MAR 2008 ISSUE 39 · 32 Can Abis optimization really pay off? By Chen Ni The rapid development of mobile services has increased pressure on mobile backhaul bandwidth, especially in

MA

R 2008 ISSU

E 39

MAR 2008 ISSUE 39

It’s IPTime !

IP relieves backhaul pain

Mobile backhaul landscape

Technology choices for mobile backhaul

－Vodafone’s splendid transform on transport networks

Seize today for tomorrow

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Editor-in -Chief: Gao Xianrui ([email protected])

Editors: Liu Zhonglin, Pan Tao, Xu Peng, Xue Hua

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Contributors:

Gao Ji, Cai Jueting, Du Wei, Li Hongsong

Liu Xiheng, Ma Hongzhong, Zhu Nianguo

Xi Zixue, Peng Bo, Jiang Shumiao, Zhang Bing

Liu Danting, Zhao Changcheng, Liu Haosheng

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People strongly felt the global trend towards mobile broadband at the Mobile World Congress 2008 held earlier this year in Barcelona, Spain. Evolving from 2G to 3G, HSPA, and LTE at an unprecedented speed, new mobile communication technologies are becoming widely available all over the world. With a rich variety of mobile applications and a wide range of mobile terminals, mobile communications have a far-reaching impact on society, and are now an integral part of people’s daily lives.

Currently, ALL IP is the development trend of mobile networks and mobile broadband has become the focus in the industry. Mobile content, basic networks, terminals and the like are gradually maturing. Yet, operators are facing a variety of challenges, one of which is from the transport network supporting the development of mobile services.

The rapid development of mobile broadband services has brought explosive growth of bandwidth requirements, which forces operators to continuously expand their networks. The growth of bandwidth has not brought positive linear growth in their revenues; on the contrary, the revenue per bandwidth unit has a tendency to drop.

Traditional TDM-based transport networks feature low bandwidth utilization rates, and the rising need for bandwidth has put operators under great pressure in regard to transport costs. Consequently, the traditional transport network no longer suits the development of today’s mobile broadband services. IP technology with features such as statistical multiplexing and bandwidth compression can help operators to greatly improve transport efficiency. Introducing IP technology into transport networks is the only viable solution in the era of mobile broadband.

Traditional IP technologies, however, have disadvantages in reliability, manageability, network synchronization. To realize carrier-class service transport, it’s necessary to optimize the traditional IP technology into transport technology. Traditional TDM-based transport networks have managed to provide carrier-class assurance for mobile service transport by using connection-based SDH technology. After IP technologies are introduced in transport networks, operators have to consider how to realize carrier-class IP transport networks.

We have invited some industry experts to explore IP transport networks, and share their experiences and opinions to keep you informed of the latest solutions and developments. A discussion of various methods for the successful transformation of transport networks towards ALL IP is also on the agenda. As a global leader in mobile broadband and transport networks, Huawei has successfully launched the IP Transport Infrastructure for Mobile Evolution (IPTime). The era of IP transport networks has finally arrived! It’s IPTime! Together, we will lead mobile transport to ALL IP.

Taking mobile transport to ALL IP

Tang Xinbing

Vice President of Huawei Network Product Line

Cover Story

09 Seize today for tomorrowVodafone’s splendid transform on transport networks

As mobile broadband networking gains popularity, traditional TDM-based transport networks are no longer keeping pace with Vodafone’s rapid development, and ALL IP transformation of transport networks ranks high on its agenda.

By Zhou Yuchun

What’s inside:

P.09 P.32

Expert’s Forum

05 Mobile backhaul landscapeBy John Lively

02 Google to put down trans-Pacific cable

03 Huawei unveils comprehensive IP Transport

Infrastructure for Mobile Evolution at

MWC 2008

Global Digest

01 Vodafone uses HSPA+ to head the mobile

broadband race

26 Achiving a carrier-class packet transport network

By Cui Jiang

23 Transport mode evolution in the mobile broadband era

By Li Hongsong & Chen Zhidan

How to Operate

29 Networking microwave communication

By Liu Haosheng

Main Topic

19 It’s IPTime!By Li Hongsong

Booming mobile broadband services and rapidly evolving mobile network technologies have pushed mobile networks into an ALL IP era.


P.29 P.40P.43

41 Fixed broadband access boosts mobile broadbandization

By Zhang Yufen & Wang Peng

43 Evolving mobile transport NMSBy Wang Shaosen

50 To build IP-based broadband mobile networks, you needThe packet microwave solution

By Cui Jiang

Media Insight

35 IP relieves backhaul painBy Anthony Plewes

Let’s COMMUNICATE beyond technology and share understandings of the latest industry trends,

successful operational cases, leading technologies and more. Based on in-depth analysis of the

matters that lie close to your heart, we will help you stay on top in the competitive telecom industry.

32 Can Abis optimization really pay off?

By Chen Ni

The rapid development of mobile services has increased pressure on mobile backhaul bandwidth, especially in terms of 3G service provision. Abis optimization can to some extent ameliorate this situation by enhancing transport efficiency, but how great is the value generated?

Solution

37 IPTime for allMulti-scenario applications challenge mobile transport networks

By He Chaohua

Mobile operators need different transport solutions when building mobile transport networks and need the right solutions for different stages of development, challenges and requirements.

Leading Edge

46 Technology choices for mobile backhaul

By Pu Yun

You can choose from various packet transport network technologies, including PBB-TE, IP/MPLS, and T-MPLS. Which one is the most effective for mobile backhaul?

GLOBAL DIGEST

MAR 2008 . ISSUE 391

News

China Mobile joins Verizon, Vodafone, in LTE tests

China Mobile has confirmed

plans to trial next generation wireless

technology LTE (Long Term Evolution),

in a three way partnership with

Vodafone and Verizon Wireless.

At the Mobile World Congress in

Barcelona, the Chinese carrier said that

the trials would encompass LTE FDD

(Frequency Division Duplex) as well as

TD-LTE (Time Division Duplex version

of LTE), as an evolution of China's

home grown TD-SCDMA technology.

China Mobile is expected to be

required to deploy TD-SCDMA when

3G licenses are finally awarded in the

country, an event many expect to

happen prior to the Beijing Olympics

which kick off in the summer.

Verizon's interest in LTE has been

recognised as something of a coup

for the GSM-community, seeing as

Verizon's existing network uses rival

CDMA2000 technology. However,

Vodafone has financial interests in

both Verizon Wireless and China

Mobile.

Sprint, T-Mobile advocate white space for backhaul

Sprint and T-Mobile have told

the Federa l Communicat ions

Commission that they support the

idea of opening up white space

spectrum - the unlicensed spectrum

that sits between airwaves currently

licensed to TV broadcasters.

While Google, Microsoft and

others have been lobbying the FCC

to open up white space spectrum for

unlicensed super Wi-Fi devices, Sprint

and T-Mobile are advocating that

white space spectrum be granted

on a fixed-license basis for wireless

backhaul services.

"Because backhaul comprises a

significant cost for wireless carriers,

and incumbent local exchange

carriers' special-access charges

are exorbitant, Sprint Nextel and

T-Mobile must find more affordable

alternatives to the ILECs' special-

access offerings," the operators

told the FCC.

Orange launches high speed mobile service

Orange France is rolling out a

new high speed HSDPA service for

corporate customers, beginning in

Lyon. The new service will deliver

up to 7.2Mb/s download data

speeds. Deployment in other major

cities and towns across France

should be underway by the summer

of 2008. Dubbed 3G + HSDPA, the

new service will also offer upload

data speeds of up to 1.4Mb/s.

Orange is the only operator in

France offering three types of

mobile phones compatible with 3G

+ HSDPA that can be adapted to

laptop computers.

Vodafone uses HSPA+ to head the mobile broadband race

Vodafone is to trial HSPA+, an

evolution of today’s radio access

HSPA technology, to assess its

potential to deliver even higher

data rates through the upgrade of

existing network equipment.

Vodafone will work alongside

Huawei, Qualcomm and Ericsson to

trial Release 7 HSPA+ (also known

as HSPA Evolution) which has the

potential to handle data even

more efficiently than today’s HSPA

technology.

The initiative will help to establish

whether HSPA+ is capable of

delivering data throughput rates of

up to 28.8Mbps compared to the

14.4Mbps maximum offered by

today’s HSPA networks. If successful,

the technology has the potential

to extend the life of today’s HSPA

infrastructure still further.

The project builds on early

technical assessments that Vodafone

has already carried out where the

MIMO version of HSPA+ recorded

high data throughput rates for users

in a simulated urban macrocellular

network.

Last year Vodafone launched a

3G broadband service based on High

Speed Packet Access (HSPA) with

downlink peak rates of up to 7.2Mbps

in selected hotspots within some key

markets. Vodafone plans to carry out

software upgrades to more of these

selected hotspots to deliver up to

14.4Mbps from the end of the year

as part of the existing HSPA roadmap

subject to device availability.

AT&T to invest USD1 billion in network

AT&T announced that it has

budgeted USD1 billion this year to

upgrade its international network.

The company said that amounts to

double what it spent in 2006 and

more than 30% higher than 2007’s

network investment. The USD1 billion

will go toward expanding the carrier’s

global network reach and capacity,

and to upgrading networks to handle

new technologies, including demand

for Internet protocol services, such as

voice transmissions.

AT&T said its network upgrade

plans include: new sub-sea fiber-

optic cable capacity to Japan

and Asia; new core MPLS routers

in Europe, Asia and the United

States; new network-to-network

connect ions to extend reach

into high growth markets in Asia

Pacific, Eastern Europe and South

America; increasing data center

hosting capacity; integrating and

developing unified communications

capabilities from its recent acquisition

of Interwise; and offering global IP-

based audio-conferencing services.

The carrier said these network

investments will help it continue to

capitalize on the ongoing shift in

network traffic from voice to data,

and IP-based data as customers

migrate from legacy packet networks

to MPLS-based VPNs and managed

applications. AT&T customers can

currently make calls on six continents

and in more than 200 countries, and

access wireless data roaming in more

than 145 countries.

MAR 2008 . ISSUE 39 2

Data

211 Seven out of every eight 3G/

WCDMA operators have launched

HSDPA services according to the

latest figures from the Global

mobile Suppliers Association (GSA).

A total of 211 WCDMA operators

have launched commercial services

in 91 countries, of which 185

operators (87.6 percent) have

a lso launched HSDPA - High

Speed Downlink Packet Access.

HSDPA mobile broadband services

are now commercially available

in 80 countries. There are 103

commercial HSDPA operators in

Europe, 36 in APAC, 24 in the

Middle East and Africa region, and

22 in the Americas.

154%According to a recent report

from ComScore, U.S. Internet usage

via mobile broadband increased

154 percent during 2007. The

study looked at data collected from

computers that accessed the Internet

via mobile broadband service

providers. Verizon Wireless and

Sprint Nextel took the lionshare of

the mobile broadband market, while

AT&T recently announced plans

to increase its coverage. The study

found that 59 percent of the traffic

came from work computers while 41

percent came from personal home

computers.

375 millionResearch and Markets announced

the addition of 4Q07 Global 3G/4G

Deployments & Subscribers Tracker

to their offering. 4Q07 was a strong

quarter for HSPA deployments, with

8 HSDPA and 9 HSUPA deployments.

More than half of the HSUPA

deployments for the quarter were

in Western Europe, which is no

surprise, given that Western Europe

is a hotbed for WCDMA/HSDPA, and

Western European operators are now

embracing HSUPA to add throughput

on the uplink. There were 6 Mobile

WiMAX deployments, with half of

these occurring in the Latin & South

America geographic segment.

3G/4G subscribers (i.e., those

subscribers to WCDMA/HSPA, EV-

DO, TD-SCDMA, WiMAX, and LTE

networks) grew 91% over the course

of 2007, and a 63% growth rate over

the course of 2008 was expected,

with subscribers expected to rise from

230 million in 2007, to 375 million in

2008.

1 trillionA new report f rom Port io

Research confidently predicts that

the worldwide mobile industry will

be worth USD1 trillion by the close

of 2008.

There are numerous highlights in

the report, which will prove happy

reading for even the most challenged

Mobile Network Operators and the

thousands of companies that support

this still fast growing industry.

Perhaps one of the most re-assuring

trends is the continued growth in

the number of mobile subscribers

worldwide from 3.1 billion at the

end of 2007 to an estimated 5 billion

by 2012. All non-voice Value Added

Services (VAS) continue to grow with

forecasts showing the worldwide

market for non-voice services to be

worth a quarter of a trillion USD by

2012.

China Telecom plans mobile network rollout in 21 provinces

China's largest fixed telecom

service operator China Telecom

is accelerating Wi-Fi deployment

and plans to launch a new round

of bidding for procuring mobile

network equipment in 21 provinces,

Shanghai Securities News reported.

The large-scale deployment

indicates the business focus of China

Telecom is moving to the mobile

network sector, which further

indicates the company may abandon

PHS service in 2009, said an industry

insider.

Reports said China Telecom will

take over the CDMA network of

China Unicom in China's telecom

industry reshuffle. After that, it will

transfer its PHS users into CDMA

users smoothly through marketing

tactics, the insider predicted.

T h e s o u r c e a d d e d t h a t

deployment of mobile network

will lift the customer loyalty for

China Telecom, which will sharpen

the competitive edge of its mobile

service.

Google to put down trans-Pacific cable

Web giant Google is heading

up a consortium of six international

companies, which th is week

forged an agreement to lay a high-

bandwidth subsea fibre optic cable

linking the United States and Japan.

The construction of the trans-

Pacific infrastructure, called Unity, will

cost an estimated USD300 million.

The consortium is a joint effort by

Bharti Airtel, Global Transit, Google,

KDDI Corporation, Pacnet and

SingTel.

Unity is expected to address

broadband demand by providing

much needed capacity to sustain

the growth in data traffic between

Asia and the US. The new cable is

expected to initially increase trans-

Pacific lit cable capacity by about 20

percent, with the potential to add up

to 7.68Tbps of bandwidth across the

Pacific.

"The Unity cable system allows

the members of the consortium

to provide the increased capacity

needed as more applications and

services migrate online, giving users

faster and more reliable connectivity,"

said Unity spokeswoman Jayne

Stowell.

According to the TeleGeography

Global Bandwidth Report, 2007,

trans-Pacific bandwidth demand

has grown at a compounded

annual growth rate (CAGR) of 63.7

percent between 2002 and 2007.

It is expected to continue to grow

strongly from 2008 to 2013, with

total demand for capacity doubling

roughly every two years.

The 10,000km Unity link will

provide connectivity between

Chikura, located off the coast near

Tokyo, to Los Angeles and other West

Coast network points of presence.

GLOBAL DIGEST


Huawei News

Unveils comprehensive IP Transport Infrastructure for Mobile Evolution at MWC 2008

Barcelona, Spain, 12 February

2008 Huawei has unveiled the

industry's most comprehensive IP

Transport Infrastructure for Mobile

Evolution (IPTime) at the Mobile

World Congress 2008 held in

Barcelona.

Huawei's IPTime is an ALL

IP based transport solution that

creates enhanced broadband

experiences and TCO reductions in

2G/3G mobile networks for carriers.

Huawei also used the event to

showcase key components of the

IPTime Solution, including PTN

series packet transport networks

equipment as well as the SmartAX

series multi-service access modules.

Huawei's IPTime provides GPS-

grade packet clock synchronization,

SDH-like OAM and protection

capabilities, supporting world-

leading end-to-end carrier-grade

performance in packet transport

network. The architecture also

provides PWE3 (Pseudo-Wire

Emulation Edge to Edge) capability

a n d s u p p o r t s a b u n d a n t o f

interfaces, such as TDM, Ethernet,

microwave, xDSL and xPON,

helping carriers achieve smooth

evolution from 2G to 3G, HSPA or

LTE.

Huawe i ha s ga ined so l i d

technical expertise and extensive

experience in both mobile and

ALL IP broadband networking. The

company's mobile solutions have

been widely deployed in more than

100 countries around the world

and the company has recently

won 44 new UMTS contracts.

Huawei's mobile NGN/3G bearer

networking products have served

more than 700 million subscribers

and over 90 operators worldwide,

making Huawei the world's largest

provider in the area. According

to the reports published by Ovum

RHK and Gartner in the third

quarter of 2007, Huawei is the

world's fastest-growing equipment

provider in the optical network

market, ranking No. 2 in the global

optical market and No.1 in IP

DSLAM shipments.

ALL IP mobile transport solution successfully completes EANTC’s mobile backhaul interoperability tests

Berlin, Germany, 5 February 2008

Huawei has announced that its ALL

IP Mobile Transport Solution has

successfully participated in the mobile

backhaul interoperability tests set by

the European Advanced Networking

Test Center (EANTC) at EANTC's

laboratory in Berlin, Germany.

Huawei was one of fifteen

vendors to participate in the testing,

co-organized by the EANTC, an

authoritative European testing agency

with the support of the Metro

Ethernet Forum and the IP/MPLS

Forum, which certifies that next-

generation mobile backhaul solutions

using Carrier Ethernet services can

be implemented over diverse fixed

and mobile network transport

technologies including MPLS, PBB-TE

and T-MPLS.

In the testing, Huawei's ALL IP

Mobile Transport Solution, including

packet transport network equipment

and multi-service access modules,

successfully interoperated with

equipment from multiple vendors

in the three domains of MPLS, PBB-

TE and T-MPLS and demonstrated

high-precision clock synchronization

technology. The solution also

demonstrated carrier-class reliability

through supporting high-quality

mobile backhaul services.

Huawei's ALL IP Mobile Transport

Solution is part of the first public

multi-vendor Mobile Backhaul

Interoperability Demonstration on

show at the MPLS and Ethernet

World Congress in Paris, 5 - 8

February, 2008, and at Mobile World

Congress in Barcelona, 11 - 14

February, 2008.

Becomes China Netcom’s largest supplier of optical access solutions

Shenzhen, China, 7 March 2008

Huawei announced that it is to

supply nearly 40% of China Network

Communications Group's (China

Netcom's) optical access solutions,

making it the operator's largest

partner in the optical field.

As a partner of the 2008 Beijing

Olympic Games, to provide fixed-

line communication services, China

Netcom decided to centralize

the purchase of its optical access

equipment to prov ide u l t ra-

broadband services to end-users.

A dozen suppliers in the industry,

including Huawei, submitted bids.

After rigorous tests, China Netcom

offered Huawei the biggest share

of the work because of

its innovative product

design, cutt ing-edge

technologies , s tab le

equipment performance

and rich experience in

commercial applications.

Accord ing to the

contract, Huawei will

provide its world-leading

optical access equipment, the

SmartAX MA5600T series, to deliver

the best optical access experience

to China Netcom's broadband users

nationwide. The SmartAX MA5600T

series is the only system in the

industry that enables real blockless

terabit full-optical access. It satisfies

customer requirements for ultra-wide

bandwidth with a unified full-optical

access platform to access the PON

and P2P traffic, and provides more

choices for the customer to increase

their user-experience, enabling

China Netcom to provide innovative

multi-play services to its subscribers,

including voice, video and data

services.

MAR 2008 . ISSUE 39 4

Demonstrates innovative WiMAX solutions at WiMAX MEGNA Forum

Dubai, UAE, 13 March 2008 Huawei

announced during the WiMAX

MEGNA Forum that it is rolling out its

new generation WiMAX solution. The

new technology is an ALL IP solution

that can deploy WiMAX with GSM,

CDMA, UMTS, HSPA, IMS, NGN and

DSL integrated networks, and enables

operators to provide its subscribers

with advanced high-speed mobile

broadband services.

The new WiMAX station applies

the innovative technologies of highly-

efficient power amplifiers, multi-

carrier, distributed architecture and

intelligent temperature controls. By

adopting this solution, operators are

able to save energy, materials, land,

and labor, reduce carbon dioxide

emissions by over 60%, and reduce

at least 30% of the general operation

expenditure. Thus, environmental

protection and economic profits can

be achieved simultaneously.

Becomes global 4th largest patent applicanShenzhen, China, 21 February

2008 According to the World

Intellectual Property Organization

(WIPO), Huawei moved up 9 places

to become the 4th largest patent

applicant under the WIPO Patent

Cooperation Treaty (PCT), with

1,365 applications published in

2007, following Matsushita, Philips

Electronics N.V. and Siemens.

The year of 2007 saw a record

number of filings under the WIPO

PCT. In total, a record 156,100

applications were fi led in the

year, representing a 4.7% rate of

growth over the previous year.

Inventors from the Republic of

Korea (4th place) and China (7th)

consolidated their top ten position

in 2007, along with the US, Japan,

Germany, France, UK, Netherlands,

Switzerland and Sweden.

Launches world’s first 3.5G datacard with mobile TV functionality

Hannover, 4 March 2008 Huawei

launched the world's first mobile TV

capable 3.5G datacard, called the

E510, at CEBIT, the world's largest

communications showcase event

for consumer electronics, held in

Hannover, Germany.

The E510 is a small and slim

2M HSUPA stick equipped with

mobile TV functionality that can

turn a computer into a television

with direct access to a TV signal.

The device integrates mobile TV

and mobile broadband, can be

used for PCs and laptops and is

suitable for both professional and

entertainment purposes.

Huawei is widely recognized

for integrating industry-leading

technologies with fashionable,

high-quality industrial design. At

CEBIT, Huawei will showcase its

award-winning products from iF (

International Forum Design ), the

recognized Oscar in the industrial

design community, including the

V720 which features a “mirror

design”, the E960, an HSDPA

wireless gateway, and the compact

and fashionable E272. In the

second half of 2007 when "slimmer

and smaller" emerged as a new

trend for terminals, Huawei set the

pace by launching the the E170,

the world's first HSUPA USB Stick.

Huawei's terminal sales, which

include handsets, datacards, fixed

wireless terminals and gateways,

totaled 40 million units in 2007,

and USD2.5 billion in contact sales.

To date, Huawei has captured

significant market share in mobile

broadband devices, selling a total

of 8 million devices predominantly

to Europe, US and Japan.

Successfully deploys ALL IP CDMA network for Tata Indicom

Shenzhen, China, 20 Feb 2008

Huawei announced that its ALL IP

CDMA solution had been successfully

deployed in the commercial network

of Tata Indicom (TATA) in India. India

is an important strategic market in

the global telecom industry. As India's

leading CDMA operator, TATA is

building a robust, pan-India telecom

network to provide high-quality

and reliable services, and realize its

corporate vision of achieving 100

million subscribers by 2011 in India.

TATA selected Huawei's ALL IP-

based CDMA core network solution

and radio access equipment to

was tested during the 2008 New

Year festival when the call traffic

was about 2.5 times the normal in

Delhi. Huawei's robust IP mobile

soft switch, renowned for its high-

capacity reliability, ensured that

TATA met the peak traffic challenge

successfully. The high throughput of

the ALL IP PARC platform allowed the

network to cope easily with heavy

load and delivered a high quality

performance.

replace its existing network in Delhi,

Kolkata and other main cities, thus

enabling its transformation towards

3G technology. Leveraging on its rich

international experience in project

deployment, Huawei successfully

completed this project in six months.

Results from independent third party

audit reveal that the network is one

of the best available. The new end-

to-end ALL IP network architecture

allows TATA to simplify network

operations, improve resource

utilization, and significantly reduce

operating expenditure.

The quality of the network

EXPERT’S FORUM



MAR 2008 . ISSUE 39

Mobile operators are banking on broadband services for continued revenue growth. Mobile

broadband services in turn generate substantially more traffic than voice service and SMS. Since

mobile backhaul is a major component of mobile OPEX, controlling its cost is the key to turning

mobile broadband revenue into profit. Operators and wholesale backhaul providers are employing

several network strategies for doing this, using an array of copper, fiber, and microwave

technologies.

EXPERT’S FORUM

By John Lively


Huawei Technologies

MAR 2008 . ISSUE 39 6

John Lively, Vice President, Forecasting and Analysis, Ovum-RHK. He leads Ovum’s coverage and analysis of mobile backhaul, global CAPEX and vendor intelligence. John is also responsible for overseeing the production of Ovum-RHK’s market forecasts, market share analysis, and market update reports for all fixed, mobile, financial, and services subscription research.

MAR 2008 . ISSUE 39

Huawei Technologies

Introductionobile backhaul is a term very much in the forefront of the telecom equipment arena in 2007. Many articles

have been written and presentations given on it, even whole conferences have been dedicated to it. Surely, it must rank among the top ten buzz phrases in telecom equipment today. Despite all the publicity, however, what it means and what it represents in terms of opportunity are far from clear.

The term backhaul is perhaps a bit misleading, to the extent that it implies a one-way transport of traffic, from a cell tower “back to” the switching office. In reality, of course, voice and data traffic is two-way and more or less symmetrical, while newer mobile music and video services are more like the wireline Internet, with much higher traffic downstream (to the subscriber’s handset) than in the other direction.

So, exactly what is meant by the term mobile backhaul? Simply put, mobile backhaul is the transport and aggregation of mobile traffic between various cell sites and a mobile switching office.

The mobile operator’s backhaul challenge

Mobile operators in many parts of the world are facing the maturation of mobile voice services. In North America, Europe, the Middle Eastern region, and the

developed countries of Asia and CALA, mobile voice penetration is well in excess of 50 percent, and consequently, subscriber growth i s s lowing and approaching stagnation. At the same time, competition for subscribers has intensified, resulting in downward pressure on prices, leading to a slow decline in voice ARPU in many countries over the past few years. The combination of fewer subscriber additions and downward price pressure has resulted in the stagnation of mobile voice revenues.

Mobile operators have responded to voice maturation by launching new ser v ices , wi th the f i r s t be ing shor t messaging service (SMS), also called text messaging. With the advent of higher-capacity third-generation (3G) radio access technology, operators have launched additional services such as music and video downloads, streaming news, and sports information services. The GSM Association reports over 196 HSDPA-based mobile networks in operation around the globe, while the CDMA Development Group reports that 226 operators have deployed or are deploying CDMA2000 1X networks in 97 countries.

Verizon’s recent results illustrate the importance of these new services to mobile operators. For the 12-month period ending March 31, 2007, Verizon’s subscriber growth was 14 percent, voice service revenues grew only 10 percent due to declining ARPU, and data service revenue grew by a whopping 78 percent, resulting in overall services revenue growth of 18 percent. Fig. 1 shows the growing importance of data revenues to Verizon. Over the past two years, data services have

grown from 6 percent of sales in 1Q05 to 18 percent in 1Q07.

Verizon’s situation is perhaps better than that of some other operators since it is experiencing continued growth in subscribers. Even so, Fig. 1 clearly shows the important role that new services play in boosting revenue growth. Fig. 2 sheds more light on the reason that data services are important, using results from KDDI au, KDDI’s mobile communications branch: the ARPU for voice services is eroding while ARPU for data is not.

The increased revenue from data services does not come without added cost, however. The new services create additional traffic, which adds to operational costs. In fact, since the new services are broadband, they have the potential to generate substantially more traffic, as shown in Fig. 3.

Qualitatively, the impact of these new mobile broadband standards on mobile backhaul is clear: backhaul traffic will increase significantly. The exact impact depends on the modulation and encoding used to carry 3G traffic over T1/E1 links (QPSK or 16QAM, for example), but estimates of 3G backhaul traffic demand range from (4 - 8) × T1 (or E1) equivalents per cell site, compared to the 1 or 2 that are required to handle voice and SMS traffic.

In addition, the traffic related to mobile broadband services will tend to be more bursty than conventional voice and SMS traffic, requiring higher levels of peak-to-average provisioning, further escalating capacity requirements. Operators are already feeling the 3G traffic bite in some cases; T-Mobile’s traffic increased by a factor of three in just one month after it

M

EXPERT’S FORUM


Fig.2 ARPU trends for voice and data ( KDDI au service )

( Source: KDDI annual reports )

Fig.1 Verizon’s mobile revenue growth

( Source: Verizon Communications )

Data

Voice

1Q05 2Q05 3Q05 4Q05 1Q06 2Q06 3Q06 4Q06 1Q07Data 0.4 0.5 0.6 0.8 0.9 1.0 1.2 1.4 1.6Voice 6.2 6.4 6.7 6.6 6.7 7.0 7.3 7.3 7.4

10

8

6

4

2

0

USD billion

Fig.3 3G and 4G standards data rates compared to 2G

( Source: Ovum-RHK )


launched a flat-rate HSDPA service.

Major backhaul solutionsMobile operators today are using similar network strategies

to avoid falling into a broadband services profitability trap.

Overlay solution

One of the simplest means of accommodating 3G traffic in a mobile backhaul network is via an overlay network. In this architecture, the existing infrastructure for transporting and aggregating voice and 2.5G data is left in place, and a separate network is installed to carry the 3G traffic.

The overlay strategy has the advantage of requiring no change to the existing 2G infrastructure, and hence carries a low risk of network disruption and service outage due to the upgrade. It also allows more relaxed network performance for multimedia services, while maintaining higher QoS on low-traffic, high-value voice services. The downside of this approach is its cost and complexity. There are more network elements and protocols to maintain, and possibly more vendors to manage, which negates some of the cost savings associated with moving the 3G traffic off the existing TDM infrastructure.

Hybrid-channel bonding

In this solution, multiple existing T1/E1 channels are used together to create a higher-capacity transport pipe. It has the advantage of using standard transport services, while requiring only small changes in the 2G infrastructure. At the same time, it allows for lower standards for the 3G traffic. Disadvantages are added complexity (multiple vendors, network elements, and protocols) and somewhat higher cost.

Hybrid-pseudowire

Pseudowire is, in a sense, the opposite of channel bonding. While in the latter, 3G traffic is carried via legacy transport services, pseudowire allows the transport of 2G traffic over Ethernet services. In a pseudowire solution, a dedicated box (or board within a larger transport or aggregation element) encapsulates TDM and ATM traffic within Ethernet. At the other end of the link, the TDM and ATM traffic is split out and reconstituted in native form, and fed into existing legacy switching equipment.

Pseudowire’s purported advantages are that it eliminates the need for TDM cross-connects and ATM switches in the MSO, and also enables the use of a variety of Ethernet services for backhaul, including Ethernet over microwave, Ethernet over copper, Ethernet over fiber, Ethernet over DSL, Passive Optical Network (PON), etc. It also provides T1/E1 and Ethernet interfaces to all generations of equipment.

The primary disadvantage is that latency is increased by about 5 milliseconds, which can affect latency-sensitive applications such as game playing and streaming video or music.

￥1,000

￥2,000

￥3,000

￥4,000

￥5,000

￥6,000

￥0

CNY per month

Voice ARPU

Data ARPU

1Q05 2Q05 3Q05 4Q05 1Q06 2Q06 3Q06 4Q06 1Q07

Voice SMS 3G 4G

10

100

1,000

10,000

100,000

1

Kbps

4G=70 Mbps

3G=2.5 Mbps

Note: Figure shows theoretical maximum data rates. Actual user rates will be less than ideal.

Huawei Technologies

MAR 2008 . ISSUE 39 8

Integrated Ethernet

The integrated Ethernet solution is just that - the integration of 2G and 3G traffic on a single Ethernet service. The BTS connects to the BCS via IP transport only, and there are no T1/E1s in the backhaul network.

One disadvantage of pure Ethernet backhaul networks is that GSM and UMTS have c locks that need to be updated via the network. If TDM is eliminated, an alternative clocking source has to be provided. CDMA networks typically embed a GPS receiver in the base station to enable clock synchronization.

Another drawback of this solution is that best-effort QoS Ethernet is not good enough for voice service, and a more expensive Carrier Ethernet or equivalent service would have to be used. Jitter and latency matter a lot for voice services.

The conversion of an existing network to ALL IP backhaul would involve a lot of changes at one time, risking service disruptions, requiring training in new technolog ie s and methods , and necessitating the evaluation and qualification of new equipment and possibly new vendors. For this reason, ALL IP backhaul is likely to appear first in new networks being built from scratch (e.g., in developing countries). Among operators with existing networks, gradual migration to ALL IP via some intermediate solution such as hybrid or overlay is most likely.

All of these network strategies support business goals that are shared by nearly all mobile operators:

Pro tec t revenues by min imiz ing • downtime (high reliability = more billable minutes) Maximize subscriber growth via rapid • installation and provisioning of services Reduce opera t iona l expense s by • optimizing the utilization of existing transport and migrating to converged ALL IP networks over time.

Backhaul equipment opportunity

Given that the traffic carried in the mobile backhaul network can include both

Table 1 Pros and cons of various backhaul facilities (Source: Ovum-RHK)

Service Advantages Disadvantages

Ethernet over fiber High speed and scalableBTS support, SLA negotiation,limited availability of fiber to cell sites, lengthy provisioning time

Ethernet over copperHigh speed and scalable; leverages existing copper facilities

Existing copper is controlled mainly by incumbent operators.

Ethernet over microwave Fast, low-cost installationLine of sight required between antennas

DSLFor integrated operators, provides some fixed/mobile synergies

Bandwidth-distance trade-off; avail-ability

PONFor integrated operators, provides some fixed/mobile synergies

Not widely deployed

Fixed WiMAX(IEEE standard 802.16-2004)

Potentially lower operating and first cost

Immature and not field proven; spectrum an issue in many places; QoS concerns

VSAT Can be located far from the MSO Higher cost; QoS concerns

standard TDM and Ethernet transport and aggregation, the term mobile backhaul equipment covers a very broad range of products.

For purposes of describing the mobile backhaul equipment opportunity for vendors, it is useful to break this market into several categories. Some possible segmentation schemes are: Network solutions, Physical media, and Backhaul facilities. Each segmentation scheme bears some commentary.

Network solutions

Network solutions basically involve TDM, Ethernet, channel bonding, and pseudowire. Any given operator will naturally favour one or the other solution depending on the state of its services deployment, its network status, and the availability of backhaul services from third-party providers.

Physical media

Physical media are copper, f iber, microwave, satellite, and others.

Mobile backhaul transport can take place over copper wire, optical fiber, or air, and there are numerous considerations for operators to determine which one to use, including maximum capacity, maximum distance, first cost and operational cost, ease of deployment, and competitive factors.

As it turns out, different regions of the world typically use different types of

backhaul:In North America the majority is copper • or fiber, because there was little spectrum for mobile backhaul at the time the mobile networks were being built. In Europe, the majority of backhaul • is microwave, because wireline (E1) services were provided by monopoly Post Telegraph and Telephone operators (PTTs) at high cost in many countries, and wireless spectrum was available. Asia is much the same as Europe, • with microwave dominating. Many of the largest Asia mobile operators are integrated with wireline telcos, e.g., DoCoMo, KT Freetel, KDDI, China Mobile (to some extent), and Telkom Indonesia/Telkomsel. Africa has a high use of Very Small • Aperture Terminal (VSAT), particularly in more remote areas where individual cell towers are geographically isolated. Estimates are that approximately 60

percent of the world’s base stations are backhauled with mobile transport of some sort.

Backhaul facilities

As detailed in Table 1, there are various backhaul facilities including Ethernet over fiber, Ethernet over copper, DSL, PON, WiMAX, and each has its advantages and disadvantages that lead operators to choose one versus another.Editor: Zhou Huajiao [email protected]

COVER STORY

MAR 2008 . ISSUE 39

SEIZE TODAY FOR TOMORROW

During the past few years, Vodafone has been actively transforming its mobile networks to ALL IP and taking the lead in the global mobile industry. In the fiscal year of 2007, Vodafone’s revenue was 31.1 billion British pounds, an increase of 6% compared to 2006. As mobile broadband networking gains popularity, traditional TDM-based transport networks are no longer keeping pace with Vodafone’s rapid development, and ALL IP transformation of transport networks ranks high on its agenda. By Zhou Yuchun

COVER STORY



Huawei Technologies

MAR 2008 . ISSUE 39

Vodafone’s splendid transform on transport networks

SEIZE TODAY FOR TOMORROW

Huawei Technologies

MAR 2008 . ISSUE 39 10

COVER STORY

MAR 2008 . ISSUE 39

Initiating new strategy

odafone is one of the largest mobile operators in the world. It conducts business in more than 25 countries and regions on six continents, including

its approximately 3.3% share of China Mobile. Vodafone has 114 million subscribers in Europe and 127 million subscribers in Eastern Europe, Middle East, Africa, Asia-Pacific region and affiliated areas (EMAPA). 3G services are developing quickly and there are now more than 20 million subscribers, making Vodafone No.1 in major telecom markets worldwide.

In recent years, the mobile communication industry environment has dramatically changed as a result of keener competition and stricter supervision. Traditional operators are seeking a wider business scope, and new Internet operators are looking for opportunities to squeeze into the mobile

communicat ion sector. Vodafone faces s t i f f competition from T-Mobile, Orange and other mobile operators, and from fixed network operators, mobile virtual network operators (MVNOs), Internet service providers, and even terminal providers such as Apple.

To stay abreast of the pack and to become a “total communications provider”, Vodafone is implementing ALL IP and fixed-mobile convergence (FMC) in its networks. The core is a “Mobile Plus” strategy to satisfy customer requirements for diversified broadband services other than basic voice services.

Vodafone formulated a new development plan, and began internal restructuring to achieve its goals.

Five core strategic objectivesOn May 20, 2006, Vodafone released its plan

outlining five strategic objectives:Reduce costs and stimulate revenues in Europe.

Deliver strong growth in emerging markets. Innovate and deliver on customers’ total

communications needs. Actively manage the portfolio to maximize

returns. Align capital structure and shareholder re turns

policy to strategy.Revenue stimulation

and cost reduction in

V

11


Huawei Technologies

MAR 2008 . ISSUE 39

To stay abreast of the pack and to become a “total communications provider”, Vodafone is implementing ALL IP and FMC in its networks. The core is a “Mobile Plus” strategy to satisfy customer requirements for diversified broadband services other than basic voice services.

Europe was necessary for development in mature markets. The measures taken by Vodafone included: subcontracting services, reducing management costs (downsizing etc.), constructing a network support management center, integrating regional data centers, and controlling the use of voice and data services.

Vodafone expected to see strong growth in emerging markets, and added a department solely dedicated to market expansion in new regions.

The convergence of mobile, broadband and Internet services had been helping Vodafone innovatively deliver on its promise of satisfying the total communications needs and ever changing requirements for subscribers. Specific measures implemented were: the establishment of a new department dedicated to developing services for Vodafone Home and Vodafone Office (DSL), plus developing applications integrating mobile, broadband and Internet services.

Active portfolio management was to maximize returns by the disposal of assets that did not bring high returns, and investment in services with potentially high earnings. Specific measures had included the careful consideration of capital return before acquisitions, and a reduction in the number of mergers and acquisitions.

Properly aligning capital structure and shareholder returns depended on different developmental stages. In order to ensure financial balance for mature and growing services, 60% profits from each share was distributed as dividend in FY 2006, and concerted efforts had been made to regain an A2/Prime-1 credit rating.

Internal restructuring

Vodafone’s future vis ion is to build “One Vo d a f o n e” a n d a f u t u r e - o r i e n t e d “t o t a l communications” network, but its OPCOs are scattered all over the globe. Vodafone has 18 wholly owned subsidiaries and scores of affiliated companies, with differing stages of network development, and previously each one of them selected its own suppliers. As a result, procurement and management costs were very high.

Vodafone has restructured the company with the “One Vodafone” strategy. It strengthened the procurement and technology selection management to reduce costs. An established global supply chain organization is now responsible for guiding network development, selecting short listed technologies, regulating development of network technologies, controlling the number of suppliers through global bidding and reducing the cost of technology selection. The global supply chain organization also regulates Opco management and procurement, reducing global network suppliers to a Top 30, three as main partners.

For worldwide service development support, Vodafone utilized the Global Price Book to reduce equipment prices and select strategic suppliers that could form a uniform value chain for network solutions, future development strategy, high quality services and even terminals.

In 2003, Vodafone started to seriously consider Huawei, scrutinizing financial aspects, strategies, technologies, company management, process management and R&D, finally selecting Huawei as a supplier in 2005 and beginning a close cooperation with 2G/3G network deployment and terminals in Spain, Iceland, Greece, Hungary and Romania.

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COVER STORY

MAR 2008 . ISSUE 3913

Gaining an edgePromoting mobile broadband services

Vodafone was driven by the new strategy and urgently needed a key profit growth point. However, it was difficult to expand the subscriber base in developed regions like Europe as mobile penetration was high and the market was nearly saturated. The key to success was to develop high-speed, diversified and differentiated mobile broadband services for the existing subscribers.

Beginning in 2005, Vodafone’s mobile broadband services have consistently shown vigorous growth, as seen in Table 1. In 2006, Vodafone’s revenue from non-voice services jumped to 17% of the service revenue. In the non-voice services, message services were still the main source of revenue, but mobile broadband services developed at a higher rate. In FY2006, revenue from non-message mobile broadband services reached 832 million British pounds, an increase of 61% from the previous year. By March 31, 2006, the subscribers to mobile broadband services like Vodafone Live!, 3G-based broadband services and mobile data card services were 27.1 million, 7.7 million and 0.7 million respectively.

The number of subscribers to mobile broadband services will predictably continue to rise in the near future, making mobile broadband services an important strategic sector for Vodafone. Launching services such as Blackberry and Push Email has also

Item FY 2006 FY 2005 Growth Rate (%)

Revenue from mobile services 28.137 25.74 9.3

Revenue from voice services 21.493 19.888 8.1

Revenue from non-voice servicesMessage service• Data service •

3.5560.832

3.1430.516

13.161.2

Ratio of revenue from non-voice services to total service revenue 17.0% 15.5%

Total number of subscribers (million) 176 140 21.8

Vodafone live! devices (million) 27.10 17.40 55.7

3G registered devices (million) 7.70 1.40 450

Mobile data cards registered (million) 0.70 0.20 250

Table 1 Main financial and operation indexes of Vodafone in FY 2006 ( Unit: billion pounds sterling ) ( Source: Vodafone )

helped to expand original markets.

Deploying HSDPA networksVodafone implemented a “Mobile Plus” strategy

for network transformation to keep pace with the fast growth of mobile broadband services, satisfy end user requirements, and improve the access quality of services.

First, fixed-mobile substitution (FMS) was implemented, second, FMS+DSL, and third, the Total Communications Solution. Vodafone’s HSDPA networks have been rapidly deployed. Since the first HSDPA network was put into commercial use in UK in 2006, Vodafone has deployed 15 commercial HSDPA networks globally, and currently is the industry leader.

Vodafone Spain is one of the most important OPCOs of the Vodafone Group. It has 3 million 3G subscribers. To provide innovative data services, Vodafone Spain started constructing a HSDPA network in 2006.

Vodafone Spain cooperated with Huawei and used an innovative new generation green mobile network solution. The solution featured efficient power amplification, multi-carrier, distributed architecture, intelligent temperature control, and a flexible site scenario model. Considerable amounts of energy, materials, land and manpower were saved, while reducing carbon dioxide emissions by more than 60%. The solution helped Vodafone Spain to cut the general operational expenditure (OPEX) by more than 30%, garner greater profits, and help protect the environment. According to a Vodafone executive, the solution will have an enormous influence on


Huawei Technologies

MAR 2008 . ISSUE 39 14

the economy and the environment after it is applied to tens of thousands of base stations.

The completion of the Vodafone Spain HSDPA network quickly improved the quality of Vodafone Live! and other ser v ices . In Barce lona, fa shionable youngsters with a Vodafone data card for Internet access and an HSDPA mobile phone in hand, are often seen enjoying mobile broadband experiences. In Madrid, Bernabeu football fans won’t miss a single

play, thanks to Vodafone Live!.Jaime Bustil lo, CTO of Vodafone

Spain remained a bit concerned despite of a l l the good news and remarked, “Since the HSDPA network has been deployed, subscribers to 3G data services have astonishingly increased. Profit is promising, but we are worried about how to get higher transport bandwidth to support the services. The growth speed of transport bandwidth required by HSDPA base stations will double in Spain in the

Fig. 1 Considerations for technical development of Vodafone’s networks in the future ( Source: Vodafone )

Where are we?

Today: Single-Service Vertical Networks

GPRSFixed

NetworkGSM UMTS

Services

Transport, Switching & Access Networks

Tomorrow: Multi-Service Integrated Network

Media Gateway

IP Backbone Network

Conmunication Control

Content Content

Access

Access

future. With the current price of a leased line, the growth speed of OPEX will also double, but our growth speed of profits from data bandwidth is only one time. Continued development is surely a losing proposition without optimizing our transport networks.”

The bandwidth expansion caused by HSDPA, especially the maturity and commercial use of technologies such as HSPA+ and LTE, has brought great challenges to Vodafone’s transport networks.

Jaime Bustillo, CTO of Vodafone Spain remained a bit concerned despite of all the good news and remarked, the bandwidth expansion caused by HSDPA, especially the maturity and commercial use of technologies such as HSPA+ and LTE, has brought great challenges to Vodafone’s transport networks.

Where do we want to go?

COVER STORY

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Urgent demands forALL IP transport network

Vodafone clearly sees that the rapid development of mobile broadband services corresponds with an explosive increase of transport bandwidth requirements.

The traditional TDM-based SDH transport network is suitable for TDM services. Utilization of the traditional transport network bandwidth is not high, and the transport efficiency is low with a growing ratio of data services in the network. IP transformation of the transport network is urgently needed to facilitate the rapid development of mobile broadband services.

Choosing the right technology

Vodafone is quite active in various technical forums and standardization organizations in the industry. It has also been engaged for years in the evolution and verif ication of packet transport technology through dedicated research institutions. There are three factors that prompt the decision to construct its

transport network.

TDM transmission is not suitable for IP services

The l ightening fast development of HSDPA has made the bandwidth of base stations increase from 2MB to 8MB/16MB, and the percentage of data services is far greater than that of voice services, with burst bandwidth features of low payload (traffic activation rate equaling 15 - 30%). If transport is still made through E1s that are suitable for voice services, efficiency is very low, while adding new fiber resources will double the cost of leased lines.

A packet-based transport technology is needed to enable traditional TDM, ATM and Ethernet services to access the packet transport media. The technology should also be capable of statistical multiplexing to improve the transport efficiency.

Reducing data service transport cost and ensuring transport quality

There can be multiple methods for dealing with the expansion of bandwidth usage. In a mobile backhaul network, the 2G network bandwidth can be reduced through Abis optimization. Optimizing idle slots, idle channels and mute frames can reduce roughly 60% of bandwidth requirements. However, 2G bandwidth original ly occupies one E1 only, so optimization has little effect compared to the expanded HSPA bandwidth of 4 - 16 E1s.

The offload mode can also be used to distribute base stations services such as transporting voice services through microwave l inks while data services through DSL or low-cost Ethernet leased lines. This is a good temporary solution, but DSL and cheap leased lines are not readily available, offload management is complex, and higher quality transport will be required for multi-play services in the future. These factors limit application popularization.

Services can be encapsulated into packets by means of packet transport n e t w o r k ( P T N ) a n d p s e u d o - w i r e e m u l a t i o n e d g e - t o - e d g e ( P W E 3 ) technology. Transport efficiency can be much higher and transport cost much lower, thanks to the inherent statistical multiplexing features of packets.

In a mobile backhaul network, i f f iber resources are avai lable in base stations, PTN equipment can be used. If fiber resources are not available in base

Vodafone is quite active in various technical forums and standardization organizations in the industry. It has also been engaged for years in the evolution and verification of packet transport technology through dedicated research institutions. They believe that the ALL IP-based design of packet transport technologies allows end-to-end carrier-class performance for transport networks, satisfies subscriber requirements for multiple broadband services.


Huawei Technologies

MAR 2008 . ISSUE 39 16

stations, services can be transported through packet microwave and air interfaces. Adaptive modulation technology can then be used for dynamic adjustment of the bandwidth depending on the quality of the transport environment, providing real-time transport of high priority services.

PTN has carrier-class reliability and manageability and can ensure that jitter and delay during packet transport meet the requirements of real-time services. It also provides hierarchical operations, administration and maintenance (OAM) information to make sure that transport bandwidth is manageable and operable.

Protecting investment on existing network

Application of new technologies is a necessity to reduce long-term investment. Network upgrades, such as making traditional microwave equipment to provide Ethernet interfaces, and enabling NG SDH equipment to provide Ethernet and ATM convergence, are means of protecting investment. Network upgrades a l so ca ter to bandwidth distribution with TDM/ATM granules as the mainstay and Ethernet services as a supplement.

There is a great deal of microwave and PDH/SDH equipment in the existing networks of Vodafone. When a new generation packet transport network is deployed, adaptation with the existing networks must be considered. If no fiber network is available, an ML-PPP-based E1 can be used, or a chSTM-1 can be adapted into the PDH/SDH microwave links, and the new network can interconnect and interwork with the existing transport network. A universal switch can be installed to reuse the already

available SDH interface boards, or STM-N interfaces can be used for SDH network compatibility.

The ALL IP-based design of packet transport technologies al lows end-to-end carrier-class performance for Vodafone’s transport networks, satisfies subscriber requirements for multiple broadband services, and helps Vodafone actualize strategic transformation from an operator to a “total communications provider”.

Vodafone is quite active in various technical forums and standardization organizations in the industry. It has also been engaged for years in the evolution and verification of packet transport technology through dedicated research institutions. They believe that the ALL IP-based design of packet transport technologies allows end-to-end carrier-class performance for transport networks, satisfies subscriber requirements for multiple broadband services.

COVER STORY

MAR 2008 . ISSUE 39

Choosing the right construction pattern

W h e n c o n f r o n t e d w i t h t h e d a u n t i n g transformation of transport networks, Vodafone was most concerned with the difficulty of managing multiple Operation Companies (OPCOs), the complex network environment, the gray areas of technical development, and more. Methods for transformation and implementation would be a great challenge. After careful consideration, Vodafone decided to start from the transport network layers.

Vodafone was hard pressed by the shortage of fiber and copper cable resources. It would not be practical to have fibers quickly extended to base stations within a few years. The actual situations of different OPCOs were also differing, and different steps had to be taken in network transformation. A key role was to be played by the global supply chain organization.

Mainstream suppliers such as Huawei were contacted for almost two years through a dedicated research department. As a result, a plan was formulated for the development of future transport networks and Vodafone released a Transport Evolution Strategy (TES). The TES made bold introductions of new transport technologies to unify service bearing, to lower network construction

and maintenance costs, and to enhance transport efficiency. Specific measures included:

Backbone

Vodafone planned and constructed its own large IP/MPLS backbone bearer networks, and transformed the MPLS backbone bearer networks of the European OPCOs into independent and integrated MPLS bearer networks. Currently, IP backbone bearer networks have already been constructed for the main OPCOs in Europe.

Vodafone also constructed large WDM/OTN/ASON transport networks, using IP over WDM/OTN, or IP over SDH technologies to realize high bandwidth and give reliable protection to backbone bearer networks.

Huawei’s ASON (SDH-based) and WDM equipment was used in the construction of mobile backbone networks in France, Netherlands, Germany, Poland, Czech Republic, Romania, Spain, Portugal, Turkey, India, Kenya and Tanzania.

Backhaul

Vodafone has constructed new mobile backhaul networks which could satisfy requirements for radio access network (RAN) services for the upcoming five years. The existing TDM-based backhaul network is evolving to ALL IP. Developing toward FMC, a uniform backhaul network was constructed to transport mobile and broadband services over the same bearer network. After consulting with Huawei, Vodafone finally decided that the mobile backhaul network should be constructed with packet transport technology.

Huawei launched a new generation PTN solution based on extensive transport network research, which can ensure the quality of transport networks and offer good flexibility and fine scalability of IP networks. The packet-based solution is compatible with service networks and has enhanced transport features. It integrates microwave networks, provides end-to-end packet transport, integrates the PTN into the existing networks, and gradually replaces and evolves the traditional TDM/ATM transport networks into ALL IP packet networks.

For base stations lacking optical fiber resources, Vodafone reduced transport OPEX by constructing microwave networks to satisfy requirements for high bandwidth in the IP RAN. Vodafone also introduced DSL networks, developed broadband services on a large scale, and provided base station accesses. During the network construction, a great number of new generation green base stations from Huawei were used by multiple OPCOs.

17


Huawei Technologies

MAR 2008 . ISSUE 39

Link

Vodafone awarded the Outstanding Performance Award to Huawei during its second Global Supplier Conference held on May 16, 2007. The award shows Vodafone’s high regard for products and services from Huawei. Adhering to its “customer-driven” philosophy, Huawei has delivered prompt and consistent quality while assuring the excellent network per formance in l ine with Vodafone’s long-term strategy.

A key factor in Vodafone’s supply chain strategy is through supplier management, and periodic assessment is given to all suppliers to continuously enhance their delivery capabilities.

“As a s t r a t eg i c pa r tne r, we a re delighted to have been awarded the

Vodafone’s mobile transport backbone network in Romania is an example with its 3G services currently available in 23 big cities. The DWDM+ASON transport solution provided by Huawei for both 2G and 3G networks transports high bandwidth services and guarantees high reliability on a large mobile network.

The network uses ASON technology to deal with multi-point failure, completely solves the problem of frequent fiber breaks, ensures high reliability of services and provides a function of service level agreement (SLA). As a result, Vodafone’s maintenance teams have been reduced from one team per 100 km of transport distance to one team per 300 km, cutting maintenance time from 24 hours per day, 7 days a week to only 8 hours per day, 7 days a week.

The ne twork a l so use s Huawei’s patented SuperWDM technology that


18

Editor: Xue Hua [email protected]

enables the transportation of 5000km ultra-long distance without regenerators. The project provides large-capacity and ultra-long-distance transport while cutting out 9 optical amplification units to further reduce DWDM network construction and maintenance costs.

I n m o b i l e b a c k h a u l n e t w o r k s , Vodafone’s OPCOs in Spain and Italy are starting to use PTN technology.

PTN technology inherits the flexibility of IP technology, and encapsulates multiple TDM, FR, ATM and Ethernet services through PWE3 technology, ensuring support for traditional mobile-service interfaces during transformation to ALL IP. Based on centralized packet switching technology, it is capable of converging services, greatly enhancing transport efficiency while saving money. PTN is a carrier-class IP transport solution, allowing

efficient and reliable service transport while overcoming the weaknesses of IP technology in reliability, manageability and network synchronization.

A n d y J o n e s , f o r m e r h e a d o f Transmi s s ion & In te rconnec t i v i t y in Vodafone and a key person in the transformation of transport networks said, “After two years of research and verification, Vodafone is now clear about its future transport network development. It is expected that the transformation can be implemented in the middle of 2008. With good compatibility and scalability, the new network will effectively support the HSDPA services that Vodafone will launch on a large scale, and will evolve to LTE in the coming years, to achieve Vodafone’s objective of being a total communications provider.”

Vodafone has se ized the hi s tor ic opportunity brought about by mobile broadband and the ALL IP transformation of transport networks, g iving them the competitive edge over the sharp competition.

Huawei’s Outstanding Performance Award

Outs tand ing Per fo rmance Award by Vodafone. The award recognizes Huawei’s commitment to providing industry-leading products, solutions and rapid response as well as outstanding delivery,” said Mr. William Xu, President of Huawei Europe. “Huawei is focused on customer-oriented innovation to create solutions, products and services that provide long-term value for our customers to help them realize their potential.”

“ Hu a w e i r e c e i v e d t h i s a w a r d f o r c o n s i s t e n t l y s h ow i n g a d e e p understanding of our business needs,” said Detlef Schultz, Vodafone’s Global Supply Chain Management Director. “The award also recognizes Huawei’s

determination to help Vodafone achieve its strategic objectives.”

Huawei has a global frame agreement with Vodafone, delivering high quality products and services to Vodafone including network equipment and handsets.

MAIN TOPIC

MAR 2008 . ISSUE 39

It’sMAIN TOPIC

19 MAR 2008 . ISSUE 39

Booming mobile broadband services and

rapidly evolving mobile network technologies

have pushed mobile networks into an ALL IP

era. Traditional transport networks that TDM

services are struggling to keep pace with the

new trend of moving to ALL IP.

By Li Hongsong

Huawei Technologies

MAR 2008 . ISSUE 39

ALL IP trend for mobile transport

P-based mobile transport networks first appeared in backbone bearer networks. IP/MPLS (multi-protocol label switching) routers over the wave division multiplexing (WDM)

system efficiently bear mobile softswitch services. China Mobile, BT, Vodafone, and Etisalat, have all seen greater profits and consumer satisfaction after building IP backbone bearer networks.

Mobile base stations are gradually adopting ALL IP technology and the air interface rate has been increasing rapidly, for example, from 144Kbps in GPRS to 14.4Mbps in HSPA, and to 100Mbps in Long-Term Evolution (LTE). As a result, transport bandwidth required by mobile backhaul networks has been booming. The forecast for 2010 is that the growth of data services will quadruple the demands on mobile backhaul bandwidth. In this scenario, an IP-based mobile backhaul is inevitable for future mobile transport networks.

Desired featuresTo improve transport efficiency and reduce

transport costs, an IP mobile transport network has to satisfy the following requirements.

ALL IP architecture: Packet requirements of transport networks can be mostly attributed to the rapid growth of data services that have uncertain and unexpected traffic. The transport network should be designed and deployed on the basis of a pure IP-based kernel to guarantee the highest level of efficiency.

Multi-service transport capability: Recent developments have shown that a unified transport network must adapt to various mobile network t e c h n o l o g i e s , i n c l u d i n g G S M , WC D M A , CDMA2000, WiMAX, HSPA+ and LTE. The transport network should be able to transport services of multi-mode radio access networks (RANs) in a unified way.

Traditional 2G networks are based on time division multiplexing (TDM); 3G R99/R4 network adopts the asynchronous transfer mode (ATM) protocol; 3G/WiMAX/LTE networks evolve into ALL IP. During the evolution of mobile networks, services based on TDM, ATM and packet will co-exist in the same network for a long time.

The transport network should be able to support unified transport of multiple services, including TDM, ATM and Ethernet services. This can be realized with the pseudo-wire emulation edge-to-

edge (PWE3) technology. Multi-scenario access and networking capability:

As different access resources are allocated to different base stations, no single access technology can cater to all requirements. Base stations in Asia-Pacific like China have relatively rich optical fiber access resources. In Europe, the microwave access mode is mostly adopted, plus there are some leased lines and small quantity of twisted pair cables.

When a mobile network is extended from wide coverage to indoor microcells and hotspot access points (APs), the transport network must provide customized multi-scenario access and networking capabilities. The network has to support multiple combined access technologies involving optical fibers, microwave and copper cables.

Precise IP clock transfer capability: Clock synchronization is a key demand for mobile networks. Traditional transport networks transfer clocks through SDH and the global positioning system (GPS). ALL IP transport networks need precise clock synchronization capabilities to handle mobile service roaming and handover.

High reliability: 3G services include data and voice services, which place different requirements on network reliability. Transport networks must offer carrier-class protection on services. By using the QoS strategy and the network protection mechanism, transport networks can offer differentiated services to reliably handle voice, video and data services.

Excellent scalability: As data services develop quickly, mobile data services and mobile traffic will boom. Transport networks should have fine flexibility and scalability regarding interface types, transport bandwidth, and network scale.

End-to-end management capability: The provision of mobile 3G services and wide network coverage will drive transport network evolution into multi-service bearer networks. End-to-end management capability can efficiently decrease network operations and maintenance costs.

Huawei sets IPTimeAt the Mobile World Congress (3GSM) Barcelona

2008, Huawei formally released the IP Transport Infrastructure for Mobile Evolution (IPTime), an ALL IP-based carrier-class IP transport network solution.

A media report commented that Huawei’s new solution embodied the development of transport networks into the ALL IP era, as mobile networks have been evolving to ALL IP. The IPTime solution has the following features:

Multi-service transport and multi-scenario

I

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It’s IPTime!

21

access. The IPTime solution is based on the ALL IP architecture and helps operators in constructing ALL IP networks, which are future-oriented strategic investments.

Based on the PWE3 technology, IPTime is able to transport various types of services and provide interface diversity such as TDM, Ethernet, xDSL (digital subscriber line), xPON (passive optical network) and microwave. IPTime helps operators to smoothly evolve from 2G networks to 3G networks, then to 4G networks. It supports access-layer transmission media like optical fiber, microwave and copper cable, as well as access requirements in various complicated scenarios. It also supports flexible transport in case of deep coverage by mobile networks.

Unique IP clock transport with GPS-like precision. IPTime offers IP clock transport schemes for ALL IP mobile networks. It adopts packet over SDH (POS) interface timing, synchronous Ethernet and IEEE 1588v2 to meet the synchronization requirements of GSM, WCDMA, WiMAX, CDMA, and future 4G networks.

High reliability and strong manageability. IPTime enables transport networks to offer end-to-end, differentiated QoS, operations, administration and maintenance (OAM) capabilities to meet different needs from base station access to the core convergence point. It supports complicated networking like star, link, ring and mesh, and enables carrier-class protection switching in the whole network within 50ms. It also supports unified network management to simplify network operation and maintenance for a significant improvement in the operator’s core competitiveness.

Smooth evolution of exist ing transport networks. IPTime adopts SDH-like management

and maintenance mechanism, offers ports that are compatible with existing transport network, and supports smooth evolution of existing networks to ALL IP transport networks.

Adding real benefitsHuawei’s IPTime ALL IP transport network solution

embraces the idea of “proper management now will guarantee a bright future”, which enables operators win big in the transformation towards ALL IP.

Simplified architecture

In a backbone bearer network, IPTime adopts the IP over OTN/WDM scheme, and decreases network costs by 30 percent. It introduces the reconfigurable optical add-drop multiplexer (ROADM) technology to the traditional WDM system and changes the point-to-point WDM system into a network that can enable cross-connect dispatching of wavelength. In addition, the IPTime enables intelligent dispatching of various service granules by introducing OTN. The backbone bearer network can provide complete OAM functions and fault location. Routers and the OTN/WDM layer adopt unified general multi-protocol label switching (GMPLS) control plane to enable interactions between the IP layer and the optical layer.

In mobile backhaul, the IPTime solution makes use of the PWE3 technology to allow IP transport of TDM, ATM and Ethernet traffic. The unified transport network leads to simpler network architecture, more convenient maintenance, and lower costs.

The IPTime solution implements end-to-end unified network management from the mobile

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backhaul to the backbone bearer network. The ALL IP transpor t network can offer higher transport efficiency, more convenient operations and maintenance, and faster deployment of new services.

Enhanced reliabilityThe backbone bearer network provides

end-to-end protection on the IP layer through various protection technologies, including MPLS traffic engineering (MPLS TE), MPLS OAM, virtual private network fast reroute (VPN FRR), and virtual router redundancy protocol (VRRP). In the optical layer, the OTN/ROADM technology enables protection on WDM subnets and cross-connect dispatching of services throughout the entire network. The advanced technologies guarantee carrier-class protection switching within 50ms in all network layers and meet the requirements of mobile IP networks. They also improve the reliability of the IP-based transport network to 99.999%.

China Mobile’s carrier-class backbone bearer network was built by Huawei and is one of the largest mobile backbone bearer networks in the world. The network has successfully handled hundreds of exponential rises in traffic volume over the past three years. Other mobile backbone bearer networks constructed by Huawei such as Vodafone and Etisalat, have also been running smoothly for over two years, proving that the IPTime transport network solution can fully meet the requirements of mobile backbone bearer networks.

In mobile backhaul, Huawei provides a complete series of carrier-class packet transport network (PTN) platforms based on ALL IP kernels. Offering carrier-class transport performance and diversified interfaces, these platforms support unified transport of traditional 2G services, 3G services, and future 4G mobile broadband services. They also support provider

backbone transport (PBT), transport MPLS (TMPLS), and layer-2 (L2) MPLS technologies. The platforms support the clock synchronization in various modes of mobile networks by using high-precision packet clock transport technologies l ike adapt ive c lock recover y, c lock synchronization over Ethernet, and clock over IP based on IEEE 1588v2. The two-layer, multi-mode carrier-class transport platform can transport comprehensive services in a highly efficient and reliable way and support mobile networks in ALL IP evolution.

Smooth network evolutionAccess resources can be obtained by

different types of base stations in mobile backhaul. Huawei’s IPTime solution offers various access modes. The solution adopts SDH-like management and maintenance as well as NG-SDH-compatible ports. These measures ensure minimal impact on the existing transport network during the network’s evolution to PTN. The existing management and maintenance mode can be inherited, and existing service interface boards can be reused.

Optical fiber-based mobile backhaul: The IPTime solution provides various optical fiber access modes, including MAN Ethernet and PON. The MAN Ethernet based on optical fibers is a multi-mode PTN transport platform with an IP kernel and provides the transport network with fine OAM and protection functions.

The transport network can significantly lower network evolution costs by inheriting the OAM features of a traditional SDH system and by reusing the interface boards of traditional SDH networks. The PON effectively improves the utilization of optical fiber resources. The WDM-PON, which integrates WDM and PON technologies, can provide bigger transport capacity and better networking capabilities.

Microwave-based mobile backhaul: IPTime provides pure packet microwave and integrates with the PTN for smooth mobile network evolution.

Microwave transport is also moving toward ALL IP as base stations develop towards ALL IP, due to the increase of bandwidth demands. There are three scenarios:

First, if base stations are partially IP-based, microwave equipment supporting both IP access and E1 access should be adopted for combined transport.

Second, if interfaces of base stations are mainly inverse multiplexing over ATM (IMA) E1, the microwave equipment supporting large-capacity E1 interfaces can be adopted. PTN equipment can be used at convergence points to enable service convergence and packet transport.

Third, if base stations are ALL IP-based, the packet microwave equipment supporting self-adaptive modulation and coding of air interfaces can be adopted for packet transport. Packet microwave equipment can be integrated with the PTN to decrease operation and maintenance costs of the transport network, and Huawei is fully able to realize microwave transport networking.

Copper cable-based mobile backhaul: Huawei’s IPTime solution provides rich xDSL access modes. At present, base stations mainly adopt the single-pair high-speed DSL (SHDSL) leased lines for service access. As the demands for mobile bandwidth increase, the offload mode can be used to separate voice and data services in base stations. Voice and signaling services requir ing high QoS can be transported through high-quality E1 lines, and Abis/lub compression technology can be used to save leased lines. Data services can then be transported through leased xDSLs.

Huawei’s IPTime ALL IP transport network solution embraces the idea of “proper management now will guarantee a bright future”, which enables operators win big in the transformation towards ALL IP.

Editor: Liu Zhonglin [email protected]

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in the mobile broadband era

Mobile broadband triggers transport network transformation

obile TV, mobile video ads, mobile search… In the past decades, the potentiality of these functions never

occurred even to the grandees who could afford a cell phone. They would

neither have imagined that a cellphone

could be so light and smart, nor could they picture themselves enjoying a range of amazing functions other than making phone calls on the move. Today, not only are mobile phones commonplace, but users are increasingly familiar with web surfing, cyber payments and online gaming through cell phones. On a global scale, mobile operators are striving to popularize mobile broadband services, the ARPU contributions from which are steadily rising. In Europe, for instance, the income derived from broadband mobile services forms over 20% of total revenue, while it exceeds 30% in Japan and Korea.

The future mobile communications market wi l l p r o v i d e

t r a d i t i o n a l voice

services as a basic communication tool subsumed within the expectation that integrated, convergent, and broadband s e r v i c e s w i l l emerge a s dominant . Moreover, one of the evolutionary goals for mobile networks is convergence with the Internet. No doubt, the rapid development of mobile broadband services will impose new demands on base stations’ air interface and backhaul technologies, which will then trigger transport network transformation.

IP and compatibility are the key factors

T h e d e v e l o p m e n t o f m o b i l e c o m m u n i c a t i o n s t e c h n o l o g i e s i s represented by high-speed packet access

(HSPA), WiMAX, and Long-Term Evolution (LTE) systems.

In HSPA mobile s y s t e m ,

By Li Hongsong & Chen Zhidan

M

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Transport mode

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for example, a WCDMA network can evolve into HSDPA, HSxPA, eHSPA, or LTE, and the air interface bandwidth will be expanded from 384Kb/s respectively to 14.4Mb/s downlink + 5.76Mb/s uplink, 25Mb/s downlink + 12.5Mb/s uplink, or 100Mb/s downlink + 50Mb/s uplink.

The major requirement for mobile backhaul is supporting cost effective, high-bandwidth transport via different t anspor t modes . High bandwidth necessitates that mobile backhaul evolves towards broadband transport to meet explosively increasing bandwidth needs stimulated by the rapid emergence and growth of mobile broadband services. IP technology forms the best method of achieving an effective and low cost system. When applied to IP technology, statistical multiplexing and bandwidth compre s s ion y i e ld h igh t r anspor t efficiency at a low cost. Additional carrier-class features are also required by IP-based mobile backhaul including high reliability, effective manageability and precise clock transfer mechanisms.

It is well-known that a backhaul n e t w o r k m a y c o n s i s t o f

multiple transport modes such

as

evolution and thus minimize the impact on current services and investment.

Smooth evolution of various transport modes

The evolution of mobile backhaul involves three stages in line with mobile broadband development: start-up, growth, and maturity. In the start-up stage very few broadband base stations are deployed and few FE interfaces emerge in mobile networks. Therefore, the bandwidth pressure placed on mobile backhaul is relatively low. The growth stage sees an increase in the number of broadband base stations, which brings constantly growing bandwidth needs. The most significant feature of this stage is the coexistence of broadband and narrowband base stations. The maturity stage involves replacing or upgrading most narrowband base stations, and basically all new base stations are built broadband in nature.

Optical fiber-based backhaul evolution

In an era of narrowband base stations, operators who build their own transport networks have already constructed large-scale optical transport networks as represented by NG-SDH/MSTP. Backhaul network bandwidth is sufficient to support future base station capacity expansion. The operators can meet bandwidth requirements by upgrading NG-SDH/MSTP equipment, replacing 155Mb/s SDH rings with 622Mb/s SDH rings, or by dividing a 155Mb/s ring into two 155Mb/s rings. For operators who employ leased lines, it is recommended that they construct their own fiber or microwave transport networks in order to cut down exorbitant leased line expenditure.

During the growth stage, a large number of broadband base stations are deployed. In order to improve mobile service transport efficiency and support transport networks’ future developement, it is necessary to construct Packet Transport Networks (PTNs). PTN equipment is based on a packet switch core in order to enhance packet swi t ch ing e f f i c i ency and ne twork

24MAR 2008 . ISSUE 39

optical fiber, microwave, and copper cables. For example, relatively rich optical access resources dictate that fiber transport supplemented with a few microwave devices is mostly adopted in China. In most areas of North America, the lack of microwave spectrum resources has been the catalyst for copper cable or fiber transport to become the pervasive mode. Meanwhile, networks in the majority of European countries are microwave-based, since the E1 rental cost is extremely high due to a monopolistic provision structure, while microwave spectrums are widely available. In this respect the situation in the rest of Asia is similar to Europe. In Africa, VSAT is widely deployed, especially in remote areas where a single BTS may be geographically isolated.

In the past when technologies needed to respond mostly to voice services, fibers, microwave, and copper cables perfectly satisfied mobile voice service requriments. Now, in the mobile broadband era, va r i ou s t r an spor t mode s mus t be developed to react to the increase in mobile broadband services.

Tr a n s p o r t m o d e e vo l u t i o n h a s highlighted the issue of compatibility, wi th t rad i t iona l s e r v ice prov i s ion de s c r ib ing a ba s i c cons ide ra t ion .

Compatibility in terms of network features and OM are also

required to realize smooth

evolution

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flexibility. PWE3 technology is deployed to support traditional service transport including E1, IMA E1, and ATM. MPLS and IP technologies are applied to PTN equipment, and their OAM features can be used to generate SDH-like 1+1/1:1 pro tec t ion , ne twork management , performance statistics, and fault location. To meet base station clock synchronization requ i rement s , e i the r s ynchronous Ethernet clock technology or packet clock transport technology can be adopted in PTN equipment to transport the synchronization clock. The interface cards in PTN equipment must be compatible with those that previously existed in NG-SDH/MSTP networks so as to reduce CAPEX, and the network management system must be inherited to reduce OPEX. Since many NG-SDH/MSTP networks are still in service during the growth stage, the PTN must be able to combine with the NG-SDH/MSTP to form an integrated network, and thus achieve the smooth evolution of fiber-based backhaul networks.

In the maturity stage, a large number of NG-SDH/MSTP devices will be replaced by PTN. For areas where base stations are densely distributed, a significant quantity of PON devices can be employed to improve fiber resource utilization. PON technology can greatly improve transport network flexibility and provide a superior network topology to support the transport of mobile broadband services.

Microwave-based backhaul evolution

In the start-up stage, existing microwave devices in the backhaul network can be upgraded to meet the banwidth requirements in a part of broadband base stations. If the corresponding interfaces are IMA E1, then large-capacity E1 modules can be added to the microwave devices to expand bandwidth. If they are FE, then FE interface cards can be added to the microwave devices to implement hybrid transport of FE and E1. The existing microwave devices located at the convergence point adopt simple L2 convergence to improve bandwidth utilization. The internal multiple add

drop multiplexer (MADM) or switching dispatch capability can convert microwave transmission links to networks in order to achieve carrier-class protection switching.

In the growth stage, a large number of broadband base stations are deployed and, accordingly, the services transported by microwave devices are mainly IP. Therefore packet microwave devices are recommended to meet base s tat ions’ cons iderable bandwidth demands and to more fully increase network bandwidth efficiency with the higher flexibility inherited from transport networks. The packet microwave device utilizes a packet switching core, wh i ch c an g rea t l y improve packe t switching efficiency. PWE3 technology can comprehensively support E1 traffic access, while MPLS and IP technologies are able to implement bandwidth statistical multiplexing, so as to produce the desired flexibility in terms of broadband service provision.

The packet microwave device supports self-adaptive modulation and coding with which transport capacity on a sunny day is able to mirror that of GE, and, on a cloudy day, can reach 100Mb/s. This greatly increases bandwidth capacity, while reducing investment since packet microwave devices are compatible with the existing microwave devices’ microwave modules. The coexistence of broadband and narrowband base stations in the growth stage inevitably leads to the coexistence of existing microwave and packet microwave devices, and compatibility between the two is essential to ensure smooth evolution.

In the maturity stage most base stations are broadband and consequently almost all the microwave devices are packet

In the mobile broadband era, various transport

modes must be developed to react to the increase in mobile broadband services.

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Transport mode evolution in the mobile broadband era

Editor: Xu Ping [email protected]

microwave. Moreover, packet microwave and packet optical transport devices are integrated to lower mobile backhaul network OPEX.

Copper cable-based backhaul evolution

During the start-up stage, bandwidth needs related to copper cable transport networks are fairly low and operators who own or rent cable resources can use G.SDHSL technology to support E1/FE traffic access from base stations. If the traffic loads on a single copper cable of a base station exceed 2Mb/s, G.SDHSL wire bonding technology can achieve a transport capacity of 5.6Mb/s.

When the number of broadband base stations increases, the offload mode is able to separate voice and data services. High QoS voice and signaling services can be transported through good quality leased E1 lines, and Abis/Iub compression technology facilitates a reduction in the number of released lines, while data services can be transported through xDSL. Given the advantage of low cost xDSL copper cable resources, the offload mode can effectively reduce leased line costs by 15% - 40%. The offload devices support traditional E1 traffic transport through PWE3, and improve the flexibility of copper cable-based transport networks by utilizing MPLS and IP technologies.

To enhance transport capacity in the maturity stage, either a large number of xDSL copper cable networks must be upgraded to VDSL2 networks, or VDSL2 network copper loops are shortened. In addition, some copper cable networks can be replaced by PON to reduce transport network costs.

Mobile broadband is an irreversible trend. With the deployment of mobile b roadband sy s t ems such a s HSPA, WiMAX, and LTE, mobile operators can achieve smooth evolution in terms of optical, microwave, and copper cable transport in backhaul networks. After all, the dream of mobile TV, video ads, search engines, and phone communities via cell phones has come to fruition. In this mobile broadband era, have we sufficiently geared up our transport networks?

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Achieving a

carrier-class packet transport network

The unprecedented growth of IP-based transport networks has renewed the evaluation of its position in the carrier-class context. Specifically, what constitutes a carrier-class packet transport network and how can such a network be realized?

ince communication networks began heading towards ALL IP, a greater variety of services have emerged in tandem with increased

service traffic. As predicted by numerous consultants, bandwidth requirements in 2008 will exceed those of 2005 by up to 7 times. Operators’ transport costs have been greatly impacted by such a massive surge in demand, and traditional TDM-based transport networks have failed to keep pace with this increase due to their comparatively low transport efficiency. Thus, transformation to IP-based packet transport network (PTN) has garnered industry-wide attention as the most expedient remedy.

Some mainstream operators are also highly concerned and actively promoting PTN’s commercial application. Vodafone, By Cui Jiang

fo r example , r ema in s p roac t i ve in various PTN technology forums and standardization organizations, and has established a specialized research institute devoted to the evaluation and verification of packet transport technology. From 2005 onwards, Vodafone has systematically liaised with equipment vendors to progress its plans for mobile backhaul construction based on PTN technology.

P T N i s g e n e r a l l y r e g a rd e d a s a connection-oriented transport network technology. Based on IP technology, it is applicable to a multi-service environment and capable of accessing, converging and transporting “TDM/ATM over Packet” and “packet-only” services. Furthermore, the low cost and high efficiency of IP networks promotes PTN as a solution that resolves these two fundamental parameters

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S

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Wireless Standard Clock Frequency Precision Clock Phase Synchronization

GSM 0.05 ppm NA

WCDMA 0.05 ppm NA

TD-SCDMA 0.05 ppm 3us

CDMA2000 0.05 ppm 3us

WiMAX FDD 0.05 ppm NA

WiMAX TDD 0.05 ppm 1us

LTE 0.05 ppm Prone to phase synchronization

Table 1 Different requirements for clock synchronizationof commercial viability to deliver an effective transport network.

Nevertheless, IP technology possesses certain innate drawbacks that negatively influence its position as a carrier-class service transport mechanism. The features that PTN technology requires to render it carrier-class are detailed below.

Highly precise network synchronization

Normal telecom service operation requires clock synchronization that confines offsets for frequency and phase in an entire network’s equipment to within a reasonable range. Thus network synchronization comprises both frequency and phase.

Frequency synchronization demands that signal rate must be strictly configured to ensure same frequency operations in all equipment. Phase synchronization embodies two functions - time serving and time keeping. The former concerns time synchronicity under which local time is harmonized with standard time via irregular verifications. Time keeping ensures that local time maintains a permissible difference from standard time during the synchronization process.

Synchronization in a mobile transport network is prerequisite to guaranteeing network performance and user shifts among different base stations. Currently, several wireless standards are available, and Table 1 lists the different requirements that each possesses in terms of clock synchronization.

Three packet clock synchronization technologies are available for PTN: Ethernet synchronization clock technology, which takes place at the Ethernet physical layer; Timing over Packet (TOP); and Clock over IP (based on IEEE 1588v2). The Ethernet synchronization and TOP technologies achieve frequency synchronization, while Clock over IP achieves synchronicity for both frequency and phase. Table 2 compares the three technologies.

Having overcome IP technology’s inherent network synchronizat ion weaknesses , these technologies successfully achieve synchronization for PTN and significantly assist its transformation into a carrier-class IP transport network.

End-to-End QoS guaranteesComplete QoS scheduling capability

Packet forwarding in traditional IP technology

employs the best-effort system in which all packets adhere to the first-in-first-out (FIFO) rule. This fails to guarantee throughput, delay, jitter and packet loss ratios, and is unable to provide a differentiated service mechanism that delineates audio, video and data services by their different quality requirements.

The booming mobile communications era has stimulated a wide range of new mobile services besides audio, spanning video, the Internet, online gaming, etc. The quality requirement for each differs in terms of packet transport delay and packet loss ratio, with real time services such as audio and video necessitating higher quality than, for example, Internet or download services.

To cater for the quality diversity needs inherent in mobile audio, video and data services, the transport network must identify different service types and designate them an appropriate service class. Holistic service identification and flexible QoS scheduling mechanisms allow PTN to execute DiffServ. Based on flow classification, DiffServ is established by applying technologies for CAR, queuing, scheduling, and congestion management. Thus the PTN achieves per-hop behavior (PHB) for expedited forwarding (EF), assured forwarding (AF), best-effort forwarding (BF), and their sub-classes. Consequently, operators can provide differentiated QoS guarantees for various services, and meet network requirements concerning simultaneous data, audio and video service provision.

Channelized bandwidth management

PTN promotes the channelized design concept in order to guarantee end-to-end QoS. On a network’s UNI side the service channel is divided according to hierarchical QoS (H-QoS). On the NNI side upstream channel resources - such as bandwidth -

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Achieving a carrier-class packet transport network

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Technology Strengths Weaknesses Applicable, Prioritized Scenario

Synchronous Ethernet

technology

Easily realized•

Largely unaffected by PSN damage•

Mirrors SDH clock quality•

Similar architecture to SDH clock•

Relatively mature•

Each network node must support the synchronous Ethernet •

to achieve whole-network clock synchronization.

The number of physical networks for clock extraction is •

limited.

Frequency synchronization in a PSN

TOP technology

Transparently transmits the clock across the network•

Does not require each node in the network to •

process TOP packets

Flexible use•

Easily affected by PSN.•

Not standardized for interworking between different vendors•

Trans-network synchronization and

transparent transmission of service

clock for a PSN

Clock over IP technology

based on IEEE 1588v2

Recovers time precisely•

Is standardized for interworking•

Broadly unaffected by PSN•

Each network node must be able to support IEEE 1588v2• Time synchronization in a PSN

Table 2 Comparison among the three technologies

are managed according to DiffServ-traffic engineering (DS-TE).

H - Q o S m e c h a n i s m - U N I s i d e support. Traffic QoS features are further specified by establishing an independent scheduler on each service class in order to provide class-specific services. Sufficient internal resources and equipment control policies enable operators to provide QoS guarantee for VIP users and reduce overall construction costs. H-QoS delivers the capability of using leased bandwidth more accurately and logically alongside QoS guarantees. Thus, users can control access points, overall bandwidth, and service type for single and multiple services.

D S - T E m e c h a n i s m - N N I s i d e support. To balance network traffic and guarantee service quality via the best effort system, each DS-TE channel supports eight service priorities. Based on the NMS CAC mechanism, Huawei’s PTN equipment achieves the end-to-end configuration of specified SLA service traffic, and also facilitates a range of maintenance methods such as end-to-end alarm performance.

SDH-like OAM and network protection

With its end-to-end OAM capability and e xc e l l en t n e twork p ro t e c t i on attributes, traditional SDH networks are reliable and easy to maintain, and feature relatively low OPEX. The PTN needs to

inherit OAM and network protection capabilities that equal those found in SDH.

In a similar way to the OAM capability found in SDH, PTN adopts hardware to transmit OAM packets and process the protocol state machine. An OAM protocol packet is inserted and transmitted every 3.3ms for each service flow to be tested. As stipulated in the protocol, three OAM frames are required for each fault detection procedure, and holistic fault detection is completed within 10ms. Moreover, a 50ms protection switching time is achieved simultaneously for tens of thousands of service protection groups by utilizing the APS, and the performance of the PTN OAM does not alter when OAM service traffic increases.

It a l so suppor t s an a la rm re turn mechanism similar to those found in the SDH’s AIS and RDI, and possesses OAM capabilities based on the service layer, MPLS LSP, and pseudo wire (PW). Thus, the powerful PTN OAM capability realizes end-to-end management and can be regarded as the foundation for both the PTN network and service protection.

Uniform multi-service transport and management platform

The PTN adopts pseudo wire emulation edge to edge (PWE3) to emulate and uniformly carry multiple services derived from TDM, ATM, or Ethernet. As a

technology that is designed to carry end-to-end Layer 2 services, the PWE3 belongs to point-to-point L2VPN. On the PTN’s dual provider edges (PE), LDP signaling is used to automatically distribute PW labels and RSVP-TE signaling is employed to automatically distribute LSP labels. Layer 2 data derived from the PTN’s customer edge (CE) equipment is transparently transported via a tunnel to emulate various Layer 2 services such as data packets and bit streams.

To orient network evolut ion and future development, the PTN can also be extended to the WDM, and is compatible with the microwave transport solution. In addition, the PTN is capable of forwarding SDH VC granularities, WDM wavelengths, sub-wavelengths, and Ethernet packets. Different services can be forwarded under the uniform GMPLS central control platform, and thus a mechanism becomes in effect for uniformly transporting multiple services and accomplishing network management. Operators can therefore schedule services across the entire transport network and realize uniform management.

Huawei forms a re l i ab le , proven and long-term commercial partner for operators. With an understanding of the pressures and challenges that operators encounters, Huawei has presented the most complete carrier-class IP transport network solution for mobile evolution - IPTime - to lead the transport network into the ALL IP era.

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Editor: Xue Hua [email protected]

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The combination of high performance and low cost is promoting the networklized microwave system as the optimal solution for new microwave networks, and the coming years will witness its rapid, global rise as an unrivalled technological choice for operators.

Networking microwave communication

By Liu Haosheng

HOW TO OPERATE

MAR 2008 . ISSUE 39


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Networklized microwave

n Europe, the leading operator, British Telecom (BT), is currently working to establish a suitable wireless edge access solution for its 21st century network. The

new, highly efficient, and cost-effective microwave transport network is set to offer significant cost savings for BT, in which Ethernet, SDH, and PDH will integrate to improve the network availability and flexibility.

In Pakistan, the GSM network of the mobile operator, Ufone, currently serves tens of millions of users. The sustained and rapid increase in new service provision has prompted a wave of transmission construction, central to which is the rapid and large scale deployment of microwave stations across the nation.

Booming consumer demand is yielding both opportunities and challenges for traditional microwave technology. Underpinned by point-to-point signal transmission between a transmission point and a receptor point, the pairing of which is referred to as a “hop”, the traditional system cannot be networked on its own. As a consequence, service transference, grooming or convergence necessitates equipment cascading, external equipment cross-connections or digital multiplexers.

These measures incur the detriment of additional construction and maintenance costs. Equipment cascading requires a large number of manually connected cables, as well as digital distribution frames (DDFs) or optical distribution frames (ODFs). The realization of uniform microwave and external equipment management demands a hub to connect the network management (NM) interfaces of various pieces of microwave equipment at a convergence node. If external cross-connection equipment, digital multiplexers and microwave equipment derive from different manufacturers, additional data communication equipment must be installed to facilitate NM information interworking. The implementation of these measures serves to inhibit economic viability.

If a traditional point-to-point microwave is networklized, however, such problems can be solved. Huawei has thus developed the new concept of networklized microwaves in which cross-connection is adopted within microwave equipment. Specifically, if an external cable connection is changed to the automatic cross connection of internal buses, and the microwave links are configured to act as optical transmission equipment lines and tributaries, microwave equipment becomes networklized.

A new approach

Analog microwave communication systems originated in the 1950s and their development over subsequent decades has witnessed evolution from analog to digital and from PDH to SDH. Higher modulation efficiency, greater bandwidth, longer transmission distances, and enhanced reliability denote continual progress that remains essentially market driven.

In the nascent networklized microwave system, microwave l inks are considered as l ines and tributaries of optical transmission equipment, which eradicates the weakness of point-to-point microwaves. The split-mount microwave model, for instance, is composed of indoor and outdoor units (IDUs and ODUs) and antennas. The IDU accesses a service signal, prompting baseband processing, multiplexing and IF modulation. The signal is then sent to the ODU for RF processing, before being finally transmitted by the antenna.

All digital processing operations are performed in the IDU. Functionally equivalent to an optical transmission equipment set, the IDU provides service grooming and multi-service access, and can be utilized to construct a ring network. The platform can also access 2Mb/s PDH, 155Mb/s SDH, and Gigabit Ethernet service signals.

Compared with traditional point-to-point microwave, the networklized microwave delivers the following technical advantages:

A single IDU supports multiple microwave • directions, thus eliminating the need for a manual cable connection at relay or convergence nodes.Hybrid networking can be attained through • the integration of wireless microwave and wired transmission.Service convergence and grooming can be executed • via embedded add-drop multiplex (ADM).To support multi-service transport, microwave

IDUs inherit the advanced and mature strengths of MSTP platforms. In addition to TDM services, they can carry Ethernet and ATM services through encapsulation and mapping, and provide higher-rate optical interfaces to achieve hybrid networking with optical transmission equipment. The microwave IDUs are managed by the same optical transmission equipment NMS, thus fulfilling end-to-end service grooming and management and actualizing a truly uniform transport network.

To minimize TCO

The most prominent advantage of the networklized

I

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directions. Thus, equipment CAPEX is lowered in terms of total IDU numbers.

Fig. 1 illustrates the application scenario of a backhaul network in mobile base stations. The entire network consists of 24 microwave transport nodes and 23 microwave air links. Services on all nodes are sent to convergence (HUB) and BSC nodes after convergence, which necessitates just 24 IDUs compared with 46 in the traditional point-to-point solution. While the number of ODUs and antennas remain the same, CAPEX savings are successfully achieved. Further reductions are made when considering the CAPEX and management costs associated with the DDFs, ODFs, and external ADMs integral to traditional microwave service grooming. Thus, the networklized microwave solution possesses obvious CAPEX advantages for operators.

The OPEX benefits of the networklized microwave system are also evident in a number of aspects:

Low service provisioning costs: Since the • networklized microwave adopts end-to-end configuration by using the NMS, on-site manual service provisioning becomes unnecessary. Thus, labor is saved and

microwave is that it offers a remarkably effective means for operators to significantly reduce total cost of ownership (TCO). Hop price forms the basis for quotations and network cost evaluation in the industry. This is broken down into a per hop price which refers to an air link. A hop within the traditional point-to-point equipment framework covers two IDUs, two ODUs and two antennas, which correspond to an air link for transmitting and receiving.

A comparison between point-to-point and networklized microwave systems reveals that the ODU and antenna costs are a lmost the same as they remain configured in pairs to realize a microwave hop. As for the IDU, its cost is slightly higher in the networklized microwave system since embedded with ADM. In traditional point-to-point microwave systems, however, one hop is needed in microwave equipment to provide one air link, whereas networklized microwave IDUs support multi-directional microwave links. The number of required IDUs is not dependent on the number of links, and an IDU at a transport node can support ODUs and antennas in multiple

construction time is shortened.Low maintenance costs: The networklized • microwave system adopts internal cable jumping which facilitates maintenance and capacity expansion.Low management costs: The networklized • microwave system is managed by the same NMS that is employed in Huawei’s optical transmission equipment. This realizes an end-to-end management mechanism in terms of performance and faults across the entire network.Reduction in losses caused by faults: The • NMS can accurately locate faults, which can shorten the troubleshooting time and reduce the losses. Comprehensive calculations demonstrate

that the OPEX associated with networklized microwave equipment is 16.2% lower than that of point-to-point microwave equipment.

The combination of high performance and low cost is promoting the networklized microwave system as the optimal solution for new microwave networks, and the coming years will witness its rapid, global rise as an unrivalled technological choice for operators.

Fig. 1 Microwave networking

2G Node3G Node (voice only)

BSC

2E15E1

5E1

5E1

5E1

15E1

7E1

HUB

7E1

3E1

4E1

4E114E1

14E1

4E14E1

2E1

2E12E1

2E1

2E12E1

2E1

Editor: Xu Peng [email protected]


Huawei Technologies

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Can Abis optimization really pay off?The rapid development of mobile services has increased pressure on mobile backhaul bandwidth,

especially in terms of 3G service provision. Abis optimization can to some extent ameliorate this situation

by enhancing transport efficiency, but how great is the value generated?By Chen Ni

Abis optimization in 2G and 3G networks

ncluding some well known European operators, many in the industry have already adopted leased lines or microwave technology to construct

mobile backhaul networks, which incurs very high per unit bandwidth costs. As 3G traffic grows, operators are faced with greater demands on bandwidth resources, and this has resulted in huge network capacity expansion investment. Therefore, various bandwidth optimization technologies have been developed and applied in orientation to mobile backhaul, amongst which Abis optimization is an option.

Voice services remain a dominant commercial interest for mobile operators. Since GSM systems di f fer f rom 3G UMTS systems in terms of voice service processing, Abis optimization technology presents different functions for them.

GSM systems utilize full-rate codes to process voice services, and transmission bandwidth is occupied even in the mute period of the communication process. The Abis interface, which is located between the base transceiver station (BTS) and the base station controller (BSC), has to support two major bandwidth requirements for both voice service and mute frames. According to the general traffic model, mute frames in a GSM

I

system normally occupy 50% to 60% of all BTS uplink bandwidths.

Abi s opt imiza t ion technology i s developed to delete mute frames through the BTS’s Abis interface and to multiplex the unused timeslots. The mute frames are then recovered before reaching the BSC. It can enhance 2G service transport efficiency by an average of 60%, and even 80% in best case scenarios.

3G systems employ adaptive multi-rate (AMR) technology to process voice services. As voice activation factors are introduced in coding, no mute frames exist in service bandwidth and thus 3G service transport efficiency cannot be improved by their deletions.

Limited bandwidth savings

Although Abis optimization technology creates little value for 3G systems, it seems to be an effective solution to mobile backhaul bandwidth optimization, given its 60% bandwidth optimization efficiency in GSM systems.

However, the actual situation is not so simple. Operators are challenged by bandwidth pressures not just from GSM, but also from the whole mobile backhaul system that supports both GSM and 3G. As such, an evaluation of Abis optimization technology should consider the value

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generated from bandwidth optimization across the entire mobile backhaul, rather than in GSM systems only.

At early phase of 3G services: at most 20%

When 3G services are initially provided, operators’ existing transmission networks are able to support the requirements of 2G services, and new added bandwidth for 3G services can drive mobile backhaul capacity expansion. In this instance, Node B coverage is similar to that provided by a BTS, with 95% of all Node Bs sharing the same sites as GSM BTSs. Uplink bandwidth comprises both Abis and Iub services.

In each GSM sys t em the up l ink transmission resources of individual BTSs should be configured according to the maximum bandwidth needed by the BTS type, the major ones being S1/1/1, S2/2/2 and S3/3/3. Table 1 lists the transmission bandwidths requ i red by BTS Ab i s interfaces, in which Abis optimization technology is able to optimize all Abis interfaces in the GSM system.

Each 3G network can be configured by referring to the typical 3G traffic model

BTS type TRX OML RSL 64K Time Slots Traffic

S1/1/1 3 1 3 9.4 0.60 Mbps

S2/2/2 6 1 6 17.8 1.14 Mbps

S3/3/3 9 1 9 26.2 1.68 Mbps

Table 1 Transmission bandwidth requirements of Abis interfaces network by 3 to 5 times. NTT DoCoMo in Japan, for example, began constructing its 3G network with approximately 15,000 Node Bs in place, but the maturity of iMode services based on 3G broadband applications has to date stimulated an increase in the quantity of Node Bs to around 50,000.

In mobile networks, only 20% - 25% of the base stations are 2G, and each requires 1×E1 uplink bandwidth. The remaining 80% of 3G Node Bs require 3×E1 uplink bandwidth for each, which is consistent with initial phase specifications. GSM services demand 7.7% of all bandwidth requirements (1×20%/(3×80%+1×20%)). When Abis optimization technology is employed to optimize these services across an entire mature 3G network, an operator can save only 4.62% (7.7%×60%) bandwidth at most.

How great is the application value?

An assessment of Abis optimization technology’s application in a network should not be confined to profits gained by decreased bandwidth in base stations. Consideration should also be given to bandwidth provision ability and mobile backhaul costs, which in turn determine the application of Abis optimization technology. The selection of mobile backhaul optimization or reconstruction

Can Abis optimization really pay off

and the service planning requirements of 3GPP. The calculations listed in Table 2 show that each 3G BTS calls for an uplink bandwidth of 5.61M in the early phase, which is 3.3 times the uplink bandwidth required by an S3/3/3 BTS, and 9.4 times the amount needed by an S1/1/1 BTS.

Thi s ana ly s i s demons t ra t e s tha t most bandwidth pressures encountered by operators derive from 3G services. GSM services occupy 20% of the total bandwidth in mobile backhaul and, as it is assumed that Abis optimization technology can save 60% bandwidth, 12% can be saved across the whole network, considerably less than 20%. This is insignificant in terms of reducing overall transmission capacity expansion costs.

At mature phase of 3G services: less than 5%

When data services, especially those based on high-speed data packet access (HSDPA), become mainstream, voice service-based Node Bs/BTSs are incapable of covering data service subscribers, with the number of Node Bs in a 3G network exceeding the number of BTSs in a 2G

Traffic model

Voice (mErl) 25

CS 64 data (mErl) UDI 18

PS 64/64 (bps) 100

PS 384 Traffic 150

HSDPA (bps) 1024

HSDPA minimum throughput per cell 1 Mbps

Voice activity factor 50%

Voice penetration 100%

Voice data penetration 20%

PS data penetration 40%

HSDPA penetration 50%

Subscriber per Node B 1000

Bandwidth dimension

Voice traffic 0.33 Mbps

CS data traffic 0.37 Mbps

PS 64K traffic 0.06 Mbps

PS 384K traffic 0.08 Mbps

HSDPA minimum throughput per cell(HSDPA traffic)

3.00 Mbps(0.92 Mbps)

CCH traffic 0.41 Mbps

Signaling & OM 0.43 Mbps

Engineering margin 0.94 Mbps

Traffic 5.61Mbps

Table 2 Bandwidth requirements of various 3G services

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requires an analysis based on actual network condit ions in terms of 3G network construction.

For leased line backhaul: just a supplementary

Fig. 1 illustrates that the booming d e m a n d f o r b a n d w i d t h i n c r e a s e s leased c i rcuit costs by tens or even hundreds of t imes in terms of new network construction costs. While Abis optimization equipment can garner an extra 4.6% profits from bandwidth optimization, this remains inadequate when compared with leased lines’ long-term OPEX. In this case, necessary measures to remove the pressure from bandwidth capacity expansion involve transmission network construction and the reduction of leased line use.

In typical environments or remote areas where transmission networks cannot be constructed, Abis optimization technology can be adopted to supplement a decrease in bandwidth lease costs.

For microwave backhaul: only restricted functions

Microwave mobile backhaul generally adopts a tree networking mode in which the SDH microwave is adopted at the RNC/BSC, while PDH is utilized at the Node Bs/BTS and for tributary links. As 3G services require greater bandwidth, the 4.6% extra bandwidth profits derived

from Abis optimization does not obviate the necessity for microwave network recons t ruc t ion , which incur s h igh expenditure levels.

At present, microwave backhaul follows three major trends. Firstly, the PDH microwave that supports 2 - 4 E1 channels gradually disappears at the network end, and is replaced by a microwave that supports 8 - 16 E1 channels. Secondly, the SDH microwave is progressively extended to base stations until it accounts for 40% (or more) in the network, up from the existing 20%. Thirdly, the SDH microwave, which is close to the RNC/BSC, is gradually transformed to optical fiber networking with a capacity exceeding 2×STM-1.

During microwave network reconstruction or expansion, maintenance and labor form the major portion of expenditure, as opposed to equipment. Current microwave soft modulation technology supports software upgrades from 1×E1 to STM-1, thus effectively controlling equipment hardware and maintenance upgrade costs. For example, in order to upgrade a microwave system that supports 4×E1 to a system that supports 16×E1, legacy expansion methods require USUSD9,000 for equipment migration and engineering. However, present developments allow the microwave network to be upgraded by software at almost no cost.

Due to improvements in microwave technology and efficient network cost control measures , the value of Abis optimization is rather limited in terms of

LL w/o optimization

LL after optimization

MW w/o optimization

Fiber

2×E1 4×E1 6×E1 8×E1 10×E1 12×E1 14×E1 16×E1 STM-1 STM-4 STM-16

Times

Fig. 1 Comparison of capacity expansion costs among various networking modes

microwave bandwidth cost savings.

For optical fiber backhaul: a temporary means also

O p t i c a l f i b e r m o b i l e b a c k h a u l construction can effectively improve network quality for mobile operators, and provide almost limitless bandwidth. The unit bit transmission cost of an optical transmission network is far less than the cost of deploying Abis optimization technology, demonstrating that in this case Abis optimization possesses negligible value.

Although much time is required to extend optical fibers to all Node Bs/ BTSs, doing so is increasingly popular with numerous related projects currently underway. As FTTx projects are carried out throughout the world, the optical cable price per kilometer is falling, with a unit cost in France, for example, of between EUR150 and EUR200.

Since the acquisition of optical fibers becomes easier, uplink bandwidth capacity has become unrestricted by transmission media, and Abis optimization no longer forms an expedient option for operators.

Conclusion

Abis optimization plays an important role in GSM systems and under general conditions leads to 60% bandwidth opt imiza t ion e f f i c i ency. In spec ia l c i r c u m s t a n c e s , s u c h a s i n r e m o t e mountainous areas, Abis optimization can remarkably improve the transport efficiency of 2G voice services.

As 3G services develop, the value of Abis optimization has grew insignificant. It is insufficient to fully mitigate transmission bandwidth pressures, and can only be applied as a supplementary or temporary measure. Thus, the primary means of solving backhaul network bandwidth pressures l ies in the construction of se l f -bui l t t ranspor t networks , such as microwave with soft modulat ion technology or optical fiber backhaul. Optical fiber backhaul represents the most effective means for operators to drastically release bandwidth pressure.Editor: Liu Zhonglin [email protected]

34MAR 2008 . ISSUE 39

Base Line

MAR 2008 . ISSUE 39

ackhauling mobile traffic used to be a straightforward affair for most operators: Cell sites linked to their core networks

with E1/T1 leased lines, and when the operator needed more capacity it simply provisioned more lines.

Mobile broadband services, which demand substantial increases in capacity throughout the network, not simply in the access portion, have shattered this cozy world. Consequently, mobile operators and their providers must look beyond legacy technologies to boost their backhaul capacity substantially without dramatically increasing their costs.

The arrival of HSDPA, which promises users DSL-like speeds at DSL prices, is jolting mobile operators out of their voice-centric backhaul comfort zones. Mobile broadband finally is changing how people use their mobile phones, with rich content downloads, Internet browsing and E-mail becoming commonplace. This explosion in bandwidth is putting the operators’ mobile backhaul networks under increasing strain, with some operators experiencing a three-fold increase in data traffic in less than a year.

I f opera tor s cont inue down th i s path, service quality for both voice and data applications ultimately will suffer. To prevent this happening, operators must overhaul their backhaul, since the incremental addition of more leased lines will prove economically unjustifiable. To make matters worse, much of the spending on mobile backhaul is ending up with wireline operators, which have for years seen retail revenues fall at the expense of rising mobile phone use. According to analysts at Infonetics Research, this spending amounted to USD19.5 billion in 2006 alone.

Regional variations Choosing new backhaul architecture

and cutting backhaul costs, however, is not entirely straightforward, as few operators have the same legacy backhaul infrastructure. Traditional mobile backhaul is a mixture of leased lines, private circuits and microwave circuits, so no single solution will meet the migration needs of all operators.

In the United States, T1 leased-line have been priced more competitively than in Europe. As a result, U.S. operators are more reliant on leased-line connections. In Europe, more than 60 percent of mobile operators have built their own microwave backhaul solutions, but a large base of leased-line users still exists, particularly among the mobile subsidiaries of former incumbents. Fiber is popular in the Asia Pacific, especially in countries with a rapidly developing infrastructure, such as China, and the technology is also starting to make inroads into both the U.S. and Europe.

ScalabilityBesides increasing capacity requirements,

this new data traffic is better suited to different technologies. “Operators need to look using different backhaul technologies for their data requirements,” says Nadine Manjaro, an ABI Research analyst. “Voice traffic is perfectly matched to sharing a 2Mbps T1, but if you have multiple users all trying to stream over 1Mbps of data you are going to have a bottleneck in your backhaul.”

The key is to use a more scalable backhaul technology. While it is possible to increase capacity by adding more T1/E1 lines, it is costly and can take too long

IP relieves backhaul pain

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35

By Anthony Plewes

to meet the operator’s immediate needs. Ideally, operators would like to have quickly scalable bandwidth they can use on a pay-as-you-use basis without having to change the infrastructure radically.

Ethernet is emerging as one of the best technologies to do just that. “Ethernet is attractive for operators as it matches how they are using the network,” Manjaro explains. “Because it is bursty, as opposed to fixed-like ATM, Ethernet gives you the ability to scale up and down as you need it while providing quality of service assurances.”

All roads lead to IP

Decisions about mobile backhaul must be made in view of an operator’s migration to an ALL IP infrastructure. IP is being introduced in the core, while IMS is being deployed in both fixed and mobile networks. To gain the most from IP in the core, however, a mobile operator must introduce IP throughout its entire network, so while the starting point for most operators may be different, the end result will eventually be the same.

Mobile operators can take three main routes to an eventual ALL IP infrastructure:

Continue using traditional backhaul • infrastructure, aggregate leased lines, share bandwidth between 2G and 3G networks, optimize the network and move over to a packet infrastructure when the technology is mature; Adopt a hybrid infrastructure that uses • TDM for voice and offloads HSPA data traffic to a separate packet network that will eventually carry all of the operator’s traffic; orMove directly to an ALL IP packet • infrastructure, taking advantage of

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bandwidth savings immediately.“Moving to ALL IP infrastructure is

a gradual process for most operators,” explains Gaby Junowicz, director of business development for cellular at RAD, an equipment supplier. “The most common RFQ we see is for hybrid solutions that keep the real-time traffic on the operator’s TDM network and offload HSDPA traffic onto packet transport. But all of them have a migration plan to move eventually to the IP world, as it can give them massive savings.” For one operator, according to RAD, this was calculated to lead to savings of EUR80 million (USD114 million) a year in backhaul alone.

The hybrid approach is popular in Europe as it solves the most pressing issue for mobile operators: how to handle the growth in data traffic while still preserving their investment in current backhaul technology. Backhaul solutions based on xDSL are a good match for many European operators, as connectivity is widespread and asymmetrical connections such as ADSL2+ mirror HSDPA, which offers much higher download than upload speeds.

A main concern about xDSL is the lack of robust QoS, so most operators plan to keep their voice on their existing backhaul infrastructures and just offload data traffic. Much of the data traffic they currently generate is from Internet browsing or e-mail downloads, which means operators can get away with a best-effort level of service.

Of course, operators with no legacy backhaul can sk ip TDM and move directly to a packet network. An example is Japan’s EMOBILE, which launched last spring with a HSDPA-powered mobile broadband solution. It backhauls all traffic over Ethernet transport using ATM pseudowires.

Packet advantage

Although next-generation microwave and IP Ethernet take mobile operators out of their comfort zones, they will, as noted, allow them to realize significant savings. Infonetics estimates the cost of mobile backhaul over traditional leased lines is around two and half times that of next-

generation technology, such as Ethernet. Given the sav ings , there i s l i t t l e

surprise operators are already testing and trialling Ethernet backhaul, with major deployments expected to begin in earnest in 2008. Infonetics says that while Ethernet made up just 1 percent of total mobile backhaul equipment sales in 2006, it will account for as much as 41 percent, or USD2.5 billion, of worldwide sales by 2010.

Microwave wi l l cont inue to be a key transport mechanism in Europe, with the move away from point-to-point technology helping to reduce costs significantly. European operators that have made significant investments in microwave likely will continue to develop the technology through to fully packet-based solutions. “Legacy microwave systems are TDM-based and few of them support IP streams,” says Frank Chevalier, senior consultant at Mason Consulting. “If the equipment is less than two years old, however, operators are likely to be able to upgrade it fairly easily.”

Point-to-multipoint technology allows operators to carry out radio planning more easily, using fewer antennas to cover the same area. It also allows them to aggregate traffic from multiple base stations within a single deployment, allowing them to share traffic and use the available bandwidth more efficiently.

Opera tor s , inc lud ing Vodafone , have already jumped on the microwave bandwagon to avoid high leased-line costs. “The majority of our global networks have already switched to microwave backhaul based on PDH and SDH technologies,” says a Vodafone spokesperson. “We have begun to explore how we can upgrade this technology to something that offers even more capacity. Right now, we are exploring the potentia l of Ethernet microwave, which offers an intelligent form of modulation to boost capacity still further and makes more economical use of spectrum.”

Although some operators reportedly are trialing it, fixed WiMAX is not yet particularly strong as a mobile backhaul option, even though it was init ial ly promoted as such. This is partly because much of the development effort is focused

on the technology’s 802.16e mobile vers ion, and also because of doubts surrounding WiMAX’s ability to handle QoS in backhaul networks.

Outsourcing strategies

To deal with the complexi t ies of mobile backhaul, a number of operators are looking at outsourcing. In July 2007, T-Mobile signed a 5-year deal with UK’s BT wholesale to manage its backhaul network, migrating the backhaul from leased lines to Ethernet. According to T-Mobile, the flexibility of BT’s 21CN Ethernet network was a key factor in the decision.

“By partnering with BT we are able to achieve cost savings and focus on our core business, while BT takes care of our access backhaul requirements,” said Emin Gurdenli, T-Mobile’s technology director. Previously, T-Mobile reportedly had been investigating the potential of DSL to backhaul its HSDPA traffic and was said to be planning to eventually backhaul its entire traffic over DSL to an Ethernet aggregation point.

Network sharing, which has been moot since 3G networks emerged, is another approach to cost savings in backhaul networks. The concept gained a significant boost early this year with the announcement by Vodafone and Orange in the UK that they planned to share their radio access networks. The exact details have not yet been released, but those operators will benefit more if they share the entire infrastructure, including the backhaul network. If this partnership is successful, the model will likely be replicated across Europe.

Whatever the technology migration path or strategic approach operators adopt to increase backhaul capacity, it’s clear the old days are fading fast. The take-up of data services is forcing operators to move away from their voice-centric infrastructures: They need fully converged infrastructures in both backhaul and core networks. The technology to do this has been around for some time, but operators are only now taking action.

(From telecommagazine.com)

SOLUTION

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Mobile operators need different transport solutions when building mobile transport networks and need the r igh t so lu t ions fo r different stages of development, challenges and requirements.

By He Chaohua

obile networks driven by high bandwidth and service integration, are evolving into ALL IP networks. A general concern among mobile operators is how the TDM-

based mobile transport network can seamlessly develop into a best-effort IP network while ensuring carrier-class reliability and quality of service (QoS).

Mobile operators look at transport networks in different ways. For a 2G network that moves to 3G, HSPA or LTE, the focus is on whether existing investment in the 2G transport network can be reused in the future network. Another factor is whether the transport network can offer fine scalability to meet service bearer requirements during evolution from 2G to 3G.

In a 2G/3G/HSPA hybrid network, with diversity of service types, operators focus on whether the transport network can bear 2G, 3G and HSPA services in a unified mode. For a 3G/HSPA network that requires large bandwidth, a primary concern of operators is the bandwidth costs of the transport network and whether the transport cost per bit can be decreased.

IPTime for all

SOLUTIONIPTime for all

Multi-scenario applications challenge mobile transport networks

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Huawei Technologies

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Huawei launched the IP Transport Infrastructure for Mobile Evolution (IPTime) solution to control costs and tackle different scenarios in mobile transport applications after an in-depth analysis of network requirements. The solution not only satisfies the service transport requirements of existing networks, but also supports smooth evolution of existing networks to future ALL IP networks while protecting the existing investment of operators.

2G network

2G services need relatively less bandwidth than 3G services, but 2G operators have to lease more lines or construct more synchronous digital hierarchy (SDH) or multiservice transport platform (MSTP) networks to meet subscriber growth and increased traffic, resulting in a larger network investment.

To cut transport costs, operators need improved efficiency, and wide coverage should be implemented in order to improve the QoS. This places high requirements on transport networks regarding transport reachability in various environments. Considering competition and service development, operators need to conduct unified planning on transport networks especially in the deployment of 3G networks in the future. The transport network should be scalable so that existing investment returns can be maximized in future 3G networks. In other words, a mobile transport network must cater to the stable growth of 2G services and be ready for the upcoming 3G era.

Huawei has recently released a mobile transport solution for 2G operators , with a full consideration for bearing heavy TDM services on 2G networks, network expansion, and transfer of ATM/IP services. Different access schemes can be offered according to base station access modes, and transport coverage can be improved through microwave systems or parts sharing within base stations at the same site.

If base stations are not allocated with physical resources like optical fibers, the microwave transport scheme can be used. Different radio transport network (RTN) products can be deployed at the access points and convergence points to enable service transport.

For base stations that have physical resources, the packet transport network (PTN) boxes or SmartAX multi-service access devices with customer premises equipment (CPE) can be used to access base stations. At each convergence point, the PTN device collects services and transfers them to the base station controller (BSC). The PTN device is compatible with various transport modes and can be used in

multi-mode mobile transport networks, providing excellent investment protection.

The solution above supports the optimization of Abis interfaces. The transport efficiency can increase 40% by compressing idle timeslots, idle channels and voice, and multiplexing traffic statistics. The volume demanded by 2G services is decreased, as well as the leased costs on E1 lines. The solution adopts the IP-based microwave system to enable wider transport coverage. The customized PTN boxes can share the same sites with base stations, saving equipment room space and decreasing base station deployment and maintenance costs.

All transport devices adopted in this solution are based on ALL IP architecture and cater to future ALL IP transport networks. The multi-mode transport network shares the same hardware and can be combined with SDH, MSTP and wave division multiplexing (WDM) systems. Existing investment on the transport network can be maximized in the 3G era. Its wide variety of functions and features guarantee sustainable development for 2G operators.

2G/3G/HSPA hybrid network

Commercialized 3G and HSPA services in a 2G/3G/HSPA hybrid network can cause large bandwidth pressure on the network. The number of circuits needed by each base station might increase from (1 - 2)×E1 in 2G to (5 - 10)×E1 or more. The number of base stations also increases exponentially leading to even greater bandwidth pressure.

The 2G/3G/HSPA hybrid network usually brings headaches and challenges to the operator. As 2G, 3G and HSPA services coexist at the same time, the transport network has to offer bigger bandwidth and wider transport coverage. Operators are looking for TCO reduction and a mobile transport solution that can bear multiple types of services in the same network. The solution is expected to guarantee high reliability in IP networks and provide high QoS. As various services are developed at different times, the ideal transport network should be flexibly deployed according to traffic growth, and existing network investment recycled.

For a 2G/3G/HSPA hybrid network, Huawei introduced the solution. All transport products are based on IP architecture. TDM, ATM and Ethernet services can be transported in a pseudowire edge-to-edge emulation (PWE3) mode, allowing the transport of multiple services in a unified way.

In case there are no physical resources in base stations, the microwave RTN devices can be adopted for transport. The RTN devices support E1 and fast

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Ethernet (FE) access modes, and different RTN devices can be deployed at access and convergence points to transport services. Base stations that are allocated with physical resources, PTN boxes or SmartAX multi-service access devices with optical network terminals (ONTs) can be used to access base stations through E1 or FE.

Microwave, PTN and SmartAX multi-service access devices can enable unified transport of TDM, ATM and IP services. At different converge points in a transport network, PTN devices of different capacities can be adopted to process, converge and transport diversified services at the convergence layer. All adopted transport devices provide carrier-class performance and guarantee high QoS and reliability. The solution supports multiple clock synchronization schemes. In packet networks, high-precision clock synchronization can be realized through Ethernet synchronization based on IEEE 1588v2.

The IPTime mobile transport solution above supports the offload transport mode. The PTN box on the base station can divide the voice, data and signaling services of a base station. Data services are transported through digital subscriber lines (DSLs) or the Ethernet, while voice and signaling services are transported through traditional E1 leased lines. Clock synchronization is implemented at the same time.

This solution supports the optimization of Abis/lub interfaces and can improve the transport

efficiency by 40 percent. In the offload mode, H S P A d a t a services, which require large b a n d w i d t h ,

are transported through inexpensive

DSL and Ethernet lines, saving E1 lease costs by 70 percent. The TCO is significantly decreased. The multi-mode transport network can be combined with the SDH, MSTP and WDM systems in networking and share hardware with them, to further protect existing network investment.

The use of flexible, reliable microwave products and PTN boxes that share the same sites with base stations, not only enables various coverage scenarios, but also curtails maintenance costs. Moreover, this solution realizes GPS-level high-precision timing in packet transport networks to meet mobile service requirements. The end result is a network that is more reliable, and offers SDH-like protection capabilities and complete operations, administration and maintenance (OAM) functions.

3G/HSPA network

In the 3G/HSPA network, 3G/HSPA services demand

large transport bandwidth. The explosive growth in bandwidth usage has brought huge network pressure instead of increased revenue to operators who are facing decreased profit per bit.

To change this situation, operators need to decrease the transport cost per bit while using larger bandwidth to transport service. The 3G/HSPA network should not only offer guaranteed QoS, but also enable effective QoS management to support diversified broadband services. In addition, the future-oriented transport network should enable maximum utilization of existing network investment in the fixed-mobile convergence (FMC) phase.

To free operators from the pressures and challenges noted above, Huawei has released a customized 3G/HSPA transport network solution. As the 3G/HSPA network mainly involves ATM and IP services, the mobile transport solution must transport services consuming large bandwidth in a cost-effective way. Microwave RTN devices adopted in the solution support both E1/FE access and packet microwave to address the IP trend. If physical resources are allocated on base stations, PTN boxes can be adopted for E1/FE access. In case an operator has a full-service operation plan or can lease lines, the operator can adopt the xDSL/GPON (Gigabit Passive Optical Network) access mode.

At present GPON is quite mature and its 2.5Gbps/1.25Gbps t r a n s m i s s i o n throughput fully s a t i s f i e s t h e requirements of IP transport in 3G networks. GPON s u p p o r t s m u l t i -service bearing, IP-based packet data services, plus traditional TDM and ATM services.

Offering high performance and IP service capabilities, GPON is applicable for long-time evolution of 3G networks. The SmartAX multi-service access devices support xDSL and GPON access modes and enable service transport with large bandwidth and low costs. While transporting services back to base stations, the SmartAX multi-service access devices can provide broadband services to fixed subscribers. By deploying FMC-oriented service transport networks, operators can be ready for the FMC era.

At each convergence point, PTN devices can be adopted to converge and transport services. Then services are transported to the remote network controller (RNC) through large-capacity PTN devices. The solution enables high-precision clock synchronization in packet networks through Ethernet synchronization based on IEEE 1588v2.

The IPTime mobile transport solution helps 3G

IPTime for all

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operators construct highly efficient broadband transport networks. Operators can then provide ultra broadband access for indoor and outdoor base stations and UMTS access points (APs) through a flexible fiber-to-the-x (FTTx) scheme.

The solution makes use of flexible and reliable microwave products based on packet network, supporting self-adaptive modulation and improved bandwidth efficiency, enabling wide transport coverage for large swatches of bandwidth. The ALL IP architecture is adopted for transport networks to keep pace with network development trends and hierarchical QoS guarantees the transport of various services.

In addition, the solution makes full use of optical fibers and copper cables so that a unified transport network can bear both mobile services and fixed broadband services. This can significantly decrease the TCO and operation expenditures (OPEX), as the entire transport network is based on unified end-to-end management.

Growing with a reliable partnerEvery mobile network has to support complicated application

scenarios, and mobile operators have to

use sui table products for

all network n o d e s . Huawei’s IPTime mobile transport solution

provides a complete

p r o d u c t p o r t f o l i o

i n c l u d i n g : t h e microwave RTN devices

for PoC3 nodes, ONTs, CPE, PTN boxes, SmartAX multi-service access devices for PoC2 nodes, small-capacity PTN convergence devices, and the large-capacity PTN convergence devices for PoC1 nodes. All products offer various interfaces, which are customized according to the mobile network features and facilitate the transformation of networks into ALL IP.

In the evolution of transport networks, a partner who understands the pressure and challenges operators face is mandatory for smooth operations. The partner should also have extensive experience in mobile networking and IP transformation.

Huawei is such a reliable partner in the ALL IP broadband field with its leading position in the global wireless market strengthened. Huawei has gained the largest number of new UMTS contracts in 2007 and 500 Editor: Pan Tao [email protected]

million mobile softswitch subscribers worldwide. For four consecutive years, Huawei has been No.1 in the shipment of IP DSLAM (Digital Subscriber Line Access Multiplexer) equipment and second in global optical networking; its IP transport networks have been serving the largest number of users worldwide.

China Mobile and Etisalat currently use the IPTime solution, and many other major operators, including Vodafone and France Telecom are testing functionality and performance for future deployment.

In China, Huawei constructed the world’s first IP-based GSM radio commercial network for China Mobile Shanxi, hence helping China Mobile in transforming a GSM network to an ALL IP one. The new network made full use of existing IP transport network resources to bear voice and data services, saved money on transporting TDM services, facilitated the transport of constantly increasing data traffic, and enabled the operator to provide both mobile voice services and triple-play services. As a result, the new network generated more profit and laid a solid foundation for the smooth evolution of the existing network to a future 3G ALL IP network.

Etisalat is the largest full-service operator in the UAE and demands u l t r a b r o a d b a n d i n i t s e n t i r e n e t w o rk , s o Etisalat adopts H u a w e i ’ s IPTime mobile t r a n s p o r t solution. The solution makes use of the GPON to access enterprises, family users and 3G base stations, and bear multiple types of services in a unified mode. IPTime satisfies large bandwidth requirements, cuts operational and maintenance costs, and increases profit.

Huawei’s ALL IP-based IPTime mobile transport solution is a result of many years of research, development and field experience in radio, access, data communications and transport. Providing end-to-end carrier-class performance, it supports various access modes and full-service transport, ensuring the smooth evolution of 2G networks to 3G/HSPA/LTE networks. This customized solution for operators operating 2G, 2G/3G and pure 3G networks meets requirements in different stages, and truly helps mobile operators to build IP-based transport networks of significant value.

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An alternative approachThe shift towards FTTx has yielded

vigor and vitality to traditional xDSL networks, and has stimulated a tide of upgrades that will serve to realize next generation broadband networks on a global scale. In addition to adding value for fixed network operators, it has leapt out at mobile network operators as a high bandwidth, low cost and easily achievable xDSL access mode that complements a range of backhaul solutions. However, a number of issues that must be addressed remain. For example, can bandwidth capacity meet future 100M bandwidth demands? How can the smooth future evolution of the backhaul network be guaranteed?

Division backhaul of E1 and FE interfaces

Since xDSL technology achieves a high transmission rate for short distance backhaul, FTTx provides an effective enhancement measure. The solution assumes that the base station must realize a transmission rate of 8-16Mbps. Legacy solutions require four E1/T1 leased lines, but this is reduced to one ADSL2+/VDSL2 line that is capable of meeting HSDPA data service transmission demands through the FTTB/FTTC network. In certain situations involving long distance backhaul, G.SHDSL.BIS binding of up

Growing pressure on mobile backhaul

ui l t on mult imedia se r v ice integrat ion, the 3G era has d e v e l o p e d r a p i d l y a m i d s t h i g h p u b l i c e x p e c t a t i o n s .

Mobi le broadbandizat ion forms an important industry-wide development, and sur veys i l lu s t ra te tha t 70% of mobile broadband access occurs indoors. Femtocell is specifically designed for indoor coverage, and has gradually emerged as a key solution. As small-scale BTSs are increasingly deployed indoors, higher requirements are created in terms of coverage.

The swift increase in the demand for broadband-based data services coupled with the depth of coverage required for mobile networks is set to raise the cost of base station backhaul with E1/T1 leased lines dramatically. Traditional E1, SDH leased lines and microwave solutions fail to meet required coverage, thus necessitating a backhaul solution that possesses the following characteristics:

Easily achievable • Smooth evolution potential • Reliability, with quality guarantees • Cost efficiency • The solution is a crucial facet of 3G

mobile network construction and integral to reducing total cost of ownership (TCO) while enhancing total benefit of ownership (TBO).

41

The drive to Extend Fiber Reach and Shorten Copper Loops, tends to be associated with fixed network operators. However, the convergence of fixed and mobile networks will promote the dominant application of xDSL in backhaul solutions for indoor coverage to realize broadbandization in the mobile field.

By Zhang Yufen & Wang Peng

Bto four pairs can be employed to improve broadband capability.

T h e u p l i n k s u s e d b y G S M a n d WCDMA R99/R4 base stations are TDM E1 and ATM E1 interfaces respectively, w h i l e t h e 3 G P P R 5 / R 6 - o r i e n t e d WCDMA base station utilizes E1 and FE division uplink interfaces. The future-oriented 3GPP R7/LTE base station may provide FE or even GE interface uplinks only. Therefore, we can divide the interface backhaul scenarios into three types: E1 interface backhaul only, division backhaul of E1 and FE interfaces, and FE interface backhaul only.

From the perspective of long-term mobile network development, TDM, ATM and IP interfaces will continue to coexist in the base station. Including many of Europe’s top mobile operators, numerous operators currently prefer the second scenario as it maintains the delivery of voice services over the existing network, thus ensuring voice service qual i ty. Moreover, the IP interface can provide data services and meet bandwidth demand increases while effectively reducing TCO.

The G.SHDSL Modem carries the base station’s ATM/TDM E1 frame over the Pseudo Wire Emulation Edge to Edge (PWE3) tunnel by employing its PWE3 function. The FE interface transfers the ATM/TDM E1 frame to the IP DSLAM by the ADSL2+/VDSL2 through the Ethernet frame. The IP DSLAM carries the Ethernet frame over the PWE3 tunnel,

Fixed broadband access boostsmobile broadbandization

Fixed broadband access boosts mobile broadbandization

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MAR 2008 . ISSUE 39 42

and the PWE3 tunnel can then carry the Ethernet frame to the MPLS by using its PWE3 function. Furthermore, traditional outdoor macro base stations can also connect over a long distance to optical cables’ remote DSLAM via the G.SHDSL.

The PWE3 and MPLS deliver strict quality of service (QoS) guarantees between the IP DSLAM and the convergence gateway, and the MPLS’s OAM function can achieve 50ms carrier-class network protection and restoration, reduce Operation Expenditure (OPEX), and maximize service integrity and quality.

Essential clock synchronization

In order to achieve cellular phone handover, location positioning, and bandwidth sharing between different base stations in the mobile network, the BTS and RNC/BSC clocks must be synchronized in terms of frequency, phase and time.

Clock transfer technology in the IP packet switching network can execute clock extraction from the PW link by using the ACM. Ethernet time synchronization technology extracts it from the Ethernet interface physical layer before transferring it to the IP network through the standard protocol IEEE 1588v2. This technology is also referred to as the internal clock solution. Thanks to cost advantages and a simple network structure, the solution is applicable to those nodes upon which external

clocks cannot be adopted. However, it also results in flawed clock accuracy, and severe impact of IP packet switching on network quality, causing delays, jitters, as well as large-scale network equipment transformation. To use the Synchronous Ethernet technology, nodes in the packet switching network must enable clock signal transfer in the physical layer. In line with technological improvements and a thorough R&D process, Huawei’s internal clock solution can fully meet mobile stations’ carrier-class requirements regarding time accuracy.

Moving towards a bright futureIn response to fixed and mobile broadbandization

convergence, integrated operators can provide small indoor base stations with convenient and cost-effective backhaul solutions by fully exploiting the advantages of mature xDSL networks, such as wide coverage. Both fixed and mobile broadband networks can maximize resource reuse to accelerate service provisioning and reduce operators’ capital expenditure (CAPEX) and OPEX. Furthermore, the FTTx network structure is able to smoothly evolve to Fiber to the Home (FTTH). Thus the future-oriented mobile backhaul solution not only realizes considerable lease expense savings, but also creates a new service growth model.

Editor: Chen Yuhong [email protected]

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New NMS for new networks

he development of mobile transport networks has catalyzed the transition from the single SDH network management system (NMS) to the MSTP NMS, and

evolving into a multi-technology integrated NMS that centralizes management of the packet transport network.

Mobile transport networks are moving in the direction of packet transport networks. OTN equipment will be deployed on the network to meet the demand for ever-increasing bandwidth. Even DSLAM devices will be networked for Fixed Mobile Convergence (FMC). Traditional PDH and SDH microwave systems are involving to packet microwave Ethernet systems along with the development of mobile transport networks. Concurrently, the NMS must transform to an integrated multi-technology system.

Three rules to follow

The ultimate purpose of network management is to reduce the costs of operation and maintenance. The NMS has also taken a great leap forward with the mobile transport network moving towards ALL IP.

Given the growing competition in the telecom industry, operators are expecting stronger network management, operations and maintenance to rise to the challenges of running mobile transport networks.

Compatible with existing systems and networks

I

Evolving mobile transport NMS

T

Evolving mobile transport

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MAR 2008 . ISSUE 39

NMS

44

By Wang Shaosen

Continuous forward compatibility puts a heavy load on a new system, but has become a critical imperative for telecom operations. The NMS should be able to manage existing SDH and MSTP networks, support existing OSS interfaces, and susta in operat ions for forward compatibility.

New transport networks are designed with the intention of using the original network, with new packet transport devices that feature s trong forward compatibility.

Fo r e x a m p l e , P T N d e v i c e s a r e interconnected with original MSTP devices, and are even compatible with original boa rd s and componen t s . Fo r wa rd compatibility means seamless service connectivity between new and old devices, and supports hybrid networking physically. The new NMS is expected to provide centralized network management, allowing operators to reduce maintenance costs with connected services and shared parts.

The new NMS is required to provide compability with the OSS. Operators have been spending good money on OSSs that have spanned several technical stages and their long-term investment should be protected, while lowering operation and maintenance costs.

One deciding factor that contributes subs tant i a l l y to the opera t ion and maintenance costs is training for maintenance engineers. No technological evolution

fares well if it requires extensive technical training to get up and running. The new generation packet transport NMS is expected to be compatible with the old system in operation and maintenance, and will significantly reduce the cost of learning new technologies, while hastening deployment of the packet transport network.

Unified management of technologies

A few years ago, the mobile transport network relied on ATM, SDH and MSTP devices and featured a fiber-based transport network. Terminal access was realized by microwave devices, which belonged to the wireless transport network. These two networks had only simple internetworking at the edge. Therefore, maintenance of the devices in the two networks could be performed separately, and eliminated the need to manage a variety of technologies.

Various transport technologies are heading in the same direction during the transition from the transport network to the packet transport network.

Vodafone’s mobile transport network scheme states clearly that microwave devices for terminal access and the backhaul network from the access layer to the backbone layer must evolve toward the packet transport network based on PWE3. This is how the microwave devices are

Evolving mobile transport

connected with the core packet transport devices through PWE3. Obviously, separate maintenance of the microwave and packet transport devices will adversely affect unified service management and considerably increase maintenance costs.

Likewise, traditional access devices such as the DSLAM device will be the best bet to match the FMC requirements of the mobile transport network. Like microvave devices, DSLAM devices as part of the transmission channel also need centralized management.

E2E network service management

As a new service management model rooted in the traditional SDH NMS, end to end (E2E) management is still the preferred option in managing packet transport networks despite its challenges.

Great changes in the management • model

Before packet transport technology b e c a m e o p e r a t i o n a l , n e t w o r k i n g technologies were independent of each other and services were transported part-by-part across different technology domains. The E2E management model was used only within the same technology domain.

Thanks to packet transport technology, the PWE3 transport channel runs through

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the entire bearer network from terminal access to the core layer. The E2E service bearer elements, such as E2E L2 VPN and ATM/Eth/CES PWE, contain a diversity of connection channels using diverse technologies. These channels are trunk links in NMS software modeling. In this situation, for unified upper-layer PWE3 management, trunk links across different technology domains must be logically abstracted and properly modeled to provide consistent interfacing with upper services. Thus, the user interfaces can focus on E2E services to minimize the differences across technology fields.

Increasing complexity in service scheduling•

Conventionally, MSTP networking services are scheduled in two ways: single node based cross-connection management and network-oriented E2E circuit service scheduling. The second scheduling model is obviously more complex. The same is true for the packet transport network. The complexity of scheduling network-oriented E2E services will not increase linearly but exponentially.

In the MSTP network, channel resources are fixed and the link capacity does not vary accoding to bearer services. For such a network, the E2E service scheduling algorithm is simply a universal routing algorithm.

But things have changed in the packet transport network. Despite the fixed physical capacity, a link’s logical service capacity and bandwidth usage vary according to the QoS requirements of bearer services on the link. This requires the package transport network to address the QoS in traffic distribution by using the distribution policy. If the QoS policy is designed to deliver assured bandwidth anytime, routing and bandwidth binding are similar to the distribution of MSTP service channels. If the QoS policy does not need a high priority but allows for preemption, routing and bandwidth binding must address the QoS policy. Even when bandwidth is running short, traffic can still be distributed based on required QoS.

To distribute and deploy services according to the preset QoS policy on the network, the packet transport devices must provide the required capabilities and the NMS must realize centralized E2E resource management. The devices and the NMS play different roles depending on the technology. For example, with T-MPLS, the NMS does the most work, but with signaling-supported dynamic MPLS, the network devices will play a bigger role.

Stronger E2E QoS management •

Traditional MSTP networks deliver assured QoS

and QoS management requires little maintenance. But in the packet transport network, QoS management is an important part of the maintenance.

In terms of transport, QoS management is set to deliver QoS assurance as required. In terms of management, QoS management means helping maintenance engineers gain quick access to the QoS information. This relies heavily on E2E management capability, which allows users to query and modify QoS data on managed elements. The QoS information enables maintenance engineers to measure service SLA.

Other E2E requirements•

In addition to addressing the challenges discussed earlier, the mobile packet transport network needs to provide robust E2E management capabilities, including graphical route presentation, E2E fault management and performance management. These capabilities form the core E2E management competencies, help operators significantly improve maintenance efficiency and reduce costs.

New NMS, new competenciesThe future NMS will face huge challenges. A

matured NMS will help operators greatly reduce their costs of operation and maintenance.

The T2000 in Huawei’s iManager s e r i e s has been widely used around the world for 10 years as an integrated management system for transport networks. It provides a full range of E2E management capabilities. The T2000 is even well positioned to serve all the needs of a mobile transport network built on packet transport technology.

Evolving from the traditional NMS, the T2000 provides seamless forward compatibility and supports centralized management of microwave, MSTP, PTN and OTN devices. In addition, Huawei is expanding its capabilities to manage other access devices.

The E2E management capabilities of the packet transport network, including packet microwave devices, have been built into the T2000 E2E subsystem. The subsystem, together with SDH/MSTP and WDM/OTN E2E capabil it ies , i s becoming part of the E2E core module and representative of the new trend.

Despite the tremendous challenges posed by the new generation mobile transport network designed for packet transport, the NMS will surely stay at the forefront of technological innovation, and help operators reduce network operation and maintenance costs.

Editor: Xu Ping [email protected]

Evolving mobile transport NMS

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You can choose from various PTN technologies, including PBB-TE, IP/MPLS, and T-MPLS. Which one is the most effective for mobile backhaul?

By Pu Yun

What technologies are available?

apidly expanding mobile data services, especially 3G HSPA services, have been consuming increasingly more bandwidth

from the mobile backhaul. Traditional technologies adopted in mobile backhaul, which are based on the PDH and SDH/SONET, are appropriate for transporting TDM services.

Since data services are growing quickly and mobile network development is moving

Rtowards ALL IP, operators must choose technologies that can transport data services and meet carrier-class service requirements.

Existing mobile services are placing great demands on mobile backhaul, which is between BTS/Node B and BSC/RNC. A good mobile backhaul network is expected to offer high bandwidth, high reliability, high quality of service (QoS), good scalability, strong support for voice, data and video services, and low cost.

Packet switching technology is adequate for bearing data services, but cannot meet carrier-class service requirements such as QoS, security, OAM, and protection. Yet,

Technology choices for

packet switching feature enhancements can meet the needs of mobile backhaul.

Packet t ransport network (PTN) technologies, including Provider Backbone Bridge - Traffic Engineering (PBB-TE), IP/MPLS and Transport Multi-Protocol Label Switching (T-MPLS), satisfy carrier-class transport requirements in the same way. But which of the three technologies is most suitable for mobile backhaul?

PBB-TE

Traditional Ethernet enables multiple

mobile backhaul

LEADING EDGE

MAR 2008 . ISSUE 3947


services and supports point-to-point (P2P), point-to-multipoint (P2MP) and multipoint-to-multipoint (MP2MP) distribution of services. Nevertheless, it is deficient as a transport technology. Some Ethernet technologies, for example, 802.1d, 802.1Q, and 802.1ad supporting QinQ, are unable to support large-scale networks. Their MAC address spaces adopt a planar structure, which leads to irregular and non-hierarchical distribution of addresses.

The forwarding table is consequently very large, because addresses cannot be summarized. The setup of a forwarding table through flooding-based delivery and self-learning mechanism is not stable when considered as a transport technology. The unstable network with uncertain routing can barely enable channel protection, QoS guarantee, or traffic engineering.

The 802.1ah technology, namely th e PBB t e chno logy, i s a c tua l l y a connectionless layer-2 (L2) network technology using an operator’s MAC address to encapsulate a user’s MAC address. The PBB network adopts the operator’s MAC address for addressing and forwarding. This can effectively isolate the user’s MAC address and make the network more flexible.

PBB technology keeps the spanning tree protocol (STP) technology and sets up a forwarding table that relies on flooding-based delivery and self-learning mechanism, but provides inadequate protection for services. Also, the fault recovery duration can hardly reach 50ms and it doesn’t enable a QoS guarantee or traffic engineering.

The PBB-TE technology based on PBB is a connection-oriented technology. It suppor t s comple t e pa th backup and provides good protection, traffic engineering, and a strict guarantee of QoS.

Hierarchical encapsulation and service support

The PBB-TE network adopts the same frame structure as the PBB network, which is specified and defined in IEEE 802.1ah. On the backbone edge bridge (BEB) of the PBB/PBB-TE network, an Ethernet frame header of the operator is encapsulated on

the Ethernet data frame of the user. The user’s MAC address is invisible to

the PBB/PBB-TE network, and the user network is clearly separated from the PBB/PBB-TE network. The network can then adopt a hierarchical structure. See Fig. 1 for the frame structure of the PBB/PBB-TE network.

The hierarchical network structure can reduce the size of the forwarding table and simplify network planning and operations.

The Ethernet switch in the PBB/PBB-TE network has less storage and processing

destination MAC address B-DA and V L A N i d e n t i f i e r B - V I D i n f r a m e forwarding. But the PBB-TE network disables functionality of the spanning tree, broadcast and MAC address self-learning.

The STP technology was developed to avoid loops or broadcast storms in the Ethernet. It does not place a high requirement upon the service convergence time due to network topology changes. Service convergence takes tens of seconds.

Rapid STP (RSTP) and multiple STP (MSTP) technologies, though greatly

Fig. 1 Frame structure of the PBB/PBB-TE network

requirements, as it processes only BEB MAC addresses. This solves many problems concerning network security and avoids possible broadcast storms and potential forwarding loops in user’s network. The network is more robust, and there are no worries about conflicts between the virtual local area network (VLAN), MAC addresses and the user network.

802.1ah technology extends the service instance I-Tag and identifies it with a 24-bit I-SID, which in theory supports 16,777,215 users . Enormous I-SID space ensures good network and service scalability.

Forwarding and protection mechanisms

Like the PBB network, the PBB-TE network adopts the same frame encapsu la t ion format and use s the

enhanced, can only reduce the service convergence time to several seconds, and can hardly meet the carrier-class requirement of less than 50ms.

The PBB-TE technology completely discards the STP technology and uses the management plane or control plane to avoid network loops. Specifically, it sets up a QoS-guaranteed Ethernet switched path (ESP) through the network management system or signaling according to the user’s service needs.

On each switching node that the ESP passes, the network management system or signaling sets up forwarding table entries and reserves resources. The forwarding table entries are the same as in traditional Ethernet and comprise destination MAC addresses and VIDs. The BVID in the PBB-TE network is no longer needed to isolate broadcasting and is not valid in the whole network. Instead, different B-DAs

802.1d

802.1q

802.1ad

802.1ah

Payload

SA

DA

Payload

VID

SA

DA

Payload

C-VID

S-VID

SA

DA

Payload

C-VID

S-VID

SA

DA

I-SID

B-VID

B-SA

B-DA

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can use the same BVID. BVID, B-DA and B-SA are used together to

identify an ESP. If different BVIDs are adopted by the same B-SA or B-DA, multiple ESPs can be established to facilitate path protection and traffic engineering. Let’s look at an example. Set up a working ESP for services by using VID y and set up a protection path by using VID x. In case the working path fails, services can be easily switched to the protection path for transmission and be protected within 50ms.

The PBB-TE switch discards frames with unknown destinations rather than broadcasting

establishment of a virtual private network (VPN). In an IP/MPLS network, end-to-end connections

can be provided through the virtual private wire service (VPWS) or virtual private LAN service (VPLS). VPLS is a multipoint-interconnected L2 VPN technology based on the point-to-point MPLS. From the user’s viewpoint, the technology enables all sites to connect to a private LAN.

MPLS-based VPLS technology adopts two-layer MPLS labels for encapsulation and is independent of physical topologies. It supports all logical topologies and enables high networking flexibility. It also uses the traffic engineering function of the MPLS

Since data services are growing quickly and mobile network development is moving towards ALL IP, operators must choose technologies that can transport data services and meet carrier-class service requirements.

them to avoid loops. In this way, the network runs well without using STP technology.

PBB-TE technology is connection-oriented and the self-learning mechanism is disabled as it is not required. The forwarding table entries are established through the network management system or the signaling technology.

Standardization of PBB-TE can be mainly found in IEEE 802.1Qay and further standardization is ongoing.

IP/MPLS

MPLS is a switching technology that combines layer-3 (L3) routes with L2 properties. It adopts the labeling mechanism and separates route selection from data forwarding. Labels are used to define the paths of packets in the network so that a connection mode is introduced into the connectionless network. Advantages of the MPLS technology are embodied in the QoS guarantee, traffic engineering, and

technology to optimize resource configurations. With the fast rerouting (FRR) function, the

VPLS technology can implement protection switching within less than 50ms. It supports L2/3/4 extensible access control list (ACL) and ACL control for each user, and provides security control and policy mechanisms. The VPLS technology shows good L2 convergence capability and supports more users than those limited by 4096 VIDs in a traditional Ethernet. It enables hierarchical VPLS (HVPLS) to further improve network scalability for supporting millions of users. It distinguishes and guarantees service flows of different users and enables simple service configurations and quick service provision. VPLS technology clearly separates the operator’s network from the user network and facilitates network management.

VPWS and VPLS adopt the pseudowire emulation edge-to-edge (PWE3) technology to enable end-to-end L2 circuit emulation. The end-to-end label switched path is called a pseudowire (PW), which is irrelevant to protocols. Frame relay

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(FR), asynchronous transfer mode (ATM), SDH and Ethernet traffic flows can all be transparently transmitted trough the PW. A network based on this mode can benefit from IP/MPLS features, including switching, signaling, routing, quality control, and QoS.

T-MPLSITU-T defines the T-MPLS technology in

several recommendations, including G.8110.1 and G.8112. The recommendation G.8110 defines the functional system architecture of T-MPLS. The T-MPLS technology is a connection-oriented packet transport technology based on MPLS. Being a subset of MPLS, T-MPLS effectively integrates data communication technologies within the existing telecom network.

C o m p l i c a t e d M P L S t e c h n o l o g y m i g h t significantly increase equipment costs and network complexity if it is completely introduced into mobile backhaul. To meet packet transport requirements, the T-MPLS is streamlined based on the MPLS technology by discarding the connectionless IP-based forwarding function, simplifying the data plane.

T-MPLS technology, designed with perfect end-to-end OAM functionality and protection switching functions to improve network performance and survivability, meets the requirements of carrier-class services.

The T-MPLS technology provides the following new functions:

OAM function

A transport network can guarantee high quality traffic transmission only if it has an efficient OAM mechanism. The ITU-T recommendation G.8114 defines the OAM mechanism that manages the T-MPLS layer network and service user plane based on Y.1711 and the T-MPLS architecture defined in G.8110.1 for P2P and P2MP T-MPLS connections. This enables efficient operations and maintenance on the T-MPLS network through connectivity, fault and performance management. Like other transport networks, the T-MPLS network is designed with continuity check, alarm indication signal, and remote defect indication functions. Hierarchical OAM is adopted to nest the maintenance entity group (MEG). As OAM is implemented in different network layers, network management becomes very flexible.

Protection function

ITU-T G. 8131 defines the T-MPLS linear

protection switching mechanism, and G.8132 defines the T-MPLS loop protection mechanism. The T-MPLS technology enables service protection in various network topologies and meets the protection requirements of carrier-class services.

Compared with MPLS technology, T-MPLS adopts architecture that separates the data plane from the control plane. This facilitates network function provisions and makes the network more reliable and stable.

Comparison of the threeThe analysis above concludes that IP/MPLS

technology is mature enough for various application scenarios. The technology is quite complicated, and network planning, operating and maintenance are more difficult and the IP/MPLS routers are quite expensive. In mobile backhaul, all services on the BTS/Node B are transported to the BSC/RNC, so no complicated routing is needed. The powerful routing function of IP/MPLS is wasted for it is of little use in mobile backhaul. Therefore, this technology is suitable for constructing the bearer networks for mobile core networks.

The T-MPLS technology uses the data plane of MPLS technology and simplifies the complicated application scenarios of MPLS. It decreases equipment, operation and maintenance costs, and separates the data plane from the control plane. This leads to higher network stability and reliability as well as greater networking flexibility. The operator can adopt static configurations in network management to replace the generalized MPLS (GMPLS) control plane. The T-MPLS technology defines strong OAM and protection switching features, which satisfy the needs of mobile backhaul.

The PBB-TE technology is derived from traditional Ethernet technologies and expected to inherit their cost effectiveness. For both PBB-TE and T-MPLS, standardization organizations are making specifications on OAM and protection functions to meet the requirements of transport networks. Like the T-MPLS network, the data plane and the control plane are also separated in the PBB-TE network. The network is stable, reliable and flexible. The operator can also use static configurations in network management to replace the GMPLS control plane. The functionality of PBB-TE technology can meet the stringent requirements of mobile backhaul. Additionally, the PBB-TE network can coexist with the PBB network, and can easily support multicast, giving it a definite advantage over MPLS and T-MPLS networks.

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Editor: Liu Zhonglin [email protected]


Huawei Technologies

MAR 2008 . ISSUE 39

The packet microwave solutionThe packet microwave system is oriented to ALL IP transport networks. It adopts packet switching as the core technology and uses pure packet structure on the air interface.

Bottlenecks for traditional microwave systems

n microwave-based mobile backhaul networks, the plesiochronous digital hierarchy (PDH) microwave is adopted in the access layer, while the synchronous digital hierarchy (SDH)

microwave is used in the convergence layer. When evolving to IP-based and broadband networks, the microwave-based mobile backhaul networks have encountered technical bottlenecks including:

Insufficient bandwidth for service development

Traditional time division multiplexing (TDM) microwave system features low efficiency in using air interface bandwidth. At present, as the mobile traffic involves mostly voice services, bandwidth is still sufficient for transporting services. However, as 3G services such as HSPA become more popular and develop rapidly, TDM-based microwave systems will begin to falter. Forecasts indicate that by 2012, booming data traffic will cause a four-fold increase in transport bandwidth for mobile local networks.

Poor capability of accessing and bearing packet services

TDM-based microwave systems perform poorly when accessing and bearing IP services, and there are only a few microwave equipment vendors who support IP over PDH technology. Presently, PDH-based microwave systems are incapable of providing strong access capability. SDH-based microwave systems also have rather poor support for packet services. Because packet services have to be encapsulated in generic framing procedure (GFP) frames in the Ethernet over SDH (EoS) mode, and then mapped to the virtual container (VC) for transmission. This results in a waste of air interface bandwidth, and indoor units (IDUs) adopted in SDH-based microwave systems can access only a limited number of packet services.

To meet the new market conditions driven by the trend toward IP-based and broadband mobile networks, new technologies need to be introduced to ease the bottlenecks created by microwave communications systems.

Four features of the packet microwave

To guarantee long-term service development, the mobile transport solution adopting microwave technology for service access must support IP bearing and large capacity to meet network needs.

50

To build IP-based broadband mobile networks, you need

By Cui Jiang

Huawei Technologies

MAR 2008 . ISSUE 39

I

LEADING EDGE

MAR 2008 . ISSUE 3951

The packet microwave solution

For future mobile broadband networks, an end-to-end mobile broadband solution lies in a packet transport network (PTN) that combines both microwave system and optical fiber system to offer pure packet architecture.

The packet microwave system is oriented to ALL IP transport networks. It adopts packet switching as the core technology and uses pure packet structure on the air interface. Through the IDU, the user network interface (UNI) can be used to access IP services like fast Ethernet (FE) service. Legacy TDM services can be accessed in the pseudo wire emulation edge-to-edge (PWE3) mode.

The packet microwave system can form a logical end-to-end PTN independently or along with the packet fiber transport network, providing high-quality service transport based on supported network protocols, such as multiprotocol label switching (MPLS), transport MPLS (T-MPLS) and provider backbone bridge - traffic engineering (PBB-TE). The packet microwave system has the following characteristics:

Improved bandwidth utilization

Traditional microwave systems mostly adopt an Ethernet over PDH/SDH mode to provide Ethernet features, yet have complicated mapping and multiplex layers. Also, traditional microwave systems are inherently inefficient for transporting packet services because of poor burst traffic support, high costs, and low-efficient bandwidth usage.

The packet microwave system adopts the pure packet switching kernel and the pure packet air interface structure to improve bandwidth multiplexing and transport efficiency, and offer better burst traffic support. Optimization of the microwave frame and link-layer protocols, allows the system to process more traffic by using limited microwave air interface resources.

Adaptive code modulation technology

Adaptive code modulation technology can be used to automatical ly adjust modulation modes and dynamically enable service transport according to the

performance of air interface channels that might be affected by bad weather conditions.

The modulation mode can be changed (for example, from 128QAM to 16QAM) to enable error-free communications. As a result, the access bandwidth of the microwave air interface is decreased from STM-1 to 32E1 or even 16E1. Low priority services become invalid, while high priority services are protected. The system will automatically recover the original rate when the channel quality is recovered.

Adaptive code modulation technology also significantly strengthens bandwidth capability, resulting in high scalability, low-cost maintenance, fast deployment, and increased adaptability, which enable microwave systems to adapt to different types of densely populated areas.

Circuit emulation supports TDM services

TDM-based service transport occupies fixed bandwidth. The PTN, however, uses bandwidth with statistical multiplexing and transports TDM services through circuit emulation technologies, such as PWE3. All services are then transported via the packet kernel and interfaces, allowing the system to interconnect with other data communications equipment.

Traditional 2G networks are TDM-based. 3GR99/R4 adopts the asynchronous transfer mode (ATM), but 3GR5/R6/LTE/WiMAX networks will evolve to ALL IP networks. TDM services and packet services will probably coexist in the same network using PWE3 technology

for quite some time. TDM services of the GSM network and ATM services of the universal mobile telecommunications system (UMTS) will all be transported by the PTN.

Packet-based clock transfer technology

Mobile communications services are highly dependent on clock and timing information transfer. Packet-based clock transfer technology is now more mature and can be applied in packet microwave systems. The packet microwave system and the PTN support various packet-based clock transfer protocols, such as synchronous Ethernet, Timing-over-Packet (ToP), and IEEE 1588V2, providing end-to-end and network-wide synchronization solutions.

Evolution solutionsHuawei pioneered in creating two

evolution solutions to help traditional microwave systems meet mobile network requirements and service development.

In the microwave system evolution, hybrid transport modes are supported when TDM and ATM services coexist during the transformation of mobile services from TDM E1/IMA E1 to FE. The air interface supports the transport of both TDM services and packet services. Services are encapsulated in unified microwave frames. The system can then support pure packet transport after the simple hardware promotion.

In the equipment evolution, pure packet microwave equipment and packet transport equipment are integrated if mobile operators build their own optical fiber-based transport networks instead of leasing frequencies for microwave transport. An operator can start by constructing only a packet microwave system. After the optical fibers are in place, the operator can pull out the intermediate frequency (IF) boards to transform the packet microwave equipment to PTN equipment . The new PTN supports various optical fiber networking schemes so that operators can maximally protect investments and strategically decrease operation expenditures (OPEX).

To meet the new market conditions driven by the trend toward IP-based and broadband mobile networks, the packet microwave solution is

needed.

Editor: Xu Peng [email protected]

Huawei Technologies

MAR 2008 . ISSUE 39 52

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