Broadband Radio Access Networks

Challenges

Prof. Hamid Aghvami

Centre for Telecommunications Research- King’s College London

Emerging candidates for next generation broadband radio

networks (4G?)

• 3GPP LTE

• 3GPP2 Ultra Mobile Broadband (UMB)

• Mobile WiMAX

Common features among them:

• OFDM-based air interface

• Adaptive modulation and coding

• Hybrid ARQ

• Fast scheduling

• MIMO and beam forming antennas.

• IP-based access network

NAP: Network Access Provider

ASN: Access Service Network

CSN: Connectivity Service Network

ASP: Application Service Provider

NSP: Network Service Provider

Source: WiMAX Forum

WiMAX Network Reference Model (NRM)

IP Based WiMAX Network Architecture

An open issue is:

How to split the radio resource and mobility management functionalities

between the BS and ASN GW.

Wireless Access Network Design

(In the context of end-to-end networking)

In the context of end-to-end networking ?

• End-to-end QoS

• End-to-end security

• End-to-end seamless mobility

Three main functionality groups of a wireless access network are:

- Mobility management

- QoS

- Security

Mobility Management

• The mobility management of a wireless access network includes how to solve

the problems of local seamless handover, idle mode and paging, and of course

the routing capabilities within the access network that allow these to take place

without constant address reassignment.

• All of these, especially the last, have major impacts on the internal architecture

of the access network, in terms of location of functionality in different network

elements.

QoS

• The problems are:

- How to identify the specific problems of mobility and radio access impacts

on the provision of end-to-end QoS.

- What requirements on external networks might be needed to enable QoS

mechanisms within the access network to operate.

- How to adapt QoS concepts for the fixed Internet to the mobile wireless

environment.

Security

Problems are:

Within one access network

• Security interaction with mobility and QoS?

• What requirements on external networks might be needed to enable security

mechanisms within the access network to operate.

Between Networks

• Networks have different identity management systems and security

requirements including confidentiality, integrity and authentication. An E2E

security framework is required.

• Users are required to sign in, multiple times with different operators/accounts.

A single-sign-on is required

Combined mechanisms?

• Mobility, QoS and Security mechanisms have traditionally been designed, each in isolation using different approaches

• When put together in one network, the overall performance has not been as expected.

• To minimise the negative interactions among these mechanisms, they should be designed simultaneously using the same approach and with a common signalling protocol.

Mo

bili

ty M

an

ag

em

en

tQuality

of S

ervice

Security

Challenges

• Within an access network, different design approaches have been

considered for QoS, mobility and security mechanisms

in isolation without considering their inherent interactions

• Access Networks are expected to use different QoS, mobility and security

mechanisms. To achieve end-to-end networking across them is a

challenging task.

Mobile VCE Ubiquitous Services Project

How?

• This will be done by selectively placing a number of enhanced nodes within

the network, capable of communicating with each other.

• New mechanisms will be provided to counteract the negative interactions

between QoS , mobility and security.

Mobile VCE Ubiquitous Services Project

Future Internet

Access Network 1 Access Network 2

Intra access network

signaling

Inter access network

signalingEnhanced nodes

Network layer

Link Layer

Mobility QoS Security

RR

M

Architecture for Enhanced Nodes

S

I

G

N

A

L

L

I

N

G

Mobility Management

Quality of Service

Security

Interactions

between

different

ModulesCommon

signalling

where

possible

Taking optimal decisions in a combined mannerMinimising delays and signalling overhead

Mobility,

QoS and

RRM

Modules

Architecture Components

Initial study

• Major Micro Mobility solutions such as Hierarchical Mobile IPv6 propose having

Mobility Agent(s) within access networks to minimise handover signalling

• Having a node through which all packets flow through will have an effect on the

resources of the network. (i.e. increase congestion which will reduce the network

throughput and the number of users the network can support)

• No work has been done to study how the presence of MAPs affect the resources

within an access network.

Introduction to the problem

Internet

Mobile Anchor

Point (MAP)

Generalised View

NEXT GENERATION INTERNET

Laptop

Different mobility patterns creating different traffic demands and flows

High congestion

Network Throughput with 18 nodes

Network Throughput with 35 nodes

More challenges

• Even within a radio access network, supporting network edge-to-terminal

QoS and Security are challenging.

• QoS and security mechanisms used in the air interface and the wired part

of access networks are different.

• To support end-to-end QoS and security, the parameters of the network

QoS and security should be mapped properly to the parameters of QoS

and security mechanisms used in the MAC layer of the BS (air interface).

End-to-End QoS and Security

End-to End QoS Support in an Interworking Environment

An Example

DiffServ-aware priority Queuing for IP QoS Support

On HSDPA

IP QoS for evolved UMTS

• IP for evolved UMTS CN/RAN.– Low infrastructure cost.

– Mitigated network administration and maintenance.

– End-to-end QoS routing.

• DiffServ for IP QoS– Packets are classified and marked to receive a particular per-hop forwarding

behaviour on nodes along their path.

– Sophisticated classification, marking, policing, and shaping operations need

only be implemented at network boundaries or hosts.

DiffServborder

Data flow

IP QoS for evolved UMTS

SGSN

IP-Based RAN

HLR

GGSNRNCBS

IP-Based CN

HSDPA

HSUPA

• All Previously reported scheduling algorithms for HSDPA consider only one queue per user.

• The scheduling is handled in the MAC layer of the Node B.

• The MAC header has 3 bits dedicated to indicate the queue ID. Thus, each user can have up to 8 simultaneous queues in parallel.

• Each queue may be assigned a priority level. Each DSCP is mapped onto the corresponding priority level. The packets with the same DSCP are forwarded to the correct queue.

Priority Queuing

Priority queuing (Node B architecture)

Pa

cke

t d

istr

ibu

tor

HARQsignaling

CQI

HARQretransmissions

HARQ #1

HARQ #2

HARQ #6

...

Tx ant.

Queue #1

Queue #2

Queue #8

...

Scheduler(MCS & MUX)

Priorityqueues

Queues of the same priority level are

treated equally.

# users

Priority queuing (UE architecture)

Re

ord

eri

ng

qu

eu

e

dis

trib

uto

r

HARQ #1

HARQ #2

HARQ #6

... M

UX

Recovered

data

ACK / NACKCQI

SIRestimator

Feedback

MUX

Rx ant.

HARQsoft combining

Reorderingqueues

Queue #1

Queue #2

Queue #8

...

Killer Applications and Services?

Services and RevenuesR

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r U

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( ££))

00

0.100.10

0.200.20

0.300.30

0.400.40

0.500.50

0.600.60

0.700.70

0.800.80

0.900.90

11

2000200010001000500500 15001500750750250250 12501250 17501750

Throughput/Performance Requirement (Kbps)Throughput/Performance Requirement (Kbps)

On-line gaming

Game downloads

Video/TV streaming

MMS

Text Messages

Music

Web browsing

Email

Video phone

Paid applications

Paid services

Source: BT Technology Journal

Trends in media creation/consumption

Source: COMSCOR, JUNIPER RESREACH

Thank You

Any Question?