Upload
moduarte
View
7
Download
0
Embed Size (px)
DESCRIPTION
Broadband Loop: A full service access network
Citation preview
7/18/2019 Andersen Duarte Et Ali IEEE ComMag 1997
http://slidepdf.com/reader/full/andersen-duarte-et-ali-ieee-commag-1997 1/6
ABSTRACT
There is a worldw ide ef fort to define a ful l-service access network. The Broadbandloop project was form ed by a European con sortium
funded by the European Union with th e objective o f defining a strategy for evolution from a narrowband voice and data network to a
broadband network The project is defining a system concept based on new innovative PON technology, which enables fiber to cost
effectively penetrate close to th e customer, and
VDSL
technology for transmission over twisted copper pairs. The system concept is vali-
dated i n field trials in Denmark, Portugal, and Poland. The article describes the d iffere nt requirements f or a full-service access network,
the system concept, and technologies developed. Results from modeling of broadband traffic and the corresponding bandw idth are
given The cost effectiveness of using new o ptical fiber vs. reusing existing telepho ne copper p lant has been evaluated, and results fro m
these studies are presented.
Niels Engell Andersen, DSC Comm unic at ions AIS
Paul0 M . N, Nordeste, Portu gal Telecom-CET
A. Man uel d e Ol ive i ra Duarte , Univers idade de Aveiro
Hans Erik Lassen, TeleDanmark
And ers Ekblad, Tel ia
Andrze j
R.
Pach, University
of
Krakow
Krzys zto Am bors ki, Telekom unik acja Polska TPSA)
Lars Di t tm ann, EM1
o support economica rlevelopment across Europe, there is
T
need to advance the availability and decrease the cost of
both basic and enhanced telecommunication services.To facili-
tate this, the European Union
(EU)
has initiated a process of
deregulation and a general opening up of the public telephony
network. While there are many network design options avail-
able, the EU’s program for Advanced Communications Tech-
nologies and Services (ACTS)
[
11 in cooperation with other
organizations has funded a project to evaluate and recommend
strategies for access network deployment, designs of a full-ser-
vice access network, and the economic balance between deploy-
ment of new fiber in the access network and reuse of the
existing copper infrastructure. This project started in Septem-
ber 1995 and is planned to conclude by the end of
1998.
The Broadbandloop (BBL) project1 will define and demon-
strate, in live field trials, a concept for
a
full-service access
network which migrates fiber gracefully into the local loop
when bandwidth demand increases. The services offered will
target two customer groups: small t o medium-sized businesses
and residential customers. BBL supports the needs of network
operators to provide both narrowband and broadband ser-
Partners
n
the Broadbandloop project are DSC Commun ications, Por-
tugal Telecom -CET , Universidade de Aveiro, TeleDanmark, Telia Uni-
versity o Mining and Metallurgy in Krakow, and Telekomunikacja P olska.
vices, such as high-speed Internet access and video on
demand , which ar e economically justified in a competitive
environment. The field trial sites, located in Denmark, Portu-
gal, and Poland, have been purposely selected to enable anal-
ysis of typical problems which may be e ncoun tere d when
legacy networks, such as those using existing copper andlor
coax for broadband access or those with little or old telephony
infrastructures, are expanded for new service.
BBL is a near-term project with the aim of developing and
testing technologies which will be ready for mass deployment
within the next three years. The system scheduled for deploy-
ment uses
a
hybrid fiber-copper concept based on a combina-
tion of
a
passive op tical network (PON)
and
very high-rate
digital subscriber line (VDSL) technology. The PON provides
the low-cost fiber acccss, while VDSL providcs the high-speed
transmission to t he custome r over a final short length of
unshielded twisted pair copper or coax. PONs have until now
not
been widely accepted for commercial deployment. BBL is
addressing som e of t he key issues to pr omote the use of
PONs
such
as
integration into the standardized synchronous
digital hierarchy (SDH) network, operational stability, upgrad-
ing of bandwidth, and flexibility to provide protected routing
and allow multiple services.
This article will present t he BBL system concept , traffic
modeling and bandwidth requirements, optical design, techni-
cal and economic evaluations, and plans for the field trials.
0163-6804/97/ 10.00 997 IEEE IEEE Communications Magazine December 1997
Authorized licensed use limited to: UNIVERSIDADE DE AVEIRO. Downloaded on June 16, 2009 at 10:48 from IEEE Xplore. Restrictions apply.
7/18/2019 Andersen Duarte Et Ali IEEE ComMag 1997
http://slidepdf.com/reader/full/andersen-duarte-et-ali-ieee-commag-1997 2/6
..
....
_...
. -
I
i
i
i
i
OLT:
Optical l ine terminal
ONU: Optical network unit
SIM: Subscriber interface module
NT: Network terminat io n
ODN: Optical distr ibu t ion network
SDH
ring (STM-1 or STM-4)
Single business custome r
Voice1
2 Mb/s
I
ult ipl e residentiallsmall business customers
(reuse of existing copper in customer drop )
i
ultip le VDSL cards
~
Passive
split ter
Mu ltipl e residentiaVsmall business customers
OLT (new network)
E l
POTS,
ATM-25,
t Ether net cards
n x 5 1
Mbl;
--..
n
x 51 Mbls
. -...
W Figure 1. TheBBL system concept.
BBL CONCEPT
egacy network operators in western Europe will require a
L roadband system which provides services as an overlay to
the existing telephony or cable television (CATV) network. If
the existing copper resources need replacement or are insuffi-
cient, narrowband services should also be made available
through the new broadband system.
Network operators without a copper network or with a net-
work with low penetration will require a system for both nar -
rowband and broadband services from the outset. An example
of such a network with low penetrat ion is Poland. In general,
the existing copper access network plant in Poland has a low
penetration of about
20
percent with higher penetration found
only in large cities. The services required initially are plain old
telephony service (POTS), Internet access, and local area net-
work (LAN)-t o-LAN interconnect ions with evolution to
broadband services. Therefore, the new access network must
provide basic narrowband services at low cost and be upgrad-
able to provide full broadband services in the future. Since the
new infrastructure must be established for both narrowband
and broadband service, it favors deployment of fiber deeper
into the access network.
A
common requirement for both applications of the system
is that it must integrate synchronous and asynchronous ser-
vices. For economy the system must be designed for sharing
of resources in an environment where customer penetration is
low. Active electronics in the field must be kept at a mini-
mum. This favors the PON with long feeder length and wide
coverage. Some customers require protected routing which
the system must therefore be able to provide on an individual
basis according to demand.
The BBL network topology is shown in Fig. 1.This system is
based on a single fiber PON architecture [2] with a splitting
ratio of up to 16. The bandwidth capacity of the PON is 155
-..
.
Mbls bidirectionally in the basic version which can be gracefully
extended to provide 1Gb/s in the downstream direction and
576 Mb/s in the upstream direction. The PON consists of the
optical line terminal (OLT), a single fiber optical distribution
network (ODN), and up to 16 optical network units (ONUs) per
link. Multiple links are connected to a single subrack system. Cus-
tomers are connected directly to the ONUs or use a VDSL
modem in the final drop, depending on the application.
The BBL PON effectively integrates transport of syn-
chronous and asynchronous traffic in t he access network.
The switched network will continue to be a separate narrow-
band and asynchronous transfer mode (ATM) based broad-
band infrastructure for many years to come. Therefore,
separation and grooming of the synchronous and asyn-
chronous traffic is performed at the OLT at the access node.
In its simplest form, the OLT is a single module forming an
integrated part of the SDH network. Standard
S D H
virtual
contai ners with a 2
M bls
payload (VC12) are dropped
through the PON to the ONU. The ONU provides I nterna-
tional Telecommunication Union (1TU)-compliant
G.703/G.704 connections to a primary rate multiplexer with
narrowband service interfaces such
as
POTS or data line
cards. When cell-based broadband services arc requi red, an
ATM crossconnect module is installed in the OLT and ATM
service modules are installed in the ONUs.
n
important factor in addition to the requirements for low
initial installation and operational cost is the graceful migration
of the network as bandwidth demand increases. The BBL pro-
ject is pioneering subcarrier multiplexing technology applied
to PONs. This technology provides for a selective upgrade
path for customers requesting the upgrade and a robust, sim-
ple, bandwidth-efficient system which meets the requirements
for future commercial PONs. The subcarrier multiplexing con-
cept is explained in more detail in the fourth section.
The design and physical location of t he O NU is of key
IEEE
Communications Magazine December 1997
9
Authorized licensed use limited to: UNIVERSIDADE DE AVEIRO. Downloaded on June 16, 2009 at 10:48 from IEEE Xplore. Restrictions apply.
7/18/2019 Andersen Duarte Et Ali IEEE ComMag 1997
http://slidepdf.com/reader/full/andersen-duarte-et-ali-ieee-commag-1997 3/6
importance in obtaining a cost-
effective network. The different
ONU designs depicted in
Fig.
1
are all compact and versatile. The
ONUS illustrated are optimized for
the three scenarios of: new net-
works for business customer offices
where fiber is extended to the cus-
tomer premises; for broadband
upgrade of copper networks with
VDSL modems; and for new net-
works where installation in a
building is preferred. The ONU
provides a combination of inter-
faces and is shared by many cus-
tomers. The
ONU
design for
outdoor applications is made such
that expensive installation of new
street cabinets can be avoided if
buildings are not available. The
field trials have beeg designed to
demonstrate the features of these
scenarios.
VDSL modems are used to
connect the customers to the
Figure
2 . Bandwidth related tograde of service.
ON U via existing copper twisted pair s o r coax used for
CATV distribution. The bandwidth from t he O NU to the
customer varies between 12 Mbls and 51 Mb/s depending on
transmission distances, which range from
300
to 1500 m. In
the opposite direction of transmission; capacity varies
between 1.6 Mbls and 26 Mbls. Therefor e, cust omers
requesting high bandwidth have the ONU located close to or
at their premises, while customers requesting lower band-
width are connected through an ONU located more centrally
in the network where the cost of the ONU is shared by more
customers.
The frequency spectrum for VDSL [3] is designed such
that POTS or basic rate integrated services digital network
(BR-IS DN) may be provided on the same copper pair.
POTS or BR-ISDN users may be connected via passive fil-
ters between the O NU and customer. The initial version of
VDSL used in
BBL
is based on carrierless amplitude and
phase (CAP) modulation in the downstream direction and
quadrature phase shift keying (QPSK) modulation in the
upstream direction. This technology provides the lowest
cost and earliest commercial availability. The VDSL fre-
quency spectrum is limited to 30 MHz and permits VDSL
to
be combined with an analog CATV distribution system
on coax.
The selected broadband service interfaces for the customer
are ATM-25 and Ether net. ATM-25 provides transp arent
ATM transport to the customer premises equipment and is
recommended by the Full Service Access Network (FSAN)
group [4] Ethernet is widely available in personal computers
today and therefore allows for faster take-up of high-speed
Internet access.
he broa
video on demand (VOD) and high-speed Internet
access. To accurately estimate the correlation between
bandwidth demand on the system and the service quality
seen by the residential customers, the BBL project consor-
tium has developed a computer model and performed traf-
fic simulations to determine t he
project ed gra de of service
offered.
NETWORKODEL
A computer model based
on
the
ATM network depicted in Fig. 1
was used to est imate the band-
width demand to serve an area
with up to
500
residential cus-
tomers. The initial assumption
about services was that residen-
tial customers in the area would
receive VOD and high-speed
Interne t access. The VO D ser-
vice is assumed to be variable bit
rate and the Internet service to
be unspecified bit rate where no
service guarantee is given. Traf-
fic for residential customers will
mainly occur in the downstream
direction fro m network t o cus-
tomer. Upstream traffic consists
mainly of commands from t he
users
e . g . ,
to reauest a film or
download a file). Bandwidth requGementsL[5] of t he new
downstream services are expected to be megabits per sec-
ond. In the downstream direction the V OD peak bit rat e
and mean bit rate used are 6 and 4 Mbls. Internet access bit
rates used are 2 and 0.128 Mb/s. The VOD bandwidth val-
ues assume that Motion Picture Experts Gr oup type
2
(MPEG-2) coding is used. The allocation of upstream band-
width is assumed to be 128 kbls for the peak and mean rates
for both residential services.
NETWORK
IMENSIONING
The global bandwidth was est imated for the BBL network
with calculations based on varying values for service penetra-
tion (SP) (i.e., the population of users with access to the ser-
vices), as well as varying grade of service which quantifies the
probability that a given connection request finds all the net-
work resources occupied and therefore does not succeed. The
grade of service was calculated using the Erlang loss formula
[ 6] .The offered traffic for VOD and Internet access services
is (A
=
500*SP*BHCA*HT)based on the pair BHCA:
busy
hour call attempts, HT: holding time)
and is chosen to be
(0.03,
2 hr) and (0.2,
1
hr), respectively.
Figure 2 gives the estimated downstream bandwidth for the
VOD and Internet services for service penetrations of 5 and
50
percent (from a maximum Qf 500 potential users in the
area). Peak rate allocations only are shown for simplicity rea-
sons. The grade of service is varied and shown in a log scale.
As an example, the variable Internetjeak (5 percent penetra-
tion) gives the estimated bandwidth for the Internet service in
the downstream direction for a peak rate allocation and 5 per-
cent
SP.
Figure 2 indicates that even for reasonably high ser-
vice penetrations the bandwidth requirement remains
moderate. The bandwidth variation with varying grade of ser-
vice is demonstrated to be relatively small.
The results of the model have helped to determine the
estimated bandwidth requirements and grade of service for an
ONU having a number x
=
1,
...,
32) of users. An ON U
providing the VOD service would require, for a grade of ser-
vice = 10 percent, between
6
Mbls and 24 Mbls in the down-
stream direction. The bandwidth estimation for the ONU is
based on the different number of users given above and a
peak rate allocation.
9
IEEE
Communications
Magazine *
December 1997
Authorized licensed use limited to: UNIVERSIDADE DE AVEIRO. Downloaded on June 16, 2009 at 10:48 from IEEE Xplore. Restrictions apply.
7/18/2019 Andersen Duarte Et Ali IEEE ComMag 1997
http://slidepdf.com/reader/full/andersen-duarte-et-ali-ieee-commag-1997 4/6
OPTICAL RANSPORT
YSTEM
\
I
/
he optical transport system between the OL T and the
TONUs must
be
designed to accommodate both narrow-
band and broadband services, and circuit-based and packet
traffic over a point-to-multipoint PON. Infrastructure cost
must be kept low and closely connected to th e service
requirements. New network deployments will ofte n be
based on narrowband POTS with initial low penetration.
The networ k must be cost-effective in this scenario but
upgradable as the demand for services increases. The
upgrade must be accomplished with a minimum of, prefer-
ably no, disruption to customer service. The bandwidth effi-
ciency, which is the ratio between the bandwidth required
for transportation of the payload (including overheads) and
the available bandwidth, must be high. To keep the installa-
tion and maintenance costs low, the system must be simple
and insensitive to the performance of the optical network
in the outside plant.
MULTIPLEXING
In BBL, subcarrier multiple access (SCMA) technology
[7]
has been chosen as the method to transmit from individual
ONUs to the OLT (multipoint-to-point) direction. With
SCMA one or more electrical subcarriers are assigned to each
ONU. In t he OLT th e traffic from the individual ONU s is
selected via electrical filters. SCMA has been proven to be
robust and simple in operational field trials [7,
81.
It allows
optimization of the ONU, with respect to processing power
and operational speed, in line with the capacity of the individ-
ual subcarrier, not the entire PON bandwidth. Additionally,
SCMA eliminates the ranging issues commonly found in time-
division-multiple-access-based PON systems. This issue is par-
ticularly important when protected redundant routing must be
provided. SCMA allows for fast resynchronization in case of
switchover to an alternative route.
The basic optical system provides a total of 9.72 Mb/s of
upstream capacity on a narrowband subcarrier for each ONU.
In addition, a subcarrier-based bandwidth upgrade will be
demonstrated providing extra upstream capacity of
51
Mb/s
on a broadband subcarrier per ONU. In th e direction from
the OLT t o the ONU , broadcast baseband transmission is
chosen for the basic system with a transmission speed of 155
Mb/s. Upgrade to higher bandwidths will also
be
possible
through the addition of extra subcarriers, each with a capacity
of 51 Mb/s. This will allow capacity upgrade on a selective
basis without widening the operating window of all ONUs.
Figure 3 illustrates the principle of carriers with different
capacity terminat ed in ei ther narrowband or broadband
ONUs. Broadband subcarriers can be added on an individual
basis without interrupting service from other ONUs. The
SCMA technology also allows ONUs to be connected and dis-
I
OLT
I
Year
OLT I-&-
Customers
f t b
SDH>
Customers
I
-. .
~. i
W
Figure 3
Illustration of broadband upgrade
of
an
ONU
and
insertion o
a
new ONU
in
an operating
PON
connected from the optical distribution network without dis-
turbing other ONUs.
ATM has been selected as the key multiplexing technique
for broadband service transmission in the time domain trans-
ported within different subcarriers. The use of ATM provides
the flexibility required for full-service integrat ion. It enables
both static time-division multiplexing (TDM), via an emula-
tion protocol, and sta tistical multiplexing, which will make
low-cost data communication possible for applications such as
residential user connectivity over the Internet.
OPTICAL ESIGN ONSIDERATIONS
The BBL PON benefits from single-fiber working. This is
fast becoming a network operato r preference, since it saves
on optica l fiber outlay and hence simplifies fiber handling.
Loo p length s below 20
km
are considered, and optical
amplifiers will not be us ed in t he system. Optical wave-
length-division multiplexing (WDM) provides a clear sepa-
ration of downstream and upst ream transmissions, which
are carried on 1550 and 1310 nm, respectively. This enables
reuse of electrical frequency bands in bot h transmission
directions. The required laser modulation bandwidth is
therefore reduced, which enables low-cost laser technology
to be used.
In BBL the key optical component is an integra ted optical
transceiver containing a Fabry-Perot laser diode, a PIN photodi-
ode, and an optical WDM to separate 1550 and 1310 nm chan-
nels. Furthermore, an additional optical filter is incorporated to
keep optical crosstalk as low as
-50
dB. The O NU opto-
transceiver is a commercially available
component developed for digital appli-
cations, enabling the BBL system to
benefit from its low mice.
~
i
- - -
As indicated in Fig. 4 the BBL sys-
. .
6
'
tem is based on SCMA. Downstream
every ONU accesses an STM-1 base-
band signal on a TDM basis and may
furthermore have access
to
a broad-
band subcarrier channel. Upstream a
Optics based on Optics based on narrowband or broadband subcarrier
is allocated to each ONU . All chan-
nels are designed, with regard to
i
.
power budgets, to meet a bit error
Figure 4.
BBL PON based
on
subcarrier upgrade both up- and downstream
by tak-
ONU I
:
t
optotransceiver
iscrete elements
rate which is better than
IEEE Communications Magazine
December
1997
91
Authorized licensed use limited to: UNIVERSIDADE DE AVEIRO. Downloaded on June 16, 2009 at 10:48 from IEEE Xplore. Restrictions apply.
7/18/2019 Andersen Duarte Et Ali IEEE ComMag 1997
http://slidepdf.com/reader/full/andersen-duarte-et-ali-ieee-commag-1997 5/6
ing into account link losses in the interval
10-25 dB and at the same time obtaining
sufficient signal-to-noise ratios, when con-
sidering the relative intensity noise (RIN),
shot noise, thermal noise, and optical
beat noise (see below). In addition, a 3
dB implementation margin is incorporat-
ed. In order to limit the t otal bandwidth
capacity in the system an efficient
1
Hz/l
b/s modulation scheme is used for all
sub-
carrier channels.
In a multicarrier system, with a total
frequency plan covering more than one
octave, ONU laser nonlinearity must be
kept below a certain level because inter-
modulation products within information
bands cannot be avoided. To ensure low
intermodulation distortion arising from
laser modulation, the lasers are not mod-
ulated near their threshold currents. This
complicates the equalization of the sub-
carriers at the OLT, but is necessary to
obtain a dense subcarrier frequency plan,
limit the total bandwidth, and avoid chan-
nel interference. The
ONU
transmitter is
Cusl;mer
ccess
point Flcxiblity po int
1
Flexibility point 2
2. PON 1:16)+
VDSL
(Downstrmm26 M ~ / s
:FON 1:16)+
VDil
(Dowrstieam SI Mb/s
I:?st:?xn
1.6
MWs)
4: ?ON 1: 6
i
I
5: PON (~5 4
Access point Typidy ?
OC0 to
i O i j 0 0 hotrie5
pzss.-tl
1 3CO i r i fr:m i:icLo*:irr
Flexibility point
l : - p ~ ~ ~ ~ ~ ~
00 to 200 huinrs pi,ved:
500 in
froi:i r.u>.oin?r
Flexibility point 2:
Tyypice
~v
io
60
homes p e , s d I n n
71
iorri CUST071211
STM: STMI interfacc to core
SDH
inemul-k
A- M: ATM ciosrco me3
ADSL: Asymmetric diyit al s ubsci ilrr line
VDSL Veiy high-rat? digiidl 5ubscrii-;dr L i?
OLM: Optical line nodde
ONM: Optical network inodul?
ATM25:
ATM
UN1 with
25
Mbs trdiistrii>sirin 6 I e
-
-. ..
W
Figure
5 . ife cycle cost scenarios.
able to automatically adapt to a differential link loss of 15
dB in the PON. This is achieved through a number of mech-
anisms, one of which involves keeping the mean laser optical
output power inversely adjusted
to
the mean received optical
power. However, the 15 dB dynamic range cannot be cov-
ered solely in the DC domain without modulating the laser
close to threshold. Consequently, regulation of the modula-
tion index is included in the equalization process to obtain
the required dynamic range.
When designing a laser driver, cost and power consump-
tion can be reduced by avoiding the use of Peltier coolers to
maintain constant laser temperature. Consequently, the design
of the BBL ONU has allowed for lasers with fluctuating tem-
perature and hence varying light current characteristics. The
driver automatically adapts
to
temperature changes by use of
an onboard temperature sensor.
In subcarrier multiple access systems the headend receiver
is simultaneously illuminated by n optical signals. The noise
level experienced by an individual channel is affected by the
RIN from all the ONU lasers. This is due to the fact that the
RIN level in the OLT receiver depends on the total incoming
light level, and high RIN levels could potentially limit the sys-
tem performance. The laser in the transceiver has been char-
acterized with respect to RIN to verify that the bit error rate
can be kept below the design level even at worst-case combi-
nation of the link losses.
Subcarrier multiple access PONS potentially suffer from
optical beat noise that may degrade the optical transmission
performance. Opt ica l
bea t
noise arises when the optical
spectra of two or more lasers, illuminating the OLT optical
receiver, overlap. The level of optical beat noise depends on
the distribution of the optical wavelengths of the ONU
lasers; consequently, the optical beat noise level fluctuates
with time and temperature. This can lead to a momentary
increase of bit error rate. The PON system is designed to be
resilient
to
this phenomenon. The optical beat noise level is
supervised at the OLT, and in case of an increased level the
wavelengths of a number of ONU lasers will be fractionally
adjusted under the control of embedded software, until an
acceptable noise level is reestablished. By this control
method the bit error rate is kept below the design level
given above.
TECHNICALCONOMIC COMPARISON
OF
DEPLOY
ENT SCHEMES
ife-cycle cost studies in the BBL project have compared the
6 ost for deployment of five different access networks over a
span of 10 years assuming a certain development in service
demand and number of customers connected to the system.
Customers are predominantly residential. The life-cycle cost
includes accumulated investment and operation, maintenance,
and administration costs.
The assumption behind the study was that a telephone net-
work with a penetration
of 95
percent would be available. It was
also assumed that the number of customers connected to broad-
band services would increase linearly from none at the beginning
of year
0
to a penetration of either
20
or 40 percent connected
after 10 years. The five scenarios (Fig. 5) compared were:
1 Asynchronous DSL (ADSL) from the access point to the
customer.
2) PON with split ratio 1:16 from the access point
to
flexibility
point 1and VDSL from flexibility point 1 o the customer
3)
PON with split ratio 1:16 from the access point to flexibility
point 2 and VDSL from flexibility point 2 to the customer
4)PO N with split ratio 1:16 from the access point to the
customer
5)PON with split ratio 1: 64 from the access point to the
customer
The ADSL technology has the advantage that existing cop-
per can be used from the access point to the customer; there-
fore, for initial broadband service deployment fiber is n o t
required. However, the bandwidth may not be sufficient for
future demand.
With the assumptions made about relatively
low
bandwidth
requirements and customer penetration evolving to 20 per-
cent, the most cost-effective method is scenario
1.
For this
application, ADSL will require very little new investment in
infrastructure. If the number of customers connected
to
the
network increases to 40 percent, the difference between sce-
nario 1 and scenario 2 is .relatively small when viewed over 10
years. Scenario 5 showed a marginally lower cost than sce-
nario 4. However, a splitting ratio of 1:64 would limit the flex-
ibility of the network design.
92
IEEE Communicat ions
Magazine December
1997
Authorized licensed use limited to: UNIVERSIDADE DE AVEIRO. Downloaded on June 16, 2009 at 10:48 from IEEE Xplore. Restrictions apply.
7/18/2019 Andersen Duarte Et Ali IEEE ComMag 1997
http://slidepdf.com/reader/full/andersen-duarte-et-ali-ieee-commag-1997 6/6
The choice of scenario will depend on expectations for devel-
opment in services. Providing severalT V channels simultaneous-
ly, for instance, may require the bandwidth
VDSL
can provide.
An operator may also,
for
strategic reasons, want to penetrate
fiber deeper into the access network for future growth.
Civil engineering work and installation of cabinets and
powering contributes the most significant portion of first
installed cost in all cases. It was found that the cost for churn
(connection and disconnection
of
customers) also contributed
significantly to the cost over 10 years. Centralized manage-
ment is expected to reduce life-cycle cost in favor of scenario
4 and scenario 5.
A similar study was performed for a residential ar ea in
Poland where li ttle existing telephony infrast ructure exists.
The results from this study show that the fiber-intensive sce-
narios 3 and 4 provide the lowest costs when considering the
increasing broadband service demand assumed for the west-
ern European partners.
FIELD
TRIALS
nstalling and evaluating trials in three different countries
IPoland, Denmark, and Portugal -will give important infor-
mation about actual availability of existing network resources
for broadband transmission and design of access networks for
implementation as an overlay to legacy networks and for
installation in green field areas. A field trial installed in
Aveiro, Portugal, in
1995
by the RACE project FIRST
[7 81
demonstrated the design of a simple, low-cost, robust P O N
system. This was based on subcarrier multiplexing technology
for upstream transmission between the ONUSand the OLT.
This trial is still in operation, providing
50
users with narrow-
band services.
The new trials under ACTS will evaluate the trade-off
between the use of optical technologies and of VDSL over coax
or twisted pairs. The objective is to demonstrate that PONs can
provide
a
low-cost entry solution which evolves as bandwidth
demand increases by evaluating the cost of fiber deployment
versus that of upgrading the existing copper network. Opera-
tional issues to be studied are the number of cable pairs that
can be used for broadban d transmission, range of
VDSL,
influence of cable age, influence of external noise, and t he
electromagnetic emission problems
VDSL
may cause.
Results expected from the trials will generate dimensioning
rules for the access network, informat ion about optimal
design of hybrid access networks, and improved definition and
understanding of usage profiles for broadband services.
CONCLUSION
n this article we discuss what we consider t o be t he most
l
mportant issues for evolution to a broadband access network
and how the Broadbandloop project is supporting the evolution.
The preliminary conclusions are that upgrade of the old copper
network to provide broadband transmission is a viable strategy
in the near term. The PON is cost effective in greenfield areas
and must provide low-cost telephony and evolution capability
to broadband services. The Broadbandloop project is develop-
ing and demonstrating new optical technologies which are
improving reliability and cost effectiveness of PONs.
ACKNOWLEDGMENTS
We would like to acknowledge the ACTS program and th e
parent organizations involved in the project for their support
in terms of funding, technologies, infrastructure, network
users, and logistics, which all together make it possible
to
carry out the Broadbandloop project.
RE ERENCES
[
]
Europe an Com mission, ”ACTS ’96, Advanced Communications Technolo-
gies and Services, Project Summaries,” Sept. 1996.
[2] N. E. Andersen, “Optimising Access Network Architectures, Comparing
PONS w it h Alternat ive Techno logies,” I IR Conf. , Londo n, U.K., July
[3]G. T. Hawley, ”System Co nsiderations fo r the Use of xDSL Technolog y for
Data Access,”
/€E€
Commun., vol.
35,
no.
3,
Mar.
1997,
pp.
56-60.
[41 ”Full
Service Access Network-GX, Network Termination-Home Network,
Functional requirements,“ 8th Int‘l. Wksp. OpticaVHybrid Access Net-
works, Atlanta, CA, Mar.
1997.
[5] E. Jaunart a nd P. Crahay, “ATM Super PON Dimensioning for Future
Resident ial and Business Demand,” Broa dba nd Superhighwa y, D. W.
Faulkner and A. L. Harmer, Eds., EFOVLAN
1996.
[61
H. Saito, Teletraffic Technologies
in A T M
Networks, Artech House, 1994.
[7] D. E. A. Clarke,
R.
Mudhar, and A. Purser,” A European Initiative Lead-
in g towa rds a Practical Customer Access Link Using Fibre,” BT Tech.
J.
vol. 11, no. 1 Jan. 1993.
[8]
P. Woolnough BTetal. , RACE
R2014
FIRST, del.
1011,
”Final Studies,
Evaluat ion and Recom mendations (contact Niels Engell Andersen a t e-
mail address below for a copy).
15-1 6, 1996.
BIOGRAPHIES
NIELS NGELL [email protected]) received an M.Sc. degree from
Georgia Inst itute of Technology in
1978. He
has worked for dif ferent pri-
vate companies ondevelopment and implementat ion o f advanced cont ro l
and comm unications systems. Since
1989
he has been wit h DSC Communi-
cat ions
A S
(formerly NKT Elektronik), whe re he
is
manager for develop-
me nt of access technologies and field trials.
PAULO
M. N. [email protected]) received an M.
Sc.
degree from Essex
University in electrical engineering in 1980 and CEPAC from Universite‘ Libre
de Bruxelles in
1989.
He has been head o f th e Traffic Engineering Department
at CET in Aveiro and m embe r of scientific sta ff in DGXIII-F in the European
Union. He
is
a m ember of the board o f MEGASIS, president of the General
Assembly of th e Portug uese Electrotechnical Institu te (IEP), representative of
Portugal Telecom in the General Assembly of Eurescom, and membe r o f the
board of INESCTEL.
A. MANUELE OLIVEIRA [email protected]) received a “Licen-
ciatura” degree in electrical engineering fro m th e University o f Coimbra in
1976, and M.Sc. and Ph.D. degrees in telecomm unica t ions systems and
electrical engine ering sciences, respect ively, in 1981 and 1984 f r o m t h e
University
of
Essex, U.K. He joine d t he University o f Aveiro
in 1978
were he
i s
n o w a n a s s o ci a te p r o f e s s o r i n t h e D e p a r t m e n t of Elec t ron i cs and
Telecommunications.
HANS
RIK
LASSEN eceived ([email protected]) M.Sc. and Ph.D. degrees from the
Electromagnetics Inst itute at the Technical University of Denmark in 1984
and 1991, respectively. From 1986 t o 1988 he was assistant professor with
the Electromagnetics Institute. From
1988
he has been with Tele Danma rk
Research
ANOERS
KBLAO
(anders.l .ekblad@tel ia.se) received his Master’s degree in
electrical engineering fr om Chalmers University of Technology, Gothen burg,
Sweden,
in 1988.
He has been employed at the Networks Division of Telia
AB since
1988.He
is no w engaged in Telia’s strategic dev elopme nt of the
broadband access netwo rk . In former pos i t ions he was engaged in the
development o f opt ical f iber cables and ou ts ide plant in which he holds
several pa tents.
ANDRZEJ. PACH ([email protected]) received an M.S. degree in electrical
engineering and a Ph.D. degree in telecommunications fro m the University
of
Mini ng and M etallurgy, Cracow, Poland, in 1976 and 1979, respectively, and
a Ph.D. Hab. in telecommunicat ions and compu ter networks from the War-
saw University of Technology in
1989.
In
1979,
he joined the Telecommuni-
cations Department at the University of Mining and Metallurgy, where he
is
currently a professor.
[email protected]. tpsa.pl) received an M.Sc.degree from
Warsaw Technical Univers i ty in te lecommun icat ion in
1964,
an M. A. i n
1971 f rom the Univers ity of Warsaw in mathematics, and a Ph.D. in 1972
fro m Warsaw Technical University. Since 1965 he has been assistant profes-
sor at W arsaw Technical University. In
1994 he
was appointed
expert for
Telekomunikacja Polska S.A.
[email protected]) (MSc. 1988, Ph.D. 1995) s assistant profes-
sor at th e Cen ter for B roadband Telecommunications (CBT/EMI) at th e Tech-
nical Univers i ty of Denmark wi th respons ib i l i t y for ATM swi tching and
netw orkin g activities. His current interest is resource management, and the
implications for network design and requirements for network elements.
IEEE
Communications Magazine Decem ber 1997
9