Int. J. Communications, Network and System Sciences, 2011, 4, 756-760
doi:10.4236/ijcns.2011.411093 Published Online November 2011 (http ://
Copyright © 2011 SciRes. IJCNS
Performance and Capacity Planning of NGN
Mustafa Shakir, Mahmood Ashraf Khan, Shahzad A. Malik, Izhar ul Haq
Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad, Pakistan
Received September 12, 2011; revised October 14, 2011; accepted October 22, 2011
There have been various emerging trends in the deployment of telecom networks recently. Due to liberaliza-
tion and technological advancements a common core network for voice and data based on MPLS has been
implemented by Telecom service providers. By offering a variety of data and multimedia services, the reve-
nue generating process can also be maximized. The economic and regulation trends also have to be synchro-
nized for the proper and step by step replacement of traditional network by NGN. The current flow is to pro-
vide users with multitude of services thus meeting their high demands and enhancing revenues for network
operators. Class 5 and Class 4 are our legacy circuit switches based upon TDM to transport voice. For han-
dling control functions, call setup and teardown SS7 signaling was used. The traditional network was de-
signed to support voice services only not being able to meet customers’ demands who require a variety of
services at an optimum cost. The aim of this work is to present the role of NGN encompassing the telecom
network, architecture and technologies. Also it has emerged as a new platform to decrease the CAPEX and
OPEX of overall network infrastructure and to maximize their revenues. In this paper, we present an upcom-
ing architecture for the transition to NGN which is future proof for going through the migration phase along
with the capacity and planning of our network.
Keywords: Next Generation Network, Convergence, MSAN, Softswitch, FTTH
1. Introduction
There is a changed trend of adoption of packet switched
networks from circuit switched networks. The scope of
services to be provided to the users can be widened thus
availability of anytime anywhere access for satisfying
customers and meeting the enhanced demands [1]. Most
service operators are targeting NGN in view of market
demands and IP would be the core network.
The ITU defines the Next Generation Network as a
packet based network able to provide services and make
use of multiple broadband, QoS enabled transport tech-
nologies in which service related functions are inde-
pendent of underlying transport related technologies [2].
The access is common to all and different network op-
erators are integrated at the access layer. NGN also pro-
vides ubiquitousness and mobility to its subscribers.
NGN has a hierarchical four layered architecture which
due to its nature can be able to support additional ser-
vices. It is a packet based network which provides effi-
cient networking features in addition to supporting new
services through open interfaces. NGN also has separate
application and network layers thus providing the room
to further improve services. Third parties can also con-
tribute to development of application applications for
subscribers. With transition to IP networks the average
per line costs of increasing networks could increase
leading to deteriorated QoS. In Section 2, we would go
through the ex isting trends followed by serv ice providers.
In Section 3 the implementation of MSAN and switch up
gradation is described. Capacity planning amongst the
NGN elements is discussed in Section 4. Finally we con-
clude our observations in Section 5.
2. Switching Approach by Network
The telecom service providers have to take into consid-
eration the high expectations such as Broadband and
Multimedia services for customers’ satisfaction. The
equipments for switching and access would have to be
upgraded and replaced so as to promote the convergence
trend. The standardization bodies throughout the world
have worked on the protocols and general architecture
for the advanced networking aspects in new approach.
The new architecture would support not only existing
telecom infrastructures but would also ensure a smooth
transition to an ip based network. British Telecom and
SingTel are adopting the converged approach thus im-
plementing a single multi-service network [3]. Various
operators are working upon implementation of NGN in
their core networks. The operators would pursue a
phased approach towards upgrading to the corresponding
NGN components while providing the services of tradi-
tional network at the same time. The NGN setup is
shown in Figure 1. The softswitch (SS) provides call
control services as well as Media Gateway control since
it handles many switching functions and has replaced the
traditional switch. The Trunk Gateway (TGW) and Ac-
cess Gateway (AGW) are controlled by the softswitch
and act as the interface between circuit and packet
switched networks converting ip to TDM traffic and
TDM traffic to ip. The Application Server (AS) provides
enhanced features which are not available in the
softswitch. A protocol used to control call setup, connec-
tion and termination. The call control protocols used in
softswitch are SS7 for switched circuit network, whereas
SIP and H.323 are implemented for call control in packet
switched networks. The softswitch controls media gate-
ways by means of MGCP. The SIGTRAN (Signaling
Transport) protocol carries SS7 signals over the internet.
The immediate and one step conversion of existing net-
works to NGN would not b e possible so it has to be exe-
cuted in a proper way. At the core IP network shown in
Figure, IP based components would be implemented
which would realize a MPLS approach and multimedia
services would have to be provided thus achieving our
targets of Fixed Mobile Converg ence [4].
The network operators divide their traditional infra-
structure into region s or domains as per the requirements
of operation and maintenance, traffic engineering and
distribution and the buildup of sites in various areas. The
network can be seen as comprising of a number of do-
mains while we realize the NGN solution for switching
i.e. the Soft Switch. Our IP based network at the core
would be able to provide a better QoS and processing a
capability to handle a large number of subscribers. The
softswitch serves as the central device in the telecommu-
nications system. The call agent in the soft switch carries
out functions of signaling, billing and services. The Me-
dia Gateway which is controlled by the softswitch acts as
the interface between circuit and packet switched net-
works converting ip to TDM traffic and TDM traffic to
ip. The Signaling Gateway converts PSTN signaling be-
tween TDM bearer mode and IP packets mode and is
applied on the access layer of NGN thus can process
both SIGTRAN and SS7 protocols keeping ahead in sig-
naling link density, capacity and signaling processing
capacity. The access gateway is the line interface to the
core ip network and connects subscribers with analog
Figure 1. NGN approach for switching.
Copyright © 2011 SciRes. IJCNS
Copyright © 2011 SciRes. IJCNS
subscriber access, ISDN and V5 subscriber access. The
service logics and individual service features are imple-
mented on the application server. Interconnection be-
tween Application Server and Media Gateway Co ntroller
is realized using SIP protocol. The nature of NGN as a
result of division into layers provides flexibility, scal-
ability and openness of the converged NGN platform.
3. Multi Service Access Nodes: The
Gateways to NGN
The deployment of networks by different operators would
more or less evolve on the same extent as access tech-
nologies would be the same. The network at the core
level would be ATM/SDH which is used to interconnect
the Class 5 switches to the Class 4 switches of higher
order [5]. This ATM network serves as source of back-
haul broadband services from DSLAMs located at the
CO to ISPs and gateways. The migration to NGN would
be achieved by converting the core network to IP. The
equipment for NGN would replace the legacy switches
as a next step.
Broadband applications would be provided through
FTTH and giving a bandwidth of several Gbps. So the
service providers are upgrading their networks by de-
ploying the MSAN. British Telecom, France Telecom,
Telekon Austria and Belgacom are upgrading their net-
works. The British Telecom has invested a huge amount
of up to $17 billion to upgrade their ex istin g netwo rks. In
Asia, NTT has developed its own Next Generation Net-
work thus providing optical fiber based broadband access
which would deliver a variety of broadband ubiquitous
services. SingTel is adopting the path towards conver-
gence by combining 3G and video services across mobile,
fixed-line an d br oadband pl at fo rms.
3.1. Switch Upgradation
The change in the infrastructure to move on to the new
switching systems would be phase wise thus capacity
requirements could be greater and OSS would be ac-
commodating the new IP infrastructure and data from
traditional legacy systems have to be transferred and
transformed to a new OSS. The BSS (Business Support
System) migration will define the operation and func-
tioning according to the new NGN IP net w o rk .
For the new scenario Class 5 switches and DSLAMs
would be replaced by MSAN equipment (equipped with
POTS, ISDN and DSLAM cards) and these MSANs
would require IP over fiber connections to the core net-
The MSAN cards convert xDSL, POTS and other ser-
vices to IP. Shifting the core networks to IP is an exten-
sive job which would take several years and with new
DSLAM installation these would have to be IP based so
that compatibility can be ensured.
3.2. Using MSAN
The new strategy would be to install MSANs with
DSLAM cards and with the completion of IP core POTS
and other cards can be added to avoid the need for total
MSANs can be fully operational with the all-IP core
when Softswitch is used for call set up and authentication
functions. MSAN would be thus used to provide the
broadband services while other services such as POTS
would be provided over copper. When the IP core is
complete customer lines would need to be transferred
from copper pairs onto MSAN ports. VoIP would be
prevalent as voice, video and data can all be provided as
Triple play application.
3.3. MSAN in the Future
Service providers are opting for FTTH (Fiber to the
Home) in the long term. The step involved in migrating
to FTTH is to convert from active MSANs to passive
Fibre distribution hubs. For each node’s service coverage
area a fiber dig would be needed from each home and
back to node.
There are two options for FTTH/P, the first one being
a passive optical network (PON) using shared fibres,
which are more cost-effective for long CO to node dis-
tances such as in rural lo cations, or a point-to-poin t (P2P)
for metro and urban situations, where every customer has
their own fibre back to the IP-core. Most operators will
need a mix of both.
In case of PON, the MSAN will be replaced with a fi-
bre distribution hub where passive optical splitters com-
bine the light wave signals from 32, 64 or 128 customers
on to a fibre pair back to the IP-core. Alongside this an
optical fibre cross-connection or patching frame (similar
to that we currently have for copper) to provide moves,
adds and changes (MAC) flexibility. For P2P, a lot of
new fibres back to the IP-core need to be blown-in or
dug in. In this case, the fibre distributio n hub only needs
to provide the fib re cross-connection facility.
In both cases, the node or fibre distribution hu b reverts
to being completely passive reducing field maintenance
and associated costs significantly. And, as previously,
this conversion to FTTH/P can be undertaken progres-
sively—either a node at a time or even by placing fibre
distribution hub and MSAN side-by-side in the OSP and
performing a gradual change over as customers are pre-
pared to pay for FTTH/B enabled services. PTCL is the
service provider company in Pakistan It has recognized
the need for migrating its network infrastructure to NGN
platform which can provide services efficiently and cost
effectively to its customers. Thus the migration of PSTN
has to be completed in least possible time and introduc-
ing new and advanced services efficiently so to construct
a unified service platform to meet fixed and mobile cus-
tomer’s requirement in near future for optimal traffic an d
capacity for which the planning has been adopted and
worked out in our paper.
4. Capacity Planning in NGN
The switching process is kept simple and the number of
trunks would be fixed [6]. There is a serious level of de-
pendence on soft switch for which if any problem arises
there might be a large number of services interruptions
and revenue lost besides the possibility of being pun-
ished by the authorities. NGN ad dresses the cost problem
in addition to the deployment of network effectively. In
order to distribute the traffic load evenly we look upon
the scenario in terms of the signaling gateways, media
resource server and the soft switch. As a first step we
have to go for a proper location, the number of network
components of NGN and the link capacity between NGN
elements. We divide the legacy Network in domains thus
deploying the softswitch and a signaling gateway in each
domain. We are also aware that in the NGN system we
would replace the class 4 switches by Trunk Gateway.
Some operators are using the MSAN as an access gate-
way. After identifying the location and nodes the band-
width has to be mentioned for the capacity calculation to
ensure the timely availability of users in order to access
the network.
The traffic intensity generated by each user is equal to
call request completed per unit time multiplied by the
holding time. The traffic intensity generated by each user
in Erlangs is given by
H is average duration of a call and
is average
number of call requests per unit time for each subscriber.
For a system having U subscribers and unspecified
number of channels, the total offered traffic intensity A,
is given as u
In a C channel trunked system, if traffic is equally dis-
tributed among the ch annels, then the traffic inten sity per
channel is denoted as c
which would be mathemati-
cally represented in the relation
Link Capacity, LC1 = Bandwidth allocated amongst 2
Softswitches using SIP-T protocol.
Link Capacity, LC2 = Bandwidth allocated for traffic
between Softswitch and Signaling
Gateway =
× No. of Messages/Call × No. of
Link Capacity, LC3 = Bandwidth allocated for Traffic
between Softswitch and Media Resource Server =
No. of messages/Call × No. of Bytes/Message.
Link Capacity, LC4 = Bandwidth allocated for Traffic
between Softswitch and Trunk Gateway =
× No. of
messages/Call × No. of Bytes/Message.
Some service providers are using MSAN as Access
Gateway so for traffic from Softswitch to MSAN.
Link Capacity, LC5 = Bandwidth allocated for Traffic
between Softswitch and Access Gateway (or MSAN) =
× No. of messages/Call × No. of Bytes/Message.
Link Capacity, LC6 = Bandwidth allocated for Traffic
between Trunk Gateway and IP Core = Total Number of
Trunks × Average Traffic/Trunk × Payload Flow. The
total traffic being A so LC6 = A × Payload Flow.
Hence the overall capacity required between the trunk
gateway and IP core network is dependent upon the
number of trunks managed by each trunk gateway and
the amount of traffic generated by the system subscrib-
5. Conclusions
NGN deployment has been kicked off and service pro-
viders are migrating their networks to NGN. The goal is
to reduce costs of building and operating number of
separate networks so we have emphasized on the soft-
switch to provide solution to migrate the PSTN to NGN.
The network capacity planning is also dependent on the
traffic distribution through softswitch.Voice services are
now becoming less profitable for service providers so
NGN based on IP is a way to bring the operating costs
down thus contributing as a major driving factor for
network operators. Operators would have to adopt IP due
to huge efficiency, capacity and flexibility. So the ser-
vice providers have to promote the delivery of “content”
across the packet switched networks to continue with the
way forward. Video on Demand offering voice, video
and data is the most prioritized service to be provided to
customers. The convergence of telecom and ip networks
is the correct way to create the universal multimedia
NGN. The existing network infrastructure cannot come
up to the demands of the customers so operators have to
provide up to 100 Mbps and above to the subscribers’
premises. Integrating all services on a single Multi Ser-
vice Access Node would be more cost effective stream-
lining the way forward for provision of new services to
customers as quick as possible.
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Copyright © 2011 SciRes. IJCNS
6. References
[1] M. Shakir, “Challenging Issues in NGN Implementation
and Regulation,” 2010 6th International Conference on
Wireless Communications Networking and Mobile Com-
putting, Chengdu, 23-25 September 2010, pp. 1-4.
[2] ITU-T Recommendation Y2001, “General Overview of
NGN,” December 2004.
[3] Sato, “Organising Innovation in Services: The Case of
Telecommunications Next Generation Networks,” First
ITU-T Kaleidoscope Academic Conference of Innovations
in NGN: Future Network and Services, Geneva, 12-13
May 2008, pp. 255-262.
[4] N. Iiyama, H. Shiba, H. Kimura and H. Hadama, “Long
term Cost-Effective Access Network for Fixed Mobile
Convergence,” 2010 15th OptoeElectronics and Commu-
nications Conference, Sapporo, 5-9 July 2010, pp. 426-
[5] C. Storbeck, “Next Generation Networks: The MSAN
Strategy,” Fibresystems Europe Magazine, Boulder, June
[6] A. Amer, “Design and Capacity Planning of Next Gen-
eration Network (NGN),” Proceedings of the Mosharaka
International Conference on Communications, Signals
and Coding, Amman, 17-19 October 2008, pp. 28-34.