This document summarizes the evolution of telecommunications networks from 1G to 5G and the transition to an IP-based network using the IMS framework. It discusses the key technologies and standards used in each generation such as GSM, GPRS, EDGE, LTE. It also covers the evolution of the access, transport and session layers from circuit-switched to packet-switched networks. Finally, it proposes a three-phase approach to migrating an existing softswitch-based VoIP network to an IMS architecture by decomposing functions and introducing new IMS elements.

1. Telecom Study of IP
Transformation
By
Altanai Bisht
tara181989@gmail.com

2. 1 G 2 G 2.5 G 3 G LTE
• SMS (short
messaging
service),
•GPRS, EDGE,
High Speed
Circuit
switched data
was introduced
• Bandwidth of
384 kbps
•High-speed data
transmissions
•Symmetrical and
asymmetrical data
transmission support
•Improved voice quality
•Greater capacity
•Support of global
mobility
•Lack of coverage in
some areas
•Demand for broadband
services in a hand-held
device
•Deployment of LTE
on existing sites
and sharing of
common
infrastructure
•Sharing of
backhauling
equipment
between LTE/SAE
and existing
network
technologies
provided at the
same site
•Common network
management
platforms
•Digital
modulation
• Bandwidth
of 14.4
kbps
•Data Transfer
(only voice)
•No encryption
•Sound quality
is poor
•Speed of
transfer is only
at 9.6kbps
4 G/ 5G
Evolution of Voice in Access Layer
•Higher bandwidth
•Support for global
mobility and service
portability
ubiquitously with
lower cost
•Broadband IP-based
entirely applying
packet switching
method of
transmission with
seamlessly access
convergence

3. ATM
Evolution of Voice in Transport Layer
Frame
Relay
SDH/SONET NG- SDH Metro
Ethernet
ROADM
• Hardware costlier
than the Ethernet
hardware
• Costly for the
data-based
applications
(wastage of
bandwidth)
• Subscribers pay
more for less
required bandwidth
•Cost-effective
•A single box
can handle the
voice, data and
bandwidth
services
•More granular
bandwidths are
available and
subscriber can
enjoy the
flexibility
•Low cost
•Reduces OPEX
and CAPEX by
flexible and
efficient service
provisioning,
service
activation and
OAM functions
•Cost-efficient as
it reduces OPEX
and
CAPEX
significantly for
the largenetworks
•Variable
packet size
•Less
expensive and
upgrading is
easier
•Fixed packet
size
•Convenient for
hardware
implementation
•Cost Higher

4. 4
Evolution of Voice- in Session Layer
IN IMS
•Introduce new services rapidly - IN provides the capability
to provision new services or modify existing services
throughout the network with physical intervention
•Provide service customization - Service providers require
the ability to change the service logic rapidly and efficiently
•Create Open interface - Allows service providers to
introduce network elements quickly for individualized
customer services
•Complex and costly to build and maintain as the number of
services grows
•Services are specified and supported by a single logical
node, or set of nodes, performing specialized tasks for each
specific service. Each service is an island, with its own
service-specific node
•To create and secure interconnect agreements on every
single service an extensive and tedious task
•Access agnostic infrastructure — services
are independent of the underlying access network
• Full mobility — transparent connectivity across
heterogeneous networks, protocols, and access mechanisms
• Always on, always available capabilities, through sessions
that cross networks and devices automatically and
transparently
• User-centric context, both device and context-
Sensitive
•QoS (Quality of Service) : The IMS takes care of
synchronizing session establishment with QoS provision so
that users have a predictable experience
•Integration of different services : Operators can use services
developed by third parties, combine them, integrate them with
services they already have, and provide the user with a
completely new service

5. •Enables convergence, and interworks in
several dimensions – across fixed and mobile
access – in the service layer, control layer and
connectivity layer
•Fast and efficient service creation and delivery
by designing systems to support multiple
Application Servers. Same infrastructure can be
utilized for new services, with the
implementation effort focusing on the actual
service and not on basic features
•IMS has Communication Services which
standardizes a few basic communication
patterns that can then be provided as
application building blocks.
IMS

6. Packet Cable Specification and DOCSIS

7. What is CMTS
CMTS is a router with Ethernet interfaces (connections) on one side and coax RF
interfaces on the other side. The RF/coax interfaces carry RF signals to and from the
subscriber's cable modem.
Architecture of a typical VoIP/SIP scenario

8. 8

9. DOCSIS
Data Over Cable Service Interface Specification (DOCSIS ) is an international
telecommunications standard that permits the addition of high-speed data transfer to an
existing cable TV(CATV) system. It is employed by many cable television operators to
provide Internet access over their existing hybrid fiber-coaxial(HFC) infrastructure.
Architecture of a typical VoIP/SIP scenario
Features:
Channel width:
Down Steam- 6 MHz channels or 8 MHz channels
upstream-between 200 kHz and 3.2 MHz DOCSIS 2.0 also specifies 6.4 MHz
Modulation:
Down Stream- 64-level or 256-level QAM
Upstream- QPSK or 16-level QAM (16-QAM) for DOCSIS 1.x, and it uses QPSK, 8-QAM, 16-QAM, 32-QAM, 64-QAM
for DOCSIS 2.0 & 3.0. DOCSIS 2.0
 Throughput:
Down Stream- 42.88 Mbits/s per 6 MHz channel, or 55.62 Mbit/s per 8 MHz channel
Upstream- of 30.72 Mbit/s per 6.4 MHz channel, or 10.24 Mbit/s per 3.2 MHz channel

10. PacketCable
 PacketCable architecture contains three networks: the "DOCSIS HFC Access Network",
the "Managed IP Network" and the PSTN. The Cable Modem Termination System (CMTS)
provides connectivity between the "DOCSIS HFC Access Network" and the "Managed IP
Network". Both the Signaling Gateway (SG) and the Media Gateway (MG) provide
connectivity between the "Managed IP Network" and the PSTN.
Architecture of a typical VoIP/SIP scenario

11. PacketCable Implementation with Cisco BTS
Architecture of a typical VoIP/SIP scenario

12. PacketCable Implementation- Contd..
 The diagram shows high level diagram of a PacketCable DQoS network architecture that shows the three segment
model. In this diagram, the network elements impacted by DQoS are the Multimedia Terminal Adapter (MTA), the
Cable Modem Termination System (CMTS), the Call Management Server (CMS), and the Record Keeping Server
(RKS).
 The Cisco BTS 10200 Softswitch performs the functions of the CMS in a DQoS capable network.
Cable Modem Termination System (CMTS)-The CMTS is responsible for allocating and scheduling upstream and
downstream bandwidth in accordance with MTA requests and QoS authorizations established by the network
administrator. The CMTS implements a “DQoS Gate” between the DOCSIS cable network and an IP backbone.
 Cable Modem (CM)-The CM is the PacketCable network element responsible for classifying, policing, and marking
packets once the traffic flows are established by the DQoS signaling protocols.
 Call Management Server (CMS)-The Call Management Server entity performs services that permit MTAs to
establish Multimedia sessions .
 Media Gateway Controller (MGC)-The Cisco BTS 10200 Softswitch performs the function of a media gateway
controller (MGC),providing signaling to trunking gateways (TGWs). This allows calls to be connected between the
PacketCable network and the PSTN

13. IMS Migration

14. Typical VOIP/SIP scenario without IMS
Architecture of a typical VoIP/SIP scenario
 A basic enterprise VoIP/SIP solution
is illustrated in Figure. The key element
is a soft switch (SIP PBX) which might
be implemented as a combination of
several SIP entities, such as SIP
registrar, proxy server, redirect server,
forking server, Back-To-Back User
Agent (B2BUA) etc.
 SIP clients can be SIP hard-phones
or soft-phones on PCs, PDAs etc. A
PSTN gateway links the enterprise SIP
PBX to the public PSTN.
 Enterprise applications, media
servers, presence servers, and the
VoIP/SIP PBX are interconnected
through a company intranet.

15. Migration towards IMS
 With IMS, applications will be able to establish sessions across different access
networks, with guaranteed QoS, flexible charging & AAA support.

16.  In this solution, the enterprise domain always forks incoming calls to operator.com.
The enterprises SIP PBX works as a forking proxy during call setup.
INVITE
Migration towards IMS- forking calls
INVITE
Forking Solution

17. Migration towards IMS- Roaming
 When a user turns on a mobile terminal, it will register with the operator domain for
access. World-wide access is supported thanks to operator-operator roaming agreements.
Once able to send IP-packets, the client will contact the enterprise.com domain to register
under its new location and thereby inform SIP PBX about the location change.
INVITE
INVITE
Client Based Solution

18. Migration towards IMS- Presence
In this solution, both domains interconnect their presence servers. These two domains
have a business agreement so that they can watch the presence status off each other’s
domain for certain clients.
Presence Based Solution

19. Migration towards IMS- Possible Migration Scenarios
This solution requires an initial setup as the operator needs to store information that a
certain user belongs to a certain enterprise domain uses a certain pre-defined enterprise
based SIP URI.
 In enterprise domain there is an application server that handles the link registration using
subscribe-notify mechanism to do link-register service subscription.
Link Registration

20. Soft Switch Migration Towards IMS

21. Comparison Between Soft Switch and IMS
•IMS further decomposes softswitch functions and adds a few new concepts. Call control, user’s database and services,
which are the typical functions of softswitch, are controlled by separate units in IMS. CSCF (Call Session Control
Function) handles session establishment, modification and release of IP multimedia sessions using the SIP/SDP protocol
suite.
•Services features are separated from call control and handled by application servers.
•Subscriber’s database function is separated from service logic function and handled by HSS using open subscriber
directory interface.
Services Services
Users
Users
Services
Call Control
Function
Call/Session Control
Function
Access and Transport Access and Transport
Soft Switch IMS

22. Migration towards IMS- Phase 1
As the first step, the softswitch is decomposed into two logical components – subscriber facing unit and PSTN facing unit.
The subscriber facing unit in softswitch is upgraded to AGCF (Access Gateway Control Function) and PSTN facing unit
is upgraded to MGCF (Media Gateway Controller Function) to interwork with IMS as shown in Figure 3.
By separating the softswitch into these components, the network can be more easily scaled for better overall network
efficiencies. More AGCFs can be added as required, allowing the network to scale with increase in subscribers.
Similarly, More PSTN trunks can be added as traffic increases. Once PSTN and subscriber control functions are
separated, the IMS elements, CSCF and BGCF functions can be introduced. BGCF is the interface for interconnecting
IMS with legacy PSTN networks.
Decomposing Softswitch to AGCF and MGCF

23. Migration towards IMS- Phase 2
To retain existing customers and attract new customers, new SIP-based services can now be rapidly introduced and
delivered by deploying new Application Servers (AS).
IMS introduces the 3GPP specified ISC interface, which is a SIP-based interface for interfacing to application servers.
Using these constructs, multiple application servers from multiple vendors can be interconnected over the IMS ISC
interface.
Application servers can be used remotely for faster rollout of services.
Inserting Application Server for SIP application service and Solutions

24. Migration towards IMS- Phase 3
Moving toward fixed/mobile convergence(FMC), a service provider can address several business needs relating to the
introduction of “triple play on the move.”
The dual-mode devices can communicate over the cellular network, or act as a new endpoint on the IP network.
The Home Subscriber Server (HSS), the last missing piece of the IMS architecture, is introduced. It is needed to manage
subscriber data uniformly between the cellular and IP worlds.
The Handoff Server is also introduced in this phase. It runs on top of the ISC interface, and provides a seamless
experience when subscribers move from the cellular network to a Wi-Fi network.
The AGCF remains the functional centre of the
network, but with the introduction of the HSS, has
added the Cx and Sh interfaces defined by the
IMS, taking it a step further to becoming a
complete SCSCF.
Inserting HSS and Handoff Server for Fixed/Mobile Convergence

25. Thank you
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