VoIP Service for Mobile Network

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September 30, 2005 Girish Kumar Patnaik 2

Introduction

• Voice over IP (VoIP)

– Supporting telephony services over an Internet

Protocol network

– Telecommunication and Internet Protocol

Harmonization over Network (TIPHON) specifiesthe mechanism to provide the service control

functions for convergence of IP networks, mobile

networks, Fixed wireless networks and PSTN.




TIPHON Architecture

Mediation Gatekeeper serves as a VLR to support roaming management.

BSC/BTS in the IP network provides wireless access to the IP network




Ericsson’s GSM on the Net

• Similar to TIPHON, utilizes corporate intranet

• Supports user mobility and terminal mobility





• Network elements of GSM on the Net(contd.):

– Service Node• Enables user mobility, controls call among

different types of terminals and translates addresses

between PSTN and GSM on the Net.

• Provides authentication, resource management,

least-cost routing and administration for useridentity and service profile





• Network elements of GSM on the Net(contd.):

– Access Node

• Manage connection, mobility and radio resources

• It does not provide trunks for user information

transmission, instead controls only thecommunication between the end points

• Consists of:

– Network Access Controller (NAC): responsible for alltasks related to the core network

– Radio Network Server (RNS): responsible for the tasks

related to the BTS nodes





• Network elements of GSM on the Net (contd.):– GSM/BTS

• Provides wireless access for a GSM MS in the IP network

• Consists of BTS and the A-bis gateway connected to RNS

– Gateway

• Provides interface between GSM on the Net and othernetworks (particularly GSM)

• Consists of both voice and SS7 gateway functionality

– Terminal Equipment• Can be an IP phone, PC (for video phone calls), DECT

Phone or GSM Mobile Station





• Based on the user identity, the Service

Node keeps the profiles of the registered

users to indicate the services (call

forwarding, call waiting) subscribed to by

the users.• The Access Node is responsible for call

handling of the GSM MS.




The iGSM Wireless VoIP

Solution• Another TIPHON scenario supporting usermobility for GSM subscribers to access VoIP

services• A GSM subscriber ordering the iGSM service

– can enjoy the standard GSM services when he is in the

GSM network – Can utilize H.323 terminal (IP phone or a PC) to

receive an incoming call to his MSISDN when he is inthe IP network

• GSM roaming mechanism determines whether thesubscriber is in the GSM network or the IP

network

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The iGSM Wireless VoIP

Solution• Difference between iGSM solution and

GSM on the Net– iGSM is a value-added service to the public

GSM networks

– iGSM does not introduce wireless accessequipment (GSM BTS) in the IP network

– iGSM service is implemented using general IP

gateway / gatekeeper

• iGSM consists of the GSM and H.323 (IP)

networks




H.323 Network




H.323 Network

• Consists of endpoints:– Terminal

• Customer premises equipment (CPE) that provides

audio, video and data communications capability forpoint-to-point or multipoint conferences in the H.323network

– Gateway• Performs all control functions (setup and release) and

the communication protocol translation mechanism

between an H.323 endpoint and an endpoint of acircuit-switched network (PSTN, ISDN, LAN)

• Two H.323 endpoints in the same network cancommunicate without involving the gateway




H.323 Network

• Consists of endpoints (contd.):– Gatekeeper

• Optional in an H.323 network • Provides call control services to the H.323

endpoints

• Functions of the gatekeeper include addresstranslation, admission control, bandwidthcontrol and zone management

• Also perform optional functions such as callcontrol signaling, call authorization, callmanagement, and so on.




H.323 Network• Consists of endpoints (contd.):

– Multipoint Control Unit (MCU)

• To support multipoint conferences

– Multipoint Controller (MC)• Provides control functions to support conferences between

three or more endpoints in a multipoint conference

• Every MCU contains an MC• Terminals, gateways and gatekeepers may or may not

contain MCs

– Multipoint Processor (MP)• Receives audio, video and/or data streams from the

endpoints involved in a multipoint conference

• MP is optionally included in a gateway, gatekeeper or MCU




iGSM Architecture




iGSM Architecture

• GSM network is not modified• In the IP network, an iGSM gateway is implemented to

perform two major functions besides the standard

H.323 mechanisms:– GSM MAP and H.323 RAS (Registration, Admission, and

Status) protocol translation

– GSM/PSTN/IP call setup and release• iGSM gatekeeper serve as VLR for iGSM subscribers

who visit the IP network

• Every iGSN gatekeeper is assigned an ISDN number• iGSN gatekeeper also maintains a list of all iGSM

subscribers

iGSM Procedures and




iGSM Procedures and

Message Flows• Every iGSM subscriber has a record in thedatabase, consists of following fields

– MSISDN of the MS– Transport address of the H.323 terminal for the

subscriber in the IP network

– Password of the iGSM subscriber– HLR Address (ISDN number) of the iGSM subscriber

– IMSI (International mobile station identity) of the MS

– User profile, indicating the service features andrestrictions of the iGSM subscriber

– Presence indication of the iGSM subscriber in the IP

network

iGSM Registration




iGSM Registration

Message flow for iGSM




Message flow for iGSM

Registration

iGSM Deregistration




iGSM Deregistration

• Subscriber moves from the IP network to the GSM network

• iGSM gatekeeper is the “old VLR”

Call Delivery to the IP




Call Delivery to the IP

Network

Message flow for iGSM Call Setup




Message flow for iGSM Call Setup

VoIP Service for Mobile Network

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