Ericsson CDMA2000 specifications Client

Figure 2

The IPMM system is built with service evolution in mind.

Ericsson￿	New service￿	New service￿
Instant Talk￿	#1￿	#2￿
Application￿	Application￿	Application￿
server	server	server

IPMM

CSCF

HSS

MRF

¥to ensure that the called party is a sub- scriber;

¥to determine who is to be included in the group during the call;

¥to determine whether or not users have activated Do-not-disturb mode; and

¥to check whether the user has activated manual or auto-answer mode.

The application server also stores and pass- es down rules and regulations to the MRF. Local policies stored in the application server typically include timer values, such as remaining talk time in a userÕs account.

The Instant Talk application server also supports group list management server (GLMS) functionality, which enables users with list management operations to create, modify, retrieve and delete the groups and contact lists needed for the Instant Talk ser- vice. The GMLS also provides storage space for groups and lists.

Client

the media resource function. Because Instant Talk is a half-duplex service, the media resource function must prevent two or more users from sending media at the same time. This is called talk burst control. The MRF employs a request/response mech- anism to control transmission rights. Users who want to transmit must wait until their requests have been granted. The MRF can also revoke transmission rights when a user abuses the service.

The HSS maintains the Instant Talk subscriber profile by keeping track of the core network node tasked with handling the subscriber. An evolution of the home loca- tion register (HLR) and the authentication center (AUC) used by all IMS services, the HSS also handles Instant Talk subscriber authentication and authorization functions.

Instant Talk application server

The Instant Talk application server is basi- cally a database tool that handles subscriber data during call set-up

Ericsson works with third parties to inte- grate clients into terminals from different vendors. Pre-integrated clients can be opti- mized for the hardware platform on which they run. For instance, to set its clients apart from downloadable clients, Ericsson can make use of the native voice codec imple- mented for circuit-switched calls, to in- crease performance and battery life.

To ensure maximum voice quality, even in environments with limited bandwidth, Ericsson employs the adaptive multirate (AMR) codec and the enhanced variable rate codec (EVRC). The AMR codec is used in EDGE, GPRS and WCDMA terminals; EVRC is used for CDMA2000 clients.

Besides SIP, Ericsson Instant Talk clients use the real-time transport protocol (RTP) to carry real-time data generated by the voice codec. Frame bundling is used to reduce the effect of relatively large headers in the IP/UDP/RTP layers. This means that several voice codec frames are sent in one RTP packet. As dictated by IETF, the

18 Ericsson Review No. 1, 2004