2.5 G Cellular Systems and Architecture

Introduction to GPRS and EDGE 2.5G System Architecture 2.5G Cellular System Introduction to GPRS and EDGE 2.5G System Architecture

Evolution of Wireless

GPRS General Packet Radio Service Value added service to 2G to connect users to IP (Internet Protocol) -based data networks Forms basis of Packet Switched Network Data rate up to 115 Kbps with GPRS and 384 Kbps with EDGE

Motivation for GPRS Wireless access to internet and intranet

Circuit and Packet Switching Circuit Switching Dedicated resources to each user Higher performance and higher cost Packet Switching Shares resources with multiple users Lower performance and lower cost Requires MAC (Medium Access Control) Requires memory buffering

Circuit Switching Network

Packet Switching Network

EDGE Enhanced Data rate for Global Evolution Also called as Enhanced GPRS or EGPRS Improves efficiency of GPRS by use of advanced modulation technique- Octal PSK or 8 PSK Modulation

GPRS Network

GPRS Network Terms

Major functions of SGSN Provides Packet Switching and routing for GPRS services- analogous to MSC in 2G Contains a database of subscribers, including visitors (roamers) and home subscribers- analogous to VLR in 2G Handles authentication and admission control – analogous to MSC/HLR/AuC

Major functions of GGSN Provides Packet Switching and Routing for GPRS services Provides interface to external Public Data Networks (PDNs) e.g. the Internet First point of contact for packet session originating outside the PLMN

Major functions of GERAN Handles admission control Handles radio resource management Performs packet relay and routing functions

Elements of Communication System

Typical Wireless Terminal

Typical 2.5G Wireless Terminal