2.5 G Wireless Communication Systems

Mobile phone system of generation 2.5 are regarded as an intermediate step between the second generation system , such as GSM, D/E-AMPS, ADC and JDC, and the tird generation technologies such as IMT-2000. in particitular, 2.5G provides higher bandwidths to support new services, including mobile multimedia. The most interesting standards are

CDMA-related: IS-95B and IS-95C, offering 64 and 144 kbit/s, respectively
IS-95A was a 14.4 kbit/s circuit-switched service. IS-95B achieves 64kbit/s by eliminating the header overhead and a transition to packet-switching.
High-Speed Circuit-Switched Data (HSCSD)
HSCSD replaces the GSM coding scheme. It add less redundancy than used for speech transmission. Meanwhile, four instead of one timeslot can be used. This allows the transmission of 57.6 kbit/s. HSCSD may be implemented in the base station just by a software upgrade.
General Packet Radio Service (GPRS)
GPRS also is an extension of GSM that uses multiple time slots within a TDMA frame. GPRS further allows the transmission of Internet TCP/IP messages to multiple users within a single GSM slot.
Enhanced Data Rates for Global Evolution (EDGE)
EDGE allows the transmission of up to 384kbit/s by involving 8PSK modulation instead of GMSK.

Justin Chang of AT&T Research Labs explains the goals of EDGE. EDGE is an evolution on GPRS and GSM.

More of this Interview

References:
GSM

JPL's Wireless Communication Reference Website

Chapter: Network Concepts and Standards

2.5 G Wireless Communication Systems

JPL's Wireless Communication Reference Website © 1993, 1995.