tailieunhanh - GSM Switching, Services and Protocols Part 12

General Packet Radio Service (GPRS) Packet data transmission has already been standardized in GSM phase 2, offering access to the Packet Switched Public Data Network (PSPDN); see Sections and . However, on the air interface such access occupies a complete circuit switched traf®c channel for the entire call period. In case of bursty traf®c (. Internet traf®c), such access leads to a highly inef®cient resource utilization. It is obvious that in this case, packet switched bearer services result in a much better utilization of the traf®c channels. This is because a packet channel will only be allocated when needed and. | 11 GSM Switching Services and Protocols . Second Edition. Jôrg Eberspâcher Hans-Jorg Vogel and Christian Bettstetter Copyright 2001 John Wiley Sons Ltd Print ISBN 0-471-49903-X Online ISBN 0-470-84174-5 General Packet Radio Service GPRS Packet data transmission has already been standardized in GSM phase 2 offering access to the Packet Switched Public Data Network PSPDN see Sections and . However on the air interface such access occupies a complete circuit switched traffic channel for the entire call period. In case of bursty traffic . Internet traffic such access leads to a highly inefficient resource utilization. It is obvious that in this case packet switched bearer services result in a much better utilization of the traffic channels. This is because a packet channel will only be allocated when needed and will be released after the transmission of the packets. With this principle multiple users can share one physical channel statistical multiplexing . In order to address these inefficiencies the General Packet Radio Service GPRS has been developed in GSM phase 2 . It offers a genuine packet switched bearer service for GSM also at the air interface. GPRS thus highly improves and simplifies the wireless access to packet data networks. Networks based on the Internet Protocol IP . the global Internet or private corporate intranets and networks are supported. In order to introduce GPRS to existing GSM networks several modifications and enhancements must be made in the network infrastructure as well as in the mobile stations. Users of GPRS benefit from higher data rates and shorter access times. In conventional GSM the connection setup takes several seconds and rates for data transmission are restricted to kbit s. GPRS in practice offers almost ISDN-like data rates up to approx. 40-50 kbit s and session establishment times below one second. Furthermore GPRS supports a more user-friendly billing than that offered by circuit switched data .