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ST55 Level 2 Service Manual
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1 GPRS (GENERAL PACKET RADIO SERVICE)
GPRS is a new non-voice value added services that allows information to be sent and received
across a GSM mobile telephone network. It supplements today’s Circuit Switched Data (CSD)
and Short Message Services (SMS). GPRS involves overlaying a packet based air interface on
the existing circuit switched GSM network. This gives the option to use a packet-based data
service. The information is split into separated but related “packets” before being transmitted and
reassembled at the receiving end. Theoretically, maximum speeds of up to 171.2 kilobits per
second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about
3 times as fast as the data transmission speed possible over today’s fixed telecommunications
networks and 10 times as fast as current Circuit Switched Data services on GSM networks.
Figure1. Example of GPRS data transmission
Example: Cell with 1 Frequency channel:
1 physical channel for signaling, 4 physical channels for Circuit switched and 3 physical channels
for Packet switched.
