GPRS Software Protocol
gprs software or General Packet Radio Service is a packet switched technology, based on
GSM. The radio and network resources of gprs software are only accessed when data actually
needs to be transmitted between the gprs software mobile user and the gprs software network.
This data is divided into packets and is then transferred via the radio and core gprs software
network. Between alternating transmissions, no gprs software network resources need to be
allocated. gprs software offers up to 115 kbps, depending on the network availability, channel
coding scheme and terminal capability. This increase in speed in gprs software with respect to
GSM is achieved by using more than one timeslot of the TDMA frame. Due to the packet
switched characteristics of gprs software the allocation of the available timeslots may vary
from one instant to the next (e.g. it may have 8 timeslots at one time and 4 later on).
The General Packet Radio Service (GPRS) is a new value added service that allows
information to be sent and received across a mobile telephone network. It supplements today's
Circuit wireless Switched Data and Short Message Service.
Timeslot building requires new functionality on the mobile side. gprs software needs a
Serving gprs software support node (SGSN), a Gateway gprs software support node (GGSN)
and a charging gateway function to support packet switched transactions. The packet switched
traffic is separated from the circuit switched traffic at the BSC/PCU and diverted to the gprs
software core network. To support point-to-multipoint features, a point-to-multipoint Service
Center (PTM-SC) needs also to be added.
Depending on the environmental radio conditions, one of the four coding schemes (CS1, CS2,
CS3, CS4) can be selected. CS1 and CS2 offer good error detection and correction with low
throughput; in the first step of gprs software only these two techniques may be used. CS3 and
CS4 provide higher throughputs but have little or no error correction capabilities.
Table 1 shows the different data rates that can be achieved with the different coding
techniques.
Table 1. Data Rate for GPRS Software
User Data Rate
1 Timeslot
8 Timeslot
CS1
9.05 kbps
72.4 kbps
CS2
13.4 kbps
107.2 kbps
CS3
15.6 kbps
124.8 kbps
CS4
21.4 kbps
171.2 kbps
Because gprs software is packet switched traffic, new protocols and channel types are
required. In gprs software the mobile device is permanently attached to the network,
providing a virtual connection without cost and data transfer (GPRS-Attach). gprs softwareAttach procedure is executed whenever a gprs software enabled mobile station is switched on
and needs to inform the network about its presence.
The two peers of a gprs software attach procedure are the mobile station (MS) and the Serving
gprs software Support Node (SGSN). Depending on the availability of the packet Common
Control Channel (PCCCH), the gprs software-Attach procedure may be executed on Circuit
Common Control Channel (CCCCH).
Figure 1 shows the gprs software system architecture, indicating new functionality required
for phase2+ operation.
Figure 1. GPRS Software system architecture
Configurations:
Layer 1. Radio gprs software. This layer includes the following GSM phase2+ ETSI
standards:
·GSM 05.02 Access & Multiple Multiplexing.
·GSM 05.03 Interleaving Code/Decoder Channel.
·GSM 05.04 Demodulator and Modulator.
·GSM 05.05 Receiver and Transmitter.
·GSM 05.10 Synchronization.
Layer 1.Vocoders gprs software. This layer includes the following GSM phase2+ ETSI
standards:
·GSM 06.10 Full rate speech transcoding.
·GSM 06.20 Half rate speech transcoding.
·GSM 06.60 Enhanced Full rate speech transcoding.
·GSM 06.90 Adaptive multi-rate speech transcoding.
·GSM 06.93 Discontinuous transmission for Adaptive Multi-rate.
Layer 2 & 3 GSM phase 2+ ETSI standards:
·GSM 03.09 Hand-over.
·GSM 03.22 Link control.
·GSM 04.04 PROTOCOLS Layer 1.
·GSM 04.05 PROTOCOLS Layer 2.
·GSM 04.06 PROTOCOLS Layer 2.
·GSM 04.07 PROTOCOLS Layer 3.
·GSM 04.08 PROTOCOLS Layer 3.
·GSM 05.08 Power control.
EGPRS (also call EDGE) is an enhanced version of gprs software, that uses a different
modulation technique, 8 PSK, that has a spectral efficiency of 3 bits/s/Hz. gprs software uses
GMSK, with a spectral efficiency of 1 bit/s/Hz.
GPRS Software will provide an important boost to mobile data usage, because of its flexible
feature set, its latency, efficiency and speed.
The following text, in the links below, provides VOCAL datasheet as a source of background
information about gprs software.