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Introduction
General Packet Radio Service (GPRS) is a 2.5 generation packet based network technology for GSM networks.
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Data Speed
GPRS data speeds are expected to reach theoretical data speeds of up to 171.2 Kbps. However, this is based on optimal conditions in terms of available cell/sector capacity in terms of available time slots, maximum coding scheme (CS-4) as well as moible phone availability to support the maximum number of time slots - eight. More practical data rates are currently in the order of 40-60 Kbps.
3G technologies such as W-CDMA will theoreticaly provide up to 2 Mbps in a fixed location. There will, however, be some significant limitations to this theoretical capacity. While 3G (and beyond) is expected to usher in the advent of high-bandwidth, multi-media services, the real impetus for
2.5G and packet based mobile data lies elsewhere.
Impetus for GPRS
The major impetus for GPRS and other packet based mobile data technologies is the "always-on" capability. Being packet based, GPRS allows for the use of infrastructure and facilities only when a transaction is required, rather than maintaining facilities in a session-like manner. This provides tremendous infrastructure efficiency and service delivery improvements.
Using GPRS as a bearer for WAP, for instance, will allow for the use of WAP on a per-transaction rather than a per-minute-of-use basis. More importantly perhaps is the ability for GPRS to allow for autonomous service realization through the always-on capability. For example, a GPRS customer could receive content or services without actually manually invoking a service or transaction. This has significant implications for mobile commerce and location based services.
GPRS Architecture and Issues
GPRS architecture consists of Gateway GPRS Support Node (GGSN) and a Serving GPRS Support Node (SGSN). The GGSN acts as the gateway to other packet data networks such as the Internet. The SGSN is the serving node that enables virtual connections to the GPRS enabled mobile device and delivery of data.
The blessing and curse of the SGSN is that it supports an attach state when a user is engaged in GPRS data usage and a detach state when idle. The idle state creates a particular challenge for attempting to position the unit for location based services. In addition, GPRS presents a challenge in terms of the ability to offer prepaid mobile data services, which may be overcome by the introduction of CAMEL and perhaps the use of Parlay.
The evolution from GPRS to W-CDMA entails upgrade of the Radio Access Network (RAN) to include two new network elements. The Node B replaces the BTS and the Radio Network Controller (RNC) replaces the BSC in the RAN. However, mobile network operators will maintain their GPRS assets for that service and thus maintain the existing network elements along with the new ones for 3G. W-CDMA continues to use the same Core Network (CN) elements as GPRS.
Deployment and Operational Issues
Beyond the scope of this white paper, there are several significant issues associated with deployment and operation of GPRS systems. Those issues include:
Capacity and network optimization
Handset availability and performance
Quality of service
Charging for services
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