GPRS (General Packet Radio Services) Overview

GPRS Overview:

GPRS is a global standard for wireless communication. GPRS was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP). GPRS is abbreviation of “General Packet Radio Services”. Its speed can be up to 115 Kbps (Kilo Bits Per Seconds). This speed is very much high when compared to current GSM (Global System for Mobile Communications) speed which is only 9.6 Kbps. Practically, Speed of GPRS is 115 Kbps but GPRS provides a theoretical speed as high as 171.2 kbps because of concatenating eight GSM channels. Usually, per Megabyte of data/traffic transferred is charged in GPRS.

GPRS Technology, no doubt, supports a wide range of bandwidth. Hence, GPRS is efficient for use with limited bandwidth access devices and is particularly suited for sending and receiving small packets (data packets) of data on hand held devices such as Mobile Phones and PDAs (Personal Digital Assistants). This data can be in form of an e-mail, bits used for Web browsing, as well as large volumes of data.

Packet-Switching service is used for GPRS. GSM time slots are used for data communication and it supports TCP/IP (Transmission Control Protocol, Internet Protocol) and X.25 protocols, with surety of quality of service (QoS) mechanisms. One can use GPRS to enable high-speed data-communication mobility. GPRS is also considered as most useful Data-Communication Service for data transferring applications such as mobile Internet browsing, e-mails and various push technologies used in Hand Held/Palm Devices.

Cellular systems with 2G and GPRS are often described as "2.5G" enabled systems. 2.5G is a technology between the second (2G) and third (3G) generation of mobile telephony communication. GPRS provides a fair speed of data transfer while using unused Time Division Multiple Access (TDMA) channels in the GSM system.

In GPRS Technology, a user is assigned, during a session, to one pair of up-link and down-link frequency channels. Packet mode communication makes it possible for many users to share the same frequency channel. Corresponding to a GSM time slot, these packets have constant length. The down-link in GPRS uses first-come first-served packet scheduling.

Logical Architecture of GPRS:
GPRS network is composed of the following network nodes:

Gateway GPRS Support Node:

The GGSN provides the facility of interworking with external Packet Data Networks (PDNs). It can be linked to one or several data networks. Via IP-Based GPRS backbone network, it is connected with SGSNs. The GGSN is a router that forwards incoming packets from the external PDN to the Serving GPRS Support Node (SGSN) of the addressed Mobile Stations (MS). It is also responsible for forwarding outgoing packets to the external PDN. An example of a PDN is the Internet network.

Serving GPRS Support Node:

The SGSN node is basically responsible for serving the Mobile Station (MS), and MS is responsible for GPRS Mobility Management (GMM). It delivers packets to the MS and communicates with the Home Location Register (HLR) to fetch the GPRS user profile. It manages the registration of the new mobile users in order to keep a record of their Location Area (LA) for routing purposes. The SGSN may be found connected to one or several Base Station Systems (BSSs).

Equipment Identity Register:

The Equipment Identity Register is a central anti-fraud database which validates the IMEI number as calls are made on the Mobile network.

Mobile Switching Center/Visitor Location Register:

The MSC coordinates the setting up of calls to and from GSM users and manages GSM mobility. The MSC is not directly involved in the GPRS network. It forwards circuit-switched paging for the GPRS-attached MSs to the SGSN when the Gs interface is present.

The Gs Interface is a GPRS interface which is located between the SGSN (Serving GPRS Support Node) and the MSC (Mobile Switching Centre).

Base Station System:

The BSS ensures the radio connection between the mobile and the network. It is responsible for radio access management. The BSS is composed of two elements: the Base Transceiver Station (BTS) and the Base Station Controller (BSC). The BTS integrates all the radio transmission and radio reception boards, while BSC is responsible for the management of the radio channels. The BSC has switching capabilities that are used for circuit-switched calls and can also be used for GPRS traffic.

Home Location Register:

HLR is a Database in a cellular network that contains subscriber information. It is the functional unit responsible for managing mobile subscribers.

Services Offered by GPRS:

GPRS upgrades GSM data services with access of:

• Push to talk over Cellular PoC / PTT
• Wireless Application Protocol (WAP) for Palm/Hand held Devices
• Short Message Service (SMS)
• Multimedia Messaging Service (MMS)
• Point-to-point (PTP) service
• Internetworking with the Internet (IP protocols)
• Instant Messaging and Presence

Future Enhancements:

GPRS id much flexible to add new functions, for example:

• New accesses
• More capacity
• More users
• New protocols
• New radio networks etc.