GPRS

Introduction to GPRS

 

Technology which permits mobile data communication using packet switching techniques.

GSM allows circuit switched (CS) data transfer

—       Data transfer on a dedicated channel (connection oriented)

—       Connection setup procedure needed as in modem

—       Subscriber charged according to time of connection

—       TS is held for duration of connection - waste of resources

GPRS designed as an extension to digital cellular networks

—       Connectionless packet switched (PS) data service

—       Standardised by ETSI

—       Radio resources shared between CS and PS data

—       New terminals are required

 

 

In GPRS up to 8 time slots of a TDMA-frame can be dynamically bundled for a single user, but in reality, most MS are limited to 3 timeslots. Given channel bundling with up to 8 physical channels/time slots and CS-4 with a data rate of 21.4 kbps, a total of 171.2 kbps is available for a single user. In reality, subscribers are normally limited to three time slots. And they can only expect CS-1 and CS-2 in use. Therefore, data rate of up to 30 to 40 kbps can be expected.

 CS traffic leaves some capacity for PS traffic

 

Key learning points

GPRS uses a packet-based technique which will enhance GSM data services significantly, especially for bursty Internet/intranet traffic.

Some application examples:

—       bus, train, airline information

—       locating restaurants and entertainment venues

—       weather information

—       security information

—       lottery

—       e-commerce

—       banking

—       e-mail

—       web browsing

The main advantages of GPRS for users:

—       Instant access to data as if connected to an office LAN

—       Charging based on amount of data transferred (not the time connected)

—       Higher transmission speeds

The main advantages for operators:

—       Fast network roll-out with minimum investment

—       Excess voice capacity used for GPRS data

—       Smooth path to 3G services

—      In circuit switching, each time a connection is required between two points, a link between the two points is established and the needed resources are reserved for the use of that single call for the complete duration of the call.

—      In packet switching, the data to be transferred is divided up into packets, which are then sent through the network and re-assembled at the receiving end.