Introduction to GPRS
GPRS stands for General Packet Radio Services. GPRS is available to IS-136 and GSM mobile phones users. GPRS is also described as Ã¢â‚¬Å“2.5GÃ¢â‚¬, a technology that is in between 3G and 2G. It uses the unused channels in the GSM system and offers moderate data transfer speed. Originally it was thought that GPRS will be allowed for other standards as well, but things have gone other way round. Now other standards are adding support for GPRS.
In many areas such as Finland, GPRS has become very economical. Some operators charge it for per kilobyte basis while others according to the time it is used. In 2000, when GPRS was instructed, it was very expensive. In Europe some operators charged as high as Ã¢â€šÂ¬20 per megabyte.
Services offered by GPRS compatible GSM mobile device include Point-to-Point (PTP) service, instant messaging, Push To Talk (PTT) and Multimedia Messaging Service (MMS).
GPRS: Packet-Switched Data Transfer
GPRS is based on packet-switched data transfer, which is much different from the old fashioned CSD or Circuit Switched Data connection. In CSD a dedicated connection is established from source to destination. This connection uses full bandwidth for that particular circuit as long as the circuit is not terminated. Disadvantage of this system is under utilization of resources. A circuit (our resource) may remain idle for some time, when data is neither being sent nor received, but still full bandwidth is dedicated to that particular circuit.
In GPRS we use packet-switching, which allows the utilization of same channel by different users. Data is only transmitted on request and hence the channel is free for requests from other users. Hence GPRS offers much efficient usage of the available bandwidth. Unlike circuit-switched connection, data transfer through GPRS is billed per kilobyte on information sent or received. This allows users to pay for quality of service instead of quantity ore duration of their connection.
Classification of GPRS
According to capability of GPRS, it can be classified as Class A, B, and C. Class A devices allow connection to GSM (SMS and voice) and GPRS service at the same time. Devices belonging to Class B can only use one service at a time i.e. either GPRS or GSM. During GSM activity (SMS or a phone call) GPRS is automatically suspended and is resumed when the GSM activity is terminated. This class is most common. Class C devices must be switched manually between GSM and GPRS.
Class A mobile phones are expensive because they require two radios. These radios allow the cell phone to transmit two different frequencies at the same time. A cheaper solution to the two radio problem is DTM (Dual Transfer Mode) option. Mobile phones using DTM are categorized as pseudo Class A.
Performance of GPRS is best described its Multislot Class. Speed of GPRS is directly proportional to TDMA time slots. Multislot Class starts from 1 to 12 and then jumps directly to 32. Here Class 32 GPRS has the best performance of all the classes.