Introduction to CSD ( Circuit Switched Data )
Mobile technology has gone beyond imagination of one would have thought. We have read about GSM technology which is used for voice data. GSM use technology called Circuit Switched Data (CSD) for transferring data. CSD creates special connection to the network to transfer data, it can take up to 30 seconds before this connection can put to use. After the connection is made, data started to transmit and subscriber is charged for the amount of time it remained connected to the network. Data transmission speed is relatively slow using CSD which is about 14.4 kbps for those GSM networks who are operated at 1800 frequency band, even low at 9.6 kbps when 900 MGHZ GSM network is used.
GPRS GPRS Technology :
Things have changed dramatically in recent past when it comes to usage of internet on mobile handsets. There wouldn’t be many who would have thought to do all those things on mobile handset which we are capable to do with a press of button today. Technologies are commercially launched which can transfer data other than just voice data at higher data rate. Yes, Data which contains emails, browsing packets and other modern capabilities for communication. All that became possible because of GRPS; it stands for General Packet Radio Services.
GPRS is one of the technologies to improve 2G phones (second generation phones) to enable them for transferring data at higher speed, GPRS allows mobile phones to remain connected to network and transfer requested or sent data instantly, e.g. if you receive MMS from other mobile phone, you do not need to press a button to check if you have any new MMS, instead mobile handset notifies you when new MMS is downloaded to your mobile. GPRS technology can provide you up to 32 kbps to 48 kbps. One of the features of GPRS technology which makes it even more useful and practical is that data can transfer during the call and there is no requirement of disconnecting call to receiving incoming or out going data. For example, you can receive SMS during the call and you can reply to it without having to disconnect your on going call. GPRS usage is charged for the amount of data sent and received, unlike CSD which is charged for amount of time it remained connected.
GPRS technology enabled to move 2G networks closer to the performance of 3G networks. 3G (Third Generation) support networks are best at transferring data to unbelievably higher data rates which can go up 2 Mbps. Data rate up to 2Mbps made so many impossible tasks very possible on mobile phones which was once only possible on computers. With this data rate it is possible to do video calling, video streaming and downloading, web browsing, emailing etc. Improved 2G networks (GPRS) manages to support few of applications like web browsing, emailing, video streaming, Multimedia messaging service etc. therefore GPRS can also be said that it is 2.5 generation technology. Technologies like HSCSD and EDGE are enhancements to the CSD technology
GPRS Class Types :
GRPS have numerous classes. Each class represents the amount of data that can be transferred with in the network. All classes have number timeslots which are available for uploading data to the phone or download data to the phone. Voice calls have additional times slots for communication and does not use timeslots dedicated for transferring of data. The more the timeslots are available more and faster the data can be transferred as these timeslots are used simultaneously. All timeslots are shared over the network by the users; GRPS send and receive data in packets and all the slots are not used all the time, hence increase the overall performance and capacity of the network. During the peak time, lower data rates can be experienced as network will give higher priority to the voice calls.
Most commonly used classes for GPRS:
|GRPS CLASSES||SLOTS||Maximum Data Rate|
|Class 2||3||8 – 12 kbps upload / 16 – 24|
|Class 4||4||8 – 12 kbps upload / 24 – 36|
|Class 6||4||24 – 36 kbps upload / 24 – 36|
|Class 8||5||8 – 12 kbps upload / 32 – 40|
|Class 10||5||16 – 24 kbps upload / 32 – 48 kbps|
|Class 12||5||32 – 48 kbps upload / 32 – 48 kbps download|