The General Packet Radio Service is essentially a clever hack to add a packet switching network to existing second - generation (2G) mobile phone networks. Unlike UMTS and other third - generation (3G) network systems which need an entirely new network infrastructure, GPRS piggy-backs on top of the GSM or TDMA network. As a result, GPRS is often referred to 2.5G or 2 ½G.
2G networks such as GSM make use of circuit switching to share out network resources. This means that each time slot is allocated to one user. Packet switching, on the other hand, allocates time slots as needed, breaking the data into individual 'packets'. If a user isn't transferring any data, they use no network resources. This is a lot more efficient, and is the basis of TCP/IP and the internet. One upshot of this is that GPRS phones could, in theory, be each allocated an IP address, making them accessible to the internet as a whole.Because GPRS supports TCP/IP directly, no PPP dialup is needed to connect to the internet, giving an always on connection similar to DSL or cable modem.
In theory, connection speeds of up to 171.2kbps are possible, but this is assuming one person using all eight time slots, without any error correction. This is totally impossible to achieve in the real world. Apart from the unlikelihood of there being only one user in a cell, networks will restrict the number of slots each user can take, and error correction will certainly be needed to deal with interference. Also, most current phones are unable to handle more than 2 or 3 timeslots. All this translates to actual speeds that are likely to be slower than 56kbps dialup modem, but faster than the 9.6kbps or 14.4kbps available over GSM.
Unlike 3G, where most of the real benefits are for the network operator in more efficient use of their spectrum, the main benefits of GPRS are for the end user. The always-on nature of the connection makes it a lot more useful than the dialup WAP services that bombed so heavily. The new GPRS-enabled phones from the likes of Nokia and Sony Ericsson have good large screens, some with full colour, as well as built-in POP3 mail clients. Hey, I want ICQ on my mobile! The main drwback is the extortionate 'per byte' charges levied by the operators. In the UK at least, this can be around £8 per MB! Hopefully this is just to catch out early adopters like me, and prices will adjusted soon.
By linking up to a PDA or laptop, whether via cable, IrDA or Bluetooth, things become a bit more useful, with access to proper web browsers. The iPAQ has become the standard hardware for the testing of GPRS web services, used by the likes of Ericsson and Vodafone for their pilots and demos.
Obviously, the main beneficiary of all of these technologies are the infrastructure and handset manufacturers. Sure enough, they have been pushing their GPRS-enabled phones hard, despite the limited support offered by network operators at this moment. Some very tasty phones they are too!
A selection of GPRS handsets:
Nokia GPRS phones
Sony Ericsson GPRS phones
Motorola GPRS phones