EDGE, short for Enhanced Data rates for GSM Evolution, and also known as Enhanced GPRS (EGPRS), is a standard of technology in wireless telecommunications introduced in 2003 that increases data transmission rates and improves data transmission reliability in GSM-enabled mobile phones.
It is usually classified as a second and three-quarters generation (2.75G) technology because although it fits the International Telecommunications Union criteria to qualify as third generation (3G) technology, it runs at a slower network speed (up to 236.8 kbps for 4 timeslots, 473.6 kbps for 8 timeslots).
It is also classified as 2.75G technology because of its variability: EDGE devices have different classes. EDGE devices of Class 3 and below only qualify as second generation (2G), but devices of Class 4 and above qualify as 3G.
EDGE may be used for any packet-switched application, for example, connecting to the internet. The increased data capacity of EDGE makes it important for the use of high-speed data applications such as video services and other multimedia.
Upgrading to EDGE is simple for existing GSM and GPRS networks, as it is a bolt-on enhancement, requires no hardware or software changes to be made in GSM core networks, and is able to function on any network with GPRS deployed on it.
However, EDGE does require some modification to base stations, such as installation of EDGE-compatible transceiver, as well as upgrade of the base station subsystem (BSS) to support EDGE. Upgrading to EDGE also requires new mobile terminal hardware and software for decoding and encoding the new modulation and coding schemes, as well as for carrying higher user data rates in order to implement new services.
EDGE uses nine modulation and coding schemes (MCS). One of these is Gaussian minimum-shift keying (GMSK), and another, used for the upper five MCS, is 8-phase shift keying (8-PSK). In EDGE, a 3-bit word is produced for every change in carrier phase, effectively tripling the gross data rate that GSM provides. Similarly to GPRS, EDGE employs a rate adaptation algorithm that adapts the MCS according to the quality of the radio channel, inclusive of the data transmission’s bit rate and robustness.
Incremental Redundancy is a new technology for EDGE that was not included in GPRS. In this process, redundancy information is sent to be combined in the receiver, rather than retransmitting disturbed packets. The probability of correct decoding is increased as a result of this process.
There is a new technology, EDGE Evolution, that serves as an improvement on EDGE. It features the following enhancements: reduced latency, possibly going down to 100 ms, accomplished by using dual carriers and lowering the Transmission Time Interval from 20 ms to 10 ms; bit rates that are increased up to 1 Mbps peak speed; a higher symbol rate and higher-order modulation, using 32 Quadrature Amplitude Modulation (32QAM) and 16QAM rather than 8-PSK; turbo codes to improve error correction; and better signal quality, achieved through the use of dual antennas.