EDGE (Enhanced Data GSM Environment)
Enhanced data for global evolution (EDGE) is a high-speed mobile data standard, intended to enable second-generation global system for mobile communication (GSM) and time division multiple access (TDMA) networks to transmit data at up to 384 kilobits per second (Kbps). As it was initially developed just for GSM systems, it has also been called GSM384. Ericsson intended the technology for those network operators who failed to win spectrum auctions for third-generation networks to allow high-speed data transmission.
EDGE provides speed enhancements by changing the type of modulation used and making a better use of the carrier currently used, for example the 200kHz carrier in GSM systems. EDGE also provides an evolutionary path to third-generation IMT-2000-compliant systems, such as universal mobile telephone systems (UMTS), by implementing some of the changes expected in the later implementation in third-generation systems.
EDGE builds upon enhancements provided by general packet radio service (GPRS) and high-speed circuit switched data (HSCSD) technologies that are currently being tested and deployed. It enables a greater data-transmission speed to be achieved in good conditions, especially near the base stations, by implementing an eight-phase-shift keying (8 PSK) modulation instead of Gaussian minimum-shift keying (GMSK).
For EDGE to be effective it should be installed along with the packet-switching upgrades used for GPRS. This entails the addition of two types of nodes to the network: the gateway GPRS service node (GGSN) and the serving GPRS service node (SGSN). The GGSN connects to packet-switched networks such as internet protocol (IP) and X.25, along with other GPRS networks, while the SGSN provides the packet-switched link to mobile stations.
The additional implementation of EDGE systems requires just one EDGE transceiver unit to be added to each cell, with the base stations receiving remote software upgrades. EDGE can co-exist with the existing GSM traffic, switching to EDGE mode automatically.
GPRS is based on a modulation technique called Gaussian minimum-shift keying (GMSK). This modulation technique does not allow as high a bit rate across the air interfaces as 8 PSK modulation if introduced into EDGE systems. 8 PSK modulation automatically adapts to local radio conditions, offering the fastest transfer rates near to the base stations, in good conditions. It offers up to 48Kbps per channel, compared to 14Kbps per channel with GPRS and 9.6Kbps per channel for GSM. By also allowing the simultaneous use of multiple channels, the technology allows rates of up to 384Kbps, using all eight GSM channels.
Because the basic infrastructure interfaces with the existing GPRS, GSM or TDMA infrastructure, the major vendors are the incumbent GPRS and GSM suppliers such as Ericsson, Nokia, Motorola and Alcatel.
By providing an upgrade route for GSM/GPRS and TDMA networks, EDGE forms part of the evolution to IMT-2000 systems. Since GPRS is already being deployed, and IMT-2000 is not expected until 2002, there is a definite window of opportunity for EDGE systems to fill in as a stop-gap measure.