Enhanced DataService for GSM Evolution (EDGE) is a mobile communications system that, like High Speed Circuit Switched Data (HSCSD) and General Packet Radio Service (GPRS), is based on the existing GSM infrastructure. It is characterized by the highest transmission rates and is conceptually designed for mobile real-time applications such as video or Internet telephony.
In contrast to High Speed Circuit Switched Data (HSCSD) and General Packet Radio Service (GPRS), where the transmission speed is increased by optimizing the error correction, EDGE already starts with the modulation in order to achieve a higher data rate.
EDGE works with phase shift keying (8PSK), with which eight symbols can be transmitted and thus the transmission speed of a GSM channel can be increased to up to 59.2 kbit/s This method involves the simultaneous transmission of three bits. With this method, three bits are transmitted simultaneously in a group, with the carrier alternating between eight different phase positions. In contrast, with the existing GSMK method, which is used adaptively for heavily disturbed connections, only one bit is transmitted per transmission step.
Data rates of EDGEtransmission method, Gaussian Minimum Shift Keying (GMSK) results in transmission rates between 8.8 kbit/s per channel and 17.2 kbit/s per channel; with phase shift keying (8-PSK), the values are between 22.4 kbit/s per channel and 59.2 kbit/s per channel. This means that when using all eight channels with Gaussian Minimum Shift Keying (GMSK) in transmission mode with the Modulation and Coding Scheme (MSC4), a maximum data transmission rate of 137.6 kbit/s can be achieved. This value increases to a maximum transmission rate of 473.6 kbit/s with 8-PSK modulation in MSC9 mode. These values can only be achieved with interference-free stationary operation in the vicinity of the transmitting equipment.
EDGE represents the final stage of the planned expansion of existing GSM networks. On the part of the network operators, changes in the radio network and extensions of existing GPRS facilities are required. EDGE is the preliminary stage for Wideband Code Division Multiple Access (WCDMA) and UMTS. However, the GSM infrastructure must be converted for EDGE.