Enhanced Data Rates for GSM Evolution

Enhanced Data Rates for GSM Evolution (EDGE) refers to a technique for increasing the data transmission rate in GSM networks by introducing an additional modulation method. With EDGE, GPRS data services are extended to ECSD to E-GPRS (Enhanced GPRS) and HSCSD.

EDGE represents an evolution of the GSM technology dar. It is basically a GSM with more bits per symbol, ie, higher bit rate for the same baud rate. EDGE can be integrated with moderate effort in the mobile networks as it does not disturb the already existing mobile telephony. Essentially, it is necessary to update the software of the GSM base station and replace if necessary individual components.

Dissemination

EDGE is considered as an intermediate step on the path towards UMTS, previously introduced in rural areas in the medium term as UMTS replacement, and was in 75 countries. Telecom Italia Mobile led one of the first European mobile operator EDGE one under the name of TIM Turbo. Meanwhile, there are also the service in Austria, Switzerland, Liechtenstein, the Netherlands, France, Czech Republic, Slovakia, Poland, Estonia, Latvia, Lithuania, Croatia, Luxembourg, Denmark, Turkey, Serbia, Macedonia, Russia, Hungary, Greece and in Germany.

Austria and Switzerland

In Austria, all three GSM providers (T -Mobile Austria, Mobilkom Austria, Orange Austria ) EDGE as an addition to its existing UMTS network. This combination is marketed by Mobilkom Austria as A1 UMTS EDGE and provides nationwide since the summer of 2005 fast mobile data transfer. In Switzerland, Swisscom Mobile EDGE was developed in spring 2005 with a population coverage of 99.6%.

Germany

In Germany the EDGE extension took place relatively late: T- Mobile launched the EDGE upgrade in March 2006 in Germany; since the spring of 2008, the technology is widely available in the GSM network of T -Mobile. Because of the EDGE - expansion T-Mobile received the contract for the German sales of the iPhone, since neither this nor UMTS HSDPA dominated in the market.

Vodafone began in spring 2007 with the deployment of EDGE in areas where no power was commanded by its own UMTS network. Meanwhile EDGE but also widely used in areas supplied with UMTS.

O2 began in July 2008 with the EDGE upgrade its network.

E-Plus announced in December 2008, gradually convert its entire network to EDGE: For the end of March 2009, a population coverage of 30% and by the end of 2009 was planned by 90%.

Modulation method

The increase in the data transfer rate in EDGE is achieved by a shift towards a more efficient modulation method. This is instead of the usual in the GSM standard Gaussian minimum shift keying technique ( GMSK ), the so-called 8- PSK method is used. This provides a data transfer rate of up to 59.2 kbit / s per time slot is enabled with EDGE. When using eight time slots up to 473 kbit be / s. In comparison, are possible with the data service GPRS maximum 171.2 kbit / s. The change of the modulation process occurs selectively only on the channels that are occupied by EDGE -enabled devices. This simultaneous interference-free use of GSM, GPRS and EDGE - enabled handsets in the same radio cell is possible.

The currently marketed devices are those of the EDGE multi -slot class 10 This means that these devices have a maximum of four downlink slots and two uplink slots. This results in a real maximum data transfer rate of 220 kbit / s downstream and 110 kbit / s upstream.

Services

EDGE offers the services ECSD and EGPRS. ECSD is an evolution of GSM HSCSD data service. EGPRS is an evolution of packet data service GPRS. Both developments offer significantly higher transfer rates. Usual rates are currently between 150 and 200 kbit / s While this is significantly less than in the UMTS networks, but after all the equivalent multiple ISDN speed and allows fast data transfer via a mobile device at virtually any location. For EDGE, no new transmitters and antennas, but only an upgrade of the existing infrastructure are necessary. This is easier and cheaper to implement than a completely new network.

Operation

Before the introduction of EDGE only modulation type GMSK used in GSM. GMSK modulation is a digital phase modulation, but it can be approximated by a BPSK modulation ( Binary Phase Shift Keying ). In GMSK 1 bit per symbol is transmitted. The symbol rate is 270 833 bps, according to 270.833 bit / s EDGE offers GMSK also 8 -PSK ( 8 Phase Shift Keying). This 3 bits per symbol are transmitted. Despite triple data rate the symbol rate is the same as for GMSK, and the pulse shape is chosen so that do not differ a GMSK and 8 -PSK, frequency spectrum.

In a good channel with little interference EDGE can transmit per unit of time three times as many bits. In a less good channel it comes, however, to frequent bit errors. Here GMSK is a better choice than less error-prone modulation. In the EGPRS service there is therefore the possibility that the power switch depending on the quality of the channel between GMSK and 8PSK. This adjustment of the transmission method on the quality of the channel is further refined by switching between different coding schemes within GMSK (MCS - 1 to MCS -4) and in 8 -PSK ( MCS- 5 to MCS -9). The optimized adaptation of the modulation and coding of the channel data rate is significantly increased.

EGPRS also offers all the advantages of packet data service GPRS, ie a transmission channel is reserved only when data is sent or received. This has the advantage that multiple users can share a channel. For this reason, the billing is based on the amount of data transferred, regardless of the duration of the connection can be made.

EDGE Evolution

EDGE "Evolution " or " Evolved EDGE " constitutes a development of EDGE technology with a higher data rate dar. This is achieved through various measures. By halving the transmission time intervals of 20 ms to 10 ms, the latencies are reduced. Bit rates are increased up to 1 Mbit / s peak speed and latencies of 100 ms using two carrier signals, higher symbol rate and 32QAM or 16QAM modulation instead of 8 -PSK and " turbo codes " to improve the error correction. A dual antenna can improve the signal quality. Some of the abilities use the same hardware as standard EDGE, so that device capabilities can be subsequently improved on EDGE evolution through software update.

Manufacturer of EDGE -enabled devices

As with the other GSM technologies also provide, for example, Alcatel- Lucent, Nokia Solutions and Networks, Ericsson and Motorola infrastructure for mobile networks. Corresponding devices (mobile phones ) are available from all major manufacturers. EDGE is supported by many phones without UMTS as a technology for fast data transfer (via GSM standard speed ), which indicates the absence of UMTS is partially compensated.