Enhanced Data Rates for GSM Evolution

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Comparison of the maximum achievable bit rates with different mobile radio standards. ( logarithmic representation )

Enhanced Data Rates for GSM Evolution ( EDGE ) describes a technology for increasing the data transmission rate in GSM mobile radio networks by introducing an additional modulation method . EDGE extends the data services from GPRS to E-GPRS (Enhanced GPRS) and HSCSD to ECSD.

EDGE represents a further development of GSM technology. Basically, it is a GSM with more bits per symbol , ie a higher bit rate with the same baud rate . EDGE can be integrated into cellular networks with moderate effort, as it does not interfere with existing cellular telephony. Essentially, it is necessary to update the software of the GSM base station and, if necessary, to replace individual components.

distribution

EDGE is seen as an intermediate step on the way to UMTS , in rural areas in the medium term as a UMTS replacement (in the sense of: "instead of" / "instead of"; not in the sense of: "replacing", because EDGE is slower than UMTS), and has so far been introduced in 75 countries. Telecom Italia was one of the first European mobile network operators to introduce EDGE under the name " TIM Turbo". The service is now also available in Denmark, Germany, Estonia, France, Greece, Croatia, Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia, the Netherlands, Austria, Poland, Russia, Switzerland, Serbia, Slovakia, the Czech Republic and Turkey and Hungary.

Austria and Switzerland

In Austria, all three GSM providers ( Magenta Telekom , A1 and Drei ) offer EDGE as a supplement to their existing UMTS network. This combination is marketed by Mobilkom Austria as "A1 UMTS + EDGE" and has made fast mobile data transfer available across the board since summer 2005. In Switzerland, Swisscom Mobile EDGE expanded in spring 2005 with a population coverage of 99.6%.

Germany

In Germany, the EDGE expansion took place relatively late.

T-Mobile started the EDGE upgrade in March 2006. Since spring 2008, the technology has been available almost everywhere in T-Mobile's GSM network. Because of the EDGE expansion, T-Mobile was awarded the contract to sell the iPhone in Germany , because it did not support UMTS or HSDPA when it was launched .

In spring 2007, Vodafone began making EDGE available in areas where no coverage was provided by its own UMTS network. EDGE is now also being used in areas covered by UMTS.

O 2 began EDGE upgrading its network in July 2008.

In December 2008, E-Plus announced that it would gradually switch its entire network to EDGE: for the end of March 2009 a population coverage of 30% and by the end of 2009 of 90% was planned.

Modulation method

The increase in the data transmission rate with EDGE is achieved by changing to a more efficient modulation method . Instead of the Gaussian minimum shift keying method (GMSK) common with the GSM standard, the 8-PSK method is used. This enables a data transmission rate of up to 59.2 kbit / s per time slot with EDGE . When using eight time slots, up to 473.6 kbit / s is achieved. In comparison, the GPRS data service allows a maximum of 171.2 kbit / s. The change of the modulation method takes place selectively only on the channels that are occupied by EDGE-capable devices. This enables simultaneous, interference-free use of GSM / GPRS and EDGE-capable end devices in the same radio cell.

The terminals currently available on the market are those of EDGE multislot class 10. This means that these devices have a maximum of four downlink slots and two uplink slots. This results in the maximum data transfer rates of around 220 kbit / s in the download and around 110 kbit / s in the upload .

EGPRS Coding Scheme (MCS)
MCS Data transfer rate 
(kbit / s / slot) 		modulation
MCS-1 08.8 GMSK
MCS-2 11.2 GMSK
MCS-3 14.8 GMSK
MCS-4 17.6 GMSK
MCS-5 22.4 8-PSK
MCS-6 29.6 8-PSK
MCS-7 44.8 8-PSK
MCS-8 54.4 8-PSK
MCS-9 59.2 8-PSK

services

EDGE offers the services ECSD and EGPRS. ECSD is a further development of the GSM data service HSCSD . EGPRS is a further development of the GPRS packet data service. Both further developments offer significantly higher transmission rates. Currently, rates between 150 and 200 kbit / s are common, which corresponds to a multiple of the ISDN speed. EDGE can be implemented cost-effectively by upgrading the existing GSM infrastructure.

functionality

Before EDGE was introduced, only the GMSK ( Gaussian Minimum-Shift Keying ) modulation type was used in GSM . GMSK modulation is a digital frequency modulation. With GMSK, 1 bit is transmitted per symbol. The symbol rate is 270,833 baud, corresponding to 270,833 bit / s. To increase the transmission speed (bps = bits per second), EDGE uses an 8-PSK (8-Phase Shift Keying) phase modulation in addition to the frequency modulation GMSK. With 8-PSK modulation, 3 bits are transmitted per symbol. Despite the triple data rate, the symbol rate is the same as with GMSK, and the pulse shape is chosen so that a GMSK and an 8-PSK frequency spectrum do not differ.

In a good channel with little interference, EDGE can transmit three times as many bits per unit of time. In contrast, bit errors occur frequently in a less good channel. As a less error-prone modulation, GMSK is the better choice here. In the EGPRS service, there is therefore the option of the network switching between GMSK and 8PSK depending on the quality of the channel. This adaptation of the transmission method to the quality of the channel is further refined by switching between different coding schemes within GMSK (MCS-1 to MCS-4) and within 8-PSK (MCS-5 to MCS-9). The data rate is increased significantly through the optimized adaptation of modulation and coding to the channel.

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

EDGE evolution

EDGE "Evolution" or "Evolved EDGE" or "E-EDGE" represents a further development of EDGE technology with a higher data rate. This is achieved through various measures. The latencies are reduced by halving the transmission time intervals from 20 ms to 10 ms. Bit rates are increased to a peak speed of 1 Mbit / s 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 error correction. A double antenna can improve the signal quality. Since Standard-EDGE operates on the same hardware as E-EDGE, it is possible to upgrade the existing infrastructure with a software update.

Manufacturer of EDGE-enabled devices

As with the other GSM technologies, Alcatel-Lucent , Nokia Solutions and Networks , Ericsson and Motorola also provide infrastructure for cellular networks. Appropriate end devices (cell phones) are available from all common manufacturers. EDGE was supported by many "telephones without UMTS" as a technology for faster data transmission (via GSM standard speed), which partially compensates for the lack of UMTS.

Individual evidence

  1. ^ Andrew S. Tanenbaum : Computer Networks. 5th, updated edition, Pearson Studium, Munich 2012, ISBN 978-3-8689-4137-1 , p. 194
  2. ↑ heise.de March 30, 2005, Swisscom closes gaps in broadband mobile communications with EDGE
  3. ↑ Vodafone: Large parts of Germany already opened up with the GPRS Turbo Teltarif, July 24, 2008
  4. ↑ O 2 starts EDGE expansion in the GSM network Teltarif, July 8, 2008
  5. ↑ E-Plus: Fast mobile internet is being expanded on a large scale Telariff

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