Technology Overview

GSM (Global System for Mobile Communications) networks have been deployed worldwide as second-generation mobile communications systems. GSM originally was developed to transmit voice, but is also able to transmit data with a max. load of 9.6 kbit/s in the downlink and uplink. With the technical interim solution HSCSD, the max. data rate was increased to 43.2 kbit/s in the downlink and 14.4 kbit/s in the uplink.

In Europe, GSM networks operate in the 900 MHz and 1800 MHz bands, while the USA and Canada use the 850 MHz and 1900 MHz bands. In addition, the 400 MHz and 450 MHz bands are becoming more and more popular in rural areas due to reduced requirements for base station density.

Packet data capabilities were added in the Release ’97 version of the GSM standard by means of GPRS (General Packet Radio Services). GPRS is a data service that is available to users of GSM and IS-136 handsets. GPRS can be used for all data services such as Internet browsing, WAP access, SMS, and MMS. In comparison to GSM, GPRS is packet-switched; in terms of multiple users, it shares the same transmission channel only when data must be sent. The achievable data rates in GPRS depend on the supported multislot class. The max. data rate per time slot is 21.4 kbit/s with a max. possible number of 8 slots in either the downlink or uplink direction. A multislot class of 10 mobile devices, for example, supports max. 4 Rx slots in the downlink and max. 2 Tx slots in the uplink, but the sum of both Rx and Tx slots is max. 5.

To increase the data transmission rate and to improve network capacity, EDGE (Enhanced Data for GSM Evolution) was introduced in Release ’98. With EDGE, a new modulation scheme is applied: 8-PSK (phase shift keying), i.e. three bits per RF modulated symbol as opposed to the original one bit per symbol in GPRS. This technology change triples the effective data rate for EDGE resulting in a peak date rate of 59.2 kbit/s per time slot. The maximum achievable data rate depends on the supported multislot class of the mobile device similar to GPRS. The average downlink data rate in commercially operated networks is in the range of 300 kbit/s. EGPRS is a superset expression comprising EDGE and GPRS.

EDGE Evolution contains a set of features specified in 3GPP Release 7. The primary motivation for enhancing EDGE is to ensure the future competitiveness of the dominant second-generation technology and specifically to provide service continuity across the various radio technologies (GERAN, UTRAN, LTE) supported by core network evolution, e.g. IMS. The improvements include DL dual carrier operation, higher order modulation (16QAM, 32QAM) in combination with an optional higher symbol rate and turbo coding in downlink, latency improvements, and the use of Rx diversity at the mobile station. Combining DL dual carrier and EGPRS2, peak data rates reach up to 1.9 Mbit/s in the downlink, whereas realistically data rates of 1 Mbit/s will be achieved.

Deployment Scenario

GSM/EDGE is the most popular mobile phone standard with rollouts across 177 countries worldwide, serving more than 3 billion users. GPRS, which only requires a software upgrade in the base station, has also been rolled out worldwide. EDGE was initially introduced in North America; meanwhile, over 80 % of commercial GSM/GPRS operators have committed to EDGE.

Rohde & Schwarz Test Solutions

Rohde & Schwarz provides a complete product portfolio for GSM/GPRS/EDGE: digital standards on general-purpose equipment such as the R&S®SMU200A vector signal generator and the R&S®FSQ signal analyzer; dedicated communications testers, e.g. the R&S®CMU200 universal radio communication tester or the R&S®CMU300 universal radio communication tester; protocol testers such as the R&S®CRTU-G universal protocol tester; and complete conformance test systems, e.g. the R&S®TS8950G. EDGE Evolution functionality is also supported by most signal generators and signal analyzers, while future implementations will reflect the latest 3GPP enhancements. Rohde & Schwarz has been offering products since the early introduction of GSM into the market and thus understands all aspects of implementing the latest developments in this technology.

Key Parameters

Standardization

In 1989, the GSM standard was defined by the Groupe Speciale Mobile and became an internationally accepted digital cellular telephony standard. GSM was later transferred to the ETSI technical committee, which continued to define the GSM standards. Today, GSM and EDGE are being specified in 3GPP (3rd Generation Partnership Project) and coordinated in TSG GERAN. The following link provides access to TSG GERAN specifications: http://www.3gpp.org/ftp/specs