GSM / EGPRS / EDGE Evolution / VAMOS

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 it 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.

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. Unlike 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 10 mobile device, 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: 8PSK (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. Similar to GPRS, the maximum achievable data rate depends on the supported multislot class of the mobile device. 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 downlink dual carrier (DL DC) operation, higher order modulation (EGPRS2 with 16QAM and 32QAM) in combination with an optional higher symbol rate (Level B) and turbo coding in downlink, latency improvements, and the use of Rx diversity at the mobile station. Combining DL DC and EGPRS2 Level B, peak data rates reach up to 1.9 Mbit/s in the downlink, whereas realistically data rates of 1 Mbit/s will be achieved.

VAMOS is one of the most important features added in 3GPP Release 9 as it has the potential to double the voice capacity in the GSM network. The new AQPSK modulation scheme in DL enables allocation of different power levels on the I and Q phase. In combination with new orthogonal training sequences, two voice users can share the same physical resource. For more details on the VAMOS technology and its test requirements for both user equipment and base stations, see application note 1MA181 or the video.

Deployment Scenario

GSM/EDGE is the most popular mobile phone standard with rollouts across approx. 200 countries worldwide, serving more than 5 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®CMW500 wideband radio communication tester, the R&S®CMU200 universal radio communication tester, the R&S®CMU300 universal radio communication tester and the R&S®CRTU-G universal protocol tester; and complete conformance test systems, e.g. the R&S®TS8950G. The latest enhancements including EDGE Evolution functionality and the VAMOS feature are supported, while future implementations will reflect the latest 3GPP enhancements. Rohde & Schwarz has been offering products since the early launch of GSM on the market and therefore understands all aspects of implementing this truly global technology.

Key Parameters

GSM/EGPRS//EDGE Evolution/VAMOS
Frequency Range Show / Hide
T-GSM 380:
UL: 380.2 MHz - 389.8 MHz
DL: 390.2 MHz - 399.8 MHz
T-GSM 410:
UL: 410.2 MHz - 419.8 MHz
DL: 420.2 MHz - 429.8 MHz
GSM 450:
UL: 450.4 MHz - 457.6 MHz
DL: 460.4 MHz - 467.6 MHz
GSM 480:
UL: 478.8 MHz - 486 MHz
DL: 488.8 MHz - 496 MHz
GSM 710:
UL: 698 MHz - 716 MHz
DL: 728 MHz - 746 MHz
GSM 750:
UL: 777 MHz - 793 MHz
DL: 747 MHz - 763 MHz
T-GSM 810:
UL: 806 MHz - 821 MHz
DL: 851 MHz - 866 MHz
GSM 850:
UL: 824 MHz - 849 MHz
DL: 869 MHz - 894 MHz
P-GSM 900:
UL: 890 MHz - 915 MHz
DL: 935 MHz - 960 MHz
E-GSM 900:
UL: 880 MHz - 915 MHz
DL: 925 MHz - 960 MHz
R-GSM 900:
UL: 876 MHz - 915 MHz
DL: 921 MHz - 960 MHz
DCS 1800:
UL: 1710 MHz - 1785 MHz
DL: 1805 MHz - 1880 MHz
PCS 1900:
UL: 1850 MHz - 1910 MHz
DL: 1930 MHz - 1990 MHz
Modulation GMSK
8PSK (EDGE)
QPSK, 16QAM, 32QAM (EDGE Evo)
AQPSK (VAMOS)
Multiple Access TDMA/FDMA
Duplex (Uplink/Downlink) FDD
Channel Bandwidth 200 kHz
Peak Data Rate 14.4 kbit/s (GSM)
171.2 kbit/s (DL, 8 slots, GPRS)
128.4 kbit/s (UL, 6 slots, GPRS)
473.6 kbit/s (DL, 8 slots, EDGE)
355.2 kbit/s (UL, 6 slots, EDGE)
1.89 Mbit/s (DL, 8 slots, EGPRS2-B and DL DC)
710 kbit/s (UL, 6 slots, EGPRS2-B)

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