Jung-Fu Cheng

Evolution of EDGE to higher data rates using QAM

EDGE has enabled GSM networks to offer third generation services as part of the UMTS core network. This has been possible through two steps: the introduction of 8PSK modulation and the specification of interfaces from the GERAN (GSM/EDGE radio access network) to the UMTS core network. This paper studies further improvements to spectral efficiency and capacity for EDGE through the use of more sophisticated adaptive modulation schemes, and the use of newer coding schemes (see Nanda, S. et al., IEEE Commun. Mag., p.54-64, 2000; Ikeda, T. et al., IEEE Trans. Vehic. Tech., vol.49, p.404-12, 2000). It is possible to use theoretical predictions of outage analysis to predict the gain in performance due to the use of higher order modulations.

System performance with higher level modulation in the GSM/EDGE radio access network

The GSM/EDGE Radio Access Network (GERAN) is presently being evolved as a full complement to the 3G UMTS network. One part of this evolution is the introduction of efficient support of real-time packet data and alignment to the UNITS Core Network. Another part will introduce performance-enhancing features aimed at improving spectral efficiency, peak and average user-throughput and capacity. One such enhancement being considered is the use of Higher Level Modulations to enhance the user peak rate in the GERAN, in much the same way as the data rate for GPRS was enhanced with the 8PSK modulation in EDGE. By introducing new coding schemes based on QAM the maximum bit rate per time slot could be increased up to 88.8 kbit/s. This paper explains the GERAN concept and investigates possible system level gains, from both spectrum efficiency and perceived user quality perspective, with Higher Level Modulation in GERAN.

System capacity with transmit diversity techniques in GERAN

Transmit diversity techniques use multiple transmit antennas to enhance the spectral efficiency and/or data rate. Examples of two different transmit diversity techniques are delay diversity (DD) and space time coding (STC). This paper describes link and system level capacity gains achieved by these two types of transmit diversity techniques for two types of services. Focus is put on voice over the GSM/EDGE radio access network (GERAN) with different codec solutions, e.g., half-rate (HR) and quarter-rate (QR) AMR speech, but best-effort packet data is also addressed. The simulation results for voice show that the relative gain from STC is higher for QR than for HR. For best-effort packet data, only a small capacity gain can be achieved with STC while the user throughput at a given load can be increased significantly.