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.