Space–Time Code Selection for Transmit Antenna Diversity Systems

In this correspondence, a space-time code selection approach for transmit antenna diversity (TAD) systems is proposed. The receiver compares the equivalent single-input-single-output channel envelopes with a set of predetermined threshold levels, decides the antennas to be used, and sends this information to the transmitter, which adjusts the space-time code to the number of selected antennas using a small amount of feedback information. Threshold levels are found out-of-line based on the Doppler frequency in such a way that channel state information outdate at the transmitter is taken into account. Analysis and simulation results show that the system performs well for a wide range of Doppler frequencies, outperforming transmit antenna selection techniques and adaptive TAD systems.