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.

I. Introduction

Transmit antenna diversity (TAD) is expected to contribute to providing the high data rates needed by third- and fourth-generation wireless systems. To use several transmitter antennas at the same time, different schemes have been proposed; among them, Tarokh et al. proposed the space–time trellis coding [1]. Later, Alamouti [2] proposed the space–time block code (STBC) for two-transmitter antennas, which was generalized by Tarokh et al. to an arbitrary number of antennas [3]. These space–time codes were designed under the assumption that channel state information (CSI) was not available at the transmitter end.