Performance of suboptimal beamforming with full knowledge of part of the channel matrix

Multiple antenna techniques are used to enhance wireless links and therefore have been studied extensively. Many practical systems differ from the ideal schemes discussed in the literature. One example is the lack of precise channel information at the transmitter. We evaluate analytically the performance of a beamforming technique that uses partial channel knowledge. Specifically, we analyze a suboptimal M ×N scheme employing Maximal Ratio Transmission at the transmitter and MRC at the receiver, assuming only one out of M rows of the channel matrix is known at the transmitter. We show that the diversity order and array gain of such a scheme is M+N -1. The performance of this scheme, which is supported by both Worldwide Inter-operability for Microwave Access (WiMAX) and Long Term Evolution (LTE) systems, is identical to that of an MRC system with M+N -1 antennas. All the results are supported by simulations.