Beamforming with partial channel knowledge

Multiple antenna techniques are used to enhance wireless links and therefore have been studied extensively. Many practical systems differ from ideal schemes which have been discussed in the literature. One example is a system that lacks precise channel information at the transmitter. We evaluate analytically the performance of a multiple input multiple output (MIMO) technique that uses partial channel knowledge. Specifically, we analyze a suboptimal M × N scheme employing Eigenbeamforming at the transmitter and MRC at the receiver, assuming only partial channel matrix is known to the transmitter, specifically only P out of N rows of the channel matrix are known. We show that the diversity order of such a scheme is MP + N - P and further show that increasing the value of P by one increases the diversity order by M - 1. We also derive the array gain for this scheme. All the results are supported by simulations.