Leakage-based precoding algorithms for multiple streams per terminal MU-MIMO systems

Mobile networks rely extensively on multi-input multi-output (MIMO) communications to increase the data rate and improve signal quality. In multi-user MIMO (MU-MIMO) the signals are steered at the base station, forming multiple beams to the several user terminals (UTs). This is achieved by precoding the signals to be sent to the UTs. In leakage-based precoding, the precoding vectors are selected so that the signal to leakage plus noise ratio is maximized, where leakage is the amount of signal that is meant for a given UT but is received by the other UTs. This technique gives better results than techniques that completely eliminate the interference without regard to the signal or noise level (zero forcing solutions) like the block diagonal (BD) algorithm. However, current leakage-based algorithms are only optimal in the case of single-antenna UTs. In this paper, we propose simplified versions of these algorithms suitable for multiple streams per UTs, and compare its performance with existing solutions. Simulation results show an increase in performance. One of the versions does not require any Singular Value Decomposition (SVD) while the other does SVD of a much smaller matrix. Both still achieve better performance than the competition.