TO STUDY AND COMPARISON OF VARIOUS BEAMFORMING TECHNIQUES FOR MULTIUSER MIMO-OFDM SYSTEM

Abstract

This paper consists three techniques of beamforming for MIMO systems base on iterative finding of transmit and receive beamformers.In the first case the transmit beamformers are set (known) and the receive beamformers are calculated. It works by projecting the Tx beamformers into a null space of appropriate channels. This eliminates one interference term for each user. The basic idea is to optimize SNR ratio taking into account the orthogonality so as to reduce interference. In the next case we simultaneously optimize the Tx and Rx beamformers from constrained SNR maximization. It uses the results from the previous case. The third case is also for joint optimization of Tx–Rx beamformers but combines constrained SNR and signal to-interference-plus-noise ratio maximization. The minimum number of antennas required is derived as part of the formulation. A precoder is used for extracting multipath diversity.At last; the required feedback rates are derived and compared to existing beamforming methods. Using the standardized statistical channel model for IEEE 802.11n, our  imulations demonstrate faster beamforming, improved error performance, and the ability to extract multipath diversity which is not possible in the leastsquare approach.