Beamforming and Combining in Multi-User Large MIMO Systems

We address the problem of beamforming and combining in a large multiple-input multiple-output systems in Rayleigh fading environment. A very large number of antennas, i.e., Ns are employed at the transmitter. Some fixed number of antennas, i.e., Nt are assigned to each user. A specific transmit weight/beamforming vector is used for transmitting the symbols of a particular user; and the user utilizes a specific combining vector for detecting the transmitted signal. Two different schemes are proposed to calculate beamforming and combining vectors. In first scheme, transmit weight vectors are chosen by using the principle of maximum ratio transmission; and maximum eigen value criterion is used for calculating the combining vector. In second scheme, the concept of null space is used for the calculation of combining vector. It is shown by simulations that proposed schemes works well and second scheme performs better than first scheme.