I.A. Mukhin, M.S. Nemirovskiy

This article is devoted to determining of conditions under which effective using of spatial multiplexing based on the using of MIMO (multiple input multiple output) technology in systems such as WiFi and WiMAX is possible. Analysis will be conducted on an example of V-BLAST technology with 4 receiving and 4 transmitting antennas. Accordingly, the radio link is described by a matrix of dimension 4x4, which consists of complex transmission coefficients for all pairs of transmitting and receiving antennas. The paper consists of two parts. In the first part the influence of the properties of the channel matrix on the possibilities of spatial multiplexing regardless of the opportunities of realization such matrices on various radio links is investigated. In the second part the possibilities of such implementation are estimated by means of simulation in MatLab of radio links with various lengths and with different numbers of reflecting and absorbing screens. Energy losses are also considered. Thus it appears that desirable matrixes can be realized only for the radio links satisfying defined enough severe conditions. The main qualitative result of the work comes to conclusion that using of multiantenna systems for spatial multiplexing in real conditions is effective only for a sufficiently large number of rays and only at relatively small distances of communication.