The article is devoted to the efficiency rating of the differential space-time block coding (DSTBC). The encoding scheme is based on the technology of Multiple Input Multiple Output (MIMO) and relative phase modulation principle, which does not require knowledge of channel state information by the receiver on some minor assumptions. Simulation of the encoding/decoding scheme is executed in MATLAB software package for different numbers of antennas on transmitting and receiving sides.  It is known that application of methods of space-time coding in MIMO systems allows to raise their noise immunity and spectral efficiency. At the same time, it is necessary to know a current state of a link channel on the receiving side; due to it, a coherent reception can be implemented. Information on the channel state can be received when transferring pilot signals that are known beforehand on the receiving side, however such method is not always rational, and sometimes it is challenging because of many factors. Therefore, there is an interest in transmission schemes that do not require knowledge of link channel state from the receiver or transmitter.  In traditional communication systems, there is a way to deal with unknown link channels. This method involves using the differential phase shift keying (DPSK), application of which does not require knowing of the channel [1]. Currently, a significant amount of researches of differential schemes was conducted based on various methods [2-3]. Let us consider the case of expansion of these systems when using differential space-time coding.  Results of simulation are given for BPSK and QPSK modulations and various number of receiving and transferring antennas. In each case, the Rayleigh fading channel was used and it was sustained permanent only within a transmission of one frame consisting of several blocks, but it changed in a random manner from frame to frame. Conclusions. Here is presented an expanded DSTBC method based on the principle of differential coding which allows absence of channel information on receiving and transferring sides.