Spatial MIMO Rank Modulation

A transmission technique, referred to as spatial multiple-input multiple-output (MIMO) rank modulation (SMRM), is proposed that uses multiple spatial domains only in order to convey information to the receiver. These multiple spatial domains are collectively referred to as ranking domain. In SMRM, the number of active transmit antennas or the rank of each spatial domain is determined by the structure of random information input bits. The input information bit stream is sent into the ranking modulator. Instead of detecting the channel index, the receiver detects the number of paths of the received radio frequency (RF) signals. In SMRM, the transmitted signals are preset and known at the receiver. Only the rank information is used to decode the bits in the ranking domain. In addition, we derive analytical upper bounds on bit error probability (BEP) of the SMRM system based on principal component analysis (PCA) of the sample covariance of the signals in the detector. Analytical results are then compared with simulation results at different data rates which show tractable performance. In fact, for better security operations, the SMRM system has the additional benefit that the wireless channel does not completely modulate spatial information, but spatial information is also modulated by the number of RF chains.