Dimensionality constraints imposed by highly frequency selective channels on MIMO-FBMC/OQAM systems

This paper investigates the application of MIMO to the FBMC/OQAM scheme in highly frequency selective channels. The system model that is considered in this work does not make any assumption about the flatness of the channel. In this scenario, it is definitely challenging the design of MIMO precoding and decoding matrices that succeed in removing the interference. In this regard, we have derived the degrees of freedom, in terms of number of streams (S), transmit (NT ) and receive (NR) antennas, required to eliminate the unwanted signals. The analysis reveals that in some multi-antenna configurations some residual interference should be expected. In this case, we have further studied existing low-complexity solutions that solve optimization problems that depend on the MSE. Numerical results show that the sum-rate in FBMC/OQAM is on pair with OFDM when NR - 1 = NT = S = 2. This result is relevant because the adoption of FBMC/OQAM brings substantial improvements with respect to OFDM in a variety of contexts.