On the usage of antennas in MIMO and MISO interference channels

We investigate the performance of an uncoordinated 2 link MIMO interference channel as a function of the number of antennas and the average channel gains. The channel coefficients are random and uncorrelated, all links undergo Rayleigh fading, and the transmitters have no channel state information. The analysis is done in terms of ergodic capacity and outage probability. For non-asymptotic networks (i.e., when the number of transmit and receive antennas is finite and small), we derive upper and lower bounds to both our performance metrics. Moreover, the particular case of a MISO channel is considered, where exact expressions for the ergodic capacity, distribution of the capacity, and outage probability are derived. It is concluded theoretically, and somewhat surprisingly, that using all transmit antennas is not always optimal. That is, depending on the average channel gains and the requested communication rate, a transmitter should apply its antennas in different ways in order to minimize the outage probability.