Percentile-based contention window design for random access MIMO interference networks

This paper describes a new method for how interfering MIMO links might transmit more effectively in a random access network. We assume perfect transmitter-side channel state information, zero-forcing pre-coding to guarantee no interference on links that have already won access, and zero-forcing receiver processing at the still-contending links to suppress interference from the links that have already won. We define an effectiveness metric, the Instantaneous Equivalent SNR Percentile (IESP), in which the Equivalent SNR is the SNR of a single-input-single-output (SISO) link that would have the same capacity of a MIMO link after its interference constraints have been met and the IESP is the percentile of the Equivalent SNR, assuming independent Rayleigh fading. We propose that fairness among heterogeneous contending links be realized by giving the shorter contention window to the link with the higher IESP based on its own distribution, enabling links with few antennas to compete with links that have many antennas. Through simulation of the sum capacity of the winning set of links, the proposed contention window design is shown to provide a higher sum capacity than contention based on equal-sized windows.