Robust Link Adaptation in Multiantenna URLLC Systems with Flashlight Interference

We present a robust link-adaptation method to realize ultra-reliable and low-latency communications (URLLC) against flashlight, i.e., on-off interference. A robust link-adaptation method is presented based on the measured signal-to-interference plus noise ratio (SINR) at the URLLC user, which varies between the time when interference power is measured and the time of payload transmission. We obtain the statistical distribution of the change of SINRs between two consecutive time slots and devise backoff methods guaranteeing the reliability of transmissions against flashlight interference. We derive the average transmission rate over Rayleigh fading channels in the considered system model. We observe that in the presence of flashlight interference, a strict reliability requirement reduces the transmission rate to a small fraction of the best effort service rate. When increasing the number of antennas at both the serving and interfering transmitters, the increase in array gain is partially compromised by the increased backoff needed to guarantee reliability. All analytical results are verified via Monte Carlo simulation.