Downlink Multiuser Detection of Ultra-Low Latency Virtual-Cell Vehicular Networks

Abstract

Forming small virtual cells by using open-loop radio communications and proactive network association has been recently shown effective to realize the ultra-low latency vehicular networking. However, multiple access emerges as another technical challenge, particularly in the downlink losing perfect synchronization for proactive radio access. Traditional beam-forming and interference alignment (IA) to suppress intercell interference could not satisfy ultra-low latency vehicular networking to enable autonomous vehicles due to the difficulty of obtaining channel state information (CSI) in open-loop communications. Multiuser detection (MUD) shall be employed in the downlink to accommodate interference from multiple co-existing virtual cells. By looking into bit-error rate (BER) in terms of power and modulation order of interference, we note that the performance gap between maximum likelihood-MUD (ML-MUD) and ideal single-user detection (SUD) heavily depends on the modulation schemes adopted by interferers. This modulation sensitivity can be easily relieved by introducing multi-antenna technique, which suggests robustness against multiple-access interference by diversity.