MCS Selection for Multi-Connectivity and eMBB-URLLC Coexistence in Time-Varying Frequency-Selective Fading Channels

Multi-connectivity, in which multiple base stations (BSs) cooperate and jointly transmit to a user, enables a 5G cellular system to meet the challenging reliability requirements of downlink ultra-reliable and low-latency communications (URLLC) traffic. We derive insightful expressions for the achievability, which is the probability that the URLLC user's reliability requirement is met by multi-connectivity. We then propose a low-complexity algorithm to jointly select the set of cooperating BSs and modulation and coding scheme (MCS) to minimize the throughput loss incurred by enhanced mobile broadband (eMBB) users whose time-frequency resources are punctured to carry URLLC data. For time-varying channels with feedback delays, we present a new stochastic reliability requirement for URLLC traffic. The MCS selected on the basis of this requirement markedly increases the probability of meeting the block error rate (BLER) target over the grid of URLLC user locations.