User Grouping and Scheduling in OFDMA-NOMA for Industrial Communication: A Low Latency Throughput-aware Approach

Future wireless networks demand very high-speed and reliable connectivity to realize smart industrial and manufacturing systems. Furthermore, there has been a tremendous growth in the number of connected sensors and devices, requiring efficient utilization of radio resources. To achieve this, we propose a user grouping and scheduling framework for hybrid multiple access scheme that combines non-orthogonal multiple access (NOMA) with orthogonal frequency division multiple access (OFDMA). First, we analyse the impact of channel gain difference among a group of power domain NOMA users on the bit error rate (BER) performance and achieved throughput. Based on the analysis, we develop a throughput-aware user grouping scheme for multiple ultra reliable low latency communication (URLLC) users, each with its own demanded throughput, taking the channel gain differences into consideration. For low latency operation, we propose a scheduling method that aims to minimize the number of utilized time slots, for a given bandwidth. The proposed scheme is evaluated in terms of BER, achieved throughput, and fairness of the grouped users to indicate that it fulfils the demanded throughput of each user, while providing lower latency compared to OMA only scenario. It is shown that OFDMA-NOMA with the proposed scheme outperforms a previously proposed user pairing scheme for uplink NOMA.