A Novel Scheme for QoS-Aware Resource Pooling and Uncoordinated Allocation in Grant-Free NOMA

Although grant-free non-orthogonal multiple access (GF-NOMA) has arisen as an efficient resource allocation strategy for energy-constrained Internet of Things (IoTs) with minimal resource allocation process; it suffers from uplink collisions in random access and degraded quality of service (QoS). The uplink collisions impact uniformly all types of devices due to equal opportunity for resource selection, resulting in degraded overall performance, especially for IoT devices with high priority and emergency services. In this letter, QoS-aware GF-NOMA: a novel QoS-aware resource allocation strategy is proposed to make GF-NOMA versatile and adaptive to the environment. It is proposed that the base station create QoS-aware resource pools and the uncoordinated IoT devices identify their appropriate resources, thus providing control on priority resource allocation for emergency services. The numerical analysis and Monte Carlo simulations corroborate our claim that the proposed scheme reduces the average collision probability by approximately $10\sim 30\%$ for all participating devices.