Delay-Limited Performance Analysis of NOMA-enabled Satellite Internet of Things

With great potential to support ubiquitous services in large footprint areas, satellite internet of things (S- IoT) is attracting increasing attentions in sixth-generation (6G) wireless communication networks. However, the increasingly growing number of applications and services of S-IoT is rapidly exhausting the limited spectral resources. In this case, this paper introduces a non-orthogonal multiple access (NOMA) scheme, which can simultaneously serve multiple users in power domain, in the S-IoT to further improve the utilization of radio spectrum. Moreover, taking into account the S-IoT applications with various delay quality-of-service (QoS) requirements, the concept of effective capacity is employed and delay-limited performance for the NOMA-enable downlink S-IoT is studied. Specifically, the exact closed-form expressions as well as low-SNR and high-SNR approximations of effective capacities for each NOMA user are all derived. Simulations are provided to show the advantage of introducing the NOMA scheme in the S-IoT system, the impact of delay-QoS requirements on users' performance, and the effects of various power allocation strategies on the performance of the considered network.