Design and Analysis of Bidirectional Relaying NCed-HARQ Transmission Scheme for S-IoT

Satellite-based Internet of Things (S-IoT) with next generation high-throughput satellites (HTS) is suggested to realize the increasing demand of terrestrial communications for beyond fifth generation (B5G), and even in sixth generation (6G) mobile system. In this paper, we propose a network coded hybrid automatic repeat request (NCed HARQ) transmission scheme for S-IoT to further improve the throughput and efficiency. First, we illustrate a thorough coding/decoding process of NCed HARQ in the case of two terrestrial nodes and detail the transmission flows in two typical bidirectional relaying scenarios. Then we derive the system throughput in a matrix exponential distribution form to make formulations more concise and unified. At last, simulation results show that our NCed-HARQ transmission scheme can enhance the throughput, and there is an optimal value of transmission rate that maximize the throughput when the average SNR is fixed.