Sum-rate maximization of SCMA in multi-gateway satellite communication with on-board processing

Abstract

Satellite communication is anticipated to play a crucial role in 6G networks by providing widespread coverage. Given the limited spectrum and the extensive connectivity requirements of satellite communication, Sparse Code Multiple Access (SCMA) compared to orthogonal multiple access techniques such as Orthogonal Frequency Division Multiplexing (OFDM), allows more users to be accommodated within the same frequency resources. Although SCMA is a promising access technology that has been extensively studied in terrestrial communication but has seen limited application in satellite systems, particularly in multi-gateway satellite communication systems. This is due to the more complex interference management required in multi-gateway satellite systems, which includes both intra-gateway and inter-gateway interference. This paper focuses on the sum-rate optimization of a multi-gateway satellite communication system utilizing SCMA, comparing it with OFDM and Power Domain Non-Orthogonal Multiple Access (PD-NOMA) schemes. Specifically, we propose a phased optimization strategy that integrates SCMA with satellite on-board processing(OBP). Additionally, we examine the effect of imperfect Channel State Information at the Transmitter (CSIT) on the system’s sum-rate when gateways cannot acquire perfect CSIT. The simulation results demonstrate that the SCMA-based multi-gateway scheme can accommodate more users compared to OFDM but also achieves a higher system sum-rate compared to OFDM and PD-NOMA. These findings highlight the potential of SCMA in multi-gateway satellite communication systems. As the optimization variables are progressively refined, the system’s sum-rate improves, demonstrating the value of these variables, particularly when satellite OBP is utilized.