Side-Information-Aware FFMA over GF$(p)$ for Efficient Coded Retransmission

Abstract

In multiuser wireless broadcast systems, conventional schemes suffer from low retransmission efficiency. To reduce the retransmission delay, this paper proposes a Side-Information-Aware Finite-Field Multiple Access (SIA-FFMA) coded retransmission scheme. Under a fully-online feedback mode, the proposed scheme exploits the state feedback matrix to capture the Has/Wants sets of each user equipment (UE), and adaptively determines the concurrent subset in each encoded retransmission round through a greedy packet selection algorithm. At the base station (BS), multiple missing packets are encoded over a prime field $\operatorname{GF}(p)$ using additive-inverse element pairs (AI-EPs) and then transmitted through finite-field multiplexing. At the UE side, the already available packets are used as side information to reduce the detection candidate set, enabling the joint recovery of multiple unknown packets. Simulation results show that, in high packet-loss scenarios, SIA-FFMA effectively reduces both the completion delay and the average decoding delay compared with automatic repeat request (ARQ) and instantly decodable network coding (IDNC).