Buffer-Aided Opportunistic Max^2-Min Network Coding for Wireless Data Broadcasting

In wireless broadcasting systems, lost packets are retransmitted to guarantee the correct reception of each packet. Traditional automatic retransmission request (ARQ) protocol retransmits one packet per slot, which leads to low spectrum efficiency. In this paper, we propose a buffer-aided opportunistic Max²-Min network coding (BOMNC) based wireless broadcasting (WBC) protocol. Specifically, to reduce the overall number of retransmissions, lost packets of different user equipments (UEs) are combined by performing Max²-Min network coding (NC) at the base station. Then, Max²-Min NC combined packets are broadcasted opportunistically to all the UEs. At each UE, lost packet within the correctly received decodable NC combined packets can be recovered by applying the proposed buffer-aided joint network recursive systematic convolution (RSC) decoder (BAJNRD). The correctly received undecodable NC combined retransmission packets are waited in the buffer for a future network decoding opportunity. Theoretical analyses and simulation results show that the proposed buffer-aided opportunistic Max²-Min NC based WBC protocol outperforms traditional NC based WBC protocol on the average number of transmissions performance.