A Framework of Joint Scheduling and Network Coding for Real-Time Traffic with Diverse Delay Constraints

Network coding is a promising technology that can be used to effectively enhance the throughput of wireless networks. In realistic wireless networks, due to the random nature of wireless medium access and possible rate mismatch among different codeable flows, there may be insufficient packets to be coded together at intermediate nodes, which compromises the potential throughput gain by exploiting network coding. In this paper, we propose a joint scheduling and network coding (SNC) framework to maximize coding opportunity for real-time traffic flows with diverse delay constraints. SNC consists of two mechanisms: Delaying Packet Transmission Policy (DTP) and Network Coding Group (NCG) based Scheduling Policy (GSP). DTP dynamically decides whether to delay packet transmission of an NCG or not and adjusts the encoding degree. We formulate this problem as a finite-horizon Markov decision process to obtain the optimal encoding degree adaptation policy. Based on the results of DTP and delay requirements of real-time traffic flows, GSP calculates a weight for each NCG and schedules the coded packets of an NCG for transmission according to the weight. Simulation results demonstrate the effectiveness and advantages of SNC, compared with NC schemes using opportunistic policy and greedy policy.