A queueing theoretic model for opportunistic network coding

In this paper, we consider a scenario in which two users communicate via a single access point with two buffers using network coding. We focus on the particular situation when there are no packets in one of the buffers for network coding to proceed. In this case, there is a trade-off between the delay due to waiting for a coding opportunity and the increased efficiency of spectrum access due to network coding. In order to analyze this situation, we develop an analytical model for the system using a discrete time Markov chain (DTMC). The packet arrivals for any general arrival distribution are modeled as a discrete time Markovian arrival process (DMAP). We then find the age distribution of the waiting packets and hence determine the waiting-time which achieves the optimal trades-off between spectrum access efficiency and packet delay.