Adaptive network coded retransmission scheme for wireless multicast

In wireless multicast, the receivers are interested in obtaining only a subset of the packets transmitted by the access node. Consequently, it is intuitively assumed that random network coded packet retransmissions will result in a lower bandwidth efficiency compared to opportunistic network coded retransmissions as the former involves the delivery of unwanted packets. In the first part of this paper, we show, through simulations, that the random network coded retransmission (RNCR) scheme outperforms the opportunistic network coded retransmission (ONCR) scheme in terms of bandwidth efficiency in a wide range of multicast settings. Motivated by this result, we propose an adaptive algorithm that can dynamically select, from the RNCR and ONCR schemes, the one that is expected to achieve a better performance for each multicast frame. Simulation results show that the proposed algorithm almost achieves the optimal performance that can be obtained by combining these two retransmission schemes.