NCOM: network coding based overlay multicast in wireless networks

The capacities of wireless networks are increasingly challenged by the traffic stresses generated by data-intensive applications. Multicast is a bandwidth-efficient solution to simultaneously disseminate data to multiple receivers. In this paper, we present NCOM, a network coding based overlay multicast design, that integrates network coding (NC), opportunistic routing (OR), and cross-layer link scheduling to achieve high efficiency and reliability in multi-hop wireless multicast. In NCOM, the source and receivers are connected by an overlay Steiner tree optimized for the minimum OR distance between nodes. With NC, coded packets are opportunistically transmitted along overlay links. The transmissions of adjacent nodes in the overlay multicast are coordinated by a novel multicast acknowledgement scheme and cross-layer MAC scheduling. We implement NCOM in OPNET by customizing the IEEE 802.11b modules. Through OPNET simulations, we demonstrate that NCOM can achieve a higher throughput and lower source transmission redundancy than the existing NC and OR based wireless multicast designs. NCOM can be easily deployed for efficient and reliable multicast in multi-hop wireless networks.