Performance Analysis of Network Coding With Virtual Overhearing in Wireless Networks

Due to the broadcast nature of wireless channels, overhearing plays an important role in interflow network coding in that it serves as a way to acquire the side information for the decoding of network-coded packets. Since overhearing only takes effect in the one-hop neighborhood of nodes, it, in turn, restricts the identification of network coding opportunities. That is, if the side information for packet decoding cannot be overheard, no coding opportunity can be identified. Hence, in this paper, we aim to relax such a restriction to further explore network coding opportunities. Specifically, we propose a virtual overhearing (VOH) technique to enable network coding when the side information cannot be obtained from traditional overhearing previously mentioned. VOH allows a node to obtain a packet sent by another node that can be two or more hops away. As a result, VOH can serve as a supplementary way for side information acquirement, thus still enabling network coding between network flows when traditional overhearing is not possible to obtain the needed side information. The additional coding opportunities brought by VOH can be translated into additional performance gains. We first analyze network coding with VOH in a simple topology and show that with VOH, network capacity could be improved by over 12% (in some situations, network throughput could be improved by 50%). Then, we conduct simulations in NS-2 to show the advantage of VOH.