On Bit-Rate Selection for Opportunistic Routing

Opportunistic routing (OR) schemes, such as ExOR, have been shown to provide significant throughput gains over traditional best-path routing schemes for wireless networks. Though the performance of OR schemes depend on the bit-rate, they currently use a fixed rate for transmitting packets. While several schemes have been proposed for selecting bit-rate for unicast transmission to a single receiver, none of them are suitable for broadcast transmission to multiple receivers under OR. This paper attempts to maximize the benefits of OR with dynamic bit-rate selection. We first define a new metric, expected anypath communication time (ExACT), that captures the time to deliver a packet to destination with a given rate at each hop under OR. We then propose bit-rate selection for opportunistic routing (BitSOR) algorithm that minimizes ExACT for each pair of nodes in the network. We evaluate the performance of BitSOR using MIT Roofnet trace and demonstrate significant potential improvement with dynamic rate over OR with the best fixed rate.