Practical opportunistic routing in wireless mesh networks

Wireless mesh network is usually used to provide Internet access to communities or citywide. Opportunistic Routing (OR) exploits overheard packets in a wireless network and has been proven to be effective for wireless mesh networks. However, the existing OR protocols cannot meet all the requirements for high-speed, multi-rate wireless mesh networks, including: running on commodity Wi-Fi interface, low complexity, supporting multiple link layer data rates, and exploiting partial packets. We propose POR, a new Opportunistic Routing protocol that is the first OR protocol to meet all the critical requirements in practical wireless mesh networks.;POR forwards individual packets and does not forward a packet if it has been already received correctly by the downstream nodes according to the feedback sent by the downstream nodes. The individual packet forwarding of POR makes it more friendly with popular protocols such as TCP than existing opportunistic routing protocols that requires packet batching. POR incorporates a block-based partial packet recovery scheme by retransmitting corrupted parts of the packet. POR employs a multi-hop link rate adaptation scheme to adapt to the wireless channel conditions by selectively probing rates that are potentially better with small dummy packets. POR also employs a new path metric that considers the cost in sending feedbacks as well as the capability of the nodes to select appropriate rates to track the channel conditions.;POR is a software-only solution. We implement POR within the Click modular routing and our experiments in a 16-node wireless testbed confirm that POR achieves significantly better performance than the compared protocols. We run TCP on top of POR and results show that POR can achieve higher TCP throughput than the compared protocol, which is the first demonstration of TCP on top of any OR protocols.