Multihop Wireless Networks: Opportunistic Routing

5.1 Introduction

With the spur of modern wireless technologies, a promising way to improve the system throughput is to allow more concurrent transmissions by installing multiple radio interfaces on one node with each radio tuned to a different orthogonal channel (Alicherry et al. 2005; Kodialam and Nandagopal 2005; Zhang et al. 2005). Other than the multiradio multichannel technology, opportunistic routing (OR) also shows its potential for significantly improving network throughput (Biswas and Morris 2005; Chachulski et al. 2007; Dubois-Ferriere et al. 2007; Fussler et al. 2003; Shah et al. 2004; Zeng et al. 2008; 2007a,b,c; Zhong et al. 2006). Opportunistic routing is a network-MAC cross-layer design, which involves multiple forwarding candidates at each hop, and the actual forwarder is selected after packet transmission according to the instant link reachability and availability. It is quite different from the traditional routing (TR) in that only one pre-selected next-hop node is involved to forward packets at each hop.

When integrating these two techniques, an interesting question arises: “what is the end-to-end throughput bound of the multi-radio multi-channel network when OR is available?” In this chapter, we will propose a methodology to answer this question. However, it is a nontrivial task.

First, unlike TR, OR has a unique quality in that for each packet transmission, any one of the forwarding candidates of the transmitter can become the actual forwarder. Thus, effective ...