Chapter 6
Medium Access Control for Opportunistic Routing—Candidate Coordination
One important and challenging issue in OR is candidate coordination. That is, in order to avoid duplication, we should ensure that only the “best” receiver of each packet forwards it. However, it is nontrivial to achieve this goal in an efficient way. The existing candidate-coordination schemes have some inherent inefficiency such as long time delay at each one-hop transmission and potential duplicate forwarding. Improperly designed coordination schemes will aggravate these problems and even overwhelm the potential gain provided by OR.
In this chapter, we carry out a comprehensive study on candidate coordination in OR and propose a new scheme, “fast slotted acknowledgment” (FSA), to further improve the efficiency of OR. This adopts a single ACK to confirm successful reception and suppresses other candidates' attempts to forward the data packet with the help of a channel-sensing technique. We also confirm the benefit of our scheme by simulation. The result shows that FSA can reduce the average end-to-end delay by up to 50% when the traffic is relatively light and can improve the throughput by up to 20% under a heavy traffic load.
The rest of this chapter is organized as follows. Section 6.1 reviews state-of-the-art coordination schemes in detail. Section 6.2 presents FSA's design and analysis. This is followed by Section 6.3, where evaluation and analysis of FSA performance are presented. Section 6.4 ...
