Courtesy piggybacking: supporting differentiated services in multihop mobile ad hoc networks

Due to the salient characteristics such as the time-varying and error-prone wireless links, the dynamic and limited bandwidth, the time-varying traffic pattern and user locations, and the energy constraints, it is a challenging task to efficiently support heterogeneous traffic with different quality of service (QoS) requirements in mulithop mobile ad hoc networks. In the last few years, many channel dependent mechanisms are proposed to address this issue based on the cross-layer design philosophy. However, a lot of problems remain before more efficient solutions are found. One of the problems is how to alleviate the conflict between throughput and fairness for different prioritized traffic, especially how to avoid the bandwidth starvation problem for low priority traffic when the high priority traffic load is very high. In this paper, we propose a novel scheme named courtesy piggybacking (CP) to address this problem. With the recognition of inter-layer coupling, our courtesy piggybacking scheme exploits the channel dynamics and stochastic traffic features to alleviate the conflict. The basic idea is to let the high priority traffic help the low priority traffic by sharing unused residual bandwidth with courtesy. Another noteworthy feature of the proposed scheme is its implementation simplicity: the scheme is easy to implement and is applicable in networks using either reservation-based or contention-based MAC protocols.