Distributed packet scheduling for multihop flows in ad hoc networks

In wireless multihop ad hoc networks, nodes need to contend for the shared wireless channel with their neighbors, which could result in congestions and greatly decrease the end-to-end throughput clue to severe packet loss. Several recent papers have indicated that the IEEE 802.11 fails to achieve the optimum schedule for this kind of contentions. In this paper, we present a framework of multihop packet scheduling to achieve maximum throughput for traffic flows in the shared channel environment. The key idea is based on the observation that in the IEEE 802.11 MAC protocol the maximum throughput for chain topology is 1/4 of the channel bandwidth and its optimum packet scheduling is to allow simultaneous transmissions at nodes which are four hops away. The proposed fully distributed scheme generalizes this optimum scheduling to any traffic flows which may encounter infra-flow contentions and inter-flow contentions. Extensive simulations indicate that our scheme could perform well and achieve high throughput at light to heavy traffic load while the performance of the original IEEE 802.11 MAC protocol greatly degrades when the traffic load becomes heavy. Moreover, our scheme also achieves much better and more stable performance in terms of delay, fairness and scalability with low and stable control overhead.