  The traditional TCP congestion control mechanism encounters a number of new
problems and suffers a poor performance when the IEEE 802.11 MAC protocol is
used in multihop ad hoc networks. Many of the problems result from medium
contention at the MAC layer. In this paper, I first illustrate that severe
medium contention and congestion are intimately coupled, and TCP s congestion
control algorithm becomes too coarse in its granularity, causing throughput
instability and excessively long delay. Further, we illustrate TCP s severe
unfairness problem due to the medium contention and the tradeoff between
aggregate throughput and fairness. Then, based on the novel use of channel
busyness ratio, a more accurate metric to characterize the network utilization
and congestion status, I propose a new wireless congestion control protocol
(WCCP) to efficiently and fairly support the transport service in multihop ad
hoc networks. In this protocol, each forwarding node along a traffic flow
exercises the internode and intranode fair resource allocation and determines
the MAC layer feedback accordingly. The endtoend feedback, which is ultimately
determined by the bottleneck node along the flow, is carried back to the source
to control its sending rate. Extensive simulations show that WCCP significantly
outperforms traditional TCP in terms of channel utilization, delay, and
fairness, and eliminates the starvation problem.
