Multihop wireless ad hoc networks are useful in an infrastructure-less environment because it is possible to deploy a network rapidly over a large area. A key issue of multihop wireless networks is that the quality of a multihop connection is vulnerable to various factors such as fading wireless channels, interference among neighbor links, packet collision due to hidden terminals, and so on. These problems get worse when multiple flows coexist in an ad hoc network, since a deteriorated flow can block other flows. This paper proposes a transmission scheduling mechanism for multiple flows in an ad hoc network to mitigate the impact of a deteriorated flow on the total throughput.

A key idea of the proposed mechanism is that it prevents automatic retransmission of failed packets in the media access control (MAC) layer. Instead, a scheduler selects a flow to have opportunity for transmission based on the estimated link quality, goodput, and fairness. This method allocates more bandwidth of a common link to a better flow than a deteriorated flow so that the overall throughput can be increased. In addition, the authors propose two algorithms that take the estimated throughput and the fairness index with adjustable weights or constraint. The experimental results show the proposed mechanism can effectively increase throughput and fairness.

The main contribution of this paper is demonstrating the proposed framework to effectively prevent the MAC layer blocking problem in a testbed. The evaluation section studies the impact of the mechanism in normal traffic and overloaded traffic environments with various parameter values such as weight of fairness. However, the proposed mechanism will be applicable only for static multihop connections without broken links. Since a deteriorated flow has less opportunity of transmission and a longer time will be taken to reach the maximum retransmission tries, a broken link detection will be delayed.