Abstract

It is well known that TCP performs poorly in wireless mesh networks. There has been intensive research in this area, but most work uses simulation as the only evaluation method; however, it is not clear whether the performance gains seen with simulation will translate into benefits on real networks. To explore this issue, we have implemented ATP (Ad-hoc Transport Protocol), a transport protocol designed specifically for wireless ad hoc networks. We have chosen ATP because it uses a radically different design from TCP and because reported results claim significant improvement over TCP. We show how ATP must be modified in order to be implemented in existing open-source wireless drivers, and we perform a comprehensive performance evaluation on mesh testbeds under different operating conditions. Our results show that the performance of ATP is highly sensitive to protocol parameters, especially the epoch timeout value. To improve its performance we design an adaptive version that utilizes a self-adjustable feedback mechanism instead of a fixed parameter. A comprehensive measurement study demonstrates the advantages of our adaptive ATP under various operating conditions. For networks with high bit-rate, low quality links, our adaptive version of ATP demonstrates an average of more than 50% gain in goodput over the default ATP for a single flow case. With respect to fairness, the adaptive ATP generally outperforms the default ATP by an order of magnitude in most results.

Degree

College and Department

Physical and Mathematical Sciences; Computer Science

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