| Summary: | 碩士 === 國立交通大學 === 資訊科學系 === 89 === Fair scheduling in wireless networks is significantly different
from that in wireline networks because of location-dependent and
bursty channel errors. The wireless media may experience a
substantial rate of link errors that cause the loss of link
capacity. In addition, the base station which performs scheduling for both uplinks and downlinks has only limited knowledge of the mobile host's channel conditions. This results in a great challenge to provide quality of service (QoS) in wireless networks. In this thesis, we present an adaptive weighted fair queueing algorithm (AW-FQ) which can provide better QoS for error-prone flows and does not need to predict the channel quality of packet transmission in the wireless environment. The weight of a flow is dynamically adjusted according to the experienced packet error rate. Every flow is guaranteed to receive the minimal tolerable quality of its original service when experiencing channel errors. Since the wireless environment is unreliable, AW-FQ is suitable for applications that need different minimal QoS requirements. In AW-FQ, each flow is individually assigned a virtual flow which does not always occupy a fixed fraction of the bandwidth. The virtual flow can provide additional service for other error-free flows and compensate the flow which it is assigned to. The amount of service degradation of a flow can be administratively controlled within a predefined tolerable ratio when the flow provides compensation. Simulation results show that our approach can guarantee throughput and fairness. Compared to
the server based fairness approach (SBFA), AW-FQ has better
queueing delay bound and does not have to assign a fixed flow
which always occupies a fixed fraction of the bandwidth for
providing compensation.
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