Abstract

Distributed opportunistic scheduling (DOS) techniques have been recently proposed for improving the throughput performance of wireless networks. With DOS, each station contends for the channel with a certain access probability. If a contention is successful, the station measures the channel conditions and transmits in case the channel quality is above a certain threshold. Otherwise, the station does not use the transmission opportunity, allowing all stations to recontend. A key challenge with DOS is to design a distributed algorithm that optimally adjusts the access probability and the threshold of each station. To address this challenge, in this paper, we first compute the configuration of these two parameters that jointly optimizes throughput performance in terms of proportional fairness. Then, we propose an adaptive algorithm based on control theory that converges to the desired point of operation. Finally, we conduct a control theoretic analysis of the algorithm to find a setting for its parameters that provides a good tradeoff between stability and speed of convergence. Simulation results validate the design of our mechanism and confirm its advantages over previous works.

Highlights

  • INTRODUCTIONC OMMUNICATION over wireless channels faces two main challenges inherent to the medium: interference and fading

  • C OMMUNICATION over wireless channels faces two main challenges inherent to the medium: interference and fading. While the former has traditionally been tackled at the MAC layer, the latter has largely been considered as a physical layer problem

  • We observe that ADOS significantly outperforms all other approaches and that this effect becomes more accentuated as the throughput of the non-saturated stations decreases

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Summary

INTRODUCTION

C OMMUNICATION over wireless channels faces two main challenges inherent to the medium: interference and fading. We significantly extend the performance evaluation of the mechanism: (i) In addition to comparing ADOS to the team-game approach (TDOS) proposed in [5], we compare it against the non-cooperative approach (NDOS) of [5] and CSMA/CA, and show that it outperforms TDOS, but it performs far better than NDOS and CSMA/CA This result is very relevant because ADOS, NDOS and CSMA/CA use only local information whereas TDOS requires global information (and involves substantial signaling). (ii) In addition to analyzing and validating the configuration of the algorithm to adapt the thresholds to changing radio conditions, we compare its performance with the algorithm we presented in [1] for a mobile scenario with different speeds and number of stations.

DOS OPTIMAL CONFIGURATION
System Model
Optimal pi configuration
ADOS MECHANISM
Adaptive algorithm for Ri
CONTROL THEORETIC ANALYSIS
Analysis of the algorithm for pi
Analysis of the algorithm for Ri
PERFORMANCE EVALUATION
Homogeneous scenario
Heterogeneous scenario
Performance under realistic models
Validation of the configuration proposed for ADOS
Moving Stations
IMPLEMENTATION ISSUES AND CHALLENGES
Findings
CONCLUSIONS
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