Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit
IEEE/ACM Transactions on Networking (TON)
A rate-adaptive MAC protocol for multi-Hop wireless networks
Proceedings of the 7th annual international conference on Mobile computing and networking
Opportunistic media access for multirate ad hoc networks
Proceedings of the 8th annual international conference on Mobile computing and networking
Goodput Analysis and Link Adaptation for IEEE 802.11a Wireless LANs
IEEE Transactions on Mobile Computing
Effect of Hidden Terminals on the Performance of IEEE 802.11 MAC Protocol
LCN '98 Proceedings of the 23rd Annual IEEE Conference on Local Computer Networks
IEEE 802.11 rate adaptation: a practical approach
MSWiM '04 Proceedings of the 7th ACM international symposium on Modeling, analysis and simulation of wireless and mobile systems
Self-management in chaotic wireless deployments
Proceedings of the 11th annual international conference on Mobile computing and networking
Using emulation to understand and improve wireless networks and applications
NSDI'05 Proceedings of the 2nd conference on Symposium on Networked Systems Design & Implementation - Volume 2
Adaptive multirate auto rate fallback protocol for IEEE 802.11 WLANs
MILCOM'06 Proceedings of the 2006 IEEE conference on Military communications
Performance analysis of the IEEE 802.11 distributed coordination function
IEEE Journal on Selected Areas in Communications
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IEEE 802.11 wireless network supports multiple link rates at the physical layer. Each link rate is associated with a certain required Signal-to-Interference-and-Noise Ratio (SINR) threshold for successfully decoding received packets. Suppose constant noise and no power adjustment strategy exists, apparently SINR is solely affected by the accumulated interference power level I. The method of selecting an appropriate link rate for transmitting/retransmitting packets is generally known as the link adaptation mechanism. Traditional link adaptation approaches try to reduce the transmit rate (hence lower SINR threshold is required) on transmission failures (potentially due to the increased denominator I of SINR), whereas upgrade the transmit rate (hence higher SINR threshold is required) on successful transmissions (potentially due to the decreased denominator I of SINR). The accumulated interference power level I in some sense indicates the medium congestion status. In 802.11, on transmission failures, the DCF performs a binary exponential backoff mechanism to discourage channel access attempts, hoping to reduce congestion. When traditional link adaptation is applied, both rate reduction and binary backoff represent double penalties for this wireless link, which may cause overly conservative transmission attempts. On the other hand, once transmission succeeds, 802.11 DCF resets the backoff contention window to the minimum value to encourage channel access attempts. At the same time, traditional link adaptation may also decide to increase the data rate, which leads to overly aggressive transmission attempts. We observe this improper interaction of link rate and backoff mechanism that harms the 802.11 system performance, due to separate consideration of those two parameters. In this paper, rather than independently dealing with the two parameters, we propose to perform link adaptations by firstly considering if a proper backoff window has been reached. Specifically, if the medium congestion level I can be reduced by imposing a larger backoff window on transmissions, then there may be no need to decrease the link rate, given SINR can be sustained. Conversely, if there is extra interference that may be tolerated in I, a smaller back-off window can be used to encourage more transmission activities while keeping the required SINR. In particular, a joint Adaptation of link Rate and backoff Contention window, abbreviated as ARC, is devised. Our ARC protocol first estimates the optimal contention window (optCW) based on Calí's approximation methods. On transmission successes (failures), the current contention window size cwp should be compared with optCW. If cwp optCW (cwp p is decreased (increased) to perform more aggressive (conservative) transmission attempts while leaving the link rate R unchanged. Otherwise, R is upgraded (reduced) to the next higher (lower) rate. One nice property of ARC is the ability to intelligently maintain link stability, avoiding unnecessary rate fluctuations. Simulation results show that the proposed ARC protocol outperforms several traditional link adaptation mechanisms. We also propose an analytic Markov chain model on ARC operations for performance validation.