Performance anomaly of 802.11b
Performance anomaly of 802.11b
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DOI：
10.1109/infcom.2003.1208921
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发表时间：
2003-07
期刊：
影响因子：
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通讯作者：
Gilles Berger-Sabbatel;F. Rousseau;M. Heusse;A. Duda
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文献类型：
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作者：
Gilles Berger-Sabbatel;F. Rousseau;M. Heusse;A. Duda
分析了IEEE802.11b无线局域网的性能。我们观察到，当某些移动主机使用比其他主机更低的比特率时，所有主机的性能都会显著降低。这种情况在无线局域网中很常见，其中远离接入点的主机会受到重要的信号衰落和干扰。为了解决此问题，主机更改了其调制类型，从而将其比特率降级到某个较低的值。通常，当检测到反复不成功的帧传输时，802.11b产品会将比特率从11 Mb/S降至5.5、2或1 Mb/S。在这种情况下，例如以1Mb/S发送的主机将以11Mb/S发送的所有其他主机的吞吐量降低到低于1Mb/S的低值。基本的CSMA/CA信道接入方法是这种异常的根源：它保证了对所有主机的相同的长期信道接入概率。当一台主机因其比特率较低而长时间捕获该信道时，会对使用较高速率的其他主机造成不利影响。通过推导有效吞吐量的简单表达式，从理论上对异常进行了分析，并通过仿真进行了验证，并与几种性能测量结果进行了比较。
The performance of the IEEE 802.11b wireless local area networks is analyzed. We have observed that when some mobile hosts use a lower bit rate than the others, the performance of all hosts is considerably degraded. Such a situation is a common case in wireless local area networks in which a host far away from an access point is subject to important signal fading and interference. To cope with this problem, the host changes its modulation type, which degrades its bit rate to some lower value. Typically, 802.11b products degrade the bit rate from 11 Mb/s to 5.5, 2, or 1 Mb/s when repeated unsuccessful frame transmissions are detected. In such a case, a host transmitting for example at 1 Mb/s reduces the throughput of all other hosts transmitting at 11 Mb/s to a low value below 1 Mb/s. The basic CSMA/CA channel access method is at the root of this anomaly: it guarantees an equal long term channel access probability to all hosts. When one host captures the channel for a long time because its bit rate is low, it penalizes other hosts that use the higher rate. We analyze the anomaly theoretically by deriving simple expressions for the useful throughput, validate them by means of simulation, and compare with several performance measurements.