A General Model and Analysis of Physical Layer Capture in 802.11 Networks

Authors:
  • HCH. Chang
    H. Chang
  • VMV. Misra
    V. Misra
  • DRD. Rubenstein
    D. Rubenstein
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Abstract
While packet capture has been observed in real im- plementations of 802.11 devices, there is a lack of accurate models that describe the phenomenon. We present a general analytical model and an iterative method that predicts error probabilities and throughputs of packet transmissions with multiple sender- receiver pairs. Our model offers a more accurate prediction than previous work by taking into account the cumulative strength of interference signals and using the BER model to convert a signal to interference and noise ratio value to a bit error probability. This permits the analysis of packet reception at any transmission rate with interference from neighbors at any set of locations. We also prove that our iterative method converges, and we verify the accuracy of our model through simulations in Qualnet .L ast, we present a rate assignment algorithm to reduce the average delay as an application of our analysis. I. INTRODUCTION signals from all neighbors and can be extended to model other physical layer effects such as shadowing and multipath fading. We also present an iterative method to compute and solve the complex equations in the model, and prove that our method converges. We then verify the accuracy of these results through simulation. Last, we present a rate assignment algorithm as an application of our model and analysis. The algorithm assigns transmission rates to all senders to reduce the average delivery time of the network. The rest of our paper is structured as follows: section II reviews related work. Section III describes packet capture in 802.11. Section IV presents our modeling and analysis of interference. Section V presents simulation results with the network simulator Qualnet to support the analysis in the previous section. In Section VI, we present our algorithm to reduce expected delays, and conclude in section VII.

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