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This paper presents a new dynamically adaptable polling scheme for efficient support of voice communications over an IEEE802.11 network. The proposed Cyclic Shift and Station Removal polling scheme is implemented only on the Access Point of each Basic Service Set without requiring any modification on the existing access protocol. This polling scheme increases the number of conversations in case of silence detection, while maintains high voice quality. By considering constant bit rate digitized voice traffic, the paper presents a discretetime Markov chain model, that is, used to analyze the performance of the IEEE802.11 Point Coordination Function in terms of maximum number of supported conversations, when silence detection is used at the mobile terminals. The paper also determines how the parameters of the proposed polling scheme have to be related to the silence detector hangover. q

The theoretical performance of CSMA/CA, as it is used in IEEE802.11 wireless LANs, is investigated in this paper. We adopt and modify a previously presented analytical approach for CSMA/CA protocols in wireless LANs with finite number of stations and find closed-form equations for throughput and delay. The presented numerical results highlight the characteristics of both CSMA/CA methods and define how their performance depends on the number of stations and on traffic conditions.

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