Transmission Time Analysis and Modeling in 802.11e Contention Free Burst Mode

Several analytical models have been developed for both 802.11 distributed coordinated function (DCF) and 802.11e enhanced distributed channel access (EDCA). However, none of these models considers the 802.11e Contention Free Burst (CFB) mode which allows a given station to transmit more than one frame for each access to the channel. In spite of its influence on the global performance and its role as a main differentiation parameter in 802.11e, transmission opportunity (TXOP) bursting is ignored in all already existing models. These latter consider, for the sake of simplicity, that a particular station transmits a unique frame when having data to be transmitted. The main objective of the current work is to analyze the TXOP bursting procedure and to propose a simple model allowing us to calculate the transmission time occupied by a particular AC when using the CFB mode. It will be shown that this transmission time is directly a function of the number of transmitted frames which depends on the queue size and on the TXOP limit. CFB performance analysis as well as the proposed model are discussed, demonstrated and validated by means of simulations.