Transmission opportunity analysis of IEEE 802.11e hybrid coordination function

Abstract

The IEEE 802.11e is the new standard for wireless LAN, designed to provide Quality of Service (QoS) for multimedia services. The centerpiece of the 802.11e standard is the hybrid coordination function (HCF). HCF provides an efficient mechanism for centrally coordinated medium access and uses the enhanced distributed coordinated function (EDCF) for distributed coordination of medium access. One of the main characteristics in the new HCF is called the transmission opportunity (TXOP). In both HCF and EDCF, the TXOP is defined as the interval of time where a station has the right to initiate its transmission. During a single TXOP, a station can transmit several frames without any contentions or any additional polling from the access point (AP). In this paper, we propose an analytical model of HCF in order to calculate the optimal values of TXOP for voice and video traffic services. Further analyses are carried out so that the optimality of our calculated TXOP values can be validated.