Optimal packing of VoIP calls in an IEEE 802.11 a/e WLAN in the presence of QoS constraints and channel errors

In this paper, we study the performance of VoIP over an IEEE 802.11e network. The contribution of this paper is to understand the advantages and limitations of IEEE 802.11e enhanced distributed coordination channel access (EDCA) as well as HCF coordinated channel access (HCCA) for carrying VoIP traffic. We also study the influence of the backoff window and TXOP size on the capacity of VoIP calls that can be admitted. We provide a closed form solution for the maximum number of VoIP calls that can be admitted subject to the QoS constraints of packet loss and delay. We analyze the HCCA with a simple scheduler and decide the optimal TXOP allocation for VoIP calls. The scenario consisted of all calls originating from a basic services set (BSS) and destined for outside the BSS. For this scenario, we evaluate via simple analysis and simulation, the capability of the IEEE 802.11e MAC to support VoIP in the presence of errors.