Abstract
VoIP over IEEE 802.11 wireless local area network (WLAN) is growing very fast and is providing a cost effective alternative for voice communications. WLANs were initially set up to handle bursty nonreal time type of data traffic. Therefore, the wireless access protocols initially defined are not suitable for voice traffic. Subsequently, updates in the standard have been made to provision for QoS requirements of data, especially the real time traffic of the type voice and video. Despite these updates, however, transmitting voice traffic over WLAN does not utilize the available bandwidth (BW) efficiently, and the number of simultaneous calls supported in practice is significantly lower than what the BW figures would suggest. Several modifications have been proposed to improve the call capacity, and recently isochronous coordination function (ICF) was introduced to mitigate the problem of low call capacity. In this paper, we propose a modified ICF which further improves the performance in terms of the call capacity. The proposed scheme uses multiplexing and multicasting in the downlink to substantially increase the call capacity.
Highlights
VoIP over wireless local area network (WLAN) is becoming a very attractive solution for wireless voice communications
distributed coordination function (DCF) mode is based on random access of channel that is best suited for nonreal-time traffic, that is, bursty traffic, and point coordination function (PCF) mode is based on polling mechanism that is best suited for real-time traffic
Using the information provided in tables and equations in the previous sections, the call capacity for the different schemes has been calculated
Summary
VoIP over WLAN is becoming a very attractive solution for wireless voice communications. In the PCF mode [1] of operation, the access of the wireless channel is centralized by a polling-based protocol controlled by the point coordinator (PC). These drawbacks of the basic PCF mode limit the number of simultaneous VoIP calls. There are several proposals given by various authors, like dynamic PCF [11], modified PCF [6], adaptive PCF [8], and so forth, which improve call capacity These proposals seek to overcome the call capacity deficiencies of the PCF mode of operation, thereby providing capability to the WLAN network to accommodate a larger number of simultaneous VoIP calls. One of the proposed techniques introduces a new modified multiple access mechanism termed as isochronous coordination function [9] to improve the capacity
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