Wireless LAN: study of hidden-terminal effect and multimedia support

Wireless local area networks (WLAN) are expected to be a major growth factor for communication networks in the up-coming years. They are expected to provide a transparent connection for mobile hosts to communicate with other mobile hosts, and wired hosts on the wired LAN and broadband networks. Two WLAN projects have undergone the standardization process: the IEEE 802.11 and the ETSI HIPERLAN. Most of the existing study of the two MAC protocols focused on simulation results, and none of them has formally analyzed the hidden-terminal effect, which is both crucial and unavoidable in wireless/mobile environment. We formally analyze the hidden-terminal effect on HIPERLAN. Through mathematical analysis, we formulate network throughput under hidden-terminal influence in terms of the original (clear-channel) throughput, hidden-terminal probability, and other protocol parameters. We show that when hidden probability is greater than zero, the achievable throughput is reduced by more than the percentage of hidden probability. We evaluate and compare the two WLAN MAC protocols by simulation of the effect of hidden terminals on (1) network throughput, (2) real-time voice delay, and (3) number of voice and data stations supported while guaranteeing delay for voice. We also evaluate how well the two MAC protocols support real-time traffic while considering the effects of frame size and other network parameters, and measure (1) the distribution of voice delay and (2) number of voice and data stations supported while guaranteeing their quality of service. We found that, compared with IEEE 802.11, HIPERLAN provides real-time packet voice traffic with shorter delay, and at the same time provides the non-real-time packet data with a higher bandwidth.