Analyzing the hidden-terminal effects and multimedia support for wireless LAN

Wireless local area networks (WLAN) are expected to be a major growth factor for communication networks in the upcoming years. They an 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. Recently there have been two WLAN projects, which are undergoing 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. In the first part of this paper, 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. In the second part of the paper, we evaluate and compare the two WLAN MAC protocols by simulation on 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; (2) number of voice and data stations supported while guaranteeing their quality of service. We found that, comparing 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 higher bandwidth. We believe that the formal analysis presented in this work would provide a significant reference for wireless/mobile network community; the comparison study of the two MAC protocols would also aid the future enhancement of WLAN MAC protocols. (C) 2000 Elsevier Science B.V. All rights reserved.