The impact of clear channel assessment and virtual carrier mechanisms on throughput of WLANS

Abstract

It is well known that the 802.11 standard specifies two ways to determine if the medium is busy: the physical and virtual carrier-sense functions. The first is a physical carrier sense [5] specifies that any PHY must provide a technique to sense if the medium is busy. The function in the PHY layer responsible for this is called the Clear Channel Assessment (CCA). The second is the virtual carrier-sense  mechanism that consists of a Network Allocation Vector (NAV) maintained by each client. The NAV can be thought of as a client's best guess as to how long the  medium will be busy! The client's NAV is updated in response to receiving a frame whose duration field contains a value that exceeds the current NAV value. In this paper, we investigated the effect of carrier sensing with Collision Avoidance on congested and error-prone channels. We carried out an analysis of the behavior of wireless stations in congested and error-prone 802.11 wireless networks. We  provided a simple and precise design to analyze the throughput of both basic and optional access schemes. Our analysis is validated through extensive simulation results. Our results show that transmission errors have significant impacts on  wireless network performance

Keywords: IEEE 802.11, wireless LAN (WLAN), medium access control (MAC), distributed coordination function (DCF), transmission error, collision.