Multimedia packet forwarding in 802.11 networks with access point diversity

Official URL: http://192.168.1.20/record=b1226360 (Table of Contents)

The characteristics of the wireless communication channels are usually time-varying, where the quality of the received signal changes rapidly over time within a few packet transmissions. The time-variability of the wireless channel is due to noise, fading, interference and mobility. An important artifact of these effects is the bursty packet losses observed at the link layer, and multimedia applications such as voice over IP and video-on-demand require resiliency against packet losses. Channel diversity is a well-known technique to alleviate the effects of time- variable wireless channels. In this thesis, we aim to apply link-layer diversity for resilient multimedia transmissions in IEEE 802.11 wireless networks. IEEE 802.11 wireless local area networks (WLANs) have widespread deployment in enterprises, public areas and homes. In many cases, a mobile user has the option of connecting to one of several 802.11 access point (APs). Unlike the standard operation where a mobile user is connected to a single AP for the duration of a session, we consider the case where a user is connected to all available APs in the vicinity. This type of operation requires a new multi-access control (MAC) protocol, where the user has to decide to which AP the packet is forwarded. The selection of the AP for each packet is performed in our proposed MAC protocol based on the most recent channel observation and the collected long-term statistics of packet loss and burstiness, where the aim is to maximize the probability of successful transmission of each packet. Our analysis of the long-term channel statistics such as burst length and packet error rate also show that these parameters depend on the user load, channel coherence time and the number of users in the network. The proposed MAC protocol is analyzed using Qualnet network simulator, and it is shown that our proposed protocol can improve the efficiency of the system approximately by up to %25 over the standard 802.11 protocol where each user is associated with the AP that has the maximum received signal strength.