UNCLASSIFIED/UNLIMITED Provision of QoS for Multimedia Services in IEEE 802.11 Wireless Network

Implementation of the IEEE 802.11 technology for wireless local area networks (WLANs) has created a new opportunity to support real time and multimedia applications. The IEEE 802.11 defines a Medium Access Control (MAC), and Physical Layers (PHYs), which provides rates from 1 to 54 Mbit/s depending on specification. In IEEE 802.11 network, the PHY rate to be used for the transmission is completely determined by the source node and is closely connected with the wireless channel performance. The varying nature of WLAN channel over time can degrade the QoS level of multimedia service, which calls for elaboration of advanced QoS mechanism supporting multimedia services. The research works applied to video transmission over WLAN mostly concentrate on using a link adaptation techniques or optimisation of video stream by cross-layer signalling. It appears to be not sufficient as far as a provision of QoS for multimedia services is considered. In the paper, a new mechanism of QoS enhancement respecting also modifications in transport and network layers is discussed. A general description of this mechanism is presented with special emphasize on new approach to the multimedia rate control. The paper covers the verification of the proposal by simulation method as well as a discussion of some selected results of simulation