QoS Support in Wireless Networks

Wireless communication has gained a great deal of attention in the last few years from both industry and academia. Nowadays, most computerized devices are equipped with wireless ports such as IEEE 802.11 WLAN, Bluetooth, or Inferred port. IEEE 802.11 WLAN device, in particular, is an ideal wireless communication tool for any mobile-based computer such as a notebook or PDA because of their low cost and high bandwidth. The wireless environment has some characteristics that make supporting QoS a very challenging task. These characteristics are bandwidth scarce, radio channel conditions that vary over the time, and highly packet loss. Legacy IEEE 802.11 standards such 802.11a, b, or g originally do not support QoS, thus many QoS enhancement schemes have been proposed; most of them focus on enhancing a particular part or mode of the standard. QoS support in any system is an accumulative task, as it needs to be maintained throughout all layers. The wireless multimedia application is the best example for proving the accumulative property for its QoS as the user is the final judge about whether the provided quality is satisfactory or not. In this chapter, we will study and analyze QoS support for wireless network and the target application, which will be a real-time multimedia application. First, we discuss QoS support for multimedia application. Second, a framework for classifying the QoS enhancements will be proposed. Next we will study QoS support in IEEE 802.11 and the new QoS extension IEEE 802.11e, and then we will study and classify the proposed QoS enhancement schemes according to the proposed framework. Finally, we will discuss mobility as an important issue for QoS support in wireless environment.