QoS support of real-time multimedia traffic in wireless IP networks

Supporting real-time multimedia applications over the packet wireless network poses a huge challenge due to the stringent QoS requirements and the time-varying and location-varying characteristics of the wireless channel. In this paper, we study a downlink, packet scheduling algorithm designed to support real-time applications with hard deadlines over the wireless network. The scheduling depends on the channel characteristics as well as the deadline of each packet. A hybrid TDMA/CDMA physical layer is used to assess the channel condition and to support the target BER of different users. RTP packet headers are used to calculate the deadline of each packet. A modified form of EDF is used to schedule packets in order of urgency and channel condition. Our results indicate that by jointly considering the channel information and the application-level information, a significant performance gain can be achieved. In addition, a more fair service is achieved even though channel conditions of different users vary greatly due to propagation losses and fading effects of the wireless channel.