Abstract
With the number of wireless network devices soon surpassing the number of wired network devices, the demand over wireless networks is increasing. Therefore, the IEEE 802.16 standard (commonly known as WiMAX), which has been proposed as a new wireless broadband standard, is capable of delivering very high data rate and covering wide area. Furthermore, the video multicast service would become one potential application over WiMAX with the popularity of streaming applications in the Internet. The main purpose of this thesis is to propose a low-complexity decision mechanism for the modulation of video coding layers to ensure the efficiency of bandwidth usage. The main problem of multicasting is the diversity of receivers. The diversity may cause different receiving constrains for modulations. So, the transmitter should choose proper modulations to achieve the satisfactions of most receivers. Therefore, this thesis intends to adjust the modulation scheme of each coding video layer in each group of picture (GOP) time according to the size of video layer, receiver distribution, and available symbols of this video session. From above-mentioned factors, an optimization problem can be formulated and then solved with weighted average and minimax methods. Furthermore, a GA-based algorithm is proposed to reduce the complexity of modulation decision. Simulation results are shown to compare the above-mentioned three optimization methods. In addition, this thesis also makes a study on allocation of given total downlink symbols to OFDMA subcarriers in several multicast video sessions.