Opportunistic Multicast Scheduling For Multi-Antenna Multicasting System With Limited Feedback

In wireless multicast system, the transmitter sends common message to multiple users in the same multicast group at once using the identical time-frequency resource in order to save spectral resource and improve system throughput. However the complexity of wireless channel conditions and dynamic changes of users restrict the efficient utilization of wireless resources. Therefore the multicast resource allocation on time domain, frequency domain, spatial domain and the user’s domain has become one of the most interesting topics in the present research of wireless multicast transmission.The multicast scheduling scheme exploits the multicasting gain by serving all users simultaneously. However, for a multicast group where multiple users with different instantaneous channel conditions, to ensure that all users can be served, the message has to be sent at a low data rate constrained by the user with the poorest channel conditions, which in turn degrades the system throughput. The existing multi-antenna technology and opportunistic multicast scheduling scheme efficiently resolved the problem of the constraint of the poorest user. But the opportunistic multicast scheduling scheme for multi-antenna multicast system is a three-step optimization problem. Due to the NP-hard nature of the problem, this dissertation adopts the precoding scheme based on codebook in order to turn the problem into an irrelevant two-step optimization problem. Although this precoding scheme can’t get the optimum solution, but it reduces the complexity of the algorithm and improves the throughput of the system compared to the old best-user precoding scheme. In previous works static opportunistic multicast scheduling scheme derives the optimal selection ratio in each transmission based on extreme value theory, but in the scheme some users who have received message successfully are selected again, which results in rate loss. This dissertation provides a semi-dynamic opportunistic multicast scheduling scheme which adjusts the selection radio in each transmission. Compared to the static opportunistic multicast scheduling scheme the semi-dynamic opportunistic multicast scheduling scheme increases the rate of each transmission and improves the average system throughput.In order to apply opportunistic multicast scheduling scheme to actual system as soon as possible, this dissertation investigates on opportunistic multicast scheduling for multi-antenna multicasting system with limited feedback and the algorithm adopts the channel estimation scheme and precoding code selection scheme based on the same codebook. Based on the above schemes, two algorithms in order to reduce the feedback load of semi-dynamic opportunistic multicast scheduling are introduced. The RSF algorithm reduces the feedback load by avoiding the feedback of the users who have received message successfully. And the BT algorithm requires the feedback of all users once in the transmission of the same message.