Research On Resource Allocation In Wireless Multicast System With Multiple Antennas

With the rapid development of wireless communications technology and wireless communication networks, wireless multimedia services become widely popular. In broadcast and multicast transmission, the transmitter simultaneously sends the same information to multiple users using the identical time-frequency resource in order to improve spectral efficiency. Wireless broadcast and multicast technology is particularly suitable for wireless multimedia data transmission because of the broadcast characteristics of wireless signal. In wireless multicast network, dynamic changes of networks, users and traffics restrict the efficient utilization of wireless resources and limit the spectral efficiency of the system. The resource allocation on spatial domain, frequency domain and the user’s domain in multicast system has become one of the most interesting topics in wireless communication area.This dissertation investigates on wireless resource allocation on spatial domain, frequency domain and the user’s domain in multicast system. First of all, we focus on transmit precoding design based on limited feedback in a multi-antenna multicast system which includes several multicast groups. Then the inter-group resource allocation and intra-group resource allocation is researched according to the number of multicast groups in multicast system. The main contents and contributions of this dissertation are presented as follows:First of all, we focus on transmit precoding design to maximize the average minimum received SINR among the receivers where the CSIT is obtained via limited feedback in a multi-antenna multicast system which includes several multicast groups. The transmit precoding can be considered as spatial resource allocation in multi-antenna system. The random codebook is adopted in the limited feedback scheme. The optimization problem is formulated considering the quantization distortion in the feedback process. Due to the NP-hard nature of the problem, the SDR-randomization method is adopted to obtain the optimum beamforming vectors.Secondly, the problem of inter-group resource allocation with downlink precoding for the multicast systems is studied in multi-antenna wireless multicast system with multiple multicast groups. Specifically, we formulate an optimization problem to maximize the system throughput given a set of available resources (power and subcarriers). A three-step algorithm is proposed, in which the multicast precoding process, subcarrier assignment and power allocation is operated separately to reduce the computational complexity. Against the unfairness among multicast groups using the throughput maximizing resource allocation algorithm, the problem of resource allocation considering inter-group fairness for multi-antenna multicast systems is studied.Thirdly, the intra-group resource allocation is analyzed in one-group multicast system to solve the problem that the transmission rate of conventional multicast transmission in wireless system is limited by the worst user in the multicast group. A multicast resource allocation algorithm based on layered transmission to maximize the throughput is proposed in this paper, considering the QoS requirement of each user. Firstly, the multicast data is encoded into a basic layer and an enhancement layer. Then the multicast allocation of resources is formulated to maximize the throughput of the enhancement layer with a total power constraint and a minimum rate requirement. Also, an intra-group resource allocation algorithm is proposed to maximize the transmission rate in multicast group by exploiting the multiuser diversity among multicast users. The subcarrier and power is allocated separately to reduce the computational complexity, considering the Quality of Services (QoS) of each user. Each subcarrier is allocated to some users with good channel state information. Due to the non-convex property of the power allocation, power allocation based on gradient is adopted to optimize the power allocation locally. Then the intra-group resource allocation in multi-antenna multicast system is considered. The joint optimization scheme in spatial domain and frequency domain is researched by joint precoding and subcarrier allocation to reduce the complexity.Finally, conclusions and future work are summarized in the end of this dissertation.