On Key Techniques In Opportunistic Beamforming Systems

Multi-antenna technique will become one of key techniques in the next generation wireless communication system. It can increase data rate and channel usage. Based on Multi-antenna technique, opportunistic beamforming system can exploit multi-user diversity to increase system throughput. With wireless resource management algorithm, it can also increase user experience. Opportunistic beamforming can be used to support new operations in the next generation system.Opportunistic beamforming system is analyzed and the key techniques is concluded. 3 main techniques are researched: user scheduling algorithm to increase system throughput, channel state information feedback algorithm for broadband system and scheduling algorithm to increase user experience. Based on greedy algorithm, a fast power allocation and user scheduling algorithm is proposed. With optimization theory and recursive method, characteristics of multisuer scheduling and power allocation are analyzed, and the improved greedy search algorithm is proposed. Simulation results show that by using the improved greedy search algorithm, the number of user searching and power allocation is equal to the number of transmit antennas, and almost the same throughput is achieved with the exhaust search algorithm.To increase feedback efficiency and uplink usage, a feedback and scheduling algorithm in OFDMA system is proposed for opportunistic beamforming. The method aggregates sub-carriers with correlation. Each sub-carrier is matched with the beams of correlated sub-carriers so that a more exact CDI (channel direction information) is obtained to increase the average system throughput. Limited feedback is used to feedback channel state information of sub-carrier groups to decrease the uplink feedback load. Simulation shows that the method proposed can achieve 1% more throughput compared with using analog SINR feedback, with only about 30% feedback load of sub-carrier independently limited feedback.At last algorithms to improve user experience are researched. Average system throughput, packet delay and user fairness are jointly considered. 3 typical algorithms are analyzed: PF, JOBS and TFS.Key techniques of opportunistic beamforming are researched in this paper, with some achievements. As the development of network cooperation, it can be introduced into opportunistic beamforming. Techniques of network cooperation in opportunistic beamforming system need more research work.