Research On The Key Pre-coding Technology In C-RAN Multiple Antenna Systems

With the development of autonomous vehicle,virtual reality and artificial intelligence,people's demand for information data is growing,showing an exponential growth.The C-RAN architecture can uniformly manage and dynamically allocate baseband resources,improve system spectrum efficiency and power efficiency,and enhance network coverage.In this paper,the distributed multi-antenna downlink hybrid precoding technology under C-RAN architecture is studied.Firstly,C-RAN architecture and massive MIMO multi-antenna systems are introduced.The latest research of related technologies such as transmit precoding in multi-antenna systems is summarized.Secondly,the distributed multi-antenna system based on C-RAN architecture is studied,channel capacity of the uplink and downlink of the distributed multi-antenna system are analyzed,and the centralized multi-antenna systems with the distributed multi-antenna system in different transmission modes are compared.The simulation results show that the multi-antenna systems under the C-RAN architecture has higher system capacity than the centralized multi-antenna systems.Then,the downlink hybrid precoding technology of the C-RAN architecture multi-user multi-antenna systems is studied.Assuming that users are equipped with a single antenna and a simplified receiver,a hybrid precoding scheme based on phase compensation and a hybrid precoding scheme based on alternating optimization are presented.The performance of the two schemes is compared.The simulation results show that the average user rate based on the alternate optimization scheme is better than the phase compensation scheme,which is at the cost of computational complexity.The analog precoding design problem under the unit modulus constraint can be solved based on the alternating minimization algorithm,and the performance is close to the full digital precoding algorithm.Finally,the hybrid precoding technique for the downlink of the C-RAN architecture single-user multi-antenna system is studied.A single-user equipped with multi-antenna scenario is presented.In this paper,a hybrid precoding scheme based on manifold optimization and a hybrid precoding scheme based on phase extraction are presented.By comparing the performance of the two schemes by simulation,the spectral efficiency based on the alternate optimization scheme is higher than the phase extraction scheme,and the performance is close to the full digital precoding algorithm,but the complexity is higher,and the hybrid precoding scheme based on phase extraction shows a trade-off between the performance and complexity.