Research On Information Feedback And Overhead In 5G MIMO System

With the rapid flourishing of smart devices,the demand for mobile data traffic is increasing.In order to provide higher data-rate and service quality wireless communications for mobile.users,the discussion and standardization of 5G are being carried out in full swing.Since 3GPP set up projects for FD-MIMO and NR MIMO,5G MIMO has become one of the key technologies in mobile communication due to its high capacity,antenna gain,and flexible beamforming with full dimension information,etc.However,the continuous increase in the number of users,antennas and the overhead of reference signals makes the time-frequency resource more scarce.Reducing system resource overhead is one of the targets of each research subject in the standardization of 5G MIMO.How to carry out information feedback,and how to reduce the system resource overhead in the process of communication have become key problems.In addition,the remote base station interference problem in the practical deployment should also be considered in 5G MIMO.To address the aforementioned problems in 5G MIMO,this thesis has studied the following work:1.An aperiodic configuration CSI-IM scheme based on trigger is proposed to minimize the waste of CSI-IM resource,which is periodically configured for inter-cell measurement.The base station can configure mobile users in different locations with specific CSI-IM resource.Mobile users then work with the corresponding measurement.When the inter-cell interference is small enough,mobile users send a request to suspend the inter-cell interference measurement to the base station.The base station decides to suspend the configuration of CSI-IM and reuse the resource depending on the trigger condition.This scheme can effectively reduce the overhead of CSI-IM resource.The simulation results show that the proposed scheme can improve the resource utilization rate and increase the throughput by about 20%when the adjacent base station interference is small.2.To address the problem that base station chooses wrong users in multi-user pairing in FD MU-MIMO system,a multi-user pairing scheme based on CSI-IM is proposed to solve the problem of resource waste in the pairing process.In this scheme,the user determines its user pool number according to the ratio of the inter cell interference intensity and the received signal power,then feedbacks it to the base station.The base station decides the members of pairing candidate groups according to both the users'position information and feedback information,configures resource allocation and selects users to do the MU hypothesis.Simulation results show that the proposed scheme can effectively improve resource utilization and system performance,and the more users,the more significant the improvements.3.An interference suppression scheme based on beam-forming is proposed,aiming at the remote base station interference problem.In this scheme,the interfered base station and the interfering base station communicate by X2 interface,and then the interfering base station adjusts the antennas by using flexible adjustment of dip angle and beam forming technology in 5G MIMO,which can solve the interference problem of remote base station conveniently and flexibly.With the modeling and analysis for the proposed scheme,the superiority has been proved.The results provide solutions for the interference problems of practical deployment in the future.In conclusion,this thesis focuses on the study of reduction of system resource overhead and interference suppression scheme in 5G MIMO system from the above three aspects.The performances of the proposed schemes are also analyzed.