Research On Pilot Assignment And Power Allocation In Massive MIMO Uplink Systems

The discrepancy between the significantly increasing requirement for the communication network market and the scarcity of spectrum information resources is extremely prominent,which stimulates the high-speed growth of communication technology.In this context,enhancing the efficiency of spectrum utilization is the future research direction.At present,massive MIMO technology has remarkably heightened the spectrum efficiency of the system by configuring numerous antennas on base station,but its function has been concerned by pilot contamination.This thesis concentrates on how to enhancing the spectrum efficiency,and implements an in-depth study on the pilot contamination and power allocation of the uplink massive MIMO system.First of all,for the study of pilot contamination problem,this thesis gives a flexible pilot reuse scheme.When pilot sequence length is slightly over the number of users in a single cell,pilot assignment is performed by adding virtual users to each cell in the system.What this thesis adopts is a kind of greedy algorithm,apply Hungarian algorithm continuously to finish pilot assignment.In addition,due to the trade-off between pilot sequence length and channel estimation,the given optimization scheme can acquire the optimal pilot reuse factor.Compared with the traditional random pilot assignment scheme and integer pilot assignment scheme,reasonable pilot assignment and pilot sequence length optimization can significantly reduce the impact of pilot contamination,thereby realizing the aim of enhancing the spectrum efficiency of the system.Secondly,for the research on power allocation technology based on the proposed pilot contamination mitigation scheme,this thesis puts forward a joint pilot assignment and uplink power allocation algorithm,which is different from the previous equal power allocation algorithm.In this thesis,both data power and pilot power are regarded as continuous optimization variables,and the power allocation topic is transformed into a constrained data and pilot power budget.The comparison of some traditional schemes has verified the usefulness of the proposed scheme.Our scheme is excellent than the power allocation algorithm that only optimizes data or pilot power,and also comprehensively considers the pilot contamination.Therefore,the proposed algorithm can seriously heighten the spectrum efficiency of the system.