The Research On Pilot Design And Channel Estimation In Massive MIMO Systems To Reduce Pilot Contamination

Massive MIMO system with dozens or hundreds of antennas at the base station has important significance for next-generation wireless standards because of its ability to achieve high energy and spectral efficiency,high data throughput and strong communication capabilities,a relatively simple signal processing process high efficiency.Pilot contamination is another important factor in limiting the performance of the massive MIMO system.As the number of base station antennas tends to infinity,interference of intra-cell and irrelevant noise can be eliminated and the reuse of the same orthogonal pilot sequences in adjacent cells becomes the only impairment to the performance of the system.In particular,pilot contamination of massive MIMO system means the Signal to Interference plus Noise Ratio(SINR)of system is ultimately limited by the CSI from the BSs with the reuse pilot sequences.This paper studies the effects of pilot contamination and learns how to reduce it.In this paper,the traditional Massive MIMO system model is established firstly,and the pilot transmission,channel estimation and data transmission are analyzed under this model.The emphasis is placed on the analysis of pilot contamination,the reasons for its introduction,the impact on system performance and the common method of eliminating pilot contamination.It has played an important rule in reconstruction of the system model and the analysis of the pilot contamination under the new model.This paper researches the pilot contamination from these three aspects: rebuild system model,pilot reusing design and maximize system performance.In this paper,the network model considers stochastic geometry that users are distributed according to a homogeneous Poisson point process(PPP)to simulate the real user distribution.And analysis the pilot contamination under the new model.Using the flexible pilot reuse to simulate the reality of the pilot allocation strategy.The users suffer from severe pilot contamination use orthogonal pilot and the others with light contamination can reuse a same set of pilot sequence,ultimately get the optimal pilot reusing factor and achieve a reasonable pilot allocation.Finally,the relationship between system performance and system parameters under stochastic geometric distribution model is analyzed,and the value of each parameter when the system performance reaches the best is found out.