Research On Pilot Power Control Method In Massive MIMO Cellular Network

Massive MIMO (Multiple-In Multiple-Out) as the fifth generation mobile communication technology (5G) is one of the key technology researches have become a hotspot in wireless communications. In Massive MIMO system, the base station is equipped with hundreds of thousands or even more antennas, and the number of antennas is much larger than the number of active users. When the number of antennas is infinity, Massive MIMO channels tend to be orthogonal. If we use orthogonal channels, accurate channel state information is required for the base station to obtain the channel state information is relatively high. The pilot channel estimate is widely used to get the channel estimation. Pilot pollution must exist due to the reuse of the same set of orthogonal pilot in multi cells, so that the channel estimation error increases. Pilot power control method plays an important role in reducing the pilot pollution problem. The current pilot power control method also has the problem that the frequency of the pilot occupied slot is too long to affect the resource utilization.At first, the Massive MIMO system model is introduced in the thesis, channel estimation based on pilot is discussed according to the frame structure of the pilot. In view of the insertion of the pilot estimation in typical least squares (LS) channel estimation and minimum mean square error (MMSE) channel estimation and Superimposed pilot channel estimation several pilot estimation methods are explored. And the pilot pollution analysis is carried out.Then, Massive MIMO cellular network pilot power control method is discussed in this thesis. In view of the problem of low utilization ratio of resources caused by the long time slot of the frequency while the pilot pollution of adjacent cells can be eliminated. Pilot power control methods are studied and improved. The improved pilot power control method in cellular networks cellular network is presented. The method divides cells into three categories which the same district not adjacent, then the pilot is divided into three non-overlapping pilot slots, only the same type of residential users in a time slot. Theoretical derivation and simulation results show that the improved method can reduce the length of the pilot slot while eliminating the pilot pollution. It can also improve the resource utilization rate.In order to improve the efficiency of resource utilization, the superimposed pilot estimation based on the study of improved pilot power control method in cellular network is improved. The proposed method changes pilot transmission frame structure in cellular network. The pilot is superimposed on the information data to be sent together, and the pilot part is controlled by the power. The theoretical derivation and simulation results show that the proposed method in low signal-to-noise ratio, based on superimposed pilot frequency pilot power control method in the channel estimation error and resource utilization performance is better than the previously mentioned improved based on insertion pilot frequency pilot power control method.