Research On The Technology Of Pilot Contamination Mitigation In Massive-MIMO

This work concerns cellular networks when their base station has an unlimited number of antennas, which is called Massive-MIMO. As is known to all,Massive-MIMO has higher data transmission rate and stronger robustness than conventional MIMO, however, pilot contamination,which is resulted from the non-orthogonal sequences transmitted by adjacent cells, has become the bottleneck and impede its development. Pilot contamination can disturb uplink channel estimation and lead to the degradation of the performance in system, thus, how to resolve the problem of pilot contamination in Massive-MIMO has become the focal point in communication field.There are three ways to mitigate pilot contamination in Massive-MIMO, using effective precoding, precise channel estimation and efficient pilot assigning scheme. This thesis firstly introduces the pilot contamination(PCP) and eigenvalue decomposition(EVD) channel estimation,Then it focus on the pilot assigning scheme.Before giving the new scheme, this thesis introduces two pilot assigning schemes, which are based on the user location and time division, then, this thesis combines factional frequency reuse technology with the later, and gives a new pilot assigning scheme. This scheme will divide all cells into several groups, when the cells in one group are receiving up link information, the other groups are transmitting down-link information at the same time, then, all the cells in one group will be assigninged with different subcarriers by fractional frequency reuse technology, Because all the subcarrier are transmitted orthogonally, the users in boundary area in one cell can only suffer with the pilot contamination from another users who use the same subcarrier, by this way, pilot contamination can be mitigated to a large extent. The Matlab simulation results confirmes that the bit error rate and data transmission rate can be improved obviously by the new pilot assigning scheme.