Pilot decontamination techniques based on beam-domain channel characteristics in millimetre-wave sparse channels

摘要

The upcoming 5G system is expected to utilise large-scale antenna arrays to increase the users' data rate and system capacity. With a large number of antennas, channel estimation becomes a very critical design issue due to the adverse effects of pilot contamination. Some problems in the existing channel estimation methods studied in the literature include: (i) the complexity of signal processing on the spatial domain is very high. (ii) Channels are quite frequency selective in the spatial domain. (iii) It is not easy to obtain the second-order statistics of channels. In this study, the channel estimation issue is investigated using the signal processing in the beam domain. It is due to the salient channel sparsity at millimetre-wave frequencies that only a few beam channels need to be estimated. The authors exploit these beam channels to propose some pilot decontamination techniques: basic pilot allocation, beam-set non-overlapping allocation, intra-cell interference mitigation allocation and maximum beam power based allocation (MBPBA). Both large pilot reuse factor and beam-domain power control are also presented to supplement the proposed techniques. Simulation results show that the best method is MBPBA in terms of overhead and normalised square error.