【摘要】 上行导频污染是大规模MIMO多小区多用户TDD系统的主要性能瓶颈。本文推导了下行链路中MF、ZF单小区预编码、基于MMSE的多小区预编码以及基于最大化SLNR准则的预编码策略在有导频污染的大规模MI-MO下的系统可达和速率渐近性能,发现当基站天线数趋向无穷时,各个策略的等效信干比均收敛到仅与大尺度衰落因子相关的一个比值,由此可以得到一个系统可达和速率的渐近结果。基于此渐近结果,以最大化系统可达和速率为目标,获得了一个导频调度方案,即使得小区间相互干扰较小的用户采用相同的导频而相互干扰较大的用户采用正交的导频,从而在存在导频污染的情况下,可以提升系统的整体性能。理论分析和数值仿真结果都验证了以上结论。更多还原

【Abstract】 The performance of very large MIMO multi-cell time division duplexing system is bottlenecked by the problem of uplink pilot contamination.The asymptotic achievable sum rate of precoding schemes,including Matched Filter(MF),single-cell Zero-Forcing(ZF),multi-cell Minimum Mean Square Error(MMSE)-based and maximize Signal-Leakage-Noise Ratio(SLNR)-based,with large arrays in downlink was investigated.As the antenna of base station grows without limit,the effective signal-to-interference ratio of each precoder converges to a ratio only associated with large scale fading coefficients,from which an asymptotic result of achievable sum rate of system can be achieved.Based on our derivations,a pilot scheduling scheme was proposed by maximizing the system achievable sum rate,which making users among cells with most different spatial feature using same pilots while users with most same spatial feature using orthogonal pilots.It could provide much better performance in the presence of pilot contamination.The theoretical analysis and numerical results both verified the results.更多还原