大规模MIMO多小区TDD系统中的导频污染减轻方法  

Pilot Contamination Reduction in Very Large MIMO Multi-Cell TDD Systems

作　　者：王海荣[1] 王玉辉[2] 黄永明[1] 杨绿溪[1] 

机构地区：[1]东南大学信息科学与工程学院,江苏南京210096 [2]南京船舶雷达研究所,江苏南京210003

出　　处：《信号处理》2013年第2期171-180,共10页Journal of Signal Processing

基　　金：国家自然科学基金(60902012;61071113;61201172;61201176);国家科技重大专项(2011ZX03003-001-02;2011ZX03003-003-03);教育部博士点新教师基金(20090092120013;20100092110010);江苏省自然科学基金(BK2011598;BK2011019)~~

摘　　要：由L个小区组成的大规模MIMO TDD系统中的下行用户和速率随着基站天线数M的增加主要受限于小区间的上行导频污染。假设小区内导频正交,小区间导频完全复用,分别推导了基站估计所有信道和期望信道的MSE闭式表达式MMSE和MMlSE,并获得了MMSE的下界为M(L-1)和MMlSE的上界为M(L-1)/L。并且发现随着天线数M的增长且当导频序列长度#较大时,#的大小对MMSE和MMlSE性能的影响很小,由此提出一种上行导频功率控制方法,即把通常的导频发射时隙分为两段,使交叉增益相对较大的小区间的导频发射时隙错开,从而提高MMSE和MMlSE性能,由此基站可以设计出更加精确的预编码,进而极大地提升了每小区下行多用户可达和速率性能。理论分析和数值仿真结果都验证了这一结论。In very large MIMO time-division duplex system with L cells, the sum-rate in downlink is bottlenecked by the problem of pilot contamination as the base station＇ s antennas number M grows. Assuming uplink training with orthoganal training sequence in one cell while aligned pilots are used in all cells, the close form analytical expression of the mean square error （MSE） of the channel estimators AdMsE（ for all channels） and mLmse（ only for desired channels） were proposed, respectively. And ,mmse has a lower bound M（L-1） while mLmse has an upper bound M（L-1）/L. We found that when the length of training sequence r is relatively large with the antennas number M＇ s increasing, r has little effect on the performance of .MMsE and mLmse. Thus, a pilot power control scheme in uplink was proposed, which dividing the training phase into two parts and making the pilot transmissions in the cells with relatively big cross gain staggered. The performance of .A4sse and .A,q^sE were improved by it so that the base station could design much better precoding, which greatly enhancing the sum-rate in downlink pre-cell. The theoretical analysis and numerical results both verified the results.

关 键 词：大规模多输入多输出 导频污染 多小区 时分双工系统 迫零 

分 类 号：TN911.22[电子电信—通信与信息系统]