Massive MIMO多小区系统中导频污染减轻方法

Massive多输入多输出(multiple-input multiple-output, MIMO)多小区系统时分双工(time division duplex,TDD)模式中,导频训练序列在小区间是复用的,小区间不正交的导频序列会造成严重地导频污染,从而降低信道估计和预编码的准确性,成为系统性能提升的瓶颈。针对此问题,提出基于小区交叉分类正交识别和上行导频功率控制的导频污染减轻方法。对所有小区进行交叉分类,给相邻的不同类小区分配正交的小区识别位,并把相应的识别位加到本小区终端发射的导频序列头部,使基站能够识别来自不同类小区终端的导频序列。同时控制同类小区内终端发射导频序列的功率,减少对交叉同类小区内基站的影响。理论推导和实验结果证明,所提方法不仅实现简单,而且可以有效地减轻多小区系统导频污染。

Approach of pilot contamination reduction in Massive MIMO multiple cells system

In the Massive multiple input multiple output (MIMO) multiple cells system, the reverse training pilots sequences of terminals, which are from different cells, are non-orthogonal due to the reuse of these pilots between cells with the mode of time division duplex. The non-orthogonality of the training sequences leads to pilots contamination, which makes the forward channel estimation and pre-coding inaccuracy and blocks the improvement of the system. An approach is proposed, which is based on the cells crossed classification orthogonal identity and pilots power control, to reduce the pilots contamination. All the cells are classified crosswise and orthogonal identifications are distributed to the terminals and base stations in different kinds of cells. Further, terminals add the allocated identification to the head of their pilots so that the base stations can identify the sources of the received pilots. Pilots power control is applied to the terminals in the same kind of cells to reduce the influence for the base station in intersecting cells. Theory analysis and simulations results verify that the proposed approach is not only simple but also effective to alleviate pilots contamination.