多层异构蜂窝网络中的嵌套对准与协作干扰删除

With the crushing demands of future wireless data traffic, the multi-tier heterogeneous cellular networks (HCN) are emerging as a promising solution. However, the inter-tier inter-cell interference is appeared as a new phenomenon that will severely degrade the system performance. Since this type of interference has unique features, we need to study corresponding interference coordination or cancelation methods. Path loss happens in electromagnetic wave propagation, and due to the position variances of different base-stations and users, the channel gains differ a lot in HCN and there are more transmission opportunities in amplitude spaces. This project tries to utilize the amplitude spaces more efficiently, and has the following research contents: in single-antenna multiuser interference channels, we unify the ideas of layered modulation, signal nesting and interference alignment, and propose a nested alignment method that can work in any random channel realization; in multi-antenna multiuser interference channels, we study the implicit connections between the subspace orthogonal and set nesting, and propose a unified framework of the amplitude-space multi-dimensional nesting and vector-space interference alignment; in multi-channel interference networks, we propose a cooperated interference cancelation method by sending interference information through cross or redundant links to the interfered receiver. In this project, we take the initiative to create opportunities for interference cancelation. Our researches will not only greatly improve the spatial capacity of the multi-tier HCN, but will also promote new cooperation mechanisms in interference channels.

随着未来移动数据业务千倍量级的增长需求，蜂窝网络日益向多层异构的形式发展，小区形态发生根本变化，小区间干扰变得更加复杂，尤其是出现了严重的异层小区间干扰，需要研究新的小区间干扰协调和消除方法。本项目抓住电波传播过程中具有路径损耗这一自然特性，根据异构网络中各基站和用户位置的差别，对幅度空间中出现的传输机会进行高效利用。计划研究内容包括：在单天线多用户干扰信道下，对分层调制、信号嵌套、干扰对准等思想进行凝炼，提出适用于随机信道系数的嵌套对准方法；在多天线多用户干扰信道下，通过发掘子空间正交与集合嵌套之间的内在联系，提出幅度空间多维嵌套与矢量空间干扰对准相统一的研究框架；在多信道干扰网络中，提出以交叉干扰链路或其它冗余链路传递干扰信息辅助进行干扰删除的方法。本项目着眼于主动创造干扰消除的机会，研究成果不仅可以大幅提高蜂窝网络的空间容量，而且为干扰信道下的协作通信开拓新的发展思路。

随着未来移动数据业务千倍量级的增长需求，蜂窝网络日益向多层异构的形式发展，小区形态发生根本变化，小区间干扰变得更加复杂，尤其是出现了严重的异层小区间干扰，需要研究新的小区间干扰协调和消除方法。本项目抓住电波传播过程中具有路径损耗这一自然特性，根据异构网络中各基站和用户位置的差别，对幅度空间中出现的传输机会进行高效利用。提出了宏小区用户与微小区用户的幅度空间共享策略；在单天线多用户干扰信道下，基于分层调制、信号嵌套、干扰对准的思想，提出了可工作于任意信道系数下的嵌套对准方法。随后将信号嵌套理论推广到高维空间当中，从而可以在多天线多用户干扰信道下进行嵌套对准。嵌套对准是传统线性干扰对准理论的进一步推广，干扰不再局限于对准在与期望信号正交的子空间上，部分干扰也可以和期望信号共享一个子空间，这大大提升了干扰抑制方法设计的灵活性。我们把这种思想用在多天线广播信道下进行非正交多用户预编码设计，也用在密集蜂窝网络下进行分布式小区间干扰协调。在多载波并行干扰信道中，我们还提出多信道联合编码的方法，以干扰强弱划分信道类型，其中强干扰子载波的交叉链路传递干扰信息辅助弱干扰子载波的直传链路进行干扰删除， 从而提高信道的可达数据率。在小区间干扰协调方面，我们将等待机会的被动干扰删除方法推广到创造机会的主动干扰删除方法，在三维大规模天线和毫米波信道等新的应用场景下提高了多用户干扰和小区间干扰的抑制能力。项目提出的若干方法不仅提高了多层异构蜂窝网络的空间容量，还为干扰信道下的协作机制提供了新的发展思路。