Abstract

Interference channel, in which multiple user pairs communicate over shared resources, is a building block of communications networks. Here, the K-user interference channel (IC) aided by J instantaneous relays (IRs), i.e. relays without delay, is considered. For KICJR networks, where \(K>2\) and \(J>1\), the DoF performance and achievable schemes have not been investigated in literature. Here, we devise a novel achievable scheme, called restricted interference alignment (RIA), which restricts the received interference from each source at each destination in a limited sub-space, and then, aligns the restricted interferences. Furthermore, we develop an analytical tool for finding a tight upper bound on DoF of KICJR networks by analyzing the properness of the interference alignment equations. Moreover, we develop linear beamforming design for sources and relays based on the mean square error (MSE) minimization, as an achievable scheme. The performance evaluation results show that the achievable sum DoF by using the proposed RIA scheme and the MSE-based beamforming design match well with the derived upper bounds. Furthermore, the results confirm that the achieved sum DoF using the RIA scheme outperforms the existing achievable schemes. Motivated by these promising results, we further investigate impact of IRs in providing physical layer security, i.e. achieving secure DoF in interference networks. Specifically, we derive a lower bound on the achievable secure DoF by devising an achievable scheme, called transmission in the null space (TNS). This scheme makes the cross channels rank deficient and enables sources to select their transmit filters in the constructed null spaces. Performance evaluation shows that by leveraging IRs, the secure DoF performance of interference networks could be increased significantly. The proposed analytical framework in this work for rank deficiency-powered DoF analysis is expected to also attract attention from other research areas, e.g. beamforming design for millimeter wave communications.

中文翻译：

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具有瞬时中继的K用户MIMO干扰信道的DoF和安全DoF

摘要

多个用户对通过共享资源进行通信的干扰通道是通信网络的基础。在此，考虑了由J个瞬时继电器（IR）辅助的K用户干扰信道（IC ），即无延迟的继电器。对于K IC J R网络，其中\（K> 2 \）和\（J> 1 \），DoF性能和可实现的方案尚未在文献中进行研究。在这里，我们设计了一种新颖的可实现方案，称为受限干扰对齐（RIA），该方案将来自每个源在每个目的地的接收干扰限制在受限子空间中，然后对齐受限干扰。此外，我们开发了一种分析工具，用于确定K IC J的DoF的严格上限通过分析干扰对准方程的正确性来建立R网络。此外，我们基于均方误差（MSE）最小化为源和继电器开发线性波束成形设计，作为可实现的方案。性能评估结果表明，使用所提出的RIA方案和基于MSE的波束成形设计可以实现的总DoF与导出的上限非常匹配。此外，结果证实了使用RIA方案获得的总DoF优于现有的可实现方案。受这些有希望的结果的激励，我们进一步研究了IR在提供物理层安全性（即在干扰网络中实现安全的DoF）方面的影响。具体来说，我们通过设计一种可实现的方案（称为零空间传输（TNS））来得出可实现的安全DoF的下限。该方案使交叉信道秩不足，并使源能够在构造的空空间中选择其发送滤波器。性能评估表明，通过利用IR，可以显着提高干扰网络的安全DoF性能。这项工作中为等级缺陷驱动的自由度分析提出的分析框架有望引起其他研究领域的关注，例如毫米波通信的波束成形设计。