Interference Management in MIMO Wireless Networks

随着对支持更高比特率的无线通信服务的需求不断增长，通过同时多个传输来重复使用相同的频谱来提高通信系统的带宽效率的需求日益迫切。要解决这一问题和许多其他问题，最成功和最有效的解决方案之一是部署多输入多输出(MIMO)技术。然而，多用户(MU)MIMO系统通常采用非优化方法来处理限制网络容量的干扰。因此，该提案寻求设计信号处理策略和无线网络协议来管理MU MIMO系统中的干扰，以实现最高的网络吞吐量。 处理干扰的传统方法是(I)通过在时间或频域中不重叠的传输来避免干扰，(Ii)将其他发射机的信号集中为噪声并通过功率控制来减轻它，或(Iii)采用多用户译码。在利用空间信令维度来并行服务多个用户的MU-MIMO系统中，存在通过在终端处的线性预编码和功率控制来对干扰进行整形以最小化在目的地的组合干扰的影响的机会。 在该方案中，我们试图通过将少数强发射机的信号对准和非协调传输的干扰消除相结合来制定策略来处理MU MIMO系统中的干扰。具体地说，通过精心设计预处理向量和传输调度，我们期望包含相关信息的信号将根据所选择的编码策略对齐到适当的空间维度。传输方案也将被优化，以降低计算复杂度并提高时频利用率。这项工作的范围将涵盖单跳、多跳和多路网络。在多跳系统中，源和目的地通过一个或多个充当中继的其他节点进行通信，我们计划利用物理层网络编码的概念来帮助无线网络的操作，其中节点根据泊松过程分布在空间中。这里我们的重点是用于功率分配的媒体接入(用户选择)机会，重点是用于中继间干扰消除的拓扑控制和路由级别的问题。我们希望在这里部署随机几何的分析工具，通过平均终端的所有潜在几何模式来计算无线网络的宏观属性。这项工作的挑战将是评估所部署的信号对准技术的增益，其中所有终端可能不是同步的或完全合作的。

With the growing demands for wireless communication services to support higher bit rates, there is an ever-pressing need to increase bandwidth efficiency of communication systems through the reuse of the same spectrum by simultaneous multiple transmissions. To address this and many other issues, one of the most successful and efficient solutions is the deployment of Multiple-Input Multiple-Output (MIMO) technology. However, the multi-user (MU) MIMO systems are often designed to use non-optimized methods to deal with the interference limiting the network capacity. As a result, this proposal seeks to design signal processing strategies and wireless network protocols that manage interference in MU MIMO systems to achieve the highest network throughput. Conventional approaches to deal with interference are (i) to avoid interference by non-overlapping transmissions in time or frequency domains, (ii) lump other transmitters' signals as noise and mitigate it through power control, or (iii) deploy multi-user decoding. In MU-MIMO systems, where the spatial signaling dimension is utilized to serve many users in parallel, there are opportunities for shaping the interference through linear pre-coding at the terminals and power control to minimize the effects of the combined interference at the destinations. In this proposal, we seek to develop strategies to deal with interference in MU MIMO systems by integrating signal alignment for few strong transmitters and interference cancellation for non-coordinated transmissions. Specifically, by a thoughtful design of pre-processing vectors and scheduling of transmissions, we expect that the signals with relevant information will be aligned into proper spatial dimensions according to the selected coding strategies. The transmission schemes will be also optimized to reduce computational complexity and to improve time-frequency utilization. The scope of this work will cover single-hop, multi-hop, and multi-way networks. In multi-hop systems, where a source and destination communicate through one or more other nodes that act as a relay, we plan to exploit the concept of physical layer network coding to aid the operation of the wireless network with the nodes distributed in space according to the Poisson-point process. Our focus here is on medium access (user selection) opportunities for power allocation, with emphasis on the topology control and routing-level issues for inter-relay interference cancellation. We expect here to deploy for analysis the tools from stochastic geometry which computes macroscopic properties of wireless networks, by averaging over all potential geometrical patterns for the terminals. The challenge in this work will be to evaluate the gains from the deployed signal alignment techniques where all terminals may not be synchronized or fully cooperating.