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Enabling Technologies for Next Generation Wireless Local Area Networks (WLANs)

机译：下一代无线局域网（WLAN）的启用技术

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摘要

Next-generation wireless local area networks (WLANs) address two major challenges. The first is the flexibility to provide significantly increased users' throughput due to the current evolution of the Internet usage toward real-time high-definition video content. Multi-input multi-output (MIMO) transmission at both access points (APs) and stations (STAs) is one of the key technologies to achieve high throughput in WLANs for both single-user MIMO (SUMIMO) and downlink multi-user MIMO (MU-MIMO). This requires APs and STAs to effi- ciently communicate while addressing challenging design trade-offs between energy efficiency, implementation complexity, and overall network spectral efficiency. In current WLANs, implementing MIMO techniques for SU-MIMO, which utilizes multiple radio-frequency (RF) chains, has become the norm. Thus, using a small number of RF chains, and ideally a single RF chain, is highly desirable for future low-power devices. The second challenge is dense deployment scenarios where many heterogeneous devices, from high-end laptops to low-power Internet of Things (IoT) devices and wearables, must coexist and operate reliably. In these dense scenarios, most relevant challenges in MU-MIMO are related to interference issues, which increase the packet error. In this dissertation, we focus on enhancing the user experience in SU-MIMO transmission and improving interference management techniques in MU-MIMO transmission for dense deployment WLAN scenarios.;For SU-MIMO, we adopt Spatial Modulation (SM) as a single- (or few-) RF MIMO transmission technique that efficiently uses multiple antennas while addressing challenging design trade-offs between energy efficiency, implementation complexity, and overall network spectral efficiency. This motivates SM-based transmission for low-power IoT devices providing a better user experience for dense environments. We analyze the robustness of SM-based direct-conversion transceivers under transmit in-phase/quadrature (I/Q) imbalance. Then, we propose temporal modulation as a new dimension to enhance the performance of spatiallymodulated space-time block codes (STBC) while achieving a full transmit diversity order. Based on our proposed codebook, we propose the first differential transmission scheme for spatial modulation with multiple active transmit antennas.;For the multi-stream MU-MIMO interference networks, we study the problem of per-stream maximum sum-rate (MSR) joint precoder and minimum mean-squared error (MMSE) equalizer design for the scenarios where multiple independent transmitters send data streams to corresponding different receivers via a shared channel forming an interference environment. We propose a generalized iterative algorithm which directly maximizes the sum-rate without assuming the signal-to-noise ratio (SNR) to be infinite. To reduce complexity, which can become prohibitive for large network size, we examine the performance-complexity tradeoffs involved in a sparse equalizer design. Joint precoder and equalizer optimization requires alternation between the forward and reverse links and assumes perfect synchronization between the transmitters and receivers at each network node, resulting in extensive overhead and spectral efficiency loss. To overcome this serious drawback, we propose a new design approach based on weighted-sum-rate maximization assuming a virtual equalizer type at the transmitter to limit the optimization process to the transmitter side. Finally, we quantify the sum-rate loss due to mismatched equalizer types and demonstrate the robustness of our proposed sum-rate weighting strategy to such mismatches with perfect or imperfect channel knowledge.
机译：下一代无线局域网（WLAN）解决了两个主要挑战。首先是由于互联网使用的当前向实时高清视频内容的发展，可以灵活地显着提高用户的吞吐量。接入点（AP）和站点（STA）上的多输入多输出（MIMO）传输是在WLAN中实现单用户MIMO（SUMIMO）和下行链路多用户MIMO（ MU-MIMO）。这要求AP和STA有效通信，同时解决能源效率，实现复杂性和整体网络频谱效率之间的挑战性设计折衷。在当前的WLAN中，实现用于SU-MIMO的MIMO技术已成为常态，该技术利用了多个射频（RF）链。因此，对于未来的低功率设备，非常希望使用少量的RF链，理想情况下使用单个RF链。第二个挑战是密集的部署场景，其中许多异构设备（从高端笔记本电脑到低功耗的物联网（IoT）设备和可穿戴设备）必须共存并可靠地运行。在这些密集场景中，MU-MIMO中最重要的挑战与干扰问题有关，这会增加数据包错误。本文主要针对在密集部署的WLAN场景中，致力于增强用户在SU-MIMO传输中的使用体验，以及改善MU-MIMO传输中的干扰管理技术。对于SU-MIMO，我们采用空间调制（SM）作为单-（ RF MIMO传输技术，可以有效使用多个天线，同时解决能源效率，实现复杂性和整体网络频谱效率之间的挑战性设计折衷。这激励了针对低功率IoT设备的基于SM的传输，从而为密集环境提供了更好的用户体验。我们分析了在传输同相/正交（I / Q）不平衡下基于SM的直接转换收发器的鲁棒性。然后，我们提出时间调制作为一种新的维度，以增强空间调制空时分组码（STBC）的性能，同时实现完整的传输分集阶数。在我们提出的密码本的基础上，我们提出了第一种用于具有多个有源发射天线的空间调制的差分传输方案。对于多流MU-MIMO干扰网络，我们研究了每流最大和率（MSR）联合问题预编码器和最小均方误差（MMSE）均衡器设计，用于以下情况：多个独立的发射机通过共享信道将数据流发送到相应的不同接收机，形成干扰环境。我们提出了一种广义的迭代算法，该算法可直接使总和速率最大化，而无需将信噪比（SNR）设为无限大。为了降低复杂度（对于大型网络而言，复杂度可能会变得过高），我们研究了稀疏均衡器设计中涉及的性能复杂度折衷。联合的预编码器和均衡器优化需要在前向链路和反向链路之间进行交替，并假定每个网络节点上的发送器和接收器之间都实现了完美的同步，从而导致大量的开销和频谱效率损失。为了克服这个严重的缺点，我们提出了一种基于加权总和速率最大化的新设计方法，该方法假设在发射机处使用虚拟均衡器类型，以将优化过程限制在发射机端。最后，我们对均衡器类型不匹配造成的和率损失进行量化，并证明了我们提出的求和率加权策略对具有完美或不完善信道知识的这种不匹配的鲁棒性。

著录项

  • 作者

    Mohamed, Ahmed Gamal Helmy.;

  • 作者单位

    The University of Texas at Dallas.;

  • 授予单位 The University of Texas at Dallas.;
  • 学科 Electrical engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 141 p.
  • 总页数 141
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 康复医学;
  • 关键词

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