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

機譯：下一代無線局域網(wǎng)（WLAN）的啟用技術

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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.
機譯：下一代無線局域網(wǎng)（WLAN）解決了兩個主要挑戰(zhàn)。首先是由于互聯(lián)網(wǎng)使用的當前向實時高清視頻內(nèi)容的發(fā)展，可以靈活地顯著提高用戶的吞吐量。接入點（AP）和站點（STA）上的多輸入多輸出（MIMO）傳輸是在WLAN中實現(xiàn)單用戶MIMO（SUMIMO）和下行鏈路多用戶MIMO（ MU-MIMO）。這要求AP和STA有效通信，同時解決能源效率，實現(xiàn)復雜性和整體網(wǎng)絡頻譜效率之間的挑戰(zhàn)性設計折衷。在當前的WLAN中，實現(xiàn)用于SU-MIMO的MIMO技術已成為常態(tài)，該技術利用了多個射頻（RF）鏈。因此，對于未來的低功率設備，非常希望使用少量的RF鏈，理想情況下使用單個RF鏈。第二個挑戰(zhàn)是密集的部署場景，其中許多異構設備（從高端筆記本電腦到低功耗的物聯(lián)網(wǎng)（IoT）設備和可穿戴設備）必須共存并可靠地運行。在這些密集場景中，MU-MIMO中最重要的挑戰(zhàn)與干擾問題有關，這會增加數(shù)據(jù)包錯誤。本文主要針對在密集部署的WLAN場景中，致力于增強用戶在SU-MIMO傳輸中的使用體驗，以及改善MU-MIMO傳輸中的干擾管理技術。對于SU-MIMO，我們采用空間調制（SM）作為單-（ RF MIMO傳輸技術，可以有效使用多個天線，同時解決能源效率，實現(xiàn)復雜性和整體網(wǎng)絡頻譜效率之間的挑戰(zhàn)性設計折衷。這激勵了針對低功率IoT設備的基于SM的傳輸，從而為密集環(huán)境提供了更好的用戶體驗。我們分析了在傳輸同相/正交（I / Q）不平衡下基于SM的直接轉換收發(fā)器的魯棒性。然后，我們提出時間調制作為一種新的維度，以增強空間調制空時分組碼（STBC）的性能，同時實現(xiàn)完整的傳輸分集階數(shù)。在我們提出的密碼本的基礎上，我們提出了第一種用于具有多個有源發(fā)射天線的空間調制的差分傳輸方案。對于多流MU-MIMO干擾網(wǎng)絡，我們研究了每流最大和率（MSR）聯(lián)合問題預編碼器和最小均方誤差（MMSE）均衡器設計，用于以下情況：多個獨立的發(fā)射機通過共享信道將數(shù)據(jù)流發(fā)送到相應的不同接收機，形成干擾環(huán)境。我們提出了一種廣義的迭代算法，該算法可直接使總和速率最大化，而無需將信噪比（SNR）設為無限大。為了降低復雜度（對于大型網(wǎng)絡而言，復雜度可能會變得過高），我們研究了稀疏均衡器設計中涉及的性能復雜度折衷。聯(lián)合的預編碼器和均衡器優(yōu)化需要在前向鏈路和反向鏈路之間進行交替，并假定每個網(wǎng)絡節(jié)點上的發(fā)送器和接收器之間都實現(xiàn)了完美的同步，從而導致大量的開銷和頻譜效率損失。為了克服這個嚴重的缺點，我們提出了一種基于加權總和速率最大化的新設計方法，該方法假設在發(fā)射機處使用虛擬均衡器類型，以將優(yōu)化過程限制在發(fā)射機端。最后，我們對均衡器類型不匹配造成的和率損失進行量化，并證明了我們提出的求和率加權策略對具有完美或不完善信道知識的這種不匹配的魯棒性。

著錄項

  • 作者

    Mohamed, Ahmed Gamal Helmy.;

  • 作者單位

    The University of Texas at Dallas.;

  • 授予單位 The University of Texas at Dallas.;
  • 學科 Electrical engineering.
  • 學位 Ph.D.
  • 年度 2017
  • 頁碼 141 p.
  • 總頁數(shù) 141
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 康復醫(yī)學;
  • 關鍵詞

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