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Advanced Signal Processing Techniques for Two-Way Relaying Networks and Full-Duplex Communication Systems

机译：用于双向中继网络和全双工通信系统的高级信号处理技术

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摘要

To enable ultra-high data rate and ubiquitous coverage in future wirelessnetworks, new physical layer techniques are desired. Relaying is apromising technique for future wireless networks since it can boost thecoverage and can provide low cost wireless backhauling solutions, ascompared to traditional wired backhauling solutions via fiber and copper.Traditional one-way relaying (OWR) techniques suffer from the spectral lossdue to the half-duplex (HD) operation at the relay. On one hand, two-wayrelaying (TWR) allows the communication partners to transmit to and/orreceive from the relay simultaneously and thus uses the spectrum moreefficiently than OWR. Therefore, we study two-way relays and morespecifically multi-pair/multi-user TWR systems with amplify-and-forward(AF) relays. These scenarios suffer from inter-pair or inter-userinterference. To deal with the interference, advanced signal processingalgorithms, in other words, spatial division multiple access (SDMA)techniques, are desired. On the other hand, if the relay is a full-duplex(FD) relay, the spectral loss due to a HD operation can also becompensated. However, in practice, a FD device is hard to realize due tothe strong loop-back self-interference and the limited dynamic range at thetransceiver. Thus, advanced self-interference suppression techniques shouldbe developed. This thesis contributes to the two goals by developingoptimal and/or efficient algebraic solutions for different scenariossubject to different utility functions of the system, e.g., sum ratemaximization and transmit power minimization. In the first part of thisthesis, we first study a multi-pair TWR network with a multi-antenna AFrelay. This scenario can be also treated as the sharing of the relay andthe spectrum among multiple operators assuming that different pairs ofusers belong to different operators. Existing approaches focus oninterference suppression. We propose a projection based separation ofmultiple operators (ProBaSeMO) scheme, which can be easily extended wheneach user has multiple antennas or when different system design criteriaare applied. To benchmark the ProBaSeMO scheme, we develop optimal relaytransmit strategies to maximize the system sum rate, minimize the requiredtransmit power at the relay, or maximize the minimum signal to interferenceplus noise ratio (SINR) of the users. Specifically for the sum ratemaximization problem, gradient based methods are developed regardlesswhether each user has a single antenna or multiple antennas. To guarantee aworst-case polynomial time solution, we also develop a polynomial timealgorithm which has been inspired by the polynomial time difference ofconvex functions (POTDC) method. Finally, we analyze the conditions forobtaining the sharing gain in terms of the sum rate. Then we study the sumrate maximization problem of a multi-pair TWR network with multiple singleantenna AF relays and single antenna users. The resulting sum ratemaximization problem, subject to a total transmit power constraint of therelays in the network, yields a similar problem structure as in theprevious scenario. Therefore the optimal solution for one scenario can beused for the other. Moreover, a global optimal solution, which is based onthe polyblock approach, and several suboptimal solutions, which are morecomputationally efficient and approximate the optimal solution, aredeveloped when there is a total transmit power constraint of the relays inthe network or each relay has its own transmit power constraint. We thenshift our focus to a multi-pair TWR network with multiple multi-antenna AFrelays and multiple dumb repeaters. This scenario is more general becausethe previous two scenarios can be seen as special realizations of thisscenario. The interference management in this scenario is more challengingdue to the existence of the repeaters. Interference neutralization (IN) isa solution for dealing with this kind of interference. Thereby, necessaryand sufficient conditions for neutralizing the interference are derived.Moreover, a general framework to optimize different system utilityfunctions in this network with or without IN is developed regardlesswhether the AF relays in the network have a total transmit power limit orindividual transmit power limits. Finally, we develop the relay transmitstrategy as well as base station (BS) precoding and decoding schemes for aTWR assisted multi-user MIMO (MU-MIMO) downlink channel. Compared to themulti-pair TWR network, this scenario suffers from the co-channelinterference. We develop three suboptimal algorithms which are based onchannel inversion, ProBaSeMO and zero-forcing dirty paper coding (ZFDPC),which has a low computational complexity, provides a balance between theperformance and the complexity, and suffers only a little when the systemis heavily loaded, respectively.In the second part of this thesis, weinvestigate self-interference (SI) suppression techniques to exploit the FDgain for a point-to-point MIMO system. We first develop SI aware transmitstrategies, which provide a balance between the SI suppression and themultiplexing gain of the system. To get the best performance, perfectchannel state information (CSI) is needed, which is imperfect in practice.Thus, worst case transmit strategies to combat the imperfect CSI aredeveloped, where the CSI errors are modeled deterministically and boundedby ellipsoids. In real word applications, the RF chain is imperfect. Thisaffects the performance of the SI suppression techniques and thus resultsin residual SI. We develop efficient transmit beamforming techniques, whichare based on the signal to leakage plus noise ratio (SLNR) criterion, todeal with the imperfections in the RF chain. All the proposed designconcepts can be extended to FD OWR systems.
机译：为了在未来的无线网络中实现超高数据速率和无处不在的覆盖，需要新的物理层技术。与通过光纤和铜缆的传统有线回程解决方案相比，中继是未来无线网络的一项有前景的技术，因为它可以扩大覆盖范围并提供低成本的无线回程解决方案。传统的单向中继（OWR）技术由于频谱损耗而损失了一半。中继上的双工（HD）操作。一方面，双向中继（TWR）允许通信伙伴同时向中继发送和/或从中继接收，因此比OWR更有效地使用频谱。因此，我们研究了双向中继，尤其是带有放大转发（AF）中继的多对/多用户TWR系统。这些方案受到线对或用户之间的干扰。为了处理干扰，需要高级信号处理算法，换句话说，空分多址（SDMA）技术。另一方面，如果该继电器是全双工（FD）继电器，则由于HD操作而引起的频谱损失也可以得到补偿。但是，实际上，由于强大的环回自干扰和收发器的动态范围有限，FD设备很难实现。因此，应该开发先进的自干扰抑制技术。通过针对系统的不同效用函数，例如求和率最大化和发射功率最小化，针对不同情况开发最优和/或有效的代数解，本论文对两个目标做出了贡献。在本文的第一部分，我们首先研究了具有多天线AF中继的多对TWR网络。假设不同的用户对属于不同的运营商，则该场景也可以视为多个运营商之间的中继和频谱共享。现有方法集中于干扰抑制。我们提出了一种基于投影的多操作符分离（ProBaSeMO）方案，当每个用户有多个天线或应用了不同的系统设计标准时，可以轻松扩展该方案。为了对ProBaSeMO方案进行基准测试，我们开发了最佳的中继传输策略，以最大程度地提高系统总速率，最小化中继站所需的传输功率或最大化用户的最小信噪比与噪声比（SINR）。专门针对总速率最大化问题，无论每个用户使用一个天线还是多个天线，都开发了基于梯度的方法。为了保证最坏情况的多项式时间解，我们还开发了一种多项式时间算法，该算法受凸函数的多项式时间差（POTDC）方法的启发。最后，我们根据总和率分析了获得共享收益的条件。然后，我们研究了具有多个单天线AF继电器和单天线用户的多对TWR网络的总和最大化问题。受网络中中继总发射功率约束的结果，总和速率最大化问题产生了与先前情形类似的问题结构。因此，一种方案的最佳解决方案可用于另一种方案。此外，当网络中存在中继的总发射功率约束或每个中继都有自己的发射时，将开发基于多块方法的全局最优解以及几种计算效率更高且近似最优解的次优解。功率约束。然后，我们将重点转移到具有多个多天线AF中继器和多个哑中继器的多对TWR网络。此方案比较笼统，因为前两个方案可以看作是此方案的特殊实现。由于存在中继器，因此在这种情况下的干扰管理更具挑战性。干扰中和（IN）是用于处理此类干扰的解决方案。从而，得出了消除干扰的必要和充分条件。此外，无论网络中的AF中继器是否具有总发射功率限制或单个发射功率限制，都开发了优化该网络中具有或不具有IN的不同系统实用功能的通用框架。最后，我们为TWR辅助的多用户MIMO（MU-MIMO）下行链路信道开发了中继传输策略以及基站（BS）预编码和解码方案。与多对TWR网络相比，这种情况遭受了同信道干扰。我们开发了基于信道反转，ProBaSeMO和迫零脏纸编码（ZFDPC）的三种次优算法，它们具有较低的计算复杂度，可以在性能和复杂度之间取得平衡，并且在系统负载较重时仅会遭受很少的损失，分别在本文的第二部分，我们研究了自干扰（SI）抑制技术，以将FDgain用于点对点MIMO系统。我们首先开发出具有SI意识的传输策略，该策略可在SI抑制和系统的多路复用增益之间取得平衡。为了获得最佳性能，需要有完美的信道状态信息（CSI），这在实践中是不完善的。因此，开发了针对不完善CSI的最坏情况的传输策略，其中确定性地建模CSI错误并以椭球为边界。在实际应用中，RF链是不完善的。这会影响SI抑制技术的性能，从而导致残留SI。我们开发有效的发射波束成形技术，该技术基于信噪比与噪声比（SLNR）标准，以应对RF链中的缺陷。所有提出的设计概念都可以扩展到FD OWR系统。

著录项

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    Zhang Jianshu;

  • 作者单位
  • 年度 2015
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  • 原文格式 PDF
  • 正文语种 eng
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