Convex Optimization Based Robust Spatial Multiplexing Techniques for Downlink Multiuser Wireless Systems

基于凸优化的下行多用户无线系统鲁棒空间复用技术

• 批准号: EP/G020442/1
• 负责人: Sangarapillai Lambotharan
• 金额: $ 32.65万
• 依托单位: Loughborough University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG020442%2F1
• 关键词: Convex; Optimization; Based; Robust; Spatial

The demand for high speed data transmission over wireless access is growing steadily due to rich multimedia applications such as video streaming, music and interactive services. The expectation is to enable wireless access to provide the same data rate and quality of services (QoS) as that provided by wire-line counterparts. This requires provision of beyond 100 Mb/s and preferably 1Gb/s wireless access. The data rates of wireless systems can be increased by exploiting spatial diversity provided by multiple antennas at the transmitter and receivers. A basestation could serve multiple users simultaneously in the same frequency band using downlink spatial multiplexing techniques. For a frequency division duplex (FDD) based system, the use of multiple antennas at the transmitter however requires feedback of channel state information (CSI) from the receiver. Such channel state information when used at the transmitter will always be inaccurate due to channel estimation error, quantization of the estimates (due to finite budget for bit feedback) and relative motion between the transmitter and receiver. For example, when the channel is changing moderately fast, due to feedback delay, by the time the transmitter uses the channel state information, the true forward channel would have changed. The error which is the difference between the true channel and the estimates available at the transmitter could seriously degrade the transmitter diversity performance. Therefore, it is very important to consider the channel state information error when designing transmitter diversity techniques for the enhancement of capacity or coverage.Motivated by the rich theoretical and experimental results on the benefits of transmitter diversity techniques for wireless multiuser systems, we propose to develop advanced signal processing techniques to mitigate this very important and practical problem of imperfect channel state information at the basestation, a major limitation for using these diversity techniques in a highly hostile downlink channel environment. The research will be focused on developing robust beamformers/transmit diversity techniques that are resilient to channel state information error, using convex optimization techniques such as second order cone programming and semidefinite programming. The performance (in terms of bit error rate (BER), coded BER (CBER) and throughput) will be compared against conventional non-robust techniques for various channel fading profiles obtained using simulations and real field data provided through QinetiQ, facilitated by Professor Malcolm Macleod. This project has a distinct advantage of European collaboration with Prof. Alex Gershman who is a world renowned expert on robust beamforming and array processing techniques, and this window of opportunity should not be lost as we believe this provides an excellent vehicle for UK's standing in the field of robust design and array signal processing at an international level.

由于视频流、音乐和交互式服务等丰富的多媒体应用，对通过无线接入进行高速数据传输的需求正在稳步增长。期望是使无线接入能够提供与有线对应方所提供的相同的数据速率和服务质量（QoS）。这需要提供超过100 Mb/s的无线接入，最好是1Gb/s的无线接入。无线系统的数据速率可以通过利用由发射机和接收机处的多个天线提供的空间分集来增加。基站可以使用下行链路空间复用技术在同一频带中同时为多个用户服务。然而，对于基于频分双工（FDD）的系统，在发射机处使用多个天线需要来自接收机的信道状态信息（CSI）的反馈。由于信道估计误差、估计的量化（由于比特反馈的有限预算）以及发射机和接收机之间的相对运动，在发射机处使用这种信道状态信息时总是不准确的。例如，当信道由于反馈延迟而适度快速地改变时，到发射机使用信道状态信息时，真实的前向信道将已经改变。真实信道与发射机处可用的估计之间的差的误差会严重降低发射机分集性能。因此，在设计发射分集技术以提高系统容量或覆盖范围时，考虑信道状态信息误差是非常重要的。我们建议开发先进的信号处理技术，以缓解信道状态信息不完整这一非常重要且实际的问题。在高度不利的下行链路信道环境中使用这些分集技术的主要限制。研究将集中在开发强大的波束形成器/发射分集技术，是弹性的信道状态信息错误，使用凸优化技术，如二阶锥规划和半定规划。性能（在误码率（BER），编码BER（CBER）和吞吐量方面）将与传统的非鲁棒性技术的各种信道衰落曲线使用模拟和真实的现场数据通过QinetiQ，由教授马尔科姆麦克劳德促进获得比较。该项目与Alex Gershman教授的欧洲合作具有明显的优势，Alex Gershman教授是世界知名的稳健波束形成和阵列处理技术专家，我们不应该错过这个机会，因为我们相信这为英国在稳健设计和阵列信号处理领域的国际地位提供了一个很好的工具。