Unquantized and Uncoded Channel State Information Feedback in Multiple Antenna Multiuser Wireless Systems

多天线技术的潜力和前景现在已经导致广泛考虑在各种情况下使用这些技术：用于下一代蜂窝系统中的广域宽带无线传输；蜂窝系统中局部热点数据业务的覆盖用于新兴的短距离无线局域网；促进在无牌频带内有效共享频谱；以及无线自组织网络中的各种协作技术。在上述任何情况下，任何多天线技术成功所需的一个关键属性是需要可靠和有效的信道状态信息（CSI）。无线应用对时延的要求以及信道的时变，不仅要求CSI信息的可靠性，而且要求这些信息的反馈要快速、频繁。本课题研究可用于多天线多用户无线通信系统的CSI反馈方案的基本限制。研究的一个基本问题是可靠的CSI反馈是否有必要在香农理论意义上进行最佳量化和编码？具体而言，研究了非量化和非编码（UQ-UC） CSI反馈方案，该方案具有避免了量化和编码所带来的延迟的吸引人的特点，同时在涉及无线信道上行和下行的某些情况下仍然是最优的。在这种“零延迟”方案不是最优的情况下，通过(a) FDD和TDD系统中UQ-UC CSI反馈的性能边界，(b) CSI反馈接收器，(c)多天线多用户系统中发射机优化的信息容量，以及(d)对UQ-UC CSI反馈与实际编码传输的比较评估来研究可以大幅提高性能的增强。

The potential and promise of multiple antenna techniques has now resulted in widespread considerations for the use of these in a variety of contexts: for wide area wideband wireless transmission in next generation cellular systems; for local area hot-spot data service overlays in cellular systems; for emerging short-range wireless LAN networks; for promoting efficient spectrum sharing in the unlicensed bands; and a variety of collaborative techniques in wireless adhoc networks. A key attribute required of any multiple antenna technique to be successful, in any of the above contexts, is the need for reliable and efficient channel state information (CSI). Delay requirements imposed by wireless applications and the time variations in the channel, require not only reliability in CSI information, but also that the feedback of such information be fast and frequent. This project studies the fundamental limits of CSI feedback schemes that can be used in multiple antenna multiuser wireless communication systems. A fundamental issue studied is if it is necessary for reliable CSI feedback to be optimally quantized and encoded in a Shannon theoretic sense? Specifically, unquantized and uncoded (UQ-UC) CSI feedback schemes are studied, that have the attractive feature of avoiding the delays due to quantization and coding, while still being optimal in certain situations relating to the uplink and downlink of wireless channels. In cases where such "zero-delay" schemes are sub-optimal, enhancements that can substantially improve performance are studied via (a) performance bounds for UQ-UC CSI feedback in FDD and TDD systems, (b) CSI feedback receivers, (c) information capacity of transmitter optimization in multiple antenna multiuser systems, and (d) comparative evaluation of UQ-UC CSI feedback with practical coded transmission.