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在各种环境中使用这些技术的广泛考虑：用于下一代蜂窝系统中的广域宽带无线传输；用于蜂窝系统中的局域热点数据服务覆盖；用于新兴的短距离无线局域网网络；用于促进在未经许可的频段中的有效频谱共享；以及用于无线自组织网络中的各种协作技术。在上述任何上下文中，任何多天线技术成功所需的关键属性是需要可靠和高效的信道状态信息(CSI)。无线应用对时延的要求以及信道中的时间变化，不仅要求CSI信息的可靠性，而且要求此类信息的反馈快速而频繁。本项目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反馈是否需要在香农理论意义上进行最佳量化和编码？具体地说，研究了未量化和未编码(UQ-UC)的CSI反馈方案，其具有避免量化和编码造成的延迟的吸引人的特征，同时在与无线信道的上行链路和下行链路相关的某些情况下仍然是最优的。在这种“零延迟”方案是次优的情况下，通过(A)FDD和TDD系统中UQ-UC CSI反馈的性能界限，(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)UQ-UC CSI反馈与实际编码传输的比较评估，研究能够显著提高性能的增强。

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.