Communications through time-varying subspace channels

通过时变子空间通道进行通信

• 批准号: 0725366
• 负责人: Benjamin Friedlander
• 金额: $ 28.1万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-10-01 至 2011-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0725366&HistoricalAwards=false
• 关键词: Communications; through; time; varying; subspace

The ``wireless revolution" and the ever increasing need to communicate on the move is continually bringing up new engineering problems and challenges. One of these challenges is the design of communication systems capable of delivering high data rates over random time-varying channels. An extensive body of work exists on the analysis and design of mobile wireless communication systems. Almost invariably these works assume that the channel variations are relatively slow so that the channel can be considered to be approximately constant over a block of symbols. Thus, the fundamental operation of existing mobile communication systems is the same as in systems designed for time-invariant channels. Various methods such as powerful error correcting codes, channel equalizers, and spatial or temporal diversity are used post-facto to mitigate the effects of the time-varying channel. This research project is developing novel communication systems for channels which vary so rapidly that the performance of conventional communication systems is severely degraded.A fundamental assumption underlying the design of a wide range of digital communication systems is that the receiver has the ability to estimate the radio or acoustic propagation channel, and to use that estimate in the detection process. In random rapidly time-varying channels with large Doppler and delay spreads, reliable channel estimation is not possible. This project considers the problem of designing a communication system when the channel realization is unknown and inestimable, and only the statistics of the channel are known (or can be estimated). Thus, the channel realization is only known to lie somewhere in a subspace whose dimension is the rank of the channel covariance matrix. The unit-rank case reduces this to a known class of communication problems. However, the case where the rank is greater than unity requires a significant extension of current theory. This problem formulation leads to new receiver structures and novel ways of designing communication systems which must operate in harsh time-varying environments. This project is developing optimal and sub-optimal solutions for communications through subspace channels and an analysis of their performance. Various types of communication systems are being studied including: single-input single-output systems operating through frequency selective channels, MIMO systems, and multi-user and multi-access systems.

“无线革命”和不断增长的移动通信需求不断带来新的工程问题和挑战。这些挑战之一是设计能够在随机时变信道上提供高数据速率的通信系统。在移动的无线通信系统的分析和设计方面存在大量的工作。这些工作几乎总是假设信道变化相对较慢，使得信道可以被认为在符号块上近似恒定。因此，现有的移动的通信系统的基本操作与为时不变信道设计的系统中的基本操作相同。各种方法，如强大的纠错码，信道均衡器，和空间或时间分集事后使用，以减轻随时间变化的信道的影响。 本研究课题是针对信道变化快、传统通信系统的性能严重下降的情况，开发新型通信系统。设计各种数字通信系统的基本假设是接收机能够估计无线电或声传播信道，并在检测过程中使用该估计。在具有大的多普勒和延迟扩展的随机快速时变信道中，可靠的信道估计是不可能的。这个项目考虑的问题是设计一个通信系统时，信道实现是未知的和不可估计的，只有信道的统计是已知的（或可以估计）。因此，信道实现仅已知位于其维度是信道协方差矩阵的秩的子空间中的某处。单位秩的情况下，减少这一类已知的通信问题。然而，秩大于1的情况需要对当前理论进行重大扩展。这个问题的制定导致新的接收机结构和设计通信系统，必须在恶劣的时变环境中工作的新方法。该项目正在为通过子空间信道进行通信开发最佳和次佳解决方案，并对其性能进行分析。 正在研究各种类型的通信系统，包括：通过频率选择性信道操作的单输入单输出系统、MIMO系统以及多用户和多址系统。