基于叠加训练序列的时变信道估计及预编码信号分离策略研究

Due to the scarce spectrum resources and high mobile scenarios,the design of wireless communication systems faces more and more challenging. It is of critical importance to utilize the finite spectrum resources efficiently for modern mobile communications. The superimposed training(ST)-based transmission schemes have been attracted much attention without loss of training bandwidth. However, with the superimposed mode,the data-training interference severely deteriorates the performance of channel estimation and data detection.The key task is how to separate the superimposed signals and eliminate the mutual interference at the receiver.In an attempt to design the separable superimposed signals, three specific aspects are involved,such as the design of superimposed training scheme with precoding, optimization parameters for channel model and iterative received processing. First, a novel idea of precoding superimposed mode built from orthogonal polyphase sequences is proposed. Based on the theory of function space, the prior information of time-varying channel is extracted to enhance the estimation performance. Finally, the iterative received schemes are designed and their performance is assessed from the viewpoint of information theory. The new transmitted signal framework and separation theory for superimposed signals are strived to establish that would overcome the disadvantages of current other superimposed schemes.These findings would offer new guidelines and directions to other bandwidth-efficient transmission systems over time-varying fading channels.

随着无线频谱资源的日趋紧张和高移动环境的应用需求，无线通信系统设计面临越来越严峻的挑战，如何充分利用有限的频谱资源是现代移动通信必须解决的问题。基于叠加训练的传输方案由于消除了训练序列占用的频带开销而受到广泛关注。然而，采用叠加信号传输方式会带来训练序列与信息符号的相互干扰，直接导致信道估计和检测性能的恶化，如何分离叠加信号进而消除二者的相互干扰是提高系统性能的关键。本项目以叠加信号分离方案设计作为切入点，探究预编码叠加训练方案设计、时变信道模型优化和迭代接收等方面的问题。提出利用多相正交序列来设计预编码叠加信号的新思路；立足函数空间理论，充分挖掘信道先验信息来提高估计性能；最后，从信息论角度综合评价迭代估计与检测方案的性能。研究旨在建立新的发射信号框架和叠加信号分离理论，克服目前叠加训练方案存在的不足，同时为时变衰落信道下其它高效传输系统提供新思路和解决方案。

本项目针对高速移动环境下宽带无线通信等场景，以提高带宽利用率为目标，对叠加训练设计、预编码信号分离及高效时变信道估计技术展开研究。针对叠加训练方案存在的严重干扰，提出利用多相正交序列来设计仿射预编码叠加训练的新思路，并将预编码的正交设计思想扩展到OFDM系统的叠加导频设计中，提出秩亏预编码的干扰置零方案，并针对其造成的数据失真，采用星座旋转来改善符号检测性能。最后，将仿射预编码正交设计思路扩展到时频双选衰落信道估计中，针对CE-BEM和DPS-BEM优化模型，提出相应的正交训练设计和仿射预编码干扰抑制方案，并采用联合迭代估计和检测来提高系统性能，通过分析不同参数下TDM、FDM与叠加训练方案的性能进行评估，验证方案设计的有效性。此外，项目组还将叠加训练设计思想扩展到协作信道估计领域，提出带内叠加导频的单跳信道估计方案，部分研究还在整理和审稿中。综上所述，本研究成果将有效提高时变信道的带宽利用率，具有较好的扩展性，其设计思想已扩展到采用叠加训练的MIMO、协作中继等通信系统中。