New Directions in Signal Processing for Digital Communications

在通信信道上的信息传输通常涉及特性未知的信道。因此，该信息被未知的信道失真，该未知的信道还向消息添加随机噪声。如果信道特性是已知的，那么失真的非随机部分通常可以在接收器处被补偿，而问题是检测隐藏在噪声中的消息。如果信道特性未知，那么关键的一步是首先估计信道。在某些条件下，确实可以从接收到的数据本身进行这种估计。这种被称为信道盲识别的方法在过去已经被研究过了。研究人员研究了基于信道的频域信息进行这种识别的新方法。近年来，冗余滤波器组预编码器的巨大威力已经被确立。预编码器不仅允许在接收端使用有限持续时间的滤波器消除已知信道引入的线性失真，而且还允许在没有训练序列和不需要四阶统计量的情况下识别未知信道。研究了基于滤波器组预编码器的盲辨识和信道均衡的几种新方法。其中之一是直接在频域中进行盲信道辨识。这为计算提供了极大的简单性。这项研究还试图探索发射机和接收机之间的复杂性权衡。在过去，预编码者强调零填充系统的低发射机复杂度。研究人员将零点干扰作为一种替代方案进行研究。这项研究还解决了在设计抗通道零点的系统时出现的一些重要问题。

The transmission of information over a communication channel often involves channels whose characteristics are unknown. The information is therefore distorted by an unknown channel which in addition adds random noise to the message. If the channel characteristics are known, then the non random part of the distortion can usually be compensated at the receiver, and the problem is one of detecting the messages buried in noise. If the channel characteristics are unknown, then a crucial step is to estimate the channel first. Under certain conditions it is indeed possible to do this estimation from the received data itself. This approach, called blind identification of channels, has been studied in the past. The investigator studies new methods for such identification based on frequency domain information of the channel. In recent years the tremendous power of redundant filter bank precoders has been established. Precoders not only allow linear distortions introduced by known channels to be cancelled with finite duration filters at the receiver, they also allow the identification of unknown channels without training sequences and without the need for fourth order statistics. The research studies several new methods for blind identification and channel equalization based on filter bank precoders. One of these is blind channel identification directly in the frequency domain. This offers tremendous simplicity in computations. The research also seeks to explore tradeoff of complexity between transmitters and receivers. In the past, precoders have emphasized low transmitter complexity of zero-padded systems. The investigators study zero-jamming at the receiver as an alternative. The research also addresses a number of important issues which arise in the context of designing systems that are resistant to channel nulls.