Multi-User Communications in Non-Gaussian Channels

本项目将研究通过扩频调制通过非高斯信道进行多址通信的问题。这在很大程度上是因为现代城市无线电网络必须在复杂多变的噪声环境中运行，而这些环境往往由脉冲、非高斯、人为和自然噪声源主导。目前已知，非高斯干扰存在于许多情况下，它们会极大地降低传统数字通信系统的性能。这项研究的总体目的是开发适用于工作在这种非高斯信道中的多用户系统的新的设计方法。这项研究可以分为两个主要任务来考虑。其中包括时间和相位同步器的发展，以及在非高斯噪声中“最佳”的非线性、相干、扩频接收机的设计。在许多应用中，在非高斯噪声源存在的情况下，噪声的脉冲和暂态特性表明，接收机结构中的非线性可以通过减小噪声脉冲引起的大电压偏差来显著降低有效噪声功率。因此，提出了设计和分析最优无记忆非线性同步和相关接收的性能。还将探索在接收器的结构中引入记忆的可能性。预计这项研究成果将在城市和军事移动无线电网络和低频通信中得到广泛应用。

This project will investigate the problem of multiple-access communications through non-Gaussian channels via spread-spectrum modulation. It is motivated in large part by the fact that modern urban radio networks must operate in complex and variable noise environments that are often dominated by impulsive, non- Gaussian man-made and natural noise sources. Non-Gaussian disturbances are now known to be present in many situations, and they can greatly reduce the performance of conventional digital communication systems. The overall purpose of this research is to develop new design methods suitable for multiuser systems operating in such non-Gaussian channels. The study can be divided into two principal tasks to be considered. There are the development of time and phase synchronizers; and the design of "optimum" nonlinear, coherent, spread-spectrum receivers in non-Gaussian noise. In many applications, in the presence of non-Gaussian noise sources, the impulsive and transient characterisitics of noise suggest that a nonlinearity in the receiver structure can significantly reduce the effective noise power by reducing the large voltage deviation caused by noise impulses. Thus it is proposed to design and analyze the performance of optimum memoryless nonlinearities for synchronization and correlation reception. Possibilities of introducing memory in the structure of receivers will also be explored. It is anticipated that the results of this study will find widespread application in urban and military mobile radio networking and low frequency communications.