Joint Source-Channel Coding for Wireless Networks

0729210-无线网络的信源-信道联合编码目前，对通过无线网络可靠、高质量地访问多媒体内容有很大的需求。这种需求源于社会对无处不在的多媒体的日益增长的需求，无论是关键的医疗信息(X光、实时患者视频)、新闻还是娱乐。通过无线网络提供这种服务是具有挑战性的，因为无线信道受到一种称为衰落的现象的影响，由于这种现象导致从发射器到接收器的瞬时链路质量随着时间、频率和位置而变化。链路质量在发送器处通常是未知的，因此需要使用对链路质量的变化具有健壮性的传输方案。本研究涉及在发射机未知瞬时链路质量的情况下，设计和分析用于在衰落无线信道上传输诸如多媒体信号的模拟信号的有效编码方案。特别强调了有效地向具有不同链路质量的多个用户广播信号的技术，以及允许接收器处的重建质量随链路质量优雅缩放的技术。本研究集中于针对广播信道和非遍历无线信道的联合信源-信道编码方案的设计和分析。研究中解决的具体问题包括：(I)设计了几种新的基于分层传输的联合信源信道编码方案，包括叠加编码、有无边信息的混合数字-模拟编码以及匹配串接编码的使用。这种码被设计用于多输入多输出信道、单输入单输出高斯和擦除广播信道、以及存在发射机已知和接收机未知干扰的单输入单输出广播信道。(Ii)开发工具，以了解这些计划的潜力和基本限制，并确定在分析上容易掌握和有洞察力的适当指标。(3)构造实际可实现的联合信源-信道码。当与实际的编码/译码算法一起使用时，而不是在假设的最大似然译码下，特别注意构造中等长度的单个码，其同时是好的信源码和好的信道码。

0729210 - Joint Source-Channel Coding for Wireless NetworksCurrently, there is a significant demand for reliable, high-quality access to multimedia content over wireless networks. This demand stems from society's growing desire for ubiquitous access to multimedia, whether it be critical medical information (x-rays, real-time patient video), news, or entertainment.Providing such services over wireless networks is challenging because wireless channels are subject to a phenomenon known as fading, due to which the instantaneous link quality from the transmitter to the receiver varies with time, frequency and location. The link quality is often not known at the transmitter, necessitating the use of transmission schemes that are robust tochanges in the link quality. This research involves the design and analysis of efficient encoding schemes for transmission of analog signals such as multimedia signals over fading wireless channels, when the instantaneous link quality is not known at the transmitter. Particular emphasis is placed on techniques which are efficient for broadcasting signals to many users with different link qualities and techniques that allow the reconstruction quality at the receiver to scale gracefully with the link quality.This research focusses on the design and analysis of joint source-channel coding schemes for broadcast channels and non-ergodic wireless channels. Specific problems addressed in the research include - (i) the design of several novel joint source-channel coding schemes based on layered transmission with superposition coding, hybrid digital-analog coding with and without side information and the use of matched tandem-encoding. Such codes are designed for multiple-input multiple-output channels, single-input single-output Gaussian and erasure broadcast channels, and a single-input single-output broadcast channel in the presence of an interference known to the transmitter and unknown to the receiver. (ii) development of tools to understand the potentials and fundamental limits of these schemes, and in the definition of appropriate metrics that are analytically tractable as well as insightful. (iii) construction of practically realizable joint source-channel codes. Particular attention is given to the construction of a single code of moderate length that is simultaneously a good source code and a good channel code when used with practical encoding/decoding algorithms, instead of under hypothetical maximum-likelihood decoding.