Joint Source-Channel Coding for Wireless Networks

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

0729210 - Joint Source-Channel Coding for Wireless Networks Currently, 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 to changes 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.