Analog joint source channel coding for multi terminal and non-linear channels

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University of Delaware
This dissertation discusses various problems in analog Joint Source Channel Coding (JSCC). Analog JSCC is an attractive communication scheme due to its encoding/decoding simplicity, and its ability to achieve near-optimal performance using very short code lengths. JSCC systems have received a renewed interest in recent years due to, among other factors, the sub-optimality of separation based schemes in many situations in multi-terminal communications. Different from traditional digital communication systems which utilize a quantizer followed by a source code and a channel code, analog JSCC systems combine source and channel coding into a single block and deal with real numbers. ☐ We present original work on the application of space filling curves, a common scheme in analog coding, to different communication scenarios. We begin by examining how to extend the use of space filling curves to non-linear channels with Inter-Symbol Interference (ISI). This type of channel arises when considering acoustic communications in the underwater environment, where the power amplifier used for communication is highly non-linear, and multi-path propagation causes ISI. We first study a simplified version of the acoustic channel assuming a frequency flat (no ISI) response, developing a scheme to adapt space filling curves to the simplified channel and studying its theoretical limits. Then, we extend our work to the complete end-to-end acoustic channel (including ISI), presenting a communication system for the end-to-end channel. ☐ We then investigate the problem of transmitting independent sources over the Gaussian Multiple Access Channel (MAC). The Gaussian MAC consists of two or more users communicating information to a central receiver over a shared noisy physical channel. We introduce an analog CDMA-like access scheme that allows users to transmit at different rates over the MAC. The developed access scheme is suitable for the transmission of analog JSCC encoded sources. The CDMA-like access scheme will be proven to be optimal for a particular case when the channel degrees of freedom are assigned amongst the users in a particular way. We will then present a hybrid analog-digital scheme which is an extension of the analog CDMA-like access scheme. The hybrid scheme uses analog and digital codes, designed for the point-to-point channel, and will be proven to be optimal for the entire region of the MAC. ☐ Finally, the dissertation introduces a new communication scheme for the two-user Gaussian Broadcast channel. The channel consists of a common transmitter wishing to communicate information to two receivers over a noisy Gaussian channel. The broadcast channel is an interesting case, since in general separation based schemes cannot achieve the theoretical limits. The new developed scheme is a variant of Scalar Quantizer Linear Coder (SQLC) systems, and is suitable for transmitting correlated Bivariate Gaussian sources. The scheme will be analyzed and shown to outperform the best known separation based schemes.
Communication and the arts, Applied sciences, Broadcast channels, Joint source channel coding, Nested quantization, Network information theory, Space filling curves