Source and Physical-Layer Network Coding for Correlated Two-Way Relaying

In this paper, we study a half-duplex two-way relay channel (TWRC) with correlated sources exchanging bidirectional information. In the case, when both sources have the knowledge of correlation statistics, a source compression with physical-layer network coding (SCPNC) scheme is proposed to perform the distributed compression at each source node. When only the relay has the knowledge of correlation statistics, we propose a relay compression with physical-layer network coding (RCPNC) scheme to compress the bidirectional messages at the relay. The closed-form block error rate (BLER) expressions of both schemes are derived and verified through simulations. It is shown that the proposed schemes achieve considerable improvements in both error performance and throughput compared with the conventional non-compression scheme in correlated two-way relay networks (CTWRNs).Comment: 15 pages, 6 figures. IET Communications, 201

Real-Time Adaptive Video Compression

Compressive sensing has been widely applied to problems in signal and imaging processing. In this work, we present an algorithm for predicting optimal real-time compression rates for video. The video data we consider is spatially compressed during the acquisition process, unlike in many of the standard methods. Rather than temporally compressing the frames at a fixed rate, our algorithm adaptively predicts the compression rate given the behavior of a few previous compressed frames. The algorithm uses polynomial fitting and simple filters, making it computationally feasible and easy to implement in hardware. Based on numerical simulations of real videos, the algorithm is able to capture object motion and approximate dynamics within the compressed frames. The adaptive video compression improves the quality of the reconstructed video (as compared to an equivalent fixed rate compression scheme) by several dB of peak signal-to-noise ratio without increasing the amount of information stored, as seen in numerical simulations presented here

Ein Beitrag zur Pixel-basierten Verteilten Videocodierung: Seiteninformationsgenerierung, WZ-Codierung und flexible Decodierung

Moderne Anwendungsszenarien, wie die individuelle Übertragung von Videodaten zwischen mobilen Endgeräten, stellen neue Herausforderungen an das Videoübertragungssystem. Hierbei liegt ein besonderer Fokus auf der geringen Komplexität des Videoencoders. Diese Anforderung kann mit Hilfe der Verteilten Videocodierung erfüllt werden. Im Fokus der vorliegenden Arbeit liegen die sehr geringe Encoderkomplexität sowie auch die Steigerung der Leistungsfähigkeit und die Verbesserung der Flexibilität des Decodierungsprozesses. Einer der wesentlichen Beiträge der Arbeit bezieht sich auf die Verbesserung der Seiteninformationsqualität durch temporale Interpolation

Backward channel aware distributed video coding

Digital image and video coding has witnessed rapid development in the past decades. Conventional hybrid motion-compensated-prediction (MCP) based video coding exploits both spatial and temporal redundancy at the encoder. Hence the encoder requires much more computational resources than the decoder. This poses a challenge for applications such as video surveillance systems and wireless sensor networks. Only limited memory and power are available at the encoder for these applications, while the decoder has access to more powerful computational resources. The Slepian-Wolf theorem and Wyner-Ziv theorem have proved that a distributed video coding scheme is achievable where sources are encoded separately and decoded jointly. The basic goal of our research is to analyze the performance of the low complexity video encoding theoretically, and to design new practical techniques to achieve a high video coding efficiency while maintaining low encoding complexity. In this thesis, we propose a new backward channel aware Wyner-Ziv approach. The basic idea is to use backward channel aware motion estimation to code the key frames in Wyner-Ziv video coding, where motion estimation is done at the decoder and motion vectors are sent back to the encoder. We refer to these backward predictive coded frames as BP frames. A mode decision scheme through the feedback channel is studied. Compared to Wyner-Ziv video coding with INTRA coded key frames, our approach can significantly improve the coding efficiency. We further consider the scenario when there are transmission errors and delays over the backward channel. A hybrid scheme with selective coding is proposed to address the problem. Our results show that the coding performance can be improved by sending more motion vectors to the encoder. However, there is a tradeoff between complexity and rate-distortion performance in backward channel aware Wyner-Ziv video coding. We present a model to quantitatively analyze the complexity and rate-distortion tradeoff for BP frames. Three estimators, the minimum estimator, the median estimator and the average estimator, are proposed and the complexity-rate-distortion analysis is presented