Joint Source-Channel Coding Based on Cosine-Modulated Filter Banks for Erasure-Resilient Signal Transmission
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Joint Source-Channel Coding Based on Cosine-Modulated Filter Banks for Erasure-Resilient Signal Transmission Slavica Marinkovic IRISA-INRIA, Campus Universitaire de Beaulieu, 35042 Rennes Cedex, France Email: [email protected]
Christine Guillemot IRISA-INRIA, Campus Universitaire de Beaulieu, 35042 Rennes Cedex, France Email: [email protected] Received 2 April 2004; Revised 18 August 2004; Recommended for Publication by Helmut Boelcskei This paper examines erasure resilience of oversampled filter bank (OFB) codes, focusing on two families of codes based on cosinemodulated filter banks (CMFB). We first revisit OFBs in light of filter bank and frame theory. The analogy with channel codes is then shown. In particular, for paraunitary filter banks, we show that the signal reconstruction methods derived from the filter bank theory and from coding theory are equivalent, even in the presence of quantization noise. We further discuss frame properties of the considered OFB structures. Perfect reconstruction (PR) for the CMFB-based OFBs with erasures is proven for the case of erasure patterns for which PR depends only on the general structure of the code and not on the prototype filters. For some of these erasure patterns, the expression of the mean-square reconstruction error is also independent of the filter coefficients. It can be expressed in terms of the number of erasures, and of parameters such as the number of channels and the oversampling ratio. The various structures are compared by simulation for the example of an image transmission system. Keywords and phrases: frames, filter banks, source coding, channel coding, erasure channels, Internet communication.
1.
INTRODUCTION
The advent of multimedia communication over packetswitched (IP) networks is creating challenging problems in the area of coding. Due to the real-time nature of data streams, multimedia delivery usually makes use of unresponsive transport protocols, that is, User Datagram Protocol (UDP) and/or Real-Time Transport Protocol (RTP) [1]. In contrast with Transport Control Protocol (TCP), these protocols offer no control mechanism that would guarantee a level of QoS. The packets may be sent via different routes and may arrive at destination with a large delay or not arrive at all. Traditional approaches to fight against erasures consist in sending redundant information along with the original information so that the lost data (or at least part of it) can be recovered from the redundant information. The design principles that have prevailed so far stem from Shannon’s source and channel separation theorem which states that the source and channel optimum performance bounds can be approached as closely as desired by independently designing the source and channel coding strategies. However, this holds only under asymptotic conditions where both codes
are allowed infinite length and complexity. If the design of the system is heavily constrained in terms of complexity or delay, the separate (also called tandem) approach can be largely subopt
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