68 research outputs found
Iterative Quantization Using Codes On Graphs
We study codes on graphs combined with an iterative message passing algorithm
for quantization. Specifically, we consider the binary erasure quantization
(BEQ) problem which is the dual of the binary erasure channel (BEC) coding
problem. We show that duals of capacity achieving codes for the BEC yield codes
which approach the minimum possible rate for the BEQ. In contrast, low density
parity check codes cannot achieve the minimum rate unless their density grows
at least logarithmically with block length. Furthermore, we show that duals of
efficient iterative decoding algorithms for the BEC yield efficient encoding
algorithms for the BEQ. Hence our results suggest that graphical models may
yield near optimal codes in source coding as well as in channel coding and that
duality plays a key role in such constructions.Comment: 10 page
Source Coding with Fixed Lag Side Information
We consider source coding with fixed lag side information at the decoder. We
focus on the special case of perfect side information with unit lag
corresponding to source coding with feedforward (the dual of channel coding
with feedback) introduced by Pradhan. We use this duality to develop a linear
complexity algorithm which achieves the rate-distortion bound for any
memoryless finite alphabet source and distortion measure.Comment: 10 pages, 3 figure
Authentication with Distortion Criteria
In a variety of applications, there is a need to authenticate content that
has experienced legitimate editing in addition to potential tampering attacks.
We develop one formulation of this problem based on a strict notion of
security, and characterize and interpret the associated information-theoretic
performance limits. The results can be viewed as a natural generalization of
classical approaches to traditional authentication. Additional insights into
the structure of such systems and their behavior are obtained by further
specializing the results to Bernoulli and Gaussian cases. The associated
systems are shown to be substantially better in terms of performance and/or
security than commonly advocated approaches based on data hiding and digital
watermarking. Finally, the formulation is extended to obtain efficient layered
authentication system constructions.Comment: 22 pages, 10 figure
Rate-splitting for the deterministic broadcast channel
We show that the deterministic broadcast channel, where a single source transmits to M receivers across a deterministic mechanism, may be reduced, via a rate-splitting transformation, to another (2M−1)-receiver deterministic broadcast channel problem where a successive encoding approach suffices. Analogous to rate-splitting for the multiple access channel and source-splitting for the Slepian-Wolf problem, all achievable rates (including non-vertices) apply. This amounts to significant complexity reduction at the encoder
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