160 likes | 276 Views
Hybrid Codes and the Point-to-Point Channel. Paul Cuff Curt Schieler. Source-Channel Coding. p( y|x ). f. g. Correlation between S and Ŝ:. Achieved with separately designed encoder and decoder. Video Transmission (example). p( y|x ). f. Systematic Transmission (example). Relay.
E N D
Hybrid Codes and thePoint-to-Point Channel Paul Cuff Curt Schieler
Source-Channel Coding p(y|x) f g Correlation between S and Ŝ: Achieved with separately designed encoder and decoder.
Video Transmission (example) p(y|x) f
Systematic Transmission (example) Relay Transmission Transmission Analog Digital Hybrid
Copy-Robust Documents (example) A document gets printed with redundancy . Photocopy noise removed by photocopier.
Connection to General Point-to-Point Channel Setting p(y|x) f g
Digital Watermark (example) • Media is modified to include extra information • Scoundrel may try to delete the watermark • Channel input (X) is modified media • Ŝ is additional information (digital tag)
Define Empirical Coordination p(y|x) f g Empirical distribution: is achievable if:
Separation Method Channel Index Achieves product distributions: such that
A Better Idea (Hybrid Codes) Channel
Hybrid Codes • Digital • Source is compressed and coded in blocks • Analog • Channel input and reconstruction depend letter-by-letter on the source and channel output • Hybrid Codes take advantage of correlation in network setting (i.e. interference channel) • [Minero, Lim, Kim – Allerton 2010, ISIT 2011]
Achievable Inner Bound is achievable if Source Channel Markov Chain Function (analog encoding) Function( analog decoding) Digital Decoding
Binary Example • Source is Bern(p) • Binary symmetric channel (Ɛ) • Require reconstruction to equal channel input • i.e. X = Ŝ (systematic transmission) • Minimize Hamming distortion If p= .5: D = Ɛ (Optimal) If p>0 and Ɛ>0 : D > 0 (Suboptimal)
State Amplification p(y|x,s) f g • Channel State is known to the encoder • Two objectives • Transmit a message • Help decoder estimate state No loss of generality [Kim, Sutivong, Cover – ‘08] [Choudhuri, Kim, Mitra– ‘10, ‘11]
Causal Achievable Region is achievable iff Source Channel Markov Chain Function (analog encoding) Function( analog decoding) Digital Decoding
Strictly-Causal Achievable Region is achievable iff Source Channel Markov Chain Function (analog encoding) Function( analog decoding) Digital Decoding