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SUMMARY:A Simple Proof of Threshold Saturation for Coupled Scalar Recursio
 ns
DTSTART:20120607T111500
DTEND:20120607T121500
DTSTAMP:20260509T103453Z
UID:93d7fccc01b4d1bf47f037e39588aa05274e1eb3659e611bd339cbd1
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Henry Pfister\nAbstract:\nIt is well-known that belief-p
 ropagation (BP) decoding of low-density parity-check (LDPC) codes is subop
 timal and that the noise threshold of maximum-a-posteriori (MAP) decoding 
 can be larger than the BP threshold.  Recently\, Kudekar et al. showed th
 at regular LDPC ensembles can be "spatially coupled" so that their BP nois
 e threshold saturates to the MAP noise threshold of the original ensemble.
   These new ensembles are actually LDPC convolutional (LDPCC) codes and t
 he new result explains an earlier observation by Lentmaier et al. that ter
 minated LDPCC codes allow reliable communication at rates very close to ca
 pacity.\nFrom a statistical physics point of view\, LDPC codes can be asso
 ciated with a collection of electrons whose spins are coupled.  Above the
  MAP threshold\, this system behaves like a liquid.  Below the BP thresho
 ld\, this system spontaneously crystallizes into the minimum-energy config
 uration.  If the noise level is between the BP threshold and the MAP thre
 shold\, the system behaves like a super-cooled liquid: the system remains 
 a liquid unless there is a seed crystal to start the crystal growth.  Spa
 tial coupling alters the ensemble to include a seed crystal and allows the
  information to crystallize when the noise is below the MAP threshold.\nTh
 is talk presents a simple proof of threshold saturation that applies to a 
 broad class of coupled scalar recursions.  In particular\, it applies to 
 the density-evolution (DE) equations of irregular LDPC codes on the erasur
 e channel and the joint iterative decoding of LDPC codes on intersymbol-in
 terference channels with erasure noise.  Extensions to coupled vector rec
 ursions will also be discussed along with their connection to universality
  in multiuser scenarios.
LOCATION:BC 01 https://plan.epfl.ch/?room==BC%2001
STATUS:CONFIRMED
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