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SUMMARY:Joint LDPC Decoding and Timing Recovery Using Code Constraint Feed
 back - Christopher Jones
DTSTART:20060526T130000Z
DTEND:20060526T140000Z
UID:TALK5035@talks.cam.ac.uk
CONTACT:David MacKay
DESCRIPTION:In traditional receiver architectures\, symbol acquisition and
 \ntracking are performed using phase lock techniques that are\nindependent
  of the channel code decoding process. In burst\nreception scenarios\, ban
 dwidth inefficient piloting must often\nbe embedded in a transmission in o
 rder to accelerate acquisition\nand or to aid symbol time tracking at low 
 signal-to-noise ratios.\nIn this paper we show that outputs from the const
 raint node side\nof a bi-partite decoding graph can be used to direct esti
 mation\nof symbol frequency and phase in a pilotless Low-Density\nParity-C
 heck (LDPC) coded transmission.  We focus on the\nproblem of a fixed symbo
 l frequency/phase offset between transmitter\nand receiver and demonstrate
  that the technique is capable of\npulling-in arbitrarily large frequency 
 offsets with complexity that grows\nlogarithmically with offset size. Rela
 tively large timing offsets may\noccur in receivers that need to determine
  baud rates autonomously\nwhile finer offsets are often due to crystal osc
 illator mismatches\nand Doppler-induced frequency shifts.  Combining the c
 onstraint node\nobservations with a properly calibrated PLL allows success
 ful\ntracking of both a fixed frequency offset and a random phase walk.\n\
 n\nAbout the Speaker\n\n\n\nChristopher R. Jones is with the Jet Propulsio
 n Laboratory in Pasadena\nCalifornia where he works on problems related to
  Low-Density Parity-Check\n(LDPC)\ncodes. Specific interests include proto
 graph selection and lifting to achieve\nlow error-floors\, universal encod
 er/decoder architectures\, hybridization\nwith ARQ\nprotocols\, and integr
 ation with timing / carrier recovery techniques. Chris'\nbackground includ
 es a Ph.D.in Electrical Engineeing from the University of\nCalifornia Los 
 Angeles and five years as a communications engineer with\nBroadcom\nCorpor
 ation.\n\n
LOCATION:Ryle Seminar Room\, Cavendish Laboratory
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