On Thu, Jan 20, 2011 at 01:36:46PM -0700, Ben Reynwar wrote: > > You've got that right: a soft decider doesn't really decide, but rather > > gives a value how good the estimate is. Say you have a binary output, > > 1 and -1. A soft decider can also give any value in between. If you get > > a 0, then the soft decider really has no clue what was actually > > transmitted and instead of guessing a binary value, it relays this > > uncertainty. > > One place this is really important is the channel decoding. > > > > That makes sense. What kind of values would you output when you have more > than 2 symbols? Would you just give the distances to the closest n points?
Good question--but it also depends on where you need the soft values. Say you have a 4-QAM and a binary channel code. Then you'd split every symbol in two soft values, one for each bit. In this case, assuming phase was corrected, the real and imaginary values. Cheers, MB -- Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin Braun Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT -- University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association
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