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A bstruct- A coding technique is described which improves error performance
of synchronous data links without sacrificing data rate or requiring
more bandwidth. This is achieved by channel coding with expanded sets of
multilevel/phase signals in a manner which increases free Euclidean distance.
Soft maximum-likelihood (ML) decoding using the Viterbi algorithm
is assumed. Following a discussion of channel capacity, simple
hand-designed trellis codes are presented for 8 phase-shift keying (PSK)
and 16 quadrature amplitude-shift keying (QASK) modulation. These
simple codes achieve coding gains in the order of 3-4 dB. It is then shown
that the codes can be interpreted as binary convolutional codes with a
mapping of coded bits into channel signals, which we call “mapping by set
partitioning.” Based on a new distance measure between binary code
sequences which efficiently lower-bounds the Euclidean distance between
Manuscript received May 24, 1977; revised January 7, 1981.
the corresponding channel signal sequences, a search procedure for more
powerful codes is developed. Codes with coding gains up to 6 dB are
obtained for a variety of multilevel/phase modulation schemes. Simulation
results are presented and an example of carrier-phase tracking is discussed. |
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发表于 2008-3-6 23:06:07
