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Joint noncoherent demodulation and decoding for the block fading
channel: A practical framework for approaching Shannon capacity
Written by:
Rong-Rong Chen,
Ralf Koetter,
Upamanyu Madhow,
and
Dakshi Agrawal.
Citation:
IEEE Transaction on Communications, 51:1676-1689, October 2003.
Copyright © (2003) by IEEE. Permission to make digital or
hard copies of part or all of this work for personal or classroom use
is granted without fee provided that copies are not made or distributed
for profit. To copy otherwise, to republish, to post on servers, or to
redistribute to lists, requires prior specific permission and/or a fee.
Abstract:
The paper contains a systematic investigation of practical coding
strategies for noncoherent communication over fading channels, guided
by explicit comparisons with information-theoretic benchmarks.
Noncoherent reception is interpreted as joint data and channel
estimation, assuming that the channel is time varying and a priori
unknown. We consider iterative decoding for a serial concatenation of
a standard binary outer channel code with an inner modulation code
amenable to noncoherent detection. For an information rate of about
1/2 bit per channel use, the proposed scheme, using a quaternary
phase-shift keying (QPSK) alphabet, provides performance within
1.6-1.7 dB of Shannon capacity for the block fading channel, and is
about 2.5-3 dB superior to standard differential demodulation in
conjunction with an outer channel code. We also provide capacity
computations for noncoherent communication using standard phase-shift
keying (PSK) and quadrature amplitude modulation (QAM) alphabets;
comparing these with the capacity with unconstrained input provides
guidance as to the choice of constellation as a function of the
signal-to-noise ratio. These results imply that QPSK suffices to
approach the unconstrained capacity for the relatively low information
and fading rates considered in our performance evaluations, but that
QAM is superior to PSK for higher information or fading rates,
motivating further research into efficient noncoherent coded
modulation with QAM alphabets.
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