Capacity and mutual information of wideband multipath fadingchannels
Telatar, I.E.
Tse, D.N.C.
Lucent Technol. Bell Labs., Murray Hill, NJ;
This paper appears in: Information Theory, IEEE Transactions on
Publication Date: Jul 2000
Volume: 46,
Issue: 4
On page(s): 1384-1400
ISSN: 0018-9448
References Cited: 14
CODEN: IETTAW
INSPEC Accession Number: 6660214
Digital Object Identifier: 10.1109/18.850678
Current Version Published: 2002-08-06
Abstract
We investigate the capacity and mutual information of a broadband
fading channel consisting of a finite number of time-varying paths. We
show that the capacity of the channel in the wideband limit is the same
as that of a wideband Gaussian channel with the same average received
power. However, the input signals needed to achieve the capacity must be
“peaky” in time or frequency. In particular, we show that if
white-like signals are used instead (as is common in spread-spectrum
systems), the mutual information is inversely proportional to the number
of resolvable paths L˜ with energy spread out, and in fact
approaches 0 as the number of paths gets large. This is true even when
the paths are assumed to be tracked perfectly at the receiver. A
critical parameter L˜crit is defined in terms of system
parameters to delineate the threshold on L over which such overspreading
phenomenon occurs
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