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Fading relay channels: Performance limits and space-time signal design
Authors
Rohit U. Nabar, Helmut Bölcskei, and Felix W. KneubühlerReference
IEEE Journal on Selected Areas in Communications, Vol. 22, No. 6, pp. 1099-1109, Aug. 2004
DOI: 10.1109/JSAC.2004.830922
[BibTeX, LaTeX, and HTML Reference] Abstract
Cooperative diversity is a transmission technique where
multiple terminals pool their resources to form a virtual antenna array that
realizes spatial diversity gain in a distributed fashion. In this paper,
we examine the basic building block of cooperative diversity systems,
a simple fading relay channel where the source, destination and
relay terminals are each equipped with single antenna transceivers. We consider
three different TDMA-based cooperative protocols that vary the degree
of broadcasting and receive collision. The relay terminal operates in either
the amplify-and-forward (AF) or decode-and-forward (DF) modes.
For each protocol, we study the ergodic and outage capacity behavior (assuming Gaussian code books) under the AF and DF modes of relaying. We analyze the
spatial diversity performance of the various protocols and find that full
spatial diversity (second-order in this case) is achieved by certain
protocols provided that appropriate power control is employed.
Our analysis
unifies previous results reported in the literature and establishes the
superiority (both from a capacity as well as a diversity point-of-view) of
a new protocol proposed in this paper.
The second part of the paper is devoted to (distributed) space-time code design
for fading relay channels operating
in the AF mode.
We show that the corresponding code design criteria
consist of the traditional rank and determinant criteria for the case
of co-located antennas
as well as
appropriate power control rules.
Consequently space-time codes designed for the case of
co-located multi-antenna channels can be used to realize cooperative diversity
provided that appropriate power control is employed.Keywords
Relay channels, fading, cooperative diversity, protocols, capacity, nonorthogonal amplify-and-forward
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