DocumentCode :
3126685
Title :
Joint optimization of the transmit covariance and the relay precoder in general Gaussian amplify-and-forward relay channels
Author :
Gohary, Ramy H. ; Yanikomeroglu, Halim
fYear :
2012
fDate :
1-6 July 2012
Firstpage :
418
Lastpage :
422
Abstract :
The capacity of the amplify-and-forward (AF) scheme in general full-duplex Gaussian relay channels is achieved by Gaussian codebooks and can be cast as the solution of an optimization problem of the input transmit covariance and the relay precoder. This problem is non-convex. To circumvent this difficulty, the Karush-Kuhn-Tucker (KKT) conditions are used to obtain closed form expressions of the optimal input covariance that corresponds to an arbitrary relay precoder. Using these expressions, it is shown the maximum rate of the AF scheme is achieved by subdiagonal precoders. This observation is used to facilitate the search for the optimal relay precoder, and to show that at high transmit powers, it is optimal for the relay to remain silent and, at low transmit powers, it is optimal to operate in a mode that resembles half-duplex operation.
Keywords :
Gaussian channels; amplify and forward communication; channel coding; concave programming; covariance matrices; precoding; AF scheme; Gaussian codebooks; KKT conditions; Karush-Kuhn-Tucker conditions; arbitrary relay precoder; general Gaussian amplify-and-forward relay channels; general full-duplex Gaussian relay channels; half-duplex operation; input transmit covariance; nonconvex problem; optimal input covariance; subdiagonal precoders; transmit covariance joint optimization; Covariance matrix; Eigenvalues and eigenfunctions; Joints; Matrix decomposition; Optimization; Relays; Vectors;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Information Theory Proceedings (ISIT), 2012 IEEE International Symposium on
Conference_Location :
Cambridge, MA
ISSN :
2157-8095
Print_ISBN :
978-1-4673-2580-6
Electronic_ISBN :
2157-8095
Type :
conf
DOI :
10.1109/ISIT.2012.6284221
Filename :
6284221
Link To Document :
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