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Optimum Power Allocation for OFDM Based Cognitive Radio Systems With Arbitrary Input Distributions

Sohail, A, Al-Imari, M, Xiao, P and Evans, B (2013) Optimum Power Allocation for OFDM Based Cognitive Radio Systems With Arbitrary Input Distributions In: IEEE 77th Vehicular Technology Conference (VTC), 2013-06-02 - ?, Dresden, Germany.

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In the literature, optimal power assuming Gaussian input has been evaluated in OFDM based Cognitive Radio (CR) systems to maximize the capacity of the secondary user while keeping the interference introduced to the primary user band within tolerable range. However, the Gaussian input assumption is not practical and Finite Symbol Alphabet (FSA) input distributions, i.e., M-QAM are used in practical systems. In this paper, we consider the power optimization problem under the condition of FSA inputs as used in practical systems, and derive an optimal power allocation strategy by capitalizing on the relationship between mutual information and minimum mean square error. The proposed scheme is shown to save transmit power in a CR system compared to its conventional counterpart, that assumes Gaussian input. In addition to extra allocated power, i.e., power wastage, the conventional power allocation scheme also causes nulling of more subcarriers, leading to reduced transmission rate, compared to the proposed scheme. The proposed optimal power algorithm is evaluated and compared with the conventional algorithm assuming Gaussian input through simulations. Numerical results reveal that for interference threshold values ranging between 1 mW to 3 mW, the transmit power saving with the proposed algorithm is in the range between 55-75%, 42-62% and 12-28% whereas the rate gain is in the range between 16.8-12.4%, 13-11.8% and 3-5.8% for BPSK, QPSK and 16-QAM inputs, respectively.

Item Type: Conference or Workshop Item (Conference Paper)
Divisions : Faculty of Engineering and Physical Sciences > Electronic Engineering > Centre for Communication Systems Research
Authors : Sohail, A, Al-Imari, M, Xiao, P and Evans, B
Date : 2013
DOI : 10.1109/VTCSpring.2013.6692683
Contributors :
Additional Information : © 2013 IEEE. This is the author's version of a paper accepted for presentation at the IEEE 77th Vehicular Technology Conference. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Depositing User : Symplectic Elements
Date Deposited : 04 Oct 2013 13:49
Last Modified : 06 Jul 2019 05:13

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