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The Scientific World Journal
Volume 2013 (2013), Article ID 370261, 11 pages
Research Article

Suboptimal Greedy Power Allocation Schemes for Discrete Bit Loading

1Electronics and Communication Engineering Department, Faculty of Electronic Engineering, Menoufia University, Menouf 32952, Egypt
2Centre for White Space Communications/CeSIP, Department of EEE, University of Strathclyde, Glasgow G1 1XW, Scotland, UK

Received 7 August 2013; Accepted 12 October 2013

Academic Editors: N. Bouguila and G. L. Foresti

Copyright © 2013 Waleed Al-Hanafy and Stephan Weiss. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We consider low cost discrete bit loading based on greedy power allocation (GPA) under the constraints of total transmit power budget, target BER, and maximum permissible QAM modulation order. Compared to the standard GPA, which is optimal in terms of maximising the data throughput, three suboptimal schemes are proposed, which perform GPA on subsets of subchannels only. These subsets are created by considering the minimum SNR boundaries of QAM levels for a given target BER. We demonstrate how these schemes can significantly reduce the computational complexity required for power allocation, particularly in the case of a large number of subchannels. Two of the proposed algorithms can achieve near optimal performance including a transfer of residual power between subsets at the expense of a very small extra cost. By simulations, we show that the two near optimal schemes, while greatly reducing complexity, perform best in two separate and distinct SNR regions.