naa a22 4500 51079503X CHVBK 20180411083333.0 cr unu---uuuuu 180411e20130401xx s 000 0 eng 10.1007/s11277-012-0626-2 doi (NATIONALLICENCE)springer-10.1007/s11277-012-0626-2 Power Allocation Schemes in OFDM-Based Femtocell Networks [Elektronische Daten] [Wei-Chen Pao, Yung-Fang Chen, Chia-Yen Chan] Orthogonal frequency division multiplex-based femtocell networks in downlink with two-tier interference are considered in this paper. In order to satisfy the quality of service of macrocell users, a capacity maximization problem with the total and the upper power constraints by allocating power to subcarriers for a user in femtocell systems becomes important. In this paper, the optimal power allocation is derived by using the Lagrangian technique. Based on the analysis of the Karush-Kuhn-Tucker conditions, subcarriers can be classified into two sets with different power allocation strategies according to the upper power constraint. One set of subcarriers is allocated with upper power, and the other set of subcarriers is processed by using the waterfilling approach. A direct linear search scheme is presented to achieve the optimal performance by finding the threshold over the channel states of all subcarriers to determine the two sets. In order to reduce the computational load, a reduced complexity scheme is designed for the optimal solution by utilizing the relationship of the allocated power in the two sets of subcarriers. Unlike the schemes in iterative manners, a fast power allocation scheme with a near-optimal performance is also developed. Simulation results reveal that the proposed schemes outperform the existing scheme. The efficacy of the proposed schemes is demonstrated in the simulations. Springer Science+Business Media, LLC., 2012 Orthogonal frequency division multiplex (OFDM) nationallicence Femtocell nationallicence Power allocation nationallicence Pao Wei-Chen Information and Communications Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, ROC aut Chen Yung-Fang Department of Communication Engineering, National Central University, Chung-Li, Taiwan, ROC aut Chan Chia-Yen Chunghwa Telecom Laboratories, Chung-Li, Taiwan, ROC aut Wireless Personal Communications Springer US; http://www.springer-ny.com 69/4(2013-04-01), 1165-1182 0929-6212 69:4<1165 2013 69 11277 https://doi.org/10.1007/s11277-012-0626-2 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11277-012-0626-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pao Wei-Chen Information and Communications Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, ROC aut NATIONALLICENCE 700 1- Chen Yung-Fang Department of Communication Engineering, National Central University, Chung-Li, Taiwan, ROC aut NATIONALLICENCE 700 1- Chan Chia-Yen Chunghwa Telecom Laboratories, Chung-Li, Taiwan, ROC aut NATIONALLICENCE 773 0- Wireless Personal Communications Springer US; http://www.springer-ny.com 69/4(2013-04-01), 1165-1182 0929-6212 69:4<1165 2013 69 11277 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer