Browsing by Subject "Transmitted signal"
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Item Open Access Convexity properties of outage probability under Rayleigh fading(IEEE, 2012) Dülek, Berkan; Vanlı, N. Denizcan; Gezici, SinanIn this paper, convexity properties of outage probability are investigated under Rayleigh fading for an average power-constrained communications system that employs maximal-ratio combining (MRC) at the receiver. By studying the first and second order derivatives of the outage probability with respect to the transmitted signal power, it is found out that the outage probability is a monotonically decreasing function with a single inflection point. This observation suggests the possibility of improving the outage performance via on-off type power randomization/sharing under stringent average transmit power constraints. It is shown that the results can also be extended to the selection combining (SC) technique in a straightforward manner. Finally, a numerical example is provided to illustrate the theoretical results. © 2012 IEEE.Item Open Access Particle swarm optimization based channel identification in cross-ambiguity domain(IEEE, 2010) Güldoğan, Mehmet Burak; Arıkan, OrhanIn this paper, a new array signal processing technique by using particle swarm optimization (PSO) is proposed to identify multipath channel parameters. The proposed technique provides estimates to the channel parameters by finding a global minimum of an optimization problem. Since the optimization problem is formulated in the cross-ambiguity function (CAF) domain of the transmitted signal and the received array outputs, the proposed technique is called as PSO-CAF. The performance of the PSO-CAF is compared with the space alternating generalized expectation maximization (SAGE) technique and with another recently proposed PSO based technique for various SNR values. Simulation results indicate the superior performance of the PSO-CAF technique over mentioned techniques for all SNR values. ©2010 IEEE.Item Open Access Real time noise-cancellation using ICA, PSO and PE(IEEE, 2012) Bor, R. İrem; Ider, Y. Ziya; Arıkan, Orhan; Ertan, ErdemIn order to provide noiseless transmission of speech in wireless communication systems a real-time implementable noise cancellation algorithm is developed. Speech and noise sources are not known but only their mixtures are observed. That system is modeled with instantaneous mixture model. Combination of independent component analysis (ICA) and particle swarm optimization (PSO) algorithms is used to separate speech and noise. However, ICA has an ambiguity such that it is not possible to know which one of the separated signals is speech or noise. As a result, the transmitted signal can be noise, instead of speech. To overcome this ambiguity problem, a pitch extraction (PE) algorithm is developed and combined with ICA-PSO. ICAPSO-PE algorithm is implemented in MATLAB. Contributions of this work are modifying objective functions of ICA algorithm to make them more robust, combining ICA with PSO to make it work fast and robust, and overcoming the ambiguity problem using PE algorithm. © 2012 IEEE.