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Xu Q.,Xian Communication Institute | Wang L.,Xi'an University of Science and Technology | Wang N.,Xian Communication Institute | Hei X.,Xi'an University of Science and Technology | Zhao L.,Beijing Institute of Technology
Engineering Applications of Artificial Intelligence | Year: 2014

Diverse forms of opposition are already existent virtually everywhere around us, and utilizing opposite numbers to accelerate an optimization method is a new idea. Since 2005, opposition-based learning is a fast growing research field in which a variety of new theoretical models and technical methods have been studied for dealing with complex and significant problems. As a result, an increasing number of works have thus proposed. This paper provides a survey on the state-of-the-art of research, reported in the specialized literature to date, related to this framework. This overview covers basic concepts, theoretical foundation, combinations with intelligent algorithms, and typical application fields. A number of challenges that can be undertaken to help move the field forward are discussed according to the current state of the opposition-based learning. © 2013 Elsevier Ltd. All rights reserved.


Rao R.,Xi'an Jiaotong University | Rao R.,Xian Communication Institute | Tang T.,Xi'an Jiaotong University
Journal of the Optical Society of America B: Optical Physics | Year: 2011

We studied active lossless single-interface surface plasmon polariton (SPP) waveguides with extremely short guided wavelengths and optimally designed a nanometer-size active lossless single-mode dielectric-loaded SPP waveguide (DLSPPW). The sufficient condition, under which both lossless propagation and extremely short guided wavelength can be achieved simultaneously in active single-interface SPP waveguides, is presented. Underthe same condition, the gain coefficient of the active medium reaches its maximum. These maximum gain coefficients are calculated in cases when the metals Au, Ag, and Cu are used, respectively, operating in wavelengths ranging from 330 to 1600nm. From the above calculation results, the working wavelength and metal are selected for the active DLSPPW. A single-mode lossless DLSPPW is designed and optimized using the effective index and finite element methods in vacuum wavelength 450nm. In this waveguide, 95% of the energy flux is constrained within a core area with thickness of 20nm and width of 22nm. © 2011 Optical Society of America.


Rao R.,Xi'an Jiaotong University | Rao R.,Xian Communication Institute | Tang T.,Xi'an Jiaotong University
Journal of Physics D: Applied Physics | Year: 2012

A silicon-based hybrid gap surface plasmon polariton (SPP) waveguide consisting of an active InP/GaInAsP/InP double heterostructure layer, a silver cladding with a rectangular bump and a gap between them is presented. Based on this waveguide, all the SPP waveguides and even the SPP components share a common planar active medium layer in the whole photonic integration circuit chip, so not only can both the waveguide structure width and the mode lateral confinement width be of nanoscale simultaneously, but optical pumping can also be easily realized for compensating the propagation loss of all the SPP waveguides and components. By means of thickening the active GaInAsP layer and thinning the gap, the threshold gain coefficient is reduced to an achievable range and the mode confinement size is dropped to the nanoscale. Numerical simulation suggests that when the gap size is 50nm×10nm and the GaInAsP height is 350nm, by adjusting the metal bump height, the effective mode area is at λ 0=1550nm and the full-width at half-maximum of the Poynting vector magnitude is 66nm and the threshold gain coefficient is 158.5cm 1 or 850.9cm 1 for different Ag permittivities coming from two sources. © 2012 IOP Publishing Ltd.


Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará | Jiang Z.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2011

Three low-complexity relay-selection strategies, namely, selective amplify and forward (S-AF), selective decode and forward (S-DF), and amplify and forward with partial relay selection (PRS-AF) in a spectrum-sharing scenario are studied. First, we consider a scenario where perfect channel state information (CSI) is available. For these scenarios, the respective asymptotic outage behaviors of the secondary systems are analyzed, from which the diversity and coding gains are derived and compared. Unlike the coding gain, which is shown to be very sensitive with the position of the primary receiver, the diversity gain of the secondary system is the same as the nonspectrum-sharing system. In addition, depending on the cooperative strategy employed, an increase in the number of relays may lead to severe loss of the coding gain. Afterwards, the impacts of imperfect CSI regarding the interference and transmit channels on the outage behavior of the secondary systems are analyzed. On one hand, the imperfect CSI concerning the interference channels only affects the outage performance of the primary system, whereas it has no effect on the diversity gain of the secondary system. On the other hand, the imperfect CSI concerning the transmit channels of the secondary systems may reduce the diversity gain of the three relay-selection strategies to unity, which is validated by both theoretical and numerical results. © 2006 IEEE.


Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará | Jiang Z.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2011

This paper proposes a new efficient scheme for the combined use of cooperative diversity and multiuser diversity. Considering a decode-and-forward (DF) opportunistic relaying strategy, we first study the outage behavior of the joint sourcerelay-selection scheme with/without direct links, from which the significance of the direct links is recognized. Motivated by the crucial role of these links on the system performance, a two-step selection scheme is proposed, which first selects the best source node based on the channel quality of the direct links and then selects the best link from the selected source to the destination. The proposed scheme significantly reduces the amount of channel estimation while achieving comparable outage performance to that using the joint selection scheme. Most importantly, the achieved diversity order is the same as that using the joint selection scheme. In addition, assuming an amplify-and-forward (AF) opportunistic relaying strategy, the outage behavior of this two-step scheme is also analyzed, and its availability is confirmed as well. © 2006 IEEE.


Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará | Jiang Z.,Xian Communication Institute
IEEE Transactions on Wireless Communications | Year: 2012

This Letter proposes a mechanism to combine multiuser diversity (MUD) and incremental relaying in a multiuser two-way relaying system, where one end-source exchanges messages with one out of N available end-sources by using a half-duplex amplify-and-forward (AF) relay. Outage analysis for the proposed scheme is carried out and, compared with the time division broadcast (TDBC) protocol, reveals that it not only realizes full diversity order (N+1) but also achieves improved expected spectral efficiency. Also, it is indicated that the expected spectral efficiency of the proposed scheme approaches that of the analog network coding (ANC) protocol in high signal-to-noise ratio (SNR) regime. Furthermore, the finite-SNR diversity-multiplexing tradeoff (DMT) is examined, from which the superiority of the proposed scheme to TDBC is confirmed as well. Other insightful comparisons in terms of the outage performance are presented that show the practical usefulness of our multiuser two-way relaying framework. © 2012 IEEE.


Da Costa D.B.,Federal University of Ceará | Ding H.,Xidian University | Ding H.,Xian Communication Institute | Yacoub M.D.,University of Campinas | Ge J.,Federal University of Ceará
IEEE Transactions on Vehicular Technology | Year: 2012

The performance of dual-hop amplify-and-forward (AF) two-way relaying systems with multiple cochannel interferers at the AF relay and two noisy end-sources is investigated. Assuming a Nakagami- $m$ fading environment, closed-form approximate expressions for the outage probability, average error probability, and achievable sum rate are derived, yielding results which, in practice, are indistinguishable from the exact analysis. In addition, the derived approximate expressions are evaluated instantaneously, regardless of the number of interferers, highly contrasting with the intricacy and computational inefficiency inherent to the exact formulations, which requires the evaluation of nested multiple integrals, i.e., a problem that becomes computationally intractable as the number of interferers increases. Our analysis allows for general operating scenarios with distinct integer-value Nakagami-$m$ fading parameters and unequal average fading power values between the hops. Monte Carlo simulation results are presented to corroborate the tightness of the proposed approximations. © 2012 IEEE.


Da Costa D.B.,Federal University of Ceará | Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University
IEEE Communications Letters | Year: 2011

In this letter, we investigate the outage performance of dual-hop decode-and-forward (DF) cooperative systems in an interference-limited Nakagami-m fading environment. More specifically, assuming the presence of Nakagami-m faded multiple co-channel interferers at the DF relay and a noisy destination, simple accurate closed-form approximations for the end-to-end outage probability are derived. To this end, moment-based estimators are used to attain the appropriate Nakagami-m fading parameters. Simulation results are presented in order to confirm the accuracy of the proposed approximations. © 2006 IEEE.


Zheng W.,Xian Communication Institute
Journal of Information and Computational Science | Year: 2015

Aiming at the sub-Nyquist sampled signal with several sub-bands, a Time-frequency Extremum Function (TFEF) is proposed to extract the Enhanced Typical Sparse Time-frequency Feature (ETSTF) of the signal in order to solve the imbalance problem of time-frequency feature extracting for various sub-bands with different SNR (Signal-to-Noise Ratio)s. And an evolutionary clustering algorithm is developed for the ETSTF data set wiping off the false classes' negative effect of idle sub-bands. Based on the clustering results, a novel strategy will be established subsequently for the wide-band spectrum sensing. Simulation experiments indicate the following. 1) The same share have the time-frequency points of various sub- bands with different SNRs extracted by TFEF, which means that TFEF enhances the time-frequency feature of the sub-band with lower SNR. 2) The time-frequency points of busy sub-bands have obvious clustering character. 3) The evolutionary clustering results neglect the idle sub-bands information and have clustering centers in the busy sub-bands. 1548-7741/Copyright © 2015 Binary Information Press


Ding H.,Xidian University | Ge J.,Xidian University | Jiang Z.,Xian Communication Institute
Electronics Letters | Year: 2010

Asymptotic average symbol error probabilities (ASEPs) using a range of modulation types are derived in closed-form for dual-hop amplify-and-forward wireless cooperative networks with partial relay selection in Rician fading. The joint impact of the Rician K-factor and the power imbalance on the ASEP of the network is investigated. As verified by simulation, the obtained ASEPs are tight bounds in medium and high signal-to-noise regions. © 2010 The Institution of Engineering and Technology.

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