Auction and Game-based Spectrum Sharing in Cognitive Radio Networks

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Dealing with uncertain entities in ontology alignment using rough sets

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, 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 components of this work in other works.Ontology alignment facilitates exchange of knowledge among heterogeneous data sources. Many approaches to ontology alignment use multiple similarity measures to map entities between ontologies. However, it remains a key challenge in dealing with uncertain entities for which the employed ontology alignment measures produce conflicting results on similarity of the mapped entities. This paper presents OARS, a rough-set based approach to ontology alignment which achieves a high degree of accuracy in situations where uncertainty arises because of the conflicting results generated by different similarity measures. OARS employs a combinational approach and considers both lexical and structural similarity measures. OARS is extensively evaluated with the benchmark ontologies of the ontology alignment evaluation initiative (OAEI) 2010, and performs best in the aspect of recall in comparison with a number of alignment systems while generating a comparable performance in precision

Cooperative SWIPT MIMO-NOMA for reliable THz 6G communications

In this paper, cooperative simultaneous wireless information and power transfer (SWIPT) terahertz (THz) multiple-input multiple-output (MIMO) nonorthogonal multiple access (NOMA) are considered. The aim is to improve wireless connectivity, resource management, scalability, and user fairness, as well as to enhance the overall performance of wireless communications and reliability. We optimized the current wireless communication systems by utilizing MIMO-NOMA technology and THz frequencies, exploring the performance and gains obtained. Hence, we developed a path-selection mechanism for the far user to enhance the system performance. The EH SWIPT approach used to improve THz communications performance was investigated. Moreover, we proposed a reliable transmission mechanism with a non-LoS (NLoS) line of THz communications for open areas or any location where the intelligent reflecting surface (IRS) cannot be deployed, in addition to using the cheap decode-forward (DF) relaying instead of IRS. The performance and scalability of the upgradeable system were examined, using adjustable parameters and the simplest modulation scheme. The system presents a noticeable improvement in energy efficiency (EE) and spectral efficiency (SE), in addition to reliability. Accordingly, the outcome showed an improvement in the overall reliability, SE, EE, and outage probability as compared to the conventional cooperative networks of the recent related work (e.g., cooperative MIMO-NOMA with THz) by multiple times with a simpler design, whereas it outperformed our previous work, i.e., cooperative SWIPT SISO-NOMA with THz, by more than 50%, with a doubled individual user gain. This system reduces the transceiver hardware and improves reliability with increasing transmission rates

Mutual Coupling Reduction with a novel Fractal Electromagnetic Band Gap Structure

This work shows the effect of a novel Fractal based Electromagnetic Band Gap (FEBG) structure between dual PIFAs antenna elements. The FEBG structure without any shorting pins builds on a well-known fractal structure called Sierpinski carpet, where two iterations have been applied as a uniplanar EBG between dual PIFAs elements to increase the isolation. The proposed antenna can operate at approximately 2.65 GHz for wireless Long Term Evolution (LTE) application with compact design dimensions. The simulations are carried out with Ansoft HFSS ver 17.0. The second iterative order FEBG band-gap characteristic is verified using more computationally efficient analysis. An investigation on coupling reduction showed more than 27 dB, and 40 dB in E-plane and H-plane; respectively between the dual antenna elements is achieved for an antenna spacing less than half wavelength. The proposed antennas with and without second iterative order FEBG are fabricated and measured. The measurement results are in good agreement with the simulated results. Moreover, the envelope correlation of antenna elements with the proposed FEBG is quite smaller than that of antenna elements without FEBG, which gives the proposed system an excellent diverse performance and suitable for the use in low-frequency narrow-band MIMO applications

Spread spectrum technique to improve the performance of radio over fibre for microcellular GSM networks

This paper presents a GSM-specific assessment of the performance of a radio over fibre link between a remote antenna unit and GSM base station. The intermodulation distortion (IMD) has been analysed for a system using the subcarrier multiplexing (SCM). A novel technique using direct sequence spread spectrum is proposed to minimize the IMD by decreasing the signal amplitude prior to a direct modulation of a laser diode. The results show that the optical fibre microcellular is outperforming the full wireless system