• Journal of Advanced Navigation Technology
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• v.19 no.4
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• pp.318-322
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• 2015

In wireless communication networks, most of the prediction techniques are used for predicting the amount of resource required by user's calls for improving their demanding quality of service. However, we propose a channel allocation scheme based on predicting the resources of white spectrum holes for improving the QoS of rental user's spectrum handoff calls for cognitive radio networks in this paper. This method is supported by Wiener predictor to predict the amount of white spectrum holes of license user's free spectrum resources. We classify rental user's calls into initial calls and spectrum handoff calls, and some portion of predicted spectrum-hole resources is reserved for spectrum handoff calls' priority allocation. Simulations show that the performance of the proposed scheme outperforms in spectrum handoff call's dropping rate than an existing method without spectrum hole prediction(11% average improvement in 50% reservation).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.560-568
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• 2012

Spectrum sensing and spectrum decision are the main functions that cognitive radios (CRs) have to perform in order to get the best available spectrum band for the establishment of a wireless communication. These problems are worsened in the presence of users with different demands and spectrum channels with different properties in a heterogeneous network. The primary objective in this work is to design and simulate a new spectrum decision algorithm for heterogeneous cognitive radio system. To this end, first, we consider all cognitive users are separated into different traffic classes according to their Quality of Service (QoS). The cognitive users within one traffic class perform spectrum sensing in centralized group-based cooperative spectrum sensing system and the users of different traffic classes share the sensing results. Second, we propose a novel use of the Analytic Hierarchy Process (AHP) to optimally select available bands according to user requirements and detected spectrum channel characteristics (SCC). In this paper, utility function is used as spectrum decision algorithm. Simulation results demonstrate that the proposed method shows can effectively select the best available spectrum channels with a low complexity.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.13-21
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• 2019

The restricted network or the unbalanced distribution of spectrum is causing the problems of lack of spectrum resources and deterioration of the service quality. In addition, the existing centralized radio sharing method has not been a fundamental solution for radio sharing and is inefficient in terms of cost, convenience, and security. In this paper, we propose a blockchain-based spectrum sharing as a low-cost, trustworthy, high-efficiency platform that can distribute and share spectrum resources, and propose policies to realize this. In the spectrum sharing platform, spectrum information about Wi-Fi AP and LTE mobile hotspot is registered in the blockchain, and spectrum sharers and users can conclude peer-to-peer spectrum sharing contract quickly and efficiently through smart contract. The pay for the shared spectrum resources and reward for spectrum quality management open platform ecosystem to activate the circulation-sharing and it can provide a convenient and efficient public wireless infrastructure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1001-1008
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• 2010

In this paper, we propose the dynamic spectrum allocation (DSA) algorithm using spectrum sharing method considering the long-term priority between NOs and service classes for the maritime communication system environment where a ship locates at either near shore (or land) or off-shore. It was shown that the proposed algorithm using spectrum sharing with priorities could deliver better satisfaction ratio (SR) than the fixed allocation schemes, in the context of provision of required bandwidth (or spectrum) for each users. Therefore, we conclude that the proposed DSA with priorities could apply to the maritime communication environment and exploit the under-used (or unused, idle) spectrum of terrestrial communication networks.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.6
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• pp.357-366
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• 2013

Spectrum sensing, as a fundamental functionality of Cognitive Radio (CR), enables Secondary Users (SUs) to monitor the spectrum and detect spectrum holes that could be used. Recently, the security issues of Cognitive Radio Networks (CRNs) have attracted increasing research attention. As one of the attacks against CRNs, a Primary User Emulation (PUE) attack compromises the spectrum sensing of CR, where an attacker monopolizes the spectrum holes by impersonating the Primary User (PU) to prevent SUs from accessing the idle frequency bands. Energy detection is often used to sense the spectrum in CRNs, but the presence of PUE attack has not been considered. This study examined the effect of PUE attack on the performance of energy detection-based spectrum sensing technique. In the proposed protocol, the stationary helper nodes (HNs) are deployed in multiple stages and distributed over the coverage area of the PUs to deliver spectrum status information to the next stage of HNs and to SUs. On the other hand, the first stage of HNs is also responsible for inferring the existence of the PU based on the energy detection technique. In addition, this system provides the detection threshold under the constraints imposed on the probabilities of a miss detection and false alarm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.613-631
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• 2013

Cognitive radio (CR) is proposed as a key solution to improve spectral efficiency and overcome the spectrum scarcity. Spectrum sensing is an important task in each CR system with the aim of identifying the spectrum holes and using them for secondary user's (SU) communications. Several conventional methods for spectrum sensing have been proposed such as energy detection, matched filter detection, etc. However, the main limitation of these classical methods is that the CR network is not able to communicate with its own base station during the spectrum sensing period and thus a fraction of the available primary frame cannot be exploited for data transmission. The other limitation in conventional methods is that the SU data frames should be synchronized with the primary network data frames. To overcome the above limitations, here, we propose a spectrum sensing technique based on blind source separation (BSS) that does not need time synchronization between the primary network and the CR. Moreover, by using the proposed technique, the SU can maintain its transmission with the base station even during spectrum sensing and thus higher rates are achieved by the CR network. Simulation results indicate that the proposed method outperforms the accuracy of conventional BSS-based spectrum sensing techniques.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.212-218
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• 2013

This paper presents an SVD(Singular Value Decomposition)-Pseudo Spectrum method for SAR (Synthetic Aperture Radar) imaging. The purpose of this work is to improve resolution and target separability of SAR images. This paper proposes SVD-Pseudo Spectrum method whose advantages are noise robustness, reduction of sidelobes and high resolution of spectral estimation. SVD-Pseudo Spectrum method uses Hankel Matrix of signal components and SVD (Singular Value Decomposition) method. In this paper, it is demonstrated that the SVD-Pseudo Spectrum method shows better performance than the matched filtering method and the conventional super-resolution based multiple signal classification (MUSIC) method in SAR image processing. The targets to be separated are modeled, and this modeled data is used to demonstrate the performance of algorithms.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.3
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• pp.71-82
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• 2009

As a solution to spectrum under-utilization problem, Cognitive radio (CR) introduces a dynamic spectrum access technology. In the area, one of the most important problems is how secondary users (SUs) should choose between the available channels, which means how to achieve load balancing between channels. We consider spectrum load balancing problem for CR system in frequency domain and especially in time domain. Our objective is to balance the load among the channels and balance the occupied time length of slots for a fixed channel dynamically in order to obtain a user-optimal solution. In frequency domain, we refer to Dynamic Noncooperative Scheme with Communication (DNCOOPC) used in distributed system and a distributed Dynamic Spectrum Load Balancing algorithm (DSLB) is formed based on DNCOOPC. In time domain, Spectrum Load Balancing method with QoS support is proposed based on Dynamic Feed Back theory and Hash Table (SLBDH). The performance of DSLB and SLBDH are evaluated. In frequency domain, DSLB is more efficient compared with existing Compare_And_Balance (CAB) algorithm and gets more throughput compared with Spectrum Load Balancing (SLB) algorithm. Also, DSLB is a fair scheme for all devices. In time domain, SLBDH is an efficient and precise solution compared with Spectrum Load Smoothing (SLS) method.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.4
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• pp.189-196
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• 2020

In cognitive radio networks, secondary transmitters should cease its transmission immediately on detecting of primary transmission in the spectrum they are accessing. Then they should exploit another idle spectrums and handoff to the newly found idle spectrums, which is called spectrum rendezvous. With regards to spectrum rendezvous, most of related work presume the existence of dedicated common control channel used by secondary users for exchanging the information of idle spectrums. However, this presumption is not feasible in real world cognitive radio scenario. Therefore we address a blind spectrum rendezvous scheme with no need of separate control channel. Furthermore we consider maintaining one or more extra spectrums (channels) to expedite the spectrum rendezvous. Our scheme lets secondary users maintain extra spectrums by exchanging the spectrum information periodically during normal communications. The one of the extra spectrums are regarded as a candidate spectrum that the users can handoff to on detecting the primary transmission. We evaluate that our blind scheme can help to reduce the rendezvous delay in a real world cognitive radio environments with USRPs.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.20-25
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• 2014

In this paper, we provide efficient spectrum sensing technology for smooth use of frequency and energy charge of multi-copter. The proposed structures focus on improving performance of spectrum sensing that is based on Ad-hoc network. First, we explain basic principles and disadvantages of cooperative spectrum sensing and ad-hoc based spectrum sensing. To solve these problems, in this paper, we employ the beamforming technology that guarantees higher transmit primary users' signal power to secondary users in ad-hoc network. The performance of proposed algorithm is analyzed in terms of detection probabilities, and the results of this paper can be applied to the various ad-hoc based Cognitive Radio system.