• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5A
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• pp.536-542
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• 2011

For efficient utilization of spectrum resources in TV white space after DTV transition, FCC allowed usage of the spectrum for CR system. The CR system is required to cognize channel usage state for utilizing the unused spectrum in TV white space which coexists various primary and secondary systems. In the meantime, as a demand for high throughput communication had been increased recently, CR systems also consider to adopt channel bonding technology, thus spectrum sensing for channel bonded system is essentially required. In this paper, we propose a novel spectrum sensing algorithm for channel bonding system using a single channel receiver. For IEEE 802.l1af signal, the proposed algorithm provide detection probability of 90% with false alarm probability 10% at SNR -18dB for single channel system and at SNR -7dB for 8 channel bonded system, respectively. Utilizing the proposed scheme, we can detect channel bonded signal using only a single receiver, therefore system overhead for spectrum sensing can be reduced significantly.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.50-59
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• 2011

In this paper, we present a spectrum sensing method by exploiting the relationship of previous and current detected data sets in frequency domain. Most of the traditional spectrum sensing methods only consider the current detected data sets of Primary User (PU). Previous state of PU is a kind of conditional probability that strengthens the reliability of the detector. By considering the relationship of the previous and current spectrum sensing, cross entropy-based spectrum sensing is proposed to detect PU signal more effectively, which has a strengthened performance and is robust. When previous detected signal is noise, the discriminating ability of cross entropy-based spectrum sensing is no better than conventional entropy-based spectrum sensing. To address this problem, we propose an improved cross entropy-based frequency-domain spectrum sensing. Regarding the spectrum sensing scheme, we have derived that the proposed method is superior to the cross entropy-based spectrum sensing. We proceed a comparison of the proposed method with the up-to-date entropy-based spectrum sensing in frequency-domain. The simulation results demonstrate the performance improvement of the proposed spectrum sensing method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.1
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• pp.88-97
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• 2013

Most of the traditional spectrum sensing methods consider only the current detected data sets of Primary User (PU). However previous state of PU is a kind of conditional probability that strengthens the reliability of the detector. Therefore, in the cross entropy spectrum sensing method, relationship of the previous and current spectrum sensing is considered to detect PU signal more effectively. But these cross entropy spectrum sensing methods only consider the ideal system. In other words, PU always occupy the channel during the same period. However, PU can occupy the channel either for a longer or a shorter period than the ideal case in the real system. For this reason, the spectrum sensing performance can be varied. In this paper, we propose the method that can maintain the performance of spectrum sensing in the real system and we confirm the results with the help of simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.101-108
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• 2013

In this paper, we propose a method in which the negative acknowledge (NACK) message is used as command for cooperation and spectrum sharing. This allows for an automatic request for cooperation and sharing when the direct link of the primary user is in outage, and also allows for saving the number of control messages in cooperation-spectrum sharing based paradigm. In the sharing phase, the selected relay shares a power fraction of $1-{\alpha}$ for secondary transmitted signal while the remaining of ${\alpha}$ is for primary retransmitted signal. In the case of no relay collected, primary transmitter uses NACK as a command to retransmit the signal with fully power fraction (${\alpha}=1$). Both systems are assumed to employ BPSK signals. In this scheme, we propose the joint optimal decoding in the secondary user. The frame error rate (FER) performance at both systems is then analyzed. The theoretical and simulation results validate the analysis and confirm the efficiency of the protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8C
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• pp.529-535
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• 2011

After permission for utilization of TV white space by FCC, a lot of attentions are focused on spectrum sensing, and various spectrum sensing methods have been proposed. However, they do not consider real environment, thus they are hard to achieve the required performance. In this paper, we propose resolutions for the problem which could be occurred in implementation of spectrum sensing module and verify performance of the proposed methods with computer simulation. The first proposed method utilizes channel status information to separate received signal and spurious for reducing false alarm probability caused by system internal spurious. The another proposed scheme is subband normalization method to prevent miss detection caused by multiple narrow band signals with different received signal strength. The simulation results verify that we can prevent false alarm cause by spurious components with the proposed system internal spurious cognition. Moreover, the proposed subband normalization method shows that it could overcome performance degradation caused by received signal strength difference.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.633-639
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• 2009

For operation of IEEE 802.22 WRAN system, spectrum sensing is a essential function. However, due to strict sensing requirement of WRAN system, spectrum sensing process of CR nodes require long quiet period. In addition, CR nodes sometimes fail to detect licensed users due to shadowing effect of wireless communication environment. To overcome this problem, CR nodes collaborate with each other for increasing the sensing reliability or mitigating the sensitivity requirement. A general approach for decision fusion, the "k out of N" rule is often taken as the decision fusion rule for its simplicity. However, since k out of N rules can not achieve better performance than the highest SNR node when SNR is largely different among CR nodes, the local SNR of each node should be considered to achieve better performance. In this paper, we propose two novel data fusion methods by utilizing confidence vector which represents the confidence level of individual sensing result. The simulation results show that the proposed schemes improve the signal detection performance than the conventional data fusion algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1079-1085
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• 2007

This Paper Proposes a new optimization algorithm named by GBNSGA-II(Goal-pareto Based Non-dominated Sorting Genetic Algorithm-II) which uses Goal Programming to find non-dominated solutions in NSGA-II. Although the conventional NSGA is very popular to solve multiobjective optimization problem, its high computational complexity, lack of elitism and difficulty of selecting sharing parameter have been considered as problems to be overcome. To overcome these problems, NSGA-II has been introduced as the alternative for multiobjective optimization algorithm preventing aforementioned defects arising in the conventional NSGA. Together with advantageous features of NSGA-II, this paper proposes rather effective optimization algorithm formulated by purposely combining NSGA-II algorithm with GP (Goal Programming) subject to satisfying multiple objectives as possible as it can. By conducting computer simulations, the superiority of the proposed GBNSGA-II algorithm will be verified in the aspects of the effectiveness on optimization process in presence of a priori constrained goals and its fast converging capability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.8
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• pp.761-767
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• 2011

In this paper, to improve performance of spectrum sensing, we propose the method which can find optimal threshold based on power of PU(Primary User) signal. To find optimal threshold value, we will use mathematical method, and find threshold which can has lowest error probability. Each SU(Secondary User) use this threshold and All Su makes local decision. All Su Send local decision to FC(Fusion Center). In this paper we consider K-out-of-n rule to combining local decision. To make global decision value, FC find optimal n. In the FC. FC received local decision which has lowest error probability and using optimal n and these vaule. FC make global decision value. In this paper, to analysis performance proposed scheme, we simulate proposed scheme using matlab and compare with traditional OR Rule. As a result of simulation, we can know that preposed scheme can get a better performance than traditional OR rule.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.7
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• pp.3095-3099
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• 2016

Background: Cervical cancer is the most frequently diagnosed cancer among women in India. Understanding quality of life (QOL) in women undergoing chemo-radiotherapy for cervical cancer will help in introducing interventions for better care and outcomes in these women. This study assessed QOL before and after chemo-radiotherapy in cervical cancer patients. Materials and Methods: This follow-up study covered sixty-seven newly diagnosed women with advanced cervical cancer (stages 2b to 4b). Structured questionnaires (the European Organization for Research and Treatment of Cancer, EORTC QLQ-C30 and EORTC QLQ-CX24) were used to assess the change in QOL after 6 months of treatment. Results: The mean age of women at the time of detection of cervical cancer was $52.3{\pm}11.29$ years (Range 30-75 years). Six months survival was 92.53%. The mean global health score of cervical cancer patients after six months of treatment was 59.52, which was significantly higher than the pre-treatment score of 50.15 (p=0.00007). Physical, cognitive and emotional functioning improved significantly (p<0.05) after treatment. Fatigue, pain, insomnia and appetite loss improved but episodes of diarrhea increased after treatment. The mean "symptoms score" using EORTC QLQ-CX24 post treatment was 20.0 which was significantly lower as compared to the pre- treatment score 30.0 (p<0.00001). Sexual enjoyment and sexual functioning decreased significantly after treatment. Conclusions: QOL of newly diagnosed cervical cancer patients improved significantly following chemo-radio therapy. Enhancement was also demonstrated on three of the five functional scales of EORTC QLQ-C30. To further improve QOL, interventions focusing on social and psychological support and physical rehabilitation may be needed.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.58
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• pp.38-49
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• 2006

In order to increase the spectrum efficiency, recently, there is the number of studies for CR technology. For instance, IEEE 802.22 WRAN(Wireless Regional Area Network) WG considered the CR technology as a solution of WRAN system to serve the high speed internet service(1.5 Mbps down stream and 384 kbps up stream) in 100 km overall coverage and 54 MHz-746 MHz band. Basically, in MAC point of view, the WRAN system have been standardizing based on the IEEE 802.16 MAC layer features such as Data transmission method, QoS provision and Bandwidth request schemes. Additionally, the WRAN system further include CR nature functions such as incumbent user protection, self coexistence which would be importantly considered. Also, the inherent WRAN functions are added such as channel bonding and fractional bandwidth usage. This paper mainly explained frame structure, IU protection, self coexistence which are key functions of WRAN system. Finally, in this paper, we expressed a prospect of IEEE 802.22 WRAN standardization.