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Nhan Nguyen-Thanh,Insoo Koo IEEE 2011 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.60 No.1
<P>Sensing spectra in a reliable and efficient manner is fundamental to cognitive radio (CR). Ensuring cooperation among spectrum sensing devices is an appropriate method when a CR system is under deep shadowing and in a fading environment. In this paper, an enhanced scheme for cooperative spectrum sensing (CSS) based on efficient quantization and the Dempster-Shafer (D-S) theory of evidence is proposed. The proposed scheme includes an effective quantizer for the sensing data by utilizing special properties of the hypothesis distribution under different signal-to-noise ratios (SNRs) of the primary signal. As a result, the required bandwidth for the reporting channel is reduced while the advantage for combinations of the D-S theory is maintained. Simulation results revealed that significant improvements in the CSS gain, as well as a reduction in the system overhead, were achieved.</P>
Nhan Nguyen-Thanh,Insoo Koo IEEE 2012 IEEE SENSORS JOURNAL Vol.12 No.6
<P>Event detection is a central issue in wireless sensor networks. In this paper, we propose a novel event-detection scheme which utilizes empirical distribution and the combination method of evidence theory. Unlike conventional methods where the sensor uses energy detection to determine the presence or absence of an event, our scheme uses a goodness-of-fit (GOF) test to measure the distance between the observed data and the empirical distributions of both the presence and absence hypotheses. Multiple types of such two-sided GOF tests are combined to create a well-adapted detector using evidence theory. The simulation results show that the proposed detector is more accurate than conventional detectors in different kinds of noisy environments.</P>
Nguyen-Pham, Thanh-Nhan,Jung, Sung-Hoon,Vo, Manh-Cuong,Thanh-Tran, Huong-Thi,Lee, Youn-Kyung,Lee, Hyun-Ju,Choi, Nu-Ri,Hoang, My-Dung,Kim, Hyeoung-Joon,Lee, Je-Jung Lippincott-Raven 2015 Journal of immunotherapy Vol.38 No.8
We investigated the efficacy of lenalidomide (LEN) in combination with dendritic cell (DC) vaccination in the MOPC-315 murine myeloma model. After tumor growth, LEN was injected intraperitoneally for 4 consecutive days in combination with DC vaccination. The combination of LEN and vaccination efficiently inhibited tumor growth compared with the single agents alone. A cytotoxic assay revealed that the anticancer effects of DC vaccination plus LEN involved not only generation of antigen-specific cytotoxic T lymphocytes but also NK cells. Vaccinated mice had reduced numbers of suppressor cells, including both myeloid-derived suppressor cells and regulatory T cells, in the spleen. The proportions of CD4 and CD8 T cells increased in the spleen, and a Th1 cytokine (interferon-&ggr;) rather than a Th2 cytokine (interleukin-10) was synthesized in response to tumor antigens. LEN enhanced the innate immune response by modulating NK cell numbers and function. In addition, LEN reduced the production levels of angiogenesis-inducing factors in tumor-bearing mice. Together, these results suggest that a combination of LEN and DC vaccination may synergistically enhance anticancer immunity in the murine myeloma model, by inhibiting immunosuppressor cells and stimulating effector cells, as well as effectively polarizing the Th1/Th2 balance in favor of a Th1-specific immune response.
Nguyen Quang Bau,Thi Thanh Nhan,Nguyen Vu Nhan 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.4
Analytic expressions for the absorption coefficient (ACF) of a weak electromagnetic wave (EMW)caused by electrons confined in rectangular quantum wires (RQWs) in the presence of laser radiationare calculated using the quantum kinetic equation for electrons in the case of electron-optical phononscattering. The dependence of the ACF of a weak EMW on the intensity E01 and the frequency 1 of the external laser radiation, the intensity E02 and the frequency2 of the weak EMW, thetemperature T of the system and the size L (Lx and Ly) of the RQWs is obtained. The resultsare numerically calculated and discussed for GaAs/GaAsAl RQWs. The numerical results showthat the ACF of a weak EMW in RQWs can have negative values. Thus, in the presence of laserradiation, under proper conditions, a weak EMW is increased. This is different from the similarproblem in bulk semiconductors and from the case without laser radiation
Optimal Truncated Ordered Sequential Cooperative Spectrum Sensing in Cognitive Radio
Nhan Nguyen-Thanh,Insoo Koo IEEE 2013 IEEE SENSORS JOURNAL Vol.13 No.11
<P>The cost for increasing the accuracy of cooperative spectrum sensing in cognitive radio requires a long time for collecting sensing data. Sequential fusion, in which the sensing data reports are sequentially collected, combined, and tested with two thresholds for deciding to wait for the next data report or concluding the presence or absence of the primary signal, is considered to reduce the collecting time. A further reduction in the average sequential report number (ASN) can be achieved by arranging the reports in descending order of data quality where the better sensing data is reported earlier. In this paper, the ASN and the error probability of the ordered sequential fusion are analytically calculated based on the direct method. The results are then adopted to design an optimal method for obtaining the optimal sequential thresholds and truncated point. The optimal truncated point enables one to minimize the ASN by discarding the sensing data with low quality, while the optimal sequential thresholds ensure the maintaining of the sensing performance of sequential fusion be the same level to that of the conventional parallel fusion.</P>
Nhan Nguyen-Thanh,Insoo Koo IEEE 2009 IEEE communications letters Vol.13 No.7
<P>This letter proposes an enhanced scheme for cooperative spectrum sensing which utilizes the signal to noise ratios to evaluate the degree of reliability of each local spectrum sensing terminal on a distributed Cognitive Radio network. The terminals' reliability weight is applied to adjust its sensing data more accurately before making fusion by Dempter-Shafer theory of evidence. Simulation results show that significant improvement of the cooperative spectrum sensing gain is achieved by our scheme.</P>
NGUYEN-THANH, Nhan,KOO, Insoo The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.12
<P>Spectrum sensing is a fundamental function for cognitive radio network to protect transmission of primary system. Cooperative spectrum sensing, which can help increasing sensing performance, is regarded as one of the most promising methods in realizing a reliable cognitive network. In such cooperation system, however the communication resources such as sensing time delay, control channel bandwidth and consumption energy for reporting the cognitive radio node's sensing results to the fusion center may become extremely huge when the number of cognitive users is large. In this paper, we propose an ordered sequential cooperative spectrum sensing scheme in which the local sensing data will be sent according to its reliability order to the fusion center. In proposed scheme, the sequential fusion process is sequentially conducted based on Dempster Shafer theory of evidence's combination of the reported sensing results. Above all, the proposed scheme is highly feasible due to the proposed two ordered sequential reporting methods. From simulation results, it is shown that the proposed technique not only keeps the same sensing performance of non-sequential fusion scheme but also extremely reduces the reporting resource requirements.</P>