A novel receiver is proposed in this paper that uses the blind adaptive multi-user detection （MUD） technique to deal with the presence of multiple-access interference （MAI） and inter-symbol interference （ISI） in...A novel receiver is proposed in this paper that uses the blind adaptive multi-user detection （MUD） technique to deal with the presence of multiple-access interference （MAI） and inter-symbol interference （ISI） in terms of high speed time-hopping ultra-wideband （TH-UWB） system. The receiver firstly adopts constrained recursive least squares constant modulus algorithm （RLS-CMA） to conduct adaptive decorrelation for eliminating MAI and ISI, and then uses projection approximation subspace tracking with deflation （PASTd） algorithm to launch channel estimation, do maximal ratio combining （MRC） and improve signal to interference plus noise ratio （SINR）. The simulation results show that the proposed receiver can go to convergence rapidly under all four IEEE＇s UWB channel models, the bit error ratio （BER） performance is better than that of the traditional receiver and rake receiver.展开更多
Two kinds of controllable doped left-handed materials （DLHMs） were designed by inserting inductors and capacitors into the traditional left-handed material （LHM） as heterogeneous elements respectively, which are D...Two kinds of controllable doped left-handed materials （DLHMs） were designed by inserting inductors and capacitors into the traditional left-handed material （LHM） as heterogeneous elements respectively, which are DLHM with inductors （LDLHM） and DLHM with capacitors （CDLHM）. The characteristics of transmission spectrum were studied by using finite-difference time-domain method （FDTD）. Compared with the traditional LHM, the resonance strength of the LDLHM is weakened and the pass-band is narrowed, but with the increase of the value of the inserted inductors, the bandwidth is expanded. As capacitors inserted into the LHM, the pass-band of the CDLHM is expanded, but the pass-band is shifted to low frequency and the bandwidth is narrowed with the increase of the value of the capacitors, meanwhile, a new generated pass-band is also shifted to low frequency. Therefore, a quantized controllable doped left-handed material can be achieved.展开更多
To improve the spectrum sensing performance in cognitive radios, a scheme of cooperative blind spectrum sensing based on autocorrelation matrix is proposed. The test statistic is extracted from the autocorrelation mat...To improve the spectrum sensing performance in cognitive radios, a scheme of cooperative blind spectrum sensing based on autocorrelation matrix is proposed. The test statistic is extracted from the autocorrelation matrix of the received signal samples and a bi-threshold hybrid decision scheme is designed for local spectrum sensing. The cognitive radio base station makes a credibility fusion based on the local soft decisions and then takes global fusion combining with the local hard decisions. The proposed method is blind in the sense since it requires no apriori knowledge of the signal and the noise power. Theoretical analysis and computer simulation results show that the proposed method can enhance the spectrum sensing capability.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars (60725105)the National Basic Research Program of China (2009CB320404)+2 种基金the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) (IRT0852)the 111 Project (B08038)Scientific Research Program Funded by Shaanxi Provincial Education Commission (2010JK666)
文摘A novel receiver is proposed in this paper that uses the blind adaptive multi-user detection （MUD） technique to deal with the presence of multiple-access interference （MAI） and inter-symbol interference （ISI） in terms of high speed time-hopping ultra-wideband （TH-UWB） system. The receiver firstly adopts constrained recursive least squares constant modulus algorithm （RLS-CMA） to conduct adaptive decorrelation for eliminating MAI and ISI, and then uses projection approximation subspace tracking with deflation （PASTd） algorithm to launch channel estimation, do maximal ratio combining （MRC） and improve signal to interference plus noise ratio （SINR）. The simulation results show that the proposed receiver can go to convergence rapidly under all four IEEE＇s UWB channel models, the bit error ratio （BER） performance is better than that of the traditional receiver and rake receiver.
基金supported by the National Natural Science Fundation of China (60871081)the Research Innovation Fund for College Students of Beijing University of Posts and Telecommunications (2010)the Beijing Natural Science Foundation (Design and Fabrication of Miniature Smart Antenna Based on Metamaterials,4112039)
文摘Two kinds of controllable doped left-handed materials （DLHMs） were designed by inserting inductors and capacitors into the traditional left-handed material （LHM） as heterogeneous elements respectively, which are DLHM with inductors （LDLHM） and DLHM with capacitors （CDLHM）. The characteristics of transmission spectrum were studied by using finite-difference time-domain method （FDTD）. Compared with the traditional LHM, the resonance strength of the LDLHM is weakened and the pass-band is narrowed, but with the increase of the value of the inserted inductors, the bandwidth is expanded. As capacitors inserted into the LHM, the pass-band of the CDLHM is expanded, but the pass-band is shifted to low frequency and the bandwidth is narrowed with the increase of the value of the capacitors, meanwhile, a new generated pass-band is also shifted to low frequency. Therefore, a quantized controllable doped left-handed material can be achieved.
文摘To improve the spectrum sensing performance in cognitive radios, a scheme of cooperative blind spectrum sensing based on autocorrelation matrix is proposed. The test statistic is extracted from the autocorrelation matrix of the received signal samples and a bi-threshold hybrid decision scheme is designed for local spectrum sensing. The cognitive radio base station makes a credibility fusion based on the local soft decisions and then takes global fusion combining with the local hard decisions. The proposed method is blind in the sense since it requires no apriori knowledge of the signal and the noise power. Theoretical analysis and computer simulation results show that the proposed method can enhance the spectrum sensing capability.
