Channel parameters estimation in an orthogonal for the receiver station is a multi-dimensional （MD） frequency division multiple access （OFDMA） system optimization problem, because every user node has a separate lo...Channel parameters estimation in an orthogonal for the receiver station is a multi-dimensional （MD） frequency division multiple access （OFDMA） system optimization problem, because every user node has a separate local oscillator and every transmitter to receiver link has individual carrier frequency offset （CFO） and channel impulse response （CIR） parameters. In order to reduce the computational complexity for MD optimization, a time domain CFOs and CIRs estimation algorithm over the OFDMA based wireless multimedia sensor networks （WMSN） is proposed in this paper. In this algorithm, the receiver station can decouple the signal from every node by correlation based on specially designed training sequences, so that the MD optimization problem is simplified to an 1-D optimal problem. It is proved that the multiple CFOs can be identified from the correlation result using the phase shift of the consecutive training se- quences. Based on the CFOs estimation result, the CIRs can then he estimated according to the minimum mean square error （MMSE） criterion. The theoretic analysis and simulation results show that the proposed algorithm can effectively decouple the signal from different user nodes and the bit error rate （BER） per- formance curves are close to the ideal estimation when the user number is not large.展开更多
Differential modulation was widely used for wireless networks in which channel estimation was diffi-cult.Based on orthogonal design,a novel distributed differential space-time coding/decoding scheme forM-PSK modulatio...Differential modulation was widely used for wireless networks in which channel estimation was diffi-cult.Based on orthogonal design,a novel distributed differential space-time coding/decoding scheme forM-PSK modulations was proposed,which had a high code rate of 2/3 and second-order diversity for thetwo-user cooperative networks.The performance of decode-and-forward (DF) protocols was evaluated.Simulations show that the differential space-time modulation scheme in this paper has better bit error rate(BER) performance or higher code rate than the schemes proposed by Tarasak and Wang when interuserchannel states are good enough.The impacts of transmission error between two users for the whole systemBER performance were also investigated.展开更多
Interference alignment(IA) has been recognized as a promising technique for obtaining the optimal degrees of freedom(DOF) in interference networks.A closed-form interference alignment design is proposed for three-cell...Interference alignment(IA) has been recognized as a promising technique for obtaining the optimal degrees of freedom(DOF) in interference networks.A closed-form interference alignment design is proposed for three-cell uplink transmissions with heterogeneous DOFs.By exploiting the heterogeneity of DOFs from different transmission links,full or partial interference alignment precoders are calculated at each base station(BS).Aided by information exchange among BSs,the precoders can be finally obtained for all transmission links.Comparing to existing IA methods,the proposed scheme has a closed-form expression.Furthermore,there is no need to go through the iterative adaptation or jointly calculate the precoder and the equalizer.Simulation results show that the proposed design is able to achieve the optimal DOF performance with the advantage of perfect alignment capabilities.展开更多
Expression, occlusion, and pose variations are three main challenges for 3D face recognition. A novel method is presented to address 3D face recognition using scale-invariant feature transform(SIFT) features on 3D mes...Expression, occlusion, and pose variations are three main challenges for 3D face recognition. A novel method is presented to address 3D face recognition using scale-invariant feature transform(SIFT) features on 3D meshes. After preprocessing, shape index extrema on the 3D facial surface are selected as keypoints in the difference scale space and the unstable keypoints are removed after two screening steps. Then, a local coordinate system for each keypoint is established by principal component analysis(PCA).Next, two local geometric features are extracted around each keypoint through the local coordinate system. Additionally, the features are augmented by the symmetrization according to the approximate left-right symmetry in human face. The proposed method is evaluated on the Bosphorus, BU-3DFE, and Gavab databases, respectively. Good results are achieved on these three datasets. As a result, the proposed method proves robust to facial expression variations, partial external occlusions and large pose changes.展开更多
The energy efficiency and packet delay tradeoffs in long term evolution-advanced(LTE-A) systems are investigated.Analytical expressions are derived to explain the relation of energy efficiency to mean packet delay,arr...The energy efficiency and packet delay tradeoffs in long term evolution-advanced(LTE-A) systems are investigated.Analytical expressions are derived to explain the relation of energy efficiency to mean packet delay,arrival rate and component carrier(CC) configurations,from the theoretical respective which reveals that the energy efficiency of multiple CC systems is closely related to the frequency of CCs and the number of active CCs.Based on the theoretical analysis,a CC adjusting scheme for LTE-A systems is proposed to maximize energy efficiency subject to delay constraint by dynamically altering the on/off state of CCs according to traffic variations.Numerical and simulation results show that for CCs in different frequency bands with equal transmit power,the proposed scheme could significantly improve the energy efficiency of users in all aggregation levels within the constraint of mean packet delay.展开更多
Multi-objective parameter adjustment plays an important role in improving the performance of the cognitive radio （CR） system. Current research focus on the genetic algorithm （GA） to achieve parameter optimization ...Multi-objective parameter adjustment plays an important role in improving the performance of the cognitive radio （CR） system. Current research focus on the genetic algorithm （GA） to achieve parameter optimization in CR, while general GA always fall into premature convergence. Thereafter, this paper proposed a linear scale transformation to the fitness of individual chromosome, which can reduce the impact of extraordinary individuals exiting in the early evolution iterations, and ensure competition between individuals in the latter evolution iterations. This paper also introduces an adaptive crossover and mutation probability algorithm into parameter adjustment, which can ensure the diversity and convergence of the population. Two applications are applied in the parameter adjustment of CR, one application prefers the bit error rate and another prefers the bandwidth. Simulation results show that the improved parameter adjustment algorithm can converge to the global optimal solution fast without falling into premature convergence.展开更多
Due to the openness of the cognitive radio network, spectrum sensing data falsification （SSDF） can attack the spectrum sensing easily, while there is no effective algorithm proposed in current research work, so this...Due to the openness of the cognitive radio network, spectrum sensing data falsification （SSDF） can attack the spectrum sensing easily, while there is no effective algorithm proposed in current research work, so this paper introduces the malicious users removing to the weight sequential probability radio test （WSPRT）. The terminals＇ weight is weighted by the accuracy of their spectrum sensing information, which can also be used to detect the malicious user. If one terminal owns a low weight, it can be treated as malicious user, and should be removed from the aggregation center. Simulation results show that the improved WSPRT can achieve higher performance compared with the other two conventional sequential detection methods under different number of malicious users.展开更多
It has been shown that transmit correlation causes a signal-to-noise ratio （SNR） loss in the zero forcing （ZF） receiver for V-BLAST （Vertical Bell LAbs LAyered Space-Time） system. In this paper, we investigate t...It has been shown that transmit correlation causes a signal-to-noise ratio （SNR） loss in the zero forcing （ZF） receiver for V-BLAST （Vertical Bell LAbs LAyered Space-Time） system. In this paper, we investigate the transmit correlation effect on the ZF receiver with successive interference cancellation （SIC）. We show that such an unfavorable condition leads to twofold effects on the performance degradation. In addition to the immediate SNR loss, the transmit correlation can increase the propagation factor to spread decision error significantly. These two effects are evaluated analytically. We derive the probability density function （pdf） of the effective SNR at each decoded stream, and hence accurately quantify the SNR loss. We also calculate the decision error propagation factor in terms of its second moment. In particular, we show that transmit correlation can cause a stable component of error propagation which does not decline during the SIC procedure. Finally, we conduct the simulation to verify the analytical results.展开更多
基金supported by the National High Technology Research and Development Programme of China(No.2006AA01Z216)
文摘Channel parameters estimation in an orthogonal for the receiver station is a multi-dimensional （MD） frequency division multiple access （OFDMA） system optimization problem, because every user node has a separate local oscillator and every transmitter to receiver link has individual carrier frequency offset （CFO） and channel impulse response （CIR） parameters. In order to reduce the computational complexity for MD optimization, a time domain CFOs and CIRs estimation algorithm over the OFDMA based wireless multimedia sensor networks （WMSN） is proposed in this paper. In this algorithm, the receiver station can decouple the signal from every node by correlation based on specially designed training sequences, so that the MD optimization problem is simplified to an 1-D optimal problem. It is proved that the multiple CFOs can be identified from the correlation result using the phase shift of the consecutive training se- quences. Based on the CFOs estimation result, the CIRs can then he estimated according to the minimum mean square error （MMSE） criterion. The theoretic analysis and simulation results show that the proposed algorithm can effectively decouple the signal from different user nodes and the bit error rate （BER） per- formance curves are close to the ideal estimation when the user number is not large.
基金the National High Technology Research and Development Programme of China(No.2006AA123320)
文摘Differential modulation was widely used for wireless networks in which channel estimation was diffi-cult.Based on orthogonal design,a novel distributed differential space-time coding/decoding scheme forM-PSK modulations was proposed,which had a high code rate of 2/3 and second-order diversity for thetwo-user cooperative networks.The performance of decode-and-forward (DF) protocols was evaluated.Simulations show that the differential space-time modulation scheme in this paper has better bit error rate(BER) performance or higher code rate than the schemes proposed by Tarasak and Wang when interuserchannel states are good enough.The impacts of transmission error between two users for the whole systemBER performance were also investigated.
基金Supported by the National Natural Science Foundation of China(No.61271285)the National High Technology Research and Development Programme of China(No.2015AA01A703)+2 种基金STCSM Project(No.17ZR1429200)Shanghai Sailing Program(No.16YF1411200)the Leadcore-WiC O Cooperative Project
文摘Interference alignment(IA) has been recognized as a promising technique for obtaining the optimal degrees of freedom(DOF) in interference networks.A closed-form interference alignment design is proposed for three-cell uplink transmissions with heterogeneous DOFs.By exploiting the heterogeneity of DOFs from different transmission links,full or partial interference alignment precoders are calculated at each base station(BS).Aided by information exchange among BSs,the precoders can be finally obtained for all transmission links.Comparing to existing IA methods,the proposed scheme has a closed-form expression.Furthermore,there is no need to go through the iterative adaptation or jointly calculate the precoder and the equalizer.Simulation results show that the proposed design is able to achieve the optimal DOF performance with the advantage of perfect alignment capabilities.
基金Project(XDA06020300)supported by the"Strategic Priority Research Program"of the Chinese Academy of SciencesProject(12511501700)supported by the Research on the Key Technology of Internet of Things for Urban Community Safety Based on Video Sensor networks
文摘Expression, occlusion, and pose variations are three main challenges for 3D face recognition. A novel method is presented to address 3D face recognition using scale-invariant feature transform(SIFT) features on 3D meshes. After preprocessing, shape index extrema on the 3D facial surface are selected as keypoints in the difference scale space and the unstable keypoints are removed after two screening steps. Then, a local coordinate system for each keypoint is established by principal component analysis(PCA).Next, two local geometric features are extracted around each keypoint through the local coordinate system. Additionally, the features are augmented by the symmetrization according to the approximate left-right symmetry in human face. The proposed method is evaluated on the Bosphorus, BU-3DFE, and Gavab databases, respectively. Good results are achieved on these three datasets. As a result, the proposed method proves robust to facial expression variations, partial external occlusions and large pose changes.
基金Supported by the National High Technology Research and Development Program of China(No.2011AA01A109)the National Natural Science Foundation of China(No.61002017,61072076.)the Department of Science and Technology Commission of Shanghai Base Project(No.11DZ2290100)
文摘The energy efficiency and packet delay tradeoffs in long term evolution-advanced(LTE-A) systems are investigated.Analytical expressions are derived to explain the relation of energy efficiency to mean packet delay,arrival rate and component carrier(CC) configurations,from the theoretical respective which reveals that the energy efficiency of multiple CC systems is closely related to the frequency of CCs and the number of active CCs.Based on the theoretical analysis,a CC adjusting scheme for LTE-A systems is proposed to maximize energy efficiency subject to delay constraint by dynamically altering the on/off state of CCs according to traffic variations.Numerical and simulation results show that for CCs in different frequency bands with equal transmit power,the proposed scheme could significantly improve the energy efficiency of users in all aggregation levels within the constraint of mean packet delay.
基金supported by the National Natural Science Foundation of China (61172073)National Key Special Program(2012ZX03003005)+1 种基金the State Key Laboratory of Rail Traffic Control and Safety (RCS2011ZT003)Beijing Jiaotong University and the Fundamental Research Funds for the Central Universities
文摘Multi-objective parameter adjustment plays an important role in improving the performance of the cognitive radio （CR） system. Current research focus on the genetic algorithm （GA） to achieve parameter optimization in CR, while general GA always fall into premature convergence. Thereafter, this paper proposed a linear scale transformation to the fitness of individual chromosome, which can reduce the impact of extraordinary individuals exiting in the early evolution iterations, and ensure competition between individuals in the latter evolution iterations. This paper also introduces an adaptive crossover and mutation probability algorithm into parameter adjustment, which can ensure the diversity and convergence of the population. Two applications are applied in the parameter adjustment of CR, one application prefers the bit error rate and another prefers the bandwidth. Simulation results show that the improved parameter adjustment algorithm can converge to the global optimal solution fast without falling into premature convergence.
基金supported by the National Natural Science Foundation of China(61172073)the State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University(RCS2011ZT003)+2 种基金the Open Research Fund of Key Laboratory of Wireless Sensor Network & Communication,Chinese Academy of Sciences(2011005)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(2013JBZ001,2012YJS129,2009JBM012)the Program for New Century Excellent Talents in University of Ministry of China(NCET-12-0766)
文摘Due to the openness of the cognitive radio network, spectrum sensing data falsification （SSDF） can attack the spectrum sensing easily, while there is no effective algorithm proposed in current research work, so this paper introduces the malicious users removing to the weight sequential probability radio test （WSPRT）. The terminals＇ weight is weighted by the accuracy of their spectrum sensing information, which can also be used to detect the malicious user. If one terminal owns a low weight, it can be treated as malicious user, and should be removed from the aggregation center. Simulation results show that the improved WSPRT can achieve higher performance compared with the other two conventional sequential detection methods under different number of malicious users.
基金Supported in part by Shanghai Research Center for Wireless Communications (SHRCWC) cooperative projectin part by the Ministry of Science and Technology of China (Grant Nos. 2008DFA12190, 2008DFA12090)
文摘It has been shown that transmit correlation causes a signal-to-noise ratio （SNR） loss in the zero forcing （ZF） receiver for V-BLAST （Vertical Bell LAbs LAyered Space-Time） system. In this paper, we investigate the transmit correlation effect on the ZF receiver with successive interference cancellation （SIC）. We show that such an unfavorable condition leads to twofold effects on the performance degradation. In addition to the immediate SNR loss, the transmit correlation can increase the propagation factor to spread decision error significantly. These two effects are evaluated analytically. We derive the probability density function （pdf） of the effective SNR at each decoded stream, and hence accurately quantify the SNR loss. We also calculate the decision error propagation factor in terms of its second moment. In particular, we show that transmit correlation can cause a stable component of error propagation which does not decline during the SIC procedure. Finally, we conduct the simulation to verify the analytical results.
