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2008 Vol. 30, No. 1
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2008, 30(1): 1-5.
doi: 10.3724/SP.J.1146.2007.00780
Abstract:
The biometric technologies for user authentication have been applied widely to identity authentication fields. But at present, the result of research on a biometric authentication system which is used for open networks has not been found. Identity authentication based on X.509 Public Key Infrastructure(PKI) and Privileges Management Infrastructure(PMI) are used widely and effectively in open network fields for authentication and privileges management. So on the basement of PKI and PMI technology, with the function of identity authentication and privileges management, the currency biometric identity authentication system based on Biometric Certificate is introduced. Finally, by designing a highly secure biometric smart card which can realize identity authentication and privileges management, proved the ability and operation of the currency biometric identity authentication system based on PKI and PMI technology.
The biometric technologies for user authentication have been applied widely to identity authentication fields. But at present, the result of research on a biometric authentication system which is used for open networks has not been found. Identity authentication based on X.509 Public Key Infrastructure(PKI) and Privileges Management Infrastructure(PMI) are used widely and effectively in open network fields for authentication and privileges management. So on the basement of PKI and PMI technology, with the function of identity authentication and privileges management, the currency biometric identity authentication system based on Biometric Certificate is introduced. Finally, by designing a highly secure biometric smart card which can realize identity authentication and privileges management, proved the ability and operation of the currency biometric identity authentication system based on PKI and PMI technology.
2008, 30(1): 6-9.
doi: 10.3724/SP.J.1146.2007.00271
Abstract:
It is relatively complex for the existing protocols of WAPI and RSNA of WLAN to run in IBSS networks. There are DoS attacks in their key management procedures. In order to resolve these problems, adopting adaptive selection of entity authentication role and redesigning a new key management protocol, a new wireless access authentication protocol more robust, more efficient and more suitable for IBSS networks is presented. With Canetti-Krawczyk model, this new protocol is analyzed in detail. The analysis results show that it is SK-secure in UM if key encryption algorithm is CCA-secure and the key derivation function is pseudo-random. Finally, based on WAPI, the performance comparison between the new protocol and its original one is made.
It is relatively complex for the existing protocols of WAPI and RSNA of WLAN to run in IBSS networks. There are DoS attacks in their key management procedures. In order to resolve these problems, adopting adaptive selection of entity authentication role and redesigning a new key management protocol, a new wireless access authentication protocol more robust, more efficient and more suitable for IBSS networks is presented. With Canetti-Krawczyk model, this new protocol is analyzed in detail. The analysis results show that it is SK-secure in UM if key encryption algorithm is CCA-secure and the key derivation function is pseudo-random. Finally, based on WAPI, the performance comparison between the new protocol and its original one is made.
2008, 30(1): 10-15.
doi: 10.3724/SP.J.1146.2007.00726
Abstract:
Network routing-based attacks have become more common and the attack consequence can be more serious than other traditional network attacks. Most schemes on improving routing data security are applied to current routing protocols, e.g. digital signature, message authentication and intrusion detection, etc. But very few design guidelines on how to select a secure path to forward confidential user packets. By analyzing the security mechanisms and security threats over network entities, trust degrees of communication links and routers are measured and trust relations are built among network routers. Based on the trust model, a novel SM (Security Metric) is further defined and quantified as the routing criterion used in the proposed security routing algorithm SMRA (Security Metric based Routing Algorithm). Simulation results show that SMRA gets better performance than OSPF in terms of packets delivery ratio and routing security in unsafe networks.
Network routing-based attacks have become more common and the attack consequence can be more serious than other traditional network attacks. Most schemes on improving routing data security are applied to current routing protocols, e.g. digital signature, message authentication and intrusion detection, etc. But very few design guidelines on how to select a secure path to forward confidential user packets. By analyzing the security mechanisms and security threats over network entities, trust degrees of communication links and routers are measured and trust relations are built among network routers. Based on the trust model, a novel SM (Security Metric) is further defined and quantified as the routing criterion used in the proposed security routing algorithm SMRA (Security Metric based Routing Algorithm). Simulation results show that SMRA gets better performance than OSPF in terms of packets delivery ratio and routing security in unsafe networks.
2008, 30(1): 16-20.
doi: 10.3724/SP.J.1146.2006.00958
Abstract:
The maximal achievable multi-rate throughput problem of a multicast session at the presence of network coding is investigated in this paper. Deviating from previous works which focus on single-rate network coding, the heterogeneity of sinks is taken into account and multiple data layers to address the problem is provided in this paper. Firstly formulated is the maximal achievable throughput problem with the assumption that the data layers are independent and layer rates are static. It is proved that the problem in this case is, unfortunately, NP-hard. In addition, the formulation is extended to the problems with dependent layers and dynamic layers. Furthermore, the approximation algorithm which satisfies certain fairness is proposed.
The maximal achievable multi-rate throughput problem of a multicast session at the presence of network coding is investigated in this paper. Deviating from previous works which focus on single-rate network coding, the heterogeneity of sinks is taken into account and multiple data layers to address the problem is provided in this paper. Firstly formulated is the maximal achievable throughput problem with the assumption that the data layers are independent and layer rates are static. It is proved that the problem in this case is, unfortunately, NP-hard. In addition, the formulation is extended to the problems with dependent layers and dynamic layers. Furthermore, the approximation algorithm which satisfies certain fairness is proposed.
2008, 30(1): 21-24.
doi: 10.3724/SP.J.1146.2006.00791
Abstract:
Efficient key management is a difficult issue in secure multicast. In this paper, a novel identity-based key agreement scheme is proposed for multicast groups. Then the procedures of secret communications between subgroups and updating of group keys with the dynamic change of group members are analyzed in detail. The analysis shows that the scheme satisfies the security requirements of key agreement and is efficient in computation and communication.
Efficient key management is a difficult issue in secure multicast. In this paper, a novel identity-based key agreement scheme is proposed for multicast groups. Then the procedures of secret communications between subgroups and updating of group keys with the dynamic change of group members are analyzed in detail. The analysis shows that the scheme satisfies the security requirements of key agreement and is efficient in computation and communication.
2008, 30(1): 25-28.
doi: 10.3724/SP.J.1146.2006.00903
Abstract:
In this paper, ARLNCStream, a novel algorithm of adaptive random linear network coding for media streaming, is presented. When distributing contents using random linear network coding, every node adjusts its coding window in an adaptive way and then requests coded block of an appropriate size from its partners. The solution makes nodes collaborate well with potential partners. Without knowledge of global network topology, ARLNCStream archives quiet low segment missing ratio. ARLNCStream is also robust and scalable. Simulations demonstrate the excellent performance of the solution.
In this paper, ARLNCStream, a novel algorithm of adaptive random linear network coding for media streaming, is presented. When distributing contents using random linear network coding, every node adjusts its coding window in an adaptive way and then requests coded block of an appropriate size from its partners. The solution makes nodes collaborate well with potential partners. Without knowledge of global network topology, ARLNCStream archives quiet low segment missing ratio. ARLNCStream is also robust and scalable. Simulations demonstrate the excellent performance of the solution.
2008, 30(1): 29-32.
doi: 10.3724/SP.J.1146.2006.00949
Abstract:
In wireless sensor networks, one of the most significant traffic pattern is data gathering from sensor nodes to sink through multi-hop data-delivery tree. For such pattern, this paper presents EBRI-MAC(Energy-efficient MAC protocol Based on Routing Information), in which the idea of a parent node and its child nodes forming a virtual cluster based on the data-delivery tree is introduced, and a medium access mechanism of a chain-invitation combined CSMA/CA and a period sleep mechanism of synchronization within each virtual cluster are designed in order to save energy. Considering the major sources of energy waste, a performance parameter is defined to evaluate energy-efficient, and theoretical analysis is performed. With ns-2 simulation results，it is verified that EBRI-MAC can win better energy-efficient performance than IEEE802.11 DCF and S-MAC under the traffic pattern of each node being time-correlated.
In wireless sensor networks, one of the most significant traffic pattern is data gathering from sensor nodes to sink through multi-hop data-delivery tree. For such pattern, this paper presents EBRI-MAC(Energy-efficient MAC protocol Based on Routing Information), in which the idea of a parent node and its child nodes forming a virtual cluster based on the data-delivery tree is introduced, and a medium access mechanism of a chain-invitation combined CSMA/CA and a period sleep mechanism of synchronization within each virtual cluster are designed in order to save energy. Considering the major sources of energy waste, a performance parameter is defined to evaluate energy-efficient, and theoretical analysis is performed. With ns-2 simulation results，it is verified that EBRI-MAC can win better energy-efficient performance than IEEE802.11 DCF and S-MAC under the traffic pattern of each node being time-correlated.
2008, 30(1): 33-37.
doi: 10.3724/SP.J.1146.2006.00758
Abstract:
User profiles, descriptions of user interests, can be used by search engines to provide personalized search results. A query optimization method based on user profiles reasoning is presented. This method creates user profiles by classifying users interests into instances in an ontology knowledge base, and then propagates user preferences to find users latent interests by analyzing the semantic association among the ontology instances. It integrates users current and history preferences to process the search results. A prototype system is implemented and the experimental results show that users latent preferences can be learned accurately and personalized search based on user preference yields significant improvements over the origin results.
User profiles, descriptions of user interests, can be used by search engines to provide personalized search results. A query optimization method based on user profiles reasoning is presented. This method creates user profiles by classifying users interests into instances in an ontology knowledge base, and then propagates user preferences to find users latent interests by analyzing the semantic association among the ontology instances. It integrates users current and history preferences to process the search results. A prototype system is implemented and the experimental results show that users latent preferences can be learned accurately and personalized search based on user preference yields significant improvements over the origin results.
2008, 30(1): 38-43.
doi: 10.3724/SP.J.1146.2006.00774
Abstract:
This paper addresses the problem of parameters estimation and signal detection for OFDMA Uplink. Firstly, a transmit signal frame structure for OFDMA uplink is designed, the preamble of frame structure consists of PN sequence. Secondly, the carrier frequency offset and channel estimation algorithm based on PN sequence are proposed, also a time minimum-mean-squre-error signal detection algorithm is proposed for OFDMA uplink. Simulation results demonstrate the carrier frequency offset and channel estimation algorithm can get more accurate parameters estimation because of correlation of PN sequence, meanwhile it is immune to the noise and adapts to the fading channel, the time minimum-mean-squre-error signal detection algorithm can provide better bit error rate performance.
This paper addresses the problem of parameters estimation and signal detection for OFDMA Uplink. Firstly, a transmit signal frame structure for OFDMA uplink is designed, the preamble of frame structure consists of PN sequence. Secondly, the carrier frequency offset and channel estimation algorithm based on PN sequence are proposed, also a time minimum-mean-squre-error signal detection algorithm is proposed for OFDMA uplink. Simulation results demonstrate the carrier frequency offset and channel estimation algorithm can get more accurate parameters estimation because of correlation of PN sequence, meanwhile it is immune to the noise and adapts to the fading channel, the time minimum-mean-squre-error signal detection algorithm can provide better bit error rate performance.
2008, 30(1): 44-47.
doi: 10.3724/SP.J.1146.2006.00836
Abstract:
An improved symbol synchronization algorithm for OFDM systems is proposed in this paper. Based on the assemble correlation method which estimates the available sampling window for FFT, the recovered binary serial is modulated for the second time. By computing the correlation of received signal and the twice modulated signal, the correct symbol timing is obtained. This data-aided method increases the SNR during the estimation. Simulation results demonstrate that the proposed algorithm has good timing synchronization performance over multi-path fading channel.
An improved symbol synchronization algorithm for OFDM systems is proposed in this paper. Based on the assemble correlation method which estimates the available sampling window for FFT, the recovered binary serial is modulated for the second time. By computing the correlation of received signal and the twice modulated signal, the correct symbol timing is obtained. This data-aided method increases the SNR during the estimation. Simulation results demonstrate that the proposed algorithm has good timing synchronization performance over multi-path fading channel.
2008, 30(1): 48-51.
doi: 10.3724/SP.J.1146.2006.00864
Abstract:
In order to improve the system performance and reduce hardware complexity further, a new transmit diversity scheme, Minimum-selection Maximum Ratio Transmit (MMRT) scheme is proposed. Based on the theory on random matrix and order statistics, an exact analysis for MMRT is carried out. The closed-form outage probability and the Bit Error Rate (BER) of the MMRT system, for Rayleigh fading scenario, are presented. The analytical results are verified by simulation.
In order to improve the system performance and reduce hardware complexity further, a new transmit diversity scheme, Minimum-selection Maximum Ratio Transmit (MMRT) scheme is proposed. Based on the theory on random matrix and order statistics, an exact analysis for MMRT is carried out. The closed-form outage probability and the Bit Error Rate (BER) of the MMRT system, for Rayleigh fading scenario, are presented. The analytical results are verified by simulation.
2008, 30(1): 52-54.
doi: 10.3724/SP.J.1146.2006.00768
Abstract:
The traditional Vertical-Bell Laboratory layered Space-Time(V-BLAST) systems adopt an Ordered Decision-Feedback(ODF) detection strategy, which can significantly outperform the liner detector, however, it increases the computational complexity. Based on the conception of segmented detection, an improved noise-predictive Partial Decision-Feedback(PDF)detector is proposed, it introduces the MMSE principle and divides the receive signals into two segments. Since only feeding back the decision once, the MMSE-PDF detector reduces complexity significantly compared to the conventional ODF detector. The simulation results show that in the condition of SUI-3 channel model, 2 transmission antennas and 4 receive antennas, in the level, compared with the complicated V-BLAST system, the novel receiver only suffers 0.6dB loss, however, it 10-4has more or less 2~3 dB performance gains compared with the linear and other improved receiver based on the MMSE principle.
The traditional Vertical-Bell Laboratory layered Space-Time(V-BLAST) systems adopt an Ordered Decision-Feedback(ODF) detection strategy, which can significantly outperform the liner detector, however, it increases the computational complexity. Based on the conception of segmented detection, an improved noise-predictive Partial Decision-Feedback(PDF)detector is proposed, it introduces the MMSE principle and divides the receive signals into two segments. Since only feeding back the decision once, the MMSE-PDF detector reduces complexity significantly compared to the conventional ODF detector. The simulation results show that in the condition of SUI-3 channel model, 2 transmission antennas and 4 receive antennas, in the level, compared with the complicated V-BLAST system, the novel receiver only suffers 0.6dB loss, however, it 10-4has more or less 2~3 dB performance gains compared with the linear and other improved receiver based on the MMSE principle.
2008, 30(1): 55-58.
doi: 10.3724/SP.J.1146.2006.01698
Abstract:
In the Space-Time-Frequency(STF) coded MIMO-OFDM system, dividing the subchannels into groups of less correlated subchannels and applying STF coding to group STF(GSTF) subsystems, this paper proposes novel the optimal training design for GSTF systems where one group is assigned for training and others groups are for data, and the channel estimation based on the optimal training sequence is extended into Space-Time-Frequency dimensions with considering the time dimension. Theoretical analysis and numerical results show that the scheme gives distinct improvements in the channel estimates on frequency-selective fading channels with low coding and decoding complexity.
In the Space-Time-Frequency(STF) coded MIMO-OFDM system, dividing the subchannels into groups of less correlated subchannels and applying STF coding to group STF(GSTF) subsystems, this paper proposes novel the optimal training design for GSTF systems where one group is assigned for training and others groups are for data, and the channel estimation based on the optimal training sequence is extended into Space-Time-Frequency dimensions with considering the time dimension. Theoretical analysis and numerical results show that the scheme gives distinct improvements in the channel estimates on frequency-selective fading channels with low coding and decoding complexity.
2008, 30(1): 59-62.
doi: 10.3724/SP.J.1146.2006.00410
Abstract:
Aiming at the discrepancies of the Signal-to-Interference Ratio (SIR) among different users in Cognitive Radios (CR), a Nash game algorithm for SIR-based power control was adopted and a novel adaptive algorithm was designed based on a Space-Time Block Coding MC-CDMA (STBC MC-CDMA) system. Simulation results show that the novel algorithm can regulate their transmitter powers to meet the different SIR requirements effectively and the anti-interference performance of CR system is improved obviously.
Aiming at the discrepancies of the Signal-to-Interference Ratio (SIR) among different users in Cognitive Radios (CR), a Nash game algorithm for SIR-based power control was adopted and a novel adaptive algorithm was designed based on a Space-Time Block Coding MC-CDMA (STBC MC-CDMA) system. Simulation results show that the novel algorithm can regulate their transmitter powers to meet the different SIR requirements effectively and the anti-interference performance of CR system is improved obviously.
2008, 30(1): 63-66.
doi: 10.3724/SP.J.1146.2006.00812
Abstract:
MIMO/OFDM is an effective architecture for future wireless communication systems. A spatial subchannel allocation algorithm based on mean feedback model over multiuser MIMO/OFDM systems is proposed in this paper. With the goal of maximizing overall data throughput the criteria of subcarrier allocation is derived and the adaptive allocation approach is developed. The simulation results show that the proposed algorithm can efficiently achieve good performance and high total transmission rate.
MIMO/OFDM is an effective architecture for future wireless communication systems. A spatial subchannel allocation algorithm based on mean feedback model over multiuser MIMO/OFDM systems is proposed in this paper. With the goal of maximizing overall data throughput the criteria of subcarrier allocation is derived and the adaptive allocation approach is developed. The simulation results show that the proposed algorithm can efficiently achieve good performance and high total transmission rate.
2008, 30(1): 67-71.
doi: 10.3724/SP.J.1146.2006.00822
Abstract:
Three new merged-reconstruction-based Inter-Layer Inter-Satellite Link(ILISL) establishment strategies are proposed to reduce the number of network topology reconfiguration and enhance the topology structure stability of the two-tier Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite networks. These proposed strategies decrease the number of the network topology reconfiguration by forcing reconstruction of all ILISL at the same time. Simulation results show that the number of the network topology reconfiguration can be reduced greatly with proposed strategies. Hence the topological stability of the LEO/MEO two-tier satellite networks can be improved with acceptable cost.
Three new merged-reconstruction-based Inter-Layer Inter-Satellite Link(ILISL) establishment strategies are proposed to reduce the number of network topology reconfiguration and enhance the topology structure stability of the two-tier Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite networks. These proposed strategies decrease the number of the network topology reconfiguration by forcing reconstruction of all ILISL at the same time. Simulation results show that the number of the network topology reconfiguration can be reduced greatly with proposed strategies. Hence the topological stability of the LEO/MEO two-tier satellite networks can be improved with acceptable cost.
2008, 30(1): 72-76.
doi: 10.3724/SP.J.1146.2006.00897
Abstract:
In this paper a coverage scheme consisting of both fixed and configurable beams is proposed for HAPS WCDMA systems. According to different user distribution, the system capacity is optimized by embedding configurable beams in fixed beams rationally and adjusting the position and size of them efficiently. The numerical results show that a higher and more stable system capacity is expectable despite variation of user distribution, and large number of beams are also economized. This good performance especially appears in solving the problem of the hot spot in communication.
In this paper a coverage scheme consisting of both fixed and configurable beams is proposed for HAPS WCDMA systems. According to different user distribution, the system capacity is optimized by embedding configurable beams in fixed beams rationally and adjusting the position and size of them efficiently. The numerical results show that a higher and more stable system capacity is expectable despite variation of user distribution, and large number of beams are also economized. This good performance especially appears in solving the problem of the hot spot in communication.
2008, 30(1): 77-80.
doi: 10.3724/SP.J.1146.2006.00778
Abstract:
This paper proposes a blind adaptive receive technique in asynchronous multipath CDMA systems based on the Pre-Processing Recursive Least Squares Constant Modulus Algorithm (PP-RLSCMA) .The received signals are adaptively pre-processed first ,and analysis of the complexity and stability of the pre-processor is provided. The pre-processor enhances the performance of CMA_based receiver by partly suppressing the interference and noise and the proposed method is only dependent on parameter of maximum multipath length. Because of slow convergence rate of statistic descend constant modulus, the paper presents a blind adaptive receiver based on fast (RLSCMA). Simulation indicates that the proposed algorithm has a better performance of BER and convergence compared with LCMMV and LCCMA.
This paper proposes a blind adaptive receive technique in asynchronous multipath CDMA systems based on the Pre-Processing Recursive Least Squares Constant Modulus Algorithm (PP-RLSCMA) .The received signals are adaptively pre-processed first ,and analysis of the complexity and stability of the pre-processor is provided. The pre-processor enhances the performance of CMA_based receiver by partly suppressing the interference and noise and the proposed method is only dependent on parameter of maximum multipath length. Because of slow convergence rate of statistic descend constant modulus, the paper presents a blind adaptive receiver based on fast (RLSCMA). Simulation indicates that the proposed algorithm has a better performance of BER and convergence compared with LCMMV and LCCMA.
2008, 30(1): 81-85.
doi: 10.3724/SP.J.1146.2006.00766
Abstract:
Focusing on the spatial multiplexing multiuser Multiple-Input Multiple-Output (MIMO) downlink, this paper studies the influence of the spatial fading correlation and the channel estimation error on the system capacity. Two novel grouped multiuser diversity schemes are proposed. The proposed schemes can effectively increase the system capacity by rightly selecting the co-channel users, and can provide a good fairness performance. Both analysis and simulation results show that the schemes are robust for the fading correlation and channel estimation errors. The second scheme can further increase the system capacity compared with the first one, but possesses higher computational complexity.
Focusing on the spatial multiplexing multiuser Multiple-Input Multiple-Output (MIMO) downlink, this paper studies the influence of the spatial fading correlation and the channel estimation error on the system capacity. Two novel grouped multiuser diversity schemes are proposed. The proposed schemes can effectively increase the system capacity by rightly selecting the co-channel users, and can provide a good fairness performance. Both analysis and simulation results show that the schemes are robust for the fading correlation and channel estimation errors. The second scheme can further increase the system capacity compared with the first one, but possesses higher computational complexity.
2008, 30(1): 86-88.
doi: 10.3724/SP.J.1146.2006.00805
Abstract:
In direct sequence spread spectrum narrow-band interference suppression is one of the difficult tasks in signal processing. This paper proposes a new narrow-band interference suppression algorithm called side correlation replacement algorithm based on side band correlation of signal. The signal carrier and center frequency of narrow interference are fixed on by calculating the side correlation function. Then narrow-band interference is eliminated when it is replaced by side correlation value. This algorithm is good for all modulation whose spectrum is symmetry. Computer simulation results demonstrate that the algorithm is more effective than transform domain interference returns zero.
In direct sequence spread spectrum narrow-band interference suppression is one of the difficult tasks in signal processing. This paper proposes a new narrow-band interference suppression algorithm called side correlation replacement algorithm based on side band correlation of signal. The signal carrier and center frequency of narrow interference are fixed on by calculating the side correlation function. Then narrow-band interference is eliminated when it is replaced by side correlation value. This algorithm is good for all modulation whose spectrum is symmetry. Computer simulation results demonstrate that the algorithm is more effective than transform domain interference returns zero.
2008, 30(1): 89-92.
doi: 10.3724/SP.J.1146.2006.00847
Abstract:
This paper addresses the issue of chaotic communication with Particle Filter (PF). Combining with the modeling technique for signal, a filtering method based on the particle filter is proposed. Communication is accomplished by using additive chaos masking scheme or multiplicative chaos masking scheme in the transmitter, and message symbols are estimated in the receiver. Simulation results demonstrate that when message symbols are binary codes and M-ary codes, two kinds of chaos masking schemes based on the particle filtering method can perform effectively communication with chaos for retrieving the message signals from the noisy contaminated chaotic signals. In comparison with the UKF-based method, PF-based method has a lower Bit Error Rate (BER). In addition, compared with multiplicative chaos masking scheme, the additive chaos masking scheme based on the particle filtering has a lower bit error rate performance, which is close to ideal BPSK.
This paper addresses the issue of chaotic communication with Particle Filter (PF). Combining with the modeling technique for signal, a filtering method based on the particle filter is proposed. Communication is accomplished by using additive chaos masking scheme or multiplicative chaos masking scheme in the transmitter, and message symbols are estimated in the receiver. Simulation results demonstrate that when message symbols are binary codes and M-ary codes, two kinds of chaos masking schemes based on the particle filtering method can perform effectively communication with chaos for retrieving the message signals from the noisy contaminated chaotic signals. In comparison with the UKF-based method, PF-based method has a lower Bit Error Rate (BER). In addition, compared with multiplicative chaos masking scheme, the additive chaos masking scheme based on the particle filtering has a lower bit error rate performance, which is close to ideal BPSK.
2008, 30(1): 93-95.
doi: 10.3724/SP.J.1146.2006.00838
Abstract:
In this paper，the CARTESIAN authentication codes based on sets and orthogonal arrays are constructed and the property of the codes are analyzed. Some known construction methods of CARTESIAN authentication codes with the same parameters can be treated as the special examples of the method proposed in the paper.
In this paper，the CARTESIAN authentication codes based on sets and orthogonal arrays are constructed and the property of the codes are analyzed. Some known construction methods of CARTESIAN authentication codes with the same parameters can be treated as the special examples of the method proposed in the paper.
2008, 30(1): 96-99.
doi: 10.3724/SP.J.1146.2006.00902
Abstract:
This paper proposes a new method to get time solutions of periodic orbits and to determine their stability for piecewise linear dynamic systems. The state space of piecewise linear dynamic system is cut into some linear subspaces by several switching surfaces. By solving together all the equations of periodic orbit in these subspaces with MATLAB, the coordinates of periodic orbit on each switching surface and the running time on each subspace are obtained, from which the time expressions in sections of periodic orbit can be derived. Based on these expressions, the Poincare mapping equation and the Jacobian matrix of periodic orbits can be deduced. According to the eigenvalues of the Jacobian matrix, the stability of the periodic orbit can be determined. Using 3rd-order and 4th-order Chaus circuits as examples, the time expressions of many periodic orbits are obtained and their stability is determined respectively by the new method. The results are exact the same as that of digital simulations, which shows the new method is correct and practical.
This paper proposes a new method to get time solutions of periodic orbits and to determine their stability for piecewise linear dynamic systems. The state space of piecewise linear dynamic system is cut into some linear subspaces by several switching surfaces. By solving together all the equations of periodic orbit in these subspaces with MATLAB, the coordinates of periodic orbit on each switching surface and the running time on each subspace are obtained, from which the time expressions in sections of periodic orbit can be derived. Based on these expressions, the Poincare mapping equation and the Jacobian matrix of periodic orbits can be deduced. According to the eigenvalues of the Jacobian matrix, the stability of the periodic orbit can be determined. Using 3rd-order and 4th-order Chaus circuits as examples, the time expressions of many periodic orbits are obtained and their stability is determined respectively by the new method. The results are exact the same as that of digital simulations, which shows the new method is correct and practical.
2008, 30(1): 100-103.
doi: 10.3724/SP.J.1146.2006.01218
Abstract:
In TAMC' 06, Bao et al. proposed a new identity-based threshold proxy signature with known signers from the bilinear pairings (denoted as BCW scheme) for the first time. As for the security, they claimed their scheme satisfies the security requirements of proxy signature such as strong unforgeability and their scheme need not the secure channel for the delivery of the signed warrant and etc.. In this paper, however, an attack against their scheme is presented. That is, based on the proxy signature generated by proxy signers on a message on behalf of an original signer, an attacker can forge a valid threshold proxy signature on the same message which seemed generated by proxy signers on behalf of this attacker himself. After production a forged proxy signature, the attacker has the same authority with the original signer to the proxy signer, and the verifier cannot distinguish that which one is the real original signer. To thwart this attack, an improvement measure is further proposed, which can resolve the security problem existing in this scheme.
In TAMC' 06, Bao et al. proposed a new identity-based threshold proxy signature with known signers from the bilinear pairings (denoted as BCW scheme) for the first time. As for the security, they claimed their scheme satisfies the security requirements of proxy signature such as strong unforgeability and their scheme need not the secure channel for the delivery of the signed warrant and etc.. In this paper, however, an attack against their scheme is presented. That is, based on the proxy signature generated by proxy signers on a message on behalf of an original signer, an attacker can forge a valid threshold proxy signature on the same message which seemed generated by proxy signers on behalf of this attacker himself. After production a forged proxy signature, the attacker has the same authority with the original signer to the proxy signer, and the verifier cannot distinguish that which one is the real original signer. To thwart this attack, an improvement measure is further proposed, which can resolve the security problem existing in this scheme.
2008, 30(1): 104-106.
doi: 10.3724/SP.J.1146.2006.00819
Abstract:
This paper presents a new method for constructing two-dimensional perfect supplementary quaternary array by using of the properties of the two-dimensional perfect supplementary quaternary array and twodimension -al quasiperfect supplementary quaternary array. As an application, a new two-dimensional perfect supplementary quaternary array with the sizes of 4s t and the sizes of 2s 2t are constructed by a perfect supplementary array with the sizes of s t and a quasiperfect supplementary array with the sizes of 2st.
This paper presents a new method for constructing two-dimensional perfect supplementary quaternary array by using of the properties of the two-dimensional perfect supplementary quaternary array and twodimension -al quasiperfect supplementary quaternary array. As an application, a new two-dimensional perfect supplementary quaternary array with the sizes of 4s t and the sizes of 2s 2t are constructed by a perfect supplementary array with the sizes of s t and a quasiperfect supplementary array with the sizes of 2st.
2008, 30(1): 107-110.
doi: 10.3724/SP.J.1146.2007.00338
Abstract:
In coding theory, it is important to study a code and the structure of codewords. In this paper, the width of a codeword on the finite ring Z4 is defined which is a new mathematical character of a codeword. A number of properties on the width of codewords are presented, and two recursive algorithms for computing the width of a codeword on the finite ring Z4 are given. Finally, the relationship between the width and depth of a codeword over the ring Z4 is preliminary discussed.
In coding theory, it is important to study a code and the structure of codewords. In this paper, the width of a codeword on the finite ring Z4 is defined which is a new mathematical character of a codeword. A number of properties on the width of codewords are presented, and two recursive algorithms for computing the width of a codeword on the finite ring Z4 are given. Finally, the relationship between the width and depth of a codeword over the ring Z4 is preliminary discussed.
2008, 30(1): 111-113.
doi: 10.3724/SP.J.1146.2006.01920
Abstract:
The uniqueness of Low Correlation Zone(LCZ) sequence pairs is put forward and proved. And, the uniqueness of Zero Correlation Zone(ZCZ) sequence pairs and Almost Perfect Autocorrelation Sequence Pairs(APASP) are proved as the specific cases of LCZ sequence pairs. The unique receiving is guaranteed in theory, when the sequence pairs mentioned above are applied.
The uniqueness of Low Correlation Zone(LCZ) sequence pairs is put forward and proved. And, the uniqueness of Zero Correlation Zone(ZCZ) sequence pairs and Almost Perfect Autocorrelation Sequence Pairs(APASP) are proved as the specific cases of LCZ sequence pairs. The unique receiving is guaranteed in theory, when the sequence pairs mentioned above are applied.
2008, 30(1): 114-116.
doi: 10.3724/SP.J.1146.2006.00938
Abstract:
A receiver structure of M-ary Differential Phase-Shift Keying (MDPSK) concatenated with Low-Density Parity Check Codes in flat Rayleigh fading channels is proposed. An iterative hard decision-feedback detection algorithm also is analyzed ignorant of channel state information. Compared with conventional differential demodulation decoding one, this algorithm almost has no increasing in complexity and simulation results also confirm that it has 2.2dB gain at BER of 10-4 when iterative four times.
A receiver structure of M-ary Differential Phase-Shift Keying (MDPSK) concatenated with Low-Density Parity Check Codes in flat Rayleigh fading channels is proposed. An iterative hard decision-feedback detection algorithm also is analyzed ignorant of channel state information. Compared with conventional differential demodulation decoding one, this algorithm almost has no increasing in complexity and simulation results also confirm that it has 2.2dB gain at BER of 10-4 when iterative four times.
2008, 30(1): 117-120.
doi: 10.3724/SP.J.1146.2006.00803
Abstract:
A non-singleton fuzzy support vector machine-based decision feedback equalizer (NSFSVM DFE) is proposed in this paper for severely nonlinear distorted channels with burst jamming. The method adopted non-singleton fuzzy Gauss kernel function with preceding filtering capability of which the tunable parameter is adjusted by gradient-descent algorithm. Simulation is carried out to compare it with other nonlinear channel equalizers. The result shows the method has much better performance on nonlinear equalization and anti-burst jamming.
A non-singleton fuzzy support vector machine-based decision feedback equalizer (NSFSVM DFE) is proposed in this paper for severely nonlinear distorted channels with burst jamming. The method adopted non-singleton fuzzy Gauss kernel function with preceding filtering capability of which the tunable parameter is adjusted by gradient-descent algorithm. Simulation is carried out to compare it with other nonlinear channel equalizers. The result shows the method has much better performance on nonlinear equalization and anti-burst jamming.
2008, 30(1): 121-124.
doi: 10.3724/SP.J.1146.2006.00634
Abstract:
An improved adaptive filtering algorithm is proposed in this paper, and the convergence of the algorithm is analyzed. As an example, the new algorithm is used to cancel echo for the chaotic modulation communication systems experiencing echo channels. The results by computer simulation indicate that the improved algorithm has faster convergence speed and higher accuracy of computation. In addition, the new algorithm is steadier in the case of low SNR.
An improved adaptive filtering algorithm is proposed in this paper, and the convergence of the algorithm is analyzed. As an example, the new algorithm is used to cancel echo for the chaotic modulation communication systems experiencing echo channels. The results by computer simulation indicate that the improved algorithm has faster convergence speed and higher accuracy of computation. In addition, the new algorithm is steadier in the case of low SNR.
2008, 30(1): 125-129.
doi: 10.3724/SP.J.1146.2006.00880
Abstract:
The effects of both symbol synchronization error and SNR estimation on the LDPC decoding performance are investigated. Based on the statistical properties of the LDPC decoding output value, a joint timing recovery and SNR estimation algorithm is given, which puts the symbol synchronization, SNR estimation and iterative decoding together by two cooperative loops. After several iterative steps, the estimated values of symbol synchronization error and SNR convergent rapidly, and little performance degradation is observed than the system with foregone SNR and accurate symbol timing.
The effects of both symbol synchronization error and SNR estimation on the LDPC decoding performance are investigated. Based on the statistical properties of the LDPC decoding output value, a joint timing recovery and SNR estimation algorithm is given, which puts the symbol synchronization, SNR estimation and iterative decoding together by two cooperative loops. After several iterative steps, the estimated values of symbol synchronization error and SNR convergent rapidly, and little performance degradation is observed than the system with foregone SNR and accurate symbol timing.
2008, 30(1): 130-133.
doi: 10.3724/SP.J.1146.2006.00939
Abstract:
A new ESPRIT-like method is presented to estimate the Direction-Of-Arrival (DOA) of non-circular sources. The basic idea of the real-value algorithm is to use the non-circular sources property of the received signals to get the sine and cosine data. Because the new data are the real-valued sine and cosine data respectively, the proposed algorithm can double the length of data by concatenating the sine and cosine data in tandem, as a result it can improve the performance of the DOA estimation and can resolve two times the number of directions when compared to those conventional ESPRIT-like estimators. More importantly, the computational complexity is reduced in the eigennalysis stage, because it exploits the eigencomposition of a real-valued covariance matrix. The simulation results show that the proposed method is superior in resolving noncoherent signal.
A new ESPRIT-like method is presented to estimate the Direction-Of-Arrival (DOA) of non-circular sources. The basic idea of the real-value algorithm is to use the non-circular sources property of the received signals to get the sine and cosine data. Because the new data are the real-valued sine and cosine data respectively, the proposed algorithm can double the length of data by concatenating the sine and cosine data in tandem, as a result it can improve the performance of the DOA estimation and can resolve two times the number of directions when compared to those conventional ESPRIT-like estimators. More importantly, the computational complexity is reduced in the eigennalysis stage, because it exploits the eigencomposition of a real-valued covariance matrix. The simulation results show that the proposed method is superior in resolving noncoherent signal.
2008, 30(1): 134-138.
doi: 10.3724/SP.J.1146.2006.00721
Abstract:
Based on cyclostationarity of digital modulated signals, many blind signal processing applications can be completed. But the cyclic spectrum structure of signals must be known in premise. Based on Linear Periodically Time-Variant transformation (LPTV) model and aperiodic homogeneous Markov chain model, the Spectral Correlation Density (SCD) expression of OFDM signals is derived. The magnitudes of cyclic spectrum are graphed as the heights of surfaces above a bifrequency plane. Computer simulation results confirm theoretical analysis.
Based on cyclostationarity of digital modulated signals, many blind signal processing applications can be completed. But the cyclic spectrum structure of signals must be known in premise. Based on Linear Periodically Time-Variant transformation (LPTV) model and aperiodic homogeneous Markov chain model, the Spectral Correlation Density (SCD) expression of OFDM signals is derived. The magnitudes of cyclic spectrum are graphed as the heights of surfaces above a bifrequency plane. Computer simulation results confirm theoretical analysis.
2008, 30(1): 139-143.
doi: 10.3724/SP.J.1146.2006.00831
Abstract:
In many applications subband adaptive filter structures have been shown to be superior computationally and performancewise. This paper presents a subband Direct Matrix Inversion (DMI) algorithm suitable for use within a recently proposed adaptive filter structure employing critically sampled filter banks. This new method reduces the computational complexity by using the block tridiagonal structure of the input sample correlation matrix, and at the same time keeps the advantage of fast convergence. Experimental results show that the output residue power of the subband DMI algorithm is around 3dB upon the optimum value after only 2K updating of the adaptive subfilters, where K is the dimension of the adaptive subfilters.
In many applications subband adaptive filter structures have been shown to be superior computationally and performancewise. This paper presents a subband Direct Matrix Inversion (DMI) algorithm suitable for use within a recently proposed adaptive filter structure employing critically sampled filter banks. This new method reduces the computational complexity by using the block tridiagonal structure of the input sample correlation matrix, and at the same time keeps the advantage of fast convergence. Experimental results show that the output residue power of the subband DMI algorithm is around 3dB upon the optimum value after only 2K updating of the adaptive subfilters, where K is the dimension of the adaptive subfilters.
2008, 30(1): 144-148.
doi: 10.3724/SP.J.1146.2006.00878
Abstract:
In this paper, a novel two-layer constraint image interpolation model is proposed. The novel model interpolates image under the constraint of gradient magnitude in original un-interpolated image. The edge pixel is processed by Partial Differential Equation (PDE). PDE enhances edge and smoothes jaggies in the edge. The pixel in smooth regions of under-interpolated image is processed by Non Local (NL)-means model. NL-means model gets gray value of pixel by weighted averaging global information in image and image is smoothed. Texture image interpolated by the novel model preserves the entire texture pattern; the jaggies in linear structure of texture is smoothed too. It is even proved by theory and experiments that noisy image can be interpolated directly to the required size using this novel model.
In this paper, a novel two-layer constraint image interpolation model is proposed. The novel model interpolates image under the constraint of gradient magnitude in original un-interpolated image. The edge pixel is processed by Partial Differential Equation (PDE). PDE enhances edge and smoothes jaggies in the edge. The pixel in smooth regions of under-interpolated image is processed by Non Local (NL)-means model. NL-means model gets gray value of pixel by weighted averaging global information in image and image is smoothed. Texture image interpolated by the novel model preserves the entire texture pattern; the jaggies in linear structure of texture is smoothed too. It is even proved by theory and experiments that noisy image can be interpolated directly to the required size using this novel model.
2008, 30(1): 149-153.
doi: 10.3724/SP.J.1146.2006.00849
Abstract:
In this paper, a method is proposed which uses the Radial Basis Function (RBF) to improve the Bidimensional Empirical Mode Decomposition (BEMD). The mirror compactly supported RBF not only has the precision of interpolation and suppresses the boundary effect, but also has fast computation. Experiments indicate that the method in this paper can gain better decompositions.
In this paper, a method is proposed which uses the Radial Basis Function (RBF) to improve the Bidimensional Empirical Mode Decomposition (BEMD). The mirror compactly supported RBF not only has the precision of interpolation and suppresses the boundary effect, but also has fast computation. Experiments indicate that the method in this paper can gain better decompositions.
2008, 30(1): 154-158.
doi: 10.3724/SP.J.1146.2007.00146
Abstract:
A method is proposed to obtain individual Head Related Transfer Function (HRTF) based on the Partial Least Square Regression (PLSR), in which anthropometric parameters are selected by correlation analysis and the original HRTF data are preprocessed before principal component analysis. Then objective simulation experiment and subjective sound localization experiment are implemented to evaluate the method. The experiments show that the estimated HRTF not only has small mean square error, but also has little perception difference from the measured one；the localization performance of the individual HRTF estimated by PLSR presented in this article is more accurate than that of the non-individual HRTF obtained from the database and also more accurate than that estimated via Least Square Regression (LSR).
A method is proposed to obtain individual Head Related Transfer Function (HRTF) based on the Partial Least Square Regression (PLSR), in which anthropometric parameters are selected by correlation analysis and the original HRTF data are preprocessed before principal component analysis. Then objective simulation experiment and subjective sound localization experiment are implemented to evaluate the method. The experiments show that the estimated HRTF not only has small mean square error, but also has little perception difference from the measured one；the localization performance of the individual HRTF estimated by PLSR presented in this article is more accurate than that of the non-individual HRTF obtained from the database and also more accurate than that estimated via Least Square Regression (LSR).
2008, 30(1): 159-162.
doi: 10.3724/SP.J.1146.2006.00940
Abstract:
When fusing the decisions of local sensors transmitted via Nakagami fading channel, the Likelihood ratio test based on channel statistics (LRT-CS) proposed in the literature requires the detection probability of local sensors and involves an infinity series. However, the detection probability of local sensors generally is a priori unknown for an uncooperative target. Thus, a Censoring based Mixed Fusion (CMF) is proposed, which is simple and does not need the detection probability of local sensors. Monte Carlo simulations show that the CMF has small performance degradation in comparison with the LRT-CS for unknown detection probabilities of local sensors. Therefore, CMF can substitute LRT-CS in practice.
When fusing the decisions of local sensors transmitted via Nakagami fading channel, the Likelihood ratio test based on channel statistics (LRT-CS) proposed in the literature requires the detection probability of local sensors and involves an infinity series. However, the detection probability of local sensors generally is a priori unknown for an uncooperative target. Thus, a Censoring based Mixed Fusion (CMF) is proposed, which is simple and does not need the detection probability of local sensors. Monte Carlo simulations show that the CMF has small performance degradation in comparison with the LRT-CS for unknown detection probabilities of local sensors. Therefore, CMF can substitute LRT-CS in practice.
2008, 30(1): 163-167.
doi: 10.3724/SP.J.1146.2006.00424
Abstract:
Based on the modeling methods with the regular tree-structured model, and the Markov characteristics in most phenomena or processes, the multiscale representation with one kind of stochastic processes are presented, and the corresponding multiscale models are also proposed by the introducing irregular tree structure, and some good functions from these new models are illustrated by numerical examples together with computer simulations.
Based on the modeling methods with the regular tree-structured model, and the Markov characteristics in most phenomena or processes, the multiscale representation with one kind of stochastic processes are presented, and the corresponding multiscale models are also proposed by the introducing irregular tree structure, and some good functions from these new models are illustrated by numerical examples together with computer simulations.
2008, 30(1): 168-171.
doi: 10.3724/SP.J.1146.2007.00234
Abstract:
The accurate knowledge of the sub-pixel registration parameters for each observed Low-Resolution (LR) image is the key for image Super-Resolution Reconstruction (SRR). Many registration algorithms fail to provide sufficient precision for SRR when the LR images are severely aliased. However, the method which combines the registration problem into SRR can obtain accurate estimation for registration parameters of each LR image in this situation. This paper analyzed the method and proposed a new approach to solve it. The proposed approach uses the principle similar to variable projection which results in a better-conditioned problem and avoids some shortcomings of cyclic coordinate descent optimization procedure. It can be efficiently implemented by using Lanczos method and Gauss quadrature theory. As a result, the proposed approach can deal with translation and rotation between the LR images. Experimental results demonstrate the effectiveness of our approach.
The accurate knowledge of the sub-pixel registration parameters for each observed Low-Resolution (LR) image is the key for image Super-Resolution Reconstruction (SRR). Many registration algorithms fail to provide sufficient precision for SRR when the LR images are severely aliased. However, the method which combines the registration problem into SRR can obtain accurate estimation for registration parameters of each LR image in this situation. This paper analyzed the method and proposed a new approach to solve it. The proposed approach uses the principle similar to variable projection which results in a better-conditioned problem and avoids some shortcomings of cyclic coordinate descent optimization procedure. It can be efficiently implemented by using Lanczos method and Gauss quadrature theory. As a result, the proposed approach can deal with translation and rotation between the LR images. Experimental results demonstrate the effectiveness of our approach.
2008, 30(1): 172-175.
doi: 10.3724/SP.J.1146.2006.01705
Abstract:
Standard Mean Shift tracker can only successfully locate the object center, but fail to find its orientation, which make it not robust to track thin object. To remedy this, an improved mean shift tracker is proposed in this paper. The new tracker use new object representation, where pixels are weighted with both their position-angles and normalized distances from target center, furthermore, pixels feature-angle, which can be seen as new feature, is introduced in. The new object representation can be conveniently integrated into the optimization framework of mean shift. By iterative optimization, both the location and orientation of targets can be precisely determined. Experimental results show the algorithm can get precise tracking results with low computational cost.
Standard Mean Shift tracker can only successfully locate the object center, but fail to find its orientation, which make it not robust to track thin object. To remedy this, an improved mean shift tracker is proposed in this paper. The new tracker use new object representation, where pixels are weighted with both their position-angles and normalized distances from target center, furthermore, pixels feature-angle, which can be seen as new feature, is introduced in. The new object representation can be conveniently integrated into the optimization framework of mean shift. By iterative optimization, both the location and orientation of targets can be precisely determined. Experimental results show the algorithm can get precise tracking results with low computational cost.
2008, 30(1): 176-179.
doi: 10.3724/SP.J.1146.2006.00808
Abstract:
Subspace learning is an effective dimensionality reduction method. However, the resulting basis vectors are significantly biased due to the presence of outlier points. Consequently, the transformed data in the subspace cannot faithfully describe the intrinsic distribution of the original data. To tackle this problem, a modified subspace learning algorithm is proposed. In the algorithm it is not necessary to detect outliers. Moreover, the algorithm is reduced to an eignenvalue problem which has a globally optimal solution. Experiments on synthetic data demonstrate the effectiveness of the proposed algorithm.
Subspace learning is an effective dimensionality reduction method. However, the resulting basis vectors are significantly biased due to the presence of outlier points. Consequently, the transformed data in the subspace cannot faithfully describe the intrinsic distribution of the original data. To tackle this problem, a modified subspace learning algorithm is proposed. In the algorithm it is not necessary to detect outliers. Moreover, the algorithm is reduced to an eignenvalue problem which has a globally optimal solution. Experiments on synthetic data demonstrate the effectiveness of the proposed algorithm.
2008, 30(1): 180-184.
doi: 10.3724/SP.J.1146.2006.00935
Abstract:
As a technique of feature extraction, 2DPCA is effective and efficient. Different from traditional PCA, it directly computes projection of one image matrix onto vector, to obtain feature for the image. In fact, 2DPCA is optimal for dimension compression under this consideration. There are two approaches to implement 2DPCA. The two approaches transform images into different spaces, and emphasize horizontal feature and vertical feature of face images respectively. Because the features extracted by the two approaches may complement each other, two schemes are designed to perform feature fusion. Experiments based on the fused features achieve high classification right rates.
As a technique of feature extraction, 2DPCA is effective and efficient. Different from traditional PCA, it directly computes projection of one image matrix onto vector, to obtain feature for the image. In fact, 2DPCA is optimal for dimension compression under this consideration. There are two approaches to implement 2DPCA. The two approaches transform images into different spaces, and emphasize horizontal feature and vertical feature of face images respectively. Because the features extracted by the two approaches may complement each other, two schemes are designed to perform feature fusion. Experiments based on the fused features achieve high classification right rates.
2008, 30(1): 185-189.
doi: 10.3724/SP.J.1146.2006.00845
Abstract:
A new method based on two-dimensional feature extraction in the complex domain is proposed for face recognition in this paper. First, face images are performed by mirror transform, and the original face samples and the corresponding mirror samples are used to compute the even symmetry samples and the odd symmetry samples, respectively. The even symmetry samples and the odd symmetry samples are used to form complex samples by an odd-even weighted factor. Then the complex image within-class scatter matrix and the complex image between-class scatter matrix are defined in the complex domain, respectively, to calculate a family of optimal complex projection axes, and complex face samples are projected onto the family of optimal complex projection axes to extract the face features. Finally, a nearest neighbor classifier is employed to classify the extracted features. The method in the paper is evaluated on the NUST603 face image database. Experimental results show the proposed method achieves better performance.
A new method based on two-dimensional feature extraction in the complex domain is proposed for face recognition in this paper. First, face images are performed by mirror transform, and the original face samples and the corresponding mirror samples are used to compute the even symmetry samples and the odd symmetry samples, respectively. The even symmetry samples and the odd symmetry samples are used to form complex samples by an odd-even weighted factor. Then the complex image within-class scatter matrix and the complex image between-class scatter matrix are defined in the complex domain, respectively, to calculate a family of optimal complex projection axes, and complex face samples are projected onto the family of optimal complex projection axes to extract the face features. Finally, a nearest neighbor classifier is employed to classify the extracted features. The method in the paper is evaluated on the NUST603 face image database. Experimental results show the proposed method achieves better performance.
2008, 30(1): 190-193.
doi: 10.3724/SP.J.1146.2006.00811
Abstract:
Cosidering the so-called Small Sample Size(SSS) problem in nature and the inferior problem in traditional Fisher linear discriminant analysis, a new method of feature extraction based on modified maximum scatter-difference criterion is developed in this paper. The method gives an effective way to resolve two difficulties of the traditional Fisher linear discriminant analysis theoretically in face recognition. Finally, extensive experiments performed on ORL and AR face database verify the effectiveness of the proposed method.
Cosidering the so-called Small Sample Size(SSS) problem in nature and the inferior problem in traditional Fisher linear discriminant analysis, a new method of feature extraction based on modified maximum scatter-difference criterion is developed in this paper. The method gives an effective way to resolve two difficulties of the traditional Fisher linear discriminant analysis theoretically in face recognition. Finally, extensive experiments performed on ORL and AR face database verify the effectiveness of the proposed method.
2008, 30(1): 194-197.
doi: 10.3724/SP.J.1146.2006.00794
Abstract:
In general, small targets always are the extremum pixels in image local area. Based on the feature of targets, a new small target detection algorithm is presented based on the extremum theory for bi-variate cubic function. In this paper, a new model is developed named Zernike-facet model, which is used to fit local image intensity. And coefficients of the model are solved by the Total Least Squares (TLS) method, which performance in resisting noise is better than the Least Squares (LS) method. Then the new small target detection algorithm is proposed. The new algorithm used the Zernike-facet model and the TLS to fit image local intensity surface, and then those extremum points are extracted as targets. The simulations show that the new method is better in resisting noise than others. Several target detection experiments are carried out on visible /infrared image. The results demonstrate that the proposed method is efficient.
In general, small targets always are the extremum pixels in image local area. Based on the feature of targets, a new small target detection algorithm is presented based on the extremum theory for bi-variate cubic function. In this paper, a new model is developed named Zernike-facet model, which is used to fit local image intensity. And coefficients of the model are solved by the Total Least Squares (TLS) method, which performance in resisting noise is better than the Least Squares (LS) method. Then the new small target detection algorithm is proposed. The new algorithm used the Zernike-facet model and the TLS to fit image local intensity surface, and then those extremum points are extracted as targets. The simulations show that the new method is better in resisting noise than others. Several target detection experiments are carried out on visible /infrared image. The results demonstrate that the proposed method is efficient.
2008, 30(1): 198-202.
doi: 10.3724/SP.J.1146.2006.00879
Abstract:
Radar High Range Resolution Profile (HRRP) is very sensitive to target aspect variation. To deal with this problem, usually, multiple statistical models are built for different target aspect sector when using HRRP for target recognition. Therefore, how to determine target aspect sector number and how to divide target aspect sector play an important role in classifier training. A data driven adaptive learning algorithm is proposed in this paper, which determines the target aspect sector boundary based on a multivariate Gaussian statistical data model and an iteration algorithm, and the target aspect sector number can be determined simultaneously. Comparing with the traditional equal interval target aspect partition approach, the proposed approach can achieve better recognition performance with lower computation complexity. Experimental results based on the measured data show the efficiency of the proposed method.
Radar High Range Resolution Profile (HRRP) is very sensitive to target aspect variation. To deal with this problem, usually, multiple statistical models are built for different target aspect sector when using HRRP for target recognition. Therefore, how to determine target aspect sector number and how to divide target aspect sector play an important role in classifier training. A data driven adaptive learning algorithm is proposed in this paper, which determines the target aspect sector boundary based on a multivariate Gaussian statistical data model and an iteration algorithm, and the target aspect sector number can be determined simultaneously. Comparing with the traditional equal interval target aspect partition approach, the proposed approach can achieve better recognition performance with lower computation complexity. Experimental results based on the measured data show the efficiency of the proposed method.
2008, 30(1): 203-205.
doi: 10.3724/SP.J.1146.2006.00829
Abstract:
The estimation of the parameters of K-distribution based on the z log(z) expectation approach is extended to zr log(z) expectation. The parameter estimation expression of the based on zr log(z) expectation is derived. When r is taken different values, the accuracies of the estimations based on the zr log(z) expectation are analyzed and compared with one another. Simulation results show that in the parameters range of K distribution radar spiky clutter, the estimation based on zr log(z) expectation is more accurate than z log(z) expectation and Normalised Log Estimator (NLE) approaches when r is less than unity.
The estimation of the parameters of K-distribution based on the z log(z) expectation approach is extended to zr log(z) expectation. The parameter estimation expression of the based on zr log(z) expectation is derived. When r is taken different values, the accuracies of the estimations based on the zr log(z) expectation are analyzed and compared with one another. Simulation results show that in the parameters range of K distribution radar spiky clutter, the estimation based on zr log(z) expectation is more accurate than z log(z) expectation and Normalised Log Estimator (NLE) approaches when r is less than unity.
2008, 30(1): 206-210.
doi: 10.3724/SP.J.1146.2006.00842
Abstract:
Interference statistic characteristics are analyzed in ship-based passive synthetic Impulse and Aperture Radar (SIAR). After estimating covariance matrix at range bin interested using data from some positive and all negative frequency bins with cosine weights, eigen-decomposition is applied to interested data for co-channel interference suppression provided that its power is stronger than target echoes. Meanwhile, improved suppression approach to nonstationary interference from multipath propagation is proposed by forming adaptive STAP in fast-time domain and maintaining slow-time statistical properties of the first order sea clutter output approximately unperturbed by filter fluctuation. Analysis and suppression approach are verified by real data.
Interference statistic characteristics are analyzed in ship-based passive synthetic Impulse and Aperture Radar (SIAR). After estimating covariance matrix at range bin interested using data from some positive and all negative frequency bins with cosine weights, eigen-decomposition is applied to interested data for co-channel interference suppression provided that its power is stronger than target echoes. Meanwhile, improved suppression approach to nonstationary interference from multipath propagation is proposed by forming adaptive STAP in fast-time domain and maintaining slow-time statistical properties of the first order sea clutter output approximately unperturbed by filter fluctuation. Analysis and suppression approach are verified by real data.
2008, 30(1): 211-215.
doi: 10.3724/SP.J.1146.2006.00877
Abstract:
Because of the property that Synthetic Aperture Radar (SAR) images include plenty of multiplicative speckle noise, an effective image segmentation algorithm is proposed based on the wavelet hidden-class-label Markov Random Field (MRF) to suppress the affect of speckle. To consider the clustering and persistence of wavelet, the hidden-class-label MRF is extended to the wavelet domain with a new wavelet model for segmented image named hidden-class-label mixture heavy-tailed model, and interscale transition probability is estimated with improved context, then a new Maximum A Posteriori (MAP) classification is obtained. The experimental results show that the method suppresses the affect of noise effectively to achieve exact and robust segmentation result.
Because of the property that Synthetic Aperture Radar (SAR) images include plenty of multiplicative speckle noise, an effective image segmentation algorithm is proposed based on the wavelet hidden-class-label Markov Random Field (MRF) to suppress the affect of speckle. To consider the clustering and persistence of wavelet, the hidden-class-label MRF is extended to the wavelet domain with a new wavelet model for segmented image named hidden-class-label mixture heavy-tailed model, and interscale transition probability is estimated with improved context, then a new Maximum A Posteriori (MAP) classification is obtained. The experimental results show that the method suppresses the affect of noise effectively to achieve exact and robust segmentation result.
2008, 30(1): 216-219.
doi: 10.3724/SP.J.1146.2006.00887
Abstract:
This paper proposes a method for multi-polarization Synthetic Aperture Radar (SAR) images compression: 3D-SPIHT，which considers the multi-polarimetric SAR images(HH,HV,VV) as a 3D-matrix unit, then does 3D-matrix transform to it. First, 1D-DCT(Discrete Cosine Transform) is processed among the polarimetric channel and then 2D-DWT(Discrete Wavelet Transform) is processed in the polarimetric SAR image plane, finally, 3D-SPIHT algorithm is adopted to encode the mixed coefficients of three frames entirely. This method does not process every channel image separately, so it not only can remove the redundancies of the image inside, but also can remove the redundancies among the polarimetric channels. And whats more, the embedded code stream can implement the precise bit allocation among the polarization channels. Both the theory and the experimental results show that the method in this paper is efficient.
This paper proposes a method for multi-polarization Synthetic Aperture Radar (SAR) images compression: 3D-SPIHT，which considers the multi-polarimetric SAR images(HH,HV,VV) as a 3D-matrix unit, then does 3D-matrix transform to it. First, 1D-DCT(Discrete Cosine Transform) is processed among the polarimetric channel and then 2D-DWT(Discrete Wavelet Transform) is processed in the polarimetric SAR image plane, finally, 3D-SPIHT algorithm is adopted to encode the mixed coefficients of three frames entirely. This method does not process every channel image separately, so it not only can remove the redundancies of the image inside, but also can remove the redundancies among the polarimetric channels. And whats more, the embedded code stream can implement the precise bit allocation among the polarization channels. Both the theory and the experimental results show that the method in this paper is efficient.
2008, 30(1): 220-223.
doi: 10.3724/SP.J.1146.2006.01613
Abstract:
The presence of speckle is a major cause of degradation in SAR images. The Multilook Polarimetric Whitening Filter (MPWF) is an effective method on speckle reduction in multilook polarimetric Synthetic Aperture Radar (SAR) images. However, the capability of the filter is directly decided with the precision of the filter-parameter estimation. Hence, a novel adaptive windowing algorithm based on unsupervised classification is proposed here, where the classified image is chosen as the processed object and the central pixel in moving rectangular window is as the reference. Then through automatic search, the pixels around the central pixel which are in the same class are selected and used for parameter estimation. Compared to some other typical methods, this approach is demonstrated the effectiveness both on speckle reduction and preservation of texture information from the experimental results.
The presence of speckle is a major cause of degradation in SAR images. The Multilook Polarimetric Whitening Filter (MPWF) is an effective method on speckle reduction in multilook polarimetric Synthetic Aperture Radar (SAR) images. However, the capability of the filter is directly decided with the precision of the filter-parameter estimation. Hence, a novel adaptive windowing algorithm based on unsupervised classification is proposed here, where the classified image is chosen as the processed object and the central pixel in moving rectangular window is as the reference. Then through automatic search, the pixels around the central pixel which are in the same class are selected and used for parameter estimation. Compared to some other typical methods, this approach is demonstrated the effectiveness both on speckle reduction and preservation of texture information from the experimental results.
2008, 30(1): 224-227.
doi: 10.3724/SP.J.1146.2006.00835
Abstract:
In the presence of multi-path propagation, it is quite difficult for VHF radar to measure the altitude of a low elevation target. In this paper, a new alternating projection algorithm is proposed to estimate the DOA of the target. By projecting the correlation matrix of the target echo into different signal subspaces, this method can be used to estimate accurately the directions of both the direct wave and the reflected wave, and hence the altitude of the target is known precisely. Results of both computer simulation and the real data from some VHF radar demonstrate the validity of the new algorithm. The Monte-Carlo experiment proves that the performance of the new algorithm is better than that of the temporal-spatial sequential ML algorithm.
In the presence of multi-path propagation, it is quite difficult for VHF radar to measure the altitude of a low elevation target. In this paper, a new alternating projection algorithm is proposed to estimate the DOA of the target. By projecting the correlation matrix of the target echo into different signal subspaces, this method can be used to estimate accurately the directions of both the direct wave and the reflected wave, and hence the altitude of the target is known precisely. Results of both computer simulation and the real data from some VHF radar demonstrate the validity of the new algorithm. The Monte-Carlo experiment proves that the performance of the new algorithm is better than that of the temporal-spatial sequential ML algorithm.
2008, 30(1): 228-232.
doi: 10.3724/SP.J.1146.2006.00747
Abstract:
Based on the problem that side-looking SAR can not image in flight direction with high azimuth resolution, an innovative forward-looking SAR system is studied. The operation mechanism and feasibility of high azimuth resolution are analyzed. According to the spatial geometry and the model of echo signal, chirp scaling algorithm is proposed for forward-looking SAR. The phase compensation factors and realized steps of algorithm are given. Raw data of forward-looking SAR is simulated, and image is achieved by using the chirp scaling algorithm proposed in this paper. The imaging effect is analyzed, and imaging quality is consistent with theory value. Simulation results demonstrate the validity of the algorithm.
Based on the problem that side-looking SAR can not image in flight direction with high azimuth resolution, an innovative forward-looking SAR system is studied. The operation mechanism and feasibility of high azimuth resolution are analyzed. According to the spatial geometry and the model of echo signal, chirp scaling algorithm is proposed for forward-looking SAR. The phase compensation factors and realized steps of algorithm are given. Raw data of forward-looking SAR is simulated, and image is achieved by using the chirp scaling algorithm proposed in this paper. The imaging effect is analyzed, and imaging quality is consistent with theory value. Simulation results demonstrate the validity of the algorithm.
2008, 30(1): 233-237.
doi: 10.3724/SP.J.1146.2006.00865
Abstract:
A noval Divided-Fitting Method based on Coons surface and B-spline (DFMB) to fit the distorted antenna affected by different loads is presented for accurately describing the real deformation of antenna surface. It firstly divides the distorted reflector into many individual zones, uses the Coons surface to fit each zone, and determines the boundary of each zone by third-order hoop and second-order radial B-spline curves. Then the precise local and total information of distorted reflector can be obtained to compute the electrical performances of antenna. The good electromechanical simulation results of the application to a 16-m parabolic antenna proved the validity of developed method.
A noval Divided-Fitting Method based on Coons surface and B-spline (DFMB) to fit the distorted antenna affected by different loads is presented for accurately describing the real deformation of antenna surface. It firstly divides the distorted reflector into many individual zones, uses the Coons surface to fit each zone, and determines the boundary of each zone by third-order hoop and second-order radial B-spline curves. Then the precise local and total information of distorted reflector can be obtained to compute the electrical performances of antenna. The good electromechanical simulation results of the application to a 16-m parabolic antenna proved the validity of developed method.
2008, 30(1): 238-240.
doi: 10.3724/SP.J.1146.2006.00987
Abstract:
Large memory and computation time requirement always make the electrical property of microstrip array can not be evaluated with MOM, however, Adaptive Integral Method (AIM) can reduce memory and computation time greatly. Scattering of microstrip patch array and radiation of microstrip antenna array are computed with AIM, and computation results show that electrical property of microstrip antenna can be obtained fast with less memory with AIM.
Large memory and computation time requirement always make the electrical property of microstrip array can not be evaluated with MOM, however, Adaptive Integral Method (AIM) can reduce memory and computation time greatly. Scattering of microstrip patch array and radiation of microstrip antenna array are computed with AIM, and computation results show that electrical property of microstrip antenna can be obtained fast with less memory with AIM.
2008, 30(1): 241-244.
doi: 10.3724/SP.J.1146.2006.01086
Abstract:
The effects of four coupling slots on antenna resonance frequency and bandwidth are studied respectively. And these effects are explained with the near field distributions. Feeding characteristics of several coupling slots are analyzed and compared, which greatly improve the flexibility of antenna design. By modifying the feeding device with the conversion idea, a broadband microstrip antenna is designed with a bandwidth of 28.9% .The gain is more than 8dBi in the operating frequency band of 3.76～4.80GHz. The gain bandwidth is 24.2%.
The effects of four coupling slots on antenna resonance frequency and bandwidth are studied respectively. And these effects are explained with the near field distributions. Feeding characteristics of several coupling slots are analyzed and compared, which greatly improve the flexibility of antenna design. By modifying the feeding device with the conversion idea, a broadband microstrip antenna is designed with a bandwidth of 28.9% .The gain is more than 8dBi in the operating frequency band of 3.76～4.80GHz. The gain bandwidth is 24.2%.
2008, 30(1): 249-251.
doi: 10.3724/SP.J.1146.2007.00840
Abstract:
The feasibility of making two antennas work with a shared aperture on a platform is investigated. The aperture is formed by a deep cavity with a dielectric radome. A Quadrifilar Helix Antenna (QHA) is adopted for the platform positioning and a horizontal monopole using the cylindrical wall of the cavity as its ground is adopted for communication. In order to tune the QHA in the cavity, an improvement is proposed by utilizing the bottom of the cavity and the horizontal branches of the four helices. The effect of the cavity on the antennas and the interaction of the two antennas are studied through experiments. The results show that the two antennas of the overall arrangement perform simultaneously well in the cavity and the mutual coupling effect expands the bandwidth of the horizontal monopole.
The feasibility of making two antennas work with a shared aperture on a platform is investigated. The aperture is formed by a deep cavity with a dielectric radome. A Quadrifilar Helix Antenna (QHA) is adopted for the platform positioning and a horizontal monopole using the cylindrical wall of the cavity as its ground is adopted for communication. In order to tune the QHA in the cavity, an improvement is proposed by utilizing the bottom of the cavity and the horizontal branches of the four helices. The effect of the cavity on the antennas and the interaction of the two antennas are studied through experiments. The results show that the two antennas of the overall arrangement perform simultaneously well in the cavity and the mutual coupling effect expands the bandwidth of the horizontal monopole.
2008, 30(1): 245-248.
doi: 10.3724/SP.J.1146.2006.00818
Abstract:
In this paper, a new anonymous proxy signature scheme proposed by Gu Li-ze et al.(2005) is cryptanalyzed in detail and is proved that this scheme is not secure against the original signers forgery attack and then four methods to attack the new scheme are found. To avoid these attacks, the new scheme is revised and two improved schemes are given. Finally, the improved schemes are concluded that they are both secure against the original signers forgery attack.
In this paper, a new anonymous proxy signature scheme proposed by Gu Li-ze et al.(2005) is cryptanalyzed in detail and is proved that this scheme is not secure against the original signers forgery attack and then four methods to attack the new scheme are found. To avoid these attacks, the new scheme is revised and two improved schemes are given. Finally, the improved schemes are concluded that they are both secure against the original signers forgery attack.
