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2005 Vol. 27, No. 3
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2005, 27(3): 337-340.
Abstract:
Direct Interconnection Networks (DIN) are considered to build scalable switching fabrics for Internet routers/switches, clue to its easy scalability. Furthermore, QoS (Quality of Service) guarantee is very important in switching systems. In this paper, fair bandwidth allocation and priority traffic supporting adaptive algorithm in the DIN is presented. In the switching fabric, there are tight relationships between the schedule scheme and the routing strategy. In order to supporting QoS in the DIN, a new Priority Supporting Adaptive Routing Algorithm (PSAR) is presented, which considers the scheduling strategy and routing scheme at the same time. Simulation results show the algorithm can fairly allocate the output port bandwidth to each input port, and support priority traffic.
Direct Interconnection Networks (DIN) are considered to build scalable switching fabrics for Internet routers/switches, clue to its easy scalability. Furthermore, QoS (Quality of Service) guarantee is very important in switching systems. In this paper, fair bandwidth allocation and priority traffic supporting adaptive algorithm in the DIN is presented. In the switching fabric, there are tight relationships between the schedule scheme and the routing strategy. In order to supporting QoS in the DIN, a new Priority Supporting Adaptive Routing Algorithm (PSAR) is presented, which considers the scheduling strategy and routing scheme at the same time. Simulation results show the algorithm can fairly allocate the output port bandwidth to each input port, and support priority traffic.
2005, 27(3): 341-345.
Abstract:
The input queued switch fabric, because of its scalability, has been implemented in more and more high speed switches and routers. Existing scheduling algorithms attempt to get the maximum throughput at the expense of fairness. As the need for Quality of Service (QoS) becomes stronger, the efficient scheduling algorithm with guaranteed fairness for Input Queued (IQ) switch has become an urgent problem. In this paper a virtual service based fair scheduling algorithm with guaranteed fairness for IQ is proposed. Theoretical analysis and computer simulation show that this algorithm can provide better performance in respects of fairness and cell delay. With the same low communication cost as iSLIP and the same computing complexity as iLQF, this algorithm has better practicability.
The input queued switch fabric, because of its scalability, has been implemented in more and more high speed switches and routers. Existing scheduling algorithms attempt to get the maximum throughput at the expense of fairness. As the need for Quality of Service (QoS) becomes stronger, the efficient scheduling algorithm with guaranteed fairness for Input Queued (IQ) switch has become an urgent problem. In this paper a virtual service based fair scheduling algorithm with guaranteed fairness for IQ is proposed. Theoretical analysis and computer simulation show that this algorithm can provide better performance in respects of fairness and cell delay. With the same low communication cost as iSLIP and the same computing complexity as iLQF, this algorithm has better practicability.
2005, 27(3): 346-350.
Abstract:
To defend against DDoS attacks on Internet, a new scheme called Ingress Address Marking (IAM) within an Autonomous System (AS) is proposed, with which the IP addresses of the ingress can be embedded into the forwarding packets. A victim can traceback the addresses of the attack ingress in a low complexity by analyzing the marking information. Besides the physical model, the mathematical formulation of false positive ratio and correlation function are provided. The relationship of the ingress link and the structure of AS is reviewed. The construction and deployment of IAM are discussed. Simulation results have shown that this scheme has a good performance and is valuable on both theory and application.
To defend against DDoS attacks on Internet, a new scheme called Ingress Address Marking (IAM) within an Autonomous System (AS) is proposed, with which the IP addresses of the ingress can be embedded into the forwarding packets. A victim can traceback the addresses of the attack ingress in a low complexity by analyzing the marking information. Besides the physical model, the mathematical formulation of false positive ratio and correlation function are provided. The relationship of the ingress link and the structure of AS is reviewed. The construction and deployment of IAM are discussed. Simulation results have shown that this scheme has a good performance and is valuable on both theory and application.
2005, 27(3): 351-354.
Abstract:
Exploit automation and massive global scanning for vulnerabilities enable adversaries to compromise computer systems shortly after vulnerabilities become known. Traditional honeypots have shortcomings to deal with these problems because their signatures can be inspected. Aiming at current research state, the paper constructs an Active Network Security System (ANSS) from another point of view, i.e., ANSS situated in a real network circumstance. ANSS is the same as other systems in Internet, and it can capture actions of hacker from beginning to end. The simulation results indicate that ANSS can elevate networks security performance to a higher level and ANSS has important impact on forecast and monitor attack activities.
Exploit automation and massive global scanning for vulnerabilities enable adversaries to compromise computer systems shortly after vulnerabilities become known. Traditional honeypots have shortcomings to deal with these problems because their signatures can be inspected. Aiming at current research state, the paper constructs an Active Network Security System (ANSS) from another point of view, i.e., ANSS situated in a real network circumstance. ANSS is the same as other systems in Internet, and it can capture actions of hacker from beginning to end. The simulation results indicate that ANSS can elevate networks security performance to a higher level and ANSS has important impact on forecast and monitor attack activities.
2005, 27(3): 355-358.
Abstract:
To guarantee quality of service of real-time traffic, an algorithm based on AODV is presented. In this algorithm, node maintains traffic information of nodes in its neighborhood. Reservable bandwidth is used as the main consult in routing.Simulation shows that the QoS of real time traffic is guaranteed and the algorithm is superior to standard AODV routing algorithm in terms of delivery rate and mean end to end packet delay.
To guarantee quality of service of real-time traffic, an algorithm based on AODV is presented. In this algorithm, node maintains traffic information of nodes in its neighborhood. Reservable bandwidth is used as the main consult in routing.Simulation shows that the QoS of real time traffic is guaranteed and the algorithm is superior to standard AODV routing algorithm in terms of delivery rate and mean end to end packet delay.
2005, 27(3): 359-363.
Abstract:
The IEEE 802.11 standard MAC is a hybrid protocol of random access and polling when both DCF (Distributed Coordination Function) and PCF (Point Coordination Function) are used. On the base of the performance analysis of the MAC protocol for integrated data and voice transmission by simulation, this paper puts forward a self-adaptive transmission scheme to support multi-service over the IEEE 802.11 WLAN. The simulation results show that, on the premise of satisfying the maximum allowable delay of packet voice, the self-adaptive transmission scheme can improve the data traffic performance and increase the WLAN capacity through dynamic and appropriate adjustment of the protocol parameters. Especially, the scheme is easy to be realized for no change in the MAC protocol is needed.
The IEEE 802.11 standard MAC is a hybrid protocol of random access and polling when both DCF (Distributed Coordination Function) and PCF (Point Coordination Function) are used. On the base of the performance analysis of the MAC protocol for integrated data and voice transmission by simulation, this paper puts forward a self-adaptive transmission scheme to support multi-service over the IEEE 802.11 WLAN. The simulation results show that, on the premise of satisfying the maximum allowable delay of packet voice, the self-adaptive transmission scheme can improve the data traffic performance and increase the WLAN capacity through dynamic and appropriate adjustment of the protocol parameters. Especially, the scheme is easy to be realized for no change in the MAC protocol is needed.
2005, 27(3): 364-368.
Abstract:
OFDM systems are sensitive to the frequency offset. In this paper, a novel frequency ambiguity resolution algorithm in OFDM systems based on phase differential modulation between adjacent symbols is proposed to correct the frequency ambiguity. The sufficient condition for the proposed algorithm to achieve unique identifiability is deduced. Moreover, the computational complexity of the proposed algorithm and the sensitivity of the proposed algorithm to the timing error are also analyzed in the paper. Theoretical analysis and computer simulations show that the proposed algorithm has the low complexity advantage over conventional algorithm while maintaining approximately the same performance.
OFDM systems are sensitive to the frequency offset. In this paper, a novel frequency ambiguity resolution algorithm in OFDM systems based on phase differential modulation between adjacent symbols is proposed to correct the frequency ambiguity. The sufficient condition for the proposed algorithm to achieve unique identifiability is deduced. Moreover, the computational complexity of the proposed algorithm and the sensitivity of the proposed algorithm to the timing error are also analyzed in the paper. Theoretical analysis and computer simulations show that the proposed algorithm has the low complexity advantage over conventional algorithm while maintaining approximately the same performance.
2005, 27(3): 369-372.
Abstract:
The OFDM signal is analyzed as a continuous stochastic processes and the closed form expression of correlation function between any two given time instant is derived. When the sampling rate increases, the correlation increases quickly and the peak-to-average power ratio of oversampling OFDM signal changes neglectably. Especially, when oversampling factor is 2, the covariance matrix is analyzed. The results of analysis and simulation denote that all samples in one symbol are approximately independent. According to the result, the probability distribution function of peak-to-average power ratio is obtained.
The OFDM signal is analyzed as a continuous stochastic processes and the closed form expression of correlation function between any two given time instant is derived. When the sampling rate increases, the correlation increases quickly and the peak-to-average power ratio of oversampling OFDM signal changes neglectably. Especially, when oversampling factor is 2, the covariance matrix is analyzed. The results of analysis and simulation denote that all samples in one symbol are approximately independent. According to the result, the probability distribution function of peak-to-average power ratio is obtained.
2005, 27(3): 373-376.
Abstract:
A key obstacle to high accuracy mobile location is the None Line of Sight (NLOS) transmission of signal. This paper presents a new radio location algorithm-believable factor algorithm (BFA), based on the time of arrival (TOA) range measurements, using the geometric relationship between the base station and measurements, the path loss model and received signal strength. Different distributed NLOS error is utilized to research the performance of this approach. Results show that the BFA algorithm can efficiently reduce the influence of the NLOS error, and is robust to different distributed NLOS error. The location accuracy has been improved greatly compared with other algorithms.
A key obstacle to high accuracy mobile location is the None Line of Sight (NLOS) transmission of signal. This paper presents a new radio location algorithm-believable factor algorithm (BFA), based on the time of arrival (TOA) range measurements, using the geometric relationship between the base station and measurements, the path loss model and received signal strength. Different distributed NLOS error is utilized to research the performance of this approach. Results show that the BFA algorithm can efficiently reduce the influence of the NLOS error, and is robust to different distributed NLOS error. The location accuracy has been improved greatly compared with other algorithms.
2005, 27(3): 377-379.
Abstract:
Space-time reveivers for the third-generation mobile communication systems is important. For a realistic simulation of such systems, a simple statistical space-time vector channel model is proposed, and the space-time-frequency correlation matrix of space-time channel which characterizes reasonably the space- and time-variant effects of the mobile radio channel is presented , and deriver the correlation between two antenna elements as a function of the power azimuth spectrum.
Space-time reveivers for the third-generation mobile communication systems is important. For a realistic simulation of such systems, a simple statistical space-time vector channel model is proposed, and the space-time-frequency correlation matrix of space-time channel which characterizes reasonably the space- and time-variant effects of the mobile radio channel is presented , and deriver the correlation between two antenna elements as a function of the power azimuth spectrum.
2005, 27(3): 380-383.
Abstract:
Chip equalization is one of the key technologies for improving the performance of the 3rd generation mobile communication system. In order to enhance the performance of the chip equalizer, a new scheme of chip equalizer jointed with pilot cancellation and Rake is presented in this paper. Computer simulations show that the new scheme effectively improves the performance of the receiver.
Chip equalization is one of the key technologies for improving the performance of the 3rd generation mobile communication system. In order to enhance the performance of the chip equalizer, a new scheme of chip equalizer jointed with pilot cancellation and Rake is presented in this paper. Computer simulations show that the new scheme effectively improves the performance of the receiver.
2005, 27(3): 384-387.
Abstract:
In this paper, a new linear blind adaptive multiuser detection based on LMK. criterion is proposed for synchronous DS/CDMA system over multipath fading channels, The new algorithm bases on HOS(High Order Statistics) and reduces complexity remarkably. The convergence of this algorithm is analyzed over multipath fading channel in the noise-free environment. In this case, the algorithm has global minimum point. On global minimum point, the algorithm satisfies dccorrelating condition and can completely remove multiple-access interference. The simulation results show that the algorithm has good performance.
In this paper, a new linear blind adaptive multiuser detection based on LMK. criterion is proposed for synchronous DS/CDMA system over multipath fading channels, The new algorithm bases on HOS(High Order Statistics) and reduces complexity remarkably. The convergence of this algorithm is analyzed over multipath fading channel in the noise-free environment. In this case, the algorithm has global minimum point. On global minimum point, the algorithm satisfies dccorrelating condition and can completely remove multiple-access interference. The simulation results show that the algorithm has good performance.
2005, 27(3): 388-391.
Abstract:
In this paper, a chaotic optimization method is presented for computing the Maximum Likelihood Estimation (MLE) of Direction of Arrivals (DOA) in sensor array processing. Based on the properties of ergodicity, stochastic property and regularity of chaos, the chaos optimization method can get global solution with low computational load. The simulation results show that this method is feasible and effective. Especially when the impinging signals are coherent, this method is much superior to AP.
In this paper, a chaotic optimization method is presented for computing the Maximum Likelihood Estimation (MLE) of Direction of Arrivals (DOA) in sensor array processing. Based on the properties of ergodicity, stochastic property and regularity of chaos, the chaos optimization method can get global solution with low computational load. The simulation results show that this method is feasible and effective. Especially when the impinging signals are coherent, this method is much superior to AP.
2005, 27(3): 392-396.
Abstract:
This paper presents a fast algorithm to detect the Least Significant Bit (LSB) steganography. The new approach is inspired by the work of Dumitrescu et al(2003) who detected LSB steganography via sample pair analysis. The new algorithm combines with the statistical measures developed by Dumitrescu and a new least square estimation. A simple cubic equation is deduced to describe the length of hidden messages with relatively high robust and precision. Moreover, compared with Dumitrescus algorithm, the novel method has much lower false alarm rate of 5% than that of 13.79%, and the estimating precision is about 9% higher if the embedding ratio is less than 10%, and the speed is also about 15 % faster. Some theoretical derivations are also included.
This paper presents a fast algorithm to detect the Least Significant Bit (LSB) steganography. The new approach is inspired by the work of Dumitrescu et al(2003) who detected LSB steganography via sample pair analysis. The new algorithm combines with the statistical measures developed by Dumitrescu and a new least square estimation. A simple cubic equation is deduced to describe the length of hidden messages with relatively high robust and precision. Moreover, compared with Dumitrescus algorithm, the novel method has much lower false alarm rate of 5% than that of 13.79%, and the estimating precision is about 9% higher if the embedding ratio is less than 10%, and the speed is also about 15 % faster. Some theoretical derivations are also included.
2005, 27(3): 397-401.
Abstract:
According to the theory of orthogonal designs, Tarokh et al.(1999) proved that a complex orthogonal space-time block code that provides full diversity and full transmission rate is not feasible for more than two antennas. Whereas the non-orthogonal space-time block codes which obtain higher transmission rate at the cost of orthogonality and partial diversity gain may degrade the performance. By rotating the channel correlation matrix of the non-orthogonal space-time block code, this paper proposes an orthogonal rate-one space-time block code which provides partial diversity but can be linearly decoded at the receiver. Simulation results show that the scheme has better Bit Error Rate (BER.) performance compared to the existing typical codes.
According to the theory of orthogonal designs, Tarokh et al.(1999) proved that a complex orthogonal space-time block code that provides full diversity and full transmission rate is not feasible for more than two antennas. Whereas the non-orthogonal space-time block codes which obtain higher transmission rate at the cost of orthogonality and partial diversity gain may degrade the performance. By rotating the channel correlation matrix of the non-orthogonal space-time block code, this paper proposes an orthogonal rate-one space-time block code which provides partial diversity but can be linearly decoded at the receiver. Simulation results show that the scheme has better Bit Error Rate (BER.) performance compared to the existing typical codes.
2005, 27(3): 402-406.
Abstract:
A ROI-based rate allocation algorithm for the MPEG-4 FGS enhancement layer is proposed in this paper. On the basis of the ROI-oriented rate-distortion model, the proposed algorithm can perform optimal rate allocation for the enhancement layer after selective enhancement under equal image quality constraint. The experimental results show that, compared with the conventional average rate allocation algorithm, the proposed algorithm can significantly eliminate the quality fluctuation of ROI. Simultaneously, the computational complexity of the proposed method is low enough to meet the requirements of the real time rate allocation at the video server.
A ROI-based rate allocation algorithm for the MPEG-4 FGS enhancement layer is proposed in this paper. On the basis of the ROI-oriented rate-distortion model, the proposed algorithm can perform optimal rate allocation for the enhancement layer after selective enhancement under equal image quality constraint. The experimental results show that, compared with the conventional average rate allocation algorithm, the proposed algorithm can significantly eliminate the quality fluctuation of ROI. Simultaneously, the computational complexity of the proposed method is low enough to meet the requirements of the real time rate allocation at the video server.
2005, 27(3): 407-410.
Abstract:
This paper investigates the performance of a reduced rank MMSE correlator for a RAKE receiver in the context of CDMA in frequency selective multipath. The MMSE correlator based on the Correlations Subtractive Architecture (CSA) is very suit for frequency selective multipath. It is emonstrated that the standard multiuser limited RAKE receiver can achieve BER performance close to the MMSE receiver spanning multiple symbols by replacing its conventional correlator with an MMSE correlator. The CSA generates an MMSE correlator without requiring atrix inversion, thereby reducing computational complexity; this facilitates direct replacement of the standard RAKE correlator.
This paper investigates the performance of a reduced rank MMSE correlator for a RAKE receiver in the context of CDMA in frequency selective multipath. The MMSE correlator based on the Correlations Subtractive Architecture (CSA) is very suit for frequency selective multipath. It is emonstrated that the standard multiuser limited RAKE receiver can achieve BER performance close to the MMSE receiver spanning multiple symbols by replacing its conventional correlator with an MMSE correlator. The CSA generates an MMSE correlator without requiring atrix inversion, thereby reducing computational complexity; this facilitates direct replacement of the standard RAKE correlator.
2005, 27(3): 411-414.
Abstract:
Single-Carrier Frequency-Domain Equalization (SC-FDE) and multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) are two techniques to combat multipath fading in digital communications. This paper compares the BER performances of them for white Gaussian noise channel theoretically. By the value-changing property of Gaussian distributions tail probability, the following conclusion is drawn: OFDM is a little better than SC-FDE in BER performance for Sow Signal-to-Noise Ratio (SNR), while SC-FDE greatly outperforms OFDM for high SNR. This conclusion is significant to the design of the communication system for its important reference value.
Single-Carrier Frequency-Domain Equalization (SC-FDE) and multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) are two techniques to combat multipath fading in digital communications. This paper compares the BER performances of them for white Gaussian noise channel theoretically. By the value-changing property of Gaussian distributions tail probability, the following conclusion is drawn: OFDM is a little better than SC-FDE in BER performance for Sow Signal-to-Noise Ratio (SNR), while SC-FDE greatly outperforms OFDM for high SNR. This conclusion is significant to the design of the communication system for its important reference value.
2005, 27(3): 415-418.
Abstract:
In indoor environments, ultra-wide band signals suffer from dense multipath propagation and severe time dispersion. Rake reception is an important way to boost the performance of ultra-wide band receivers. With the assumption that BPSK modulation is used, the equations used to compute BER performance of Rake receivers in dense multipath channels are derived. The BER performance is related to the multipath channel parameters and the pulse autocorrelation coefficients. With a typical channel model and specific pulse shapes, the computation has been done.
In indoor environments, ultra-wide band signals suffer from dense multipath propagation and severe time dispersion. Rake reception is an important way to boost the performance of ultra-wide band receivers. With the assumption that BPSK modulation is used, the equations used to compute BER performance of Rake receivers in dense multipath channels are derived. The BER performance is related to the multipath channel parameters and the pulse autocorrelation coefficients. With a typical channel model and specific pulse shapes, the computation has been done.
2005, 27(3): 419-422.
Abstract:
A signal denoising algorithm based on singularity detection is introduced in this paper, It simplified the complicated linear interpolation operation needed in the 2-D image denoising so that the 2-D denoising is greatly simplified and it can also get the fast denoising and save lots of memory. A complete description of this method and its 1-D denoising simulation are presented. A simplified 2-D denoising simulation is presented, too. This method does not need the prior information of signal or noise. Simulation results indicate that compared to other wavelet based denoising algorithms, the main advantage of this method is: it can better detect and reduce the pulse noise and it can reduce the noise while keeping the signal edges better.
A signal denoising algorithm based on singularity detection is introduced in this paper, It simplified the complicated linear interpolation operation needed in the 2-D image denoising so that the 2-D denoising is greatly simplified and it can also get the fast denoising and save lots of memory. A complete description of this method and its 1-D denoising simulation are presented. A simplified 2-D denoising simulation is presented, too. This method does not need the prior information of signal or noise. Simulation results indicate that compared to other wavelet based denoising algorithms, the main advantage of this method is: it can better detect and reduce the pulse noise and it can reduce the noise while keeping the signal edges better.
2005, 27(3): 423-426.
Abstract:
By combining the Linearly Constrained Minimum Variance Beamformer(LCMVB) with the eigenspace-based beam former, this pnper presents the Eigenspace-based Linearly Constrained Minimum Variance Beamformer{ELCMVB). The ELCMVB first projects the presumed steering vector of the LCMVB onto the signal subspace, then gets the weight vector by using the LCMV and the projected steering vector. The theoretical analysis indicates that the ELCMVB outperforms the Generalized Eigenspace-based Beamlbrmer(GEIB).Compared to the GEIB, the ELCMVB removes the computation of the modified signal subspace and overcomes the numerical instability. Null constraints hardly affect the performance of the ELCMVB. Computer simulation results are also presented and demonstrate the merits of the ELCMVB.
By combining the Linearly Constrained Minimum Variance Beamformer(LCMVB) with the eigenspace-based beam former, this pnper presents the Eigenspace-based Linearly Constrained Minimum Variance Beamformer{ELCMVB). The ELCMVB first projects the presumed steering vector of the LCMVB onto the signal subspace, then gets the weight vector by using the LCMV and the projected steering vector. The theoretical analysis indicates that the ELCMVB outperforms the Generalized Eigenspace-based Beamlbrmer(GEIB).Compared to the GEIB, the ELCMVB removes the computation of the modified signal subspace and overcomes the numerical instability. Null constraints hardly affect the performance of the ELCMVB. Computer simulation results are also presented and demonstrate the merits of the ELCMVB.
2005, 27(3): 427-430.
Abstract:
A novel nonuniform sampling digital spectrum processing method based on wavelet transform is studied in this paper. The fundamental principle of nonuniform sampling wavelet transform is introduced and the processing procedure is presented from the uniform wavelet to nonuniform wavelet. The nonuniform sampling wavelet transform method is applied to the frequency detection in this paper. The results of the experiments show that it is an effective method for signal detection and it can exactly estimate the frequencies of sinusoidal signals.
A novel nonuniform sampling digital spectrum processing method based on wavelet transform is studied in this paper. The fundamental principle of nonuniform sampling wavelet transform is introduced and the processing procedure is presented from the uniform wavelet to nonuniform wavelet. The nonuniform sampling wavelet transform method is applied to the frequency detection in this paper. The results of the experiments show that it is an effective method for signal detection and it can exactly estimate the frequencies of sinusoidal signals.
2005, 27(3): 431-433.
Abstract:
In this paper, LFM signal reconnaissance theory based on fractional Fourier transform is discussed firstly. Compared with bilinear transform, the fractional Fourier transform is a linear operator and it can eliminate the intercross terms. Hence, it has better detection capability in severe electronic warfare environment. And then variable window search peak algorithm is presented. The simulation results validate the effectiveness of this algorithm.
In this paper, LFM signal reconnaissance theory based on fractional Fourier transform is discussed firstly. Compared with bilinear transform, the fractional Fourier transform is a linear operator and it can eliminate the intercross terms. Hence, it has better detection capability in severe electronic warfare environment. And then variable window search peak algorithm is presented. The simulation results validate the effectiveness of this algorithm.
2005, 27(3): 434-437.
Abstract:
Based on principle of orthogonal projection filtering, it is introduced firstly, the method of AM-FM interference excision using projection filtering in pseudo-random code fuzes is analyzed in detail. Moreover, the method in some cases is simulated. And, the correlator output SNR using projection filtering is deduced in detail. The results show that the method could filter not only FM interference effectively, but also AM-FM interference in pseudo-random code fuzes. Furthermore, the method could improve the output SNR, and could not cause distortion to the desired PN code at the receiver. However, estimation error of interference parameters has significantly effect on the performance of AM-FM interference excision using projection filtering.
Based on principle of orthogonal projection filtering, it is introduced firstly, the method of AM-FM interference excision using projection filtering in pseudo-random code fuzes is analyzed in detail. Moreover, the method in some cases is simulated. And, the correlator output SNR using projection filtering is deduced in detail. The results show that the method could filter not only FM interference effectively, but also AM-FM interference in pseudo-random code fuzes. Furthermore, the method could improve the output SNR, and could not cause distortion to the desired PN code at the receiver. However, estimation error of interference parameters has significantly effect on the performance of AM-FM interference excision using projection filtering.
2005, 27(3): 438-440.
Abstract:
A new calculated method of the position area to radar is presented. The method is that the Circular Error Probability(CEP) of the smaller area is calculated using the parameters of the place of two and three radar devices. When CEP of some smaller area is less than or equal to the given value, the area belongs to the whole position area. By means of the method, the position area is gained and the position precision can be obtained.
A new calculated method of the position area to radar is presented. The method is that the Circular Error Probability(CEP) of the smaller area is calculated using the parameters of the place of two and three radar devices. When CEP of some smaller area is less than or equal to the given value, the area belongs to the whole position area. By means of the method, the position area is gained and the position precision can be obtained.
2005, 27(3): 441-444.
Abstract:
This paper first presents the unified network model associated antennas with loaded networks, which shows that the loaded circuit networks and the antennas (field networks) are unified by the generalized matrix Ohm’s law. Based on the theory of the unified network model, this paper give a rigorous study of the Five-element Circle Array for Direction Finding (FCADF) by using the Method of Moments (MoM). The results show that the interaction between circuits and fields is introduced by loading a matching and compensating network, which compensates the effect of mutual coupling between array elements, realizes impedance matching, and improves the non-circular degree of radiated pattern and the precision of direction finding. In addition, the local resonant phenomenon in FCAFD is effectively restrained by loading the circuit network.
This paper first presents the unified network model associated antennas with loaded networks, which shows that the loaded circuit networks and the antennas (field networks) are unified by the generalized matrix Ohm’s law. Based on the theory of the unified network model, this paper give a rigorous study of the Five-element Circle Array for Direction Finding (FCADF) by using the Method of Moments (MoM). The results show that the interaction between circuits and fields is introduced by loading a matching and compensating network, which compensates the effect of mutual coupling between array elements, realizes impedance matching, and improves the non-circular degree of radiated pattern and the precision of direction finding. In addition, the local resonant phenomenon in FCAFD is effectively restrained by loading the circuit network.
2005, 27(3): 445-448.
Abstract:
In this paper, a new coding approach to remote sensing images is proposed according to the statistical characteristic of remote sensing images data. The approach is based on an improved embedded, zeroblock-based, image wavelet transform coding algorithm. A modified quadtree algorithm and a new orderings strategy of List of Insignificant Sets (LIS) are proposed in new algorithm. By improving in this proposal, the performance of the embedded wavelet image coder is increased and a higher computing efficiency is obtained. The proposed algorithm exhibits a lower complexity, a more efficient compression ratio and a higher PSNR than SPIHT and SPECK. Experimental results show that the proposed method increases the PSNR by about 0.3dB over SPIHT, and beats SPIHT by 35% at the CPU time.
In this paper, a new coding approach to remote sensing images is proposed according to the statistical characteristic of remote sensing images data. The approach is based on an improved embedded, zeroblock-based, image wavelet transform coding algorithm. A modified quadtree algorithm and a new orderings strategy of List of Insignificant Sets (LIS) are proposed in new algorithm. By improving in this proposal, the performance of the embedded wavelet image coder is increased and a higher computing efficiency is obtained. The proposed algorithm exhibits a lower complexity, a more efficient compression ratio and a higher PSNR than SPIHT and SPECK. Experimental results show that the proposed method increases the PSNR by about 0.3dB over SPIHT, and beats SPIHT by 35% at the CPU time.
2005, 27(3): 449-453.
Abstract:
Power consumption has to be taken into consideration in an applied SAR real-time processor. The power consumption is measured before and after clock-gating method had been applied to DSP, SBSRAM and FPGA of an air-borne SAR real-time preprocessor board respectively by software. It has been proved that clock-gating method is feasible for low power design in the SAR especially the future space-borne SAR real-time processor.
Power consumption has to be taken into consideration in an applied SAR real-time processor. The power consumption is measured before and after clock-gating method had been applied to DSP, SBSRAM and FPGA of an air-borne SAR real-time preprocessor board respectively by software. It has been proved that clock-gating method is feasible for low power design in the SAR especially the future space-borne SAR real-time processor.
2005, 27(3): 454-457.
Abstract:
The wavenumber domain algorithm (ur-k algorithm for short) has the ability to process wide-beam SAR data because it has the ability to handle the range-azimuth coupling correctly. However, because the traditional nj-k algorithm can not integrate with the motion compensation approach, it sometimes results in bad image. Some improvement of the traditional ra-k algorithm is presented in this paper, that is, the deconvolution is used to separate the range migration correction from the azimuth compression, and then the sub-aperture and autofocus approach are applied to the ro-k algorithm, which makes the improved nj-k algorithm more practicable. At the end of this paper, a set of P-band wide-beam SAR data is processed by the improved tn-k algorithm, and the resultant image quality is obviously increased.
The wavenumber domain algorithm (ur-k algorithm for short) has the ability to process wide-beam SAR data because it has the ability to handle the range-azimuth coupling correctly. However, because the traditional nj-k algorithm can not integrate with the motion compensation approach, it sometimes results in bad image. Some improvement of the traditional ra-k algorithm is presented in this paper, that is, the deconvolution is used to separate the range migration correction from the azimuth compression, and then the sub-aperture and autofocus approach are applied to the ro-k algorithm, which makes the improved nj-k algorithm more practicable. At the end of this paper, a set of P-band wide-beam SAR data is processed by the improved tn-k algorithm, and the resultant image quality is obviously increased.
2005, 27(3): 458-461.
Abstract:
Phase unwrapping is so important that it determines the precision of the DEM of INSAR directly. To improve the precision of phase unwrapping, a new method based on method of Goldstein is given. Qualification data are produced with the inconsistent points to determine the optimal integral path. With this method, the error is restricted in a small area, the operation keeps fast, and the precision is improved. With the help of simulation of INSAR data, the capability of the two methods is compared. The result of phase unwrapping of ERS1/ERS2-SAR data shows the capability of the new method.
Phase unwrapping is so important that it determines the precision of the DEM of INSAR directly. To improve the precision of phase unwrapping, a new method based on method of Goldstein is given. Qualification data are produced with the inconsistent points to determine the optimal integral path. With this method, the error is restricted in a small area, the operation keeps fast, and the precision is improved. With the help of simulation of INSAR data, the capability of the two methods is compared. The result of phase unwrapping of ERS1/ERS2-SAR data shows the capability of the new method.
2005, 27(3): 462-466.
Abstract:
The classification mechanism of the kernel-based methods in pattern recognition, i.e. SVMs, nonPCA, and nonLDA, are analyzed in detail in this paper. The range profiles of radar target are recognized by the kernel-based methods. The results of the simulation on three radar target show that SVMs is more effective than nonPCA and nonLDA, and a sound explanation for the results is given too.
The classification mechanism of the kernel-based methods in pattern recognition, i.e. SVMs, nonPCA, and nonLDA, are analyzed in detail in this paper. The range profiles of radar target are recognized by the kernel-based methods. The results of the simulation on three radar target show that SVMs is more effective than nonPCA and nonLDA, and a sound explanation for the results is given too.
2005, 27(3): 467-470.
Abstract:
Estimation of Distribution Algorithms (EDAs) available in continuous domains are based on non-generic Gaussian networks. The computational cost for learning this kind of networks is very great, moreover the low accuracy of Ihe joint pdf will be resulted because the greedy algorithm is used to learn the Gaussian networks. To overcome these disadvantages, an Estimation of Distribution Algorithm based on generic Gaussian Networks (GN-EDA) is presented. Ft leads to the low computational cost by no structure learning of Gaussian networks. In the meanwhile, a generic Gaussian network is not an approximate one, so the joint pdf is of high accuracy. Due to an effective sampling is adopted, the computational cost for parameters learning is great reduced. The experimental results show that GN-EDA achieves a more stable performance and a stronger ability in searching the global optima.
Estimation of Distribution Algorithms (EDAs) available in continuous domains are based on non-generic Gaussian networks. The computational cost for learning this kind of networks is very great, moreover the low accuracy of Ihe joint pdf will be resulted because the greedy algorithm is used to learn the Gaussian networks. To overcome these disadvantages, an Estimation of Distribution Algorithm based on generic Gaussian Networks (GN-EDA) is presented. Ft leads to the low computational cost by no structure learning of Gaussian networks. In the meanwhile, a generic Gaussian network is not an approximate one, so the joint pdf is of high accuracy. Due to an effective sampling is adopted, the computational cost for parameters learning is great reduced. The experimental results show that GN-EDA achieves a more stable performance and a stronger ability in searching the global optima.
2005, 27(3): 471-473.
Abstract:
Tracking fusion with dissimilar sensors, which is a challenge work in multisensor fusion, is studied. Under the condition of general correlated measurement noises, the centralized and distributed tracking fusion question is investigated based on linear unbiased minimum variance estimation theory. The basic algorithms of measurement fusion and state vector fusion are presented in linear system with dissimilar sensors by the way of sequential filtering. These algorithms involve with not only the correlated measurement noises but also the configuration difference in local sensors, so information about multi-sensors fusion is increased. Through a simulation example it is indicated that the results of proposed algorithm is better than that classic ones where the measurement noises and processing noises are assumed to be uncorrelated.
Tracking fusion with dissimilar sensors, which is a challenge work in multisensor fusion, is studied. Under the condition of general correlated measurement noises, the centralized and distributed tracking fusion question is investigated based on linear unbiased minimum variance estimation theory. The basic algorithms of measurement fusion and state vector fusion are presented in linear system with dissimilar sensors by the way of sequential filtering. These algorithms involve with not only the correlated measurement noises but also the configuration difference in local sensors, so information about multi-sensors fusion is increased. Through a simulation example it is indicated that the results of proposed algorithm is better than that classic ones where the measurement noises and processing noises are assumed to be uncorrelated.
2005, 27(3): 474-477.
Abstract:
The data structure in JPEG2000 compressed domain is firstly analyzed. The concept of information tree and a novel tree-distance measurement are then proposed. Finally, a new image retrieval method in JPEG2000 compressed domain is proposed. Experimental results show its potential in the research of compressed domain image retrieval techniques.
The data structure in JPEG2000 compressed domain is firstly analyzed. The concept of information tree and a novel tree-distance measurement are then proposed. Finally, a new image retrieval method in JPEG2000 compressed domain is proposed. Experimental results show its potential in the research of compressed domain image retrieval techniques.
2005, 27(3): 478-482.
Abstract:
A new blind intelligent image watermarking technique proposed in this paper adopts intelligent information disposal-independent component analysis. The characteristics of the human visual system are incorporated into the watermark embedding and a closed-loop embedding in discrete wavelet transform domain is proposed. The watermark is rearranged by chaotic before embedded, and it can be detected and extracted correctly not merely be detected without any information about the original image, watermark and attack. It can also extract the multiple embedded watermarks. The accuracy of watermark extraction depends on the key and the statistical independence between the original images and watermark. Experimental results demonstrate that the proposed intelligent watermarking technique is robust with respect to traditional image processing including cropping, filtering, image compression and geometric distortions such as rotation, scaling. It even has a good robustness against combination of several attacks. All attacks are produced by popular watermark test software-Stirmark.
A new blind intelligent image watermarking technique proposed in this paper adopts intelligent information disposal-independent component analysis. The characteristics of the human visual system are incorporated into the watermark embedding and a closed-loop embedding in discrete wavelet transform domain is proposed. The watermark is rearranged by chaotic before embedded, and it can be detected and extracted correctly not merely be detected without any information about the original image, watermark and attack. It can also extract the multiple embedded watermarks. The accuracy of watermark extraction depends on the key and the statistical independence between the original images and watermark. Experimental results demonstrate that the proposed intelligent watermarking technique is robust with respect to traditional image processing including cropping, filtering, image compression and geometric distortions such as rotation, scaling. It even has a good robustness against combination of several attacks. All attacks are produced by popular watermark test software-Stirmark.
2005, 27(3): 483-486.
Abstract:
After analyzing the classic 2-D steady-state trajectory method for multistage depressed collectors simulation and design and its limitation, a novel method of full three-dimensional (3-D) dynamic PIC simulation using MAFIA a three dimensional electromagnetic finite integration code and large signal analysis code is presented. The simplified formula of collector efficiency is also put forward. The process and primary result of this method are described, which shows that the simulation results close to the experimental data within acceptable error range. It is the new approach to accurate simulation and engineering design and optimizing of multistage depressed collectors. Simultaneausly, the deficiency of this method is also pointed out.
After analyzing the classic 2-D steady-state trajectory method for multistage depressed collectors simulation and design and its limitation, a novel method of full three-dimensional (3-D) dynamic PIC simulation using MAFIA a three dimensional electromagnetic finite integration code and large signal analysis code is presented. The simplified formula of collector efficiency is also put forward. The process and primary result of this method are described, which shows that the simulation results close to the experimental data within acceptable error range. It is the new approach to accurate simulation and engineering design and optimizing of multistage depressed collectors. Simultaneausly, the deficiency of this method is also pointed out.
2005, 27(3): 487-491.
Abstract:
This paper presents a improved K-NN algorithm. The CURE clustering is carried out to select the subset of the training set. It can reduce the volume of the training set and omit the outlier. Therefore it can lead both to computational efficiency and to higher classification accuracy. In the algorithm, the weights of each feature are learned using neural network. The feature weights are used in the nearest measure computation such that the important features contribute more in the nearest measure. Experiments on several UCI databases and practical data sets show the efficiency of the algorithm.
This paper presents a improved K-NN algorithm. The CURE clustering is carried out to select the subset of the training set. It can reduce the volume of the training set and omit the outlier. Therefore it can lead both to computational efficiency and to higher classification accuracy. In the algorithm, the weights of each feature are learned using neural network. The feature weights are used in the nearest measure computation such that the important features contribute more in the nearest measure. Experiments on several UCI databases and practical data sets show the efficiency of the algorithm.
2005, 27(3): 492-494.
Abstract:
Based on Linear Frequency Modulated (LFM) pulse compression signal, a system which has two resolution with 1200MHz carrier and 200MHz and 66.7MHz bandwidth, is designed and implemented. According to the measurement results, the spurious signals involved in the system output as well as the harmonic signals are lower than - 55dB, the ripple in the band is below 2dB, and pulse compression Ratio of Mainlobe to Sidelobe (RMS) reaches 30dB. The system is quite stable and its performance meets the requirement of actual application.
Based on Linear Frequency Modulated (LFM) pulse compression signal, a system which has two resolution with 1200MHz carrier and 200MHz and 66.7MHz bandwidth, is designed and implemented. According to the measurement results, the spurious signals involved in the system output as well as the harmonic signals are lower than - 55dB, the ripple in the band is below 2dB, and pulse compression Ratio of Mainlobe to Sidelobe (RMS) reaches 30dB. The system is quite stable and its performance meets the requirement of actual application.
2005, 27(3): 495-497.
Abstract:
This paper presents a realization scheme based on shifting and adding operation, sub-expression, and multiplier module. First it gives the definition of partly-common sub-expression. Then it introduces a matrix used for searching proper partly-common sub-expressions. Through the comparison, it is found that this presented realization scheme will use less hardware than ordinary schemes. In addition, theoretic analysis gives us a conclusion that this method especially fits for filters with many coefficients.
This paper presents a realization scheme based on shifting and adding operation, sub-expression, and multiplier module. First it gives the definition of partly-common sub-expression. Then it introduces a matrix used for searching proper partly-common sub-expressions. Through the comparison, it is found that this presented realization scheme will use less hardware than ordinary schemes. In addition, theoretic analysis gives us a conclusion that this method especially fits for filters with many coefficients.
2005, 27(3): 498-501.
Abstract:
Based on a micro-payment model of Unbalanced One-way Binary Tree (UOBT), this paper proposes an efficient protocol for mutual authentication and electronic payment with the capability of arbitrating disputed bills. This protocal can protect subscribers from incorrect service charges and provide service providers legal evidences to collect bills that are denied.
Based on a micro-payment model of Unbalanced One-way Binary Tree (UOBT), this paper proposes an efficient protocol for mutual authentication and electronic payment with the capability of arbitrating disputed bills. This protocal can protect subscribers from incorrect service charges and provide service providers legal evidences to collect bills that are denied.
2005, 27(3): 502-504.
Abstract:
A new preconditioning method based on neighbor element which has distinct physical background is presented in this paper. The dominant information of impedance matrix is fully considered in the neighbor element preconditioner. The preconditioner is generated from the targets geometry structure and not from the matrix element, which assured the computational complexity for generating the preconditioner is only O(N). This preconditioning method combined with conjugate-gradient method is used to solve the integral-equations generated from a base station antenna with MoM method in this paper. Numerical results are presented to demonstrate the validity of this method.
A new preconditioning method based on neighbor element which has distinct physical background is presented in this paper. The dominant information of impedance matrix is fully considered in the neighbor element preconditioner. The preconditioner is generated from the targets geometry structure and not from the matrix element, which assured the computational complexity for generating the preconditioner is only O(N). This preconditioning method combined with conjugate-gradient method is used to solve the integral-equations generated from a base station antenna with MoM method in this paper. Numerical results are presented to demonstrate the validity of this method.
