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2005 Vol. 27, No. 11
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2005, 27(11): 1681-1685.
Abstract:
In the design of cellular radio systems, power control methods based on signal-to-interference ratio (SIR) measurement have been used widely. This paper proposes distributed power control (DPC) methods based on SIR measurement in Multiple-Input Multiple-Output (MIMO) antenna cellular systems. The methods control the transmitter power of mobile stations or base stations with one of the following two objectives: (1) to minimize the averaged SIR outage probability over all base stations or mobile stations and (2) to minimize the averaged transmitter power while satisfying the specified SIR requirements for all links. Numerical study shows that the DPC methods proposed in this paper can effectively lower SIR outage probability and transmitter power at low computation complexity.
In the design of cellular radio systems, power control methods based on signal-to-interference ratio (SIR) measurement have been used widely. This paper proposes distributed power control (DPC) methods based on SIR measurement in Multiple-Input Multiple-Output (MIMO) antenna cellular systems. The methods control the transmitter power of mobile stations or base stations with one of the following two objectives: (1) to minimize the averaged SIR outage probability over all base stations or mobile stations and (2) to minimize the averaged transmitter power while satisfying the specified SIR requirements for all links. Numerical study shows that the DPC methods proposed in this paper can effectively lower SIR outage probability and transmitter power at low computation complexity.
2005, 27(11): 1686-1690.
Abstract:
An advanced Hybrid ARQ (HARQ) technique applicable to QAM is presented in this paper, which employs signal constellation rearrangement to average the variations in bit reliabilities caused by QAM signal constellation. The presented scheme employs 4 constellation mapping rules for 64-QAM, and can achieve a noticeable gain in HARQ performance as well as a reduction in complexity compared to the existing constellation rearrangement scheme.
An advanced Hybrid ARQ (HARQ) technique applicable to QAM is presented in this paper, which employs signal constellation rearrangement to average the variations in bit reliabilities caused by QAM signal constellation. The presented scheme employs 4 constellation mapping rules for 64-QAM, and can achieve a noticeable gain in HARQ performance as well as a reduction in complexity compared to the existing constellation rearrangement scheme.
2005, 27(11): 1691-1694.
Abstract:
Iterative multi-user detection with channel decoding is applied to MC-CDMA, the multi-user detector is implemented as successive interference canceller with post-minimum mean squared error filtering. A new channel estimation approach based on expectation maximizatiom algorithm is proposed for the iterative detection. The proposed approach decreases the complexity of computation. Simulation shows that the proposed receiver approach single-user performance at very high channel load.
Iterative multi-user detection with channel decoding is applied to MC-CDMA, the multi-user detector is implemented as successive interference canceller with post-minimum mean squared error filtering. A new channel estimation approach based on expectation maximizatiom algorithm is proposed for the iterative detection. The proposed approach decreases the complexity of computation. Simulation shows that the proposed receiver approach single-user performance at very high channel load.
2005, 27(11): 1695-1698.
Abstract:
By Spectrum Spreading, the multi-path signals can be distinguished and received by RAKE receiver, and spectrum spreading is an efficient way to overcome multi-path fading. Time spreading can implement RAKE diversity receiving in frequency domain. But time spreading comes with serious ISI in fading channels. Synchronous time spreading can overcome the ISI. By channel decomposing, the signal can be received by diversity receiver, so good performance can be achieved. To achieve 10-4 BER performance, the SNR required in time-varying fading channels by our algorithm with 1024 bit spreading length is only 1.4dB more than that in AWGN channels without diversity.
By Spectrum Spreading, the multi-path signals can be distinguished and received by RAKE receiver, and spectrum spreading is an efficient way to overcome multi-path fading. Time spreading can implement RAKE diversity receiving in frequency domain. But time spreading comes with serious ISI in fading channels. Synchronous time spreading can overcome the ISI. By channel decomposing, the signal can be received by diversity receiver, so good performance can be achieved. To achieve 10-4 BER performance, the SNR required in time-varying fading channels by our algorithm with 1024 bit spreading length is only 1.4dB more than that in AWGN channels without diversity.
2005, 27(11): 1699-1703.
Abstract:
Based on the property of OFDM systems, this paper discusses the feasibility of Wiener LMS algorithm in OFDM systems, and derives the frequency expression of the WLMS channel prediction algorithm for OFDM systems. The performance of the algorithm is greatly improved by using a frequency domain filter, which is derived based on the correlations of channel response in frequency domain, in each iteration. The simulation results show that the performance of uncoded Symbol Error Rate (SER) can reach the bound of ideal channel estimation at the proper step size.
Based on the property of OFDM systems, this paper discusses the feasibility of Wiener LMS algorithm in OFDM systems, and derives the frequency expression of the WLMS channel prediction algorithm for OFDM systems. The performance of the algorithm is greatly improved by using a frequency domain filter, which is derived based on the correlations of channel response in frequency domain, in each iteration. The simulation results show that the performance of uncoded Symbol Error Rate (SER) can reach the bound of ideal channel estimation at the proper step size.
2005, 27(11): 1703-1709.
Abstract:
This paper proposes a novel M-ary spread spectrum receiver scheme based on time-frequency transform domain. At the transmitter of the system, the M spreading codes of each user are generated by circularly shifting the prototype spreading code. At the receiver, a time-frequency transform domain orthogonal matched-filter is employed to noncoherently despread and demodulate the received signals. The proposed scheme reduces computation and spreading codes selection difficulty of M-ary spread spectrum system remarkably. The BER performances of the receiver for single user and multiuser are analyzed, and the computations for three kinds of M-ary despreading methods are compared. The results show that the proposed scheme has better BER performance and lower computation complexity than of traditional M-ary systems.
This paper proposes a novel M-ary spread spectrum receiver scheme based on time-frequency transform domain. At the transmitter of the system, the M spreading codes of each user are generated by circularly shifting the prototype spreading code. At the receiver, a time-frequency transform domain orthogonal matched-filter is employed to noncoherently despread and demodulate the received signals. The proposed scheme reduces computation and spreading codes selection difficulty of M-ary spread spectrum system remarkably. The BER performances of the receiver for single user and multiuser are analyzed, and the computations for three kinds of M-ary despreading methods are compared. The results show that the proposed scheme has better BER performance and lower computation complexity than of traditional M-ary systems.
2005, 27(11): 1710-1713.
Abstract:
Further investigation is given to a kind of carrier frequency offset (CFO) blind estimation algorithm based on time domain received signal reconstruction in OFDM systems, and the four aspects that affect the estimation accuracy are analyzed. For minimizing the residual carrier frequency offset, a kind of decision-directed carrier frequency synchronization loop is given by introducing a feedback factor into the frequency compensation. Better carrier frequency tracking performance can be gotten by adjusting the loop gain. The residual frequency offset can be restricted within 1% of the carrier spacing even if lager frequency drift exists, if bit SNR reaches 9dB.
Further investigation is given to a kind of carrier frequency offset (CFO) blind estimation algorithm based on time domain received signal reconstruction in OFDM systems, and the four aspects that affect the estimation accuracy are analyzed. For minimizing the residual carrier frequency offset, a kind of decision-directed carrier frequency synchronization loop is given by introducing a feedback factor into the frequency compensation. Better carrier frequency tracking performance can be gotten by adjusting the loop gain. The residual frequency offset can be restricted within 1% of the carrier spacing even if lager frequency drift exists, if bit SNR reaches 9dB.
2005, 27(11): 1717-1721.
Abstract:
A major drawback related to the Block-based Discrete Cosine Transform(BDCT) for image and video compression is that the decoded images, especially at very low bit rates,exhibit highly noticeable blocking artifact near the block boundaries. In this paper, a deblocking algorithm based on Human Visual System (HVS) is proposed. For smooth regions, one dimension DCT domains filter is applied to reduce the blocking artifacts, but for texture regions a spatial filter is used. The experimental results show that the proposed algorithm reduces the blocking artifacts effectively and preserves the original edges faithfully.
A major drawback related to the Block-based Discrete Cosine Transform(BDCT) for image and video compression is that the decoded images, especially at very low bit rates,exhibit highly noticeable blocking artifact near the block boundaries. In this paper, a deblocking algorithm based on Human Visual System (HVS) is proposed. For smooth regions, one dimension DCT domains filter is applied to reduce the blocking artifacts, but for texture regions a spatial filter is used. The experimental results show that the proposed algorithm reduces the blocking artifacts effectively and preserves the original edges faithfully.
2005, 27(11): 1722-1725.
Abstract:
In this paper, a novel image denoising method based on statistical mixture model in wavelet domain is proposed. Firstly, the wavelet coefficients are classified as significant and insignificant coefficients by using interscale statistical model. Secondly, Maximum A Posteriori (MAP) estimator based on intrascale statistical model is used to restore the noisy wavelet image coefficients. A completive algorithm is presented to implement this idea. Experimental results and analysis are given to demonstrate the validity and effectiveness of the proposed method.
In this paper, a novel image denoising method based on statistical mixture model in wavelet domain is proposed. Firstly, the wavelet coefficients are classified as significant and insignificant coefficients by using interscale statistical model. Secondly, Maximum A Posteriori (MAP) estimator based on intrascale statistical model is used to restore the noisy wavelet image coefficients. A completive algorithm is presented to implement this idea. Experimental results and analysis are given to demonstrate the validity and effectiveness of the proposed method.
2005, 27(11): 1726-1731.
Abstract:
Continuous Phase Modulated (CPM) signals play a prominent role in modern satellite communication systems and mobile communication systems due to their constant envelope property and bandwidth efficiencies. However, there was no much comprehensive reference concerning the cyclostationarity of the large family of CPM. In this paper, the general band-pass cyclic spectral representations of the continuous phase modulation are derived and analyzed in detail based on the analytical expression of the corresponding base-band cyclic spectra; as well, the relation between cyclic frequency and carrier frequency, code width, peak frequency deviation is obtained with the different modulation indexes. These conclusions are proved by the computer simulations.
Continuous Phase Modulated (CPM) signals play a prominent role in modern satellite communication systems and mobile communication systems due to their constant envelope property and bandwidth efficiencies. However, there was no much comprehensive reference concerning the cyclostationarity of the large family of CPM. In this paper, the general band-pass cyclic spectral representations of the continuous phase modulation are derived and analyzed in detail based on the analytical expression of the corresponding base-band cyclic spectra; as well, the relation between cyclic frequency and carrier frequency, code width, peak frequency deviation is obtained with the different modulation indexes. These conclusions are proved by the computer simulations.
2005, 27(11): 1732-1736.
Abstract:
A class of Convolutional Space-Time Code(CSTC) is designed for Serially Concatenated Space-Time Code(SCSTC) with an arbitrary number of transmit antennas. The most apparent characteristic of the designed SCSTC is that the data rate increases with the number of transmit antennas. The concept of EXIT (EXtrinsic Information Transfer) Chart is generalized to multiple antenna system to study the convergence of SCSTC. Compared with the available SCSTC with space-time trellis code as the inner code, the new SCSTC can converge earlier and have improved performance.
A class of Convolutional Space-Time Code(CSTC) is designed for Serially Concatenated Space-Time Code(SCSTC) with an arbitrary number of transmit antennas. The most apparent characteristic of the designed SCSTC is that the data rate increases with the number of transmit antennas. The concept of EXIT (EXtrinsic Information Transfer) Chart is generalized to multiple antenna system to study the convergence of SCSTC. Compared with the available SCSTC with space-time trellis code as the inner code, the new SCSTC can converge earlier and have improved performance.
2005, 27(11): 1737-1740.
Abstract:
A new anonymous authentication scheme with traceable identity is proposed. This scheme has the following advantages: (1) It is easy for users to dynamically join and leave, the only thing needs to do is manager add or delete the relevant data of users. (2) The prover can unrestrictedly choose a group of users and declare that himself belong to it, so he can choose his anonymous scope initiatively and freely. (3) In the process of trace the identity of prover, the right of manager is restricted, he needs cooperation with the verifiers to reveal the identity of the prover. In the aspect of against outside attack and masking attack, compared with the scheme 1-resilient of Boneh(1999), this scheme can realize arbitrary resilience .
A new anonymous authentication scheme with traceable identity is proposed. This scheme has the following advantages: (1) It is easy for users to dynamically join and leave, the only thing needs to do is manager add or delete the relevant data of users. (2) The prover can unrestrictedly choose a group of users and declare that himself belong to it, so he can choose his anonymous scope initiatively and freely. (3) In the process of trace the identity of prover, the right of manager is restricted, he needs cooperation with the verifiers to reveal the identity of the prover. In the aspect of against outside attack and masking attack, compared with the scheme 1-resilient of Boneh(1999), this scheme can realize arbitrary resilience .
2005, 27(11): 1741-1744.
Abstract:
The performance analysis of chaotic Frequency-Hopping (FH) sequences, which are generated by quantization function and reshaping operation based on chaotic map, is presented in this paper. Theory analysis and performance experimental at results show that this sequence is Bernoulli sequence and its Hamming correlation is shown to be Poisson distributed. It is comparable to other FH sequences on the properties of uniform distribution, Hamming correlation and linear complexity when they have the same number of frequency slots and the same period, but much less requirements of iterative operation. It can be concluded that more FH sequences can be generated by this method and they are suitable for FH code-division multiple-access systems.
The performance analysis of chaotic Frequency-Hopping (FH) sequences, which are generated by quantization function and reshaping operation based on chaotic map, is presented in this paper. Theory analysis and performance experimental at results show that this sequence is Bernoulli sequence and its Hamming correlation is shown to be Poisson distributed. It is comparable to other FH sequences on the properties of uniform distribution, Hamming correlation and linear complexity when they have the same number of frequency slots and the same period, but much less requirements of iterative operation. It can be concluded that more FH sequences can be generated by this method and they are suitable for FH code-division multiple-access systems.
2005, 27(11): 1745-1749.
Abstract:
In order to avoid computing elements inverses in the ring Z(N) since they may not exit, a new RSA threshold group signature scheme based on modified Shamirs secret sharing solution is proposed. Differing from the old schemes based on Lagrange interpolation solution in which fraction arithmetic operations leading to the computation of elements inverses in Z(N) should be handled, this new scheme reconstructs its group secret key through series of integer arithmetic operations in integral matrixes, by which it can efficiently avoid the computation of any elements inverse in any algebraic structure (such as Z(N)), and can further avoid algebraic extensions. Therefore, this new scheme is more efficient and convenient than the old ones.
In order to avoid computing elements inverses in the ring Z(N) since they may not exit, a new RSA threshold group signature scheme based on modified Shamirs secret sharing solution is proposed. Differing from the old schemes based on Lagrange interpolation solution in which fraction arithmetic operations leading to the computation of elements inverses in Z(N) should be handled, this new scheme reconstructs its group secret key through series of integer arithmetic operations in integral matrixes, by which it can efficiently avoid the computation of any elements inverse in any algebraic structure (such as Z(N)), and can further avoid algebraic extensions. Therefore, this new scheme is more efficient and convenient than the old ones.
2005, 27(11): 1750-1754.
Abstract:
In this paper, a new method for 2D adaptive lifting wavelet transform is proposed, which suite for the task of image compression applications. It is based on a update lifting operator and a nonlinear prediction lifting operator according with certain local characteristic and statistical information of an image. Some experiment results show that the entropy of the coefficients in the transform domain obtained with this new method is smaller than that obtained with other adaptive wavelet transform method and non-adaptive wavelet transform, which can avoid quantization with the image detail signals being zero(or almost zero) at the smooth gray-level variation areas at big probability.
In this paper, a new method for 2D adaptive lifting wavelet transform is proposed, which suite for the task of image compression applications. It is based on a update lifting operator and a nonlinear prediction lifting operator according with certain local characteristic and statistical information of an image. Some experiment results show that the entropy of the coefficients in the transform domain obtained with this new method is smaller than that obtained with other adaptive wavelet transform method and non-adaptive wavelet transform, which can avoid quantization with the image detail signals being zero(or almost zero) at the smooth gray-level variation areas at big probability.
2005, 27(11): 1755-1759.
Abstract:
This paper provides a new design approach based on a Neural Networks Algorithm(NNA). According to the amplitude-frequency response characteristics of 2-D FIR linear-phase filters ,the NNA is established .Using the NNA,the designed filter coefficients can be obtained from the specified amplitude-frequency responses.To ensure stability of the NNA, the convergence theorem of the NNA is presented and proved. Two examples including circularly-symmetric and quadrately-symmetric 2-D lowpass linear-phase FIR filtsrs are also given to illustrate the effectiveness of the NNA-based design approach,and the results show that the ripple is considerably small in passband and in stopband,and the NNA-based method is of strong stability and requires significantly little amount of computations.Therefore,the optimal design approach is effective and excellent in the design field of 2-D linear phase FIR digital filters.
This paper provides a new design approach based on a Neural Networks Algorithm(NNA). According to the amplitude-frequency response characteristics of 2-D FIR linear-phase filters ,the NNA is established .Using the NNA,the designed filter coefficients can be obtained from the specified amplitude-frequency responses.To ensure stability of the NNA, the convergence theorem of the NNA is presented and proved. Two examples including circularly-symmetric and quadrately-symmetric 2-D lowpass linear-phase FIR filtsrs are also given to illustrate the effectiveness of the NNA-based design approach,and the results show that the ripple is considerably small in passband and in stopband,and the NNA-based method is of strong stability and requires significantly little amount of computations.Therefore,the optimal design approach is effective and excellent in the design field of 2-D linear phase FIR digital filters.
2005, 27(11): 1760-1764.
Abstract:
Wideband FM signal occupies a wide band in frequency domain and has a time-varying direction vector. Therefore it is difficult to estimate its DOA, particularly the method to estimate 2-D DOA of coherent wideband FM signals has not been reported. This paper constructs a novel time-frequency equation based on STFT and the time-frequency distribution of wideband FM signals. The structure of rectangular or array and the SVD based on the stack of rectangular sub-arrays are also exploited to estimate 2-D DOA of coherent wideband FM signals. Theoretical predictions and simulation results indicate the efficacy of the proposed algorithm.
Wideband FM signal occupies a wide band in frequency domain and has a time-varying direction vector. Therefore it is difficult to estimate its DOA, particularly the method to estimate 2-D DOA of coherent wideband FM signals has not been reported. This paper constructs a novel time-frequency equation based on STFT and the time-frequency distribution of wideband FM signals. The structure of rectangular or array and the SVD based on the stack of rectangular sub-arrays are also exploited to estimate 2-D DOA of coherent wideband FM signals. Theoretical predictions and simulation results indicate the efficacy of the proposed algorithm.
2005, 27(11): 1765-1769.
Abstract:
This paper presents a novel method to design prefilters starting from analysis scaling functions and utilizing the algebraic polynomial interpolation. In the case of uniform sampling, the obtained prefilters are time-invariant and its coefficients are linear combinations of the moments of the analysis scaling function. Its approximate order is dependent on the support length of analysis scaling function rather than its degree of regularity. This method provides two outstanding advantages: the prefilters can be designed with higher approximate orders than the existing prefilters, e.g., the special prefilters from the values at integer points of the synthesis scaling function and the prefilters from prescaling function method; moreover, the method is easy to be extended to the case of nonuniform sampling, in which the prefilters are time-variant and their approximate order is dependent on the support length of analysis scaling function as well as the distribution of sample points.
This paper presents a novel method to design prefilters starting from analysis scaling functions and utilizing the algebraic polynomial interpolation. In the case of uniform sampling, the obtained prefilters are time-invariant and its coefficients are linear combinations of the moments of the analysis scaling function. Its approximate order is dependent on the support length of analysis scaling function rather than its degree of regularity. This method provides two outstanding advantages: the prefilters can be designed with higher approximate orders than the existing prefilters, e.g., the special prefilters from the values at integer points of the synthesis scaling function and the prefilters from prescaling function method; moreover, the method is easy to be extended to the case of nonuniform sampling, in which the prefilters are time-variant and their approximate order is dependent on the support length of analysis scaling function as well as the distribution of sample points.
2005, 27(11): 1770-1773.
Abstract:
Object detection has been a difficult problem in remote sensing community for a long time. To process very large image make object detection even more difficult. A method for detecting airport ROI(Region Of Interest) is proposed, which is based on feature space analysis that can fast locate airport. The image can be read into blocks for extracting features respectively and simultaneously. The extracted features are analyzed by mean-shift method, and eventually the airport regions can be located. The proposed ROI detecting method has strong robustness, autonomy and parallelism. It can drastically decrease the difficulty of processing very large images.
Object detection has been a difficult problem in remote sensing community for a long time. To process very large image make object detection even more difficult. A method for detecting airport ROI(Region Of Interest) is proposed, which is based on feature space analysis that can fast locate airport. The image can be read into blocks for extracting features respectively and simultaneously. The extracted features are analyzed by mean-shift method, and eventually the airport regions can be located. The proposed ROI detecting method has strong robustness, autonomy and parallelism. It can drastically decrease the difficulty of processing very large images.
2005, 27(11): 1774-1777.
Abstract:
In this paper, a new wavelet invariant moment based on image projections is proposed. Firstly, Radon transform is used to project the image to 1-D space. Then, a translation and scaling invariant adaptive 1-D wavelet transform is introduced, and the projection data is transformed to wavelet domain to get a feature matrix with translation and scaling invariance. Since the feature matrix is influenced to be cyclically shifted of rows when image rotates, Singular Value Decomposition (SVD) is employed and singular value vector is invariant under image translation, scaling and rotation. Simulation results are given to obtain insight into the efficiencies offered by this method.
In this paper, a new wavelet invariant moment based on image projections is proposed. Firstly, Radon transform is used to project the image to 1-D space. Then, a translation and scaling invariant adaptive 1-D wavelet transform is introduced, and the projection data is transformed to wavelet domain to get a feature matrix with translation and scaling invariance. Since the feature matrix is influenced to be cyclically shifted of rows when image rotates, Singular Value Decomposition (SVD) is employed and singular value vector is invariant under image translation, scaling and rotation. Simulation results are given to obtain insight into the efficiencies offered by this method.
2005, 27(11): 1778-1781.
Abstract:
Skin color is an important feature for face detection in color images. Usually by applying a statistical skin model, possible skin region can be segmented. However, the output can not be as accurate as expected. Besides, simple 2D model, e.g. CbCr, can not present the real skin point distribution. So this paper presents a 3D CrCbCg model to describe skin distribution more precisely. Meanwhile, considering skin points in a specific image have a relative stable distribution, a cluster-based skin model is presented to remove background points which are wrongly retained by the general model. Because of applying the characteristic of each specific image, this algorithm can effectively improve the performance and accuracy of skin model. Experimental result shows that this algorithm can achieve satisfied results for over 95% images, including obviously improved images for over 70% .
Skin color is an important feature for face detection in color images. Usually by applying a statistical skin model, possible skin region can be segmented. However, the output can not be as accurate as expected. Besides, simple 2D model, e.g. CbCr, can not present the real skin point distribution. So this paper presents a 3D CrCbCg model to describe skin distribution more precisely. Meanwhile, considering skin points in a specific image have a relative stable distribution, a cluster-based skin model is presented to remove background points which are wrongly retained by the general model. Because of applying the characteristic of each specific image, this algorithm can effectively improve the performance and accuracy of skin model. Experimental result shows that this algorithm can achieve satisfied results for over 95% images, including obviously improved images for over 70% .
2005, 27(11): 1782-1785.
Abstract:
Because of the complexity in satellite remote sensing imaging system, some uncertainties or mixed spectrum information are contained in the data. By using maximal likelihood classification to process remote sensing data, the result accuracy of the classification is affected. In order to improve the accuracy of the classification, prior knowledge is needed to modify the probability. Bayesian network is composed of directed acyclic graph and probability chart; it can modify the prior probability density dynamically and improve the accuracy of classification. In this paper, a technical procedure is demonstrated that using Bayesian network to process the remote sensing data, the classification results prove that Bayesian network has solid mathematics base and can be a new effective methods for remote sensing data processing.
Because of the complexity in satellite remote sensing imaging system, some uncertainties or mixed spectrum information are contained in the data. By using maximal likelihood classification to process remote sensing data, the result accuracy of the classification is affected. In order to improve the accuracy of the classification, prior knowledge is needed to modify the probability. Bayesian network is composed of directed acyclic graph and probability chart; it can modify the prior probability density dynamically and improve the accuracy of classification. In this paper, a technical procedure is demonstrated that using Bayesian network to process the remote sensing data, the classification results prove that Bayesian network has solid mathematics base and can be a new effective methods for remote sensing data processing.
2005, 27(11): 1786-1789.
Abstract:
This paper describes the principle of antenna stabilization platform of airborne SAR briefly, and then introduces an ATS(Automatic Test System) for such platform . The core of this system is a PXI VI(Virtual Instrument). The system uses an electro-controlling motion simulator to simulate the angle-motion of airplane and laser-test device to test the track error of the platform. It can be used for different types of antenna stabilization platform of airborne SAR.
This paper describes the principle of antenna stabilization platform of airborne SAR briefly, and then introduces an ATS(Automatic Test System) for such platform . The core of this system is a PXI VI(Virtual Instrument). The system uses an electro-controlling motion simulator to simulate the angle-motion of airplane and laser-test device to test the track error of the platform. It can be used for different types of antenna stabilization platform of airborne SAR.
2005, 27(11): 1790-1794.
Abstract:
This paper proposed a new clutter reduction method based on characteristic of Ground Penetrating Radar(GPR) image in detecting shallow subsurface objects. Moreover, a method to realize fast synthetic aperture imaging based on the proposed clutter reduction method is proposed. The results of processing measurement data show the proposed clutter reduction method is very effective and universally valid; The resolving power of image gained by the proposed fast synthetic aperture imaging method corresponds with that general synthetic aperture imaging method, thanks to the proposed method can eliminate the influence of clutter, so the processing speed is improve greatly comparing with general synthetic aperture imaging method, the effect of image gained by the proposed method better than general synthetic aperture imaging method.
This paper proposed a new clutter reduction method based on characteristic of Ground Penetrating Radar(GPR) image in detecting shallow subsurface objects. Moreover, a method to realize fast synthetic aperture imaging based on the proposed clutter reduction method is proposed. The results of processing measurement data show the proposed clutter reduction method is very effective and universally valid; The resolving power of image gained by the proposed fast synthetic aperture imaging method corresponds with that general synthetic aperture imaging method, thanks to the proposed method can eliminate the influence of clutter, so the processing speed is improve greatly comparing with general synthetic aperture imaging method, the effect of image gained by the proposed method better than general synthetic aperture imaging method.
2005, 27(11): 1795-1800.
Abstract:
Based on the idea of contention reservation access and polling transmission, a modified User-dependent Perfect-scheduling Multiple Access (UPMA) protocol is proposed, the bandwidth can be allocated dynamically to the uplink and downlink according to the service requirement, the active node can access the channel rapidly by effective collision resolution scheme, and no transmission overhead will be wasted during transmission by the valid polling scheme. Meanwhile, the theoretic analytical model is proposed and its correctness is validated by simulation. The theoretic value and the simulation results show that the proposed protocol has a high throughput, low information delay and small information dropping probability. Finally, with the theoretic analysis, to a given length of polling period, the optimal length of contention access period is given.
Based on the idea of contention reservation access and polling transmission, a modified User-dependent Perfect-scheduling Multiple Access (UPMA) protocol is proposed, the bandwidth can be allocated dynamically to the uplink and downlink according to the service requirement, the active node can access the channel rapidly by effective collision resolution scheme, and no transmission overhead will be wasted during transmission by the valid polling scheme. Meanwhile, the theoretic analytical model is proposed and its correctness is validated by simulation. The theoretic value and the simulation results show that the proposed protocol has a high throughput, low information delay and small information dropping probability. Finally, with the theoretic analysis, to a given length of polling period, the optimal length of contention access period is given.
2005, 27(11): 1801-1805.
Abstract:
Scalable switching fabrics can be done on implementing high performance routers by employing multi-dimensional packet switching fabrics. The internal routing algorithm in the switching fabric is a key technology. This paper proposes a new distributed deadlock detection strategy, which combines with queue length on each node without other information required except local information. Based on this technology, a fully adaptive routing algorithmQDAR(Queue length based Deadlock recovery Adaptive Routing) have been designed. The performance is assessed on 3-dimensional torus architecture. Effect of the buffer length, the number of virtual channels and variable traffic types has been analyzed. Performance evaluation through comparing with other routing algorithms has been done.
Scalable switching fabrics can be done on implementing high performance routers by employing multi-dimensional packet switching fabrics. The internal routing algorithm in the switching fabric is a key technology. This paper proposes a new distributed deadlock detection strategy, which combines with queue length on each node without other information required except local information. Based on this technology, a fully adaptive routing algorithmQDAR(Queue length based Deadlock recovery Adaptive Routing) have been designed. The performance is assessed on 3-dimensional torus architecture. Effect of the buffer length, the number of virtual channels and variable traffic types has been analyzed. Performance evaluation through comparing with other routing algorithms has been done.
2005, 27(11): 1806-1812.
Abstract:
A new QoS routing algorithm for mobile Ad hoc networks, Fuzzy Logic QoS Dynamic Source Routing (FLQDSR), is proposed in this paper. The idea of FLQDSR starts from the fuzzy theory. It integrates the multiple QoS parameters of traffic into one request that is represented by Language variable through integrated fuzzy judgment. Based on the multiple paths routing algorithm which is modified the Dynamic Source Routing (DSR), FLQDSR compares the integrated QoS fuzzy value of each path and selects the most appropriate one according to the fuzzy rules. Simulation results show that FLQDSR can tolerate the imprecise information which is caused by the dynamic network topology well while supporting QoS function.
A new QoS routing algorithm for mobile Ad hoc networks, Fuzzy Logic QoS Dynamic Source Routing (FLQDSR), is proposed in this paper. The idea of FLQDSR starts from the fuzzy theory. It integrates the multiple QoS parameters of traffic into one request that is represented by Language variable through integrated fuzzy judgment. Based on the multiple paths routing algorithm which is modified the Dynamic Source Routing (DSR), FLQDSR compares the integrated QoS fuzzy value of each path and selects the most appropriate one according to the fuzzy rules. Simulation results show that FLQDSR can tolerate the imprecise information which is caused by the dynamic network topology well while supporting QoS function.
2005, 27(11): 1813-1817.
Abstract:
Although it is very meaningful to embed secret messages into a cover image in JPEG format, an analyst can detect the presence of hidden data according to a change of DCT coefficient histogram or an increase of blockiness parameter. In order to improve the security of embedded information, a secure steganographic technique is proposed, in which AC DCT coefficients with non-zero values are used to carry the secret bits when the DCT coefficient histogram and blockiness property are reserved. This way, the histogram-based and blockiness-based steganalyses are effectively resisted. Simulation results show that the proposed method is secure for cover images with quality factor more than 35.
Although it is very meaningful to embed secret messages into a cover image in JPEG format, an analyst can detect the presence of hidden data according to a change of DCT coefficient histogram or an increase of blockiness parameter. In order to improve the security of embedded information, a secure steganographic technique is proposed, in which AC DCT coefficients with non-zero values are used to carry the secret bits when the DCT coefficient histogram and blockiness property are reserved. This way, the histogram-based and blockiness-based steganalyses are effectively resisted. Simulation results show that the proposed method is secure for cover images with quality factor more than 35.
2005, 27(11): 1818-1820.
Abstract:
The learning issue of feedforward neural networks whose activation function of hidden neurons satisfies Mercer condition is discussed in theory. The approach to improving learning speed is investigated. Then a fast learning algorithm of feedforward neural networks based on screening samples dynamically is proposed, which improves learning speed, solves the abuses of those learning algorithm based on gradient decent method and has the self-configuring advantage by determining the number of hidden neuron dynamically. The reliability and advantage of the proposed algorithm are illustrated concretely through test.
The learning issue of feedforward neural networks whose activation function of hidden neurons satisfies Mercer condition is discussed in theory. The approach to improving learning speed is investigated. Then a fast learning algorithm of feedforward neural networks based on screening samples dynamically is proposed, which improves learning speed, solves the abuses of those learning algorithm based on gradient decent method and has the self-configuring advantage by determining the number of hidden neuron dynamically. The reliability and advantage of the proposed algorithm are illustrated concretely through test.
2005, 27(11): 1821-1824.
Abstract:
In this article, the transformations of the parametric coordinates (i.e. area coordinates) and general Duffycoordinates are employed to transform the singular integrals of the Time-Domain Electric Field Integral Equation (TDEFIE) into non-singular integrals, which can be accurately and efficiently evaluated by dividing the transformed domain of integration into sub-domains. Simulation results demonstrate that this approach seems to drastically improve stability and accuracy of the numerical results without resort to any averaging processes. The proposed method is suitable to any causal temporal basis functions and can be extended to curvilinear patch and high-order spatial basis functions in a straightforward way.
In this article, the transformations of the parametric coordinates (i.e. area coordinates) and general Duffycoordinates are employed to transform the singular integrals of the Time-Domain Electric Field Integral Equation (TDEFIE) into non-singular integrals, which can be accurately and efficiently evaluated by dividing the transformed domain of integration into sub-domains. Simulation results demonstrate that this approach seems to drastically improve stability and accuracy of the numerical results without resort to any averaging processes. The proposed method is suitable to any causal temporal basis functions and can be extended to curvilinear patch and high-order spatial basis functions in a straightforward way.
2005, 27(11): 1825-1828.
Abstract:
A kind of rectangular coaxial cavity, which is used for low frequency broadband multiple beam klystron, is studied. The 3D electromagnetic code of ISFEL3D is used to calculate the main parameters and field distribution of rectangular coaxial cavity. The results show that rectangular coaxial cavity has small volume and potential of bandwidth extending. It can be used in low frequency band multiple beam klystrons.
A kind of rectangular coaxial cavity, which is used for low frequency broadband multiple beam klystron, is studied. The 3D electromagnetic code of ISFEL3D is used to calculate the main parameters and field distribution of rectangular coaxial cavity. The results show that rectangular coaxial cavity has small volume and potential of bandwidth extending. It can be used in low frequency band multiple beam klystrons.
2005, 27(11): 1829-1833.
Abstract:
A hardware implement Adaptive Genetic Algorithm (AGA) is proposed in this paper. The adaptive algorithm uses three parameters, i. e. fmax , fmin and fave to determine the fc and fm of the whole generation adaptively. The selection , crossover and mutation operators which are suitable for hardware implement are selected and they are designed in a pipelining architecture . The parallelism of the selection operator and the computation of the fitness of the individual enhance the efficiency of the algorithm greatly. The hardware GA processor has been implemented in XILINX FPGA(Field Programmable Gate Arrays) XC2V1000. The VHDL language is used to describe the whole algorithm. Experimental results indicate that the adaptive genetic algorithm improves the global convergence and search performance of the algorithm greatly. The hardware implementation of the algorithm reduces the running time efficiently and makes it possible to apply in time-critical systems.
A hardware implement Adaptive Genetic Algorithm (AGA) is proposed in this paper. The adaptive algorithm uses three parameters, i. e. fmax , fmin and fave to determine the fc and fm of the whole generation adaptively. The selection , crossover and mutation operators which are suitable for hardware implement are selected and they are designed in a pipelining architecture . The parallelism of the selection operator and the computation of the fitness of the individual enhance the efficiency of the algorithm greatly. The hardware GA processor has been implemented in XILINX FPGA(Field Programmable Gate Arrays) XC2V1000. The VHDL language is used to describe the whole algorithm. Experimental results indicate that the adaptive genetic algorithm improves the global convergence and search performance of the algorithm greatly. The hardware implementation of the algorithm reduces the running time efficiently and makes it possible to apply in time-critical systems.
2005, 27(11): 1834-1838.
Abstract:
By analyzing the principle of 2-5 mixed-valued coding, the theory of three essential circuit elements and the theory of N+1-valued algebra, the 2-5 mixed-valued gate circuits, flip-flops and up-down counters with carry/borrow bit are investigated quantitatively, the 2-5 mixed-valued/ten-valued encoder is designed in order to make the output of counter become ten-valued signal. Compared with the conventional design of ten-valued circuits, the design has the characteristics of high coding efficiency, low voltage supply, etc. Above theory and circuits based on this theory are verified by computer simulations.
By analyzing the principle of 2-5 mixed-valued coding, the theory of three essential circuit elements and the theory of N+1-valued algebra, the 2-5 mixed-valued gate circuits, flip-flops and up-down counters with carry/borrow bit are investigated quantitatively, the 2-5 mixed-valued/ten-valued encoder is designed in order to make the output of counter become ten-valued signal. Compared with the conventional design of ten-valued circuits, the design has the characteristics of high coding efficiency, low voltage supply, etc. Above theory and circuits based on this theory are verified by computer simulations.
2005, 27(11): 1845-1848.
Abstract:
A new array channel mismatch model for simulations is proposed. The model consists of four sub-filters which separately control the four specifications of channels: amplitude variation, bandwidth, group delay variation and absolute delay offset. It is shown from design results that the channel mismatch model proposed is accurate and flexible, hence the model is suitable for the simulations of adaptive arrays.
A new array channel mismatch model for simulations is proposed. The model consists of four sub-filters which separately control the four specifications of channels: amplitude variation, bandwidth, group delay variation and absolute delay offset. It is shown from design results that the channel mismatch model proposed is accurate and flexible, hence the model is suitable for the simulations of adaptive arrays.
2005, 27(11): 1714-1716.
Abstract:
The high efficiency in bandwidth and high suppression to sidebands are very meaningful for wireless communications. Based on the composition of its modulated waveforms and power spectra, the optimization to very-minimun waveforms difference keying modulations is put forward, and the advanced modulated waveforms with narrower bandwidth and lower sidebands are obtained.
The high efficiency in bandwidth and high suppression to sidebands are very meaningful for wireless communications. Based on the composition of its modulated waveforms and power spectra, the optimization to very-minimun waveforms difference keying modulations is put forward, and the advanced modulated waveforms with narrower bandwidth and lower sidebands are obtained.
2005, 27(11): 1839-1844.
Abstract:
According to the prototype of living bodys immune system，Artificial Immune System, (AIS) is introduced. Based on the main function of immune system， the typical algorithms are described， such as immune algorithm，negative and clonal selection algorithms，immune evolutionary algorithm，AIS-neural network mix intelligent system，fuzzy immune system，danger model and so on. a chronological list of AIS models and techniques that are found in the literature is showed. Finally，based on the analysis of AIS，the development directions and research emphases are discussed.
According to the prototype of living bodys immune system，Artificial Immune System, (AIS) is introduced. Based on the main function of immune system， the typical algorithms are described， such as immune algorithm，negative and clonal selection algorithms，immune evolutionary algorithm，AIS-neural network mix intelligent system，fuzzy immune system，danger model and so on. a chronological list of AIS models and techniques that are found in the literature is showed. Finally，based on the analysis of AIS，the development directions and research emphases are discussed.
