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2003 Vol. 25, No. 2
Display Method:
2003, 25(2): 145-151.
Abstract:
The 3G mobile communication systems based on CDMA technique are expected to provide multi-services to mobile users. An efficient call admission control scheme is essential to provide QoS guarantees of different services to as many users as possible. This paper analyzes the relation between the system residual capacity and QoS constraints for a multi-service CDMA cellular system. Then the SIR-measurement-based local and global call admission control schemes for multi-services are proposed. The performances of the two schemes under both uniform and non-uniform traffic distribution environments are studied through extensive simulations. The simulation results show that global scheme outperforms the local scheme under both environments.
The 3G mobile communication systems based on CDMA technique are expected to provide multi-services to mobile users. An efficient call admission control scheme is essential to provide QoS guarantees of different services to as many users as possible. This paper analyzes the relation between the system residual capacity and QoS constraints for a multi-service CDMA cellular system. Then the SIR-measurement-based local and global call admission control schemes for multi-services are proposed. The performances of the two schemes under both uniform and non-uniform traffic distribution environments are studied through extensive simulations. The simulation results show that global scheme outperforms the local scheme under both environments.
2003, 25(2): 152-157.
Abstract:
In a Code Division Multiple Access (CDMA) mobile communication system which supports multiple services, such as voice, and data, the variation degree of the cell load after adding a connection is different for the services with different data, rates and quality of service (QoS) requirements. Hence the cell load must be constrained to preserve the system stability. This paper presents a method for forecasting the increment of the cell reverse load after adding a new connection of a pre-defined service type. The method is then exemplified by applying it to predict the reverse load in a typical system. The results are further validated by computer simulation.
In a Code Division Multiple Access (CDMA) mobile communication system which supports multiple services, such as voice, and data, the variation degree of the cell load after adding a connection is different for the services with different data, rates and quality of service (QoS) requirements. Hence the cell load must be constrained to preserve the system stability. This paper presents a method for forecasting the increment of the cell reverse load after adding a new connection of a pre-defined service type. The method is then exemplified by applying it to predict the reverse load in a typical system. The results are further validated by computer simulation.
2003, 25(2): 158-163.
Abstract:
This paper presents a new implementation mechanism of RED, Cooperative Adjusted RED (CARED), for the DiffServ network. It, deduces first, the quantitative relationship between the actual rate and the committed rate of services on the basis of the marking probability of token-based markers, and then adjust the dropping probability of CARED to drop packets fairly according to this relationship. It also proposes a new marking probability metering algorithm NSWM to implement CARED in DiffServ network. Lots of simulations have validated the relationship between the actual rate and the committed rate and prove the efficiency of CARED.
This paper presents a new implementation mechanism of RED, Cooperative Adjusted RED (CARED), for the DiffServ network. It, deduces first, the quantitative relationship between the actual rate and the committed rate of services on the basis of the marking probability of token-based markers, and then adjust the dropping probability of CARED to drop packets fairly according to this relationship. It also proposes a new marking probability metering algorithm NSWM to implement CARED in DiffServ network. Lots of simulations have validated the relationship between the actual rate and the committed rate and prove the efficiency of CARED.
2003, 25(2): 164-170.
Abstract:
This paper presents a new scheme of wavelet image coding, X-tree. An X-tree is a spatial hierarchical tree whose all nodes are 0 except the root node. It is the generalization of the zero tree. Based on the X-tree scheme, two new coding algorithms, the embedded X-tree approach and the general X-tree approach are proposed in the paper. Experimental results show that the coding efficiency of the proposed algorithms are obviously higher than those of the stack-run and the EZW algorithms.
This paper presents a new scheme of wavelet image coding, X-tree. An X-tree is a spatial hierarchical tree whose all nodes are 0 except the root node. It is the generalization of the zero tree. Based on the X-tree scheme, two new coding algorithms, the embedded X-tree approach and the general X-tree approach are proposed in the paper. Experimental results show that the coding efficiency of the proposed algorithms are obviously higher than those of the stack-run and the EZW algorithms.
2003, 25(2): 171-179.
Abstract:
Quantum cryptography is best known for key distribution. However, previous proposed proofs of security of Quantum Key Distribution (QKD) contain various technical subtleties. In this paper, a conceptually simpler proof of security of QKD is proposed. Also, the error rate of a teleportation channel has no concern with the signal being transmitted. This is because the non-trivial error patterns are permuted under teleportation. This inherent fact is combined with the recently proposed quantum to classical reduction theorem. In the argument, supposed Alice and Bob to have fault-tolerant quantum computer, the result shows that QKD can be made unconditionally secure over arbitrarily long distances even against the most general type of eavesdropping attacks and in the presence of all types of noises.
Quantum cryptography is best known for key distribution. However, previous proposed proofs of security of Quantum Key Distribution (QKD) contain various technical subtleties. In this paper, a conceptually simpler proof of security of QKD is proposed. Also, the error rate of a teleportation channel has no concern with the signal being transmitted. This is because the non-trivial error patterns are permuted under teleportation. This inherent fact is combined with the recently proposed quantum to classical reduction theorem. In the argument, supposed Alice and Bob to have fault-tolerant quantum computer, the result shows that QKD can be made unconditionally secure over arbitrarily long distances even against the most general type of eavesdropping attacks and in the presence of all types of noises.
2003, 25(2): 180-186.
Abstract:
Most watermarking schemes focus on the robustness and invisibility with the problem of copyright protection remained unresolved, which are their initial motivation. In this paper, a watermarking scheme is proposed to provide effective copyright protection. By using a. novel method of generating watermark, the use of original data is no longer limited in resolving rightful ownerships. Moreover, blind and non-blind watermark detections have different applications. The robustness and invisibility are also improved. Both theoretical analysis and experimental results show its effectiveness against copyright attack and other distortions such as JPEG compression, Additive White Gaussian Noise (AWGN), image resizing and media filtering.
Most watermarking schemes focus on the robustness and invisibility with the problem of copyright protection remained unresolved, which are their initial motivation. In this paper, a watermarking scheme is proposed to provide effective copyright protection. By using a. novel method of generating watermark, the use of original data is no longer limited in resolving rightful ownerships. Moreover, blind and non-blind watermark detections have different applications. The robustness and invisibility are also improved. Both theoretical analysis and experimental results show its effectiveness against copyright attack and other distortions such as JPEG compression, Additive White Gaussian Noise (AWGN), image resizing and media filtering.
2003, 25(2): 187-194.
Abstract:
One source blind extraction can be used to blind beamfonning for underwater acoustic arrays. Among existing candidate approaches such as the simple constant modulus Algorithm (CMA), Kurtosis Maximization Algorithm (KMA), etc., KMA can separate both negative and positive kurtosis signals. As KMA is used to separate underwater acoustic signals the convergence rate is low. Present paper applies logarithm of kurtosis to form tho objective function, and proposes a one source blind extraction algorithm based on logaritlnii-kiiirtosis maximization. At the same time, double deflation algorithms are also proposed to separate more signals in turn. In contrast to KMA convergence rate is improved. A nonlinear Function is used in learning so that the algorithm can choose the learning step automatically. Computer simulations verify the proposed algorithm.
One source blind extraction can be used to blind beamfonning for underwater acoustic arrays. Among existing candidate approaches such as the simple constant modulus Algorithm (CMA), Kurtosis Maximization Algorithm (KMA), etc., KMA can separate both negative and positive kurtosis signals. As KMA is used to separate underwater acoustic signals the convergence rate is low. Present paper applies logarithm of kurtosis to form tho objective function, and proposes a one source blind extraction algorithm based on logaritlnii-kiiirtosis maximization. At the same time, double deflation algorithms are also proposed to separate more signals in turn. In contrast to KMA convergence rate is improved. A nonlinear Function is used in learning so that the algorithm can choose the learning step automatically. Computer simulations verify the proposed algorithm.
2003, 25(2): 195-199.
Abstract:
This paper introduces weak periodic pulse signal into given chaotic system, and uses the change of system phase track which leaps from chaotic status to periodic status as the detection criterion. The given chaotic system is used to realize weak periodic pulse signal detection under strong noise background. Simulation experiments show that chaos detection system is very sensitive to periodic pulse signal contained by strong noise and has strong constraint to any colored noise.
This paper introduces weak periodic pulse signal into given chaotic system, and uses the change of system phase track which leaps from chaotic status to periodic status as the detection criterion. The given chaotic system is used to realize weak periodic pulse signal detection under strong noise background. Simulation experiments show that chaos detection system is very sensitive to periodic pulse signal contained by strong noise and has strong constraint to any colored noise.
2003, 25(2): 200-205.
Abstract:
In this paper, an adaptive quasi-Newton algorithm for eigensubspace estimation is analysed and proved. This algorithm is similar to power method, but its transient performance is poor than power method. Assuming one iteration to be done between snapshots, the error between estimated and true eigenpairs is obtained. The simulation results show the correct of the analysis in this paper.
In this paper, an adaptive quasi-Newton algorithm for eigensubspace estimation is analysed and proved. This algorithm is similar to power method, but its transient performance is poor than power method. Assuming one iteration to be done between snapshots, the error between estimated and true eigenpairs is obtained. The simulation results show the correct of the analysis in this paper.
2003, 25(2): 206-211.
Abstract:
In the paper, the method to estimate instantaneous frequency of AM-FM signals using the peak of the WVD and its performances are studied. Analysis results show that the estimation on amplitude time-varying and frequency linear modulating signals will be unbiased, only if the WVD of time-varying amplitude reaches its maximum at frequency zero no matter in which time. The related expected variance is given in the paper. The simulations using signals modulated Gaussian envelope in amplitude and linearly in frequency support this conclusion.
In the paper, the method to estimate instantaneous frequency of AM-FM signals using the peak of the WVD and its performances are studied. Analysis results show that the estimation on amplitude time-varying and frequency linear modulating signals will be unbiased, only if the WVD of time-varying amplitude reaches its maximum at frequency zero no matter in which time. The related expected variance is given in the paper. The simulations using signals modulated Gaussian envelope in amplitude and linearly in frequency support this conclusion.
2003, 25(2): 212-217.
Abstract:
In stretching processing system of linear FM, the frequency is in proportion to range and the delay of returns are different in different ranges. The single frequency pulses occupy different time intervals indicating the variation in time delay as a function of range after stretching processing. This will lead to high sidelobe when proceeding with a uniform weight in the whole time width. This paper describes a method of delay compensation with subband filter group. Sidelobe level of weighted signal will be greatly reduced after the synthesis of multiple channels.
In stretching processing system of linear FM, the frequency is in proportion to range and the delay of returns are different in different ranges. The single frequency pulses occupy different time intervals indicating the variation in time delay as a function of range after stretching processing. This will lead to high sidelobe when proceeding with a uniform weight in the whole time width. This paper describes a method of delay compensation with subband filter group. Sidelobe level of weighted signal will be greatly reduced after the synthesis of multiple channels.
2003, 25(2): 218-223.
Abstract:
An improved method is presented on the base of the study for the discrete-amplitude multi-resolution speech coding. New coding format is adopted through statistical analysis for signal amplitude. Then the indented adapting bit allocation is employed. Theoretical analysis and experimental results show that improved coding method can farther reduce the coding rate maintaining the same speech quality.
An improved method is presented on the base of the study for the discrete-amplitude multi-resolution speech coding. New coding format is adopted through statistical analysis for signal amplitude. Then the indented adapting bit allocation is employed. Theoretical analysis and experimental results show that improved coding method can farther reduce the coding rate maintaining the same speech quality.
2003, 25(2): 224-228.
Abstract:
This paper describes the coronary arteries of human being macroscopically and locally, and proposes a method named parameter co-restriction of spherical coordinate to model the heart, which is used to control the spatial configuration of coronary arteries. Then combining the optimum principle of vessel system, a rule-base of vessel bifurcations is built. Finally, the coronary arteries can be simulated by choosing one of the bifurcate modes according to the given probability in each iterated course, which is induced from the idea of iterated function system in fractal theory. At the same time, some random variables are also introduced to make the simulating result more vivid, and the experiment indicates the validity of this method.
This paper describes the coronary arteries of human being macroscopically and locally, and proposes a method named parameter co-restriction of spherical coordinate to model the heart, which is used to control the spatial configuration of coronary arteries. Then combining the optimum principle of vessel system, a rule-base of vessel bifurcations is built. Finally, the coronary arteries can be simulated by choosing one of the bifurcate modes according to the given probability in each iterated course, which is induced from the idea of iterated function system in fractal theory. At the same time, some random variables are also introduced to make the simulating result more vivid, and the experiment indicates the validity of this method.
2003, 25(2): 229-234.
Abstract:
The definition of frequency linearity of LFM(Lincar Frequency Modulation) is discussed in this paper. The causes for frequency linearity, phase error and spectrum unevenness during the process of generation with digital method are analyzed. The effects of these errors on SAR image are also described. Finally, the simulation results are given in this paper.
The definition of frequency linearity of LFM(Lincar Frequency Modulation) is discussed in this paper. The causes for frequency linearity, phase error and spectrum unevenness during the process of generation with digital method are analyzed. The effects of these errors on SAR image are also described. Finally, the simulation results are given in this paper.
2003, 25(2): 235-241.
Abstract:
Generalized impedance boundary conditions are employed to simulate the effect of the earths surface on electromagnetic fields. The Sommerfeld type integrals contained in the electromagnetic fields of a horizontal electric dipole over the ground plane are expressed as a rapidly and absolutely convergent expansion of spherical wave functions; and the coefficients of the series are cast into the Legendre functions with argument for the complex surface impedance of the ground with the help of the techniques of the transformation of integration path and the hypergeometric functions. The obtained results have explicit mathematical and physical interpretation and can conveniently be used to calculate the fields. The technique described here is an accurate and efficient computation for the Sommerfeld type integrals.
Generalized impedance boundary conditions are employed to simulate the effect of the earths surface on electromagnetic fields. The Sommerfeld type integrals contained in the electromagnetic fields of a horizontal electric dipole over the ground plane are expressed as a rapidly and absolutely convergent expansion of spherical wave functions; and the coefficients of the series are cast into the Legendre functions with argument for the complex surface impedance of the ground with the help of the techniques of the transformation of integration path and the hypergeometric functions. The obtained results have explicit mathematical and physical interpretation and can conveniently be used to calculate the fields. The technique described here is an accurate and efficient computation for the Sommerfeld type integrals.
2003, 25(2): 242-246.
Abstract:
The double-crossover Genetic Algorithm (GA) extending the basic idea of conventional Genetic Algorithms(GAs) is presented. The double-crossover GA with the double-crossover reproduction operation and parametric chromosomes gets rid of the dependence of the convergence of conventional GAs on the initial population, avoids troublesome encoding and decoding, and is more practical and effective than conventional GAs. To illustrate effectiveness and practicality, the double-crossover GA is applied to the scanning radiation pattern synthesis of aperiodic circular arrays. The successful application shows that the double-crossover GA can be used as a general tool for radiation pattern synthesis of antenna arrays.
The double-crossover Genetic Algorithm (GA) extending the basic idea of conventional Genetic Algorithms(GAs) is presented. The double-crossover GA with the double-crossover reproduction operation and parametric chromosomes gets rid of the dependence of the convergence of conventional GAs on the initial population, avoids troublesome encoding and decoding, and is more practical and effective than conventional GAs. To illustrate effectiveness and practicality, the double-crossover GA is applied to the scanning radiation pattern synthesis of aperiodic circular arrays. The successful application shows that the double-crossover GA can be used as a general tool for radiation pattern synthesis of antenna arrays.
2003, 25(2): 247-253.
Abstract:
In this paper, a novel hybrid approach is proposed in which Iterative Physical Optics (IPO)subdomain splicing technique is combined with edge-based finite element method. It is applied to the analyses of electromagnetic scattering characteristics of electrically large complex cavities. IPO approach is applied for the region where it is suitable to use high frequency method; the edge-based finite element method is employed for the region where complex structures or complex materials are located. At the interface, the field continuous condition is applied to realize the coupling of the two regions. To verify the new approach, an open-ended empty rectangular cavity and cavity loaded with a metal cuboid are analyzed. The numerical results are in agreement with the published data and those obtained by FDTD. Good convergence behavior is observed. Moreover, complex cavities where three layers of lossy dielectric or a metal cuboid is loaded at the bottom are analyzed. The results show that the proposed hybrid approach is efficient for analyzing the electromagnetic scattering characteristic of electrically large complex cavity.
In this paper, a novel hybrid approach is proposed in which Iterative Physical Optics (IPO)subdomain splicing technique is combined with edge-based finite element method. It is applied to the analyses of electromagnetic scattering characteristics of electrically large complex cavities. IPO approach is applied for the region where it is suitable to use high frequency method; the edge-based finite element method is employed for the region where complex structures or complex materials are located. At the interface, the field continuous condition is applied to realize the coupling of the two regions. To verify the new approach, an open-ended empty rectangular cavity and cavity loaded with a metal cuboid are analyzed. The numerical results are in agreement with the published data and those obtained by FDTD. Good convergence behavior is observed. Moreover, complex cavities where three layers of lossy dielectric or a metal cuboid is loaded at the bottom are analyzed. The results show that the proposed hybrid approach is efficient for analyzing the electromagnetic scattering characteristic of electrically large complex cavity.
2003, 25(2): 254-258.
Abstract:
The rapid increase in IC design complexity and greater time-to-market pressures require reuse of complex pre-defined design blocks to improve design productivity. By analyzing the communication between modules, this paper draws a conclusion that interface-based IP design methodology can improve design reusability. Interface-based IP design methodology and environment is built according to MSRS (Motorola Semiconductor Reuse Standard) A case is given which combines both hierarchical bus architecture and interface-based desitm methodology.
The rapid increase in IC design complexity and greater time-to-market pressures require reuse of complex pre-defined design blocks to improve design productivity. By analyzing the communication between modules, this paper draws a conclusion that interface-based IP design methodology can improve design reusability. Interface-based IP design methodology and environment is built according to MSRS (Motorola Semiconductor Reuse Standard) A case is given which combines both hierarchical bus architecture and interface-based desitm methodology.
2003, 25(2): 259-262.
Abstract:
Large-scale amorphous Si nanowires are prepared by heating the Si substrate at 950-1000C under the ambient of Ar/H2 (2.5104Pa) using Ni (or Au) catalyst. The nanowires have a length up to several tens micron and a diameter of 10-40 nm. A solid-liquid-solid (SLS) mechanism is found controlling the nanowire growth. The heating process during SLS growth is studied detailedly using SEM and TEM. Effects of several processing variables such as the pressure, temperature and heating time are investigated individually. The effect of three heating steps is also discussed.
Large-scale amorphous Si nanowires are prepared by heating the Si substrate at 950-1000C under the ambient of Ar/H2 (2.5104Pa) using Ni (or Au) catalyst. The nanowires have a length up to several tens micron and a diameter of 10-40 nm. A solid-liquid-solid (SLS) mechanism is found controlling the nanowire growth. The heating process during SLS growth is studied detailedly using SEM and TEM. Effects of several processing variables such as the pressure, temperature and heating time are investigated individually. The effect of three heating steps is also discussed.
2003, 25(2): 263-269.
Abstract:
Employing the synthetic technology with the Doppler shift, the high resolution image has been achieved by the observation of the space- or air-bome SAR (Syiitlietic. Aperture R.adar). However, unexpected Doppler shift caused by the high speed moving target can defocus the image. The Minimum Entropy Method (MEM) is an optimized method with no request of additional parameters. In this paper, an improved method of MEM is developed. The entropy, as a target function, is optimized for refocusing the image. This method is demonstrated fast and effective when it is applied to a simulated SAR image of a moving aircraft.
Employing the synthetic technology with the Doppler shift, the high resolution image has been achieved by the observation of the space- or air-bome SAR (Syiitlietic. Aperture R.adar). However, unexpected Doppler shift caused by the high speed moving target can defocus the image. The Minimum Entropy Method (MEM) is an optimized method with no request of additional parameters. In this paper, an improved method of MEM is developed. The entropy, as a target function, is optimized for refocusing the image. This method is demonstrated fast and effective when it is applied to a simulated SAR image of a moving aircraft.
2003, 25(2): 270-274.
Abstract:
An underwater acoustic channel blind equalization method via the blind source separation theory is presented. Constructing source signal by oversampling of the received signal, an on-line separation algorithm based on infoniax principle is employed to equalize the underwater acoustic channel. Convengence results in both time-invariant and time-variant, channel are studied. Simulation experiment shows that without the limit of minimum phase, the proposed algorithm gains promising results in multipath underwater acoustic channel.
An underwater acoustic channel blind equalization method via the blind source separation theory is presented. Constructing source signal by oversampling of the received signal, an on-line separation algorithm based on infoniax principle is employed to equalize the underwater acoustic channel. Convengence results in both time-invariant and time-variant, channel are studied. Simulation experiment shows that without the limit of minimum phase, the proposed algorithm gains promising results in multipath underwater acoustic channel.
2003, 25(2): 275-278.
Abstract:
In this paper, a new fast algorithm for the numerical multiplication of the points on elliptic curves is presented. By introducing 2k sequence representation for number, the length of numerical multiplication is shortened, so that the number of addition operation on elliptic curves is decreased greatly. Moreover, the optimal choice of k is analyzed and the efficiency of the algorithm presented is improved about 60.
In this paper, a new fast algorithm for the numerical multiplication of the points on elliptic curves is presented. By introducing 2k sequence representation for number, the length of numerical multiplication is shortened, so that the number of addition operation on elliptic curves is decreased greatly. Moreover, the optimal choice of k is analyzed and the efficiency of the algorithm presented is improved about 60.
2003, 25(2): 279-283.
Abstract:
An equivalent circuit model of micromachined gyroscope s oscillating properties is derived according to its dynamics equation. The model is implemented with the circuit simulation tool PSPICE, and can be used to analyse oscillating properties, including the detection mode transient response, stable response and frequency response to angular rate. Thus the optimizing conditions can be gotten. And also the model enables the sensor to simulate together with the interfacing electronics.
An equivalent circuit model of micromachined gyroscope s oscillating properties is derived according to its dynamics equation. The model is implemented with the circuit simulation tool PSPICE, and can be used to analyse oscillating properties, including the detection mode transient response, stable response and frequency response to angular rate. Thus the optimizing conditions can be gotten. And also the model enables the sensor to simulate together with the interfacing electronics.
2003, 25(2): 284-288.
Abstract:
The effective microwave refractive index (Nm) of traveling wave electrode is an important parameter in the designing of LiNbO3 electro-optic modulator. A method for mea-kiring Nm is proposed in this paper. The probe frames, microwave probe and three kinds of sample CPW electrodes used in this method are designed and fabricated. The experimental results of Nm in CPW traveling-wave electrode are given. Finally, the errors of the measurement are analyzed.
The effective microwave refractive index (Nm) of traveling wave electrode is an important parameter in the designing of LiNbO3 electro-optic modulator. A method for mea-kiring Nm is proposed in this paper. The probe frames, microwave probe and three kinds of sample CPW electrodes used in this method are designed and fabricated. The experimental results of Nm in CPW traveling-wave electrode are given. Finally, the errors of the measurement are analyzed.
