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2002 Vol. 24, No. 6
Display Method:
2002, 24(6): 721-725.
Abstract:
To support different QoS services in HFC, the CMTS scheduling algorithm should be analyzed carefully. However, in the most important standard-MCNS DOCSIS 1.1, no specific scheduling is prescribed, and many papers have discussed it with modified First Come First Service(FCFS). In this paper, a scheduling algorithm with QoS support-PDBQ is introduced. It distributes the priority of services by the different used bandwidth of different services. The influence of piggyback to throughput is also discussed, the performance of this algorithm is illustrated by simulation results. A method of improving link bandwidth utilization is presented in the typical delay-sensitive service of IP telephony.
To support different QoS services in HFC, the CMTS scheduling algorithm should be analyzed carefully. However, in the most important standard-MCNS DOCSIS 1.1, no specific scheduling is prescribed, and many papers have discussed it with modified First Come First Service(FCFS). In this paper, a scheduling algorithm with QoS support-PDBQ is introduced. It distributes the priority of services by the different used bandwidth of different services. The influence of piggyback to throughput is also discussed, the performance of this algorithm is illustrated by simulation results. A method of improving link bandwidth utilization is presented in the typical delay-sensitive service of IP telephony.
2002, 24(6): 726-734.
Abstract:
This paper presents an enhancement of flow control mechanism of traditional TCP, which is called as differentiated service Fast-TCP policy. Considering relative flow control, scheduling and queuing mechanisms, an effective implementation scheme of this policy is put forward. Lots of simulation results prove the feasibility and validity of differentiated service Fast-TCP policy and its implementation algorithm, and relative formula to estimate the burst of buffer occupancy. This policy suits for supporting differentiated services in current Internet.
This paper presents an enhancement of flow control mechanism of traditional TCP, which is called as differentiated service Fast-TCP policy. Considering relative flow control, scheduling and queuing mechanisms, an effective implementation scheme of this policy is put forward. Lots of simulation results prove the feasibility and validity of differentiated service Fast-TCP policy and its implementation algorithm, and relative formula to estimate the burst of buffer occupancy. This policy suits for supporting differentiated services in current Internet.
2002, 24(6): 735-743.
Abstract:
In this paper, joint estimation of the number of active users, active users and their timing in asynchronous CDMA systems are discussed. The subspace based method to oversampling received signal model is applied to identify the number of active users, and at the same time, to estimate active users and their timing while requiring only a priori knowledge of all the registered users signature sequences in its cell. The performances of the proposed algorithm are analyzed. This method does not require training sequence. Theoretical analysis ad simulation show that this algorithm is simple in computation, has good performance in joint estimation of active users and their timing, and is asymptotically near far resistant. Finally, simulation also shows that the performances are obviously improved when the received signal is sampled at multiple of the chip rate (oversampling).
In this paper, joint estimation of the number of active users, active users and their timing in asynchronous CDMA systems are discussed. The subspace based method to oversampling received signal model is applied to identify the number of active users, and at the same time, to estimate active users and their timing while requiring only a priori knowledge of all the registered users signature sequences in its cell. The performances of the proposed algorithm are analyzed. This method does not require training sequence. Theoretical analysis ad simulation show that this algorithm is simple in computation, has good performance in joint estimation of active users and their timing, and is asymptotically near far resistant. Finally, simulation also shows that the performances are obviously improved when the received signal is sampled at multiple of the chip rate (oversampling).
2002, 24(6): 744-750.
Abstract:
This paper focuses on the design of high quality speech coding with variable rate at 0.75～5.4kb/s. The new algorithm classifies input speech signals as noise, unvoiced speech, transitional speech and voiced speech, and it uses different codebooks as excited impulses according to different types of speech frames. Especially, an embedded splitting vector quantization method based on pitch synchronization to synthesize voiced speech is proposed. The speech can be recovered very well at low bit rate by making use of the itch periodicity for voiced speech frames. This new algorithm can overcome the disadvantage of CELP whose recovered speech quality will degrade quickly when the bit rate is below 4kb/s because the codebook size is too small. the informal listeing test results show that the subject quality of the algorithm exceeds that of QCELP while the average bit rate of the algorithm is only about 2kb/s, which is much lower than that of QCELP whose average bit rate is about 5kb/s. This new speech coding algorithm is therefore very apt to CDMA mobile communication systems.
This paper focuses on the design of high quality speech coding with variable rate at 0.75～5.4kb/s. The new algorithm classifies input speech signals as noise, unvoiced speech, transitional speech and voiced speech, and it uses different codebooks as excited impulses according to different types of speech frames. Especially, an embedded splitting vector quantization method based on pitch synchronization to synthesize voiced speech is proposed. The speech can be recovered very well at low bit rate by making use of the itch periodicity for voiced speech frames. This new algorithm can overcome the disadvantage of CELP whose recovered speech quality will degrade quickly when the bit rate is below 4kb/s because the codebook size is too small. the informal listeing test results show that the subject quality of the algorithm exceeds that of QCELP while the average bit rate of the algorithm is only about 2kb/s, which is much lower than that of QCELP whose average bit rate is about 5kb/s. This new speech coding algorithm is therefore very apt to CDMA mobile communication systems.
2002, 24(6): 751-757.
Abstract:
Throughput performance for Slotted ALOHA DS/CDMA (S-ALOHA-DS/CDMA) and Multicarrier Slotted ALOHA (MC-S-ALOHA) systems is performed and compared in this paper. Theory analysis and computer simulation results of throughput of S-ALOHA-DS/CDMA are obtained using different error correcting code. And comparison results with MC-S-ALOHA system are also obtained. It is proved that with the traffic increasing, the S-ALOHA-DS/CDMA with high error-correct code being used has better throughput performance. In the case of the too heavy traffic, the MC-S-ALOHA system has better throughput performance. If the total codes of the system are limited, the code contention collision will occur so that throughput will drop.
Throughput performance for Slotted ALOHA DS/CDMA (S-ALOHA-DS/CDMA) and Multicarrier Slotted ALOHA (MC-S-ALOHA) systems is performed and compared in this paper. Theory analysis and computer simulation results of throughput of S-ALOHA-DS/CDMA are obtained using different error correcting code. And comparison results with MC-S-ALOHA system are also obtained. It is proved that with the traffic increasing, the S-ALOHA-DS/CDMA with high error-correct code being used has better throughput performance. In the case of the too heavy traffic, the MC-S-ALOHA system has better throughput performance. If the total codes of the system are limited, the code contention collision will occur so that throughput will drop.
2002, 24(6): 758-764.
Abstract:
The optimizing design of chaotic synchronization system by combining feedback control with wavelet transformation is presented in this paper. In the transmitter, a part of signals is transformed by wavelet and the detail information is removed. In the receiver, the component with low frequency is reconstructed and discrete feedback is used. Using the optimizing design, transmitting signal is transmitted in compressible way, system resource is saved, the component with high frequency is filtered and the effects of disturbance and noise on synchronization are reduced. The optimizing design is illustrated by numerical simulation experiment.
The optimizing design of chaotic synchronization system by combining feedback control with wavelet transformation is presented in this paper. In the transmitter, a part of signals is transformed by wavelet and the detail information is removed. In the receiver, the component with low frequency is reconstructed and discrete feedback is used. Using the optimizing design, transmitting signal is transmitted in compressible way, system resource is saved, the component with high frequency is filtered and the effects of disturbance and noise on synchronization are reduced. The optimizing design is illustrated by numerical simulation experiment.
2002, 24(6): 765-772.
Abstract:
This paper investigates the optimal packet length for AAL2 packet voice system without bit dropping, which takes into consideration the features and quality of service of AAL2 packet voice. A conclusion is drawn that the optimal packet length is about 31byte for the case of 32kb/s encoded voice when AAL2 packet voice multiplexer without bit dropping is concerned. As far as 16kb/s encoded voice is concerned, the optimal packet length is about 27 byte. Under this condition, good voice quality can be achieved with small packet overhead.
This paper investigates the optimal packet length for AAL2 packet voice system without bit dropping, which takes into consideration the features and quality of service of AAL2 packet voice. A conclusion is drawn that the optimal packet length is about 31byte for the case of 32kb/s encoded voice when AAL2 packet voice multiplexer without bit dropping is concerned. As far as 16kb/s encoded voice is concerned, the optimal packet length is about 27 byte. Under this condition, good voice quality can be achieved with small packet overhead.
2002, 24(6): 773-780.
Abstract:
A pilot-based serial multipath interference cancellation method and the corresponding RAKE receiver are proposed. Theoretical analysis and computer simulations are carried out, and comparison with conventional RAKE receiver is performed. It is shown that RAKE receiver performance can be improved using this method with simple structure and easy implementation.
A pilot-based serial multipath interference cancellation method and the corresponding RAKE receiver are proposed. Theoretical analysis and computer simulations are carried out, and comparison with conventional RAKE receiver is performed. It is shown that RAKE receiver performance can be improved using this method with simple structure and easy implementation.
2002, 24(6): 781-788.
Abstract:
The general composition of IC arc prepayment product systems is briefly introduced. Three topics are investigated: the password security of the IC card, encrypting and checking the data on the IC card, and a novel comprehensive data security design scheme is proposed, so that damages by passive and active attacks are avoided. The product system adopts the technique of encrypting lock and the encryption mechanism of multi-hierarchy encryption key, which provide a new idea for the data encryption of IC card prepayment product systems.
The general composition of IC arc prepayment product systems is briefly introduced. Three topics are investigated: the password security of the IC card, encrypting and checking the data on the IC card, and a novel comprehensive data security design scheme is proposed, so that damages by passive and active attacks are avoided. The product system adopts the technique of encrypting lock and the encryption mechanism of multi-hierarchy encryption key, which provide a new idea for the data encryption of IC card prepayment product systems.
2002, 24(6): 789-793.
Abstract:
This paper presents a study on application of regularized Gaussian classifier to Raman spectroscopy signals pattern recognition. Each Raman spectrum is treated as a point in high dimensional vector space. For given samples, the statistical model is used and Bayes decision is adopted to classify then according to their maximum posterior probabilities. Computer experiments show that the classification accuracy is obtained as high as 99.81%.
This paper presents a study on application of regularized Gaussian classifier to Raman spectroscopy signals pattern recognition. Each Raman spectrum is treated as a point in high dimensional vector space. For given samples, the statistical model is used and Bayes decision is adopted to classify then according to their maximum posterior probabilities. Computer experiments show that the classification accuracy is obtained as high as 99.81%.
2002, 24(6): 794-799.
Abstract:
To describe contours in digital space and simplify the presentation of computer graphics, a wavelet descriptor is presented, which is suitable for contours constructed with a set of points. According to the fact that contours in digital space is periodical, wavelet descriptor is defined based on wavelet analysis of discrete periodic signal. Application of the wavelet descriptor for medical image contour description is achieved. Comparing with Fourier descriptor, this work shows that the contours expressed by wavelet descriptor can make a good shape preserving, and the data for constructing the contours is compressed.
To describe contours in digital space and simplify the presentation of computer graphics, a wavelet descriptor is presented, which is suitable for contours constructed with a set of points. According to the fact that contours in digital space is periodical, wavelet descriptor is defined based on wavelet analysis of discrete periodic signal. Application of the wavelet descriptor for medical image contour description is achieved. Comparing with Fourier descriptor, this work shows that the contours expressed by wavelet descriptor can make a good shape preserving, and the data for constructing the contours is compressed.
2002, 24(6): 800-804.
Abstract:
MEGs inversion is an important aspect in MEG studies. Generally, global optimization methods are usually used on estimating parameters of multidipole source, but these methods are of low convergence speed. To increase the computing speed, a strategy based on genetic algorithm combined with local optimization is adopted. This method has the ability of overcoming the problem of local minima, and has fast convergence speed. Computer simulation with real brain-shaped head model demonstrated the efficiency of the proposed strategy.
MEGs inversion is an important aspect in MEG studies. Generally, global optimization methods are usually used on estimating parameters of multidipole source, but these methods are of low convergence speed. To increase the computing speed, a strategy based on genetic algorithm combined with local optimization is adopted. This method has the ability of overcoming the problem of local minima, and has fast convergence speed. Computer simulation with real brain-shaped head model demonstrated the efficiency of the proposed strategy.
2002, 24(6): 805-810.
Abstract:
A general methodology of key-generation of noise-like by use of chaotic process of tent-map function is described in this paper, a mathematics model of noise-like chaotic coding memory is constructed, meanwhile the basic mechanism of circulant convolution and circulant correlation in image information storage and retrieval is demonstrated. Simulation experiments show that image can be correctly recalled from single-pattern and double-pattern of noise-like chaotic coding by use of circulant convolution and circulant correlation operation, and there is a displacement between the last recalled image and the prototype image.
A general methodology of key-generation of noise-like by use of chaotic process of tent-map function is described in this paper, a mathematics model of noise-like chaotic coding memory is constructed, meanwhile the basic mechanism of circulant convolution and circulant correlation in image information storage and retrieval is demonstrated. Simulation experiments show that image can be correctly recalled from single-pattern and double-pattern of noise-like chaotic coding by use of circulant convolution and circulant correlation operation, and there is a displacement between the last recalled image and the prototype image.
2002, 24(6): 811-815.
Abstract:
In this paper, using the stochastic resonance technique, the detection method of weak signal is simulated, then the increasing of SNR and the detecting of weak signal are investigated. And the signal passing through the stochastic resonator is compared with the original signal. It indicates that the stochastic resonance is fully able to become a strong newtool in signal detection.
In this paper, using the stochastic resonance technique, the detection method of weak signal is simulated, then the increasing of SNR and the detecting of weak signal are investigated. And the signal passing through the stochastic resonator is compared with the original signal. It indicates that the stochastic resonance is fully able to become a strong newtool in signal detection.
2002, 24(6): 816-820.
Abstract:
In this paper, the imaging theories for the squint mode SAR. are discussed. Basing on the discuss of the difference between the centric side-looking and squint mode SAR, a new imaging algorithm for squint mode SAR is presented. By this algorithm, high quality image with satisfied resolution for the squint mode SAR is obtained.
In this paper, the imaging theories for the squint mode SAR. are discussed. Basing on the discuss of the difference between the centric side-looking and squint mode SAR, a new imaging algorithm for squint mode SAR is presented. By this algorithm, high quality image with satisfied resolution for the squint mode SAR is obtained.
2002, 24(6): 821-826.
Abstract:
An approximate method is used to analyse the excited fields with a non-symmetrical dipole in lossy media and simple analytical expressions about the fields and joule heat are obtained. These expressions are compared with the formulas of traditional symmetrical half-wave dipole. Some calculated results are given for a typical oil reservior, which will be useful for the electromagnetic wave oil recovery technique.
An approximate method is used to analyse the excited fields with a non-symmetrical dipole in lossy media and simple analytical expressions about the fields and joule heat are obtained. These expressions are compared with the formulas of traditional symmetrical half-wave dipole. Some calculated results are given for a typical oil reservior, which will be useful for the electromagnetic wave oil recovery technique.
2002, 24(6): 827-832.
Abstract:
It is always the goal of the control systems design that ensuring the system robust stability and satisfying the requirements of the system performance specifications at the same time. In this paper, based on the requirements of stability and performance specifications of the excitation power supply for the angular measurement system of test turntable, a design method, is presented, in which the robust stability based H-optimal control theory is applied to the magnitude loop of excitation power supply with closed-loop control. The solving process of the H controller is discussed. Long period of operation of the four test turntables has proven that the validity and rationality of the design method fully satisfy the requirements of high precision test turntable.
It is always the goal of the control systems design that ensuring the system robust stability and satisfying the requirements of the system performance specifications at the same time. In this paper, based on the requirements of stability and performance specifications of the excitation power supply for the angular measurement system of test turntable, a design method, is presented, in which the robust stability based H-optimal control theory is applied to the magnitude loop of excitation power supply with closed-loop control. The solving process of the H controller is discussed. Long period of operation of the four test turntables has proven that the validity and rationality of the design method fully satisfy the requirements of high precision test turntable.
2002, 24(6): 833-837.
Abstract:
Power penalty of crosstalk in 17 cylindrical mixing-rod plastic optical coupler (17 CMRC) is studied. Theoretical model on the relationship between inter-port crosstalk in 17 CMRC, power penalty and bit error rate (BER) is built. The model indicates that power penalty induced by the inter-port crosstalk under -20dB is insignificant and can be ignored. Experimental measurement of the 17 CMRC showing that the inter-port crosstalk is lower than -23dB, the inter-port crosstalk can be further lowered by about 5dB as the mismatched end-face of the mixing-rod is coated with optical absorb materials.
Power penalty of crosstalk in 17 cylindrical mixing-rod plastic optical coupler (17 CMRC) is studied. Theoretical model on the relationship between inter-port crosstalk in 17 CMRC, power penalty and bit error rate (BER) is built. The model indicates that power penalty induced by the inter-port crosstalk under -20dB is insignificant and can be ignored. Experimental measurement of the 17 CMRC showing that the inter-port crosstalk is lower than -23dB, the inter-port crosstalk can be further lowered by about 5dB as the mismatched end-face of the mixing-rod is coated with optical absorb materials.
2002, 24(6): 838-844.
Abstract:
Based on the hydro-dynamics energy transport model, the influence of geometrical structure parameters on hot-carrier-effect immunity in deep-submicron grooved gate PMOSFET is studied and explained in terms of device interior physics mechanism. These investigated structure parameters include effective channel length, concave corner and negative junction depth induced by change of source/drain junction depth and groove depth respectively. The research results indicate that the hot-carrier-effect is depressed deeply for grooved gate PMOSFET even in deep and super-deep-sub-micron region, and with the increase of concave corner and negative junction depth, the hot-carrier-effect immunity becomes better. It is mainly because that the structure parameters influence the electric field distribution in device and corner effect and so do the transportation of carriers.
Based on the hydro-dynamics energy transport model, the influence of geometrical structure parameters on hot-carrier-effect immunity in deep-submicron grooved gate PMOSFET is studied and explained in terms of device interior physics mechanism. These investigated structure parameters include effective channel length, concave corner and negative junction depth induced by change of source/drain junction depth and groove depth respectively. The research results indicate that the hot-carrier-effect is depressed deeply for grooved gate PMOSFET even in deep and super-deep-sub-micron region, and with the increase of concave corner and negative junction depth, the hot-carrier-effect immunity becomes better. It is mainly because that the structure parameters influence the electric field distribution in device and corner effect and so do the transportation of carriers.
2002, 24(6): 845-849.
Abstract:
In this paper, an efficient method for speaker recognition-the combination of VQ (Vector-Quantization) algorithm with fuzzy C-mean clustering algorithm is proposed. This algorithm extracts 12th order LPC cepstrum coefficients from speech signals and makes them the marker of those samples, which will be classified. At first, codebooks which can represent those feature parameters of each speaker are figured out, and used as the clustering centers of speaker recognition. Finally, all speakers feature parameters are identified from each other with fuzzy C-mean clustering algorithm in which the clustering centers are these codebooks which has been obtained using VQ algorithm. With relatively less feature parmeters and simpler computation, the proposed algorithm has a higher recognition rate compared with VQ algorithm.
In this paper, an efficient method for speaker recognition-the combination of VQ (Vector-Quantization) algorithm with fuzzy C-mean clustering algorithm is proposed. This algorithm extracts 12th order LPC cepstrum coefficients from speech signals and makes them the marker of those samples, which will be classified. At first, codebooks which can represent those feature parameters of each speaker are figured out, and used as the clustering centers of speaker recognition. Finally, all speakers feature parameters are identified from each other with fuzzy C-mean clustering algorithm in which the clustering centers are these codebooks which has been obtained using VQ algorithm. With relatively less feature parmeters and simpler computation, the proposed algorithm has a higher recognition rate compared with VQ algorithm.
2002, 24(6): 850-854.
Abstract:
This paper presents a balancing admission mechanism of wide band and narrow band calls in ATM networks. The combination of the mechanism with CAC can guarantee the fair admission of all kinds of calls. This paper also analyzes the probabilities of wide band calls blocking the narrow band calls in ATM networks under the mechanism when the traffic approaching to the system capacity. The analysis exposes that the proposed balancing mechanism can avoid the phenomena of one kind calls blocking the other kind calls. The result of the analysis is helpful for choosing a reasonable call admission and call refusing policy in practice.
This paper presents a balancing admission mechanism of wide band and narrow band calls in ATM networks. The combination of the mechanism with CAC can guarantee the fair admission of all kinds of calls. This paper also analyzes the probabilities of wide band calls blocking the narrow band calls in ATM networks under the mechanism when the traffic approaching to the system capacity. The analysis exposes that the proposed balancing mechanism can avoid the phenomena of one kind calls blocking the other kind calls. The result of the analysis is helpful for choosing a reasonable call admission and call refusing policy in practice.
2002, 24(6): 855-859.
Abstract:
This paper studies the generalized synchronization of hyperchaotic circuit . Theoretical analysis demonstrates that if a matrix and its commutative matrix can be built, generalized synchronization of driving system and driven system can be realized. A 4-D hyperchaotic oscillator is taken as typical example. The results of numerical simulation are presented.
This paper studies the generalized synchronization of hyperchaotic circuit . Theoretical analysis demonstrates that if a matrix and its commutative matrix can be built, generalized synchronization of driving system and driven system can be realized. A 4-D hyperchaotic oscillator is taken as typical example. The results of numerical simulation are presented.
2002, 24(6): 860-864.
Abstract:
The new optical methods for measuring electric energy utilizing the Faradays magneto-optical effect and the Pockel effect of some transparent material with single chip computer technology are proposed in this paper. The principle is discussed comprehensively and systematically. The optical measuring electric energy system designed by writer has been introduced. The experimental results are presented. The study shows that the theoretical analysis coincides with experimental results. It proves that the optical measuring electric energy system is effective.
The new optical methods for measuring electric energy utilizing the Faradays magneto-optical effect and the Pockel effect of some transparent material with single chip computer technology are proposed in this paper. The principle is discussed comprehensively and systematically. The optical measuring electric energy system designed by writer has been introduced. The experimental results are presented. The study shows that the theoretical analysis coincides with experimental results. It proves that the optical measuring electric energy system is effective.
