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2004 Vol. 26, No. 7
Display Method:
2004, 26(7): 1009-1016.
Abstract:
In order to improve the spectral efficiency, this paper proposes a new framework for designing a modulation consisting of more than one modulation method. The new modulation method is able to provide better spectral efficiency while preserving the merits of Unitary Space-Time Modulation (USTM), such as low error rate and demodulation simplicity. The necessary condition for this set of modulations is presented and several different options satisfying the condition are given. Finally a novel modulation called Differential Phase Unitary Space-Time Modulation (DPUSTM) is designed as a special case. DPUSTM, which consists of USTM and Differential Phase-Shift Keying (DPSK) modulation, is not only easier to improve the spectral efficiency than USTM, but also simpler to demodulate. The novel modulation can achieve low bit error rate as UST signals and be exploited in multi-rate data communication. The simulation results not only verify the theoretical analysis, but also show that DPUSTM provides a better performance than USTM and DSTM.
In order to improve the spectral efficiency, this paper proposes a new framework for designing a modulation consisting of more than one modulation method. The new modulation method is able to provide better spectral efficiency while preserving the merits of Unitary Space-Time Modulation (USTM), such as low error rate and demodulation simplicity. The necessary condition for this set of modulations is presented and several different options satisfying the condition are given. Finally a novel modulation called Differential Phase Unitary Space-Time Modulation (DPUSTM) is designed as a special case. DPUSTM, which consists of USTM and Differential Phase-Shift Keying (DPSK) modulation, is not only easier to improve the spectral efficiency than USTM, but also simpler to demodulate. The novel modulation can achieve low bit error rate as UST signals and be exploited in multi-rate data communication. The simulation results not only verify the theoretical analysis, but also show that DPUSTM provides a better performance than USTM and DSTM.
2004, 26(7): 1017-1023.
Abstract:
Signal-to-Noise SKew Ratio (SNSKR) is defined and its mathematical formula is obtained. A novel analysis based on the SNSKR is presented. When ambient noise is asymmetrical distributed noise, the SNSKR is equal to or greater than the original Signal-to-Noise Ratio(SNR); whereas the SNSKR is theoretically infinite value if ambient noise is symmetrical distributed noise. Theoretic analysis and simulation results have shown that the analysis is valid and that it is unnecessary to assume that the ambient noise is Gaussian distribution or asymmetrical distribution when employing third-order cumulant slices extracts the underwater target-radiated quadratic phase dynamic coupling signals. These conclusions are significance in engineering.
Signal-to-Noise SKew Ratio (SNSKR) is defined and its mathematical formula is obtained. A novel analysis based on the SNSKR is presented. When ambient noise is asymmetrical distributed noise, the SNSKR is equal to or greater than the original Signal-to-Noise Ratio(SNR); whereas the SNSKR is theoretically infinite value if ambient noise is symmetrical distributed noise. Theoretic analysis and simulation results have shown that the analysis is valid and that it is unnecessary to assume that the ambient noise is Gaussian distribution or asymmetrical distribution when employing third-order cumulant slices extracts the underwater target-radiated quadratic phase dynamic coupling signals. These conclusions are significance in engineering.
2004, 26(7): 1024-1029.
Abstract:
This paper does more research on families of dyadic complementary codes pairs. Firstly, a new block design(dyadic addition set pairs) is presented. Secondly, the equivalent relationship between families of dyadic complementary code pairs and the new block design is given. Finally, families of dyadic complementary code pairs are constructed.
This paper does more research on families of dyadic complementary codes pairs. Firstly, a new block design(dyadic addition set pairs) is presented. Secondly, the equivalent relationship between families of dyadic complementary code pairs and the new block design is given. Finally, families of dyadic complementary code pairs are constructed.
2004, 26(7): 1030-1037.
Abstract:
In this paper, a low-complexity DOA estimation algorithm is presented for asynchronous DS-CDMA systems with multipath propagation. First, the influence of multiacess interferences and noise is eliminated. Then, a group of correlation matrices constituted by the interested DOAs is derived. Finally, according to the conventional MUSIC algorithm, DOAs are resolved preciously from the above matrices. The algorithm has the advantages of low computation burden and high resolution. Simulation results confirm the effectiveness of the algorithm.
In this paper, a low-complexity DOA estimation algorithm is presented for asynchronous DS-CDMA systems with multipath propagation. First, the influence of multiacess interferences and noise is eliminated. Then, a group of correlation matrices constituted by the interested DOAs is derived. Finally, according to the conventional MUSIC algorithm, DOAs are resolved preciously from the above matrices. The algorithm has the advantages of low computation burden and high resolution. Simulation results confirm the effectiveness of the algorithm.
2004, 26(7): 1038-1044.
Abstract:
In TDD-CDMA system, the different asymmetrical requirements between uplink (UL) and downlink (DL) in different Base Station (BS) and different time will generate serious inter-cell interference. From the interference point of view, Dynamic Channel Allocation (DCA) is treated mandatorily on TDD-CDMA systems. In this paper, a novel and advanced DCA algorithm is presented, which is based on radio resource reserving related to pathloss assistance and BS-BS interference resolving mechanisms. Simulation results show the novel DCA can work better than the traditional DCA schemes for asymmetrical traffic.
In TDD-CDMA system, the different asymmetrical requirements between uplink (UL) and downlink (DL) in different Base Station (BS) and different time will generate serious inter-cell interference. From the interference point of view, Dynamic Channel Allocation (DCA) is treated mandatorily on TDD-CDMA systems. In this paper, a novel and advanced DCA algorithm is presented, which is based on radio resource reserving related to pathloss assistance and BS-BS interference resolving mechanisms. Simulation results show the novel DCA can work better than the traditional DCA schemes for asymmetrical traffic.
2004, 26(7): 1045-1052.
Abstract:
Several emerging internet services by multicast force the research on secure multicast, and the research on key update is a big challenge. This paper designs a hash function of variable message digest and variable key length for a key update protocol that is proposed based on time stream, and analysises the overall performances for the protocol.
Several emerging internet services by multicast force the research on secure multicast, and the research on key update is a big challenge. This paper designs a hash function of variable message digest and variable key length for a key update protocol that is proposed based on time stream, and analysises the overall performances for the protocol.
2004, 26(7): 1053-1056.
Abstract:
A new key management scheme applied for large dynamic multicast group is proposed in this paper. In the hierarchical structure one-way hash chain is used as transmission key to transmit the data between the levels. Digital envelope is used to realize key management in subgroups. This scheme is of good attributes in computation, storage and dynamic security. It provides a valuable reference to further study.
A new key management scheme applied for large dynamic multicast group is proposed in this paper. In the hierarchical structure one-way hash chain is used as transmission key to transmit the data between the levels. Digital envelope is used to realize key management in subgroups. This scheme is of good attributes in computation, storage and dynamic security. It provides a valuable reference to further study.
2004, 26(7): 1057-1063.
Abstract:
The security of several typical chaotic synchronized secure communication schemes , as well as the respective unmasking methods are studied to find the way to improve the security. A new secure communication scheme based on active-passive decomposition using parameters perturbation technique, which makes it has a kind of dynamic secrete key, is analyzed in this paper. The dynamic secrete key contributes to the capacity against the unmasking methods. Computer simulation and security test results demonstrate that the scheme is high in security and good in synchronization properties , and that it is safe to the attack of the unmasking methods mentioned in this paper.
The security of several typical chaotic synchronized secure communication schemes , as well as the respective unmasking methods are studied to find the way to improve the security. A new secure communication scheme based on active-passive decomposition using parameters perturbation technique, which makes it has a kind of dynamic secrete key, is analyzed in this paper. The dynamic secrete key contributes to the capacity against the unmasking methods. Computer simulation and security test results demonstrate that the scheme is high in security and good in synchronization properties , and that it is safe to the attack of the unmasking methods mentioned in this paper.
Image Compression Based on Integer Wavelet Transform and Improved Embedded Zerotree Wavelet Encoding
2004, 26(7): 1064-1069.
Abstract:
The main advantages of Integer Wavelet Transform(IWT) are that the input and output values are all integers, all operations can be done in place, only a small memory is required and easy to be implemented in hardware. In the context of image coding, IWT is well suited for lossless compression. However, it performs a little worse compared to the conventional Discrete Wavelet Transform(DWT) for lossy compression. In this paper, a new algorithm is proposed for improving lossy compression performance of IWT, It is by means of the IWT based on lifting scheme combining with improved Embedded Zerotree Wavelet(EZW) based on morphological dilation operation. Simulation results show the proposed algorithm improves the Peak Signal Noise Ratio(PSNR) compared to conventional DWT without increasing computational complexity.
The main advantages of Integer Wavelet Transform(IWT) are that the input and output values are all integers, all operations can be done in place, only a small memory is required and easy to be implemented in hardware. In the context of image coding, IWT is well suited for lossless compression. However, it performs a little worse compared to the conventional Discrete Wavelet Transform(DWT) for lossy compression. In this paper, a new algorithm is proposed for improving lossy compression performance of IWT, It is by means of the IWT based on lifting scheme combining with improved Embedded Zerotree Wavelet(EZW) based on morphological dilation operation. Simulation results show the proposed algorithm improves the Peak Signal Noise Ratio(PSNR) compared to conventional DWT without increasing computational complexity.
2004, 26(7): 1070-1075.
Abstract:
A kind of interpolator, called the modified pixel-filled interpolator, is advanced for images enlarged the same integer times in lines as that in columns. The principle a.iul the implement method in software and hardware of the interpolator are given, Comparing with the nearest neighbor interpolator, the bilinear interpolator, the pixol-exchanged-intcrpolator and the wavelet-based zooming methods, the effects of enlarged images with this interpolator are better according to the subjective and objective evaluation to the enlarged images. Its implementation in software and hardware is easy, and can be applied to all kinds of image zooming.
A kind of interpolator, called the modified pixel-filled interpolator, is advanced for images enlarged the same integer times in lines as that in columns. The principle a.iul the implement method in software and hardware of the interpolator are given, Comparing with the nearest neighbor interpolator, the bilinear interpolator, the pixol-exchanged-intcrpolator and the wavelet-based zooming methods, the effects of enlarged images with this interpolator are better according to the subjective and objective evaluation to the enlarged images. Its implementation in software and hardware is easy, and can be applied to all kinds of image zooming.
2004, 26(7): 1076-1081.
Abstract:
A multi-level elimination algorithm for fast motion estimation is proposed in this paper. The most matched block of the current block is detected in the next frame with a multi-level elimination strategy in this algorithm. In the first level, some candidate blocks are eliminated by simple characters based blockmatching, needing only very few computation costs. Then in further levels, more detailed characters are used for block-matching to eliminate more candidate blocks until the most matched block is selected in the last level. Experimental results show that the proposed algorithm can work steadily and get very close performance to the full-search algorithm while a computation reduction of about 12~14 times, with respect to the full-search algorithm.
A multi-level elimination algorithm for fast motion estimation is proposed in this paper. The most matched block of the current block is detected in the next frame with a multi-level elimination strategy in this algorithm. In the first level, some candidate blocks are eliminated by simple characters based blockmatching, needing only very few computation costs. Then in further levels, more detailed characters are used for block-matching to eliminate more candidate blocks until the most matched block is selected in the last level. Experimental results show that the proposed algorithm can work steadily and get very close performance to the full-search algorithm while a computation reduction of about 12~14 times, with respect to the full-search algorithm.
2004, 26(7): 1082-1087.
Abstract:
In this paper, Dolby AC3 standard is used as the audio decoding standard to research the hardware/software co-design method of HDTV audio decoding based on Virgo-IP-Core and a new method is present to realize the hardware/software partition by setting models for the key sub-functions of AC3 decoding program. That is, after decoding AC3 bit stream by software, the models are set up for the key sub-functions to get the extended instructions of RISC core. Through this extension, the speed of AC3 decoding is fastened, the memory space is reduced and the gates of the whole system are lessened. Next, the detail hardware of extended instruction is given. Finally, the performance of the whole system is analyzed by using the hardware/software co-evaluation method.
In this paper, Dolby AC3 standard is used as the audio decoding standard to research the hardware/software co-design method of HDTV audio decoding based on Virgo-IP-Core and a new method is present to realize the hardware/software partition by setting models for the key sub-functions of AC3 decoding program. That is, after decoding AC3 bit stream by software, the models are set up for the key sub-functions to get the extended instructions of RISC core. Through this extension, the speed of AC3 decoding is fastened, the memory space is reduced and the gates of the whole system are lessened. Next, the detail hardware of extended instruction is given. Finally, the performance of the whole system is analyzed by using the hardware/software co-evaluation method.
2004, 26(7): 1088-1093.
Abstract:
The effect of the multiple-user interference, the receiver shot noise, ambient light interference, the receiver dark current and the thermal noise are taken into account. A probability union bound and the pessimistic estimation method are used that decision errors may occur on condition that two decision measurements are equal. The upper bounds of the bit error (BER) of infrared Overlapping Pulse-Position Modulation (OPPM)/Code Division Multiple Access (CDMA) correlation receiver without optical hard-limiters, with single optical hard-limiters and with double optical hard-limiters for arbitrary AQ and Ac are derived. Moreover, the performance analysis and comparisons for aforementioned three receivers are presented by computer simulation.
The effect of the multiple-user interference, the receiver shot noise, ambient light interference, the receiver dark current and the thermal noise are taken into account. A probability union bound and the pessimistic estimation method are used that decision errors may occur on condition that two decision measurements are equal. The upper bounds of the bit error (BER) of infrared Overlapping Pulse-Position Modulation (OPPM)/Code Division Multiple Access (CDMA) correlation receiver without optical hard-limiters, with single optical hard-limiters and with double optical hard-limiters for arbitrary AQ and Ac are derived. Moreover, the performance analysis and comparisons for aforementioned three receivers are presented by computer simulation.
2004, 26(7): 1094-1100.
Abstract:
When the total transmitting power is limited, the authors investigate the effect of different power allocation schemes on the side-information and the arithmetic to obtain the optimal power allocation coefficient for the system with Partial Transmit Sequences (PTS). Besides, the authors propose a new simple arithmetic to obtain the sub-optimal coefficient. The simulation results indicate that reducing a little power on every data carrier will obtain large gain on side-information carriers. With increasing the signal to noise ratio, the system is apt to averagely allocate the total power on every carrier. The bit error rate with the optimal or sub-optimal coefficient is close to the ideal value.
When the total transmitting power is limited, the authors investigate the effect of different power allocation schemes on the side-information and the arithmetic to obtain the optimal power allocation coefficient for the system with Partial Transmit Sequences (PTS). Besides, the authors propose a new simple arithmetic to obtain the sub-optimal coefficient. The simulation results indicate that reducing a little power on every data carrier will obtain large gain on side-information carriers. With increasing the signal to noise ratio, the system is apt to averagely allocate the total power on every carrier. The bit error rate with the optimal or sub-optimal coefficient is close to the ideal value.
2004, 26(7): 1101-1106.
Abstract:
The congestion control mechanisms used in Internet have been the focus of numerous studies and have undergone a number of enhancements. However, even with these enhancements, TCP connections still experience alarmingly high loss rates, especially during times of congestion. The IETF has addressed this problem by advocating the deployment of active queue management mechanisms, such as RED, in the network, But RED have some problems, for example the average queue length changing slowly when congestion starting and ending. To alleviate this problem, a Dynamic-Weight RED(DWRED) is proposed which can quickly be conscious of the congestion and dynamic adjust the weight. DWRED use the average queue length to estimate the change of the queue and adjust the weight to alleviate the congestion and drop when the congestion is over. The time of congestion is shorter than the RED. The result is proved by the simulation.
The congestion control mechanisms used in Internet have been the focus of numerous studies and have undergone a number of enhancements. However, even with these enhancements, TCP connections still experience alarmingly high loss rates, especially during times of congestion. The IETF has addressed this problem by advocating the deployment of active queue management mechanisms, such as RED, in the network, But RED have some problems, for example the average queue length changing slowly when congestion starting and ending. To alleviate this problem, a Dynamic-Weight RED(DWRED) is proposed which can quickly be conscious of the congestion and dynamic adjust the weight. DWRED use the average queue length to estimate the change of the queue and adjust the weight to alleviate the congestion and drop when the congestion is over. The time of congestion is shorter than the RED. The result is proved by the simulation.
2004, 26(7): 1107-1113.
Abstract:
In saturated IEEE 802.11 WLAN, the energy consumption in transmission per frame through basic mode and RTS/CTS mode is analyzed through mathematical model. The relation of RTS threshold and average energy consumption per frame is produced in the assumption that the frame payloads length is distributed in a given interval. Further analysis shows there is an optimum RTS threshold that can minimize the average energy consumption. The method of calculating optimum RTS threshold is also presented. All theoretical analysis is validated through computer simulation.
In saturated IEEE 802.11 WLAN, the energy consumption in transmission per frame through basic mode and RTS/CTS mode is analyzed through mathematical model. The relation of RTS threshold and average energy consumption per frame is produced in the assumption that the frame payloads length is distributed in a given interval. Further analysis shows there is an optimum RTS threshold that can minimize the average energy consumption. The method of calculating optimum RTS threshold is also presented. All theoretical analysis is validated through computer simulation.
2004, 26(7): 1114-1119.
Abstract:
In WDM networks, the bandwidth request of a traffic stream can be much lower than the capacity of a wavelength. Traffic grooming can aggregate low-rate connections onto high-capacity lightpaths to make full use of the bandwidth. But most of the researches related to traffic grooming has focused on ring networks, and fewer concerns are about the dependable traffic grooming of low-rate connections in WDM mesh networks. In this paper, a Shared Protection Traffic Grooming algorithm is proposed based on wavelength Layered-Graph (SPTG-LG) considering both the survivability and traffic grooming in WDM mesh networks. Some simulations and analysis are also given out.
In WDM networks, the bandwidth request of a traffic stream can be much lower than the capacity of a wavelength. Traffic grooming can aggregate low-rate connections onto high-capacity lightpaths to make full use of the bandwidth. But most of the researches related to traffic grooming has focused on ring networks, and fewer concerns are about the dependable traffic grooming of low-rate connections in WDM mesh networks. In this paper, a Shared Protection Traffic Grooming algorithm is proposed based on wavelength Layered-Graph (SPTG-LG) considering both the survivability and traffic grooming in WDM mesh networks. Some simulations and analysis are also given out.
2004, 26(7): 1120-1125.
Abstract:
Design and realization of a real-time high-resolution SAR data processing system is proposed. By the adoption of PowerPC G4 as DSP, VME as system bus and RACE++ as high speed data exchange path, this stable system has great performance and flexible expansibility. To fit different requirement of real-time SAR data processing system, variable performance can be achieved by simply extension.
Design and realization of a real-time high-resolution SAR data processing system is proposed. By the adoption of PowerPC G4 as DSP, VME as system bus and RACE++ as high speed data exchange path, this stable system has great performance and flexible expansibility. To fit different requirement of real-time SAR data processing system, variable performance can be achieved by simply extension.
2004, 26(7): 1126-1130.
Abstract:
This paper studies the imaging of moving target in the situation of the bistatic synthetic aperture radar with stationary transmitter. The WVD-Radon method is used to estimate the Doppler frequency parameter of the moving target, and to adjust the parameter of the imaging and the motion compensation to get better imaging result. The results of computer simulation are given to demonstrate that the conclusion of the paper is correct.
This paper studies the imaging of moving target in the situation of the bistatic synthetic aperture radar with stationary transmitter. The WVD-Radon method is used to estimate the Doppler frequency parameter of the moving target, and to adjust the parameter of the imaging and the motion compensation to get better imaging result. The results of computer simulation are given to demonstrate that the conclusion of the paper is correct.
2004, 26(7): 1131-1136.
Abstract:
Using the perfect properties of Radial Basis Function (RBF) neural networks, such as approximation any non-linear mapping and quick convergence, a new scheme is proposed to estimate scaling factors for radar CFAR detectors. Owing to few constraints, it can estimate scaling factor for single radar as well as radar netting system. The numerical results indicate that the proposed scheme can quickly reach high estimation accuracy for most CFAR detectors.
Using the perfect properties of Radial Basis Function (RBF) neural networks, such as approximation any non-linear mapping and quick convergence, a new scheme is proposed to estimate scaling factors for radar CFAR detectors. Owing to few constraints, it can estimate scaling factor for single radar as well as radar netting system. The numerical results indicate that the proposed scheme can quickly reach high estimation accuracy for most CFAR detectors.
2004, 26(7): 1137-1143.
Abstract:
Eigen-subspace and canonical-subspace methods are studied and applied to feature-extraction for target recognition using range profiles of a High-range-Resolution-Radar (HRR) system. Based on this study, a subspace cluster method is proposed to tackle the problem of aspect-sensitivity of range profiles. In subspace cluster method, the aspect scope of a radar target is divided into a proper number of zones, and eigen-subspaces are established for each zone. After the zone number of an unknown target is determined by radar, the range profile of this target is mapped into eigen-subspaces of the corresponding zone, and the class whose subspace has the maximum mapping energy is judged as the right class to which the unknown target belongs. This method is named as single-mode classification rule in the subspace cluster method. Experimental results on simulated data and field data show the efficiency of the subspace methods and subspace cluster method in target recognition.
Eigen-subspace and canonical-subspace methods are studied and applied to feature-extraction for target recognition using range profiles of a High-range-Resolution-Radar (HRR) system. Based on this study, a subspace cluster method is proposed to tackle the problem of aspect-sensitivity of range profiles. In subspace cluster method, the aspect scope of a radar target is divided into a proper number of zones, and eigen-subspaces are established for each zone. After the zone number of an unknown target is determined by radar, the range profile of this target is mapped into eigen-subspaces of the corresponding zone, and the class whose subspace has the maximum mapping energy is judged as the right class to which the unknown target belongs. This method is named as single-mode classification rule in the subspace cluster method. Experimental results on simulated data and field data show the efficiency of the subspace methods and subspace cluster method in target recognition.
2004, 26(7): 1144-1149.
Abstract:
A fast effective algorithm is developed for the road identification problem in ground target tracking. A mathematic model of road identification problem is provided and the problem is related with a positive definite quadratic programming problem with inequality constraints. The optimality conditions are given and a road identification method based on active set algorithm is proposed. The two different simulation examples verify the feasibility and efficiency of the above algorithm.
A fast effective algorithm is developed for the road identification problem in ground target tracking. A mathematic model of road identification problem is provided and the problem is related with a positive definite quadratic programming problem with inequality constraints. The optimality conditions are given and a road identification method based on active set algorithm is proposed. The two different simulation examples verify the feasibility and efficiency of the above algorithm.
2004, 26(7): 1150-1156.
Abstract:
Since the information fails to be expressed integrally in the agent organization model constructed by the single Aalaadin meta-model and it appears difficult in directly modeling with Agent Unified Modeling Language (AUML), a new modeling method (i.e. Aalaadin-AUML modeling method) combining the Aalaadin meta-model with AUML is presented after pointing out the existing mutual supplements in the both. Taking an agent organization of the distribution management in e-business for example, the modeling process is introduced based on this new method. As it is proved by practice, Aalaadin-AUML modeling method expends the ability of information expression and unifies the notion and understanding in the organization model of multi-agent system.
Since the information fails to be expressed integrally in the agent organization model constructed by the single Aalaadin meta-model and it appears difficult in directly modeling with Agent Unified Modeling Language (AUML), a new modeling method (i.e. Aalaadin-AUML modeling method) combining the Aalaadin meta-model with AUML is presented after pointing out the existing mutual supplements in the both. Taking an agent organization of the distribution management in e-business for example, the modeling process is introduced based on this new method. As it is proved by practice, Aalaadin-AUML modeling method expends the ability of information expression and unifies the notion and understanding in the organization model of multi-agent system.
2004, 26(7): 1157-1162.
Abstract:
In the light of most current segmentation algorithms are of high complexity and huge computation, one algorithm of coarse segmentation in compressed domain and refined segmentation in spatial domain is put forward. The initial coarse segmentation masks from the motion vectors are obtained by applying Estimation Maximum(EM) algorithm. These blocks in the masks can be decompressed to obtain the origin image and the actual edges of the objects can be extracted by applying Canny edge detection and edge tracking only in the segmented regions. By using the proposed algorithm, the amount of data needed to be processed is kept in necessarily minimal, saving the computation time as well as gaining the pixel-wise edges of the segmented objects.
In the light of most current segmentation algorithms are of high complexity and huge computation, one algorithm of coarse segmentation in compressed domain and refined segmentation in spatial domain is put forward. The initial coarse segmentation masks from the motion vectors are obtained by applying Estimation Maximum(EM) algorithm. These blocks in the masks can be decompressed to obtain the origin image and the actual edges of the objects can be extracted by applying Canny edge detection and edge tracking only in the segmented regions. By using the proposed algorithm, the amount of data needed to be processed is kept in necessarily minimal, saving the computation time as well as gaining the pixel-wise edges of the segmented objects.
2004, 26(7): 1163-1167.
Abstract:
This paper researches mainly 011 the network traffic sampling measurement methods. The Stratified Random Double Sampling method based on Event-driven (ESRDS) is proposed. Its performance is proved to be better than traditional methods in analyzing the length and interval of packets according to simulation experiments. Especially, estimated interval time of packages by this method is nearly real. It also researches on the measurement methods in the calculating Hurst coefficient. According to the estimation of Hurst coefficient using ESRDS method, the error is much less between estimated and real values.
This paper researches mainly 011 the network traffic sampling measurement methods. The Stratified Random Double Sampling method based on Event-driven (ESRDS) is proposed. Its performance is proved to be better than traditional methods in analyzing the length and interval of packets according to simulation experiments. Especially, estimated interval time of packages by this method is nearly real. It also researches on the measurement methods in the calculating Hurst coefficient. According to the estimation of Hurst coefficient using ESRDS method, the error is much less between estimated and real values.
2004, 26(7): 1168-1172.
Abstract:
Spaceborne Electronic Power Controller(EPC) works in severe environment and its lifetime must be over 3 years. Therefore its reliability should be under great consideration. This paper, analyzes on the reliability of EPC used in weather satellite and the estimations of its A and Mean Time Between Failures(MTBF) are given.
Spaceborne Electronic Power Controller(EPC) works in severe environment and its lifetime must be over 3 years. Therefore its reliability should be under great consideration. This paper, analyzes on the reliability of EPC used in weather satellite and the estimations of its A and Mean Time Between Failures(MTBF) are given.
2004, 26(7): 1173-1176.
Abstract:
In this paper, a method of automatic gain control for synthetic aperture radar is given. In this way, radar signal is processed in two dimensions. Comparison to the traditional AGC, this method keeps the properties of signal and widens the dynamic range of the receiver. Then the operation mode and coefficient of 2-Dimensional AGC are described, and the computer simulation results and the real radar image are given.
In this paper, a method of automatic gain control for synthetic aperture radar is given. In this way, radar signal is processed in two dimensions. Comparison to the traditional AGC, this method keeps the properties of signal and widens the dynamic range of the receiver. Then the operation mode and coefficient of 2-Dimensional AGC are described, and the computer simulation results and the real radar image are given.
