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2004 Vol. 26, No. 10
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2004, 26(10): 1513-1520.
Abstract:
This paper presents two effective bandwidth estimation methods for connection admission control in satellite ATM networks with Adaptive FEC (AFEC). Due to the dynamic code rate of AFEC, its effect would be taken into account in estimating the effective bandwidth. A fluid approximation method is first applied to estimate the effective bandwidth values for general time-varying satellite channels and satellite ATM network with multiple-code-rate AFEC. But the requirements of the method are strict and its computing complexity is high for practical purposes. Based on this method, the authors propose a second estimation method by using a modification factor. the numerical results show the second method is simple and effective and widely applicable.
This paper presents two effective bandwidth estimation methods for connection admission control in satellite ATM networks with Adaptive FEC (AFEC). Due to the dynamic code rate of AFEC, its effect would be taken into account in estimating the effective bandwidth. A fluid approximation method is first applied to estimate the effective bandwidth values for general time-varying satellite channels and satellite ATM network with multiple-code-rate AFEC. But the requirements of the method are strict and its computing complexity is high for practical purposes. Based on this method, the authors propose a second estimation method by using a modification factor. the numerical results show the second method is simple and effective and widely applicable.
2004, 26(10): 1521-1526.
Abstract:
This paper focuses on the mobility management in hierarchical multi-hop mobile wireless networks. A mobility management solution is proposed which combines macro mobility management using Logical Home Agent (LHA) and micro mobility management integrating location management with routing and paging. The main advantage of this scheme is that it considerably reduces the location update overhead and especially cares for reliability and survivability.
This paper focuses on the mobility management in hierarchical multi-hop mobile wireless networks. A mobility management solution is proposed which combines macro mobility management using Logical Home Agent (LHA) and micro mobility management integrating location management with routing and paging. The main advantage of this scheme is that it considerably reduces the location update overhead and especially cares for reliability and survivability.
2004, 26(10): 1527-1533.
Abstract:
The MAC layer of the IEEE 802.11 standard adopts an exponential backoff scheme to access media. This paper provides an enhanced backoff scheme, which changes Contending Windows(CW) adaptively by estimating the number of active stations in network to improve the efficiency of network.
The MAC layer of the IEEE 802.11 standard adopts an exponential backoff scheme to access media. This paper provides an enhanced backoff scheme, which changes Contending Windows(CW) adaptively by estimating the number of active stations in network to improve the efficiency of network.
2004, 26(10): 1534-1539.
Abstract:
In the Optical Burst Switching (OBS) network, the data channel scheduling is one of key issues. Bandwidth efficiency and QoS support are the two concerned focuses. However, the existing algorithms pay more attentions to bandwidth efficiency. In this paper, BM-VF-SBD, an efficient data channel scheduling algorithm is developed. It effectively integrates void filling, burst migration and selective burst discard to reduce the bandwidth fragment and support QoS. Its basic idea is in that a new burst is scheduled by migrating some bursts to other channels if none of voids in any channels can accommodate it; otherwise repeating the above processes after selectively dropping some bursts. Meanwhile under the balanced binary search tree data structure, its computational complexity will be O((2w + 1) log w) at most, and be close to that of LAUC-VF and ODBR, In the proposed algorithm, burst migration plays a key role in the improvement of bandwidth efficiency while selective burst discard has great effects on the two sides. The simulation results show that it performs much better than LAUC-VF and ODBR in burst loss probability (overall or individual) and bandwidth fragment ratio.
In the Optical Burst Switching (OBS) network, the data channel scheduling is one of key issues. Bandwidth efficiency and QoS support are the two concerned focuses. However, the existing algorithms pay more attentions to bandwidth efficiency. In this paper, BM-VF-SBD, an efficient data channel scheduling algorithm is developed. It effectively integrates void filling, burst migration and selective burst discard to reduce the bandwidth fragment and support QoS. Its basic idea is in that a new burst is scheduled by migrating some bursts to other channels if none of voids in any channels can accommodate it; otherwise repeating the above processes after selectively dropping some bursts. Meanwhile under the balanced binary search tree data structure, its computational complexity will be O((2w + 1) log w) at most, and be close to that of LAUC-VF and ODBR, In the proposed algorithm, burst migration plays a key role in the improvement of bandwidth efficiency while selective burst discard has great effects on the two sides. The simulation results show that it performs much better than LAUC-VF and ODBR in burst loss probability (overall or individual) and bandwidth fragment ratio.
2004, 26(10): 1540-1547.
Abstract:
This paper presents a novel round robin based fully distributed fair queuing algorithm for IEEE 802.11 WLANs. The proposed algorithm in this paper achieves fair scheduling in a distributed environment by doing a small modification to the distributed coordination function of the IEEE 802.11 MAC protocol. Simulation results show this algorithm is effective.
This paper presents a novel round robin based fully distributed fair queuing algorithm for IEEE 802.11 WLANs. The proposed algorithm in this paper achieves fair scheduling in a distributed environment by doing a small modification to the distributed coordination function of the IEEE 802.11 MAC protocol. Simulation results show this algorithm is effective.
2004, 26(10): 1548-1554.
Abstract:
The OFDM transmitter diversity has gotten more attention in recent years. However, OFDM systems are very sensitive to frequency-offset. Therefore, it is necessary to estimate effectively and to compensate frequency-offset in the systems. This paper presents a blind and adaptive fine frequency-offset estimation method firstly, and then proposes a coarse frequency-offset estimation method based on pilot frequency. Finally, simulation results verify these methods.
The OFDM transmitter diversity has gotten more attention in recent years. However, OFDM systems are very sensitive to frequency-offset. Therefore, it is necessary to estimate effectively and to compensate frequency-offset in the systems. This paper presents a blind and adaptive fine frequency-offset estimation method firstly, and then proposes a coarse frequency-offset estimation method based on pilot frequency. Finally, simulation results verify these methods.
2004, 26(10): 1555-1561.
Abstract:
In this paper a novel dynamic channel allocation algorithm based on network optimization in CDMA network is presented. It establishes an integer programming model for CBR services, which does not allocate channel at each time slot but at some time slots. The goal is to trade off between the QoS for users and system performance. The simulation results show that this optimal algorithm both improves the channel usage and guarantees the QoS, compared with traditional voice-allocated-first algorithm and queue-by-priority allocation algorithm.
In this paper a novel dynamic channel allocation algorithm based on network optimization in CDMA network is presented. It establishes an integer programming model for CBR services, which does not allocate channel at each time slot but at some time slots. The goal is to trade off between the QoS for users and system performance. The simulation results show that this optimal algorithm both improves the channel usage and guarantees the QoS, compared with traditional voice-allocated-first algorithm and queue-by-priority allocation algorithm.
2004, 26(10): 1562-1568.
Abstract:
This paper focuses on the anti-interference technique to restrain the interfer-ence of co-channel users while simply introducing the concept of space-time block coding. Anti-interference technique uses the relationship among signals to remove the interference, which can enhance the capacity of communication system by introducing co-channel users. Moreover, the paper submits a strategy to eliminate the effect of co-channel interference by decoding signals by stages while using different performance of various modulation tech-niques. The system performance can get more enhancements by using this strategy, which is very important for enlarging the capacity of system.
This paper focuses on the anti-interference technique to restrain the interfer-ence of co-channel users while simply introducing the concept of space-time block coding. Anti-interference technique uses the relationship among signals to remove the interference, which can enhance the capacity of communication system by introducing co-channel users. Moreover, the paper submits a strategy to eliminate the effect of co-channel interference by decoding signals by stages while using different performance of various modulation tech-niques. The system performance can get more enhancements by using this strategy, which is very important for enlarging the capacity of system.
2004, 26(10): 1569-1574.
Abstract:
In this paper, a carrier frequency offset estimation and tracking scheme for OFDM is presented. Pilot-Symbol-Aided (PSA) estimation is used to estimate carrier frequency offset in OFDM system, and the carrier frequency tracking applies the cyclic prefix. The simulation results prove the PSA estimation of frequency offset is precise, and the carrier frequency tracking is available.
In this paper, a carrier frequency offset estimation and tracking scheme for OFDM is presented. Pilot-Symbol-Aided (PSA) estimation is used to estimate carrier frequency offset in OFDM system, and the carrier frequency tracking applies the cyclic prefix. The simulation results prove the PSA estimation of frequency offset is precise, and the carrier frequency tracking is available.
2004, 26(10): 1575-1579.
Abstract:
This paper proposed a fast, simple, robust and precise scheme of frequency offset estimation within a great range with lower SNR in the context of the Synchronized Multi-Carrier CDMA plus (SMCC+) system, which is one of the candidate standard of digital terrestrial multimedia/TV broadcasting transmission in China, and COFDM systems based on short Pseudo Noise sequence (PN-sequence) reconstructed by a special method. Computer simulation results show the proposed technique get better properties than the conventional frequency synchronization method.
This paper proposed a fast, simple, robust and precise scheme of frequency offset estimation within a great range with lower SNR in the context of the Synchronized Multi-Carrier CDMA plus (SMCC+) system, which is one of the candidate standard of digital terrestrial multimedia/TV broadcasting transmission in China, and COFDM systems based on short Pseudo Noise sequence (PN-sequence) reconstructed by a special method. Computer simulation results show the proposed technique get better properties than the conventional frequency synchronization method.
2004, 26(10): 1580-1586.
Abstract:
In this paper, the performance of the LDPC coded MIMO system scheme is evaluated through numerical simulations, and according to the belief propagation decoding algorithm of LDPC codes, a combined iterative detection/decoding MAP algorithm based on the factor-graph representation is proposed. The system performance is analyzed under two transmitter encoding structures, namely the separate encoding structure and the combined encoding structure respectively. Simulation results show that LDPC codes can increase the effective diversity gain by utilizing both the space and the time diversity effects of the MIMO system, and the combined iterative detection/decoding algorithm results in different performance gain for the two transmitter encoding structures.
In this paper, the performance of the LDPC coded MIMO system scheme is evaluated through numerical simulations, and according to the belief propagation decoding algorithm of LDPC codes, a combined iterative detection/decoding MAP algorithm based on the factor-graph representation is proposed. The system performance is analyzed under two transmitter encoding structures, namely the separate encoding structure and the combined encoding structure respectively. Simulation results show that LDPC codes can increase the effective diversity gain by utilizing both the space and the time diversity effects of the MIMO system, and the combined iterative detection/decoding algorithm results in different performance gain for the two transmitter encoding structures.
2004, 26(10): 1587-1593.
Abstract:
This paper deals with frame detection of OFDM signal with multiple-periodic preambles transmitted over frequency-selective channels and with existence of carrier fre-quency offset. Involving effect of AGC (Automatic Gain Control), frame detection can be taken as a hypothesis test model with unknown parameters. By applying generalized log-likelihood ratio testing to this model, a simple CFAR (Constant False-Alarm Rate) detector that is insensitive to frequency offset is derived. Parametric generalized lambda distribution is utilized to fit the statistical characteristic of detector when only noise exists, which is then used by Neyman-Pearson rule to determine decision threshold at given false alarm proba-bility. Finally, computer simulations achieve detection performance of the obtained frame detector.
This paper deals with frame detection of OFDM signal with multiple-periodic preambles transmitted over frequency-selective channels and with existence of carrier fre-quency offset. Involving effect of AGC (Automatic Gain Control), frame detection can be taken as a hypothesis test model with unknown parameters. By applying generalized log-likelihood ratio testing to this model, a simple CFAR (Constant False-Alarm Rate) detector that is insensitive to frequency offset is derived. Parametric generalized lambda distribution is utilized to fit the statistical characteristic of detector when only noise exists, which is then used by Neyman-Pearson rule to determine decision threshold at given false alarm proba-bility. Finally, computer simulations achieve detection performance of the obtained frame detector.
2004, 26(10): 1594-1600.
Abstract:
A new optimum algorithm is proposed for frequency estimation from a train of coherent pulses in additive Gaussian noise, named it as multi-stages frequency estimation algorithm. It is shown to be a optimum algorithm with small computation and high corrective possibility. Simulations are given to support these conclusion.
A new optimum algorithm is proposed for frequency estimation from a train of coherent pulses in additive Gaussian noise, named it as multi-stages frequency estimation algorithm. It is shown to be a optimum algorithm with small computation and high corrective possibility. Simulations are given to support these conclusion.
2004, 26(10): 1601-1606.
Abstract:
In this paper Parallel Hidden Markov Model (PHMM) made up of several par-allel Markov chains is proposed to fit in with speaker-independent speech recognition. The performance is improved because of the fusion of different models from classification based speech recognition. By sharing states of fused models, making classification automatically during training and getting result from all classifications, the amount of storage and operation can be decreased. The experiment for speaker-independent recognition of mandarin isolated digit shows that the PHMM improves the recognition performance and noise robustness.
In this paper Parallel Hidden Markov Model (PHMM) made up of several par-allel Markov chains is proposed to fit in with speaker-independent speech recognition. The performance is improved because of the fusion of different models from classification based speech recognition. By sharing states of fused models, making classification automatically during training and getting result from all classifications, the amount of storage and operation can be decreased. The experiment for speaker-independent recognition of mandarin isolated digit shows that the PHMM improves the recognition performance and noise robustness.
2004, 26(10): 1607-1612.
Abstract:
In this paper, a speaker identification system is proposed based on classify Fea-ture Sub-space Gaussian Mixture Model and Neural Net fusion (FS-GMM/NN) . With clus-tering analysis of the feature vectors, the speakers training feature vectors can be classified to some subsets and training classify Gaussian Mixture Models (GMM) with different mix-tures according to the subsets feature vectorss number. Finally, the outputs of every classify GMM will be fused by Neural Net (NN). In the experiment of text-independent speaker iden-tification of 100 speakers (male), the system based on FS-GMM/NN overmatch the Baseline Gaussian Mixture Model (B-GMM) in identification performance and noise robustness with fewer mixtures and shorter test speech. Moreover, the training of FS-GMM/NN is more effective.
In this paper, a speaker identification system is proposed based on classify Fea-ture Sub-space Gaussian Mixture Model and Neural Net fusion (FS-GMM/NN) . With clus-tering analysis of the feature vectors, the speakers training feature vectors can be classified to some subsets and training classify Gaussian Mixture Models (GMM) with different mix-tures according to the subsets feature vectorss number. Finally, the outputs of every classify GMM will be fused by Neural Net (NN). In the experiment of text-independent speaker iden-tification of 100 speakers (male), the system based on FS-GMM/NN overmatch the Baseline Gaussian Mixture Model (B-GMM) in identification performance and noise robustness with fewer mixtures and shorter test speech. Moreover, the training of FS-GMM/NN is more effective.
2004, 26(10): 1613-1619.
Abstract:
A novel MultiColor Voronoi Classifier (MCVC) is proposed, which can be ap-plied to linear and nonlinear classification problems. MCVC has sound ability to expend classification plane between samples. With increment of samples, it can be shown that the classification plane of MCVC can close to any classification function. MCVC has very good local ability too. When new learning sample is added, only local classification planed is modified and the whole classification characteristics are not modified greatly. So MCVC can solve the overfitting problem of neural network. Experiments show that MCVC is feasible to linear classification and nonlinear classification problems.
A novel MultiColor Voronoi Classifier (MCVC) is proposed, which can be ap-plied to linear and nonlinear classification problems. MCVC has sound ability to expend classification plane between samples. With increment of samples, it can be shown that the classification plane of MCVC can close to any classification function. MCVC has very good local ability too. When new learning sample is added, only local classification planed is modified and the whole classification characteristics are not modified greatly. So MCVC can solve the overfitting problem of neural network. Experiments show that MCVC is feasible to linear classification and nonlinear classification problems.
2004, 26(10): 1620-1625.
Abstract:
In this paper, a new digital watermarking algorithm based on LU decomposition of matrix is proposed. In order to apply LU decomposition, the corresponding nonnegative matrix of the image is transformed into G-diagonally dominant matrix. In the course of embedding digital watermarking, the scale quantization function is used. The original image is not needed in the recover progress. Experiments are given for contrasting the LU algorithm with DCT mid-frequency coefficient comparison method, and results show that this new-algorithm is robust and easy to embed and extract.
In this paper, a new digital watermarking algorithm based on LU decomposition of matrix is proposed. In order to apply LU decomposition, the corresponding nonnegative matrix of the image is transformed into G-diagonally dominant matrix. In the course of embedding digital watermarking, the scale quantization function is used. The original image is not needed in the recover progress. Experiments are given for contrasting the LU algorithm with DCT mid-frequency coefficient comparison method, and results show that this new-algorithm is robust and easy to embed and extract.
2004, 26(10): 1626-1630.
Abstract:
An Improved Iterative Reprojection Reconstruction (IIRR) from a view of in-tegral equation for incomplete image reconstruction is presented in this paper. IIRR is convergence under L~2 norm. The convergent velocity and the error of the reconstructed image depend on the relaxed parameter, the detected data and some prior information on image. The reconstructed image can be expressed in term of a series of image reconstructed by the detected data. Numerical simulation also shows that IIRR is effective to image reconstruction.
An Improved Iterative Reprojection Reconstruction (IIRR) from a view of in-tegral equation for incomplete image reconstruction is presented in this paper. IIRR is convergence under L~2 norm. The convergent velocity and the error of the reconstructed image depend on the relaxed parameter, the detected data and some prior information on image. The reconstructed image can be expressed in term of a series of image reconstructed by the detected data. Numerical simulation also shows that IIRR is effective to image reconstruction.
2004, 26(10): 1631-1637.
Abstract:
A problem in an algorithm to estimate frequency and orientation of each arrival signal with uniform circular-shaped antenna array is introduced, and a resolvent of this problem is put forward in the paper. The algorithm quoted in this paper includes two methods: direct method and indirect method. As the precision of each arrival signals parameters estimated by direct method is not satisfied, an indirect method grounded on direct method is put forward to improve the precision mentioned above. But, when several single-frequency signals arriving at the same time, parameters of each signal estimated by indirect method cannot always be paired correctly, this paper explains the reason of that, and a method to solve this problem is introduced, the resolvent makes the indirect method more simple and credible than its preceding form.
A problem in an algorithm to estimate frequency and orientation of each arrival signal with uniform circular-shaped antenna array is introduced, and a resolvent of this problem is put forward in the paper. The algorithm quoted in this paper includes two methods: direct method and indirect method. As the precision of each arrival signals parameters estimated by direct method is not satisfied, an indirect method grounded on direct method is put forward to improve the precision mentioned above. But, when several single-frequency signals arriving at the same time, parameters of each signal estimated by indirect method cannot always be paired correctly, this paper explains the reason of that, and a method to solve this problem is introduced, the resolvent makes the indirect method more simple and credible than its preceding form.
2004, 26(10): 1638-1644.
Abstract:
Based on the theory of integral multiwavelet transformation, the representation of 1/f signal (not near-1/f signal) is explored by inverse integral multiwavelet transforma-tion, and the conditions of representing 1/f signal are acquired. The statistical characteris-tics of integral multiwavelets transformation are studied, and it is proved that the self-similar characteristics of 1/f signal can be represented by the autocorrelation matrix of coefficients of integral multiwavelet in multiwavelet domain. The representation of 1/f signal by singular wavelet is only the special case of the representation.
Based on the theory of integral multiwavelet transformation, the representation of 1/f signal (not near-1/f signal) is explored by inverse integral multiwavelet transforma-tion, and the conditions of representing 1/f signal are acquired. The statistical characteris-tics of integral multiwavelets transformation are studied, and it is proved that the self-similar characteristics of 1/f signal can be represented by the autocorrelation matrix of coefficients of integral multiwavelet in multiwavelet domain. The representation of 1/f signal by singular wavelet is only the special case of the representation.
2004, 26(10): 1645-1649.
Abstract:
This paper presents a fast SA(Synthetic Aperture) algorithm based on the high SNR of the subsurface Subsurface Penetrating Radars (SPRs) reflecting signal and the SA algorithm of microwave holographic imaging. With this fast algorithm,the target azimuth is automatically detected and the amount of SA operating data is cut down. The algorithm is simple and easy to be realized. When the image is processed with the fast SA algorithm, the result is almost the same as the image processed with the general SA algorithm, but its processing speed is enhanced greatly.
This paper presents a fast SA(Synthetic Aperture) algorithm based on the high SNR of the subsurface Subsurface Penetrating Radars (SPRs) reflecting signal and the SA algorithm of microwave holographic imaging. With this fast algorithm,the target azimuth is automatically detected and the amount of SA operating data is cut down. The algorithm is simple and easy to be realized. When the image is processed with the fast SA algorithm, the result is almost the same as the image processed with the general SA algorithm, but its processing speed is enhanced greatly.
2004, 26(10): 1650-1655.
Abstract:
A new method of pulse compression, match Fourier pulse compression technol-ogy is proposed in this paper. The method can achieve pulse compression to multi-targets echoes in match Fourier domain, and the peak position of each compressed echo changes linearly with its time delay. The same as conventional method of match filter pulse compres-sion, it can be applied to radar signal processing. The paper first gives the theory of match Fourier pulse compression and the resolution between echo time delays. Then the simulation is carried out. The results verify that the theory is right and the new method is feasible.
A new method of pulse compression, match Fourier pulse compression technol-ogy is proposed in this paper. The method can achieve pulse compression to multi-targets echoes in match Fourier domain, and the peak position of each compressed echo changes linearly with its time delay. The same as conventional method of match filter pulse compres-sion, it can be applied to radar signal processing. The paper first gives the theory of match Fourier pulse compression and the resolution between echo time delays. Then the simulation is carried out. The results verify that the theory is right and the new method is feasible.
2004, 26(10): 1656-1660.
Abstract:
A novel fast phase compensation approach based on two-dimensional minimal image entropy is presented in this paper for Inverse Synthetic Aperture Radar(ISAR) imaging. Compared with the other methods, the proposed approach has better effect of autofocusing, better computation efficiency, global minimal entropy as well as explicit expression applied easily, and these advantages are demonstrated by the analysis and data processing results.
A novel fast phase compensation approach based on two-dimensional minimal image entropy is presented in this paper for Inverse Synthetic Aperture Radar(ISAR) imaging. Compared with the other methods, the proposed approach has better effect of autofocusing, better computation efficiency, global minimal entropy as well as explicit expression applied easily, and these advantages are demonstrated by the analysis and data processing results.
2004, 26(10): 1661-1667.
Abstract:
Based on the phase correlativity between pluses of Synthetic Aperture Radar (SAR), a new observation method is presented. By the method the SARs location information can be obtained from the characteristics of the observed azimuth chirp signals of SAR. Compared with the normal TOA observation, the method that uses a phase measurement instead of time measurement, could avoid a severe demand of time measurement accuracy.
Based on the phase correlativity between pluses of Synthetic Aperture Radar (SAR), a new observation method is presented. By the method the SARs location information can be obtained from the characteristics of the observed azimuth chirp signals of SAR. Compared with the normal TOA observation, the method that uses a phase measurement instead of time measurement, could avoid a severe demand of time measurement accuracy.
2004, 26(10): 1668-1674.
Abstract:
Attack simulation plays a key role in testing Intrusion Detection System(IDS). Prom the viewpoint of attack testing, an attack simulation platform is put forward for testing IDS based on virtual machine technology. First of all, the testing aims and contents of attack simulation are proposed. Then, the design and implementation of the attack simulation platform are presented in detail. Under the platform, that the authors build, three key issues in realization of the platform :the choice of testing datum, the classification of attack technology, and the attack testing zones and their compartmentalization are discussed in detail. Finally, the test results are given.
Attack simulation plays a key role in testing Intrusion Detection System(IDS). Prom the viewpoint of attack testing, an attack simulation platform is put forward for testing IDS based on virtual machine technology. First of all, the testing aims and contents of attack simulation are proposed. Then, the design and implementation of the attack simulation platform are presented in detail. Under the platform, that the authors build, three key issues in realization of the platform :the choice of testing datum, the classification of attack technology, and the attack testing zones and their compartmentalization are discussed in detail. Finally, the test results are given.
2004, 26(10): 1675-1680.
Abstract:
In this paper, author wants to present a new software verification method based on native-compiling technology for embedded system. The method verifies the target system from behavior level, after creating RTOS based software simulator, together with hardware simulator, easily to realize the co-verification for the hardware/software mixed system. At the end of this paper, a co-design example called fifth elliptical filter is put forward to illustrate how to realize the co-verification using the RTOS software simulator.
In this paper, author wants to present a new software verification method based on native-compiling technology for embedded system. The method verifies the target system from behavior level, after creating RTOS based software simulator, together with hardware simulator, easily to realize the co-verification for the hardware/software mixed system. At the end of this paper, a co-design example called fifth elliptical filter is put forward to illustrate how to realize the co-verification using the RTOS software simulator.
