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2007 Vol. 29, No. 6
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2007, 29(6): 1271-1275.
doi: 10.3724/SP.J.1146.2005.01553
Abstract:
With the increasing demand for high data rate and high quality of mobile telecommunication services, and the deeply research on multi-antenna techniques, the cellular concept and network topology for future mobile communication systems are necessarily researched. This paper introduces the generalized distributed cellular architecture-group cell, which is suitable for advanced physical techniques and solves the problem of smaller cells caused by higher frequency carrier. The concept and the structure of the group cell are described and slide handover strategy based on the group cell is introduced as well. The system performance of capacity and coverage with downlink weighted transmission power allocation scheme are focused both in theory and numerical simulation. Compared to traditional cellular structure, the simulation results verify that group cell architecture can improve the system capacity and enlarge the coverage area.
With the increasing demand for high data rate and high quality of mobile telecommunication services, and the deeply research on multi-antenna techniques, the cellular concept and network topology for future mobile communication systems are necessarily researched. This paper introduces the generalized distributed cellular architecture-group cell, which is suitable for advanced physical techniques and solves the problem of smaller cells caused by higher frequency carrier. The concept and the structure of the group cell are described and slide handover strategy based on the group cell is introduced as well. The system performance of capacity and coverage with downlink weighted transmission power allocation scheme are focused both in theory and numerical simulation. Compared to traditional cellular structure, the simulation results verify that group cell architecture can improve the system capacity and enlarge the coverage area.
2007, 29(6): 1276-1280.
doi: 10.3724/SP.J.1146.2005.01390
Abstract:
An efficient Sphere Decoding (SD) algorithm is proposed for uncoded Multi-Input Multi-Output (MIMO) systems with a large number of antennas and higher modulation constellations. This method utilizes a channel-based group detection strategy. The transmitted symbols on each substream are detected by performing sphere decoding within each group and successive interference canceling between groups. Analyses and simulations demonstrate that the proposed algorithm can approach Maximum Likelihood (ML) detection with a relatively low complexity.
An efficient Sphere Decoding (SD) algorithm is proposed for uncoded Multi-Input Multi-Output (MIMO) systems with a large number of antennas and higher modulation constellations. This method utilizes a channel-based group detection strategy. The transmitted symbols on each substream are detected by performing sphere decoding within each group and successive interference canceling between groups. Analyses and simulations demonstrate that the proposed algorithm can approach Maximum Likelihood (ML) detection with a relatively low complexity.
2007, 29(6): 1281-1285.
doi: 10.3724/SP.J.1146.2005.01318
Abstract:
The current IEEE 802.11 PHYs provide multiple transmission rates, but in MAC layer, the rate adaptation algorithm is not specified. This paper studies rate adaptation schemes for high rate IEEE 802.11 WLANs MAC protocol. Firstly, an Enhanced ACKnowledgement (EACK) rate adaptation protocol is presented. In EACK, the MAC header is transmitted at basic rate and the channel state information is carried by ACK frame. EACK reacts to channel variations quickly while has fewer overheads. Then, a constant transmission duration scheme with EACK (CEACK) is proposed for high rate wireless LANs which can overcome the throughput upper limit of legacy IEEE 802.11 DCF MAC and has better temporal fairness performance in hybrid rates networks.
The current IEEE 802.11 PHYs provide multiple transmission rates, but in MAC layer, the rate adaptation algorithm is not specified. This paper studies rate adaptation schemes for high rate IEEE 802.11 WLANs MAC protocol. Firstly, an Enhanced ACKnowledgement (EACK) rate adaptation protocol is presented. In EACK, the MAC header is transmitted at basic rate and the channel state information is carried by ACK frame. EACK reacts to channel variations quickly while has fewer overheads. Then, a constant transmission duration scheme with EACK (CEACK) is proposed for high rate wireless LANs which can overcome the throughput upper limit of legacy IEEE 802.11 DCF MAC and has better temporal fairness performance in hybrid rates networks.
2007, 29(6): 1286-1289.
doi: 10.3724/SP.J.1146.2005.01345
Abstract:
Power allocation is an important issue of resource scheduling in OFDMA system. In this paper, an algorithm of linear water-filling power allocation is proposed through searching for a rapid means for confirming the sub-carriers which need not allocate power. It can finish the process of power water-filling without time after time iterative calculation. The simulation results show that the throughput of the proposed algorithm approaches the algorithm of iterated water-filling power allocation.
Power allocation is an important issue of resource scheduling in OFDMA system. In this paper, an algorithm of linear water-filling power allocation is proposed through searching for a rapid means for confirming the sub-carriers which need not allocate power. It can finish the process of power water-filling without time after time iterative calculation. The simulation results show that the throughput of the proposed algorithm approaches the algorithm of iterated water-filling power allocation.
2007, 29(6): 1290-1294.
doi: 10.3724/SP.J.1146.2005.01395
Abstract:
Based on the situation that the serving area of Gateway Location Register (GLR) is larger than that of Visitor Location Register (VLR) in three-tier database architecture in 3G network, this paper presents a novel call setup mechanism by taking consideration of the locality of the called traffic which means the number of local mobile users calling local users is a large part of the total call number and caching callee current GLR address in caller GLR database. An analytical model is established and the total cost function and total time delay function are presented based on the model. Then the performance of this mechanism is evaluated over the basic call setup mechanism and the VLR cache based call setup mechanism in 2G network. The outcomes show that the new call setup mechanism outperforms the other two mechanisms.
Based on the situation that the serving area of Gateway Location Register (GLR) is larger than that of Visitor Location Register (VLR) in three-tier database architecture in 3G network, this paper presents a novel call setup mechanism by taking consideration of the locality of the called traffic which means the number of local mobile users calling local users is a large part of the total call number and caching callee current GLR address in caller GLR database. An analytical model is established and the total cost function and total time delay function are presented based on the model. Then the performance of this mechanism is evaluated over the basic call setup mechanism and the VLR cache based call setup mechanism in 2G network. The outcomes show that the new call setup mechanism outperforms the other two mechanisms.
2007, 29(6): 1295-1298.
doi: 10.3724/SP.J.1146.2005.01428
Abstract:
In this paper, a distributed resource allocation scheme is developed for OFDMA cellular systems in a downlink transmission. The major impairments considered are co-channel interference and frequency selective fading. The allocation problem includes assignment of sub-carriers, bit loading and power control for multiple users considering their individual QoS as well as the fairness. Exchanging the simple occupation of sub-carriers among cells, the scheme does not result in heave signal load. Simulation results show that the allocation scheme can achieve the tradeoff among different performance objects by adjusting the parameters.
In this paper, a distributed resource allocation scheme is developed for OFDMA cellular systems in a downlink transmission. The major impairments considered are co-channel interference and frequency selective fading. The allocation problem includes assignment of sub-carriers, bit loading and power control for multiple users considering their individual QoS as well as the fairness. Exchanging the simple occupation of sub-carriers among cells, the scheme does not result in heave signal load. Simulation results show that the allocation scheme can achieve the tradeoff among different performance objects by adjusting the parameters.
2007, 29(6): 1299-1303.
doi: 10.3724/SP.J.1146.2005.01402
Abstract:
According to OSI model, the no-cooperation characteristics of nodes and the importance of cooperation mechanism in wireless Ad hoc network are presented in this paper. The key design ideas of three different cooperation mechanisms in the network layer are also analyzed. Based on game theory and network model, the behavior characteristics of nodes are described in details and the utility function to stimulate cooperate is provide at the end of this paper.
According to OSI model, the no-cooperation characteristics of nodes and the importance of cooperation mechanism in wireless Ad hoc network are presented in this paper. The key design ideas of three different cooperation mechanisms in the network layer are also analyzed. Based on game theory and network model, the behavior characteristics of nodes are described in details and the utility function to stimulate cooperate is provide at the end of this paper.
2007, 29(6): 1304-1309.
doi: 10.3724/SP.J.1146.2005.01274
Abstract:
A new synthesis method of network traffic, stable CPC noise, is proposed in this paper. The method can approximate the infinitely divisible cascades model of traffic. It is testified that sequences generated using the method can simulate real network traffic favorably. In queuing analysis the sequence of synthesized traffic is much better than fBm self-similar traffic sequence, and are fit for research of network performance.
A new synthesis method of network traffic, stable CPC noise, is proposed in this paper. The method can approximate the infinitely divisible cascades model of traffic. It is testified that sequences generated using the method can simulate real network traffic favorably. In queuing analysis the sequence of synthesized traffic is much better than fBm self-similar traffic sequence, and are fit for research of network performance.
2007, 29(6): 1310-1313.
doi: 10.3724/SP.J.1146.2005.01411
Abstract:
In this paper, a reformed MC-CDMA scheme is proposed, which choose the symbol period transmitted multiple the chip period. This allows each subcarrier undergoes frequency selective fading channel and avoids the limitation on the chip rate and symbol rates of the former scheme, and furthermore it guarantees the multipath signals can be separated effectively. The Bit Error Rate (BER) expression is derived in a multipath fading channel, which is verified through simulations. Compared with the typical MC-CDMA scheme the BER performance of the proposed system is improved significantly because of the extra path gain.
In this paper, a reformed MC-CDMA scheme is proposed, which choose the symbol period transmitted multiple the chip period. This allows each subcarrier undergoes frequency selective fading channel and avoids the limitation on the chip rate and symbol rates of the former scheme, and furthermore it guarantees the multipath signals can be separated effectively. The Bit Error Rate (BER) expression is derived in a multipath fading channel, which is verified through simulations. Compared with the typical MC-CDMA scheme the BER performance of the proposed system is improved significantly because of the extra path gain.
2007, 29(6): 1314-1318.
doi: 10.3724/SP.J.1146.2005.01559
Abstract:
This paper proposes an improved reverse link common rate control algorithm in CDMA system from practical utilization aspect. In this scheme, packet data service mobile controls its data rate to rise or decrease according to the change of Outer-Loop Power Control (OLPC) set point and Reverse Activity (RA) bit in a probabilistic manner. Analysis of probabilities is also presented in this paper and a sub-optimal and less complex solution is constructed. It is proved with system level simulation results that the improved scheme can enlarge system throughput and enhance resource utilization while maintaining Quality of Service (QoS) compared to existing algorithm only based on reverse active bit.
This paper proposes an improved reverse link common rate control algorithm in CDMA system from practical utilization aspect. In this scheme, packet data service mobile controls its data rate to rise or decrease according to the change of Outer-Loop Power Control (OLPC) set point and Reverse Activity (RA) bit in a probabilistic manner. Analysis of probabilities is also presented in this paper and a sub-optimal and less complex solution is constructed. It is proved with system level simulation results that the improved scheme can enlarge system throughput and enhance resource utilization while maintaining Quality of Service (QoS) compared to existing algorithm only based on reverse active bit.
2007, 29(6): 1319-1323.
doi: 10.3724/SP.J.1146.2005.01295
Abstract:
According to the features of TD-SCDMA system, a new MIMO structure of TD-SCDMA system based on midamble sequences is proposed. Furthermore, by combining Turbo iterative equalization and MIMO technology, MMSE-IC detection and MMSE-IC-Turbo detection are put forward. The two algorithms are measured with generally accepted RAKE-BLAST detection proposed in 3GPP. Simulation results show that MMSE-IC-Turbo detection performs best, and MMSE-IC also has better performance than the traditional algorithm. The capacity of TD-SCDMA system is largely improved by using the MIMO technology.
According to the features of TD-SCDMA system, a new MIMO structure of TD-SCDMA system based on midamble sequences is proposed. Furthermore, by combining Turbo iterative equalization and MIMO technology, MMSE-IC detection and MMSE-IC-Turbo detection are put forward. The two algorithms are measured with generally accepted RAKE-BLAST detection proposed in 3GPP. Simulation results show that MMSE-IC-Turbo detection performs best, and MMSE-IC also has better performance than the traditional algorithm. The capacity of TD-SCDMA system is largely improved by using the MIMO technology.
2007, 29(6): 1324-1327.
doi: 10.3724/SP.J.1146.2005.01473
Abstract:
This paper presents a new HF hopping system, which is called Differential Frequency Hopping (DFH) system. The frequencies transition function and the method of signal detection are the key technologies in this system. Detection and receiving symbol by symbol, detection by sequence and linear-combining receiving are two kinds of methods of signal detection and receiving. The performance of rejecting Partial Band Noise Jamming (PBNJ) by using these two methods is analyzed respectively in theory, and the corresponding simulation results are given, all these prove that the performance of DFH system with signal detection by sequence and linear-combining receiver is much better than conventional frequency hopping system under PBNJ.
This paper presents a new HF hopping system, which is called Differential Frequency Hopping (DFH) system. The frequencies transition function and the method of signal detection are the key technologies in this system. Detection and receiving symbol by symbol, detection by sequence and linear-combining receiving are two kinds of methods of signal detection and receiving. The performance of rejecting Partial Band Noise Jamming (PBNJ) by using these two methods is analyzed respectively in theory, and the corresponding simulation results are given, all these prove that the performance of DFH system with signal detection by sequence and linear-combining receiver is much better than conventional frequency hopping system under PBNJ.
2007, 29(6): 1328-1331.
doi: 10.3724/SP.J.1146.2005.01305
Abstract:
A novel nonlinear adaptive prediction approach based on truncated Laguerre memory structure is proposed to effectively suppress NarrowBand Interference (NBI) in Direct Sequence Spread Spectrum (DSSS). The memory depth can be uncoupled with the filter orders. Simulation results show that the proposed nonlinear adaptive prediction scheme outperforms the other exiting nonlinear adaptive prediction methods for the NBI suppression in DSSS, and the orders of the proposed filter can be largely reduced 3~5 times than that of Vijayan and Poors filters.
A novel nonlinear adaptive prediction approach based on truncated Laguerre memory structure is proposed to effectively suppress NarrowBand Interference (NBI) in Direct Sequence Spread Spectrum (DSSS). The memory depth can be uncoupled with the filter orders. Simulation results show that the proposed nonlinear adaptive prediction scheme outperforms the other exiting nonlinear adaptive prediction methods for the NBI suppression in DSSS, and the orders of the proposed filter can be largely reduced 3~5 times than that of Vijayan and Poors filters.
2007, 29(6): 1332-1337.
doi: 10.3724/SP.J.1146.2006.00429
Abstract:
A high performance SDRAM controller for HDTV video decoder is proposed. Configured with multiple ports and integrated with an arbitration function, the SDRAM controller proposed can be used in place of traditional structures of bus + DMA to share the bandwidth resource of the SDRAM among several function blocks in the HDTV decoder. The SDRAM controller consists of pipelined address path and data path, which take advantage of the pipeline feature of the SDRAM to enable the controller to process access requests from each port continuously, so that the storage volume of on-chip memories is significantly reduced. The simulation results show that up to 70% of the on-chip memories could be reduced compared to the traditional bus + DMA structures, while the performance for HDTV decoding is assured.
A high performance SDRAM controller for HDTV video decoder is proposed. Configured with multiple ports and integrated with an arbitration function, the SDRAM controller proposed can be used in place of traditional structures of bus + DMA to share the bandwidth resource of the SDRAM among several function blocks in the HDTV decoder. The SDRAM controller consists of pipelined address path and data path, which take advantage of the pipeline feature of the SDRAM to enable the controller to process access requests from each port continuously, so that the storage volume of on-chip memories is significantly reduced. The simulation results show that up to 70% of the on-chip memories could be reduced compared to the traditional bus + DMA structures, while the performance for HDTV decoding is assured.
2007, 29(6): 1338-1342.
doi: 10.3724/SP.J.1146.2005.01193
Abstract:
Through analyzing visual differences between cartoon and other videos, 8 groups of typical features including MPEG-7 descriptors are extracted to construct the feature space of cartoon videos. Then, a content-based video classifier is designed by introducing the active relevance feedback technique into Support Vector Machine (SVM) for the cartoon video detection. Experimental results on a great many real video clips illustrate that the constructed feature space can represent the cartoon videos effectively. In addition, compared with the classifier based on SVM and that based on the traditional relevance feedback technique and SVM, the proposed classifier has a higher performance for cartoon video detection.
Through analyzing visual differences between cartoon and other videos, 8 groups of typical features including MPEG-7 descriptors are extracted to construct the feature space of cartoon videos. Then, a content-based video classifier is designed by introducing the active relevance feedback technique into Support Vector Machine (SVM) for the cartoon video detection. Experimental results on a great many real video clips illustrate that the constructed feature space can represent the cartoon videos effectively. In addition, compared with the classifier based on SVM and that based on the traditional relevance feedback technique and SVM, the proposed classifier has a higher performance for cartoon video detection.
2007, 29(6): 1343-1347.
doi: 10.3724/SP.J.1146.2006.00326
Abstract:
This paper analyzes the relationship between the Sampling Rate (SR) and Sampling Loss Rate of Elephant Flows (SLREF) of hardflow. Then two improved algorithms are proposed to reduce the ratio of SLREF to SR(rd ). The relative error and the parameters setting are discussed with various sampling buffer sizes and various measurement periods. Compared to the hardflow, the results show that rd of the two improved algorithms decrease 1.4 and 6.6 respectively when SR is low (e.g. 4.5%). Furthermore, all rd incline to zero when SR is large (e.g. 11.3%).
This paper analyzes the relationship between the Sampling Rate (SR) and Sampling Loss Rate of Elephant Flows (SLREF) of hardflow. Then two improved algorithms are proposed to reduce the ratio of SLREF to SR(rd ). The relative error and the parameters setting are discussed with various sampling buffer sizes and various measurement periods. Compared to the hardflow, the results show that rd of the two improved algorithms decrease 1.4 and 6.6 respectively when SR is low (e.g. 4.5%). Furthermore, all rd incline to zero when SR is large (e.g. 11.3%).
2007, 29(6): 1348-1351.
doi: 10.3724/SP.J.1146.2005.01542
Abstract:
The conception of Trusted Network Connection (TNC) is introduced, and the problem of TNC protocol extend is analyzed. Direct Anonymous Attestation(DAA) protocol is descripted. After this, the paper takes out a new host Indentity based One-time Key Exchange Protocol(I-OKEP), and analyzes its security character. The security analysis can prove that the protocol can ensure the confidentiality and reliability of key-exchange, and the integrity and anonymous of host in trusted computing environments.
The conception of Trusted Network Connection (TNC) is introduced, and the problem of TNC protocol extend is analyzed. Direct Anonymous Attestation(DAA) protocol is descripted. After this, the paper takes out a new host Indentity based One-time Key Exchange Protocol(I-OKEP), and analyzes its security character. The security analysis can prove that the protocol can ensure the confidentiality and reliability of key-exchange, and the integrity and anonymous of host in trusted computing environments.
2007, 29(6): 1352-1355.
doi: 10.3724/SP.J.1146.2005.01422
Abstract:
A new weighted multimodulus blind equalization algorithm is proposed in this paper. The proposed algorithm, which combines the benefits of the MultiModulus Algorithm (MMA) and the Decision-Directed Algorithm (DDA), utilizes exponential weighted symbols of the slicers output to adjust the modulus in the cost function. During the equalizer tab update process, the weight term varies according to the decided symbols as well as the MSE estimation for more accurate adjustment. Analysis and simulation results demonstrate that compared with other blind equalization algorithms including MMA, the proposed algorithm provides superior performance by increasing the convergence rate and decreasing the steady-state mean square error, which is more efficient for high-order QAM signals.
A new weighted multimodulus blind equalization algorithm is proposed in this paper. The proposed algorithm, which combines the benefits of the MultiModulus Algorithm (MMA) and the Decision-Directed Algorithm (DDA), utilizes exponential weighted symbols of the slicers output to adjust the modulus in the cost function. During the equalizer tab update process, the weight term varies according to the decided symbols as well as the MSE estimation for more accurate adjustment. Analysis and simulation results demonstrate that compared with other blind equalization algorithms including MMA, the proposed algorithm provides superior performance by increasing the convergence rate and decreasing the steady-state mean square error, which is more efficient for high-order QAM signals.
2007, 29(6): 1356-1360.
doi: 10.3724/SP.J.1146.2005.01593
Abstract:
In MIMO-OFDM systems, data streams of multiple users can be simultaneously recovered up to a phase ambiguity when a VCMA criterion combined with a user decorrelation criterion is considered. Since a low complexity LMS algorithm is used in the iteration, the convergence speed and the steady state MSE performance become a contradiction. In this paper, a variable step size iteration method is proposed which has good performance in both convergence speed and steady state MSE. Moreover, the impact of channel noise on the tap refreshing process of the transverse filters is analyzed, and a simple method to remove the effect of noise is induced. As a result the convergence performance of the blind equalizer is further improved.
In MIMO-OFDM systems, data streams of multiple users can be simultaneously recovered up to a phase ambiguity when a VCMA criterion combined with a user decorrelation criterion is considered. Since a low complexity LMS algorithm is used in the iteration, the convergence speed and the steady state MSE performance become a contradiction. In this paper, a variable step size iteration method is proposed which has good performance in both convergence speed and steady state MSE. Moreover, the impact of channel noise on the tap refreshing process of the transverse filters is analyzed, and a simple method to remove the effect of noise is induced. As a result the convergence performance of the blind equalizer is further improved.
2007, 29(6): 1361-1364.
doi: 10.3724/SP.J.1146.2005.01315
Abstract:
Through the analysis of fractional Fourier transform of the Linear Frequency Modulation (LFM) signal, a LFM interference suppression algorithm using Time-Frequency Windowed-Short Time Fourier Transform (TFW-STFT) is proposed. Because the energy of LFM interference can be concentrated into a very narrow band in frequency domain by the time-frequency window, the impact made on the signal by TFW-STFT is lighter than the STFT. Simulation results show that the SNR loss and the BER performance of the proposed algorithm are evidently better than the STFT algorithm.
Through the analysis of fractional Fourier transform of the Linear Frequency Modulation (LFM) signal, a LFM interference suppression algorithm using Time-Frequency Windowed-Short Time Fourier Transform (TFW-STFT) is proposed. Because the energy of LFM interference can be concentrated into a very narrow band in frequency domain by the time-frequency window, the impact made on the signal by TFW-STFT is lighter than the STFT. Simulation results show that the SNR loss and the BER performance of the proposed algorithm are evidently better than the STFT algorithm.
2007, 29(6): 1365-1368.
doi: 10.3724/SP.J.1146.2005.01328
Abstract:
Finite plane LDPC codes are important structured LDPC codes, which have excellent performance under iterative decoding algorithm. It is a key problem that to evaluate the performance of LDPC codes under iterative decoding. Recently, the stopping sets and stopping distance of Tanner graph are of interests in performance evaluation. In this paper, the smallest sets of finite plane LDPC codes are studied. It shows that for finite plane LDPC codes, a smallest stopping set is the support of a codeword. These results give positive consequences for the good performance of finite plane LDPC codes under iterative decoding.
Finite plane LDPC codes are important structured LDPC codes, which have excellent performance under iterative decoding algorithm. It is a key problem that to evaluate the performance of LDPC codes under iterative decoding. Recently, the stopping sets and stopping distance of Tanner graph are of interests in performance evaluation. In this paper, the smallest sets of finite plane LDPC codes are studied. It shows that for finite plane LDPC codes, a smallest stopping set is the support of a codeword. These results give positive consequences for the good performance of finite plane LDPC codes under iterative decoding.
2007, 29(6): 1369-1372.
doi: 10.3724/SP.J.1146.2005.01408
Abstract:
This paper introduces a new particle filter for nonlinear and non-Gaussian systems.The divided difference filter based on numerical integration is used for generating the importance density functions.As it integrates the new observations into system state transition density,which approximates to the state posterior density , the proposed particle filter has the better performance than the conventional one. Finally, the validity of this method is well verified by the computer simulations.
This paper introduces a new particle filter for nonlinear and non-Gaussian systems.The divided difference filter based on numerical integration is used for generating the importance density functions.As it integrates the new observations into system state transition density,which approximates to the state posterior density , the proposed particle filter has the better performance than the conventional one. Finally, the validity of this method is well verified by the computer simulations.
2007, 29(6): 1373-1376.
doi: 10.3724/SP.J.1146.2005.01424
Abstract:
A 2-D DOA estimation algorithm for coherent signal is presented based on plane array in this paper, firstly the plane array is divided into three sub-arrays with the nature of rotational invariance and three kinds of data matrix is formed for each of the three sub-arrays, based on which two kinds of modified data matrix is formed for raising the array utilization ratio. Then it imitates the DOA matrix method, obtains the generalized DOA matrix. Theoretical analysis shows that signal direction vectors and signal direction elements can be obtained via the eigen-decomposition of the generalized DOA matrix. Thus the coherent signal 2-D DOA can be estimated. This method avoids the parameter pairing and the spectrum peak searching, reduces the computation quantity. The computer simulation confirms the validity and the accuracy of this algorithm.
A 2-D DOA estimation algorithm for coherent signal is presented based on plane array in this paper, firstly the plane array is divided into three sub-arrays with the nature of rotational invariance and three kinds of data matrix is formed for each of the three sub-arrays, based on which two kinds of modified data matrix is formed for raising the array utilization ratio. Then it imitates the DOA matrix method, obtains the generalized DOA matrix. Theoretical analysis shows that signal direction vectors and signal direction elements can be obtained via the eigen-decomposition of the generalized DOA matrix. Thus the coherent signal 2-D DOA can be estimated. This method avoids the parameter pairing and the spectrum peak searching, reduces the computation quantity. The computer simulation confirms the validity and the accuracy of this algorithm.
2007, 29(6): 1377-1379.
doi: 10.3724/SP.J.1146.2005.01300
Abstract:
In this paper, a complex Linear FM (LFM) signal model is given, and a transform called Cyclic- Correlation Transform (CCT) is introduced. Then, a new method combining CCT with clean technique for multipath LFM signal detection and parameter estimation is presented. Multipath LFM signal parameters, time delays and attenuation factors are estimated precisely with this method, and the correlated cross-item can be avoided effectively. The relevant conclusions are got and verified by the computer simulation.
In this paper, a complex Linear FM (LFM) signal model is given, and a transform called Cyclic- Correlation Transform (CCT) is introduced. Then, a new method combining CCT with clean technique for multipath LFM signal detection and parameter estimation is presented. Multipath LFM signal parameters, time delays and attenuation factors are estimated precisely with this method, and the correlated cross-item can be avoided effectively. The relevant conclusions are got and verified by the computer simulation.
2007, 29(6): 1380-1383.
doi: 10.3724/SP.J.1146.2005.01333
Abstract:
In order to make full use of the cell information and decrease CFAR loss, A new CFAR detector (MOSUM-CFAR) based on unbiased minimum-variance estimation and ordered statistics estimation is presented in this paper . It takes the sum of UMVE of leading window and OS estimation of lagging window as a global noise power estimation. Under swerling II assumption, the analytic expressions of Pfa and Pd in homogeneous background are derived, and the analytic expression of Pd in multiple target situations is also derived. In contrast to other detectors, the MOSUM-CFAR detector has fairly well detection performance in both homogeneous background and multiple target situations.
In order to make full use of the cell information and decrease CFAR loss, A new CFAR detector (MOSUM-CFAR) based on unbiased minimum-variance estimation and ordered statistics estimation is presented in this paper . It takes the sum of UMVE of leading window and OS estimation of lagging window as a global noise power estimation. Under swerling II assumption, the analytic expressions of Pfa and Pd in homogeneous background are derived, and the analytic expression of Pd in multiple target situations is also derived. In contrast to other detectors, the MOSUM-CFAR detector has fairly well detection performance in both homogeneous background and multiple target situations.
2007, 29(6): 1384-1388.
doi: 10.3724/SP.J.1146.2005.01316
Abstract:
A novel model compensation method is proposed, which integrates the Vector Taylor Series (VTS) approach with a robust feature extraction technique called SNR-dependent Non-uniform Spectral Compression (SNSC). The SNSC method is a spectral operation of magnitude transformation which resembles the human intensity-to-loudness conversion process and de-emphasizes noisy bands. Based on this mismatch function, which models the effect of the noise onto the clean speech in the Log-spectral domain together with the SNSC, a new model compensation procedure is derived. By adopting this novel model compensation approach, significant improvement over the PMC and VTS method can be found in different additive noisy environments at the expense of slight increase in computational complexity.
A novel model compensation method is proposed, which integrates the Vector Taylor Series (VTS) approach with a robust feature extraction technique called SNR-dependent Non-uniform Spectral Compression (SNSC). The SNSC method is a spectral operation of magnitude transformation which resembles the human intensity-to-loudness conversion process and de-emphasizes noisy bands. Based on this mismatch function, which models the effect of the noise onto the clean speech in the Log-spectral domain together with the SNSC, a new model compensation procedure is derived. By adopting this novel model compensation approach, significant improvement over the PMC and VTS method can be found in different additive noisy environments at the expense of slight increase in computational complexity.
2007, 29(6): 1389-1393.
doi: 10.3724/SP.J.1146.2005.01320
Abstract:
In this paper, the multiwavelet sampling theorem from Walters wavelet sampling theorem by reproducing kernel is generalized. The reconstruction function can be expressed by multiwavelet using Zak transform. Then the general case of the irregular sampling is considered and the irregular sampling theorem for multiwavelet subspaces is established. Finally, the corresponding examples are given.
In this paper, the multiwavelet sampling theorem from Walters wavelet sampling theorem by reproducing kernel is generalized. The reconstruction function can be expressed by multiwavelet using Zak transform. Then the general case of the irregular sampling is considered and the irregular sampling theorem for multiwavelet subspaces is established. Finally, the corresponding examples are given.
2007, 29(6): 1394-1398.
doi: 10.3724/SP.J.1146.2005.01326
Abstract:
One of the most important problems in Empirical Mode Decomposition (EMD) applications is mitigation of the end effect. Except Huangs patented approach several methods have been proposed. However, a final solution for this problem is yet to be found. In this paper five common end effect mitigation methods of EMD have been investigated, including linear extending method, polynomial fitting extending method, mirror extrema extending method, RBF neural network prediction method and AR prediction method. With a quasi-periodical signal and a stochastic signal as the test bed a quantitative test method was proposed for elimination of the mode confusion effect of EMD. The five end effect mitigation methods were quantitatively evaluated and the comparison shows that mirror extrema extending method is the best option among the five methods.
One of the most important problems in Empirical Mode Decomposition (EMD) applications is mitigation of the end effect. Except Huangs patented approach several methods have been proposed. However, a final solution for this problem is yet to be found. In this paper five common end effect mitigation methods of EMD have been investigated, including linear extending method, polynomial fitting extending method, mirror extrema extending method, RBF neural network prediction method and AR prediction method. With a quasi-periodical signal and a stochastic signal as the test bed a quantitative test method was proposed for elimination of the mode confusion effect of EMD. The five end effect mitigation methods were quantitatively evaluated and the comparison shows that mirror extrema extending method is the best option among the five methods.
2007, 29(6): 1399-1402.
doi: 10.3724/SP.J.1146.2005.01344
Abstract:
A novel method of analogous Fourier transform is proposed for reconstruction of multi-component signals, and the behaviors of this method are investigated. This method transforms multi-component signals, which are aliasing in frequency domain but not overlapping in time-frequency spectrogram, into analogous Fourier frequency domain where no aliasing appears. Compared with the method of optimal filtering in fractional Fourier domain, this method has better applicability. Simulation results show that this method can produce reliable reconstruction signals. This method has a variety of applications in the aspect of signal detection and analysis.
A novel method of analogous Fourier transform is proposed for reconstruction of multi-component signals, and the behaviors of this method are investigated. This method transforms multi-component signals, which are aliasing in frequency domain but not overlapping in time-frequency spectrogram, into analogous Fourier frequency domain where no aliasing appears. Compared with the method of optimal filtering in fractional Fourier domain, this method has better applicability. Simulation results show that this method can produce reliable reconstruction signals. This method has a variety of applications in the aspect of signal detection and analysis.
Optimization Design of 17/11 Biorthogonal Wavelet and Its Performance Analysis for Image Compression
2007, 29(6): 1403-1407.
doi: 10.3724/SP.J.1146.2005.01358
Abstract:
Many wavelet filter banks suitable for image coding, e.g. CDF-9/7, Winger-17/11 (W-17/11), Villasenor-6/10 and 10/18 (V-6/10 and V-10/18), have irrational coefficients, and thus require infinite computational precision to implement the corresponding Discrete Wavelet Transforms (DWT). Here a simple technique for parametrization construction of 17/11 biorthogonal wavelet family is presented: first, the associated synthesis filter is formulated as one trigonometric polynomial represented by two free parameters; then the perfect reconstruction condition of the filter bank is reduced to one system of linear equations; finally the analysis filter is obtained by solving this system of linear equations. Thus, the exact free parameter expressions for the 17/11 biorthogonal wavelet filter banks are derived. By adjusting the free parameters, one can easily construct any linear phase 17/11 filters (a pair) with desired features. As a case study, a previously unpublished 17/11 biorthogonal wavelet filter bank with rational coefficients is constructed, which has optimum coding gain. Extensive simulations show that the new filter bank has the compression performance comparable to that of W-17/11 and V-10/18 for image transform coding, while surpasses the CDF-9/7 and V-6/10 far away.
Many wavelet filter banks suitable for image coding, e.g. CDF-9/7, Winger-17/11 (W-17/11), Villasenor-6/10 and 10/18 (V-6/10 and V-10/18), have irrational coefficients, and thus require infinite computational precision to implement the corresponding Discrete Wavelet Transforms (DWT). Here a simple technique for parametrization construction of 17/11 biorthogonal wavelet family is presented: first, the associated synthesis filter is formulated as one trigonometric polynomial represented by two free parameters; then the perfect reconstruction condition of the filter bank is reduced to one system of linear equations; finally the analysis filter is obtained by solving this system of linear equations. Thus, the exact free parameter expressions for the 17/11 biorthogonal wavelet filter banks are derived. By adjusting the free parameters, one can easily construct any linear phase 17/11 filters (a pair) with desired features. As a case study, a previously unpublished 17/11 biorthogonal wavelet filter bank with rational coefficients is constructed, which has optimum coding gain. Extensive simulations show that the new filter bank has the compression performance comparable to that of W-17/11 and V-10/18 for image transform coding, while surpasses the CDF-9/7 and V-6/10 far away.
2007, 29(6): 1408-1411.
doi: 10.3724/SP.J.1146.2005.01388
Abstract:
In this paper, a new method is proposed for jamming the Linear Frequency Modulation (LFM) radar, which is based on the feature of the LFM signals processing and is named convolution jamming. The jammer receives the radar signal and convolves it with the expected video frequency signal. Then the convolution result is retransmitted. It can produce false targets deceptive jamming or noise cover jamming according to the video frequency signal. Theoretical analysis and computer simulation justify the validity and efficiency of the new jamming technique.
In this paper, a new method is proposed for jamming the Linear Frequency Modulation (LFM) radar, which is based on the feature of the LFM signals processing and is named convolution jamming. The jammer receives the radar signal and convolves it with the expected video frequency signal. Then the convolution result is retransmitted. It can produce false targets deceptive jamming or noise cover jamming according to the video frequency signal. Theoretical analysis and computer simulation justify the validity and efficiency of the new jamming technique.
2007, 29(6): 1412-1415.
doi: 10.3724/SP.J.1146.2005.01349
Abstract:
In this paper, a deception jamming detection scheme derived from moving target detection is proposed, which is based on dual-aperture antenna along-track interferometric SAR. Another new scheme of deception jamming detection is also investigated on the basis of dual-aperture antenna cross-track interferometric cancellation. Both schemes are discussed respectively on its spatial cancellation algorithm and applicability in detail, and demonstrated effectively with point target simulation in detecting deception jamming.
In this paper, a deception jamming detection scheme derived from moving target detection is proposed, which is based on dual-aperture antenna along-track interferometric SAR. Another new scheme of deception jamming detection is also investigated on the basis of dual-aperture antenna cross-track interferometric cancellation. Both schemes are discussed respectively on its spatial cancellation algorithm and applicability in detail, and demonstrated effectively with point target simulation in detecting deception jamming.
2007, 29(6): 1416-1420.
doi: 10.3724/SP.J.1146.2005.01381
Abstract:
Long duration integration of the interesting signal energy is a key to develop an effective detector under severe noise background in many applications. With the time-frequency concentration characteristic of the interesting signal, a new energy integration detect method is proposed in this paper based on the morphological filtering in the time-frequency plane. Firstly, the optimal kernel of the Cohens Time-Frequency Distribution (TFD) is designed and the TFD of the observation is calculated. Thereafter, the support region of strong energy is estimated by thresholding the TFD and morphological filtering the obtained binary image. Finally, the energy on the estimated region is integrated to judge whether a signal is present or not. Simulation results show that the proposed method is effective in low ratios of signal to noise case.
Long duration integration of the interesting signal energy is a key to develop an effective detector under severe noise background in many applications. With the time-frequency concentration characteristic of the interesting signal, a new energy integration detect method is proposed in this paper based on the morphological filtering in the time-frequency plane. Firstly, the optimal kernel of the Cohens Time-Frequency Distribution (TFD) is designed and the TFD of the observation is calculated. Thereafter, the support region of strong energy is estimated by thresholding the TFD and morphological filtering the obtained binary image. Finally, the energy on the estimated region is integrated to judge whether a signal is present or not. Simulation results show that the proposed method is effective in low ratios of signal to noise case.
2007, 29(6): 1421-1424.
doi: 10.3724/SP.J.1146.2005.01339
Abstract:
Based on the proposed motion error model and detailed influence analysis, with respect to different squint angle and beam width, novel motion compensation methods are presented in this paper for slightly squinted-looking SAR and highly squinted-looking SAR, respectively. It is shown that the application scope of the proposed methods is wider than the existing ones. Lastly, both simulation and results of real data are provided to demonstrate the effectiveness of the proposed methods.
Based on the proposed motion error model and detailed influence analysis, with respect to different squint angle and beam width, novel motion compensation methods are presented in this paper for slightly squinted-looking SAR and highly squinted-looking SAR, respectively. It is shown that the application scope of the proposed methods is wider than the existing ones. Lastly, both simulation and results of real data are provided to demonstrate the effectiveness of the proposed methods.
2007, 29(6): 1425-1428.
doi: 10.3724/SP.J.1146.2005.01454
Abstract:
Chirp Scaling Algorithm (CSA) is integrated with Contrast Optimization Autofocus Algorithm (COAA) via properly modifying azimuth processing of CS to incorporate COAA in it, resulting in improving airborne SAR image quality. RCMC is precisely corrected by means of CSA without interpolation, on the other hand, precise estimation and correction for the second phase error in SAR raw data is accomplished. To improve the phase error estimation precision and speed, modified iteration step is used, resulting in more effective application of COAA. In this paper, the SAR processing flow diagram of the two integrated algorithms is given. Finally, the effective experimental results are shown with real stripmap broadside SAR data.
Chirp Scaling Algorithm (CSA) is integrated with Contrast Optimization Autofocus Algorithm (COAA) via properly modifying azimuth processing of CS to incorporate COAA in it, resulting in improving airborne SAR image quality. RCMC is precisely corrected by means of CSA without interpolation, on the other hand, precise estimation and correction for the second phase error in SAR raw data is accomplished. To improve the phase error estimation precision and speed, modified iteration step is used, resulting in more effective application of COAA. In this paper, the SAR processing flow diagram of the two integrated algorithms is given. Finally, the effective experimental results are shown with real stripmap broadside SAR data.
2007, 29(6): 1429-1432.
doi: 10.3724/SP.J.1146.2006.00615
Abstract:
In this paper the Multi-Stage Wiener Filter (MSWF) is presented for the DOA estimation of ocean currents. For echoes scattered from ocean waves with the same velocity of flow and in the same range bin are partially correlated, first the spatial smoothing technique is applied to the measured data to remove the correlation of signal, then the signal subspace and noise subspace can be obtained by the recursive algorithm instead of the estimation and eigen-decomposition of covariance matrix, therefore the computation complexity can be reduced remarkably, which is necessary for the real time system. Finally by analyzing the measured data, it is shown that this method can detect the currents efficiently and effectively.
In this paper the Multi-Stage Wiener Filter (MSWF) is presented for the DOA estimation of ocean currents. For echoes scattered from ocean waves with the same velocity of flow and in the same range bin are partially correlated, first the spatial smoothing technique is applied to the measured data to remove the correlation of signal, then the signal subspace and noise subspace can be obtained by the recursive algorithm instead of the estimation and eigen-decomposition of covariance matrix, therefore the computation complexity can be reduced remarkably, which is necessary for the real time system. Finally by analyzing the measured data, it is shown that this method can detect the currents efficiently and effectively.
2007, 29(6): 1433-1436.
doi: 10.3724/SP.J.1146.2005.01525
Abstract:
Along-Track Interferometric (ATI) SAR can be used to measure the radial velocity of ground moving targets. By using distributed satellites system the metrical accuracy will be improved and the measurable radial range will be increased. The key point of guaranteeing the distributed satellites system performance is to design the formation of the satellites appropriately. A velocity metrical accuracy model is developed to estimate distributed satellites SAR system performance. This model can be used to optimize the satellite formation of distributed satellites system which moves on flying around orbit. Finally, it is validated by simulation using randomized search algorithm, and the simulation results demonstrate the efficiency of the method.
Along-Track Interferometric (ATI) SAR can be used to measure the radial velocity of ground moving targets. By using distributed satellites system the metrical accuracy will be improved and the measurable radial range will be increased. The key point of guaranteeing the distributed satellites system performance is to design the formation of the satellites appropriately. A velocity metrical accuracy model is developed to estimate distributed satellites SAR system performance. This model can be used to optimize the satellite formation of distributed satellites system which moves on flying around orbit. Finally, it is validated by simulation using randomized search algorithm, and the simulation results demonstrate the efficiency of the method.
2007, 29(6): 1437-1440.
doi: 10.3724/SP.J.1146.2005.01527
Abstract:
An algorithm of HF ground wave radar array calibration for amplitude and phase errors based on sea-echo is proposed in this paper. According to the relation between the adjacent antenna sea-echo responses for the same ocean cell, the equations of amplitude and phase errors are developed and solved. The bias of calibration results is analyzed by numerical simulation, and its application in HF ground wave radar OSMAR2000 shows this algorithm effective and credible.
An algorithm of HF ground wave radar array calibration for amplitude and phase errors based on sea-echo is proposed in this paper. According to the relation between the adjacent antenna sea-echo responses for the same ocean cell, the equations of amplitude and phase errors are developed and solved. The bias of calibration results is analyzed by numerical simulation, and its application in HF ground wave radar OSMAR2000 shows this algorithm effective and credible.
2007, 29(6): 1441-1444.
doi: 10.3724/SP.J.1146.2005.01440
Abstract:
In this paper, the satellite SAR imagery is regarded as an image which is acquired from the frame projection sensor approximately based on photogrametry theory. The satellite SAR collinearity equation is revised and a new location model is proposed. As an example, the RadarSat Imagery is tested. Experiment result demonstrates the new model formulation is simple and the resolution is stable without any orbit ephemeris and imaging parameters, and also location accuracy reaches pixels.
In this paper, the satellite SAR imagery is regarded as an image which is acquired from the frame projection sensor approximately based on photogrametry theory. The satellite SAR collinearity equation is revised and a new location model is proposed. As an example, the RadarSat Imagery is tested. Experiment result demonstrates the new model formulation is simple and the resolution is stable without any orbit ephemeris and imaging parameters, and also location accuracy reaches pixels.
2007, 29(6): 1445-1449.
doi: 10.3724/SP.J.1146.2005.01273
Abstract:
In this paper, a refined Secondary Range Compression (SRC) imaging algorithm for large squint air-borne Synthetic Aperture Radar (SAR) is presented. Based on the squint range mode, refined SRC algorithm for squint mode SAR is deduced directly. By compensating the cubic phase term of range frequency, the problem of range compressing unsymmetrical sidelobe is improved effectively, By compensating the parallel phase term introduced by forward looking beam, the shift of image location in azimuth is solved. Implemented steps and algorithm flow are given, imaging effects are compared in different squint angle as well. The simulation demonstrates that imaging quality is improved obviously and this algorithm is suitable for large squint air-borne SAR imaging.
In this paper, a refined Secondary Range Compression (SRC) imaging algorithm for large squint air-borne Synthetic Aperture Radar (SAR) is presented. Based on the squint range mode, refined SRC algorithm for squint mode SAR is deduced directly. By compensating the cubic phase term of range frequency, the problem of range compressing unsymmetrical sidelobe is improved effectively, By compensating the parallel phase term introduced by forward looking beam, the shift of image location in azimuth is solved. Implemented steps and algorithm flow are given, imaging effects are compared in different squint angle as well. The simulation demonstrates that imaging quality is improved obviously and this algorithm is suitable for large squint air-borne SAR imaging.
2007, 29(6): 1450-1454.
doi: 10.3724/SP.J.1146.2005.01544
Abstract:
Scattering center target model is widely used to describe the target electromagnetic scattering properties in optical region.It achieves good recognition performance in High Resolution Rang Profiles (HRRPs) based Radar Automatic Target Recognition (RATR). Due to the characteristics of scattering center, sometimes HRRPs may appear abnormity, which results in error classification. In order to solve the above problems, this paper mainly discusses the sensitivities of airplane targets with the variation of course, pitch and roll angle, the property of the HRRPs near the airplane targets broadside, and coherent apex phenomena in test data. Corresponding schemes are proposed to improve the recognition performance. Experimental results based on the simulated HRRP data show the proposed schemes can improve the recognition performance effectively.
Scattering center target model is widely used to describe the target electromagnetic scattering properties in optical region.It achieves good recognition performance in High Resolution Rang Profiles (HRRPs) based Radar Automatic Target Recognition (RATR). Due to the characteristics of scattering center, sometimes HRRPs may appear abnormity, which results in error classification. In order to solve the above problems, this paper mainly discusses the sensitivities of airplane targets with the variation of course, pitch and roll angle, the property of the HRRPs near the airplane targets broadside, and coherent apex phenomena in test data. Corresponding schemes are proposed to improve the recognition performance. Experimental results based on the simulated HRRP data show the proposed schemes can improve the recognition performance effectively.
2007, 29(6): 1455-1459.
doi: 10.3724/SP.J.1146.2005.01456
Abstract:
In order to demonstrate the effectiveness of GTD model, usually used to model the target scattering behaviors in optical frequency band, for target resonance band, a new method for the GTD model parameters extraction based on matching pursuits is proposed in this paper. Then, the proposed method and Lis least-square-fitting scheme are used to analyze the resonance scattering data of a aluminum sphere and the measured ultra-wide band scattering data of a finite-length cylinder through the GTD model, Altes model and extended Altes model. Furthermore, after contrasting the scattering behavior parameters and fitting results, some important conclusions are obtained.
In order to demonstrate the effectiveness of GTD model, usually used to model the target scattering behaviors in optical frequency band, for target resonance band, a new method for the GTD model parameters extraction based on matching pursuits is proposed in this paper. Then, the proposed method and Lis least-square-fitting scheme are used to analyze the resonance scattering data of a aluminum sphere and the measured ultra-wide band scattering data of a finite-length cylinder through the GTD model, Altes model and extended Altes model. Furthermore, after contrasting the scattering behavior parameters and fitting results, some important conclusions are obtained.
2007, 29(6): 1460-1463.
doi: 10.3724/SP.J.1146.2005.01563
Abstract:
Applying wavelet decomposition to build high-scale statistical model for capturing statistical difference between cover images and stego-images. However, not all wavelet statistics are able to reflect well statistical change due to hidden message embedded. By exploring analysis of variance, the statistics that are more sensitive to hidden message are chosen as features of images. Kernel-based support vector machine is chosen as classifier to implement blind steganalysis of images. Experiment results show that our method can reach a high testing rate to hidden message of images.
Applying wavelet decomposition to build high-scale statistical model for capturing statistical difference between cover images and stego-images. However, not all wavelet statistics are able to reflect well statistical change due to hidden message embedded. By exploring analysis of variance, the statistics that are more sensitive to hidden message are chosen as features of images. Kernel-based support vector machine is chosen as classifier to implement blind steganalysis of images. Experiment results show that our method can reach a high testing rate to hidden message of images.
2007, 29(6): 1464-1470.
doi: 10.3724/SP.J.1146.2005.01682
Abstract:
Using data fusion of multi-spectral and microwave radar images, a semiautomatic method is developed based on the level set method for application to urban road extraction. The fast marching method of level set makes data fusion. Radar remote sensing image can make up road breaks due to shadowing of high building or tree canopy in multi-spectral image, while multi-spectral image can be of helpful to decrease speckels and identify linear road from flat water surface. As example, the data fusion and road extraction from the ERS-2 SAR image and Landsat ETM+, as well as RASARSAT-1 SAR image and Landsat ETM+, in Shanghai area are applied.
Using data fusion of multi-spectral and microwave radar images, a semiautomatic method is developed based on the level set method for application to urban road extraction. The fast marching method of level set makes data fusion. Radar remote sensing image can make up road breaks due to shadowing of high building or tree canopy in multi-spectral image, while multi-spectral image can be of helpful to decrease speckels and identify linear road from flat water surface. As example, the data fusion and road extraction from the ERS-2 SAR image and Landsat ETM+, as well as RASARSAT-1 SAR image and Landsat ETM+, in Shanghai area are applied.
2007, 29(6): 1471-1475.
doi: 10.3724/SP.J.1146.2005.01355
Abstract:
Since the security of many cryptosystems relies on the apparent intractability of the computational problems, the underdetermined problem of Blind Source Separation (BSS) is used to encrypt multiple images with high security. However, due to the BSS ambiguity, the order of BSS decrypted images may different from that of the original images and the value of pixel in some decrypted images may be reversed, which can result in decryption errors when encrypting multiple sequential images. To solve this problem, digital watermarking technique is utilized to embed some order information into each original image before encryption. After decryption, these order information is extracted from the decrypted images and then used to eliminate the decryption errors. Computer simulation results show that the proposed method not only can recover the original order of the decrypted images, but also can detect if the decrypted images are reversed.
Since the security of many cryptosystems relies on the apparent intractability of the computational problems, the underdetermined problem of Blind Source Separation (BSS) is used to encrypt multiple images with high security. However, due to the BSS ambiguity, the order of BSS decrypted images may different from that of the original images and the value of pixel in some decrypted images may be reversed, which can result in decryption errors when encrypting multiple sequential images. To solve this problem, digital watermarking technique is utilized to embed some order information into each original image before encryption. After decryption, these order information is extracted from the decrypted images and then used to eliminate the decryption errors. Computer simulation results show that the proposed method not only can recover the original order of the decrypted images, but also can detect if the decrypted images are reversed.
2007, 29(6): 1476-1479.
doi: 10.3724/SP.J.1146.2005.01414
Abstract:
Based on the ergodicity of the shifters (except for all zero-states) in m-sequence generator, in this paper a new m-sequence transform method is first proposed to apply to image position permutation. Combining this method with chaotic map, a novel image encryption approach is presented, and some simulating results are shown in this paper. Comparing with the existing encryption methods, the approach is not only of the characteristics of chaotic map with initial value sensitivity, parameter sensitivity and random sensitivity, but also of more larger secret key space. Thus the approach is more security than other encryption methods.
Based on the ergodicity of the shifters (except for all zero-states) in m-sequence generator, in this paper a new m-sequence transform method is first proposed to apply to image position permutation. Combining this method with chaotic map, a novel image encryption approach is presented, and some simulating results are shown in this paper. Comparing with the existing encryption methods, the approach is not only of the characteristics of chaotic map with initial value sensitivity, parameter sensitivity and random sensitivity, but also of more larger secret key space. Thus the approach is more security than other encryption methods.
2007, 29(6): 1480-1482.
doi: 10.3724/SP.J.1146.2005.01561
Abstract:
Terrain surface is not always so perfect that it keeps invariable self-similar characteristic in whole scale space. To describe the degree of the self-similarity, the self-similarity curve is divided into several linear parts and then a new parameter called Self-Similarity Degree (SSD) is presented in the similitude of information entropy. Furthermore, the simulation in which distance measurement and fuzzy c mean clustering are adopted and it shows that the new parameter is the effective feature for terrain recognition. As the presented feature provides more information than traditional single Hurst feature, the precision of terrain classing is improved.
Terrain surface is not always so perfect that it keeps invariable self-similar characteristic in whole scale space. To describe the degree of the self-similarity, the self-similarity curve is divided into several linear parts and then a new parameter called Self-Similarity Degree (SSD) is presented in the similitude of information entropy. Furthermore, the simulation in which distance measurement and fuzzy c mean clustering are adopted and it shows that the new parameter is the effective feature for terrain recognition. As the presented feature provides more information than traditional single Hurst feature, the precision of terrain classing is improved.
2007, 29(6): 1483-1486.
doi: 10.3724/SP.J.1146.2005.01416
Abstract:
In this paper a new method to determine the bearings and ranges of the three highlight sections of a ship is given. This method is based on a non-typical vector sound intensity array with seven sensors. The seven sensors can all be fixing in some underwater detection platform and the distances between them are adjustable. So the array is more convenient for engineering implementation than the traditional array proposed by Liu Xun(2002), et al.. The bearings of the low frequency noise radiated by the midship and the section between the midship and stern is determined by sound intensity vector. And the bearing of the stern which radiates high frequency noise is determined by time delay estimation. The two methods can be carried out based on the same array. The computer simulation for the ships real measured data proved that this method can find the bearings of the three sections of the ship in high precision. And the size of the ship can be estimated if the depth of the platform is already known.
In this paper a new method to determine the bearings and ranges of the three highlight sections of a ship is given. This method is based on a non-typical vector sound intensity array with seven sensors. The seven sensors can all be fixing in some underwater detection platform and the distances between them are adjustable. So the array is more convenient for engineering implementation than the traditional array proposed by Liu Xun(2002), et al.. The bearings of the low frequency noise radiated by the midship and the section between the midship and stern is determined by sound intensity vector. And the bearing of the stern which radiates high frequency noise is determined by time delay estimation. The two methods can be carried out based on the same array. The computer simulation for the ships real measured data proved that this method can find the bearings of the three sections of the ship in high precision. And the size of the ship can be estimated if the depth of the platform is already known.
2007, 29(6): 1487-1491.
doi: 10.3724/SP.J.1146.2005.01392
Abstract:
It is a difficult problem how to detect such accident of a system. This paper presents a new algorithm, an anomaly detection algorithm based on hidden pattern. Epsilon machine, a new computational mechanics, can discover hidden pattern from the response time series. Causal State Splitting Reconstruction (CSSR), one algorithm of epsilon machine, can infer a set of causal states, which has an analogy to hidden Markov chain. Based on this set, an anomaly measure can be defined, which is the distance of two characteristic vectors. Computing all parts of the time series, an anomaly evolution curve can be got. In simulation analysis of Duffing equation, step changes appear in the anomaly curve, before Duffing oscillator begin to bifurcate. The algorithm proves to be effective in anomaly detection and warning.
It is a difficult problem how to detect such accident of a system. This paper presents a new algorithm, an anomaly detection algorithm based on hidden pattern. Epsilon machine, a new computational mechanics, can discover hidden pattern from the response time series. Causal State Splitting Reconstruction (CSSR), one algorithm of epsilon machine, can infer a set of causal states, which has an analogy to hidden Markov chain. Based on this set, an anomaly measure can be defined, which is the distance of two characteristic vectors. Computing all parts of the time series, an anomaly evolution curve can be got. In simulation analysis of Duffing equation, step changes appear in the anomaly curve, before Duffing oscillator begin to bifurcate. The algorithm proves to be effective in anomaly detection and warning.
2007, 29(6): 1492-1495.
doi: 10.3724/SP.J.1146.2005.01548
Abstract:
The relationships between loop performance (settling time, phase noise and spur signal) and loop parameters (bandwidth and phase margin) are briefly discussed in the paper. An adaptive Phase-Locked Loop (PLL) with a fast settling time and its key blocks including Phase-Frequency Detector (PFD) and charge pump are then proposed and analyzed. The proposed architecture is based on two tuning loops: a coarse-tuning loop and a fine-tuning loop. The coarse-tuning loop is used for fast convergence and the fine-tuning loop is used to complete fine adjustments. Adaptation of loop parameters occurs continuously, without switching of loop filter components, and without interaction from outside control signal. Spectre simulation based on SMIC 0.18m 1.8V supply voltage CMOS technology shows that coarse-tuning PFD can effectively cut off coarse-tuning loop, and the charge pump has a 0.1% up/down current mismatching characteristic. The adaptive PLL can reduce settling time over 30% in comparison to the conventional PLL in the same loop bandwidth.
The relationships between loop performance (settling time, phase noise and spur signal) and loop parameters (bandwidth and phase margin) are briefly discussed in the paper. An adaptive Phase-Locked Loop (PLL) with a fast settling time and its key blocks including Phase-Frequency Detector (PFD) and charge pump are then proposed and analyzed. The proposed architecture is based on two tuning loops: a coarse-tuning loop and a fine-tuning loop. The coarse-tuning loop is used for fast convergence and the fine-tuning loop is used to complete fine adjustments. Adaptation of loop parameters occurs continuously, without switching of loop filter components, and without interaction from outside control signal. Spectre simulation based on SMIC 0.18m 1.8V supply voltage CMOS technology shows that coarse-tuning PFD can effectively cut off coarse-tuning loop, and the charge pump has a 0.1% up/down current mismatching characteristic. The adaptive PLL can reduce settling time over 30% in comparison to the conventional PLL in the same loop bandwidth.
2007, 29(6): 1496-1499.
doi: 10.3724/SP.J.1146.2005.01284
Abstract:
A monolithic clock recovery circuit is proposed in this paper. The frequency of the recovered clock is 125MHz. By using of some compensation methods, such as current subtraction technology, the gain of the VCO is greatly diminished, as a result the chip area is reduced also without sacrificing the noise performance of the recovered clock. This design is implemented by a 0.25m standard CMOS technology. The active chip area is less than 0.2mm2, and the power consumption is only 10mW. The simulation results in different temperature and process condition indicate that the phase error of the recovered clock is less than 200ps and the peak-to-peak jitter is less than 150ps. A 100MHz PHY with the proposed clock recovery circuit inside is taped out and tested. The test result shows that the clock recovery circuit works properly.
A monolithic clock recovery circuit is proposed in this paper. The frequency of the recovered clock is 125MHz. By using of some compensation methods, such as current subtraction technology, the gain of the VCO is greatly diminished, as a result the chip area is reduced also without sacrificing the noise performance of the recovered clock. This design is implemented by a 0.25m standard CMOS technology. The active chip area is less than 0.2mm2, and the power consumption is only 10mW. The simulation results in different temperature and process condition indicate that the phase error of the recovered clock is less than 200ps and the peak-to-peak jitter is less than 150ps. A 100MHz PHY with the proposed clock recovery circuit inside is taped out and tested. The test result shows that the clock recovery circuit works properly.
2007, 29(6): 1500-1502.
doi: 10.3724/SP.J.1146.2005.01418
Abstract:
A micro-strip shorted antenna with Compact Electromagnetic Band-Gap structure (CEBG) is presented. A shorted antenna with identical dimensions on a conventional ground plane is also included, so that a direct performance comparison can be made. Measured data shows a gain improvement of 3dB and a significant reduction in cross polarization for the CEBG antenna. Meanwhile it also proves that to design the same resonant frequency, the CEBG structure cell size is only about 5060% of conventional structure, and this is significant in realizing EBG micro-strip phased antenna array.
A micro-strip shorted antenna with Compact Electromagnetic Band-Gap structure (CEBG) is presented. A shorted antenna with identical dimensions on a conventional ground plane is also included, so that a direct performance comparison can be made. Measured data shows a gain improvement of 3dB and a significant reduction in cross polarization for the CEBG antenna. Meanwhile it also proves that to design the same resonant frequency, the CEBG structure cell size is only about 5060% of conventional structure, and this is significant in realizing EBG micro-strip phased antenna array.
2007, 29(6): 1503-1507.
doi: 10.3724/SP.J.1146.2005.01304
Abstract:
The setting method of time-domain excitation sources is studied in this paper in order to analyzing the characteristic of waveguide by using the Multidomain PseudoSpectral Time-Domain (MPSTD) algorithm. Based on it, a rigorous analysis for a compound slot coupler by using the MPSTD algorithm is presented. Coupling slot characteristics of half-height X-band waveguide are obtained, including the resonant length and scattering parameters in different height, offsets, and tilt angles of the slot. All numerical results indicate the MPSTD is more accurate and efficient to analyze the slot coupler. And it extends application fields of MPSTD and offers a scheme for analyzing the broad-band characteristic of complex waveguide accurately and efficiently.
The setting method of time-domain excitation sources is studied in this paper in order to analyzing the characteristic of waveguide by using the Multidomain PseudoSpectral Time-Domain (MPSTD) algorithm. Based on it, a rigorous analysis for a compound slot coupler by using the MPSTD algorithm is presented. Coupling slot characteristics of half-height X-band waveguide are obtained, including the resonant length and scattering parameters in different height, offsets, and tilt angles of the slot. All numerical results indicate the MPSTD is more accurate and efficient to analyze the slot coupler. And it extends application fields of MPSTD and offers a scheme for analyzing the broad-band characteristic of complex waveguide accurately and efficiently.
2007, 29(6): 1508-1510.
doi: 10.3724/SP.J.1146.2005.01352
Abstract:
Bandwidth property of mode conversion from the TE□10 mode of a rectangular waveguide to the TE⊙01 mode of a coaxial waveguide is studied. The influence of mode competition on operating mode inside the bandwidth is analyzed and the effect of mode filter on mode conversion property is discussed. The simulation results with Ansoft HFSS show that the influence of mode competition can be weakened with a mode filter, and the operating bandwidth of 700MHz can be reached while the mode conversion efficiency is more than 70% at Ku band for the new structure.
Bandwidth property of mode conversion from the TE□10 mode of a rectangular waveguide to the TE⊙01 mode of a coaxial waveguide is studied. The influence of mode competition on operating mode inside the bandwidth is analyzed and the effect of mode filter on mode conversion property is discussed. The simulation results with Ansoft HFSS show that the influence of mode competition can be weakened with a mode filter, and the operating bandwidth of 700MHz can be reached while the mode conversion efficiency is more than 70% at Ku band for the new structure.
2007, 29(6): 1514-1517.
doi: 10.3724/SP.J.1146.2005.01092
Abstract:
Blind synchronization algorithm is developed for estimating jointly timing and carrier frequency offset of Lattice Orthogonal Frequency Division Multiplexing (LOFDM) systems, which is based on the cyclostationarity of LOFDM signals. The theoretical analysis shows that the following characters are occupied by the proposed algorithm. The proposed estimators can effectively combat the fading caused by the frequency selective slowly time-varying channels. In the case of wide-sense stationary noise, the performance of the estimators is independent of Signal-to-Noise Ratio (SNR) received, and then they operate well in low SNR. Moreover, the performance of the symbol timing estimator and that of carrier frequency offset estimator do not influence each other. Finally, simulation results demonstrate the performance of the presented estimators.
Blind synchronization algorithm is developed for estimating jointly timing and carrier frequency offset of Lattice Orthogonal Frequency Division Multiplexing (LOFDM) systems, which is based on the cyclostationarity of LOFDM signals. The theoretical analysis shows that the following characters are occupied by the proposed algorithm. The proposed estimators can effectively combat the fading caused by the frequency selective slowly time-varying channels. In the case of wide-sense stationary noise, the performance of the estimators is independent of Signal-to-Noise Ratio (SNR) received, and then they operate well in low SNR. Moreover, the performance of the symbol timing estimator and that of carrier frequency offset estimator do not influence each other. Finally, simulation results demonstrate the performance of the presented estimators.
2007, 29(6): 1518-1520.
doi: 10.3724/SP.J.1146.2006.01201
Abstract:
How to distinguish the ghost-mode in window is illuminated at first and then the method is introduced using Microwave Studio, a three-dimension simulating soft, to improve a X-band output window. The data of calculation and test are very good and the window can be used in practice, which is very useful for output system designs.
How to distinguish the ghost-mode in window is illuminated at first and then the method is introduced using Microwave Studio, a three-dimension simulating soft, to improve a X-band output window. The data of calculation and test are very good and the window can be used in practice, which is very useful for output system designs.
2007, 29(6): 1521-1524.
doi: 10.3724/SP.J.1146.2005.01384
Abstract:
In this paper reaction wheels inner friction and static and dynamic imbalance are particularly analysed by reaction wheels dynamics. A mathematical model is set up. A method of control disturb is used. for example, the method to estimate the inner friction torque is introduced by using compensation observer, and the method to estimate the wheel static imbalance and dynamic imbalance is introduced by using late and forward revise compensation. And the numerical simulation model is constituted. Finally, the simulation results prove that this method can improve satellite attitude pointing accuracy and stability efficiently.
In this paper reaction wheels inner friction and static and dynamic imbalance are particularly analysed by reaction wheels dynamics. A mathematical model is set up. A method of control disturb is used. for example, the method to estimate the inner friction torque is introduced by using compensation observer, and the method to estimate the wheel static imbalance and dynamic imbalance is introduced by using late and forward revise compensation. And the numerical simulation model is constituted. Finally, the simulation results prove that this method can improve satellite attitude pointing accuracy and stability efficiently.
2007, 29(6): 1511-1513.
doi: 10.3724/SP.J.1146.2005.01046
Abstract:
In 2005, Zhang et al. proposed an efficient group signature scheme based on RSA, the total computation cost of signature and verification requires only 9 modular exponentiations. This paper will show that Zhang et al.s scheme is insecure, any group member colludes with repeal center can generate a valid group signature without using his secret parameters. Additional, it will show that the signer identity verification algorithm is error, identity verification expression is independent of the group signature. That is, the signer identity verification algorithm cannot find who the signer is. Finally, it will show that their scheme is not unlinkable.
In 2005, Zhang et al. proposed an efficient group signature scheme based on RSA, the total computation cost of signature and verification requires only 9 modular exponentiations. This paper will show that Zhang et al.s scheme is insecure, any group member colludes with repeal center can generate a valid group signature without using his secret parameters. Additional, it will show that the signer identity verification algorithm is error, identity verification expression is independent of the group signature. That is, the signer identity verification algorithm cannot find who the signer is. Finally, it will show that their scheme is not unlinkable.
