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2006 Vol. 28, No. 5
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2006, 28(5): 769-773.
Abstract:
A random early expiration detection based buffer management algorithm is proposed for real-time traffic over wireless networks. Considering the characters of wireless link such as variable channel condition and transmission error, the algorithm is composed of three steps: aimed to guarantee the delay of retransmission packets, using the method which is similar to early congestion detection to detect expiration and discard packets in advance; adaptive adjusting the drop probability based on the trend of channel condition; re-calculating the threshold value when the link rate is changed. The influence on the TCP performance is also considered in the design. Simulation results show that the system performance is improved through using the proposed algorithm.
A random early expiration detection based buffer management algorithm is proposed for real-time traffic over wireless networks. Considering the characters of wireless link such as variable channel condition and transmission error, the algorithm is composed of three steps: aimed to guarantee the delay of retransmission packets, using the method which is similar to early congestion detection to detect expiration and discard packets in advance; adaptive adjusting the drop probability based on the trend of channel condition; re-calculating the threshold value when the link rate is changed. The influence on the TCP performance is also considered in the design. Simulation results show that the system performance is improved through using the proposed algorithm.
2006, 28(5): 774-779.
Abstract:
An admission control algorithm with deterministic delay guarantees in DiffServ networks, Service Admission Control in DiffServ (SACiD), is developed in this paper. It can not only prevent the end-to-end delay of admitted services from violating the allowed upper bound, but alalo utilize network resources efficiently. Simulation results indicate that the performance of SACiD is close to that of the similar algorithm in IntServ networks with little memory requirement. Due to its simplicity and scalability, SACiD can support resource management in DiffServ networks.
An admission control algorithm with deterministic delay guarantees in DiffServ networks, Service Admission Control in DiffServ (SACiD), is developed in this paper. It can not only prevent the end-to-end delay of admitted services from violating the allowed upper bound, but alalo utilize network resources efficiently. Simulation results indicate that the performance of SACiD is close to that of the similar algorithm in IntServ networks with little memory requirement. Due to its simplicity and scalability, SACiD can support resource management in DiffServ networks.
2006, 28(5): 780-784.
Abstract:
In Ad hoc networks, low reliability of wireless link makes the scalability of multicast group degrade drastically, and FEC(Forward Error Correction) technique and NACK(Negative ACKnowledgement)-based mechanism, which guarantees reliable transport of multicast in wired networks, is not adapt to be deployed in Ad hoc networks. In this paper, focusing on improving the scalability of multicast in Ad hoc networks, a Reliable Multicast Transport Scheme (RMTS) consist of PDA(Packet Dispersal Algorithm) and ARM(Active Retransmission Model) is proposed to guarantee reliable transports of multicast. Both theory analyses and simulation result show the merits of validity, simpleness, low resources-occupied and moderate overhead.
In Ad hoc networks, low reliability of wireless link makes the scalability of multicast group degrade drastically, and FEC(Forward Error Correction) technique and NACK(Negative ACKnowledgement)-based mechanism, which guarantees reliable transport of multicast in wired networks, is not adapt to be deployed in Ad hoc networks. In this paper, focusing on improving the scalability of multicast in Ad hoc networks, a Reliable Multicast Transport Scheme (RMTS) consist of PDA(Packet Dispersal Algorithm) and ARM(Active Retransmission Model) is proposed to guarantee reliable transports of multicast. Both theory analyses and simulation result show the merits of validity, simpleness, low resources-occupied and moderate overhead.
2006, 28(5): 785-788.
Abstract:
A topology-transparent Time Division Multiple Access (TDMA) with reservation for MIMO link is proposed for multi-hop Ad hoc networks in this paper. By reservation each node transmits simultaneously all data streams in its assigned collision-free slots and utilizes free slots among other non-assigned slots and its assigned collision slots by probability to transmit a part of all data streams. The protocol is suitable for distributed application since it need not know the whole network topology information. Through theoretical analysis, the minimum throughput and optimal frame length are derived. The results show that the protocol is robust to topology change.
A topology-transparent Time Division Multiple Access (TDMA) with reservation for MIMO link is proposed for multi-hop Ad hoc networks in this paper. By reservation each node transmits simultaneously all data streams in its assigned collision-free slots and utilizes free slots among other non-assigned slots and its assigned collision slots by probability to transmit a part of all data streams. The protocol is suitable for distributed application since it need not know the whole network topology information. Through theoretical analysis, the minimum throughput and optimal frame length are derived. The results show that the protocol is robust to topology change.
2006, 28(5): 789-794.
Abstract:
A fair and efficient bandwidth allocation scheduling architecture for IEEE 802.16 Broadband Wireless Access (BWA) systems in TDD mode is proposed. In this area, comparing with the traditional fixed bandwidth allocation, the proposed scheduling architecture allocates uplink and downlink bandwidth simultaneously and dynamically. A Deficit Fair Priority Queue (DFDQ) algorithm is proposed to schedule different service flow, which provides more fairness to the system. The simulation results show the proposed architecture can meet the QoS requirement and fairness for all types of traffic.
A fair and efficient bandwidth allocation scheduling architecture for IEEE 802.16 Broadband Wireless Access (BWA) systems in TDD mode is proposed. In this area, comparing with the traditional fixed bandwidth allocation, the proposed scheduling architecture allocates uplink and downlink bandwidth simultaneously and dynamically. A Deficit Fair Priority Queue (DFDQ) algorithm is proposed to schedule different service flow, which provides more fairness to the system. The simulation results show the proposed architecture can meet the QoS requirement and fairness for all types of traffic.
2006, 28(5): 795-799.
Abstract:
This paper studies the media access control protocol and key technologies in ultra-wideband wireless networks. It is mainly analyzed that the basic principle of IEEE 802.15.3 media access control protocol which is as one of the most suitable protocols for ultra-wideband networks. Using the character of accurate location information of ultra-wideband communication, the IEEE 802.15.3 protocol is improved and a scheme which is media access control technique based space reuse is proposed. Simulation results reveal this new proposal improves the performance of network throughput and packet access delay compared with basic IEEE 802.15.3 media access control scheme.
This paper studies the media access control protocol and key technologies in ultra-wideband wireless networks. It is mainly analyzed that the basic principle of IEEE 802.15.3 media access control protocol which is as one of the most suitable protocols for ultra-wideband networks. Using the character of accurate location information of ultra-wideband communication, the IEEE 802.15.3 protocol is improved and a scheme which is media access control technique based space reuse is proposed. Simulation results reveal this new proposal improves the performance of network throughput and packet access delay compared with basic IEEE 802.15.3 media access control scheme.
2006, 28(5): 800-804.
Abstract:
Taking into account the features of satellite networking，solving the measurement for traffic in satellite networks by adopting passive measurement method based on SNMP is studied in this paper. The principle of measurement for network traffic using SNMP is studied firstly. Based on this, a selecting algorithm of nodes monitored is introduced so as to decrease the number of devices monitored and enhance the network performance of measurement for traffic. Finally, the flow chart of application explored in practice and the related experimental results are given. Further calculating or statistical disposing using the results can be processed. Then the distribution and utilization of resources in satellite network can be confirmed and the network can be adjusted to the optimal performance. The whole procedure of measurement for traffic is implemented and real-time exact data and available network management evidence are provided for the implementation of traffic engineering in satellite network.
Taking into account the features of satellite networking，solving the measurement for traffic in satellite networks by adopting passive measurement method based on SNMP is studied in this paper. The principle of measurement for network traffic using SNMP is studied firstly. Based on this, a selecting algorithm of nodes monitored is introduced so as to decrease the number of devices monitored and enhance the network performance of measurement for traffic. Finally, the flow chart of application explored in practice and the related experimental results are given. Further calculating or statistical disposing using the results can be processed. Then the distribution and utilization of resources in satellite network can be confirmed and the network can be adjusted to the optimal performance. The whole procedure of measurement for traffic is implemented and real-time exact data and available network management evidence are provided for the implementation of traffic engineering in satellite network.
2006, 28(5): 805-809.
Abstract:
Traditional input-queued switches based on crossbar are insufficient in providing good QoS performance. As a contrast, the CICQ(Combined Input and Cross-point buffered Queuing) switches can provide almost 100% throughput under different input traffic, the performance of which is very close to the OQ(Output-Queued) switch, and has the potentials to support good QoS. Based on the CICQ switches, a new scheme is put forward, which can realize distributed weighted fair schedule for the packets of variable length, and have both the scalability of input-queued switches and QoS performance of output-queued switches. The issue of updating the virtual time of back-pressured queues is also discussed. Simulation results show the scheme is very effective and has good performance.
Traditional input-queued switches based on crossbar are insufficient in providing good QoS performance. As a contrast, the CICQ(Combined Input and Cross-point buffered Queuing) switches can provide almost 100% throughput under different input traffic, the performance of which is very close to the OQ(Output-Queued) switch, and has the potentials to support good QoS. Based on the CICQ switches, a new scheme is put forward, which can realize distributed weighted fair schedule for the packets of variable length, and have both the scalability of input-queued switches and QoS performance of output-queued switches. The issue of updating the virtual time of back-pressured queues is also discussed. Simulation results show the scheme is very effective and has good performance.
2006, 28(5): 810-814.
Abstract:
To improve the Binary Exponential Backoff algorithm (BEB)s channel throughput of IEEE 802.11 protocol, a novel Collision Reduced Multiple Access protocol (CRMA) is proposed based on slow contention window decrease mechanism and runtime optimization method. By integrating slow CW decrease scheme with runtime optimization mechanism to effectively solve no state information indicating the actual contention level of BEB algorithm after a successful transmission, CRMA protocol can record the current backoff stage of the latest successful transmission under the overload network precisely. As a result, it decreases the collision times and improve the channel utilization. The CRMA protocol could be compatible completely with pre-existed IEEE 802.11 protocol, and it is represented by its simplicity, integrability, complete distribution and adaptiveness. The performance analysis and numerical results show that its performance is much better than the IEEE 802.11 protocol and other recent multiple access mechanisms because of the accurate estimation of congested level before transmission and the effective record of backoff stage after a successive transmission.
To improve the Binary Exponential Backoff algorithm (BEB)s channel throughput of IEEE 802.11 protocol, a novel Collision Reduced Multiple Access protocol (CRMA) is proposed based on slow contention window decrease mechanism and runtime optimization method. By integrating slow CW decrease scheme with runtime optimization mechanism to effectively solve no state information indicating the actual contention level of BEB algorithm after a successful transmission, CRMA protocol can record the current backoff stage of the latest successful transmission under the overload network precisely. As a result, it decreases the collision times and improve the channel utilization. The CRMA protocol could be compatible completely with pre-existed IEEE 802.11 protocol, and it is represented by its simplicity, integrability, complete distribution and adaptiveness. The performance analysis and numerical results show that its performance is much better than the IEEE 802.11 protocol and other recent multiple access mechanisms because of the accurate estimation of congested level before transmission and the effective record of backoff stage after a successive transmission.
2006, 28(5): 815-819.
Abstract:
As a kind of dynamic self-organized network, wireless Ad hoc network is faced with serious security threat. On the basis of analyzing the characteristics of Ad hoc network, a hierarchical group key management solution (Hierarchical Group Controller-Based Group Key Management protocol) based on extended Diffie-Hellman protocol is presented. The HGKM utilizes member filter function and hierarchy to maintain a single group key to adapt to the special requirements for frequent key refresh of Ad hoc network.
As a kind of dynamic self-organized network, wireless Ad hoc network is faced with serious security threat. On the basis of analyzing the characteristics of Ad hoc network, a hierarchical group key management solution (Hierarchical Group Controller-Based Group Key Management protocol) based on extended Diffie-Hellman protocol is presented. The HGKM utilizes member filter function and hierarchy to maintain a single group key to adapt to the special requirements for frequent key refresh of Ad hoc network.
2006, 28(5): 820-822.
Abstract:
Based on group signature scheme from bilinear pairings, a new offline fair cash scheme is presented. Because of setting up on the elliptic curve group and without using blind signature scheme , this scheme has many properties such as having simple structure, security, efficiency, trapdoor-free and so on.
Based on group signature scheme from bilinear pairings, a new offline fair cash scheme is presented. Because of setting up on the elliptic curve group and without using blind signature scheme , this scheme has many properties such as having simple structure, security, efficiency, trapdoor-free and so on.
2006, 28(5): 823-826.
Abstract:
A multi-signature scheme is a digital signature scheme that allow multiple signers to generate in a collaborative and simultaneous manner. In the application of multi-signature, the signing order among co-signers may satisfy a special sequence and sometimes the each signer can express his intention associating with the message to be signed and referring by others. Considering the need of application, a multi-signature from bilinear pairings is proposed in this paper. The proposed scheme has two properties that it can set up the order of signing in advance and add the intention of signer into the signature. The security analysis of the new scheme shows that it can resist all kind of outsider and insider attacks.
A multi-signature scheme is a digital signature scheme that allow multiple signers to generate in a collaborative and simultaneous manner. In the application of multi-signature, the signing order among co-signers may satisfy a special sequence and sometimes the each signer can express his intention associating with the message to be signed and referring by others. Considering the need of application, a multi-signature from bilinear pairings is proposed in this paper. The proposed scheme has two properties that it can set up the order of signing in advance and add the intention of signer into the signature. The security analysis of the new scheme shows that it can resist all kind of outsider and insider attacks.
2006, 28(5): 827-831.
Abstract:
A correlation attack on A5/1 algorithm can be educed by the linear filling weakness in initiate process of A5/1 algorithm. An aberrant A5/1 sequence can be obtained from it, which have treated by statistic tools to get A5/1 statistic trait, so the distinction of A5/1 output from real random sequence can be found. Test results show that this method can work effectively.
A correlation attack on A5/1 algorithm can be educed by the linear filling weakness in initiate process of A5/1 algorithm. An aberrant A5/1 sequence can be obtained from it, which have treated by statistic tools to get A5/1 statistic trait, so the distinction of A5/1 output from real random sequence can be found. Test results show that this method can work effectively.
2006, 28(5): 832-835.
Abstract:
Towards making the construction method on the DES-model pseudorandom permutations given by Luby and Rackoff optimal and practical, a new construction method on pseudorandom permutations is provided. Based on the random oracle model by showing that two DES-model permutations are sufficient to be super-pseudorandom permutation together with initial and final rotation permutations, the complexity of construction is reduced samewhat and its proof of security is simplified The revised construction reduces the success probability of the adversary and the upper bound of advantage and also requirements of the first and the end functions.
Towards making the construction method on the DES-model pseudorandom permutations given by Luby and Rackoff optimal and practical, a new construction method on pseudorandom permutations is provided. Based on the random oracle model by showing that two DES-model permutations are sufficient to be super-pseudorandom permutation together with initial and final rotation permutations, the complexity of construction is reduced samewhat and its proof of security is simplified The revised construction reduces the success probability of the adversary and the upper bound of advantage and also requirements of the first and the end functions.
2006, 28(5): 836-839.
Abstract:
The VV algorithm is very suitable for carrier synchronization of burst signal. After VV algorithm, a post processing is needed for eliminating the phase equivocation which is brought by the residual frequency and the cycle slip can be avoided. In this paper, a new post processing method is put forward. It has a good effect on the phase equivocation brought by both residual frequency and noise. Contrast to some other methods, it reduces the probability of cycle slip greatly. Simulation results prove that this method had a good performance and can apply to the demodulation of MPSK burst signal.
The VV algorithm is very suitable for carrier synchronization of burst signal. After VV algorithm, a post processing is needed for eliminating the phase equivocation which is brought by the residual frequency and the cycle slip can be avoided. In this paper, a new post processing method is put forward. It has a good effect on the phase equivocation brought by both residual frequency and noise. Contrast to some other methods, it reduces the probability of cycle slip greatly. Simulation results prove that this method had a good performance and can apply to the demodulation of MPSK burst signal.
2006, 28(5): 840-843.
Abstract:
This paper presents a new combined algorithm based on FFT for frame synchronization and frequency offset estimation. The algorithm can achieve frame synchronization effectively in the presence of a frequency offset and the frequency offset estimation range is －Rs/2~Rs/2. Simulation results indicate that the proposed algorithm can outperform existing methods when a frequency offset exists.
This paper presents a new combined algorithm based on FFT for frame synchronization and frequency offset estimation. The algorithm can achieve frame synchronization effectively in the presence of a frequency offset and the frequency offset estimation range is －Rs/2~Rs/2. Simulation results indicate that the proposed algorithm can outperform existing methods when a frequency offset exists.
2006, 28(5): 844-847.
Abstract:
A novel image coding algorithm based on coefficients of interest is proposed in terms of the special needs of remote-sensing images. When coding rate is given, the entropy estimate is calculated from the coefficients of the given image, so that the last coding bit-plane can be derived when the image is coded normally. The difference of the algorithm from the one for region-of-interest algorithm lies in that the region and the scaled value need not be preappointed, and the most important is that all the coefficients in bands are not scaled up, while the coefficients of interest and the scaled value are deduced from the given image in the algorithm. This algorithm can be thought as the generalization from the region-of-interest algorithm, which is smarter and more valid than the region of interest coding algorithm. The simulation and the experimental results show that the small targets in the remote-sensing images can be saved validly while the whole image quality decreases a little.
A novel image coding algorithm based on coefficients of interest is proposed in terms of the special needs of remote-sensing images. When coding rate is given, the entropy estimate is calculated from the coefficients of the given image, so that the last coding bit-plane can be derived when the image is coded normally. The difference of the algorithm from the one for region-of-interest algorithm lies in that the region and the scaled value need not be preappointed, and the most important is that all the coefficients in bands are not scaled up, while the coefficients of interest and the scaled value are deduced from the given image in the algorithm. This algorithm can be thought as the generalization from the region-of-interest algorithm, which is smarter and more valid than the region of interest coding algorithm. The simulation and the experimental results show that the small targets in the remote-sensing images can be saved validly while the whole image quality decreases a little.
2006, 28(5): 848-851.
Abstract:
An optimized approach based on texture synthesis for filling-in blocks of missing data is presented in this paper. According to coarseness analysis and the character of inpainting algorithm, parts of image blocks would be dropped purposively. And then, this method is applied to the second-time image compression along with other compression algorithms such as JPEG, and the compression ratio is highly improved.
An optimized approach based on texture synthesis for filling-in blocks of missing data is presented in this paper. According to coarseness analysis and the character of inpainting algorithm, parts of image blocks would be dropped purposively. And then, this method is applied to the second-time image compression along with other compression algorithms such as JPEG, and the compression ratio is highly improved.
2006, 28(5): 852-856.
Abstract:
Orthogonal Hermite pulse shapes used for Ultra Wide-Band(UWB) communication are proposed. The paper presents a novel method for multi-user transmission system in UWB communication. By transmitting multiple orthogonal Hermite pulses simultaneously, the UWB multi-user transmission system achieves good performance characteristic. Also it proposes that orthogonal Hermite pulses can be applied to the DS-CDMA system in UWB to access more users at one time.
Orthogonal Hermite pulse shapes used for Ultra Wide-Band(UWB) communication are proposed. The paper presents a novel method for multi-user transmission system in UWB communication. By transmitting multiple orthogonal Hermite pulses simultaneously, the UWB multi-user transmission system achieves good performance characteristic. Also it proposes that orthogonal Hermite pulses can be applied to the DS-CDMA system in UWB to access more users at one time.
2006, 28(5): 857-860.
Abstract:
Successive Interference Cancellation (SIC) can effectively mitigate Multiple Access Interference (MAI) and improve the capacity of Direct-Sequence Code-Division Multiple Access (DS-CDMA) systems. In this paper, for the uplink of a single cell DS-CDMA system, the capacity limits of a conventional single-user detection receiver, a system with linear SIC receiver, and a system with perfect SIC are derived for an Addictive White Gaussian Noise (AWGN) channel. The results show that the linear SIC system can provide a much larger capacity compared with the conventional system in all cases. Moreover, with increasing of the number of the users in the system, the difference between the whole power of the perfect SIC and that of the linear SIC increases. So, if the perfect SIC is used to guide the power allocation, the resulting performance will be significantly worse than predicted.
Successive Interference Cancellation (SIC) can effectively mitigate Multiple Access Interference (MAI) and improve the capacity of Direct-Sequence Code-Division Multiple Access (DS-CDMA) systems. In this paper, for the uplink of a single cell DS-CDMA system, the capacity limits of a conventional single-user detection receiver, a system with linear SIC receiver, and a system with perfect SIC are derived for an Addictive White Gaussian Noise (AWGN) channel. The results show that the linear SIC system can provide a much larger capacity compared with the conventional system in all cases. Moreover, with increasing of the number of the users in the system, the difference between the whole power of the perfect SIC and that of the linear SIC increases. So, if the perfect SIC is used to guide the power allocation, the resulting performance will be significantly worse than predicted.
2006, 28(5): 861-864.
Abstract:
This paper focuses on the geometrical properties of Inter-Satellite Links (ISLs) of the small satellites formation flying under the elliptical orbits, including the azimuth, elevation and the distance. The article addresses the mathematical formula for these characteristics., and then presents the simulation results based on the given example. The paper also analyzes the law that the formation flyings ISLs geometrical characteristics change with the parameters of the satellite constellation. These results are important for futures constellation design , satellite networking, etc.
This paper focuses on the geometrical properties of Inter-Satellite Links (ISLs) of the small satellites formation flying under the elliptical orbits, including the azimuth, elevation and the distance. The article addresses the mathematical formula for these characteristics., and then presents the simulation results based on the given example. The paper also analyzes the law that the formation flyings ISLs geometrical characteristics change with the parameters of the satellite constellation. These results are important for futures constellation design , satellite networking, etc.
2006, 28(5): 865-870.
Abstract:
Based on the functionality and traffic characteristics of the Medium Earth Orbit Tracking and Data Relay Satellite System(MEO-TDRSS), the coverage properties and Inter-Satellite Link(ISL) performances of four familiar satellite constellation schemes which are adopted as the MEO-TDRSS of China are simulated and compared. The simulation results indicate that Rosette and Common-track constellations, whose satellites are distributed in the celestial sphere uniformly, are appropriate for MEO-TDRSS of China.
Based on the functionality and traffic characteristics of the Medium Earth Orbit Tracking and Data Relay Satellite System(MEO-TDRSS), the coverage properties and Inter-Satellite Link(ISL) performances of four familiar satellite constellation schemes which are adopted as the MEO-TDRSS of China are simulated and compared. The simulation results indicate that Rosette and Common-track constellations, whose satellites are distributed in the celestial sphere uniformly, are appropriate for MEO-TDRSS of China.
2006, 28(5): 871-874.
Abstract:
High data transmission rates and high mobility give rise to time selectivity and frequency selectivity in wireless communication channels. This paper investigates Multi-Input Multi-Output (MIMO) time and frequency doubly selective channel estimation using polynomial interpolation method for data block transmissions. Firstly, a polynomial interpolation model is introduced to represent doubly selective MIMO channel; then, relying on channel Doppler fading rate and the polynomial error term, the polynomial model order and the length of the whole data block are obtained; Finally, based on polynomial interpolation channel model, MIMO doubly selective channels are estimated using pilot symbol assisted modulation. Simulation results show that the proposed estimation method has effective performance.
High data transmission rates and high mobility give rise to time selectivity and frequency selectivity in wireless communication channels. This paper investigates Multi-Input Multi-Output (MIMO) time and frequency doubly selective channel estimation using polynomial interpolation method for data block transmissions. Firstly, a polynomial interpolation model is introduced to represent doubly selective MIMO channel; then, relying on channel Doppler fading rate and the polynomial error term, the polynomial model order and the length of the whole data block are obtained; Finally, based on polynomial interpolation channel model, MIMO doubly selective channels are estimated using pilot symbol assisted modulation. Simulation results show that the proposed estimation method has effective performance.
2006, 28(5): 875-878.
Abstract:
This paper present a new DOA estimation algorithm in impulsive noise environment. The algorithm uses firstly screened ratio principle to construct the correlation matrix of the array data and then implements the DOA estimation by MUSIC algorithm. In comparison with the Fractional Lower Order Moment (FLOM)-based algorithms, the proposed algorithm does not need the selection of the FLOM parameter. Computer simulations show that the algorithm is more robust and more accurate than FLOM-MUSIC algorithm.
This paper present a new DOA estimation algorithm in impulsive noise environment. The algorithm uses firstly screened ratio principle to construct the correlation matrix of the array data and then implements the DOA estimation by MUSIC algorithm. In comparison with the Fractional Lower Order Moment (FLOM)-based algorithms, the proposed algorithm does not need the selection of the FLOM parameter. Computer simulations show that the algorithm is more robust and more accurate than FLOM-MUSIC algorithm.
2006, 28(5): 879-882.
Abstract:
This paper presents a decoupled maximum likelihood(ML) detection algorithm, which utilizes the orthogonal characteristic of signal, decoupled the combined ML detection into separated one, under the assumption that CSI is known at the receiver. Utilizing appropriate channel estimation algorithm, the decoupled algorithm not only sharply reduces the computational complexity compared to the noncoherent ML detection, but also improves the performance. Simulation results confirm the effectiveness of the algorithm.
This paper presents a decoupled maximum likelihood(ML) detection algorithm, which utilizes the orthogonal characteristic of signal, decoupled the combined ML detection into separated one, under the assumption that CSI is known at the receiver. Utilizing appropriate channel estimation algorithm, the decoupled algorithm not only sharply reduces the computational complexity compared to the noncoherent ML detection, but also improves the performance. Simulation results confirm the effectiveness of the algorithm.
2006, 28(5): 883-889.
Abstract:
The updated image fusion schemes could not identify meaningful image features from noises, the input noise is treated as valid information and transferred into the fused output. After complex wavelet transformation (CWT), structured information is decomposed into varying scales and directions. Based on CWT, two structured information entropies, intra-band structured information entropy and inter-band structured information entropy, are formulated to express the structurization level of image features. Preceding the image fusion process, the metrics are employed to weight all inputs. As a result, the perceptual salient inputs are enhanced while the noise inputs are de-emphasized adaptively. Comparing the visual aesthetics of fusion results and analyzing the performance objectively, show the good performance of the proposed image fusion algorithm.
The updated image fusion schemes could not identify meaningful image features from noises, the input noise is treated as valid information and transferred into the fused output. After complex wavelet transformation (CWT), structured information is decomposed into varying scales and directions. Based on CWT, two structured information entropies, intra-band structured information entropy and inter-band structured information entropy, are formulated to express the structurization level of image features. Preceding the image fusion process, the metrics are employed to weight all inputs. As a result, the perceptual salient inputs are enhanced while the noise inputs are de-emphasized adaptively. Comparing the visual aesthetics of fusion results and analyzing the performance objectively, show the good performance of the proposed image fusion algorithm.
2006, 28(5): 890-894.
Abstract:
A novel algorithm for image inpainting based on Compactly Supported Radial Basis Functions(CSRBF) interpolation is proposed. The algorithm looks an image as an incomplete 3D points set. The 2D image inpainting problem is converted into implicit surface reconstruction problem from 3D points set. To construct the implicit surface for approximating the points set by using Radial Basis Functions(RBF) can interpolate the points in absent portion, and then resample from the constructed surface can calculate the pixels value of damaged or removed portion on the image. Using CSRBF, the matrix of corresponding system of the linear algebraic equations is spare and bounded. So it can decrease the complexity of RBF algorithm. A number of examples on image inpainting demonstrates that the algorithm is an practical one and using the algorithm can obtain good results.
A novel algorithm for image inpainting based on Compactly Supported Radial Basis Functions(CSRBF) interpolation is proposed. The algorithm looks an image as an incomplete 3D points set. The 2D image inpainting problem is converted into implicit surface reconstruction problem from 3D points set. To construct the implicit surface for approximating the points set by using Radial Basis Functions(RBF) can interpolate the points in absent portion, and then resample from the constructed surface can calculate the pixels value of damaged or removed portion on the image. Using CSRBF, the matrix of corresponding system of the linear algebraic equations is spare and bounded. So it can decrease the complexity of RBF algorithm. A number of examples on image inpainting demonstrates that the algorithm is an practical one and using the algorithm can obtain good results.
2006, 28(5): 895-900.
Abstract:
A method to identify Chinese organization names by utilizing SVM (Support Vector Machines) and RS (Rough Set) is provided. Forming rule of organization name is defined based on semanteme collocation relation, and then the un-redundancy set of rough forming rules can be learned by employing attribute reduction in RS automatically. A chain of words matching forming rule is selected first as candidate, then a SVM classifier discern whether a candidate is real organization name according to candidate semanteme and its contextual semanteme while recognizing. Results of open testing achieve F-measure 82.06% in 16.17 million words news based on this project separately.
A method to identify Chinese organization names by utilizing SVM (Support Vector Machines) and RS (Rough Set) is provided. Forming rule of organization name is defined based on semanteme collocation relation, and then the un-redundancy set of rough forming rules can be learned by employing attribute reduction in RS automatically. A chain of words matching forming rule is selected first as candidate, then a SVM classifier discern whether a candidate is real organization name according to candidate semanteme and its contextual semanteme while recognizing. Results of open testing achieve F-measure 82.06% in 16.17 million words news based on this project separately.
2006, 28(5): 901-904.
Abstract:
A new algorithm of mixed noise removal for digital image is presented combing median filter and fuzzy technology. The pixels of an image are divided into two sets: impulse noise points and pixels polluted by Gaussian noise. The min-max operator is used first. Then impulse noise is detected accurately by using image texture and removed by median filter. A detail-preserving fuzzy filter is adopted to reduce Gaussian noise contained in other pixels. Experiments show that the algorithm can remove mixed impulse and Gaussian noise efficiently while protecting image details.
A new algorithm of mixed noise removal for digital image is presented combing median filter and fuzzy technology. The pixels of an image are divided into two sets: impulse noise points and pixels polluted by Gaussian noise. The min-max operator is used first. Then impulse noise is detected accurately by using image texture and removed by median filter. A detail-preserving fuzzy filter is adopted to reduce Gaussian noise contained in other pixels. Experiments show that the algorithm can remove mixed impulse and Gaussian noise efficiently while protecting image details.
2006, 28(5): 905-908.
Abstract:
According to Hilbert-Huang Transform (HHT) theory, the signals Intrinsic Mode Function (IMF) is extracted by Empirical Mode Decomposition (EMD). Its time-frequency-amplitude spectrum and marginal spectrum are obtained by Hilbert transform. In the basis of summarizing the limitation of the Hilbert transform theory and its realization, an algorithm based on zero-crossing and extremum estimation to obtain instantaneous frequency and instantaneous amplitude is presented. The positions of zero-crossings and extrema are obtained accurately by interpolating the discrete signal. The instantaneous frequency and instantaneous amplitude of relative points are obtained. The signals instantaneous frequency and instantaneous amplitude waveform are obtained by cubic spline interpolation computation. By testing the result and comparing the detail of result with Hilbert transform method through several representative examples, it shows that the instantaneous frequency and instantaneous amplitude obtained by zero-crossing and extremum estimation algorithm are more precise and the frequency resolution is better.
According to Hilbert-Huang Transform (HHT) theory, the signals Intrinsic Mode Function (IMF) is extracted by Empirical Mode Decomposition (EMD). Its time-frequency-amplitude spectrum and marginal spectrum are obtained by Hilbert transform. In the basis of summarizing the limitation of the Hilbert transform theory and its realization, an algorithm based on zero-crossing and extremum estimation to obtain instantaneous frequency and instantaneous amplitude is presented. The positions of zero-crossings and extrema are obtained accurately by interpolating the discrete signal. The instantaneous frequency and instantaneous amplitude of relative points are obtained. The signals instantaneous frequency and instantaneous amplitude waveform are obtained by cubic spline interpolation computation. By testing the result and comparing the detail of result with Hilbert transform method through several representative examples, it shows that the instantaneous frequency and instantaneous amplitude obtained by zero-crossing and extremum estimation algorithm are more precise and the frequency resolution is better.
2006, 28(5): 909-914.
Abstract:
The issue of Direction-Of-Arrival (DOA) estimation in multiple subarrays is addressed. It is assumed that an array is composed of several uniform linear arrays (ULAs) of arbitrary known geometry, but there are mutual coupling between sensors of each subarray. By using the banded, symmetric Toeplitz character of the ULAs and the block diagonal character of the multiple subarrays, a new decoupling DOA estimation and self-calibration algorithm is proposed. The new algorithm can provides accurate DOA estimation without the knowledge of mutual coupling. In addition, the mutual coupling coefficients for array self-calibration can be achieved simultaneously. Instead of multidimensional nonlinear search or iterative computation, the algorithm just uses a one-dimensional search and can reduce the computation burden. DOA identifiability issue for such arrays is discussed, and the corresponding Cramer-Rao Bound (CRB) is derived also. Monte-Carlo simulations illustrate that the proposed algorithm possesses the better performance of low computational complexity, high resolution and better accuracy of self-calibration.
The issue of Direction-Of-Arrival (DOA) estimation in multiple subarrays is addressed. It is assumed that an array is composed of several uniform linear arrays (ULAs) of arbitrary known geometry, but there are mutual coupling between sensors of each subarray. By using the banded, symmetric Toeplitz character of the ULAs and the block diagonal character of the multiple subarrays, a new decoupling DOA estimation and self-calibration algorithm is proposed. The new algorithm can provides accurate DOA estimation without the knowledge of mutual coupling. In addition, the mutual coupling coefficients for array self-calibration can be achieved simultaneously. Instead of multidimensional nonlinear search or iterative computation, the algorithm just uses a one-dimensional search and can reduce the computation burden. DOA identifiability issue for such arrays is discussed, and the corresponding Cramer-Rao Bound (CRB) is derived also. Monte-Carlo simulations illustrate that the proposed algorithm possesses the better performance of low computational complexity, high resolution and better accuracy of self-calibration.
2006, 28(5): 915-918.
Abstract:
To reduce the loss of sampling, higher sampling frequency than bandwidth of chirp must be adopted for Modulated Frequency Stepped Pulse(MFSP) radar signal, which will bring on over-sampling result of pulse compression for chirp. So the pick-up algorithm for the MFSP radar signal must be adopted to eliminate targets redundancy in order to obtain fine HRRP(High-Resolution Range Profile). However, because of inaccuracy of the velocity compensation method, the velocity error of the moving target will produce velocity-range coupling error, even bring the influence of losing target or producing spurious peaks on the HRRP. This paper proposes a targets redundancy removed algorithm based on the offset of the most powerful scatterer, which can solve the velocity-range coupling problem effectively by modifying the pick-up scopes of all sampled points. Finally, the processing results of both simulated data and real radar data validate the correctness of theoretical analysis.
To reduce the loss of sampling, higher sampling frequency than bandwidth of chirp must be adopted for Modulated Frequency Stepped Pulse(MFSP) radar signal, which will bring on over-sampling result of pulse compression for chirp. So the pick-up algorithm for the MFSP radar signal must be adopted to eliminate targets redundancy in order to obtain fine HRRP(High-Resolution Range Profile). However, because of inaccuracy of the velocity compensation method, the velocity error of the moving target will produce velocity-range coupling error, even bring the influence of losing target or producing spurious peaks on the HRRP. This paper proposes a targets redundancy removed algorithm based on the offset of the most powerful scatterer, which can solve the velocity-range coupling problem effectively by modifying the pick-up scopes of all sampled points. Finally, the processing results of both simulated data and real radar data validate the correctness of theoretical analysis.
2006, 28(5): 919-922.
Abstract:
The advantages of wavelet transform constructed with lifting scheme are introduced and compression algorithm based on lifting wavelet for SAR raw data is proposed. Compression performance of the algorithm is analyzed with simulation and real raw data and compared with other techniques by different quality parameters, which show that the algorithm is suitable for compression of SAR raw data.
The advantages of wavelet transform constructed with lifting scheme are introduced and compression algorithm based on lifting wavelet for SAR raw data is proposed. Compression performance of the algorithm is analyzed with simulation and real raw data and compared with other techniques by different quality parameters, which show that the algorithm is suitable for compression of SAR raw data.
2006, 28(5): 923-926.
Abstract:
The effect of the range migration to the Shift-And-Correlate Monopulse Secondary Surbeillause Redar (SAC) algorithm is analyzed in this paper. The conclusion is that the precision of SAC would be severely affected by the range migration in the high resolution SAR. Integrated with the range Doppler algorithm, a new SAC autofocus algorithm based on the limits of range bin is presented, which called Shift-And-Correlate within Gate Strategy (SACGS). The effect of the range migration is minished by SACGS. And the precision is increased. The efficiency of SACGS is proved by the simulation and actual SAR data. It can satisfy the request of the high resolution. And the computation is very simple, which make it very suitable for real-time image processing.
The effect of the range migration to the Shift-And-Correlate Monopulse Secondary Surbeillause Redar (SAC) algorithm is analyzed in this paper. The conclusion is that the precision of SAC would be severely affected by the range migration in the high resolution SAR. Integrated with the range Doppler algorithm, a new SAC autofocus algorithm based on the limits of range bin is presented, which called Shift-And-Correlate within Gate Strategy (SACGS). The effect of the range migration is minished by SACGS. And the precision is increased. The efficiency of SACGS is proved by the simulation and actual SAR data. It can satisfy the request of the high resolution. And the computation is very simple, which make it very suitable for real-time image processing.
2006, 28(5): 927-931.
Abstract:
The SAR working mode of range multi-aperture is a high resolution imaging mode for wide swath. Resolving and imaging are the two parts of range multi-aperture imaging algorithm. How to match the two parts together is the key problem for the algorithm. This paper presents a new method based on SCFT (SCaled FT) to solve the problem. Simulation and comparison between different methods is also given to prove the feasibility of range multi-aperture SAR imaging method based on SCFT.
The SAR working mode of range multi-aperture is a high resolution imaging mode for wide swath. Resolving and imaging are the two parts of range multi-aperture imaging algorithm. How to match the two parts together is the key problem for the algorithm. This paper presents a new method based on SCFT (SCaled FT) to solve the problem. Simulation and comparison between different methods is also given to prove the feasibility of range multi-aperture SAR imaging method based on SCFT.
2006, 28(5): 932-935.
Abstract:
The multiplicative nature of the speckle noise in SAR images is a big problem in SAR image segmentation. A novel method for automatic segmentation of SAR images is proposed. The wavelet energy is used to extract texture features, the regional statistics is used to extract gray-level features and the edge preserving mean of gray-level features is used to ensure the accuracy of classification of pixels near to the edge. Three representative kinds of features of SAR image are extracted, so the segmentation performance is enhanced. Besides, an improved unsupervised clustering algorithm is proposed for image segmentation, which can determine the number of classes automatically. Segmentation results on real SAR image demonstrate the effectiveness of the proposed method.
The multiplicative nature of the speckle noise in SAR images is a big problem in SAR image segmentation. A novel method for automatic segmentation of SAR images is proposed. The wavelet energy is used to extract texture features, the regional statistics is used to extract gray-level features and the edge preserving mean of gray-level features is used to ensure the accuracy of classification of pixels near to the edge. Three representative kinds of features of SAR image are extracted, so the segmentation performance is enhanced. Besides, an improved unsupervised clustering algorithm is proposed for image segmentation, which can determine the number of classes automatically. Segmentation results on real SAR image demonstrate the effectiveness of the proposed method.
2006, 28(5): 936-940.
Abstract:
Based on the analysis of the algorithms for implementing Multistage Wiener Filter (MWF), the MWF implemented by the Correlation Subtraction Algorithm (CSA) is proved to be an Unitary MWF (UMWF). The rank reduction performance of UMWF is superior to the original MWF proposed by Goldstein, Reed, and Scharf. In this paper, the block matrixes in the CSA are modified to reduce the size of the observation data vectors step by step in the forward recursion of MWF. The modified block matrixes can also be used in the CSA architecture. The new implementing algorithm needs a lower computation complexity, while keeping almost the same performance as the CSA. The validity of the proposed algorithm is proved by the simulation results.
Based on the analysis of the algorithms for implementing Multistage Wiener Filter (MWF), the MWF implemented by the Correlation Subtraction Algorithm (CSA) is proved to be an Unitary MWF (UMWF). The rank reduction performance of UMWF is superior to the original MWF proposed by Goldstein, Reed, and Scharf. In this paper, the block matrixes in the CSA are modified to reduce the size of the observation data vectors step by step in the forward recursion of MWF. The modified block matrixes can also be used in the CSA architecture. The new implementing algorithm needs a lower computation complexity, while keeping almost the same performance as the CSA. The validity of the proposed algorithm is proved by the simulation results.
2006, 28(5): 941-944.
Abstract:
An error model of transmitting array mutual coupling, gain and phase error of the synthetic transmitted beam bistatic HF-Surface Wave Radar (HF-SWR) is investigated in this paper. According to the characteristics of the error model, a transmitting array calibration method is proposed. This method employs the direct signal between receiving antenna and transmitting antenna as calibration sources, and utilizes an iterative Least Square (LS) algorithm to estimate the errors of transmitting array. Simulation results validate the effectiveness of this method.
An error model of transmitting array mutual coupling, gain and phase error of the synthetic transmitted beam bistatic HF-Surface Wave Radar (HF-SWR) is investigated in this paper. According to the characteristics of the error model, a transmitting array calibration method is proposed. This method employs the direct signal between receiving antenna and transmitting antenna as calibration sources, and utilizes an iterative Least Square (LS) algorithm to estimate the errors of transmitting array. Simulation results validate the effectiveness of this method.
2006, 28(5): 945-949.
Abstract:
In this paper, geometric accuracy of the airborne high resolution SAR developed by Institute of Electronics, Chinese Academy of Sciences (IECAS) is verified with real terrain map data by using classical radar photogrammetry.The experimental results show that horizontal positional accuracy of single imagery revision is better than 4m and spatial positional accuracy of stereo images measurement is better than 20m for the kind of radar imagery.
In this paper, geometric accuracy of the airborne high resolution SAR developed by Institute of Electronics, Chinese Academy of Sciences (IECAS) is verified with real terrain map data by using classical radar photogrammetry.The experimental results show that horizontal positional accuracy of single imagery revision is better than 4m and spatial positional accuracy of stereo images measurement is better than 20m for the kind of radar imagery.
2006, 28(5): 950-954.
Abstract:
In this paper, an accurate and efficient implementation approach of the Method of Moments (MOM) is developed to compute scattering from 3-D targets in the subsurface, which is based on the Mixed Potential Integral Equation (MPIE) in layered media and the RWG basis function. The implementation skill and computing performance of the proposed approach are studied in detail. In particular, how to efficiently calculate various different Sommerfeld integrals (SIs) is numerically investigated with the discrete complex images technique. The computed results of the targets in free space are in agreement with Mie Series results and the computed results of subsurface flat are also in agreement with the published data, which shows the reliability, efficiency and accuracy of the developed approach. Furthermore, the EM scattering of other shaped targets is computed at different size, buried depth, and subsurface medium.
In this paper, an accurate and efficient implementation approach of the Method of Moments (MOM) is developed to compute scattering from 3-D targets in the subsurface, which is based on the Mixed Potential Integral Equation (MPIE) in layered media and the RWG basis function. The implementation skill and computing performance of the proposed approach are studied in detail. In particular, how to efficiently calculate various different Sommerfeld integrals (SIs) is numerically investigated with the discrete complex images technique. The computed results of the targets in free space are in agreement with Mie Series results and the computed results of subsurface flat are also in agreement with the published data, which shows the reliability, efficiency and accuracy of the developed approach. Furthermore, the EM scattering of other shaped targets is computed at different size, buried depth, and subsurface medium.
2006, 28(5): 955-960.
Abstract:
The diversified researches of capacity of digital watermarking are summarized in this paper. The capacity of watermarking as a basic communication system, the capacity as side information, the capacity using dirty paper encoding and the capacity of security watermarking are introduced. An effective conclusion for designing the arithmetic of embedding and detecting is found by analysis the capacity.
The diversified researches of capacity of digital watermarking are summarized in this paper. The capacity of watermarking as a basic communication system, the capacity as side information, the capacity using dirty paper encoding and the capacity of security watermarking are introduced. An effective conclusion for designing the arithmetic of embedding and detecting is found by analysis the capacity.
