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2009 Vol. 31, No. 10
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2009, 31(10): 2287-2293.
doi: 10.3724/SP.J.1146.2008.01538
Abstract:
Media synchronization puts forward determinate requirements on end-to-end delay and delay jitter. The jitter buffers at the destination site can eliminate the effect of the delay jitter but increase the end-to-end delay. Then, the requirements of media synchronization guarantee on the network delay are not clear. From the point of view of statistical guarantee, this paper determines the range of the jitter buffer size for guaranteeing media synchronization, provides the sufficient condition for the network to guarantee the media synchronization, presents an synchronization guarantee evaluating examples with the sufficient condition and validates the sufficient condition by the actual network testing results on VoIP(Voice over IP) based on Internet.
Media synchronization puts forward determinate requirements on end-to-end delay and delay jitter. The jitter buffers at the destination site can eliminate the effect of the delay jitter but increase the end-to-end delay. Then, the requirements of media synchronization guarantee on the network delay are not clear. From the point of view of statistical guarantee, this paper determines the range of the jitter buffer size for guaranteeing media synchronization, provides the sufficient condition for the network to guarantee the media synchronization, presents an synchronization guarantee evaluating examples with the sufficient condition and validates the sufficient condition by the actual network testing results on VoIP(Voice over IP) based on Internet.
2009, 31(10): 2294-2298.
doi: 10.3724/SP.J.1146.2008.01439
Abstract:
Reliability and stability are essential to Media-on-Demand (MoD) system. Based on the node reliability and QoS assessment, a Peer-to-peer MoD architecture (RP2MoD) is proposed in this paper. In the proposed system, the reliable degree of each client is calculated based on the failure probability of its parents, and the QoS level of its parents is also assessed. The reliability degree and QoS level are the basis of MoD operations, such as the parent selection, the allocation strategy of the requested media data and the error resilience. Analytical and experimental results about the system performance show that the operations relative to the reliability degree and QoS level have little effect on the performance of the proposed system and result in a strong ability of fault tolerance. Thus the system can provide large-scale, steady and reliable MoD service in Internet.
Reliability and stability are essential to Media-on-Demand (MoD) system. Based on the node reliability and QoS assessment, a Peer-to-peer MoD architecture (RP2MoD) is proposed in this paper. In the proposed system, the reliable degree of each client is calculated based on the failure probability of its parents, and the QoS level of its parents is also assessed. The reliability degree and QoS level are the basis of MoD operations, such as the parent selection, the allocation strategy of the requested media data and the error resilience. Analytical and experimental results about the system performance show that the operations relative to the reliability degree and QoS level have little effect on the performance of the proposed system and result in a strong ability of fault tolerance. Thus the system can provide large-scale, steady and reliable MoD service in Internet.
2009, 31(10): 2299-2304.
doi: 10.3724/SP.J.1146.2008.01291
Abstract:
The current practical scheduling algorithms supporting unicast and multicast traffic in high-speed crossbars are generally based on a request-grant-accept process, such as ESLIP. But there is a phenomenon called Grant blocking between unicast and multicast cells in this kind of algorithms, which decreases the scheduling efficiency. According to the practicability, this paper presents a new algorithm supporting unicast and multicast trafficERGRR (Extended Request-Grant-based Round-Robin). ERGRR overcomes the Grant blocking and improves the system performance, such as throughput and delay, by simplifying execution process. The simulation results show that the ERGRR can achieve better performance of throughput and delay than ESLIP under various unicast and multicast traffics. In addition, ERGRR provides better fairness and its implementation complexity is lower than ESLIP.
The current practical scheduling algorithms supporting unicast and multicast traffic in high-speed crossbars are generally based on a request-grant-accept process, such as ESLIP. But there is a phenomenon called Grant blocking between unicast and multicast cells in this kind of algorithms, which decreases the scheduling efficiency. According to the practicability, this paper presents a new algorithm supporting unicast and multicast trafficERGRR (Extended Request-Grant-based Round-Robin). ERGRR overcomes the Grant blocking and improves the system performance, such as throughput and delay, by simplifying execution process. The simulation results show that the ERGRR can achieve better performance of throughput and delay than ESLIP under various unicast and multicast traffics. In addition, ERGRR provides better fairness and its implementation complexity is lower than ESLIP.
2009, 31(10): 2305-2309.
doi: 10.3724/SP.J.1146.2008.00945
Abstract:
Sensing range is the maximum range within which a sensor node can detect a target. This paper proposes an energy-efficient scheme for area coverage in wireless sensor networks with adjustable sensing ranges. The scheme assigns reasonable sensing ranges to the network of nodes to minimize the energy consumption and meanwhile meet the coverage requirement. Firstly, the coverage capability and energy consumption are formulated as functions of node sensing ranges; Then, the area coverage issue is formulated as a constrained optimal model; Finally, a area-divided-based method is developed to solve the problem. Simulated results show that, compared with traditional method, the proposed scheme can efficiently save energy with satisfactory area coverage.
Sensing range is the maximum range within which a sensor node can detect a target. This paper proposes an energy-efficient scheme for area coverage in wireless sensor networks with adjustable sensing ranges. The scheme assigns reasonable sensing ranges to the network of nodes to minimize the energy consumption and meanwhile meet the coverage requirement. Firstly, the coverage capability and energy consumption are formulated as functions of node sensing ranges; Then, the area coverage issue is formulated as a constrained optimal model; Finally, a area-divided-based method is developed to solve the problem. Simulated results show that, compared with traditional method, the proposed scheme can efficiently save energy with satisfactory area coverage.
2009, 31(10): 2310-2315.
doi: 10.3724/SP.J.1146.2008.00877
Abstract:
In this paper, a distributed intrusion detection approach is proposed based on timed automata. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then the timed automata is constructed by the way of manually abstracting the correct behaviours of the node according to the routing protocol of Dynamic Source Routing (DSR). The monitor nodes can verify every nodes behaviour by timed automata, and validly detect real-time attacks without signatures of intrusion or trained data. Compared with the architecture where each node is its own IDS agent, our approach is much more efficient while maintaining the same level of effectiveness. Finally, the intrusion detection method is evaluated through simulation experiments.
In this paper, a distributed intrusion detection approach is proposed based on timed automata. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then the timed automata is constructed by the way of manually abstracting the correct behaviours of the node according to the routing protocol of Dynamic Source Routing (DSR). The monitor nodes can verify every nodes behaviour by timed automata, and validly detect real-time attacks without signatures of intrusion or trained data. Compared with the architecture where each node is its own IDS agent, our approach is much more efficient while maintaining the same level of effectiveness. Finally, the intrusion detection method is evaluated through simulation experiments.
2009, 31(10): 2316-2320.
doi: 10.3724/SP.J.1146.2008.01343
Abstract:
The key management schemes bsaed on Distributed Certificate Authority resolve the difficulty to adopting concentrating key management in space networks, but result in some new threats of authenticated key. Based on discribing and analyzing the threats suffered by authenticated key of space networks, a measurement method for security intensity of authenticated key is proposed. The method can quantitatively measure the security intensity of authenticated key according to the setting of parameters, such as threshold value, key-update period etc. By analyzing the impact of threshold value and key-update period on authenticated key security, a method of setting the two networks security parameters reasonably is given.
The key management schemes bsaed on Distributed Certificate Authority resolve the difficulty to adopting concentrating key management in space networks, but result in some new threats of authenticated key. Based on discribing and analyzing the threats suffered by authenticated key of space networks, a measurement method for security intensity of authenticated key is proposed. The method can quantitatively measure the security intensity of authenticated key according to the setting of parameters, such as threshold value, key-update period etc. By analyzing the impact of threshold value and key-update period on authenticated key security, a method of setting the two networks security parameters reasonably is given.
2009, 31(10): 2321-2325.
doi: 10.3724/SP.J.1146.2008.01326
Abstract:
The existing periodic broadcasting schemes mainly support CBR-encoded videos. A modification of recursive frequency-splitting (RFS) scheme, called v-RFS, is presented in this paper to support VBR-encoded videos. In v-RFS, the maximum number and the placement of segments are determined by using the RFS. Then the VBR video is partitioned into a series of segments with equal-length, and these segments are further partitioned into multiple equal-size sub-segments. Finally sub-segments of different segments are multiplexed and transmitted periodically on their channels. The proposed scheme can deliver all segments on time at constant transmission rate. Simulation results indicated that the proposed scheme outperforms RFS and Smooth RFS in improving bandwidth efficiency and reducing client storage.
The existing periodic broadcasting schemes mainly support CBR-encoded videos. A modification of recursive frequency-splitting (RFS) scheme, called v-RFS, is presented in this paper to support VBR-encoded videos. In v-RFS, the maximum number and the placement of segments are determined by using the RFS. Then the VBR video is partitioned into a series of segments with equal-length, and these segments are further partitioned into multiple equal-size sub-segments. Finally sub-segments of different segments are multiplexed and transmitted periodically on their channels. The proposed scheme can deliver all segments on time at constant transmission rate. Simulation results indicated that the proposed scheme outperforms RFS and Smooth RFS in improving bandwidth efficiency and reducing client storage.
2009, 31(10): 2326-2331.
doi: 10.3724/SP.J.1146.2009.00114
Abstract:
A novel cooperative Hybrid-ARQ protocol is presented on the basis of network coding. Two users communicate with the base station with the assistance of a relay node. Relay node responds the repeat request and processes two users incremental redundancy frames with physical-layer network coding, i.e. signal superposition modulation, before transmitting to the base station. Multi-user joint detection and joint soft decision decoding are adopted at the base station. Compared with traditional Hybrid-ARQ protocol, the proposed cooperative Hybrid-ARQ protocol can achieve better performance on flat Rayleigh fading channel, and approximates the performance of cooperative Hybrid-ARQ protocol without network coding with fewer hardware and bandwidth resources.
A novel cooperative Hybrid-ARQ protocol is presented on the basis of network coding. Two users communicate with the base station with the assistance of a relay node. Relay node responds the repeat request and processes two users incremental redundancy frames with physical-layer network coding, i.e. signal superposition modulation, before transmitting to the base station. Multi-user joint detection and joint soft decision decoding are adopted at the base station. Compared with traditional Hybrid-ARQ protocol, the proposed cooperative Hybrid-ARQ protocol can achieve better performance on flat Rayleigh fading channel, and approximates the performance of cooperative Hybrid-ARQ protocol without network coding with fewer hardware and bandwidth resources.
2009, 31(10): 2332-2337.
doi: 10.3724/SP.J.1146.2008.01398
Abstract:
Compared with OFDM system with Cyclic Prefix (CP-OFDM) which satisfies strictly complex field orthogonality, OFDM/Offset QAM system (OFDM/OQAM) only satisfies the real field orthogonality. Therefore, in present of multipath fading channel, the Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI) always exist in the OFDM/OQAM system if utilizing the conventional preamble based channel estimation method for CP-OFDM system. In this paper, a joint iterative channel estimation and detection is proposed for OFDM/OQAM system. The proposed method exchanges the information between channel estimator and demodulator to remove the ISI and ICI effectively. Simulation results demonstrate that as the number of iterative time increasing, BER performance of the joint iterative channel estimation and detection method is approximately close to perfect channel estimation.
Compared with OFDM system with Cyclic Prefix (CP-OFDM) which satisfies strictly complex field orthogonality, OFDM/Offset QAM system (OFDM/OQAM) only satisfies the real field orthogonality. Therefore, in present of multipath fading channel, the Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI) always exist in the OFDM/OQAM system if utilizing the conventional preamble based channel estimation method for CP-OFDM system. In this paper, a joint iterative channel estimation and detection is proposed for OFDM/OQAM system. The proposed method exchanges the information between channel estimator and demodulator to remove the ISI and ICI effectively. Simulation results demonstrate that as the number of iterative time increasing, BER performance of the joint iterative channel estimation and detection method is approximately close to perfect channel estimation.
2009, 31(10): 2338-2342.
doi: 10.3724/SP.J.1146.2008.01391
Abstract:
Being different from previous spectrum sensing research for single-antenna cognitive users, a spectrum sensing algorithm based on optimal power allocation and cooperative diversity under multi-antenna scenario is proposed. It used Sigular Value Decomposition(SVD) to implement power water-filling on each antenna based on channel condition, and the detection process of the cooperative spectrum sensing for the primary user is considered in the two-user network with multi-antenna. The ergodic capacity, detection probability and detection time in cognitive network with multi-antenna are analyzed with path-loss model based on exponential attenuation. Theory analysis and simulation results show that cognitive users with multi-antenna can not only make the cognitive network have maximal ergodic capacity, but also improve detection performance of the system through optimal power allocation and cooperative spectrum sensing.
Being different from previous spectrum sensing research for single-antenna cognitive users, a spectrum sensing algorithm based on optimal power allocation and cooperative diversity under multi-antenna scenario is proposed. It used Sigular Value Decomposition(SVD) to implement power water-filling on each antenna based on channel condition, and the detection process of the cooperative spectrum sensing for the primary user is considered in the two-user network with multi-antenna. The ergodic capacity, detection probability and detection time in cognitive network with multi-antenna are analyzed with path-loss model based on exponential attenuation. Theory analysis and simulation results show that cognitive users with multi-antenna can not only make the cognitive network have maximal ergodic capacity, but also improve detection performance of the system through optimal power allocation and cooperative spectrum sensing.
2009, 31(10): 2343-2347.
doi: 10.3724/SP.J.1146.2008.01504
Abstract:
This paper proposes a new limited feedback approach based on tree-structure codebook. As the temporally-correlation across adjacent frames, the quantized channel vector codeword can be modeled as a first-order finite-state Markov chain. The channel vector of current frame is quantized into son-codeword of the codeword with the most transition probabilities corresponding to the previous frame. The index of the son-codeword is fed back to the transmitter with 1 bit feedback. The link simulation results show that, the proposed approach can significantly improve the BER performance relative to the common approach, and the feedback rate can be reduced under some conditions.
This paper proposes a new limited feedback approach based on tree-structure codebook. As the temporally-correlation across adjacent frames, the quantized channel vector codeword can be modeled as a first-order finite-state Markov chain. The channel vector of current frame is quantized into son-codeword of the codeword with the most transition probabilities corresponding to the previous frame. The index of the son-codeword is fed back to the transmitter with 1 bit feedback. The link simulation results show that, the proposed approach can significantly improve the BER performance relative to the common approach, and the feedback rate can be reduced under some conditions.
2009, 31(10): 2348-2353.
doi: 10.3724/SP.J.1146.2008.00525
Abstract:
A cooperative communication and wireless relay techniques based convergence mechanism for the heterogeneous wireless communication system is presented to fulfill the functionalities of convergence and interworking. In order to maximize the capacity of the proposed heterogeneous cooperative network, the utility function based cooperative power allocation strategy is proposed. This paper gives the theoretical optimum model for the power allocation, and presents the detailed cooperative power allocation algorithm different from the conventional water-filling algorithm, in which the global optimization is guaranteed under the conditions of equivalent transmission rates between the first and second hops. The simulation results demonstrate that the proposed cooperative power allocation algorithm has a significant performance gain.
A cooperative communication and wireless relay techniques based convergence mechanism for the heterogeneous wireless communication system is presented to fulfill the functionalities of convergence and interworking. In order to maximize the capacity of the proposed heterogeneous cooperative network, the utility function based cooperative power allocation strategy is proposed. This paper gives the theoretical optimum model for the power allocation, and presents the detailed cooperative power allocation algorithm different from the conventional water-filling algorithm, in which the global optimization is guaranteed under the conditions of equivalent transmission rates between the first and second hops. The simulation results demonstrate that the proposed cooperative power allocation algorithm has a significant performance gain.
2009, 31(10): 2354-2358.
doi: 10.3724/SP.J.1146.2008.01388
Abstract:
A construction scheme of sequences with good properties for multi-carrier code division multiple access communication systems is presented. The proposed method is based on sequences with Zero Correlation Zone (ZCZ), and a novel kind of sequences with complementary mode and multiple subsets can be obtained by interleaving these ZCZ sequences. The designed sequences have periodic complementary characteristics, which leads to stronger ability to resist multi-path interference and multiple access interference. This paper proves the periodic correlation properties of the constructed sequences, and the construction example shows that the proposed method combines effectively complementary characteristics and ZCZ characteristics.
A construction scheme of sequences with good properties for multi-carrier code division multiple access communication systems is presented. The proposed method is based on sequences with Zero Correlation Zone (ZCZ), and a novel kind of sequences with complementary mode and multiple subsets can be obtained by interleaving these ZCZ sequences. The designed sequences have periodic complementary characteristics, which leads to stronger ability to resist multi-path interference and multiple access interference. This paper proves the periodic correlation properties of the constructed sequences, and the construction example shows that the proposed method combines effectively complementary characteristics and ZCZ characteristics.
Proportional Fairness Algorithm for Multiuser MIMO-OFDM Systems Based on the Application Time Window
2009, 31(10): 2359-2363.
doi: 10.3724/SP.J.1146.2008.01264
Abstract:
A novel proportional fairness algorithm based on the application time window for multiuser MIMO- OFDM systems with delay channel state information is presented in this paper. With the goal of maximizing overall data throughput in a finite time window W subject to user proportional rate constraints and user power constraints the algorithm of resource allocation is proposed. This algorithm firstly designs constellation distance which meets users bit error rate. Then it maps every user into the corresponding virtual users according to the proportion. Finally in accordance with the shadow price of optimization theory it optimally allocates subcarrier to virtual users. The simulation results show the algorithm can improve total throughput efficiently under the condition of guaranteeing the proportional fairness of users.
A novel proportional fairness algorithm based on the application time window for multiuser MIMO- OFDM systems with delay channel state information is presented in this paper. With the goal of maximizing overall data throughput in a finite time window W subject to user proportional rate constraints and user power constraints the algorithm of resource allocation is proposed. This algorithm firstly designs constellation distance which meets users bit error rate. Then it maps every user into the corresponding virtual users according to the proportion. Finally in accordance with the shadow price of optimization theory it optimally allocates subcarrier to virtual users. The simulation results show the algorithm can improve total throughput efficiently under the condition of guaranteeing the proportional fairness of users.
2009, 31(10): 2364-2368.
doi: 10.3724/SP.J.1146.2008.01443
Abstract:
In this paper, An analysis method of effects of frequency offset on the property of pulse shaping multicarrier system is presented. The method first divides demodulator output into signals and interference, and then based on the cross-ambiguity function of transmit pulse and receive pulse, obtaines the quantitative analysis of signal and interference, finally calculates the SIR with the utilization of statistical properties of the transmit data. Simulation results show that BER caused by frequency synchronization error is consistent with theoretical calculation of the SIR. Therefore, the reliability of the method is verified.
In this paper, An analysis method of effects of frequency offset on the property of pulse shaping multicarrier system is presented. The method first divides demodulator output into signals and interference, and then based on the cross-ambiguity function of transmit pulse and receive pulse, obtaines the quantitative analysis of signal and interference, finally calculates the SIR with the utilization of statistical properties of the transmit data. Simulation results show that BER caused by frequency synchronization error is consistent with theoretical calculation of the SIR. Therefore, the reliability of the method is verified.
2009, 31(10): 2369-2373.
doi: 10.3724/SP.J.1146.2008.01312
Abstract:
A new conic fitting code discriminator is proposed for the traditional discriminator gain decreasing in bandwidth-limited environment. According to the correlation property, conic fitting code discriminator gets the conic equation with the early and late integration-dumping results. The code phase estimate can be calculated by solving equation. Simulation results show that the conic fitting code discriminator is not influenced by bandwidth and it has better discriminate performance than traditional discriminator when the system bandwidth is limited.
A new conic fitting code discriminator is proposed for the traditional discriminator gain decreasing in bandwidth-limited environment. According to the correlation property, conic fitting code discriminator gets the conic equation with the early and late integration-dumping results. The code phase estimate can be calculated by solving equation. Simulation results show that the conic fitting code discriminator is not influenced by bandwidth and it has better discriminate performance than traditional discriminator when the system bandwidth is limited.
2009, 31(10): 2374-2377.
doi: 10.3724/SP.J.1146.2008.01475
Abstract:
Adaptive equalization is an effective way to cope with intersymbol interference caused by multipath propagation in underwater acoustic coherent communication. An experiment is carried out to verify the coherent underwater acoustic communication technique and to study the performance of adaptive equalization algorithm promoted by the author. Data processing results show that there is poor performance at Ts/2 fractionally spaced equalization and by using Ts/4 spaced equalization the data is without error. This algorithm has better performance compared with conventional equalization algorithms because it has robust convergence performance for its adaptive stepsize behavior and has low computational load.
Adaptive equalization is an effective way to cope with intersymbol interference caused by multipath propagation in underwater acoustic coherent communication. An experiment is carried out to verify the coherent underwater acoustic communication technique and to study the performance of adaptive equalization algorithm promoted by the author. Data processing results show that there is poor performance at Ts/2 fractionally spaced equalization and by using Ts/4 spaced equalization the data is without error. This algorithm has better performance compared with conventional equalization algorithms because it has robust convergence performance for its adaptive stepsize behavior and has low computational load.
2009, 31(10): 2378-2384.
doi: 10.3724/SP.J.1146.2008.00634
Abstract:
MF-TDMA has been widely applied to the up-link of broadband communication satellites, and the timeslot allocation strategy is the key to guarantee the efficient utilization of the system resources. In this paper, the timeslot allocation technology with dynamic channel selection is proposed to confront the difficulty of complex allocation process and the low utilization rate. This allocation issue can be divided into two steps: channel select and in-channel slot allocation. To achieve the channel selection, RCP-A algorithm is proposed to provide better support to multi-users with multi-service and higher resource utilization ratio. To address the in-channel slot management, an inverse-numbering slots tree is selected as the management model to solve the problem of delay jitter brought by the slot allocation. Finally, a detailed management realization on satellite is given at last part, and the simulation shows that the allocation algorithm is of high efficiency in the management of timeslot resources and this method can be utilized in RRM (Radio Resource Management) on satellite.
MF-TDMA has been widely applied to the up-link of broadband communication satellites, and the timeslot allocation strategy is the key to guarantee the efficient utilization of the system resources. In this paper, the timeslot allocation technology with dynamic channel selection is proposed to confront the difficulty of complex allocation process and the low utilization rate. This allocation issue can be divided into two steps: channel select and in-channel slot allocation. To achieve the channel selection, RCP-A algorithm is proposed to provide better support to multi-users with multi-service and higher resource utilization ratio. To address the in-channel slot management, an inverse-numbering slots tree is selected as the management model to solve the problem of delay jitter brought by the slot allocation. Finally, a detailed management realization on satellite is given at last part, and the simulation shows that the allocation algorithm is of high efficiency in the management of timeslot resources and this method can be utilized in RRM (Radio Resource Management) on satellite.
2009, 31(10): 2385-2391.
doi: 10.3724/SP.J.1146.2008.01411
Abstract:
Aiming at access security aspect of 3G-WLAN heterogeneous wireless network, this paper abstracts each entities of heterogeneous wireless network, thereby establishes a general authentication model. Then based on this general authentication model, a novel access authentication and key agreement scheme by using Canetti-Krawczyk (CK) model is devised. This scheme simplifies the authentication process and information between access network server and home network server by using Public Key Infrastructure (PKI) to distribute public key. It also decreases the authentication computational complexity of mobile terminal by Elliptic Curves Cryptography (ECC). Finally, formal analysis and proof with CK model for the proposed protocol are given. It is showed that the proposed scheme is secure and efficient.
Aiming at access security aspect of 3G-WLAN heterogeneous wireless network, this paper abstracts each entities of heterogeneous wireless network, thereby establishes a general authentication model. Then based on this general authentication model, a novel access authentication and key agreement scheme by using Canetti-Krawczyk (CK) model is devised. This scheme simplifies the authentication process and information between access network server and home network server by using Public Key Infrastructure (PKI) to distribute public key. It also decreases the authentication computational complexity of mobile terminal by Elliptic Curves Cryptography (ECC). Finally, formal analysis and proof with CK model for the proposed protocol are given. It is showed that the proposed scheme is secure and efficient.
2009, 31(10): 2392-2396.
doi: 10.3724/SP.J.1146.2008.01178
Abstract:
Ring signature is a new kind of anonymous signature which can provide unconditional anonymity of the signer. Proxy ring signature is the combination of proxy signature and ring signature. Previous proxy ring signature schemes are constructed based on the idea of ring signature to provide the privacy protection for the proxy signer while the identity of the original signer is public. A new proxy ring signature scheme based on the difficulty of RSA problem is proposed in this paper, which can provide the privacy protection for both the proxy signer and the original signer. It proves that the proposed scheme can resist the adaptive chosen-message attack in the random oracle model.
Ring signature is a new kind of anonymous signature which can provide unconditional anonymity of the signer. Proxy ring signature is the combination of proxy signature and ring signature. Previous proxy ring signature schemes are constructed based on the idea of ring signature to provide the privacy protection for the proxy signer while the identity of the original signer is public. A new proxy ring signature scheme based on the difficulty of RSA problem is proposed in this paper, which can provide the privacy protection for both the proxy signer and the original signer. It proves that the proposed scheme can resist the adaptive chosen-message attack in the random oracle model.
2009, 31(10): 2397-2401.
doi: 10.3724/SP.J.1146.2008.01307
Abstract:
This paper proves that the noise functions produced by six kinds of macrocosm approximations of exclusive or with addition modulo 2n have the same probability distribution values. Then, the relations between the six noise functions are given. Moreover, this paper presents the computing formulas for the probability distributions and the square sums of the probability values, and proposes a correct formula for the square sums of the probability values of noise function produced by macrocosm approximations of addition modulo 2n with exclusive or. The results presented in this paper are useful in some distinguishing attacks.
This paper proves that the noise functions produced by six kinds of macrocosm approximations of exclusive or with addition modulo 2n have the same probability distribution values. Then, the relations between the six noise functions are given. Moreover, this paper presents the computing formulas for the probability distributions and the square sums of the probability values, and proposes a correct formula for the square sums of the probability values of noise function produced by macrocosm approximations of addition modulo 2n with exclusive or. The results presented in this paper are useful in some distinguishing attacks.
2009, 31(10): 2402-2405.
doi: 10.3724/SP.J.1146.2008.01410
Abstract:
In this paper, based on output linearization feedback control,the nonlinear function of the chaotic system is linearized, then the complex synchronization of the nonlinear chaotic system is converted into the stable problem of the linearization system. Then a nonlinear controller is given by pole assignment. Furthermore based on the scheme above, a system of secure communication is proposed. One channel of the system is output of the chaotic transmitter, the other one transmits the information-bearing signal. Finally a numerical example is used to show the effectiveness of the proposed technique.
In this paper, based on output linearization feedback control,the nonlinear function of the chaotic system is linearized, then the complex synchronization of the nonlinear chaotic system is converted into the stable problem of the linearization system. Then a nonlinear controller is given by pole assignment. Furthermore based on the scheme above, a system of secure communication is proposed. One channel of the system is output of the chaotic transmitter, the other one transmits the information-bearing signal. Finally a numerical example is used to show the effectiveness of the proposed technique.
2009, 31(10): 2406-2410.
doi: 10.3724/SP.J.1146.2008.01339
Abstract:
Whether the algorithm noise can be effectively wiped off decides the success or loss of the power analysis attack. This paper offers a new differential power analysis attack algorithm, which is based on the consumed power differences between two neighboring clock cycles of liner feedback shift register. This new attack algorithm radically wipes off the effect of cipher algorithm noise in the process of attack. Because this algorithm randomly chooses initialization vectors, the attackers can easily extend the algorithm to other stream ciphers that have similar structures. In order to further validate the algorithms availability, simulative attacks on DECIM are carried on with the method of software simulation. And the result shows that this algorithm can effectively reduce the complexity of the exhaustive search on LFSR.
Whether the algorithm noise can be effectively wiped off decides the success or loss of the power analysis attack. This paper offers a new differential power analysis attack algorithm, which is based on the consumed power differences between two neighboring clock cycles of liner feedback shift register. This new attack algorithm radically wipes off the effect of cipher algorithm noise in the process of attack. Because this algorithm randomly chooses initialization vectors, the attackers can easily extend the algorithm to other stream ciphers that have similar structures. In order to further validate the algorithms availability, simulative attacks on DECIM are carried on with the method of software simulation. And the result shows that this algorithm can effectively reduce the complexity of the exhaustive search on LFSR.
2009, 31(10): 2411-2415.
doi: 10.3724/SP.J.1146.2007.01521
Abstract:
For k-redundant multicast network, the maximum multicast rate can be achieved with network coding. The minimal finite field which is enough to implement network coding for different multicast rate in k-redundant multicast network is obtained, by using some results of MDS codes available. To design codes of multicast network and implement network coding, a generator matrix of a [n, k] MDS code is constructed based on the obtained minimal finite field, and its column vectors are allocated to output links of the source as their global coding vectors. An application instance shows that, compared with present universal approaches of network coding, this approach has lower computation complexity.
For k-redundant multicast network, the maximum multicast rate can be achieved with network coding. The minimal finite field which is enough to implement network coding for different multicast rate in k-redundant multicast network is obtained, by using some results of MDS codes available. To design codes of multicast network and implement network coding, a generator matrix of a [n, k] MDS code is constructed based on the obtained minimal finite field, and its column vectors are allocated to output links of the source as their global coding vectors. An application instance shows that, compared with present universal approaches of network coding, this approach has lower computation complexity.
2009, 31(10): 2416-2420.
doi: 10.3724/SP.J.1146.2008.01321
Abstract:
It is difficult to recovery carrier at rather low SNR (2 dB). An iterative carrier recovery via soft decision metrics of LDPC decoding is proposed. By maximizing the sum of the absolute value of the soft decision metrics of LDPC decoding with search window aided simplex algorithm, it can obtain accurate carrier estimate which will be compensated. Meanwhile, it can be combined with the Costas loop with LDPC decoding feedback to eliminate the residual carrier offsets. Simulation results indicate that it can overcome the problems of phase ambiguity, cycle slip and so on, and the performance of the QPSK system with it under carrier offsets is just within 0.1 dB of the ideal performance at the cost of some more computation complexity.
It is difficult to recovery carrier at rather low SNR (2 dB). An iterative carrier recovery via soft decision metrics of LDPC decoding is proposed. By maximizing the sum of the absolute value of the soft decision metrics of LDPC decoding with search window aided simplex algorithm, it can obtain accurate carrier estimate which will be compensated. Meanwhile, it can be combined with the Costas loop with LDPC decoding feedback to eliminate the residual carrier offsets. Simulation results indicate that it can overcome the problems of phase ambiguity, cycle slip and so on, and the performance of the QPSK system with it under carrier offsets is just within 0.1 dB of the ideal performance at the cost of some more computation complexity.
2009, 31(10): 2421-2426.
doi: 10.3724/SP.J.1146.2008.01243
Abstract:
BP (Belief Propagation) decoding based on reliability updating schedule reduces the computational complexity and improves the decoding efficiency. However, the poor Bit Error Rate (BER) performance of the decoding appears due to the low accuracy of reliability criteria and the wrong bits which are no longer update. Therefore, an improved reliability criteria and modified updating schedule are proposed to increase the accuracy of the criteria. The simulation results show that the proposed algorithm can reduce the computational complexity and improve the decoding performance of conventional BP algorithm.
BP (Belief Propagation) decoding based on reliability updating schedule reduces the computational complexity and improves the decoding efficiency. However, the poor Bit Error Rate (BER) performance of the decoding appears due to the low accuracy of reliability criteria and the wrong bits which are no longer update. Therefore, an improved reliability criteria and modified updating schedule are proposed to increase the accuracy of the criteria. The simulation results show that the proposed algorithm can reduce the computational complexity and improve the decoding performance of conventional BP algorithm.
2009, 31(10): 2427-2431.
doi: 10.3724/SP.J.1146.2008.00558
Abstract:
The iterative channel decoder of joint source-channel decode has the transform of log-likelihood and probability, also the multiplication and accumulation operation, which improves the computation complexity of channel decoder. In order to reduce the complexity, this paper proposes the simplified iterative channel decoding algorithm. The algorithm directly utilizes the hard decided value of channel decoder and parameter prior probability to estimate the extrinsic information for iterative channel decoder. Based on Gaussian-Markov source, simulation results show that the simplified iterative channel decoder significantly improves SNR of received parameters and reduces the computation compared with separation source channel decoder. Also, the simplified algorithm does not degrade the performance of joint source channel decoding algorithm obviously.
The iterative channel decoder of joint source-channel decode has the transform of log-likelihood and probability, also the multiplication and accumulation operation, which improves the computation complexity of channel decoder. In order to reduce the complexity, this paper proposes the simplified iterative channel decoding algorithm. The algorithm directly utilizes the hard decided value of channel decoder and parameter prior probability to estimate the extrinsic information for iterative channel decoder. Based on Gaussian-Markov source, simulation results show that the simplified iterative channel decoder significantly improves SNR of received parameters and reduces the computation compared with separation source channel decoder. Also, the simplified algorithm does not degrade the performance of joint source channel decoding algorithm obviously.
2009, 31(10): 2432-2437.
doi: 10.3724/SP.J.1146.2008.01295
Abstract:
The performance loss of conventional Grassmannian codebook is analyzed. According to the analysis of unitary perturbations effects on channel capacity as well as the BER, a novel hierarchical codebook consisting of a Grassmannian main-codebook and a perturbation subcodebook proposed for multi-antenna systems with linear receivers is established, and corresponds with the two-step codeword selection scheme that uses the product of two codewords respectively selected from the main-codebook and the sub one as the ultimate precoder. Specifically to the design of subcodebook, two schemes is brought forward: rotation-based and householder transformation-based, and the superiority of the proposed codebook in terms of both the channel capacity and BER is further confirmed by computer simulations.
The performance loss of conventional Grassmannian codebook is analyzed. According to the analysis of unitary perturbations effects on channel capacity as well as the BER, a novel hierarchical codebook consisting of a Grassmannian main-codebook and a perturbation subcodebook proposed for multi-antenna systems with linear receivers is established, and corresponds with the two-step codeword selection scheme that uses the product of two codewords respectively selected from the main-codebook and the sub one as the ultimate precoder. Specifically to the design of subcodebook, two schemes is brought forward: rotation-based and householder transformation-based, and the superiority of the proposed codebook in terms of both the channel capacity and BER is further confirmed by computer simulations.
2009, 31(10): 2438-2442.
doi: 10.3724/SP.J.1146.2008.01485
Abstract:
A new method is proposed in this paper to accomplish the carrier frequency estimation of non- cooperative underwater acoustic DSSS-BPSK signal. The carrier frequency estimated using the method is accurate even under low-CNR and signal distortion conditions. A rough estimation of the carrier frequency is first made through gravity method. With the concave point characteristic of the signal power spectrum envelope at the carrier frequency, a more precise carrier frequency is then estimated by searching the local minimum of the power spectrum envelope in the frequency neighborhood of the rough estimation. Monte Carlo simulations of the method are in accord with theoretical analysis. Results of oceanic experimental data test also verify the effectiveness feasibility and practicality of the method for its low complexity and robustness under low-CNR and signal distortion conditions.
A new method is proposed in this paper to accomplish the carrier frequency estimation of non- cooperative underwater acoustic DSSS-BPSK signal. The carrier frequency estimated using the method is accurate even under low-CNR and signal distortion conditions. A rough estimation of the carrier frequency is first made through gravity method. With the concave point characteristic of the signal power spectrum envelope at the carrier frequency, a more precise carrier frequency is then estimated by searching the local minimum of the power spectrum envelope in the frequency neighborhood of the rough estimation. Monte Carlo simulations of the method are in accord with theoretical analysis. Results of oceanic experimental data test also verify the effectiveness feasibility and practicality of the method for its low complexity and robustness under low-CNR and signal distortion conditions.
2009, 31(10): 2443-2448.
doi: 10.3724/SP.J.1146.2008.01328
Abstract:
A new algorithm named as M-elitist Evolutionary Algorithm (MEA) is presented with low complexity and high performance to approach the performance of Maximum-Likelihood(ML) detection, for solving the problem of the high complexity of ML detection in real-time Vertical- Bell laboratories LAyered Space-Time (V-BLAST) communication system. The simulation of one knapsack problem validates the effectiveness of MEA to solve combinatorial optimization problems. Furthermore, the simulation of V-BLAST communication system shows that the MEA-based detection algorithm can approach the performance of ML well, and is superior to the detection algorithm based on standard genetic algorithm and that based on clonal selection algorithm as well as some classical ones.
A new algorithm named as M-elitist Evolutionary Algorithm (MEA) is presented with low complexity and high performance to approach the performance of Maximum-Likelihood(ML) detection, for solving the problem of the high complexity of ML detection in real-time Vertical- Bell laboratories LAyered Space-Time (V-BLAST) communication system. The simulation of one knapsack problem validates the effectiveness of MEA to solve combinatorial optimization problems. Furthermore, the simulation of V-BLAST communication system shows that the MEA-based detection algorithm can approach the performance of ML well, and is superior to the detection algorithm based on standard genetic algorithm and that based on clonal selection algorithm as well as some classical ones.
2009, 31(10): 2449-2454.
doi: 10.3724/SP.J.1146.2008.01300
Abstract:
The information within different cyclo-frequencies about the wideband cyclostationary signals may be complementary to each other, whether and to what degree can they be exploited synthetically to improve the Direction-Of-Arrival (DOA) performance with arrays for wideband cyclostationary signals owns much significance, especially when the Signal-to-Noise Ratio (SNR) is low. This paper analyzes the spectral correlation of the array output at different cyclo-frequencies, and verifies that the errors of their estimates from finite sampling are independent to each other, which demonstrates the possibility of multi-cycle synthesization. An effective way of multi-cycle focussing is also proposed to realize the process of synthesization. Simulation results show that the proposed multi-cycle focusing method greatly improved the DOA estimation performance for wideband cyclostationary signals when the SNR is low.
The information within different cyclo-frequencies about the wideband cyclostationary signals may be complementary to each other, whether and to what degree can they be exploited synthetically to improve the Direction-Of-Arrival (DOA) performance with arrays for wideband cyclostationary signals owns much significance, especially when the Signal-to-Noise Ratio (SNR) is low. This paper analyzes the spectral correlation of the array output at different cyclo-frequencies, and verifies that the errors of their estimates from finite sampling are independent to each other, which demonstrates the possibility of multi-cycle synthesization. An effective way of multi-cycle focussing is also proposed to realize the process of synthesization. Simulation results show that the proposed multi-cycle focusing method greatly improved the DOA estimation performance for wideband cyclostationary signals when the SNR is low.
2009, 31(10): 2455-2459.
doi: 10.3724/SP.J.1146.2008.01427
Abstract:
A time-domain Multi-Stage Algorithm (MSA) based on the second order statistics for blind source separation of convolutive mixtures is proposed. Whitening procedure is adopted to transform the mixing matrix into a unitary matrix. The unitary matrix is expressed as a column-block matrix according to the block-diagonalization structure in autocorrelation matrices of source signals at different time delays. A novel least square tri-quadratic cost function with respect to a certain column block of the unitary matrix is proposed utilizing the orthogonality between each two different column blocks. Furthermore, a regular Triply Iterative Algorithm (TIA) following the gradient descent idea is used to seek the minimum point of the tri-quadratic cost function by alternately estimating one of the three independent variables parameter subsets, obtaining a column block of the unitary matrix. With each column block being got by using the systemic multi-stage algorithm, the unitary matrix can be estimated and then the source signals can be retrieved. Simulations results illustrate that, the new method outperforms the classic SUB method and the recently proposed JBD-NonU method, and can be efficiently applied to the blind source separation of convolutive mixtures.
A time-domain Multi-Stage Algorithm (MSA) based on the second order statistics for blind source separation of convolutive mixtures is proposed. Whitening procedure is adopted to transform the mixing matrix into a unitary matrix. The unitary matrix is expressed as a column-block matrix according to the block-diagonalization structure in autocorrelation matrices of source signals at different time delays. A novel least square tri-quadratic cost function with respect to a certain column block of the unitary matrix is proposed utilizing the orthogonality between each two different column blocks. Furthermore, a regular Triply Iterative Algorithm (TIA) following the gradient descent idea is used to seek the minimum point of the tri-quadratic cost function by alternately estimating one of the three independent variables parameter subsets, obtaining a column block of the unitary matrix. With each column block being got by using the systemic multi-stage algorithm, the unitary matrix can be estimated and then the source signals can be retrieved. Simulations results illustrate that, the new method outperforms the classic SUB method and the recently proposed JBD-NonU method, and can be efficiently applied to the blind source separation of convolutive mixtures.
2009, 31(10): 2460-2464.
doi: 10.3724/SP.J.1146.2008.01283
Abstract:
The located text regions need to be binarized for accurate recognition in automatic textural extraction. Due to the complex backgrounds, traditional thresholding methods can not segment the character image effectively from natural scenes. A novel approach of binarization is proposed for gray images. The proposed algorithm uses the Normalized graph cut(Ncut) as the measure for spectral clustering, and the weighted matrices used in evaluating the graph cuts are based on the gray levels of an image, rather than the commonly used image pixels. Thus, the proposed algorithm requires much smaller spatial costs and much lower computation complexity. Experiments on text images in natural scene show the superior performance of the proposed method compared to the typical thresholding algorithms.
The located text regions need to be binarized for accurate recognition in automatic textural extraction. Due to the complex backgrounds, traditional thresholding methods can not segment the character image effectively from natural scenes. A novel approach of binarization is proposed for gray images. The proposed algorithm uses the Normalized graph cut(Ncut) as the measure for spectral clustering, and the weighted matrices used in evaluating the graph cuts are based on the gray levels of an image, rather than the commonly used image pixels. Thus, the proposed algorithm requires much smaller spatial costs and much lower computation complexity. Experiments on text images in natural scene show the superior performance of the proposed method compared to the typical thresholding algorithms.
2009, 31(10): 2465-2469.
doi: 10.3724/SP.J.1146.2008.01344
Abstract:
A novel method of extracting affine invariant feature is proposed using the theory of Generalized Canonical Correlation Analysis(GCCA). First, a new kind of transformation named MSAE is constructed based on MSA. Second, MSAE is proved to be affine invariant. Then MSA is combined with MSAE using GCCA to obtain a new feature with more information. Finally, the coil-100 image database viewed from different angles in the case of Gaussian noise or occlusion is put into recognition experiments using minimum distance classifier. The comparing results among MSA, MSAE and combined feature indicate that the combined feature can obtain highest recognition accuracy followed by MSAE and MSA in turn.
A novel method of extracting affine invariant feature is proposed using the theory of Generalized Canonical Correlation Analysis(GCCA). First, a new kind of transformation named MSAE is constructed based on MSA. Second, MSAE is proved to be affine invariant. Then MSA is combined with MSAE using GCCA to obtain a new feature with more information. Finally, the coil-100 image database viewed from different angles in the case of Gaussian noise or occlusion is put into recognition experiments using minimum distance classifier. The comparing results among MSA, MSAE and combined feature indicate that the combined feature can obtain highest recognition accuracy followed by MSAE and MSA in turn.
2009, 31(10): 2470-2475.
doi: 10.3724/SP.J.1146.2009.00161
Abstract:
Calculating methods of normal vector, principal curvatures and principal directions at each triangular mesh vertexes are researched. Types of vertexes on surface are analyzed. A method for mosaicing broken objects based on fractured faces matching is presented. Directed feature vectors and undirected feature vectors used in surface matching are consisted of directed footprints and undirected footprints respectively. Directed features similarity of pair of matching points is measured through mapping direction of matching points based on undirected features matching. Calculating for matching fractured face is completed. Based on fractured face matching, broken objects mosaicing are realized through mapping direction of pairs of matching points. Experimental results show that presented algorithm can mosaic broken objects reliably.
Calculating methods of normal vector, principal curvatures and principal directions at each triangular mesh vertexes are researched. Types of vertexes on surface are analyzed. A method for mosaicing broken objects based on fractured faces matching is presented. Directed feature vectors and undirected feature vectors used in surface matching are consisted of directed footprints and undirected footprints respectively. Directed features similarity of pair of matching points is measured through mapping direction of matching points based on undirected features matching. Calculating for matching fractured face is completed. Based on fractured face matching, broken objects mosaicing are realized through mapping direction of pairs of matching points. Experimental results show that presented algorithm can mosaic broken objects reliably.
2009, 31(10): 2476-2482.
doi: 10.3724/SP.J.1146.2009.00699
Abstract:
In order to solve the low accuracy diagnosis of metastases and non-metastases tumid lymph nodes in the lung cancer N stage with chest CT images, effective image features of lymph nodes need to be found for quickly and accurately differentiating metastases and non-metastases tumid lymph nodes. First, tumid lymph nodes are extracted from chest CT images using interactive segmentation. Second, the multi-resolution histograms of tumid lymph nodes are directly calculated to receive a high-dimensional features sample set with spatial information. Then the classifier for differentiating metastases and non-metastases tumid lymph nodes is constructed with making full use the advantage of SVM which is good at dealing with high dimensional data sets. Finally, the performance of classification is evaluated by testing the trained SVM with the test sample set. The test results by 96 cases show that it takes 1.91 s for computing 200 dimensional features of 100 lymph nodes, 1.36 s for training and testing the SVM classifier. Receiver Operating Characteristic (ROC) analysis of the classification performance shows that the sensitivity is 76%, specificity is 64%, accuracy is 70%, and the Area Under Curve (AUC) is nearly 0.6525. Image spatial information can effectively express the characteristics of lymph nodes, the classification accuracy of metastases and non-metastases tumid lymph nodes is up to 70% without medical signs, and the classification speed is about 10 times than traditional texture methods. It provides a feasible, simple, objective method for improving the accuracy of the lung cancer N stage in medical imaging diagnosis.
In order to solve the low accuracy diagnosis of metastases and non-metastases tumid lymph nodes in the lung cancer N stage with chest CT images, effective image features of lymph nodes need to be found for quickly and accurately differentiating metastases and non-metastases tumid lymph nodes. First, tumid lymph nodes are extracted from chest CT images using interactive segmentation. Second, the multi-resolution histograms of tumid lymph nodes are directly calculated to receive a high-dimensional features sample set with spatial information. Then the classifier for differentiating metastases and non-metastases tumid lymph nodes is constructed with making full use the advantage of SVM which is good at dealing with high dimensional data sets. Finally, the performance of classification is evaluated by testing the trained SVM with the test sample set. The test results by 96 cases show that it takes 1.91 s for computing 200 dimensional features of 100 lymph nodes, 1.36 s for training and testing the SVM classifier. Receiver Operating Characteristic (ROC) analysis of the classification performance shows that the sensitivity is 76%, specificity is 64%, accuracy is 70%, and the Area Under Curve (AUC) is nearly 0.6525. Image spatial information can effectively express the characteristics of lymph nodes, the classification accuracy of metastases and non-metastases tumid lymph nodes is up to 70% without medical signs, and the classification speed is about 10 times than traditional texture methods. It provides a feasible, simple, objective method for improving the accuracy of the lung cancer N stage in medical imaging diagnosis.
2009, 31(10): 2483-2487.
doi: 10.3724/SP.J.1146.2008.01392
Abstract:
This paper presents an algorithm to select the optimal Gaussian filtering scale. First, it estimates the SNR of image to evaluate the noise degraded intensity of image. Second, it obtains the optimal Gaussian filtering scales by using optimal criteria on the sample images with varying intensity of noise. Finally, a statistically investigation of the relationship between the optimal Gaussian scales and their corresponding SNR and using the method of data fitting lead to the algorithm of estimating Gaussian filtering scale based on the SNR of image. Applied experiments on the algorithms of Canny edge detection and the nonlinear diffusion filtering demonstrate the efficiency of the proposed algorithm.
This paper presents an algorithm to select the optimal Gaussian filtering scale. First, it estimates the SNR of image to evaluate the noise degraded intensity of image. Second, it obtains the optimal Gaussian filtering scales by using optimal criteria on the sample images with varying intensity of noise. Finally, a statistically investigation of the relationship between the optimal Gaussian scales and their corresponding SNR and using the method of data fitting lead to the algorithm of estimating Gaussian filtering scale based on the SNR of image. Applied experiments on the algorithms of Canny edge detection and the nonlinear diffusion filtering demonstrate the efficiency of the proposed algorithm.
2009, 31(10): 2488-2492.
doi: 10.3724/SP.J.1146.2008.01471
Abstract:
A detector based on order statistic for range spread target in white Gaussian noise is derived in this paper. With the fact that the power of wideband radar target return is concentrated in several range bins, the data in the detection window is re-arranged in the order of energy decreasing, then the energy accumulation and detection is implemented in order, until the decision is made. The false alarm rate of the detector is derived and the method of threshold setting is proposed. Finally, the performance of proposed detector compared with that of the integration detector is given by Monte Carlo experiment, with two special energy distributing range profiles and a measured range profile of an actual target. For the range profiles that the energy of the return is concentrated in several range bins, the detector proposed in this paper has a better performance than the integration detector.
A detector based on order statistic for range spread target in white Gaussian noise is derived in this paper. With the fact that the power of wideband radar target return is concentrated in several range bins, the data in the detection window is re-arranged in the order of energy decreasing, then the energy accumulation and detection is implemented in order, until the decision is made. The false alarm rate of the detector is derived and the method of threshold setting is proposed. Finally, the performance of proposed detector compared with that of the integration detector is given by Monte Carlo experiment, with two special energy distributing range profiles and a measured range profile of an actual target. For the range profiles that the energy of the return is concentrated in several range bins, the detector proposed in this paper has a better performance than the integration detector.
2009, 31(10): 2493-2497.
doi: 10.3724/SP.J.1146.2008.01445
Abstract:
When distributed Space-borne SAR measures the ground moving target velocity using along track interferometry, larger baseline leads to serious velocity ambiguity. On the basis of exploring robust Chinese remainder theorem, this paper analyzes the method of deblurring velocity ambiguity for multi-baseline and multi-frequency distributed Space-borne SAR, which uses the principle that remainder theorem determines the unique resolution on some conditions. Moreover, the constraints of multi-baseline and multi-frequency, and the maximum measurement velocity value are derived. The simulation results show that the algorithm is efficient for deblurring velocity ambiguity, play a guiding role and provides reference for system design and baseline design of distributed Space-borne SAR.
When distributed Space-borne SAR measures the ground moving target velocity using along track interferometry, larger baseline leads to serious velocity ambiguity. On the basis of exploring robust Chinese remainder theorem, this paper analyzes the method of deblurring velocity ambiguity for multi-baseline and multi-frequency distributed Space-borne SAR, which uses the principle that remainder theorem determines the unique resolution on some conditions. Moreover, the constraints of multi-baseline and multi-frequency, and the maximum measurement velocity value are derived. The simulation results show that the algorithm is efficient for deblurring velocity ambiguity, play a guiding role and provides reference for system design and baseline design of distributed Space-borne SAR.
2009, 31(10): 2498-2503.
doi: 10.3724/SP.J.1146.2008.00770
Abstract:
In order to solve the problem of recognition to the ground-based radar station using an active radar seeker, the fusion recognition algorithms are put forward. Firstly the electromagnetic scattering model of the phased-array antenna is established. Then using Doppler Beam Sharpening (DBS) technology to improve the detection probability and to estimate targets RCS, then based on the extracted features－the range property and the period property of RCS, four kinds of characteristics of phased-array radar antenna are constituted. Finally the recognition algorithms as well as the fusion technique for target recognition are put forward. The simulation experiment indicated the effectiveness of the algorithm.
In order to solve the problem of recognition to the ground-based radar station using an active radar seeker, the fusion recognition algorithms are put forward. Firstly the electromagnetic scattering model of the phased-array antenna is established. Then using Doppler Beam Sharpening (DBS) technology to improve the detection probability and to estimate targets RCS, then based on the extracted features－the range property and the period property of RCS, four kinds of characteristics of phased-array radar antenna are constituted. Finally the recognition algorithms as well as the fusion technique for target recognition are put forward. The simulation experiment indicated the effectiveness of the algorithm.
2009, 31(10): 2504-2508.
doi: 10.3724/SP.J.1146.2008.01282
Abstract:
The cross-range scaling is the base of the pattern matching and target characteristic extraction. Using the approximately proportional relation between the Doppler frequency in cross range and the transverse coordinate position, and based on the orthogonal relation between the centerline and the line through axially symmetric points in the symmetrical target, a novel method of rotation angle estimation and cross range calibration is given for the symmetrical target. Then, the estimation error expression of the scaling parameter is offered, and influencing factors of the parameter estimation error is analyzed quantitatively. Finally, the ISAR imaging simulation results of both the warhead model on rotating platform and the outfield airplane data verify this method. This method has a very good application prospect to the ISAR image calibration aspect of cooperative maneuvering target with simple and low computation cost.
The cross-range scaling is the base of the pattern matching and target characteristic extraction. Using the approximately proportional relation between the Doppler frequency in cross range and the transverse coordinate position, and based on the orthogonal relation between the centerline and the line through axially symmetric points in the symmetrical target, a novel method of rotation angle estimation and cross range calibration is given for the symmetrical target. Then, the estimation error expression of the scaling parameter is offered, and influencing factors of the parameter estimation error is analyzed quantitatively. Finally, the ISAR imaging simulation results of both the warhead model on rotating platform and the outfield airplane data verify this method. This method has a very good application prospect to the ISAR image calibration aspect of cooperative maneuvering target with simple and low computation cost.
2009, 31(10): 2509-2513.
doi: 10.3724/SP.J.1146.2008.01442
Abstract:
The construction of available fusion models, such as that based on color space transform, on statistical, on multi-scale analysis is mostly based on the experience. These models have the problem that the parameters are subjectively chosen and can not be adjusted according to the follow applications of the fusion image. A image fusion framework of remote sensing is proposed based on data assimilation and particle swarm algorithm. Under this framework, weights of different attributes are determined according to their importance degree to the following process and object function is composed of the property weights, then the particle swarm algorithm is used to optimize the object function to get suitable image. A group experiments with the help of the entropy, mean gradient, standard variance, spatial frequency and structure similarity verify effectiveness of the framework.
The construction of available fusion models, such as that based on color space transform, on statistical, on multi-scale analysis is mostly based on the experience. These models have the problem that the parameters are subjectively chosen and can not be adjusted according to the follow applications of the fusion image. A image fusion framework of remote sensing is proposed based on data assimilation and particle swarm algorithm. Under this framework, weights of different attributes are determined according to their importance degree to the following process and object function is composed of the property weights, then the particle swarm algorithm is used to optimize the object function to get suitable image. A group experiments with the help of the entropy, mean gradient, standard variance, spatial frequency and structure similarity verify effectiveness of the framework.
2009, 31(10): 2514-2517.
doi: 10.3724/SP.J.1146.2008.01848
Abstract:
Considering the antenna mutual coupling problems on electrically large platforms, a fast algorithm of Time Domain Integral Equation (TDIE) based on the Geometry Theory of Diffraction (GTD) is proposed. On the basis of classical Marching-On in Time (MOT) solver, diffraction ray tracing method in GTD is introduced, and the calculation efficiency of retarded-time integral is raised. Numerical results prove that the proposed method can accelerate the process of MOT, and has the theoretical advising meaning towards the optimization design of antennas layout on electrically large platforms.
Considering the antenna mutual coupling problems on electrically large platforms, a fast algorithm of Time Domain Integral Equation (TDIE) based on the Geometry Theory of Diffraction (GTD) is proposed. On the basis of classical Marching-On in Time (MOT) solver, diffraction ray tracing method in GTD is introduced, and the calculation efficiency of retarded-time integral is raised. Numerical results prove that the proposed method can accelerate the process of MOT, and has the theoretical advising meaning towards the optimization design of antennas layout on electrically large platforms.
2009, 31(10): 2518-2522.
doi: 10.3724/SP.J.1146.2008.00624
Abstract:
A -TM610 mode double-gap coaxial cavity loaded by a coaxial line is proposed as the output circuit of X-band multi-beam klystron. Its main performances, such as bandwidth and power capacity, are studied. The results show that characteristics impedances along different beam hole are still almost equal after the output cavity coupled with a coaxial line. But the external quality factor of the output cavity is too large and difficult to diminish, so that the output bandwidth is small. The output power capacity reaches about 1MW. So it is suitable as a proper output circuit of high power narrowband multi-beam klystron of high radio-frequency.
A -TM610 mode double-gap coaxial cavity loaded by a coaxial line is proposed as the output circuit of X-band multi-beam klystron. Its main performances, such as bandwidth and power capacity, are studied. The results show that characteristics impedances along different beam hole are still almost equal after the output cavity coupled with a coaxial line. But the external quality factor of the output cavity is too large and difficult to diminish, so that the output bandwidth is small. The output power capacity reaches about 1MW. So it is suitable as a proper output circuit of high power narrowband multi-beam klystron of high radio-frequency.
2009, 31(10): 2523-2526.
doi: 10.3724/SP.J.1146.2008.00635
Abstract:
Based on the theory of finite polynomial ring, a novel code design method for Quasi-Cyclic Low Density Parity Check (QC-LDPC) codes with continuously variable length is proposed. When the cardinal number of the ring is larger than a certain threshold, the shift offset values can be formulated by the parameters selected in the ring. Thus all H matrices constructed by them have larger girth. In the design, the cardinal number of the ring is a continuously variable integer, which has a linear relation with the code length, so that the code length can be increased continuously. Analyses and proofs show that, the method can enlarge the number of QC-LDPC codes greatly, which can serve the adaptive link systems better.
Based on the theory of finite polynomial ring, a novel code design method for Quasi-Cyclic Low Density Parity Check (QC-LDPC) codes with continuously variable length is proposed. When the cardinal number of the ring is larger than a certain threshold, the shift offset values can be formulated by the parameters selected in the ring. Thus all H matrices constructed by them have larger girth. In the design, the cardinal number of the ring is a continuously variable integer, which has a linear relation with the code length, so that the code length can be increased continuously. Analyses and proofs show that, the method can enlarge the number of QC-LDPC codes greatly, which can serve the adaptive link systems better.
2009, 31(10): 2527-2531.
doi: 10.3724/SP.J.1146.2008.01414
Abstract:
A Luby Transform (LT) encoding algorithm based on parabolic map by using chaotic scrambling method is proposed. Firstly, chaotic sequences are produced by using parabolic map and then transformed into uniform-like sequences. The degree distribution and data set of neighbors of LT codes are generated by using position scrambling algorithm which is more sensitive than traditional importance sampling method keeping the construction of theoretical distribution. Experimental results show that the algorithm has more simple construction, smaller header costs of the packets, better encryption effect and furthermore is outperformed the traditional importance sampling method.
A Luby Transform (LT) encoding algorithm based on parabolic map by using chaotic scrambling method is proposed. Firstly, chaotic sequences are produced by using parabolic map and then transformed into uniform-like sequences. The degree distribution and data set of neighbors of LT codes are generated by using position scrambling algorithm which is more sensitive than traditional importance sampling method keeping the construction of theoretical distribution. Experimental results show that the algorithm has more simple construction, smaller header costs of the packets, better encryption effect and furthermore is outperformed the traditional importance sampling method.
2009, 31(10): 2532-2535.
doi: 10.3724/SP.J.1146.2008.01767
Abstract:
A type of baseband GMSK signal correlator is presented in this paper. From the phase probability density function of demodulated GMSK signal and the probability distribution function of the sums of independent identical distribution random variables, the auto-correlation and cross-correlation functions of the correlator are proposed. A uniform auto-correlation and cross-correlation probability distribution functions of digital correlator(digital matched filter) is derived from the probability and statistics theory. Numerical results demonstrate that the error probability of the baseband GMSK signal correlator is about one order of magnitude lower than that of digital one under the same condition.
A type of baseband GMSK signal correlator is presented in this paper. From the phase probability density function of demodulated GMSK signal and the probability distribution function of the sums of independent identical distribution random variables, the auto-correlation and cross-correlation functions of the correlator are proposed. A uniform auto-correlation and cross-correlation probability distribution functions of digital correlator(digital matched filter) is derived from the probability and statistics theory. Numerical results demonstrate that the error probability of the baseband GMSK signal correlator is about one order of magnitude lower than that of digital one under the same condition.
2009, 31(10): 2536-2540.
doi: 10.3724/SP.J.1146.2008.01361
Abstract:
It is obtained that every formant can be traced and found out by studying and analyzing the Chinese speech in the way of experiment in this paper, combining with the generally articulation feature of the Chinese speech, a speech enhancement algorithm based on tracing the formant is proposed. The speech frames can be determined from the non-speech frames effectively using the algorithm, and then, all the noise in the non-speech frames can be wiped off simply and validly, and noise in the speech frame can be degraded largely. Also, the algorithm has some other good characteristics, such as simple computation and noise-environment transplantability and so on.
It is obtained that every formant can be traced and found out by studying and analyzing the Chinese speech in the way of experiment in this paper, combining with the generally articulation feature of the Chinese speech, a speech enhancement algorithm based on tracing the formant is proposed. The speech frames can be determined from the non-speech frames effectively using the algorithm, and then, all the noise in the non-speech frames can be wiped off simply and validly, and noise in the speech frame can be degraded largely. Also, the algorithm has some other good characteristics, such as simple computation and noise-environment transplantability and so on.
