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2007 Vol. 29, No. 11
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2007, 29(11): 2541-2544.
doi: 10.3724/SP.J.1146.2006.01566
Abstract:
A new method for analyzing module reliability of Network Management System(NMS) in operational phase is proposed to resolve the problem existed in the domain of current NMS reliability evaluation. Firstly, some methods, e.g. periodic survival reports and module redundancy, which is used in NMS are assembled into three major run-time scenarios; Secondly, three scenario are modeled using Markov Regenerative Stochastic Petri Nets (MRSPN), and the effect which various scenario impose on module reliability is analyzed. Finally, some important reliability index, such as module availability, is concluded with applying the models. Numerical examples show that module reliability depend on both quality itself and run-time scenarios. Suitable run-time scenario can be applied in various modules according to the requirement of NMS.
A new method for analyzing module reliability of Network Management System(NMS) in operational phase is proposed to resolve the problem existed in the domain of current NMS reliability evaluation. Firstly, some methods, e.g. periodic survival reports and module redundancy, which is used in NMS are assembled into three major run-time scenarios; Secondly, three scenario are modeled using Markov Regenerative Stochastic Petri Nets (MRSPN), and the effect which various scenario impose on module reliability is analyzed. Finally, some important reliability index, such as module availability, is concluded with applying the models. Numerical examples show that module reliability depend on both quality itself and run-time scenarios. Suitable run-time scenario can be applied in various modules according to the requirement of NMS.
2007, 29(11): 2545-2548.
doi: 10.3724/SP.J.1146.2006.00550
Abstract:
This paper introduces a value-added service platform in Next Generation Network (NGN) enabled by grid technology to solve the performance issue with traditional application server in NGN. All of the value-added services hosted by this platform are wrapped into grid service. This platform provides running environment to value-added service in NGN. A grid-based task scheduling algorithm is also proposed with this platform. This grid-based task scheduling algorithm can solve the system performance bottleneck problem when system gets overload by leveraging existing resources in the same virtual organization with the help of grid technology. This paper models the service platform using Stochastic Petri Net (SPN), and the simulation experiment is done with SPNP (Stochastic Petri Net Package) to test the performance of the service platform according to this model. The simulation result verifies the platform can achieve the goal of improving the system performance.
This paper introduces a value-added service platform in Next Generation Network (NGN) enabled by grid technology to solve the performance issue with traditional application server in NGN. All of the value-added services hosted by this platform are wrapped into grid service. This platform provides running environment to value-added service in NGN. A grid-based task scheduling algorithm is also proposed with this platform. This grid-based task scheduling algorithm can solve the system performance bottleneck problem when system gets overload by leveraging existing resources in the same virtual organization with the help of grid technology. This paper models the service platform using Stochastic Petri Net (SPN), and the simulation experiment is done with SPNP (Stochastic Petri Net Package) to test the performance of the service platform according to this model. The simulation result verifies the platform can achieve the goal of improving the system performance.
2007, 29(11): 2549-2554.
doi: 10.3724/SP.J.1146.2006.00393
Abstract:
Differed from the traditional resolution method of selecting a service with highest priority, a method is proposed to resolve the Shared Trigger Interaction (STI) by dividing the services into consistent service and conflict service. The consistent services are conducted in turn combining the users intention with the system policy. The priority of the conflict service is calculated according to the interaction mechanism among the immune cells in the immune network theory, in which considered both the shared trigger services and the relative services providing users information, deduced the users intention on the service execution, and dynamically chose the best service with highest priority according to the consistent policy. The example analyses show that the method can resolve the STI effectively and meet the users demand.
Differed from the traditional resolution method of selecting a service with highest priority, a method is proposed to resolve the Shared Trigger Interaction (STI) by dividing the services into consistent service and conflict service. The consistent services are conducted in turn combining the users intention with the system policy. The priority of the conflict service is calculated according to the interaction mechanism among the immune cells in the immune network theory, in which considered both the shared trigger services and the relative services providing users information, deduced the users intention on the service execution, and dynamically chose the best service with highest priority according to the consistent policy. The example analyses show that the method can resolve the STI effectively and meet the users demand.
2007, 29(11): 2555-2559.
doi: 10.3724/SP.J.1146.2006.00613
Abstract:
In this paper, a new robust and efficient routing strategy for vehicular Ad hoc networks is proposed through analyzing existing routing strategies in city scenarios. A fixed node is set up on the junction, a twice-choice method for choosing routing directions and some repair strategies for city scenarios are presented. Simulation results show that the routing performance is improved by using the new algorithm.
In this paper, a new robust and efficient routing strategy for vehicular Ad hoc networks is proposed through analyzing existing routing strategies in city scenarios. A fixed node is set up on the junction, a twice-choice method for choosing routing directions and some repair strategies for city scenarios are presented. Simulation results show that the routing performance is improved by using the new algorithm.
2007, 29(11): 2560-2563.
doi: 10.3724/SP.J.1146.2005.01560
Abstract:
In large scale P2P networks, it is difficult to establish the trust relationship between peers as it is less likely that repeat interactions will occur with the same peer. So the network is vulnerable to malicious peers. A group based hierarchical reputation model for P2P networks is proposed in this paper to solve this problem. In this model, the trust relationship is classified into three tiers: the trust relationship between groups, the trust relationship between groups and peers, and the trust relationship between peers. A peer evaluates the trust of the given peer by its local trust information or the reference from the group it belonging to. The simulation and analyses show that the proposed reputation model can distinguish good peers and make them happy with the high ratio of the success query.
In large scale P2P networks, it is difficult to establish the trust relationship between peers as it is less likely that repeat interactions will occur with the same peer. So the network is vulnerable to malicious peers. A group based hierarchical reputation model for P2P networks is proposed in this paper to solve this problem. In this model, the trust relationship is classified into three tiers: the trust relationship between groups, the trust relationship between groups and peers, and the trust relationship between peers. A peer evaluates the trust of the given peer by its local trust information or the reference from the group it belonging to. The simulation and analyses show that the proposed reputation model can distinguish good peers and make them happy with the high ratio of the success query.
2007, 29(11): 2564-2568.
doi: 10.3724/SP.J.1146.2006.00569
Abstract:
While the current object oricented-based description of management operation mechanisms only focuses on operation-level details, the service-oriented methods are proposed, which can improve the description capability with contents involving business process characteristics, process flow and policy. At first, the relationships between network management functions, business process elements, and network management services are built, which provides network management services with meanings on both operation-level details and business process. Then, the description mechanisms of a service involving service interfaces, information, semantics, processes and policies, as well as a combined top-down and bottom-up network management service modeling process are proposed. At last, an example illustrating the above description aspects and analysis process is also provided. The proposed description methods support the business and customer oriented telecom operation strategy, and can effectively instruct the analysis, design, implementation and integration of network management or operation supporting systems.
While the current object oricented-based description of management operation mechanisms only focuses on operation-level details, the service-oriented methods are proposed, which can improve the description capability with contents involving business process characteristics, process flow and policy. At first, the relationships between network management functions, business process elements, and network management services are built, which provides network management services with meanings on both operation-level details and business process. Then, the description mechanisms of a service involving service interfaces, information, semantics, processes and policies, as well as a combined top-down and bottom-up network management service modeling process are proposed. At last, an example illustrating the above description aspects and analysis process is also provided. The proposed description methods support the business and customer oriented telecom operation strategy, and can effectively instruct the analysis, design, implementation and integration of network management or operation supporting systems.
2007, 29(11): 2569-2573.
doi: 10.3724/SP.J.1146.2006.00479
Abstract:
In this paper, the performance of cooperative diversity for reach-back problem in wireless sensor networks is studied, in which network synchronization or orthogonal channels are not necessary. The bit error rate and diversity order of destination are respectively developed for two typical channels, considering the error propagation appeared in the decode-and-forward procedure. Its shown by the analysis that the increase of the nodes number will improve the performance in destination if relays are at normal working point. To increase hop number is more effective for the scenario of AWGN channel among relays, while it is better to increase the number of branches when the channels among relays are Rayleigh fading. Cooperation diversity outperforms the direct transmission or the traditional spatio diversity if the relays are located in a certain region. Error propagation will reduce the diversity order of destination to 1, whereas almost has no influence on the diversity gain at the medium and low signal-noise-rate.
In this paper, the performance of cooperative diversity for reach-back problem in wireless sensor networks is studied, in which network synchronization or orthogonal channels are not necessary. The bit error rate and diversity order of destination are respectively developed for two typical channels, considering the error propagation appeared in the decode-and-forward procedure. Its shown by the analysis that the increase of the nodes number will improve the performance in destination if relays are at normal working point. To increase hop number is more effective for the scenario of AWGN channel among relays, while it is better to increase the number of branches when the channels among relays are Rayleigh fading. Cooperation diversity outperforms the direct transmission or the traditional spatio diversity if the relays are located in a certain region. Error propagation will reduce the diversity order of destination to 1, whereas almost has no influence on the diversity gain at the medium and low signal-noise-rate.
2007, 29(11): 2574-2579.
doi: 10.3724/SP.J.1146.2006.00328
Abstract:
By analyzing the present mainly prefetch algorithms advantages and disadvantages, ccording to the difference between VoiceXML-based voice platform and HTML-based World Wide Web, it is proposed that the voice resource should be prefetched in VoiceXML-based voice platform. An adaptive multi-user shared predict Markov model is presented to predict the probability of the forthcoming required resource of all the online users, which help to improve the veracity of the prediction. Finally, a preemptive priority model is designed to schedule the prefetch tasks, which mapped the resource access probability to the task priority. The simulation research shows that the predict algorithm and the schedule model can reduce delay of a users request and improve response speed better than that of single-user predict Markov model and Round-Robin (RR) schedule model.
By analyzing the present mainly prefetch algorithms advantages and disadvantages, ccording to the difference between VoiceXML-based voice platform and HTML-based World Wide Web, it is proposed that the voice resource should be prefetched in VoiceXML-based voice platform. An adaptive multi-user shared predict Markov model is presented to predict the probability of the forthcoming required resource of all the online users, which help to improve the veracity of the prediction. Finally, a preemptive priority model is designed to schedule the prefetch tasks, which mapped the resource access probability to the task priority. The simulation research shows that the predict algorithm and the schedule model can reduce delay of a users request and improve response speed better than that of single-user predict Markov model and Round-Robin (RR) schedule model.
2007, 29(11): 2580-2584.
doi: 10.3724/SP.J.1146.2006.00403
Abstract:
Anomaly detection acts as one of the important directions of research on Intrusion Detection Systems(IDSs).This paper presents a new method for anomaly detection of user behaviors based on shell commands and Markov chain models. The method constructs a one-order Markov chain model to represent the normal behavior profile of a network user, and associates shell commands with the states of the Markov chain. The parameters of the Markov chain model are estimated by a command matching algorithm which is computationally efficient. At the detection stage, the probabilities of the state sequences of the Markov chain is firstly computed, and two different schemes can be used to determine whether the monitored users behaviors are normal or anomalous while the particularity of user behaviors is taken into account. The application of the method in practical intrusion detection systems shows that it can achieve high detection performance.
Anomaly detection acts as one of the important directions of research on Intrusion Detection Systems(IDSs).This paper presents a new method for anomaly detection of user behaviors based on shell commands and Markov chain models. The method constructs a one-order Markov chain model to represent the normal behavior profile of a network user, and associates shell commands with the states of the Markov chain. The parameters of the Markov chain model are estimated by a command matching algorithm which is computationally efficient. At the detection stage, the probabilities of the state sequences of the Markov chain is firstly computed, and two different schemes can be used to determine whether the monitored users behaviors are normal or anomalous while the particularity of user behaviors is taken into account. The application of the method in practical intrusion detection systems shows that it can achieve high detection performance.
2007, 29(11): 2585-2588.
doi: 10.3724/SP.J.1146.2006.00609
Abstract:
The conventional PTS method of reducing OFDM signals PAPR has large computation complexity because of the computation of all sets of the phase rotation vectors. In this paper, a general principle of finding appropriate phase rotation vectors by analyzing the rule of the appearance of peak value for OFDM signals is presented. Based on the principle, a novel method is proposed which can remarkably reduce the complexity of PTS with little degradation of systems performance, as illustrated by theoretical analysis and simulation results.
The conventional PTS method of reducing OFDM signals PAPR has large computation complexity because of the computation of all sets of the phase rotation vectors. In this paper, a general principle of finding appropriate phase rotation vectors by analyzing the rule of the appearance of peak value for OFDM signals is presented. Based on the principle, a novel method is proposed which can remarkably reduce the complexity of PTS with little degradation of systems performance, as illustrated by theoretical analysis and simulation results.
2007, 29(11): 2589-2592.
doi: 10.3724/SP.J.1146.2006.00524
Abstract:
The performance of joint detection depends highly on the accuracy of channel estimation. In an intra-frequency network, inter-cell interfering signals are treated as white noise in conventional channel estimators, which degrades the accuracy of channel estimation. In this paper, a Minimum Mean Square Error (MMSE) based joint multi-cell channel estimation algorithm is proposed. By including the strong interfering users of adjacent cells into the channel estimation matrix, the noise power is significantly reduced which guarantees more precise channel estimation. The newly proposed algorithm can be applied to both multi-cell joint detection and single cell joint detection. Compared with conventional Steiner channel estimation, the proposed algorithm shows much higher estimation accuracy and then greatly improves the performance of the TD-SCDMA system.
The performance of joint detection depends highly on the accuracy of channel estimation. In an intra-frequency network, inter-cell interfering signals are treated as white noise in conventional channel estimators, which degrades the accuracy of channel estimation. In this paper, a Minimum Mean Square Error (MMSE) based joint multi-cell channel estimation algorithm is proposed. By including the strong interfering users of adjacent cells into the channel estimation matrix, the noise power is significantly reduced which guarantees more precise channel estimation. The newly proposed algorithm can be applied to both multi-cell joint detection and single cell joint detection. Compared with conventional Steiner channel estimation, the proposed algorithm shows much higher estimation accuracy and then greatly improves the performance of the TD-SCDMA system.
2007, 29(11): 2593-2598.
doi: 10.3724/SP.J.1146.2006.00563
Abstract:
In this paper, a cross-layer cooperative design is developed under the constraint of maximum transmission number per node in an uncoded two-hop relay network. Two-type simple single-relay adaptive cooperative protocols are proposed in order to exploit a combined spatial and time diversity. Analysis and simulation show that for the asymmetric multi-hop relay wireless networks, the cooperative protocols enable effective antenna/energy share and remarkable frame error rateperformance gain in block fading channels at the moderate loss of average throughput due to truncated ARQ(Automatic Repeat Request) re-transmissions.
In this paper, a cross-layer cooperative design is developed under the constraint of maximum transmission number per node in an uncoded two-hop relay network. Two-type simple single-relay adaptive cooperative protocols are proposed in order to exploit a combined spatial and time diversity. Analysis and simulation show that for the asymmetric multi-hop relay wireless networks, the cooperative protocols enable effective antenna/energy share and remarkable frame error rateperformance gain in block fading channels at the moderate loss of average throughput due to truncated ARQ(Automatic Repeat Request) re-transmissions.
2007, 29(11): 2599-2602.
doi: 10.3724/SP.J.1146.2006.00349
Abstract:
In order to realize the micropayment protocol with both full fairness and non-unit payment function, the concept of Double PayWord Chain(DPWC) and the realization mechanism of non-unit payment are presented first in this paper. Using DPWC, a new Fair Mobile Micropayment Protocol(FMMP) based on Data Service Management Platform(DSMP) is developed. The new protocol consists of 5 subprotocols: registration, payment, arbitration, settlement and cancellation. Full fair payment and non-unit payment can be provided by FMMP. In addition, FMMP has characteristics of security, efficiency and nonrepudiation.
In order to realize the micropayment protocol with both full fairness and non-unit payment function, the concept of Double PayWord Chain(DPWC) and the realization mechanism of non-unit payment are presented first in this paper. Using DPWC, a new Fair Mobile Micropayment Protocol(FMMP) based on Data Service Management Platform(DSMP) is developed. The new protocol consists of 5 subprotocols: registration, payment, arbitration, settlement and cancellation. Full fair payment and non-unit payment can be provided by FMMP. In addition, FMMP has characteristics of security, efficiency and nonrepudiation.
2007, 29(11): 2603-2605.
doi: 10.3724/SP.J.1146.2006.00508
Abstract:
In recent years, there has been considerable interest in distributed antenna system due to its promising improvement in coverage, power efficiency and channel capacity. But many papers are only focused on these cases and do not consider multiuser diversity. A minimal capacity loss Round-Robin scheduling algorithm is presented in this paper. Coupled with this algorithm, the multiuser diversity is studied in downlink distributed antenna system based on zero-forcing beamforming. The results show that with the same antenna number and sum power Distributed Antenna System (DAS) is preferable to Co-located Antenna System (CAS) in term of multiuser diversity gain. The minimal capacity loss Round-Robin scheduling algorithm distinctly outperforms common Round-Robin scheduling algorithm and it can be used in DAS and CAS.
In recent years, there has been considerable interest in distributed antenna system due to its promising improvement in coverage, power efficiency and channel capacity. But many papers are only focused on these cases and do not consider multiuser diversity. A minimal capacity loss Round-Robin scheduling algorithm is presented in this paper. Coupled with this algorithm, the multiuser diversity is studied in downlink distributed antenna system based on zero-forcing beamforming. The results show that with the same antenna number and sum power Distributed Antenna System (DAS) is preferable to Co-located Antenna System (CAS) in term of multiuser diversity gain. The minimal capacity loss Round-Robin scheduling algorithm distinctly outperforms common Round-Robin scheduling algorithm and it can be used in DAS and CAS.
2007, 29(11): 2606-2608.
doi: 10.3724/SP.J.1146.2006.01171
Abstract:
To research the information capacity of the Asynchronous Optical Code Division Multiple Access (OCDMA) system, the system model and its implementation under ideal channel and AWGN channel optical communications are presented. We modeled a discrete memoryless channel OCDMA system and evaluated the aggregate capacity from the probability of the output signal at the chip level. On the condition that the information capacity limited by 1 bit per chip, the results show that the interference caused by asynchronism reduces the capacity limit as the number of users increases, but for a sufficiently large number of users, both the ideal and the AWGN channel throughput limit varies slowly and the limit is around 0.71-0.75 bit/chip. With less number of users of the ideal channel, the more the input probability is lower than 0.50, the lower the largest capacity limit will be. With low noise variance of the AWGN channel, the system with smaller users can attain higher capacity limit. So the information capacity of the asynchronous OCDMA is gotten.
To research the information capacity of the Asynchronous Optical Code Division Multiple Access (OCDMA) system, the system model and its implementation under ideal channel and AWGN channel optical communications are presented. We modeled a discrete memoryless channel OCDMA system and evaluated the aggregate capacity from the probability of the output signal at the chip level. On the condition that the information capacity limited by 1 bit per chip, the results show that the interference caused by asynchronism reduces the capacity limit as the number of users increases, but for a sufficiently large number of users, both the ideal and the AWGN channel throughput limit varies slowly and the limit is around 0.71-0.75 bit/chip. With less number of users of the ideal channel, the more the input probability is lower than 0.50, the lower the largest capacity limit will be. With low noise variance of the AWGN channel, the system with smaller users can attain higher capacity limit. So the information capacity of the asynchronous OCDMA is gotten.
2007, 29(11): 2609-2611.
doi: 10.3724/SP.J.1146.2005.00069
Abstract:
A novel space-time block encoding and decoding method in MIMO CDMA system is proposed in this paper. It is called Cyclic Space-Time Block Code (C-STBC). The input data stream is circularly encoded in block, and then the encoded data streams are transmitted through different antenna by multiplying different spread code respectively. The proposed C-STBC scheme in CDMA system can achieve full coding rate and full diversity gain but the decoding method is simple as the conventional STBC. Simulation results show that the proposed C-STBC is superior to the conventional STBC.
A novel space-time block encoding and decoding method in MIMO CDMA system is proposed in this paper. It is called Cyclic Space-Time Block Code (C-STBC). The input data stream is circularly encoded in block, and then the encoded data streams are transmitted through different antenna by multiplying different spread code respectively. The proposed C-STBC scheme in CDMA system can achieve full coding rate and full diversity gain but the decoding method is simple as the conventional STBC. Simulation results show that the proposed C-STBC is superior to the conventional STBC.
2007, 29(11): 2612-2615.
doi: 10.3724/SP.J.1146.2006.00496
Abstract:
An adaptive multistage beamforming receiver with a low complexity that is suitable for CDMA wireless communication systems is proposed in this paper. The receiver adopts a novel orthogonal multistage structure to achieve the system optimization which is carried out independently at each stage. The system parameters for each stage are obtained through a simple iterative procedure, and a complex weight is set up at each stage. The MMSE optimization criterion is used to compute and update the adaptive weight. The number of stages is determined by signal environments to make the system more flexible. In comparison with other methods, the proposed system provides an improved performance especially in correlated signal environments. In addition, it gives a reduced computational complexity.
An adaptive multistage beamforming receiver with a low complexity that is suitable for CDMA wireless communication systems is proposed in this paper. The receiver adopts a novel orthogonal multistage structure to achieve the system optimization which is carried out independently at each stage. The system parameters for each stage are obtained through a simple iterative procedure, and a complex weight is set up at each stage. The MMSE optimization criterion is used to compute and update the adaptive weight. The number of stages is determined by signal environments to make the system more flexible. In comparison with other methods, the proposed system provides an improved performance especially in correlated signal environments. In addition, it gives a reduced computational complexity.
2007, 29(11): 2616-2619.
doi: 10.3724/SP.J.1146.2006.00548
Abstract:
A block transmission scheme with frequency domain pilots is proposed. Algorithms with low complexity are proposed too, which include channel estimation and equalization algorithm. Compared with the existed block transmission scheme with PN pilots, it is proved by simulations that the block transmission scheme with frequency domain pilots achieves reducing complexity without loss of BER performance.
A block transmission scheme with frequency domain pilots is proposed. Algorithms with low complexity are proposed too, which include channel estimation and equalization algorithm. Compared with the existed block transmission scheme with PN pilots, it is proved by simulations that the block transmission scheme with frequency domain pilots achieves reducing complexity without loss of BER performance.
2007, 29(11): 2620-2623.
doi: 10.3724/SP.J.1146.2006.00670
Abstract:
For burst mode in slowly time-varying channel, channel state information can be obtained mostly based on preamble and supposed maintain constant. In fact, for different OFDM symbol, channel change slowly, so the assumption degrades the system performance. A low-complexity technique is presented to estimate and track the channel for ZP-OFDM. Channel state information can be obtained in the first OFDM symbol based on comb-type pilots and tracked by insert a bit in time-domain for others OFDM symbols. Simulation results verify the improved performance of the proposed method.
For burst mode in slowly time-varying channel, channel state information can be obtained mostly based on preamble and supposed maintain constant. In fact, for different OFDM symbol, channel change slowly, so the assumption degrades the system performance. A low-complexity technique is presented to estimate and track the channel for ZP-OFDM. Channel state information can be obtained in the first OFDM symbol based on comb-type pilots and tracked by insert a bit in time-domain for others OFDM symbols. Simulation results verify the improved performance of the proposed method.
2007, 29(11): 2624-2627.
doi: 10.3724/SP.J.1146.2006.00855
Abstract:
The problem of the analyses of Space-Time Block Coding (STBC) in impulsive, non-Gaussian noise environments is considered. A model of an additive mixture of Gaussian and non-Gaussian impulsive noise is adopted, and the asymptotical solution of the closed-form expression for the average symbol error rate (SER) of orthogonal space-time block coding over Rayleigh flat fading channel is derived by means of the Moment Generating Function (MGF) with the approximate equivalent Multiple-Input Single-Output (MISO) model of mixture noise. Also, the performance evaluation of STBC is performed in terms of the impulsive noise occurring probability and the power ratio of the impulsive noise to the Gaussian noise. It is shown that mixture noise degrades the system performance significantly even at high SNR. Monte Caro simulation results corroborate the effectiveness of analyses.
The problem of the analyses of Space-Time Block Coding (STBC) in impulsive, non-Gaussian noise environments is considered. A model of an additive mixture of Gaussian and non-Gaussian impulsive noise is adopted, and the asymptotical solution of the closed-form expression for the average symbol error rate (SER) of orthogonal space-time block coding over Rayleigh flat fading channel is derived by means of the Moment Generating Function (MGF) with the approximate equivalent Multiple-Input Single-Output (MISO) model of mixture noise. Also, the performance evaluation of STBC is performed in terms of the impulsive noise occurring probability and the power ratio of the impulsive noise to the Gaussian noise. It is shown that mixture noise degrades the system performance significantly even at high SNR. Monte Caro simulation results corroborate the effectiveness of analyses.
2007, 29(11): 2628-2631.
doi: 10.3724/SP.J.1146.2006.00659
Abstract:
The MIMO channel is changed into the mixture channel using the eigenvector of the channel matrix. The adaptive modulation together with power allocation is studied in order to maximize the system capacity under the constraint of total transmit power and Quality of Service (QoS). The information needed at the transmitter such as beamforming vector and power allocation vector is conveyed back using limited feedback. The simulation results show that the proposed scheme can improve the capacity greatly at low SNR.
The MIMO channel is changed into the mixture channel using the eigenvector of the channel matrix. The adaptive modulation together with power allocation is studied in order to maximize the system capacity under the constraint of total transmit power and Quality of Service (QoS). The information needed at the transmitter such as beamforming vector and power allocation vector is conveyed back using limited feedback. The simulation results show that the proposed scheme can improve the capacity greatly at low SNR.
2007, 29(11): 2632-2636.
doi: 10.3724/SP.J.1146.2006.00373
Abstract:
To resolve the channel resources waste problem of the typical source-specific multicast routing algorithm in Low Earth Orbit (LEO) satellite IP networks, a new core-based shared tree algorithm named Core-cluster Combination-based Shared Tree (CCST) algorithm is proposed in this paper. It includes a core selection method named Dynamic Approximate Center (DAC) and a multicast route construction scheme named core-cluster combination. The DAC method selects core node based on virtually static and regular network topology formed by logical locations. The core-cluster combination scheme takes core node as initial core-cluster, and extends it to construct entire multicast tree with the lowest tree cost step by step by a shortest path scheme between newly-generated core-cluster and surplus group members, which can greatly improve transport bandwidth utilization and multicast transport efficiency. Finally, the CCST algorithm is compared with several other typical algorithms in LEO satellite IP networks, and simulation results show that its tree cost performance is greatly better than the others at the expense of a bit higher end-to-end propagation delay.
To resolve the channel resources waste problem of the typical source-specific multicast routing algorithm in Low Earth Orbit (LEO) satellite IP networks, a new core-based shared tree algorithm named Core-cluster Combination-based Shared Tree (CCST) algorithm is proposed in this paper. It includes a core selection method named Dynamic Approximate Center (DAC) and a multicast route construction scheme named core-cluster combination. The DAC method selects core node based on virtually static and regular network topology formed by logical locations. The core-cluster combination scheme takes core node as initial core-cluster, and extends it to construct entire multicast tree with the lowest tree cost step by step by a shortest path scheme between newly-generated core-cluster and surplus group members, which can greatly improve transport bandwidth utilization and multicast transport efficiency. Finally, the CCST algorithm is compared with several other typical algorithms in LEO satellite IP networks, and simulation results show that its tree cost performance is greatly better than the others at the expense of a bit higher end-to-end propagation delay.
2007, 29(11): 2637-2640.
doi: 10.3724/SP.J.1146.2006.00635
Abstract:
CDMA is superior to others methods in the anti-collision of UHF RFID systems for its anti-jamming, security features. A mechanism of anti-collision base on CDMA and its circuits is designed in this paper. This mechanism is simulated, so the relationship of time consumption of identification with the count of Tags is educed and discussed.
CDMA is superior to others methods in the anti-collision of UHF RFID systems for its anti-jamming, security features. A mechanism of anti-collision base on CDMA and its circuits is designed in this paper. This mechanism is simulated, so the relationship of time consumption of identification with the count of Tags is educed and discussed.
2007, 29(11): 2641-2644.
doi: 10.3724/SP.J.1146.2006.00567
Abstract:
A chaotic synchronization secure communication method based on several Lorenz systems switch is proposed. These Lorenz systems are built, which are relevant and can be switched each other via the choicer. Chaotic synchronization of these systems is realized using same nonlinear feedback control method. The transmitter can be switched discretionarily among several chaotic systems, bring on ceaseless changing of the chaotic carriers in transport channel. In the receiver, the chaotic carriers are retrieved from the received signals, then the information signals are recovered. The experiment result shows that this chaotic synchronization secure communications method based on several chaotic systems switch is better in security because of the transmitter can be switched and the chaotic carriers can be changed discretionarily.
A chaotic synchronization secure communication method based on several Lorenz systems switch is proposed. These Lorenz systems are built, which are relevant and can be switched each other via the choicer. Chaotic synchronization of these systems is realized using same nonlinear feedback control method. The transmitter can be switched discretionarily among several chaotic systems, bring on ceaseless changing of the chaotic carriers in transport channel. In the receiver, the chaotic carriers are retrieved from the received signals, then the information signals are recovered. The experiment result shows that this chaotic synchronization secure communications method based on several chaotic systems switch is better in security because of the transmitter can be switched and the chaotic carriers can be changed discretionarily.
2007, 29(11): 2645-2648.
doi: 10.3724/SP.J.1146.2006.01167
Abstract:
The ring signature is one of the anonymous techniques by virtue of its unconditional anonymity. Most proposed ring signature schemes have the problem that the size of ring signatures depends linearly on the group size. That is an open problem. In this paper, new scheme called constant-size ring signatures is presented. The scheme is based on bilinear pairings and accumulators. In the scheme, users can send messages anonymously, and the size of the signature is independent of the group size. Therefore, the scheme proposed can be used to solve the open problem.
The ring signature is one of the anonymous techniques by virtue of its unconditional anonymity. Most proposed ring signature schemes have the problem that the size of ring signatures depends linearly on the group size. That is an open problem. In this paper, new scheme called constant-size ring signatures is presented. The scheme is based on bilinear pairings and accumulators. In the scheme, users can send messages anonymously, and the size of the signature is independent of the group size. Therefore, the scheme proposed can be used to solve the open problem.
Algorithm for Modulation Recognition Based on Characteristic Function in Impulsive Noise Environment
2007, 29(11): 2649-2652.
doi: 10.3724/SP.J.1146.2006.00490
Abstract:
Wireless channel environment is influenced by Gauss noise and impulsive noise. A new algorithm is proposed based on Characteristic Function (CF) phase of received signal by analyzing the feature of SS impulsive noise. The classification vectors are composed of CF phase corresponding to different angle. The method of minimum mean squared distance is used to classify unknown modulation type. Theoretical analysis proves this algorithm is invariant to the presence of SS noise. Simulations show average successful rates are both more than 90% in impulsive noise and Gauss noise channel when SNR is above 8dB.
Wireless channel environment is influenced by Gauss noise and impulsive noise. A new algorithm is proposed based on Characteristic Function (CF) phase of received signal by analyzing the feature of SS impulsive noise. The classification vectors are composed of CF phase corresponding to different angle. The method of minimum mean squared distance is used to classify unknown modulation type. Theoretical analysis proves this algorithm is invariant to the presence of SS noise. Simulations show average successful rates are both more than 90% in impulsive noise and Gauss noise channel when SNR is above 8dB.
2007, 29(11): 2653-2656.
doi: 10.3724/SP.J.1146.2006.00333
Abstract:
This paper utilizes FFT after undersampling to analyze the relationship between the estimation of sinusoidal parameters and corresponding actual values on the basis of bandpass sampling theorem. In addition, the errors of parameter estimation using phase difference are deduced strictly. Investigation indicates that the error of frequency estimation is proportional to the sampling rate, while that of initial phase independent of it. The results of computer simulation show the validity of academic conclusions.
This paper utilizes FFT after undersampling to analyze the relationship between the estimation of sinusoidal parameters and corresponding actual values on the basis of bandpass sampling theorem. In addition, the errors of parameter estimation using phase difference are deduced strictly. Investigation indicates that the error of frequency estimation is proportional to the sampling rate, while that of initial phase independent of it. The results of computer simulation show the validity of academic conclusions.
2007, 29(11): 2657-2660.
doi: 10.3724/SP.J.1146.2006.00619
Abstract:
Steerable filters are a class of filter banks that can implement oriented filtering, and they have less computation quantity than usual oriented filters and can obtain omni-oriented filtering. This paper introduces the wavelet functions and the multiresolution relationship into the process of the steerable filters, and achieves images oriented filtering. The wavelets can extract more orientation information from images, and the experiments verify the steerable filter, which is designed from the wavelet transform.
Steerable filters are a class of filter banks that can implement oriented filtering, and they have less computation quantity than usual oriented filters and can obtain omni-oriented filtering. This paper introduces the wavelet functions and the multiresolution relationship into the process of the steerable filters, and achieves images oriented filtering. The wavelets can extract more orientation information from images, and the experiments verify the steerable filter, which is designed from the wavelet transform.
2007, 29(11): 2661-2664.
doi: 10.3724/SP.J.1146.2006.00617
Abstract:
The Support Vector Clustering (SVC) algorithm is introduced to get the number of the pinnacles in the result of the time-frequency analysis and Radon transform of the multi-component Linear FM (LFM) signal, and to finish the detection of the components of the LFM signal. Meanwhile, the preprocessing to reduce the points number of the input data-set for SVC is proposed to improve the computation efficiency. And a novel cluster labeling method is developed to improve the SVC algorithm. The simulation results depict that the SVC-Radon-time-frequency approach is efficient for the detection and parameter estimation of the multi-components LFM signal with low SNR.
The Support Vector Clustering (SVC) algorithm is introduced to get the number of the pinnacles in the result of the time-frequency analysis and Radon transform of the multi-component Linear FM (LFM) signal, and to finish the detection of the components of the LFM signal. Meanwhile, the preprocessing to reduce the points number of the input data-set for SVC is proposed to improve the computation efficiency. And a novel cluster labeling method is developed to improve the SVC algorithm. The simulation results depict that the SVC-Radon-time-frequency approach is efficient for the detection and parameter estimation of the multi-components LFM signal with low SNR.
An Algorithm of Estimation Direction of Arrival for Phase Interferometer Array Using Cosine Function
2007, 29(11): 2665-2668.
doi: 10.3724/SP.J.1146.2006.00560
Abstract:
In the background of phase ambiguity in using phase interferometer to estimate the direction of arrival, a new algorithm is proposed for estimation Direction Of Arrival (DOA) using phase interferometer array with cosine function. The condition on the uniqueness of the estimation direction of arrival is obtained, which is looser than the one of the other algorithms. Simulation results under different condition show that as far as the uniqueness is satisfied, this new algorithm is available for the estimation direction of arrival.
In the background of phase ambiguity in using phase interferometer to estimate the direction of arrival, a new algorithm is proposed for estimation Direction Of Arrival (DOA) using phase interferometer array with cosine function. The condition on the uniqueness of the estimation direction of arrival is obtained, which is looser than the one of the other algorithms. Simulation results under different condition show that as far as the uniqueness is satisfied, this new algorithm is available for the estimation direction of arrival.
2007, 29(11): 2669-2671.
doi: 10.3724/SP.J.1146.2006.00604
Abstract:
Pitch parameter is often quantized uniformly with no distortion using 7 bit in speech coding applications. As pitch changes slowly in voiced segments, in order to remove the correlation between two consecutive pitch more effectively, based on Eriksson and Kangs 4 bit pitch quantization algorithm, this paper implements a pitch quantization algorithm using 4~6 bit for Chinese. This algorithm has a small complexity and no codebook is needed. This pitch quantization algorithm is applied to WI model and WI coder, the results from the subjective A/B listening test indicate that this algorithm not only quantized pitch effectively, but also kept the quality of synthesized speech with no obvious hearing distortion. Therefore, it satisfies the accuracy of the quantized pitch of WI coder completely.
Pitch parameter is often quantized uniformly with no distortion using 7 bit in speech coding applications. As pitch changes slowly in voiced segments, in order to remove the correlation between two consecutive pitch more effectively, based on Eriksson and Kangs 4 bit pitch quantization algorithm, this paper implements a pitch quantization algorithm using 4~6 bit for Chinese. This algorithm has a small complexity and no codebook is needed. This pitch quantization algorithm is applied to WI model and WI coder, the results from the subjective A/B listening test indicate that this algorithm not only quantized pitch effectively, but also kept the quality of synthesized speech with no obvious hearing distortion. Therefore, it satisfies the accuracy of the quantized pitch of WI coder completely.
2007, 29(11): 2672-2675.
doi: 10.3724/SP.J.1146.2006.00608
Abstract:
In traditional low bit-rate speech coding, considering that ears are not sensitive to phase information, the phase information is often neglected, and this will result in coarse and harsh speech quality, and it even may lead to inflection in pitch. In order to obtain a high-quality speech codec, the phase information of speech should be included in codec. In this paper, the phase redundancy is reduced further based on the dispersion phase vector quantization method. In the waveform interpolation (WI) speech coding model, the difference of SEWs phase spectra of conjoint frames is quantized using predictive vector quantization. The result of this scheme reveals that the speech quality is improved, and its naturalness and articulation are increased greatly. Subjective A/B listening test indicates that the reconstructed speechs quality of this method is better than that of fixed phase with 4-6 bit. Compared with the dispersion phase vector quantization method, the synthesis speech is slightly improved for female speakers.
In traditional low bit-rate speech coding, considering that ears are not sensitive to phase information, the phase information is often neglected, and this will result in coarse and harsh speech quality, and it even may lead to inflection in pitch. In order to obtain a high-quality speech codec, the phase information of speech should be included in codec. In this paper, the phase redundancy is reduced further based on the dispersion phase vector quantization method. In the waveform interpolation (WI) speech coding model, the difference of SEWs phase spectra of conjoint frames is quantized using predictive vector quantization. The result of this scheme reveals that the speech quality is improved, and its naturalness and articulation are increased greatly. Subjective A/B listening test indicates that the reconstructed speechs quality of this method is better than that of fixed phase with 4-6 bit. Compared with the dispersion phase vector quantization method, the synthesis speech is slightly improved for female speakers.
2007, 29(11): 2676-2678.
doi: 10.3724/SP.J.1146.2006.00666
Abstract:
The target capture is the key technology of the space-based early warning system. In this paper, the thrust acceleration is analyzed, and then the nonlinear model of ballistic missile in the image is presented. Combined with the Probabilistic Data Association (PDA), the likelihood function is denoted, and the optimal weighted probability is calculated using Lagrange way which causes the logarithmic likelihood ratio maximum. Using the amplitude information of measurement, under low Signal-to-noise (SNR) the detection performance is improved. Via the Monte Carlo simulation, this method has the better detection performance and estimation accuracy than other approaches. It is applicable for the target capture under low SNR in the space-based early warning system.
The target capture is the key technology of the space-based early warning system. In this paper, the thrust acceleration is analyzed, and then the nonlinear model of ballistic missile in the image is presented. Combined with the Probabilistic Data Association (PDA), the likelihood function is denoted, and the optimal weighted probability is calculated using Lagrange way which causes the logarithmic likelihood ratio maximum. Using the amplitude information of measurement, under low Signal-to-noise (SNR) the detection performance is improved. Via the Monte Carlo simulation, this method has the better detection performance and estimation accuracy than other approaches. It is applicable for the target capture under low SNR in the space-based early warning system.
2007, 29(11): 2679-2682.
doi: 10.3724/SP.J.1146.2006.00556
Abstract:
Multisensor measurement fusion technology can improve the accuracy, reliability, and continuity when it is applied to parameters estimation. A new algorithm for orbit parameters estimation of formation flying satellites is proposed based on extend Kalman filter, and multisensor measurement fusion technology is also used. Derived from motion equation of absolute satellite orbit, the algorithm overcomes the localizations of Hill equation, in which many assumes are not met actually and is not suitable for the model with perturbations considered. Simulation results verify the feasibility and validity of the algorithm.
Multisensor measurement fusion technology can improve the accuracy, reliability, and continuity when it is applied to parameters estimation. A new algorithm for orbit parameters estimation of formation flying satellites is proposed based on extend Kalman filter, and multisensor measurement fusion technology is also used. Derived from motion equation of absolute satellite orbit, the algorithm overcomes the localizations of Hill equation, in which many assumes are not met actually and is not suitable for the model with perturbations considered. Simulation results verify the feasibility and validity of the algorithm.
2007, 29(11): 2683-2687.
doi: 10.3724/SP.J.1146.2006.00638
Abstract:
A new multi-objective optimization algorithm based on marginal distribution estimation is proposed, in which marginal probability distribution of the selected better individuals is estimated and is used to guide the search of Pareto optimal solutions of the multi-objective optimization problems. Combined with non-dominant ranking, diversity preserving technique based on crowding mechanism, tournament selection based on non-dominant ranking, and elitist strategy, the algorithm achieves a good balance between convergence and diversity. A set of typical test functions are used to evaluate the performance of the proposed algorithm, and comparison is made between some well-known multi-objective optimization algorithms, i.e. NSGA-II, SPEA, PAES. The experimental results show that the proposed algorithm can achieve a good balance between convergence and diversity, and is suited to complex multi-objective problems.
A new multi-objective optimization algorithm based on marginal distribution estimation is proposed, in which marginal probability distribution of the selected better individuals is estimated and is used to guide the search of Pareto optimal solutions of the multi-objective optimization problems. Combined with non-dominant ranking, diversity preserving technique based on crowding mechanism, tournament selection based on non-dominant ranking, and elitist strategy, the algorithm achieves a good balance between convergence and diversity. A set of typical test functions are used to evaluate the performance of the proposed algorithm, and comparison is made between some well-known multi-objective optimization algorithms, i.e. NSGA-II, SPEA, PAES. The experimental results show that the proposed algorithm can achieve a good balance between convergence and diversity, and is suited to complex multi-objective problems.
2007, 29(11): 2688-2692.
doi: 10.3724/SP.J.1146.2006.00457
Abstract:
How causes the algorithm fast to restrain to the true Pareto optimal front, and maintains solutions distributed uniformly in the Pareto optimal front is one of the key research issue. A multi-objective optimization algorithm is proposed based on Q-bit Coding Genetic Algorithm (QCGA). By right of the capability of efficient global search and maintenance of diversity of QGA, it explores the feasible region for Pareto optimal solutions quickly and maintains the solutions distributed uniformly over the Pareto optimal front. Characteristics of the algorithm are confirmed through optimization experiments of multi-objective functions with constraints. Compared with several well-known algorithms such as NSGAII, PAES, MOPSO, experiment results prove the algorithm validity and efficiency.
How causes the algorithm fast to restrain to the true Pareto optimal front, and maintains solutions distributed uniformly in the Pareto optimal front is one of the key research issue. A multi-objective optimization algorithm is proposed based on Q-bit Coding Genetic Algorithm (QCGA). By right of the capability of efficient global search and maintenance of diversity of QGA, it explores the feasible region for Pareto optimal solutions quickly and maintains the solutions distributed uniformly over the Pareto optimal front. Characteristics of the algorithm are confirmed through optimization experiments of multi-objective functions with constraints. Compared with several well-known algorithms such as NSGAII, PAES, MOPSO, experiment results prove the algorithm validity and efficiency.
2007, 29(11): 2693-2697.
doi: 10.3724/SP.J.1146.2006.00614
Abstract:
The DNA solution of the Maximum Weighted Independent Set (MWIS) problem based on biological technology is primarily presented in this paper. The MWIS problem is a well-known NP complete problem. The crucial point in the algorithm is to use of direct proportional length-based DNA strands to encode the vertices in weighed graphs and POA to build complete data pool, respectively, then the result comes out by a series of biological reaction and computation such as denaturation, anneal, Polymerase Chain Reaction(PCR), gel electrophoresis. And the maximum weighted independent set of the graph is found. Finally, the computer program is given to simulate this algorithm and the MWIS of the graph is also found , and the feasibility of the algorithm is validated and summarized.
The DNA solution of the Maximum Weighted Independent Set (MWIS) problem based on biological technology is primarily presented in this paper. The MWIS problem is a well-known NP complete problem. The crucial point in the algorithm is to use of direct proportional length-based DNA strands to encode the vertices in weighed graphs and POA to build complete data pool, respectively, then the result comes out by a series of biological reaction and computation such as denaturation, anneal, Polymerase Chain Reaction(PCR), gel electrophoresis. And the maximum weighted independent set of the graph is found. Finally, the computer program is given to simulate this algorithm and the MWIS of the graph is also found , and the feasibility of the algorithm is validated and summarized.
2007, 29(11): 2698-2701.
doi: 10.3724/SP.J.1146.2006.00577
Abstract:
An algorithm for estimating full aperture by sparse data is proposed in this paper. For big vacant aperture in sparse data, by measuring sparse data actually, accurate sparse data frequency domain energy distribution estimate can be obtained with parametric approaches. With estimated power spectrum as prior information, minimum weighting norm as the restraint, underdetermined equations are solved to interpolate vacant aperture, thus wide aperture data segment estimate is obtained. This algorithm can be effectively applied to SAR imaging in sparse data. Resulting simulation and actual data processing results confirm validity of the proposed algorithm.
An algorithm for estimating full aperture by sparse data is proposed in this paper. For big vacant aperture in sparse data, by measuring sparse data actually, accurate sparse data frequency domain energy distribution estimate can be obtained with parametric approaches. With estimated power spectrum as prior information, minimum weighting norm as the restraint, underdetermined equations are solved to interpolate vacant aperture, thus wide aperture data segment estimate is obtained. This algorithm can be effectively applied to SAR imaging in sparse data. Resulting simulation and actual data processing results confirm validity of the proposed algorithm.
2007, 29(11): 2702-2705.
doi: 10.3724/SP.J.1146.2006.00630
Abstract:
The development of bistatic focusing algorithm is a pivotal issue, which is still in progress and not sufficiently solved. This paper firstly describes the special case of equal velocity vectors and parallel flight paths of transmitter and receiver, and then makes detailed and mathematical study on the approximate bistatic-to-monostatic application. Based on the Bistatic-To-Monostatic Application (BTMA), the bistatic imaging can be processed with a Standard SAR Processor, and then the conventional CS, ECS algorithm are also applicable to the bistatic imaging, which are all testified by the simulation in the paper. As a result, based on BTMA, the imaging of the bistatic SAR with parallel track can be solved.
The development of bistatic focusing algorithm is a pivotal issue, which is still in progress and not sufficiently solved. This paper firstly describes the special case of equal velocity vectors and parallel flight paths of transmitter and receiver, and then makes detailed and mathematical study on the approximate bistatic-to-monostatic application. Based on the Bistatic-To-Monostatic Application (BTMA), the bistatic imaging can be processed with a Standard SAR Processor, and then the conventional CS, ECS algorithm are also applicable to the bistatic imaging, which are all testified by the simulation in the paper. As a result, based on BTMA, the imaging of the bistatic SAR with parallel track can be solved.
2007, 29(11): 2706-2710.
doi: 10.3724/SP.J.1146.2006.00428
Abstract:
Noise in the interferogram hinders the processing of two-dimensional phase unwrapping, and decreases the accuracy of the final DEM products. In this paper a interferometric phase noise reduction algorithm, in the stationary wavelet domain, is proposed. The algorithm chooses threshold of wavelet coefficients adaptively by using Bayesian method, and adaptively selects the best scale of two dimensional stationary wavelet transform for filtering. By using both simulated and SIR-C/X SAR generated interferograms, the performance of the algorithm is demonstrated and compared with the mean filter, the median filter and the Goldstein filter. By processing the simulated data, it is proved that the algorithm can get a result with better RMS and coherence. By using the algorithm, the residue number of real data reduced from 30430 to 113, far below the other methods. The result shows that the algorithm can preserve the fringes better, and filter the phase noise more effectively by reducing the number of residues. And the algorithm has some advantages over the Goldstein filter.
Noise in the interferogram hinders the processing of two-dimensional phase unwrapping, and decreases the accuracy of the final DEM products. In this paper a interferometric phase noise reduction algorithm, in the stationary wavelet domain, is proposed. The algorithm chooses threshold of wavelet coefficients adaptively by using Bayesian method, and adaptively selects the best scale of two dimensional stationary wavelet transform for filtering. By using both simulated and SIR-C/X SAR generated interferograms, the performance of the algorithm is demonstrated and compared with the mean filter, the median filter and the Goldstein filter. By processing the simulated data, it is proved that the algorithm can get a result with better RMS and coherence. By using the algorithm, the residue number of real data reduced from 30430 to 113, far below the other methods. The result shows that the algorithm can preserve the fringes better, and filter the phase noise more effectively by reducing the number of residues. And the algorithm has some advantages over the Goldstein filter.
2007, 29(11): 2711-2714.
doi: 10.3724/SP.J.1146.2006.00391
Abstract:
The method of measuring deep soil moisture by VHF/UHF dual frequency multiple polarization Synthetic Aperture Radar (SAR) consisting of vector network analyzer is proposed. The backscattering mechanism of vegetation and soil at depth, dielectric properties of soil are presented. The simulation results of the backscattering of multilayered soil, dielectric properties of soil are given and the models are validated by special case of single layered soil.
The method of measuring deep soil moisture by VHF/UHF dual frequency multiple polarization Synthetic Aperture Radar (SAR) consisting of vector network analyzer is proposed. The backscattering mechanism of vegetation and soil at depth, dielectric properties of soil are presented. The simulation results of the backscattering of multilayered soil, dielectric properties of soil are given and the models are validated by special case of single layered soil.
2007, 29(11): 2715-2719.
doi: 10.3724/SP.J.1146.2006.00538
Abstract:
When high resolution radar observes rough sea surface with low grazing angle the level of sea clutter increases obviously and the sea spike phenomena appears. It is not accurate to analyze the radar echo including stationary sea clutter, spike and target with the conventional statistical model based on single Probability Density Function (PDF). In this paper, the Continuous Hidden Markov Model (CHMM) is used to model and analyze the sea clutter. The echoes from sea surface are divided into three states of CHMM stationary sea clutter, sea spike and target. The Gaussian Mixture Density Model (GMDM) and the Baum-Welch algorithm are used to construct the PDF expressions of the observations of the three states and re-estimate the CHMM parameters, respectively. At the same time, the expressing of the observation-state joint probability is modified to avoid the underflow of the denominator during the iterative procedure of the GMDM parameters. Thus, a new method is proposed for modeling and analyzing sea clutter.
When high resolution radar observes rough sea surface with low grazing angle the level of sea clutter increases obviously and the sea spike phenomena appears. It is not accurate to analyze the radar echo including stationary sea clutter, spike and target with the conventional statistical model based on single Probability Density Function (PDF). In this paper, the Continuous Hidden Markov Model (CHMM) is used to model and analyze the sea clutter. The echoes from sea surface are divided into three states of CHMM stationary sea clutter, sea spike and target. The Gaussian Mixture Density Model (GMDM) and the Baum-Welch algorithm are used to construct the PDF expressions of the observations of the three states and re-estimate the CHMM parameters, respectively. At the same time, the expressing of the observation-state joint probability is modified to avoid the underflow of the denominator during the iterative procedure of the GMDM parameters. Thus, a new method is proposed for modeling and analyzing sea clutter.
2007, 29(11): 2720-2724.
doi: 10.3724/SP.J.1146.2006.00584
Abstract:
A variable discretization precision rough logic neural network is proposed to solve contradiction between network precision and the size of network as well as generalization ability. Based on the approximation area partition, the universe discussed can be partitioned into certain area and possibility area. The important reason of misclassification is the granularity of the possibility area is too coarse. In this work, only possibility area is refined and the precision of the rough logic neural network is improved while the size of network is restrained. In the experiment of the remote sensing image classification about Changbai mountain area, the performance of conventional method is best when the discretization level is 7. The most approximated result is acquired, while less network cost and training time are expended, when this method is used.
A variable discretization precision rough logic neural network is proposed to solve contradiction between network precision and the size of network as well as generalization ability. Based on the approximation area partition, the universe discussed can be partitioned into certain area and possibility area. The important reason of misclassification is the granularity of the possibility area is too coarse. In this work, only possibility area is refined and the precision of the rough logic neural network is improved while the size of network is restrained. In the experiment of the remote sensing image classification about Changbai mountain area, the performance of conventional method is best when the discretization level is 7. The most approximated result is acquired, while less network cost and training time are expended, when this method is used.
2007, 29(11): 2725-2728.
doi: 10.3724/SP.J.1146.2006.00593
Abstract:
The simulation of brightness temperature image is a necessary work in the passive microwave remote sensing. This paper introduces the brightness temperature tracing method for 3-D scene microwave radiometric image simulation, and describes the general requirements and considerations such as sky radiation, antenna smoothing and polarization rotation caused by multiple-reflection. Then a simulation model is established which can create more realistic imagery and reproduce the radiation phenomenology. Using this model the microwave radiometric phenomenology which is greatly deferent from optical and infrared ones is analyzed. Finally, the Lab building and airstrip are simulated in order to validate this model. The comparisons with field measurements indicate that this model is completely feasible in practice.
The simulation of brightness temperature image is a necessary work in the passive microwave remote sensing. This paper introduces the brightness temperature tracing method for 3-D scene microwave radiometric image simulation, and describes the general requirements and considerations such as sky radiation, antenna smoothing and polarization rotation caused by multiple-reflection. Then a simulation model is established which can create more realistic imagery and reproduce the radiation phenomenology. Using this model the microwave radiometric phenomenology which is greatly deferent from optical and infrared ones is analyzed. Finally, the Lab building and airstrip are simulated in order to validate this model. The comparisons with field measurements indicate that this model is completely feasible in practice.
2007, 29(11): 2729-2733.
doi: 10.3724/SP.J.1146.2006.00522
Abstract:
In this paper, the general noise jamming, cheat jamming and a novel similar clutter jamming method are discussed. From the viewpoint of the jamming power, the precision of leading parameters and the jamming effect, the matched jamming is proposed after the theory analysis. Both the theory analysis and simulation, bring the same conclusion that the similar clutter jamming method based on the multidimensional digital modulation, matches the SARs receiver and possesses the similar statistical characteristic with the SAR background clutter. It can partly overcome SARs high processing gain and requires moderate precision of leading parameters. Therefore, it is the realizable jamming method presently.
In this paper, the general noise jamming, cheat jamming and a novel similar clutter jamming method are discussed. From the viewpoint of the jamming power, the precision of leading parameters and the jamming effect, the matched jamming is proposed after the theory analysis. Both the theory analysis and simulation, bring the same conclusion that the similar clutter jamming method based on the multidimensional digital modulation, matches the SARs receiver and possesses the similar statistical characteristic with the SAR background clutter. It can partly overcome SARs high processing gain and requires moderate precision of leading parameters. Therefore, it is the realizable jamming method presently.
2007, 29(11): 2734-2737.
doi: 10.3724/SP.J.1146.2006.00365
Abstract:
In comparison with the Extended Kalman Filtering (EKF) algorithm, the Auxiliary Variable Particle Filtering (AVPF) algorithm is exploited in this paper to solve the problem of TMA based on Bearing-Only measurements (BO-TMA). Firstly, the problem of nonlinear filtering is identified in nature as the groundwork embedded in TMA. The PF (Particle Filtering) and the AVPF algorithms are then introduced, including their design consideration and elements of algorithms. Particular attention is paid to the problem of single observer air-to-sea BO-TMA. The discrete-time models are formulated pertinent to the nonlinear filtering problem and a typical scenario is depicted. The contrast results of Monte Carlo simulations between the AVPF and EKF have demonstrated that AVPF is more feasible to the air-to-sea BO-TMA by virtue of its favorable consistency with higher accuracy and better convergence.
In comparison with the Extended Kalman Filtering (EKF) algorithm, the Auxiliary Variable Particle Filtering (AVPF) algorithm is exploited in this paper to solve the problem of TMA based on Bearing-Only measurements (BO-TMA). Firstly, the problem of nonlinear filtering is identified in nature as the groundwork embedded in TMA. The PF (Particle Filtering) and the AVPF algorithms are then introduced, including their design consideration and elements of algorithms. Particular attention is paid to the problem of single observer air-to-sea BO-TMA. The discrete-time models are formulated pertinent to the nonlinear filtering problem and a typical scenario is depicted. The contrast results of Monte Carlo simulations between the AVPF and EKF have demonstrated that AVPF is more feasible to the air-to-sea BO-TMA by virtue of its favorable consistency with higher accuracy and better convergence.
2007, 29(11): 2738-2742.
doi: 10.3724/SP.J.1146.2006.00633
Abstract:
A new method based on third-order cyclic moment is presented for joint estimation of Directions-Of-Arrival (DOAs) and range of near-field sources. By exploiting the cyclostationarity and space-time information of the signals, the parameters are directly given by the eigendecomposition of certain constructed DOA-matrix. Compared with several existing approaches, the loss of array aperture is voided since the proposed method doesnt need a symmetrical array. Moreover, the proposed method can effectively suppress the additive stationary noises with any distribution and interfering signals with different cyclic frequency, and the parameters match automatically in the process. Some numerical simulations illustrate the effectiveness of the proposed algorithm.
A new method based on third-order cyclic moment is presented for joint estimation of Directions-Of-Arrival (DOAs) and range of near-field sources. By exploiting the cyclostationarity and space-time information of the signals, the parameters are directly given by the eigendecomposition of certain constructed DOA-matrix. Compared with several existing approaches, the loss of array aperture is voided since the proposed method doesnt need a symmetrical array. Moreover, the proposed method can effectively suppress the additive stationary noises with any distribution and interfering signals with different cyclic frequency, and the parameters match automatically in the process. Some numerical simulations illustrate the effectiveness of the proposed algorithm.
2007, 29(11): 2743-2746.
doi: 10.3724/SP.J.1146.2006.00533
Abstract:
A monopulse reflector antenna with an illuminator of six elements circular array is studied. The antenna has features of broadband and dual circular polarization performance. The output signals of the antenna are similar to multimode circular waveguide feed with one sum pattern and one difference pattern. The method for conveting the two channel signals to one channel signal is provided. The six log-periodic monopole antennas (LPMA) illuminator, diplexer, beam form network (BFN), single channel modulator (SCM) of a L/S dual band tracking antenna are introduced. The gain of sum pattern of 22.9dB, 30.1dB, zero-depth of difference pattern of 35dB, 40dB at 1.1GHz, 2.2GHz respectively are achieved with a 3.2m reflector. The antenna can auto-tracking beacon stably in the L/S bands.
A monopulse reflector antenna with an illuminator of six elements circular array is studied. The antenna has features of broadband and dual circular polarization performance. The output signals of the antenna are similar to multimode circular waveguide feed with one sum pattern and one difference pattern. The method for conveting the two channel signals to one channel signal is provided. The six log-periodic monopole antennas (LPMA) illuminator, diplexer, beam form network (BFN), single channel modulator (SCM) of a L/S dual band tracking antenna are introduced. The gain of sum pattern of 22.9dB, 30.1dB, zero-depth of difference pattern of 35dB, 40dB at 1.1GHz, 2.2GHz respectively are achieved with a 3.2m reflector. The antenna can auto-tracking beacon stably in the L/S bands.
2007, 29(11): 2747-2750.
doi: 10.3724/SP.J.1146.2006.00504
Abstract:
A novel Left-Handed Transmission Lines (LHTLs) based on coaxial waveguide is presented, compared with the LHTLs based on microstrip, the new structure has higher operating frequency, lower loss and higher power capability; compared with the LHTLs based on coaxial waveguide and rectangular waveguide presented recently, it has a simpler structure and is more easily to realize; The results of equivalent circuit method and finite element simulation show that the structure exhibits obvious left-handed behavior in a specific frequency range.
A novel Left-Handed Transmission Lines (LHTLs) based on coaxial waveguide is presented, compared with the LHTLs based on microstrip, the new structure has higher operating frequency, lower loss and higher power capability; compared with the LHTLs based on coaxial waveguide and rectangular waveguide presented recently, it has a simpler structure and is more easily to realize; The results of equivalent circuit method and finite element simulation show that the structure exhibits obvious left-handed behavior in a specific frequency range.
2007, 29(11): 2751-2753.
doi: 10.3724/SP.J.1146.2005.01348
Abstract:
In order to make the microstrip equalizer matchs the given attenuation curve respectively ,it should be attenuation adjustable and quality factor adjustable besides frequency adjustable. So in this paper, the novel thin-film resistor loaded microstrip resonator and its application to microstrip equalizer are investigated through numerical simulations and experiments, and the influence of thin-film resistor for microstrip equalizers transmission and standing wave character is studied. The results showed that the microstrip equalizer can be frequency adjustable by changing the dimension of the microstrip reaonator and it can be attenuation adjustable and quality factor adjustable by changing the location and resistance of the loaded thin-film resistors. The High Frequency Structure Simulator (HFSS) was used to simulate this thin-film resistor loaded resonator. Simulation and experiment results show that this thin-film resistor loaded resonator is suitable to microstrip equalizer. Finally a microstrip equalizer composed of this thin-film resistor loaded resonator is designed, fabricated and good results are obtained in the experiment.
In order to make the microstrip equalizer matchs the given attenuation curve respectively ,it should be attenuation adjustable and quality factor adjustable besides frequency adjustable. So in this paper, the novel thin-film resistor loaded microstrip resonator and its application to microstrip equalizer are investigated through numerical simulations and experiments, and the influence of thin-film resistor for microstrip equalizers transmission and standing wave character is studied. The results showed that the microstrip equalizer can be frequency adjustable by changing the dimension of the microstrip reaonator and it can be attenuation adjustable and quality factor adjustable by changing the location and resistance of the loaded thin-film resistors. The High Frequency Structure Simulator (HFSS) was used to simulate this thin-film resistor loaded resonator. Simulation and experiment results show that this thin-film resistor loaded resonator is suitable to microstrip equalizer. Finally a microstrip equalizer composed of this thin-film resistor loaded resonator is designed, fabricated and good results are obtained in the experiment.
2007, 29(11): 2754-2757.
doi: 10.3724/SP.J.1146.2006.00597
Abstract:
A new type of coupled cavity interaction circuit for harmonic multiplying gyrotron amplifier applications is proposed. Based on Ansoft HFSS software, the relation of the conversion coefficient from the rectangular waveguide TE□10 mode to the cylindrical waveguide TE○01 mode with geomitric parameters and frequency is calculated and analyzed, and the effect of the geomitric structure of the cavity on mode selection and suppression is discussed. Simulating results show that the energy conversion efficiency of more than 97% from the TE□10 mode to the TE○01 mode can be reached, and 3dB bandwidth is not less than 327MHz. The coupled cavity can be used as an input structure for harmonic multiplying gyrotron amplifier applications
A new type of coupled cavity interaction circuit for harmonic multiplying gyrotron amplifier applications is proposed. Based on Ansoft HFSS software, the relation of the conversion coefficient from the rectangular waveguide TE□10 mode to the cylindrical waveguide TE○01 mode with geomitric parameters and frequency is calculated and analyzed, and the effect of the geomitric structure of the cavity on mode selection and suppression is discussed. Simulating results show that the energy conversion efficiency of more than 97% from the TE□10 mode to the TE○01 mode can be reached, and 3dB bandwidth is not less than 327MHz. The coupled cavity can be used as an input structure for harmonic multiplying gyrotron amplifier applications
2007, 29(11): 2758-2761.
doi: 10.3724/SP.J.1146.2006.00486
Abstract:
The ill-conditioned normal equations bring numerical problems in construction of macromodel in time domain for power distribution networking using rational function approximation. This paper presents the superdefinite equations coefficient matrix can be decomposed in QR form using modified Gram-Schmidt orthogonal and the accurate passive macromodel in time domain can be constructed based on Bernoulli polynomial root finding method and the formulae for stability and passivity. Finally, a broadband passive macromodel constructed from DC to 1GHz is given to demonstrate the validity and accuracy of the method.
The ill-conditioned normal equations bring numerical problems in construction of macromodel in time domain for power distribution networking using rational function approximation. This paper presents the superdefinite equations coefficient matrix can be decomposed in QR form using modified Gram-Schmidt orthogonal and the accurate passive macromodel in time domain can be constructed based on Bernoulli polynomial root finding method and the formulae for stability and passivity. Finally, a broadband passive macromodel constructed from DC to 1GHz is given to demonstrate the validity and accuracy of the method.
2007, 29(11): 2762-2766.
doi: 10.3724/SP.J.1146.2006.00377
Abstract:
This paper proposes a new partition algorithm. The variable weight of the nets is introduced into the algorithm. Generally, the nodes connected to the nets are more than two in the hypergraph, so the probability gain model is used to enforce the effect of the increased weight of the nets. This algorithm can jump out of local minimal effectively when compared with original algorithm. The improvement is especially obvious for the large-scale circuits. For the gain value of the cell is floating-point, balanced binary tree is used to store the gain value of the cells, so the speed of this algorithm is several times slower than FM algorithm. The time complexity of this algorithm is O(P log2(n))(where P is the sum of the pins of all logic cells of the circuit, and n is the number of the circuit logic cells).
This paper proposes a new partition algorithm. The variable weight of the nets is introduced into the algorithm. Generally, the nodes connected to the nets are more than two in the hypergraph, so the probability gain model is used to enforce the effect of the increased weight of the nets. This algorithm can jump out of local minimal effectively when compared with original algorithm. The improvement is especially obvious for the large-scale circuits. For the gain value of the cell is floating-point, balanced binary tree is used to store the gain value of the cells, so the speed of this algorithm is several times slower than FM algorithm. The time complexity of this algorithm is O(P log2(n))(where P is the sum of the pins of all logic cells of the circuit, and n is the number of the circuit logic cells).
2007, 29(11): 2771-2774.
doi: 10.3724/SP.J.1146.2006.00547
Abstract:
A novel broadband microstrip antenna is presented. Double patch configuration is employed, and a circular metal is introduced on the top of the feed probe to counteract the inductance of the probe. As a result, the bandwidth of microstrip antenna is increased. Broadband microstrip antennas suitable for second generation and third generation mobile communication are fabricated, whose measurement results show that good bandwith characteristics are obtained, which can address the need of bandwidth for the mobile communication system.
A novel broadband microstrip antenna is presented. Double patch configuration is employed, and a circular metal is introduced on the top of the feed probe to counteract the inductance of the probe. As a result, the bandwidth of microstrip antenna is increased. Broadband microstrip antennas suitable for second generation and third generation mobile communication are fabricated, whose measurement results show that good bandwith characteristics are obtained, which can address the need of bandwidth for the mobile communication system.
2007, 29(11): 2775-2778.
doi: 10.3724/SP.J.1146.2006.00534
Abstract:
OFDM has received a considerable attention for realization of high-speed power line communications, and impulse noise is one of the main disturbances in power line. An optimization algorithm for impulsive noise mitigation in OFDM system is proposed based on the analysis of output SNR of blanking nonlinearity. Simulation results show that the proposed analysis provides very good prediction of the output SNR if the number of OFDM subcarriers is sufficiently large. For given impulsive index (A), there is a minimal optimum threshold. As the decrease of A, the minimal optimum threshold becomes larger. The output SNR and performance gain are functions of Signal to Impulsive Noise Ratio (SINR) respectively. Under lower and higher SINR, the output SNR changes linearly; and performance gain close to a fixed value respectively. But under middle SINR region, SNR and gain are nonlinear functions of SINR. The optimization algorithm proposed can improve the performance of impulse detection algorithm; furthermore, heighten the overall performance of the OFDM receiver in impulsive noise environment.
OFDM has received a considerable attention for realization of high-speed power line communications, and impulse noise is one of the main disturbances in power line. An optimization algorithm for impulsive noise mitigation in OFDM system is proposed based on the analysis of output SNR of blanking nonlinearity. Simulation results show that the proposed analysis provides very good prediction of the output SNR if the number of OFDM subcarriers is sufficiently large. For given impulsive index (A), there is a minimal optimum threshold. As the decrease of A, the minimal optimum threshold becomes larger. The output SNR and performance gain are functions of Signal to Impulsive Noise Ratio (SINR) respectively. Under lower and higher SINR, the output SNR changes linearly; and performance gain close to a fixed value respectively. But under middle SINR region, SNR and gain are nonlinear functions of SINR. The optimization algorithm proposed can improve the performance of impulse detection algorithm; furthermore, heighten the overall performance of the OFDM receiver in impulsive noise environment.
2007, 29(11): 2779-2782.
doi: 10.3724/SP.J.1146.2006.00492
Abstract:
The agorithm of RLS to suppress unknown narrowband interference is proposed by analyzing the received signalss statistical character when the narrowband interference is unknown in DS-SS systems. Compared with Blind Recursive Least-Square, it doesnt need limiting condition and reduces the complication.What is more, it makes up the shortcoming that the agorithm of LS cannot process the real-time signal, and is implemented with fast algorithms. The simulation results show that the performance to suppress narrowband inteference for DS-SS systems by the agorithm is better than the one of adaptive linear filter, and the convergence is not cared. Its easier to be applied.
The agorithm of RLS to suppress unknown narrowband interference is proposed by analyzing the received signalss statistical character when the narrowband interference is unknown in DS-SS systems. Compared with Blind Recursive Least-Square, it doesnt need limiting condition and reduces the complication.What is more, it makes up the shortcoming that the agorithm of LS cannot process the real-time signal, and is implemented with fast algorithms. The simulation results show that the performance to suppress narrowband inteference for DS-SS systems by the agorithm is better than the one of adaptive linear filter, and the convergence is not cared. Its easier to be applied.
2007, 29(11): 2783-2786.
doi: 10.3724/SP.J.1146.2006.00348
Abstract:
A Real-valued Discrete Gabor Transform (RDGT) based on DCT for finite sequences is proposed in this paper, which can be applied to both the critical sampling condition and the over-sampling condition. And the biorthogonal relationship between the analysis window and synthesis window for the transform is also proved in this paper. Because the DCT-based RDGT only involves real operations and can utilize fast DCT and IDCT algorithms for fast computation, it is easier in computation and implementation by hardware or software compared to the traditional DFT-based complex-valued discrete Gabor transform. The proposed transform can be used to improve the speed and efficiency in analyzing and processing nonstational or time-varying signals.
A Real-valued Discrete Gabor Transform (RDGT) based on DCT for finite sequences is proposed in this paper, which can be applied to both the critical sampling condition and the over-sampling condition. And the biorthogonal relationship between the analysis window and synthesis window for the transform is also proved in this paper. Because the DCT-based RDGT only involves real operations and can utilize fast DCT and IDCT algorithms for fast computation, it is easier in computation and implementation by hardware or software compared to the traditional DFT-based complex-valued discrete Gabor transform. The proposed transform can be used to improve the speed and efficiency in analyzing and processing nonstational or time-varying signals.
2007, 29(11): 2787-2790.
doi: 10.3724/SP.J.1146.2006.00585
Abstract:
The hybrid iterative Method of Moments and Physical-Optics method of moments (MoM-PO) is used to analyze radiation pattern of antenna around an electrically large platform modeled with Non-Uniform Rational B-Spline (NURBS) surfaces. The formula of scatter field based on NURBS surface is deduced. Stationary Phase Method (SPM) is applied to the integral of induced current on the rational Bezier surface. The process of obtaining stationary point is accelerated by interpolation technique. Results obtained by this method and by MoM-PO based on triangle facet model agree well while the former is more efficient in execution time.
The hybrid iterative Method of Moments and Physical-Optics method of moments (MoM-PO) is used to analyze radiation pattern of antenna around an electrically large platform modeled with Non-Uniform Rational B-Spline (NURBS) surfaces. The formula of scatter field based on NURBS surface is deduced. Stationary Phase Method (SPM) is applied to the integral of induced current on the rational Bezier surface. The process of obtaining stationary point is accelerated by interpolation technique. Results obtained by this method and by MoM-PO based on triangle facet model agree well while the former is more efficient in execution time.
2007, 29(11): 2791-2794.
doi: 10.3724/SP.J.1146.2006.01196
Abstract:
A mixed-mode AGC is proposed in this paper. The peak value of the output signal is detected by an analog peak detector. The detected peak is then processed by the following comparator and control logic. The gain of the VGA is controlled by the output of the control logic. The AGC is designed based on 0.25m standard CMOS technology. The supply voltage is 2.5V. The simulation results show that the amplitude of the output signal is 800mV25mV when the input amplitude ranges from 100mV to 1.3V. The THD of the output signal is less than 45dB when the input amplitude is 1V, and the power consumption is 10mW.
A mixed-mode AGC is proposed in this paper. The peak value of the output signal is detected by an analog peak detector. The detected peak is then processed by the following comparator and control logic. The gain of the VGA is controlled by the output of the control logic. The AGC is designed based on 0.25m standard CMOS technology. The supply voltage is 2.5V. The simulation results show that the amplitude of the output signal is 800mV25mV when the input amplitude ranges from 100mV to 1.3V. The THD of the output signal is less than 45dB when the input amplitude is 1V, and the power consumption is 10mW.
2007, 29(11): 2767-2770.
doi: 10.3724/SP.J.1146.2007.00457
Abstract:
IP micro-mobility is one of the mobility management methods that can improve the communication quality during movement of mobile nodes. Handoff management is its key technology. In this paper, a comprehensive survey on IP micro-mobility handoff management is given. A new classification of handoff management, from the viewpoint of relationship and interaction between network-level handoff and data-link-level handoff, is introduced. Further, the characteristics and problems of some representative IP micro-mobility handoff protocols are analyzed in detail, and the comparison results are given also. Finally, future research directions of IP micro-mobility handoff management are discussed.
IP micro-mobility is one of the mobility management methods that can improve the communication quality during movement of mobile nodes. Handoff management is its key technology. In this paper, a comprehensive survey on IP micro-mobility handoff management is given. A new classification of handoff management, from the viewpoint of relationship and interaction between network-level handoff and data-link-level handoff, is introduced. Further, the characteristics and problems of some representative IP micro-mobility handoff protocols are analyzed in detail, and the comparison results are given also. Finally, future research directions of IP micro-mobility handoff management are discussed.
