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2008 Vol. 30, No. 11
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2008, 30(11): 2541-2546.
doi: 10.3724/SP.J.1146.2007.01812
Abstract:
NLOS propagation is a main source of ranging error for IR-UWB localization systems. To mitigate the NLOS effects, a NLOS identification method which do not need accurate channel estimation process is proposed in this paper. Metrics are directly extracted from the received signal samples to identify the channel state. In this paper, product of DP-to-average and peak-to-average is constructed as the identification metric, whose performance is compared to conventional metrics including kurtosis and the mean excess delay. Simulation results show that performance corresponding to coherent ranging is better than that corresponding to non-coherent ranging, which is mainly due to the more accurate DP detection results and the higher sampling rate of coherent ranging. Performance comparison demonstrates that both kurtosis and the mean excess delay cannot obtain satisfying results, while using the product of DP-to-average and peak-to-average can increase the identification success ratio nearly 10 percent. Localization accuracy is expected to be improved by incorporating the NLOS identification results into the positioning module.
NLOS propagation is a main source of ranging error for IR-UWB localization systems. To mitigate the NLOS effects, a NLOS identification method which do not need accurate channel estimation process is proposed in this paper. Metrics are directly extracted from the received signal samples to identify the channel state. In this paper, product of DP-to-average and peak-to-average is constructed as the identification metric, whose performance is compared to conventional metrics including kurtosis and the mean excess delay. Simulation results show that performance corresponding to coherent ranging is better than that corresponding to non-coherent ranging, which is mainly due to the more accurate DP detection results and the higher sampling rate of coherent ranging. Performance comparison demonstrates that both kurtosis and the mean excess delay cannot obtain satisfying results, while using the product of DP-to-average and peak-to-average can increase the identification success ratio nearly 10 percent. Localization accuracy is expected to be improved by incorporating the NLOS identification results into the positioning module.
2008, 30(11): 2547-2551.
doi: 10.3724/SP.J.1146.2007.00736
Abstract:
Based on the non-regenerative relaying mode, the capacity of the two-hop relaying system is analyzed based on Orthogonal Frequency Division Multiplex (OFDM), and the analysis is extended to the scenario with two antennas in transmitter using Space Time Block Coding (STBC). Taking the maximum end-to-end data rate as the optimization criterion, the two-hop subcarrier pairing theorem is proposed, and the joint optimization is investigated across frequency domain, space domain as well as space-frequency planar domain respectively combined with the water-filling theory. The simulation results show that the proposed joint optimization scheme can improve the system capacity obviously compared with the uniform resource allocation scheme, and STBC-OFDM scheme can achieve performance gain. The proposed two-hop subcarrier pairing strategy can enhance the system performance further.
Based on the non-regenerative relaying mode, the capacity of the two-hop relaying system is analyzed based on Orthogonal Frequency Division Multiplex (OFDM), and the analysis is extended to the scenario with two antennas in transmitter using Space Time Block Coding (STBC). Taking the maximum end-to-end data rate as the optimization criterion, the two-hop subcarrier pairing theorem is proposed, and the joint optimization is investigated across frequency domain, space domain as well as space-frequency planar domain respectively combined with the water-filling theory. The simulation results show that the proposed joint optimization scheme can improve the system capacity obviously compared with the uniform resource allocation scheme, and STBC-OFDM scheme can achieve performance gain. The proposed two-hop subcarrier pairing strategy can enhance the system performance further.
2008, 30(11): 2552-2555.
doi: 10.3724/SP.J.1146.2007.00585
Abstract:
This paper firstly introduces a new architecture of two-hop-relay WCDMA cellular system, and builds the analytical model of this system. Then based on this model, the average downlink transmission rate and the call blocking probability of packets of the system are obtained respectively. Finally, through numerical calculation, the impact of the various parameters on the performance of the two-hop-relay WCDMA cellular systems is analyzed, and the systems performance is compared with the traditional WCDMA cellular systems without relaying and the two-hop-relay WCDMA cellular systems with congestion control.
This paper firstly introduces a new architecture of two-hop-relay WCDMA cellular system, and builds the analytical model of this system. Then based on this model, the average downlink transmission rate and the call blocking probability of packets of the system are obtained respectively. Finally, through numerical calculation, the impact of the various parameters on the performance of the two-hop-relay WCDMA cellular systems is analyzed, and the systems performance is compared with the traditional WCDMA cellular systems without relaying and the two-hop-relay WCDMA cellular systems with congestion control.
2008, 30(11): 2556-2560.
doi: 10.3724/SP.J.1146.2007.00568
Abstract:
Key techniques and the advanced RRM (Radio Resource Management) algorithms in LCR TDD systems are researched in this paper. An scheduling algorithm based on rate-prediction is proposed. In order to compare these technique functions, different scheduling strategies combined with SA (Smart Antenna) or JD (Joint Detection), which improve the throughput of packet traffics are simulated in dynamic system layer simulation. As some curves are obtained, new RRM algorithm with both SA and JD can not only balance the opportunity of all users, but also keep the throughput of users in cross slots at a high level.
Key techniques and the advanced RRM (Radio Resource Management) algorithms in LCR TDD systems are researched in this paper. An scheduling algorithm based on rate-prediction is proposed. In order to compare these technique functions, different scheduling strategies combined with SA (Smart Antenna) or JD (Joint Detection), which improve the throughput of packet traffics are simulated in dynamic system layer simulation. As some curves are obtained, new RRM algorithm with both SA and JD can not only balance the opportunity of all users, but also keep the throughput of users in cross slots at a high level.
2008, 30(11): 2561-2564.
doi: 10.3724/SP.J.1146.2007.00624
Abstract:
In this paper, system RoT and a novel intercell interference control scheme for TD-SCDMA HSUPA(High-Speed Uplink Packet Access) based on system RoT is presented. The scheme controls the user admission and the resource distribution according to the information of users geometry. System simulation results proves that this scheme improves the system performance.
In this paper, system RoT and a novel intercell interference control scheme for TD-SCDMA HSUPA(High-Speed Uplink Packet Access) based on system RoT is presented. The scheme controls the user admission and the resource distribution according to the information of users geometry. System simulation results proves that this scheme improves the system performance.
2008, 30(11): 2565-2569.
doi: 10.3724/SP.J.1146.2007.00680
Abstract:
A double parameters cross-layer adaptive resource allocation scheme for multiuser OFDM system with heterogeneous types of traffic is proposed in this paper. By dynamically adjusting values of the two parameters: delay compensatory factor and throughput compensatory factor respectively, existing scheduling algorithms can be utilized flexibly and efficiently in the OFDM system. Simulations show that the scheme can achieve diverse levels of tradeoff between system power efficiency and traffic QoS satisfaction flexibly and fairness among different types of traffic can be guaranteed.
A double parameters cross-layer adaptive resource allocation scheme for multiuser OFDM system with heterogeneous types of traffic is proposed in this paper. By dynamically adjusting values of the two parameters: delay compensatory factor and throughput compensatory factor respectively, existing scheduling algorithms can be utilized flexibly and efficiently in the OFDM system. Simulations show that the scheme can achieve diverse levels of tradeoff between system power efficiency and traffic QoS satisfaction flexibly and fairness among different types of traffic can be guaranteed.
2008, 30(11): 2570-2574.
doi: 10.3724/SP.J.1146.2007.00846
Abstract:
Multiuser diversity can significantly improve wireless communication system performance by exploiting the feedback information that conveys the channel quality. In Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM) structure, the per subcarrier of per user feedback expenses a substantial amount of wireless resource and decreases spectrum efficiency, so various limited channel feedback scheme is proposed to reduce the feedback load. In this paper, the multiuser diversity gain based on two representative limited channel feedback is investigated, and it is compared with ideal feedback. The close-form expression of average spectrum efficiency is deduced with considering a discrete finite set of candidate constellation sizes for practical system. Extensive simulations are presented to evaluate the multiuser diversity performance in various feedback scheme and the results match with the numeral analysis very well. The limited feedback schemes can reduce the feedback load greatly with no loss in terms of multiuser diversity gain only if the feedback parameters are chosen properly, which provides the instruction to design the channel feedback of practical system.
Multiuser diversity can significantly improve wireless communication system performance by exploiting the feedback information that conveys the channel quality. In Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM) structure, the per subcarrier of per user feedback expenses a substantial amount of wireless resource and decreases spectrum efficiency, so various limited channel feedback scheme is proposed to reduce the feedback load. In this paper, the multiuser diversity gain based on two representative limited channel feedback is investigated, and it is compared with ideal feedback. The close-form expression of average spectrum efficiency is deduced with considering a discrete finite set of candidate constellation sizes for practical system. Extensive simulations are presented to evaluate the multiuser diversity performance in various feedback scheme and the results match with the numeral analysis very well. The limited feedback schemes can reduce the feedback load greatly with no loss in terms of multiuser diversity gain only if the feedback parameters are chosen properly, which provides the instruction to design the channel feedback of practical system.
2008, 30(11): 2575-2579.
doi: 10.3724/SP.J.1146.2007.00740
Abstract:
To improve the porformance of Space-Time Block Code (STBC) over time-selective fading channels, the Coordinate Interleaved Space-Time Block Code (CISTBC) is proposed. Compared with the existing STBC, CISTBC sends the real and imaginary parts of each symbol from different antennas. This makes the best of the multi-path transmission resulted from the time-varing character of the channel coefficients and strengthens each symbols resistance to the deep fading. Moreover, from QR decompostion and gaussian approximation (GA), the impact of successive interference cancellation (SIC) algorithm on different symbols decoding performnance is analyzed. A Circular SIC (CSIC) algorithm to combat the error propagation and obtain an extra performance gain is developed. Analysis and simulations demonstrate that CISTBC can effectively improve the performance of STBC over time-selective fading channels.
To improve the porformance of Space-Time Block Code (STBC) over time-selective fading channels, the Coordinate Interleaved Space-Time Block Code (CISTBC) is proposed. Compared with the existing STBC, CISTBC sends the real and imaginary parts of each symbol from different antennas. This makes the best of the multi-path transmission resulted from the time-varing character of the channel coefficients and strengthens each symbols resistance to the deep fading. Moreover, from QR decompostion and gaussian approximation (GA), the impact of successive interference cancellation (SIC) algorithm on different symbols decoding performnance is analyzed. A Circular SIC (CSIC) algorithm to combat the error propagation and obtain an extra performance gain is developed. Analysis and simulations demonstrate that CISTBC can effectively improve the performance of STBC over time-selective fading channels.
2008, 30(11): 2580-2583.
doi: 10.3724/SP.J.1146.2007.00474
Abstract:
The space correlation is analyzed in different propagation conditions including the MIMO macro-cell and micro-cell applications. The characteristics curves describing the space correlation versus the distance of antennas are obtained according to the numerical analysis. The effect of the spread of the angle of arrival on the space correlation is also investigated. Besides, the impact of the space correlation on the system performances is discussed here. The thresholds of the space correlation coefficients influencing BER performance under different propagations are also found by BER analysis.
The space correlation is analyzed in different propagation conditions including the MIMO macro-cell and micro-cell applications. The characteristics curves describing the space correlation versus the distance of antennas are obtained according to the numerical analysis. The effect of the spread of the angle of arrival on the space correlation is also investigated. Besides, the impact of the space correlation on the system performances is discussed here. The thresholds of the space correlation coefficients influencing BER performance under different propagations are also found by BER analysis.
2008, 30(11): 2584-2587.
doi: 10.3724/SP.J.1146.2007.00790
Abstract:
For multiuser MISO downlink systems, an efficient user selection algorithm aiming to maximize the sum rate capacity is proposed in this paper. The number of selected users can change adaptively according to current channel condition. It achieves near optimal performance while with low computational complexity. Through simulation results, the excellent performance of the proposed algorithm is shown. Based on this method, a fair scheduling scheme is further given to ensure fairness to all users in the system.
For multiuser MISO downlink systems, an efficient user selection algorithm aiming to maximize the sum rate capacity is proposed in this paper. The number of selected users can change adaptively according to current channel condition. It achieves near optimal performance while with low computational complexity. Through simulation results, the excellent performance of the proposed algorithm is shown. Based on this method, a fair scheduling scheme is further given to ensure fairness to all users in the system.
2008, 30(11): 2588-2591.
doi: 10.3724/SP.J.1146.2007.00631
Abstract:
Considering the problem of key distribute between any two users in a network, we transform the coefficients of W state to be uniform in symmetrical form. A scheme for quantum key distribution in a network via W state is proposed. Certificate Authority (CA) and the two users who want to communicate with each other share the three particles of W state. CA performs a measurement on his own particle and promulgates the result of his measurement, two users create their key in corresponding ways according to the measurement result of CA. Then the security of the situation that exists an eavesdropper (Eve) or CA is unauthentic is discussed respectively. It is proved that this scheme can withstand the attack effectively, and carry out the academic efficiency that three W states can be used to gain two bits key.
Considering the problem of key distribute between any two users in a network, we transform the coefficients of W state to be uniform in symmetrical form. A scheme for quantum key distribution in a network via W state is proposed. Certificate Authority (CA) and the two users who want to communicate with each other share the three particles of W state. CA performs a measurement on his own particle and promulgates the result of his measurement, two users create their key in corresponding ways according to the measurement result of CA. Then the security of the situation that exists an eavesdropper (Eve) or CA is unauthentic is discussed respectively. It is proved that this scheme can withstand the attack effectively, and carry out the academic efficiency that three W states can be used to gain two bits key.
2008, 30(11): 2592-2595.
doi: 10.3724/SP.J.1146.2007.00711
Abstract:
In order to depict and study randomicity of sequences better, this correspondence gives the concept of k-error sequences of keystream, and for k=1,2, the counting function, i.e., the number of k-error sequences of 2n-periodic binary sequence, and the expected value of the number of 1-error sequences of 2n-periodic binary sequences are provided.
In order to depict and study randomicity of sequences better, this correspondence gives the concept of k-error sequences of keystream, and for k=1,2, the counting function, i.e., the number of k-error sequences of 2n-periodic binary sequence, and the expected value of the number of 1-error sequences of 2n-periodic binary sequences are provided.
2008, 30(11): 2596-2600.
doi: 10.3724/SP.J.1146.2008.00235
Abstract:
To determine the potential signaling traffic reductions, the session establishment procedures in IMS (IP Multimedia Subsystem) are investigated. The investigation showes that, the S-CSCF (Serving Call Session Control Function) is the major bottleneck in IMS network. To reduce the session setup delay and improve the system performance, a new Group based Service Triggering Algorithm (GSTA) is proposed. And then the modeling of 3GPP (3rd Generation Partnership Project) Service Triggering Algorithm (3GPP STA) and GSTA are presented. Theoretical analysis and simulation results show that, GSTA efficiently reduces the signaling traffic load at the S-CSCF, increases the throughput of the system and significantly reduces the session setup delay, improves IMS network quality of service.
To determine the potential signaling traffic reductions, the session establishment procedures in IMS (IP Multimedia Subsystem) are investigated. The investigation showes that, the S-CSCF (Serving Call Session Control Function) is the major bottleneck in IMS network. To reduce the session setup delay and improve the system performance, a new Group based Service Triggering Algorithm (GSTA) is proposed. And then the modeling of 3GPP (3rd Generation Partnership Project) Service Triggering Algorithm (3GPP STA) and GSTA are presented. Theoretical analysis and simulation results show that, GSTA efficiently reduces the signaling traffic load at the S-CSCF, increases the throughput of the system and significantly reduces the session setup delay, improves IMS network quality of service.
2008, 30(11): 2601-2604.
doi: 10.3724/SP.J.1146.2007.01757
Abstract:
Mobile WiMAX is an important technology for broadband wireless access. It has high-speed date transmission rate，great covering range, supporting several different service classes and some other merits. For the sake of guaranteeing every services QoS, a new access control algorithm based on game theory is proposed. The algorithm gives services different priorities firstly, and then formulates a non-cooperative two-person game. Finally it decides to accept or reject connect application and selects bandwidth reservation scheme by figuring out Nash Equilibrium. The simulation results show the algorithm can increase bandwidth utilization, reduce the blocking probabilities of new originated connections and the dropping probabilities of handover connections, and can provide differentiated services to distinct services.
Mobile WiMAX is an important technology for broadband wireless access. It has high-speed date transmission rate，great covering range, supporting several different service classes and some other merits. For the sake of guaranteeing every services QoS, a new access control algorithm based on game theory is proposed. The algorithm gives services different priorities firstly, and then formulates a non-cooperative two-person game. Finally it decides to accept or reject connect application and selects bandwidth reservation scheme by figuring out Nash Equilibrium. The simulation results show the algorithm can increase bandwidth utilization, reduce the blocking probabilities of new originated connections and the dropping probabilities of handover connections, and can provide differentiated services to distinct services.
2008, 30(11): 2605-2608.
doi: 10.3724/SP.J.1146.2007.00638
Abstract:
Multicast transmission is a key technology of the present communication system, which can send the same information simultaneously to several receivers. A new multicast routing algorithm based on network coding is proposed in this paper, searching the routing groups from source to each receiver by using Dijkstra reduction network. Simulation results show that, compared with traditional multicast routing algorithms, performances of the routing algorithm are improved at a great extent in resource consumption and load balance, and are closer to minimum-cost multicast algorithm based on network coding. Finally, mathematic analysis indicates that the algorithm has lower computational complexity.
Multicast transmission is a key technology of the present communication system, which can send the same information simultaneously to several receivers. A new multicast routing algorithm based on network coding is proposed in this paper, searching the routing groups from source to each receiver by using Dijkstra reduction network. Simulation results show that, compared with traditional multicast routing algorithms, performances of the routing algorithm are improved at a great extent in resource consumption and load balance, and are closer to minimum-cost multicast algorithm based on network coding. Finally, mathematic analysis indicates that the algorithm has lower computational complexity.
2008, 30(11): 2609-2612.
doi: 10.3724/SP.J.1146.2007.00650
Abstract:
A novel crank back mechanism based on re-routing in crank back node is proposed in ASON. This mechanism avoids the flow of crank back message when the crank back happened in connection establishment. To support this mechanism, function of component and procedure of signaling perform are extended. A test-platform of 15 nodes is built, it implement control plane of ASON by running RSVP-TE, OSPF-TE and LMP etc. The experimental results show that new mechanism has less connection setup time and network traffic than the traditional mechanism has.
A novel crank back mechanism based on re-routing in crank back node is proposed in ASON. This mechanism avoids the flow of crank back message when the crank back happened in connection establishment. To support this mechanism, function of component and procedure of signaling perform are extended. A test-platform of 15 nodes is built, it implement control plane of ASON by running RSVP-TE, OSPF-TE and LMP etc. The experimental results show that new mechanism has less connection setup time and network traffic than the traditional mechanism has.
2008, 30(11): 2613-2616.
doi: 10.3724/SP.J.1146.2008.00874
Abstract:
To make the agents negotiate more efficiently in multi-lateral multi-issue negotiation in multi-agent based competitive e-commerce, an agent negotiation model in competitive environment is presented, and the Adaptive Genetic Algorithm(AGA) is applied to the model to enhance the negotiation efficiency. In the experiments, two kinds of genetic algorithms are used to compare with, they are Standard Genetic Algorithm(SGA) and AGA. After 1000 times of experiments for the two kinds of agents to gain the satisfying result, SGA averagely needs negotiation of 183 runs, while the AGA averagely needs only 152 runs. The experiment results show that the AGA can gain the satisfying negotiation result more efficiently than SGA in competitive multi-lateral multi-issue negotiation.
To make the agents negotiate more efficiently in multi-lateral multi-issue negotiation in multi-agent based competitive e-commerce, an agent negotiation model in competitive environment is presented, and the Adaptive Genetic Algorithm(AGA) is applied to the model to enhance the negotiation efficiency. In the experiments, two kinds of genetic algorithms are used to compare with, they are Standard Genetic Algorithm(SGA) and AGA. After 1000 times of experiments for the two kinds of agents to gain the satisfying result, SGA averagely needs negotiation of 183 runs, while the AGA averagely needs only 152 runs. The experiment results show that the AGA can gain the satisfying negotiation result more efficiently than SGA in competitive multi-lateral multi-issue negotiation.
2008, 30(11): 2617-2621.
doi: 10.3724/SP.J.1146.2007.01756
Abstract:
Based on GSM EFR (Enhanced Full Rate) parameter redundancy, this paper proposes a new structure of joint source-channel decoding based on iterative channel decoder and parameter estimation. Based on the analysis of GSM EFR parameter redundancy, the paper presents the reasonable redundancy allocation strategy to arrange the two kinds of redundancy between the source decoder and channel decoder. Also, according to the characteristic of different speech coefficient, different estimation criterions are presented. Simulation results show that the algorithm of this paper improves the receiver performance significantly.
Based on GSM EFR (Enhanced Full Rate) parameter redundancy, this paper proposes a new structure of joint source-channel decoding based on iterative channel decoder and parameter estimation. Based on the analysis of GSM EFR parameter redundancy, the paper presents the reasonable redundancy allocation strategy to arrange the two kinds of redundancy between the source decoder and channel decoder. Also, according to the characteristic of different speech coefficient, different estimation criterions are presented. Simulation results show that the algorithm of this paper improves the receiver performance significantly.
2008, 30(11): 2622-2625.
doi: 10.3724/SP.J.1146.2007.00595
Abstract:
A new periodic correlation signal is presented, which is the perfect ternary sequence pair. The definitions of the perfect ternary sequence pair and its transformation properties are presented. A method for constructing the perfect ternary sequence pairs taking advantage of pseudorandom binary sequence, perfect binary sequence pair and the perfect punctured binary sequence pair is presented by us. As a result, it indicates that the method is handy and flexible. With this method more perfect signals could be obtained. These signals enrich the theory of sequence pair perfect discrete correlated signals.
A new periodic correlation signal is presented, which is the perfect ternary sequence pair. The definitions of the perfect ternary sequence pair and its transformation properties are presented. A method for constructing the perfect ternary sequence pairs taking advantage of pseudorandom binary sequence, perfect binary sequence pair and the perfect punctured binary sequence pair is presented by us. As a result, it indicates that the method is handy and flexible. With this method more perfect signals could be obtained. These signals enrich the theory of sequence pair perfect discrete correlated signals.
2008, 30(11): 2626-2629.
doi: 10.3724/SP.J.1146.2007.00738
Abstract:
Based on two arbitrary Hadamard matrices of common size, a new class of ternary sequence with aperiodic zero correlation zone is presented. Different from the construction given by Donelan and OFarrell, the proposed method can generate sequences with higher energy efficiency. Furthermore, two of this kind of sequence sets are constructed which are mutually orthogonal, so that the number of available sequences for a Qs-CDMA system is increased.
Based on two arbitrary Hadamard matrices of common size, a new class of ternary sequence with aperiodic zero correlation zone is presented. Different from the construction given by Donelan and OFarrell, the proposed method can generate sequences with higher energy efficiency. Furthermore, two of this kind of sequence sets are constructed which are mutually orthogonal, so that the number of available sequences for a Qs-CDMA system is increased.
2008, 30(11): 2630-2633.
doi: 10.3724/SP.J.1146.2007.00693
Abstract:
In this paper, a low-rate LDPC-PPM scheme is bring forward which can be applied into UWB communication systems. This scheme can provide good performance with low decoding complexity. By changing the mapping style from coded bits to modulated symbols, not only the iterative operations between decoding and demodulation can be avoided, but also Fast Hadamard Transformation (FHT) and the so called A Posteriori Probability FHT (APP-FHT) algorithm can be adopted to further decrease decoding complexity. It can be proved that this scheme is equivalent to low-rate LDPC-Hadamard codes with BPSK modulation. Simulation results show that this scheme can achieve -1.18dB at bit error rate with data length 65536, which is only worse 0.02dB than Turbo-Hadamard codes with BPSK modulation.
In this paper, a low-rate LDPC-PPM scheme is bring forward which can be applied into UWB communication systems. This scheme can provide good performance with low decoding complexity. By changing the mapping style from coded bits to modulated symbols, not only the iterative operations between decoding and demodulation can be avoided, but also Fast Hadamard Transformation (FHT) and the so called A Posteriori Probability FHT (APP-FHT) algorithm can be adopted to further decrease decoding complexity. It can be proved that this scheme is equivalent to low-rate LDPC-Hadamard codes with BPSK modulation. Simulation results show that this scheme can achieve -1.18dB at bit error rate with data length 65536, which is only worse 0.02dB than Turbo-Hadamard codes with BPSK modulation.
2008, 30(11): 2634-2637.
doi: 10.3724/SP.J.1146.2007.00642
Abstract:
Digital Fountain is a packet oriented FEC technology for erasure channels. And the performance of fountain codes is limited by the distribution of stopping sets. In the paper, a pair of bounds was proposed to estimate the decoding failure probability of finite length fountain codes. And a search algorithm of low complexity was presented to get the stopping set distribution. The comparisons show that the upper and lower bounds are very close to the simulation results.
Digital Fountain is a packet oriented FEC technology for erasure channels. And the performance of fountain codes is limited by the distribution of stopping sets. In the paper, a pair of bounds was proposed to estimate the decoding failure probability of finite length fountain codes. And a search algorithm of low complexity was presented to get the stopping set distribution. The comparisons show that the upper and lower bounds are very close to the simulation results.
2008, 30(11): 2638-2641.
doi: 10.3724/SP.J.1146.2007.01738
Abstract:
The usual in-band spectrum sensing in cognitive radio is performed without the interference from the network itself by quiet periods. In this paper, an In-band spectrum sensing method is proposed which can avoid the usage of quiet period to guarantee the performance of the network. In this method, the complementarity of adjacent OFDM symbols is utilized to perform energy detection. Furthermore, the performance of the algorithm is analyzed and this idea is extended to several applications. Simulation proves that the algorithm has a comparable performance with power detector with quiet period. And the algorithm can achieve an acceptable detection performance for IEEE802.22 system.
The usual in-band spectrum sensing in cognitive radio is performed without the interference from the network itself by quiet periods. In this paper, an In-band spectrum sensing method is proposed which can avoid the usage of quiet period to guarantee the performance of the network. In this method, the complementarity of adjacent OFDM symbols is utilized to perform energy detection. Furthermore, the performance of the algorithm is analyzed and this idea is extended to several applications. Simulation proves that the algorithm has a comparable performance with power detector with quiet period. And the algorithm can achieve an acceptable detection performance for IEEE802.22 system.
2008, 30(11): 2642-2645.
doi: 10.3724/SP.J.1146.2007.00645
Abstract:
Application of the non-linear post-processing method in improving the weak signal detection performance of the broadband Minimum Variance Distortionless Response (MVDR) is researched fully. The final spatial energy spectrum can be obtained by summing the reciprocal of the output power of every narrowband frequency bin. There is no need for the method proposed in this paper to know any prior information about the array noise and the target signal. The processing gain by this method compared to the general broadband MVDR can be obtained as long as the amplitude fluctuation of the array noise frequency spectrum is severer than that of the target signal. Based on the optimal signal detection theory, a method for analyzing the performance of the non-linear post-processing is also brought forward. Simulation and real data are used to validate the effectiveness of the non-linear post-processing method. Analysis results show that 3.5dB-6dB processing gain compared to the general broadband MVDR can be reached with the proposed method.
Application of the non-linear post-processing method in improving the weak signal detection performance of the broadband Minimum Variance Distortionless Response (MVDR) is researched fully. The final spatial energy spectrum can be obtained by summing the reciprocal of the output power of every narrowband frequency bin. There is no need for the method proposed in this paper to know any prior information about the array noise and the target signal. The processing gain by this method compared to the general broadband MVDR can be obtained as long as the amplitude fluctuation of the array noise frequency spectrum is severer than that of the target signal. Based on the optimal signal detection theory, a method for analyzing the performance of the non-linear post-processing is also brought forward. Simulation and real data are used to validate the effectiveness of the non-linear post-processing method. Analysis results show that 3.5dB-6dB processing gain compared to the general broadband MVDR can be reached with the proposed method.
2008, 30(11): 2646-2649.
doi: 10.3724/SP.J.1146.2007.00767
Abstract:
Based on the echoes with micro-Doppler signatures, a method is proposed to estimate target frequencies and amplitudes. Model echoes as multi-harmonic micro-Doppler one in order to obtain the connection between target amplitude ratio and frequency domain peak ratio and the relationship between maximum Doppler frequency and target amplitudes. Thus, the method estimating target vibrational parameters is deduced. The method is applicable to the target detections as long as the echoes has multi-harmonic micro-Doppler signatures. The theoretical validity is illustrated with simulation results.
Based on the echoes with micro-Doppler signatures, a method is proposed to estimate target frequencies and amplitudes. Model echoes as multi-harmonic micro-Doppler one in order to obtain the connection between target amplitude ratio and frequency domain peak ratio and the relationship between maximum Doppler frequency and target amplitudes. Thus, the method estimating target vibrational parameters is deduced. The method is applicable to the target detections as long as the echoes has multi-harmonic micro-Doppler signatures. The theoretical validity is illustrated with simulation results.
2008, 30(11): 2650-2653.
doi: 10.3724/SP.J.1146.2007.00612
Abstract:
In the actual detection, the wireless channels from the local detectors to fusion center usually cant be the ideal channel, so the traditional optimal detection arithmetic based on the ideal channel is rectified accordingly. In this paper, a suboptimal detection arithmetic is studied based on non-ideal channel, using Neyman-Pearson (NP) rule the decision forms of every node are derived, according to the probability theory knowledge, the false alarm probability and the detection probability of every node are obtained, in order to maximize the detection probability restricted a constant of the false alarm probability, the iterative arithmetic is applied to find the detective threshold of every node. Finally the smulation shows that the non-ideal channel affect the detection performance of system surely.
In the actual detection, the wireless channels from the local detectors to fusion center usually cant be the ideal channel, so the traditional optimal detection arithmetic based on the ideal channel is rectified accordingly. In this paper, a suboptimal detection arithmetic is studied based on non-ideal channel, using Neyman-Pearson (NP) rule the decision forms of every node are derived, according to the probability theory knowledge, the false alarm probability and the detection probability of every node are obtained, in order to maximize the detection probability restricted a constant of the false alarm probability, the iterative arithmetic is applied to find the detective threshold of every node. Finally the smulation shows that the non-ideal channel affect the detection performance of system surely.
2008, 30(11): 2654-2657.
doi: 10.3724/SP.J.1146.2007.00555
Abstract:
The aliasing of sparse arrays could be theoretically discriminated by two signals with different frequencies, but it could not be eliminated completely in the presence of noise. In order to research the effect on the error decision of targets angle of arrival in instantaneous detection in the condition of aliasing, monopulse amplitude-comparison is exploited to detect the angle of target and the distribution of detected-angle in the noise is derived. The error decision probability of targets angle due to different frequencies signals illuminating the sparse arrays also is obtained according to the distribution above, and the difference between the amplitude- comparison considering only real part of the monopulse ratio and both parts is compared. The results show that the pdf of targets angle by considering both parts is accordance with the simulation data.
The aliasing of sparse arrays could be theoretically discriminated by two signals with different frequencies, but it could not be eliminated completely in the presence of noise. In order to research the effect on the error decision of targets angle of arrival in instantaneous detection in the condition of aliasing, monopulse amplitude-comparison is exploited to detect the angle of target and the distribution of detected-angle in the noise is derived. The error decision probability of targets angle due to different frequencies signals illuminating the sparse arrays also is obtained according to the distribution above, and the difference between the amplitude- comparison considering only real part of the monopulse ratio and both parts is compared. The results show that the pdf of targets angle by considering both parts is accordance with the simulation data.
2008, 30(11): 2658-2661.
doi: 10.3724/SP.J.1146.2007.00565
Abstract:
Based on CCIPCA algorithm in pattern recognition, a low complexity online Music method is presented firstly. It does not need to form the sample covariance matrix or compute its eigenvectors and the estimation of signal subspace begins after the first snap being received, this means the subspace estimation and the data receiving is simultaneous, and the current snap is the only data need to be stored. Then, the data is used repetitiously to improve subspaces estimation performance when few snap is available. Finally, experiments based simulated data demonstrate the efficiency of the presented algorithm.
Based on CCIPCA algorithm in pattern recognition, a low complexity online Music method is presented firstly. It does not need to form the sample covariance matrix or compute its eigenvectors and the estimation of signal subspace begins after the first snap being received, this means the subspace estimation and the data receiving is simultaneous, and the current snap is the only data need to be stored. Then, the data is used repetitiously to improve subspaces estimation performance when few snap is available. Finally, experiments based simulated data demonstrate the efficiency of the presented algorithm.
2008, 30(11): 2662-2665.
doi: 10.3724/SP.J.1146.2007.00713
Abstract:
The performance of adaptive beamforming algorithms is known to degrade severely in the presence of even slight signal steering vector mismatches. To account for the mismatches, a novel robust adaptive beamforming algorithm is proposed. To improve robustness, the weight vector is optimized to involve minimization of a quadratic function subject to the norm of error between the actual and assumed signal steering vectors and the parameter in the optimal solution can be solved accurately. The proposed algorithm can suffer the least distortion from the directions near the steering angle, reduce the influence of the mismatches, and provide an improved robustness against the mismatches. Moreover, it can suppress the interference signals and make the mean output array SINR consistently close to the optimal one. Simulation results demonstrate its validity and superiority as compared with the conventional algorithms.
The performance of adaptive beamforming algorithms is known to degrade severely in the presence of even slight signal steering vector mismatches. To account for the mismatches, a novel robust adaptive beamforming algorithm is proposed. To improve robustness, the weight vector is optimized to involve minimization of a quadratic function subject to the norm of error between the actual and assumed signal steering vectors and the parameter in the optimal solution can be solved accurately. The proposed algorithm can suffer the least distortion from the directions near the steering angle, reduce the influence of the mismatches, and provide an improved robustness against the mismatches. Moreover, it can suppress the interference signals and make the mean output array SINR consistently close to the optimal one. Simulation results demonstrate its validity and superiority as compared with the conventional algorithms.
2008, 30(11): 2666-2669.
doi: 10.3724/SP.J.1146.2007.00608
Abstract:
Independent Component Analysis with Reference (ICA-R) extracts only desired signals by incorporating prior information as reference signals. It can provide output signals with definite order and improved performance. However, no ICA-R algorithm in complex domain has been reported till now. Motivated by the fact that the magnitude information of a complex-valued signal is readily obtained, this paper proposes a fixed-point complex-valued ICA-R algorithm to extract a desired signal by utilizing its magnitude information in the framework of constrained ICA. Specifically, the complex ICA-R is formulated as maximizing the contrast function of a blind complex fastICA algorithm under an inequality constraint corresponding to the magnitude information, the augmented Lagrangian function and Kuhn-Tucker conditions are then used to derive the fixed-point algorithm. The results of computer simulations and performance analysis demonstrate that the complex-valued ICA-R algorithm outperforms the blind complex fastICA algorithm by virtue of incorporation of magnitude information.
Independent Component Analysis with Reference (ICA-R) extracts only desired signals by incorporating prior information as reference signals. It can provide output signals with definite order and improved performance. However, no ICA-R algorithm in complex domain has been reported till now. Motivated by the fact that the magnitude information of a complex-valued signal is readily obtained, this paper proposes a fixed-point complex-valued ICA-R algorithm to extract a desired signal by utilizing its magnitude information in the framework of constrained ICA. Specifically, the complex ICA-R is formulated as maximizing the contrast function of a blind complex fastICA algorithm under an inequality constraint corresponding to the magnitude information, the augmented Lagrangian function and Kuhn-Tucker conditions are then used to derive the fixed-point algorithm. The results of computer simulations and performance analysis demonstrate that the complex-valued ICA-R algorithm outperforms the blind complex fastICA algorithm by virtue of incorporation of magnitude information.
Calculation on Range-Velocity-Acceleration Ambiguous Functions Using Signal Dynamical Representation
2008, 30(11): 2670-2673.
doi: 10.3724/SP.J.1146.2007.00770
Abstract:
In this paper, the calculation of Range-Velocity-Acceleration Ambiguous Function (RVAAF) of wideband signals is considered. In the direct implementation, the formulation of the time-scaling and time-varying signal takes much computational load and its formulation accuracy affects the AAF performance. By exploiting the generating dynamics of the wideband signal, it is found that the time-delay and time-scaling wideband signal can be generated by a corresponding dynamical system with synchronization techniques. With this observation, the AAF can be calculated by following the conventional correlation method. Numerical simulation shows that the proposed method has little computational load and is suitable for non-analytical signals.
In this paper, the calculation of Range-Velocity-Acceleration Ambiguous Function (RVAAF) of wideband signals is considered. In the direct implementation, the formulation of the time-scaling and time-varying signal takes much computational load and its formulation accuracy affects the AAF performance. By exploiting the generating dynamics of the wideband signal, it is found that the time-delay and time-scaling wideband signal can be generated by a corresponding dynamical system with synchronization techniques. With this observation, the AAF can be calculated by following the conventional correlation method. Numerical simulation shows that the proposed method has little computational load and is suitable for non-analytical signals.
2008, 30(11): 2674-2677.
doi: 10.3724/SP.J.1146.2007.00690
Abstract:
The manifold of 3D conformal array geometry is modeled and the classical high resolution Direction-Of-Arrival (DOA) estimation methodMultiple Signal Classification (MUSIC) algorithm is replanted into conformal array. The performance of MUSIC for conformal array is analyzed in detail, including its variance and corresponding Cramer-Rao bound (CRB). Computer simulations for the performance comparison between conformal array (conical array, cylindrical array, and spherical array) and planar array (uniform linear array and uniform circular array) are demonstrated. Some conclusions of MUSIC performance evaluation for different array geometry are reached. It is shown that the performance of MUSIC for different geometric arrays is improved with the increase of the elements number and SNR, which validates the theoretical analysis.
The manifold of 3D conformal array geometry is modeled and the classical high resolution Direction-Of-Arrival (DOA) estimation methodMultiple Signal Classification (MUSIC) algorithm is replanted into conformal array. The performance of MUSIC for conformal array is analyzed in detail, including its variance and corresponding Cramer-Rao bound (CRB). Computer simulations for the performance comparison between conformal array (conical array, cylindrical array, and spherical array) and planar array (uniform linear array and uniform circular array) are demonstrated. Some conclusions of MUSIC performance evaluation for different array geometry are reached. It is shown that the performance of MUSIC for different geometric arrays is improved with the increase of the elements number and SNR, which validates the theoretical analysis.
2008, 30(11): 2678-2683.
doi: 10.3724/SP.J.1146.2007.00666
Abstract:
MP3 coding has become the most popular coding method for audio signals. The distortions of MP3 coding from time and frequency domain based on experiments are explored. An audio watermarking method is proposed: besides synchronization by extracting host signal, secret bit is embedded by quantizing the proportion of low frequency energy of two sequential frames. Then reference parameter values by evaluation of each embedding frame were suggested. The experiment results show the imperceptablity and the robustness against MP3 with a low bit rate and low sampling frequency and against AAC coding, also with a satisfying capacity.
MP3 coding has become the most popular coding method for audio signals. The distortions of MP3 coding from time and frequency domain based on experiments are explored. An audio watermarking method is proposed: besides synchronization by extracting host signal, secret bit is embedded by quantizing the proportion of low frequency energy of two sequential frames. Then reference parameter values by evaluation of each embedding frame were suggested. The experiment results show the imperceptablity and the robustness against MP3 with a low bit rate and low sampling frequency and against AAC coding, also with a satisfying capacity.
2008, 30(11): 2684-2687.
doi: 10.3724/SP.J.1146.2007.00570
Abstract:
Based on a new viewpoint that digital image is considered as mass with non-uniform densities, a novel scrambling degree rule is presented that can be used to measure the scrambling degree by the distance between the center of mass and the center of figure. Compared with other rules, this rule has the distinguished advantage that it can measure the scrambling degree of any scrambled image using only the information of image. Experimental results show that its performance is superior to other rules.
Based on a new viewpoint that digital image is considered as mass with non-uniform densities, a novel scrambling degree rule is presented that can be used to measure the scrambling degree by the distance between the center of mass and the center of figure. Compared with other rules, this rule has the distinguished advantage that it can measure the scrambling degree of any scrambled image using only the information of image. Experimental results show that its performance is superior to other rules.
2008, 30(11): 2688-2692.
doi: 10.3724/SP.J.1146.2007.00675
Abstract:
In view of the fact that the center position of new target template obtained by the computation of the core step of Mean Shift algorithm is nearly all non-integer, in this paper, a concept of fuzzy membership is proposed, the steps in image tracking using Mean Shift algorithm are improved. The results of experiments show that computational load and error are less than that of the original algorithm.
In view of the fact that the center position of new target template obtained by the computation of the core step of Mean Shift algorithm is nearly all non-integer, in this paper, a concept of fuzzy membership is proposed, the steps in image tracking using Mean Shift algorithm are improved. The results of experiments show that computational load and error are less than that of the original algorithm.
2008, 30(11): 2693-2697.
doi: 10.3724/SP.J.1146.2007.00808
Abstract:
In order to study the effect of raw data compression on space-borne InSAR interferometry. This paper utilizes 4 typical ERS-1/2 raw data of different altitude to evaluate Block Adaptive Quantization (BAQ) and Amplitude-Phase (AP) algorithm. The numerical experiments results show that when BAQ is used, the block size should be chosen carefully. At the same time, 4 bit/sample is the least bit rate for precise SAR interferometry when the vertical baseline is short. When AP algorithm is used, the quantization bits should be distributed suitably. When the average bit rate is 3 bit/sample, the best choice of AP is 2 bits for amplitude quantization and 4 bits for phase quantization which performance is between 3 bit BAQ and 4 bit BAQ.
In order to study the effect of raw data compression on space-borne InSAR interferometry. This paper utilizes 4 typical ERS-1/2 raw data of different altitude to evaluate Block Adaptive Quantization (BAQ) and Amplitude-Phase (AP) algorithm. The numerical experiments results show that when BAQ is used, the block size should be chosen carefully. At the same time, 4 bit/sample is the least bit rate for precise SAR interferometry when the vertical baseline is short. When AP algorithm is used, the quantization bits should be distributed suitably. When the average bit rate is 3 bit/sample, the best choice of AP is 2 bits for amplitude quantization and 4 bits for phase quantization which performance is between 3 bit BAQ and 4 bit BAQ.
2008, 30(11): 2698-2701.
doi: 10.3724/SP.J.1146.2007.00701
Abstract:
In this paper, a new iterative classification of polarimetric SAR image based on Freeman decomposition and scattering entropy is proposed. This technique extracts the powers of three scattering mechanism components through Freeman decomposition and scattering entropy through H/ decomposition first; Then using the four parameters which can characterize terrain divides the terrains of polarimetric SAR image into nine initial classes, and the final result is obtained by iterative classification with Wishart classifier. This method utilizes polarimetric scattering information of terrain with reason, can acquire good effect of classification and requires a little operation. The effectiveness of this method is demonstrated with the experimental results of polarimetric SAR datas measured practically.
In this paper, a new iterative classification of polarimetric SAR image based on Freeman decomposition and scattering entropy is proposed. This technique extracts the powers of three scattering mechanism components through Freeman decomposition and scattering entropy through H/ decomposition first; Then using the four parameters which can characterize terrain divides the terrains of polarimetric SAR image into nine initial classes, and the final result is obtained by iterative classification with Wishart classifier. This method utilizes polarimetric scattering information of terrain with reason, can acquire good effect of classification and requires a little operation. The effectiveness of this method is demonstrated with the experimental results of polarimetric SAR datas measured practically.
2008, 30(11): 2702-2705.
doi: 10.3724/SP.J.1146.2007.00639
Abstract:
Bistatic Ground-Wave Over-The-Horizon Radar (GWOTHR) uses an array located on a coast to transmit orthogonal frequency coded signals, and a single antenna to receive the returns. The direct-path-interference suppression methods such as transmit nulling and sidelobe cancellation are inapplicable because the energy is radiated isotropiclly and the receive platform is moving. The method of subspace-projection based direct-path-interference suppression is presented in this paper with the characters of this radar and the interference nulling technique considered, followed by the anlysis of the technqiues performance. The orthogonal projection matrix to the direct-path subspace is formulated using the received signals which are then projected to the null space and the direct-path interference are suppressed. Both the simulated and the real data prove the validity of the method.
Bistatic Ground-Wave Over-The-Horizon Radar (GWOTHR) uses an array located on a coast to transmit orthogonal frequency coded signals, and a single antenna to receive the returns. The direct-path-interference suppression methods such as transmit nulling and sidelobe cancellation are inapplicable because the energy is radiated isotropiclly and the receive platform is moving. The method of subspace-projection based direct-path-interference suppression is presented in this paper with the characters of this radar and the interference nulling technique considered, followed by the anlysis of the technqiues performance. The orthogonal projection matrix to the direct-path subspace is formulated using the received signals which are then projected to the null space and the direct-path interference are suppressed. Both the simulated and the real data prove the validity of the method.
2008, 30(11): 2706-2709.
doi: 10.3724/SP.J.1146.2007.00679
Abstract:
Circular-Scan SAR is mainly used for scene matching in the precision-guided missiles, where geometry accuracy is very important. However, due to errors introduced by the GPS/IMU, it remains somewhat geometric distortion after geometric distortion correction based on the GPS/IMU data. This paper analyzes the impact of the error of scan angle and aircraft height and aircraft velocity on the image quality. Meanwhile, approaches to correcting these errors based on measured data are presented. Experiments carried out on measured data confirm the validity of the analysis and the feasibility of the compensation scheme.
Circular-Scan SAR is mainly used for scene matching in the precision-guided missiles, where geometry accuracy is very important. However, due to errors introduced by the GPS/IMU, it remains somewhat geometric distortion after geometric distortion correction based on the GPS/IMU data. This paper analyzes the impact of the error of scan angle and aircraft height and aircraft velocity on the image quality. Meanwhile, approaches to correcting these errors based on measured data are presented. Experiments carried out on measured data confirm the validity of the analysis and the feasibility of the compensation scheme.
2008, 30(11): 2710-2713.
doi: 10.3724/SP.J.1146.2007.00637
Abstract:
In order to overcome the insufficiency of traditional algorithms in multi-target enhancement and polarimetric signature preservation, a new method is proposed to enhance targets in polarimetric SAR imagery. Based on the similarity parameter between target scattering matrix and surface scattering matrix, the coherency matrix of random target corresponding to different scattering mechanisms is multiplied by relevant real coefficient, thus it enlarges the otherness between surface scattering targets and other scattering targets. As coherency matrix is operated as a whole in this method, it does not change the relationship between the elements of coherency matrix and then preserves polarimetric information in SAR imagery. Utilizing fully polarimetric data obtained by SIR-C/X-SAR to test this method, the result is satisfactory.
In order to overcome the insufficiency of traditional algorithms in multi-target enhancement and polarimetric signature preservation, a new method is proposed to enhance targets in polarimetric SAR imagery. Based on the similarity parameter between target scattering matrix and surface scattering matrix, the coherency matrix of random target corresponding to different scattering mechanisms is multiplied by relevant real coefficient, thus it enlarges the otherness between surface scattering targets and other scattering targets. As coherency matrix is operated as a whole in this method, it does not change the relationship between the elements of coherency matrix and then preserves polarimetric information in SAR imagery. Utilizing fully polarimetric data obtained by SIR-C/X-SAR to test this method, the result is satisfactory.
2008, 30(11): 2714-2718.
doi: 10.3724/SP.J.1146.2007.00622
Abstract:
Aimed at the distributed SAR satellite system consisting of more than three satellites, SM-PSO algorithm-based configuration optimal design is proposed in this paper. The mean orbital elements differences of among satellites are given and the normal configuration design flow of distributed SAR satellite system is presented. In order to realize exactly and fleetly system configuration design faced to mission requirements, the SM-PSO algorithm-based configuration optimal design method is developed. The configuration optimal design is completed in terms of configuration stability, limited by effective baseline range, working time and ground coverage area. It is indicated that the system configuration initial parameters from this method can meet with ground converge and relative steady effective baseline requirements.
Aimed at the distributed SAR satellite system consisting of more than three satellites, SM-PSO algorithm-based configuration optimal design is proposed in this paper. The mean orbital elements differences of among satellites are given and the normal configuration design flow of distributed SAR satellite system is presented. In order to realize exactly and fleetly system configuration design faced to mission requirements, the SM-PSO algorithm-based configuration optimal design method is developed. The configuration optimal design is completed in terms of configuration stability, limited by effective baseline range, working time and ground coverage area. It is indicated that the system configuration initial parameters from this method can meet with ground converge and relative steady effective baseline requirements.
2008, 30(11): 2719-2723.
doi: 10.3724/SP.J.1146.2007.00761
Abstract:
Phase Adjustment by Contrast Enhancement (PACE) algorithm is a new nonparametric autofocus algorithm, which can extract effectively high frequency phase errors from Synthetic Aperture Radar (SAR) images. PACE algorithm searching the best parameters by optimization method needs much heavy computation load because it takes directly the phase correction vector as variables to be estimated. To reduce the computation load, an improved PACE algorithm is proposed in this paper, which is called Interpolated PACE (IPACE) algorithm. The IPACE takes the contrast function as object function and some variable of the phase correction vector as parameters to be estimated The IPACE algorithm needs much less computation load than the PACE, and the image quality achieved by IPACE is almost the same good as the quality through PACE. The results of focusing the real SAR data show the method is a good robust autofocus algorithm.
Phase Adjustment by Contrast Enhancement (PACE) algorithm is a new nonparametric autofocus algorithm, which can extract effectively high frequency phase errors from Synthetic Aperture Radar (SAR) images. PACE algorithm searching the best parameters by optimization method needs much heavy computation load because it takes directly the phase correction vector as variables to be estimated. To reduce the computation load, an improved PACE algorithm is proposed in this paper, which is called Interpolated PACE (IPACE) algorithm. The IPACE takes the contrast function as object function and some variable of the phase correction vector as parameters to be estimated The IPACE algorithm needs much less computation load than the PACE, and the image quality achieved by IPACE is almost the same good as the quality through PACE. The results of focusing the real SAR data show the method is a good robust autofocus algorithm.
2008, 30(11): 2724-2727.
doi: 10.3724/SP.J.1146.2007.00670
Abstract:
Researching data processing of the spaceborne precipitation radar is very important in understanding this unique radar system and developing data application, and will help to design spaceborne weather radar and develop algorithms in the future. Radar reflectivity factor is retrieved using observation data; surface radar cross section and path integration attenuation are calculated with less computation. Rain type classification is also studied and the final results are presented. Typhoon data are processed and some pictures illustrating its 3D structure are given. These results can provide valuable information about internal structures as well as mechanism of precipitation.
Researching data processing of the spaceborne precipitation radar is very important in understanding this unique radar system and developing data application, and will help to design spaceborne weather radar and develop algorithms in the future. Radar reflectivity factor is retrieved using observation data; surface radar cross section and path integration attenuation are calculated with less computation. Rain type classification is also studied and the final results are presented. Typhoon data are processed and some pictures illustrating its 3D structure are given. These results can provide valuable information about internal structures as well as mechanism of precipitation.
2008, 30(11): 2728-2731.
doi: 10.3724/SP.J.1146.2007.00681
Abstract:
This paper proposes a novel bandwidth-matched digital receiving method based on the variable- bandwidth EFT filter. The variable-bandwidth frequency characteristics of the Linear Quasi-Time-Invariant (LQTI) system in Extended Fourier Transform (EFT) frequency domain are used for constructing the Variable-Bandwidth Filter (VBF). By using the variable-bandwidth EFT filter, the Digital DownConversion (DDC) can correctly receive the signals with different bandwidth. Based on a simple updating routine, the proposed variable-bandwidth filter can considerably reduce the complexity during normal operations. It is proposed that the efficient polyphase structure of bandwidth-matched digital downconversion and a significant improvement in efficiency and realizability can be achieved. Finally, the experimental results show the correctness and validity of the method.
This paper proposes a novel bandwidth-matched digital receiving method based on the variable- bandwidth EFT filter. The variable-bandwidth frequency characteristics of the Linear Quasi-Time-Invariant (LQTI) system in Extended Fourier Transform (EFT) frequency domain are used for constructing the Variable-Bandwidth Filter (VBF). By using the variable-bandwidth EFT filter, the Digital DownConversion (DDC) can correctly receive the signals with different bandwidth. Based on a simple updating routine, the proposed variable-bandwidth filter can considerably reduce the complexity during normal operations. It is proposed that the efficient polyphase structure of bandwidth-matched digital downconversion and a significant improvement in efficiency and realizability can be achieved. Finally, the experimental results show the correctness and validity of the method.
2008, 30(11): 2732-2736.
doi: 10.3724/SP.J.1146.2007.00707
Abstract:
In this paper, a method for automatic object extraction in high-resolution remote sensing image is proposed. First, a robust multilayer classifier is employed to detect the object efficiently. Secondly, a cost function based on the color model and the smoothness prior knowledge is built up and minimized to segment the object accurately. Lastly, in the post processing stage, the shape prior knowledge of the object is utilized to eliminate the false positives and improve the extraction precision. As an example of objects in remote sensing images the oil tanks are extracted. Experimental results demonstrate the robustness and effectiveness of the proposed automatic object extraction method.
In this paper, a method for automatic object extraction in high-resolution remote sensing image is proposed. First, a robust multilayer classifier is employed to detect the object efficiently. Secondly, a cost function based on the color model and the smoothness prior knowledge is built up and minimized to segment the object accurately. Lastly, in the post processing stage, the shape prior knowledge of the object is utilized to eliminate the false positives and improve the extraction precision. As an example of objects in remote sensing images the oil tanks are extracted. Experimental results demonstrate the robustness and effectiveness of the proposed automatic object extraction method.
2008, 30(11): 2737-2741.
doi: 10.3724/SP.J.1146.2007.00614
Abstract:
Traditional unsupervised change detection algorithms based on simple MRF model assume that subimages applied to extracting features are homogeneous, but that is not always true and causes low accuracy. Based on the fields Correlation Markov Random Field (CMRF) model, an adaptive algorithm is proposed in this paper. The labeling is obtained through solving a Maximum A Posterior (MAP) problem by Iteration Condition Model (ICM). Features of each pixel are exacted by using only the pixels currently labeled as the same pattern. With the adapted features, the new labeling is obtained. Under the idea of two-stage iteration algorithm, we use the difference image of multitemporal remote-sensing images as observation field. The satisfied experimental confirm the effectiveness of proposed techniques.
Traditional unsupervised change detection algorithms based on simple MRF model assume that subimages applied to extracting features are homogeneous, but that is not always true and causes low accuracy. Based on the fields Correlation Markov Random Field (CMRF) model, an adaptive algorithm is proposed in this paper. The labeling is obtained through solving a Maximum A Posterior (MAP) problem by Iteration Condition Model (ICM). Features of each pixel are exacted by using only the pixels currently labeled as the same pattern. With the adapted features, the new labeling is obtained. Under the idea of two-stage iteration algorithm, we use the difference image of multitemporal remote-sensing images as observation field. The satisfied experimental confirm the effectiveness of proposed techniques.
2008, 30(11): 2742-2745.
doi: 10.3724/SP.J.1146.2007.00598
Abstract:
The impact of residual code phase and carrier frequency estimate error on correlation is analyzed in detail, and the correlation expression is given. The advantage and deficiency of these existed code phase discrimination algorithms are analyzed from the view of the Linearity, the sensitivity for signal amplitude and carrier frequency estimate error, and the computational complexity. Based on the above research, a new C/A code phase discrimination algorithm is proposed. The analysis and simulation results indicate that the new algorithm which has good linearity can restrain the sensitivity for signal amplitude and carrier frequency estimate error and multipath error effectively, and has high tracking precision and low computational complexity. Tracking performance is improved obviously by using the proposed algorithm.
The impact of residual code phase and carrier frequency estimate error on correlation is analyzed in detail, and the correlation expression is given. The advantage and deficiency of these existed code phase discrimination algorithms are analyzed from the view of the Linearity, the sensitivity for signal amplitude and carrier frequency estimate error, and the computational complexity. Based on the above research, a new C/A code phase discrimination algorithm is proposed. The analysis and simulation results indicate that the new algorithm which has good linearity can restrain the sensitivity for signal amplitude and carrier frequency estimate error and multipath error effectively, and has high tracking precision and low computational complexity. Tracking performance is improved obviously by using the proposed algorithm.
2008, 30(11): 2746-2749.
doi: 10.3724/SP.J.1146.2007.00725
Abstract:
HSMC-SVM is a kind of high-speed multi-class SVM with direct mode, and it is appropriate for the situation having lots of categories. Because working set selection of SMO algorithm is based on experience, HSMC-SVM would converge slowly trained with SMO. For accelerating the convergence process of HSMC-SVM, a new approach of working set selection based on second order approximation is proposed. At the same time, shrinking strategy is used too. The numeric experiments show that these measures can speed up the convergence process of HSMC-SVM efficiently. The convergence process of HSMC-SVM is even shorter than these composed multi-class SVMs trained with libsvm. Hence, HSMV-SVM based on second order approximation is very appropriate for the situation that classification category is more and the number of training samples is large.
HSMC-SVM is a kind of high-speed multi-class SVM with direct mode, and it is appropriate for the situation having lots of categories. Because working set selection of SMO algorithm is based on experience, HSMC-SVM would converge slowly trained with SMO. For accelerating the convergence process of HSMC-SVM, a new approach of working set selection based on second order approximation is proposed. At the same time, shrinking strategy is used too. The numeric experiments show that these measures can speed up the convergence process of HSMC-SVM efficiently. The convergence process of HSMC-SVM is even shorter than these composed multi-class SVMs trained with libsvm. Hence, HSMV-SVM based on second order approximation is very appropriate for the situation that classification category is more and the number of training samples is large.
2008, 30(11): 2750-2754.
doi: 10.3724/SP.J.1146.2007.00596
Abstract:
Distributed Memory Service is integrated in Simulink-based multiprocessor design flow to improve communication efficiency comparing to Global FIFO(GFIFO) method. In Motion-JPEG case study, DMS made the percentage cost on communication of total execution time decreased by 50%, and the execution time decreased by 30% for decoding 10 frames， comparing with GFIFO. This integration makes more opportunities in design exploration to improve the performance of Simulink-based multiprocessor design flow.
Distributed Memory Service is integrated in Simulink-based multiprocessor design flow to improve communication efficiency comparing to Global FIFO(GFIFO) method. In Motion-JPEG case study, DMS made the percentage cost on communication of total execution time decreased by 50%, and the execution time decreased by 30% for decoding 10 frames， comparing with GFIFO. This integration makes more opportunities in design exploration to improve the performance of Simulink-based multiprocessor design flow.
2008, 30(11): 2755-2758.
doi: 10.3724/SP.J.1146.2007.00769
Abstract:
For crests and troughs exiting in the scattering parameters of the coupled microstrip lines, the relation between the frequencies where crests and troughs occur and the parallel length, space between lines for the four-port network is deduced from scattering parameters of the odd mode and even mode based on microwave network principle. Effect on the transmitted signal by the insertion loss for the structure of two parallel microstrip lines is also studied in frequency domain and time domain respectively. Due to the coupling between microstrip lines, it is shown that the frequencies where crests and troughs occur increase with the space between lines but reduce with the parallel length, and the transmitted signal is attenuated when crosstalk is induced.
For crests and troughs exiting in the scattering parameters of the coupled microstrip lines, the relation between the frequencies where crests and troughs occur and the parallel length, space between lines for the four-port network is deduced from scattering parameters of the odd mode and even mode based on microwave network principle. Effect on the transmitted signal by the insertion loss for the structure of two parallel microstrip lines is also studied in frequency domain and time domain respectively. Due to the coupling between microstrip lines, it is shown that the frequencies where crests and troughs occur increase with the space between lines but reduce with the parallel length, and the transmitted signal is attenuated when crosstalk is induced.
2008, 30(11): 2759-2762.
doi: 10.3724/SP.J.1146.2007.00777
Abstract:
In this paper, a kind of linear-end metallic thin wire antenna is studied. The properties of the transmitted waveforms in free space, the footprints and the VSWR are simulated with the FDTD method and tested. Simulations are carried out for various parameters such as end resistor values, permittivity values, flare angles, and height above the ground. The electronic field distributions in near field are simulated in different modulated frequencies. The results show that the simulation results and the measurement results are basic agreement. The results also show that this kind of antenna is more adaptive to the different working conditions than the common bow-tie antenna.
In this paper, a kind of linear-end metallic thin wire antenna is studied. The properties of the transmitted waveforms in free space, the footprints and the VSWR are simulated with the FDTD method and tested. Simulations are carried out for various parameters such as end resistor values, permittivity values, flare angles, and height above the ground. The electronic field distributions in near field are simulated in different modulated frequencies. The results show that the simulation results and the measurement results are basic agreement. The results also show that this kind of antenna is more adaptive to the different working conditions than the common bow-tie antenna.
2008, 30(11): 2763-2766.
doi: 10.3724/SP.J.1146.2007.00652
Abstract:
A fast solution to the Volume Integral Equation (VIE) for 3-D dielectric objects is implemented by using the precorrected-FFT method. A new stencil topology is presented to reduce near-zone interactions to be computed directly and precorrected, in which the projection and interpolation stencils are floating but not fixed. Numerical results show that the P-FFT method based on floating stencil can significantly reduce near-zone interactions to be precorrected, as well as memory and CPU time.
A fast solution to the Volume Integral Equation (VIE) for 3-D dielectric objects is implemented by using the precorrected-FFT method. A new stencil topology is presented to reduce near-zone interactions to be computed directly and precorrected, in which the projection and interpolation stencils are floating but not fixed. Numerical results show that the P-FFT method based on floating stencil can significantly reduce near-zone interactions to be precorrected, as well as memory and CPU time.
2008, 30(11): 2767-2770.
doi: 10.3724/SP.J.1146.2007.00710
Abstract:
A novel FDTD modeling approach for active devices characterized by measured S-parameters is presented. This approach applies Vector Fitting (VF) technique and Piecewise Linear Recursive Convolution (PLRC) technique to complete modeling process, and does not need to know the equivalent circuits of active devices. It preserves the explicit nature of the conventional FDTD method, and obtains a general updated formula. Furthermore, the main data-processing procedure is directly handled over the frequency band of interest, which avoids the time-domain non-causal error in traditional techniques. It is useful to full-wave analyze hybrid microwave circuits including practical active devices.
A novel FDTD modeling approach for active devices characterized by measured S-parameters is presented. This approach applies Vector Fitting (VF) technique and Piecewise Linear Recursive Convolution (PLRC) technique to complete modeling process, and does not need to know the equivalent circuits of active devices. It preserves the explicit nature of the conventional FDTD method, and obtains a general updated formula. Furthermore, the main data-processing procedure is directly handled over the frequency band of interest, which avoids the time-domain non-causal error in traditional techniques. It is useful to full-wave analyze hybrid microwave circuits including practical active devices.
2008, 30(11): 2771-2774.
doi: 10.3724/SP.J.1146.2007.00796
Abstract:
In this paper, based on a small-signal theory, an analytical expression for the harmonic contents in the prebunched electron beam in a multicavity gyroklystron is obtained. As an example, the dependence of the harmonic contents in three-cavity gyroklystron amplifier on the prebunched parameters is numerically calculated. The results show that the second harmonic content is much smaller than the fundamental harmonic content and the undulation of the second harmonic content depended on the second cavity prebunched parameters is greater than the fundamental one, and the amplitude of the second harmonics in the electron beam current density as functions of the bunching parameters is proportional to the field amplitude in the second cavity and relate with the electron phase shift resulting from the first drift region and the effect of input cavity Q in a certain range on the harmonic content is little or nothing.
In this paper, based on a small-signal theory, an analytical expression for the harmonic contents in the prebunched electron beam in a multicavity gyroklystron is obtained. As an example, the dependence of the harmonic contents in three-cavity gyroklystron amplifier on the prebunched parameters is numerically calculated. The results show that the second harmonic content is much smaller than the fundamental harmonic content and the undulation of the second harmonic content depended on the second cavity prebunched parameters is greater than the fundamental one, and the amplitude of the second harmonics in the electron beam current density as functions of the bunching parameters is proportional to the field amplitude in the second cavity and relate with the electron phase shift resulting from the first drift region and the effect of input cavity Q in a certain range on the harmonic content is little or nothing.
2008, 30(11): 2775-2779.
doi: 10.3724/SP.J.1146.2007.00703
Abstract:
A new kind of 3-stage filter type of output circuit for lower RF band and middle power broadband klystron, -mode double-gap cavity loaded by Coaxial-Rectangular Waveguide output circuit, is put forward and the feasibility is demonstrated. The performance of this kind of output circuit is simulated and the influence of all parts of the output circuit on the gap impedance of the output cavity is investigated in detail. The research results show that, the coaxial-rectangular waveguide output circuit not only overcomes the obstacle of big rectangular waveguides impairment of focus system of beams and is of benefit to raising the efficiency, but also has a very wide band and high power capacity.
A new kind of 3-stage filter type of output circuit for lower RF band and middle power broadband klystron, -mode double-gap cavity loaded by Coaxial-Rectangular Waveguide output circuit, is put forward and the feasibility is demonstrated. The performance of this kind of output circuit is simulated and the influence of all parts of the output circuit on the gap impedance of the output cavity is investigated in detail. The research results show that, the coaxial-rectangular waveguide output circuit not only overcomes the obstacle of big rectangular waveguides impairment of focus system of beams and is of benefit to raising the efficiency, but also has a very wide band and high power capacity.
2008, 30(11): 2780-2783.
doi: 10.3724/SP.J.1146.2007.00698
Abstract:
This paper points out that the fake solutions appear when the quasi-period boundary condition method is applied to the coupled-cavity structure. Phase method and energy method are presented to identify the fake solutions. Then, the cause of fake solutions is made out. Theory analysis and phase method is presented to eliminate the fake solutions. Finally, the application of the method on Huges coupled-cavity structure is carried out as an example.
This paper points out that the fake solutions appear when the quasi-period boundary condition method is applied to the coupled-cavity structure. Phase method and energy method are presented to identify the fake solutions. Then, the cause of fake solutions is made out. Theory analysis and phase method is presented to eliminate the fake solutions. Finally, the application of the method on Huges coupled-cavity structure is carried out as an example.
2008, 30(11): 2784-2787.
doi: 10.3724/SP.J.1146.2007.01814
Abstract:
Based on the 2-D dynamic displacement field model, the dynamic displacement model is extended from 2-D to 3-D. It realizes the description for the motion state estimation of the target in the depth direction of the sight field. It provides a gradually description process for distorted image sequence from estimating plane displacements to estimating spatial motion state. Compared to other video tracking techniques, based on the 3-D dynamic displacement field model, it has been implemented to stabilize the tracking sequence and estimate the targets motion state.
Based on the 2-D dynamic displacement field model, the dynamic displacement model is extended from 2-D to 3-D. It realizes the description for the motion state estimation of the target in the depth direction of the sight field. It provides a gradually description process for distorted image sequence from estimating plane displacements to estimating spatial motion state. Compared to other video tracking techniques, based on the 3-D dynamic displacement field model, it has been implemented to stabilize the tracking sequence and estimate the targets motion state.
2008, 30(11): 2788-2791.
doi: 10.3724/SP.J.1146.2007.00799
Abstract:
Good degree distributions can improve the error-floor and reduce the complication in encoding and decoding of LDPC. Under AWGN channel, Gaussian approximation algorithm can analyze the decoding threshold of LDPC presented by their degree distributions. Using differential evolution, the degree distributions that possess maximal threshold can be gotten. Through simulation results, the optimized degree distributions which possess a 0.15dB better noisy threshold than using linear algorithm.
Good degree distributions can improve the error-floor and reduce the complication in encoding and decoding of LDPC. Under AWGN channel, Gaussian approximation algorithm can analyze the decoding threshold of LDPC presented by their degree distributions. Using differential evolution, the degree distributions that possess maximal threshold can be gotten. Through simulation results, the optimized degree distributions which possess a 0.15dB better noisy threshold than using linear algorithm.
2008, 30(11): 2792-2794.
doi: 10.3724/SP.J.1146.2007.00797
Abstract:
3-D electromagnetic simulation software is used to calculate the dispersion and interaction impedance of circular comb Slow-Wave Structure (SWS) which works for Terahertz (THz) Backward-wave Oscillators (BWO). The results show that the inner radius of SWS is 0.175mm in the band of 430-570GHz, and the inner radius of SWS is 0.1mm in the band of 760-940GHz. The large radius of SWS is a great help for improving beam transmission. The interaction impedance of fundamental backward wave of the SWS is smaller than 1 is a good explain to the truth that the electronic efficiency of THz BWO is smaller than 0.01%.
3-D electromagnetic simulation software is used to calculate the dispersion and interaction impedance of circular comb Slow-Wave Structure (SWS) which works for Terahertz (THz) Backward-wave Oscillators (BWO). The results show that the inner radius of SWS is 0.175mm in the band of 430-570GHz, and the inner radius of SWS is 0.1mm in the band of 760-940GHz. The large radius of SWS is a great help for improving beam transmission. The interaction impedance of fundamental backward wave of the SWS is smaller than 1 is a good explain to the truth that the electronic efficiency of THz BWO is smaller than 0.01%.
