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2011 Vol. 33, No. 10
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2011, 33(10): 2287-2292.
doi: 10.3724/SP.J.1146.2011.00157
Abstract:
The capacity of a Mobile User (MU) is analyzed for downlink distributed communication system in multi-cell environment, when MU locates at any position within the cell. Moreover, the closed-form expression of the capacity is derived. Most papers adopt Central Limit Theory (CLT), and the precondition of it is that the interference terms are more enough. If the interference terms are few, the CLT method has defects in system performance analysis. The contribution of the paper is that the constraint condition is relaxed. The interference plus noise is considered as Gaussian noise with fixed variance when adopting CLT. On the contrary, the variance of the interference plus noise is considered as a random variable influenced by transmit power as well as propagation pathloss in the paper. Under the relaxed condition, the system performance is re-analyzed and the repeated-root problem making use of Moment Generation Function (MGF) is overcome. Through theoretical analysis along with numerical simulations, it demonstrates that the proposed analytical method can represent the propagation pathloss effect on interference more accurately. Thus, the whole system performance is improved.
The capacity of a Mobile User (MU) is analyzed for downlink distributed communication system in multi-cell environment, when MU locates at any position within the cell. Moreover, the closed-form expression of the capacity is derived. Most papers adopt Central Limit Theory (CLT), and the precondition of it is that the interference terms are more enough. If the interference terms are few, the CLT method has defects in system performance analysis. The contribution of the paper is that the constraint condition is relaxed. The interference plus noise is considered as Gaussian noise with fixed variance when adopting CLT. On the contrary, the variance of the interference plus noise is considered as a random variable influenced by transmit power as well as propagation pathloss in the paper. Under the relaxed condition, the system performance is re-analyzed and the repeated-root problem making use of Moment Generation Function (MGF) is overcome. Through theoretical analysis along with numerical simulations, it demonstrates that the proposed analytical method can represent the propagation pathloss effect on interference more accurately. Thus, the whole system performance is improved.
2011, 33(10): 2293-2299.
doi: 10.3724/SP.J.1146.2011.00197
Abstract:
A joint precoding algorithmZero Force-Tomlinson-Harashima Precoding (ZF-THP) algorithm is proposed based on overlapped clustering model. Then, two problems in existing clustering scheme are investigated and corresponding resolutions are designed by employing the ZF-THP algorithm: one is an inter-cluster interference mitigated scheme; the other is an overlapping clustering scheme under the condition of asymmetry of Degree Wiliness to Cooperate (DWC). Simulation results show the scheme proposed performs better than other conventional clustering algorithm in the system spectrum efficiency, and enhances the capacity of partial users fairness.
A joint precoding algorithmZero Force-Tomlinson-Harashima Precoding (ZF-THP) algorithm is proposed based on overlapped clustering model. Then, two problems in existing clustering scheme are investigated and corresponding resolutions are designed by employing the ZF-THP algorithm: one is an inter-cluster interference mitigated scheme; the other is an overlapping clustering scheme under the condition of asymmetry of Degree Wiliness to Cooperate (DWC). Simulation results show the scheme proposed performs better than other conventional clustering algorithm in the system spectrum efficiency, and enhances the capacity of partial users fairness.
2011, 33(10): 2300-2305.
doi: 10.3724/SP.J.1146.2011.00413
Abstract:
There exists circular trap in Circular Viterbi Algorithm (CVA) and deficiencies in CVA-based decoding algorithms of Tail-Biting Convolutional Codes (TBCC). A high efficient decoding algorithm is proposed for TBCC. The checking rule for circular trap in the new algorithm is that comparing whether the two maximum likelihood paths obtained from two different iterations are identical to each other, if they are identical, the CVA should be terminated. Meanwhile, when there no trap happens, a new adaptive stopping rule for CVA is proposed which is based on comparing the maximum likelihood path with the best maximum likelihood tail-biting path. Furthermore, the path used as the measurements in the checking rule and in the stopping rule is replaced by its net path metric to reduce the complexity of decoder. The results of experiments show that the new algorithm improves the decoding efficiency and reduces the decoder complexity.
There exists circular trap in Circular Viterbi Algorithm (CVA) and deficiencies in CVA-based decoding algorithms of Tail-Biting Convolutional Codes (TBCC). A high efficient decoding algorithm is proposed for TBCC. The checking rule for circular trap in the new algorithm is that comparing whether the two maximum likelihood paths obtained from two different iterations are identical to each other, if they are identical, the CVA should be terminated. Meanwhile, when there no trap happens, a new adaptive stopping rule for CVA is proposed which is based on comparing the maximum likelihood path with the best maximum likelihood tail-biting path. Furthermore, the path used as the measurements in the checking rule and in the stopping rule is replaced by its net path metric to reduce the complexity of decoder. The results of experiments show that the new algorithm improves the decoding efficiency and reduces the decoder complexity.
2011, 33(10): 2306-2311.
doi: 10.3724/SP.J.1146.2011.00242
Abstract:
To solve the spectrum assignment issue in cognitive network, a new ant optimization algorithm for spectrum assignment is proposed in this paper. In the cognitive radio network model, where primary and secondary users are coexistent, ants visit secondary users as the node, and leave pheromones using channel rewards. By this way the optimized parallel algorithm is implemented. Compared with the traditional spectrum assignment method, it can implement enhanced accumulation by learning, fast coverage to the optimal resolution, and improve the performance in the whole network average throughput. The method is analyzed. Simulation results verify the stability and validity of the method.
To solve the spectrum assignment issue in cognitive network, a new ant optimization algorithm for spectrum assignment is proposed in this paper. In the cognitive radio network model, where primary and secondary users are coexistent, ants visit secondary users as the node, and leave pheromones using channel rewards. By this way the optimized parallel algorithm is implemented. Compared with the traditional spectrum assignment method, it can implement enhanced accumulation by learning, fast coverage to the optimal resolution, and improve the performance in the whole network average throughput. The method is analyzed. Simulation results verify the stability and validity of the method.
2011, 33(10): 2312-2316.
doi: 10.3724/SP.J.1146.2010.01409
Abstract:
The effective capacity of the multi-user OFDMA (Orthogonal Frequency-Division Multiple Access) system for time-varying channel is characterized. Then to maximize the system average effective capacity, through the Tayler approximation, an asymptotical optimal user scheduling is proposed, which selects users based on the relationships among the moving speed, traffic profile and the effective capacity. By means of simulations, it is further shown that the proposed scheme can improve the effective capacity of the mobile hosts.
The effective capacity of the multi-user OFDMA (Orthogonal Frequency-Division Multiple Access) system for time-varying channel is characterized. Then to maximize the system average effective capacity, through the Tayler approximation, an asymptotical optimal user scheduling is proposed, which selects users based on the relationships among the moving speed, traffic profile and the effective capacity. By means of simulations, it is further shown that the proposed scheme can improve the effective capacity of the mobile hosts.
2011, 33(10): 2317-2321.
doi: 10.3724/SP.J.1146.2010.01240
Abstract:
A dual-beam spread spectrum signal based on directional modulation is proposed to increase the difficulty of the wireless communication tapping. The transmitted signal is not only associated with the spread spectrum sequence but also with the azimuth angle of the receiver. Therefore, this signal is a space spread spectrum signal modulated by the azimuth angle. Simulation results show that the proposed signal offers a safety method for the data transmission compared with the traditional spread spectrum signal.
A dual-beam spread spectrum signal based on directional modulation is proposed to increase the difficulty of the wireless communication tapping. The transmitted signal is not only associated with the spread spectrum sequence but also with the azimuth angle of the receiver. Therefore, this signal is a space spread spectrum signal modulated by the azimuth angle. Simulation results show that the proposed signal offers a safety method for the data transmission compared with the traditional spread spectrum signal.
2011, 33(10): 2322-2327.
doi: 10.3724/SP.J.1146.2011.00263
Abstract:
Cooperative transmission for cognitive radio networks not only enhances the anti-fading capability of the system, but also improves the bandwidth efficiency. But its really a worth considering issue when the relay node should assit the source node to transmit information. This paper proposes a cooperative guideline based on cooperative level. Firstly the notion of cooperative level is defined, then the expressions of system bandwidth utilization and the average symbol error rate are deduced, finally the system performance function is got through the compromise between the coorperative thresholds and power ratio. This paper also employs particle swarm optimization algorithm to solve optimal cooperative threshold and optimal power ratio. The simulation results verify the performance of the proposed scheme and show that good link state from source node to destination node and cooperative transmission by the relay node are both useful for optimizing the system performance.
Cooperative transmission for cognitive radio networks not only enhances the anti-fading capability of the system, but also improves the bandwidth efficiency. But its really a worth considering issue when the relay node should assit the source node to transmit information. This paper proposes a cooperative guideline based on cooperative level. Firstly the notion of cooperative level is defined, then the expressions of system bandwidth utilization and the average symbol error rate are deduced, finally the system performance function is got through the compromise between the coorperative thresholds and power ratio. This paper also employs particle swarm optimization algorithm to solve optimal cooperative threshold and optimal power ratio. The simulation results verify the performance of the proposed scheme and show that good link state from source node to destination node and cooperative transmission by the relay node are both useful for optimizing the system performance.
2011, 33(10): 2328-2333.
doi: 10.3724/SP.J.1146.2010.01384
Abstract:
The k-error linear complexity of the output sequences by-bit of single cycle T-function is investigated with the polynomial and the Chan Games algorithm as the main tools. The distribution of k-error linear complexity and k-error linear complexity profile of the output sequences by-bit of single cycle T-function are presented when n=2t.
The k-error linear complexity of the output sequences by-bit of single cycle T-function is investigated with the polynomial and the Chan Games algorithm as the main tools. The distribution of k-error linear complexity and k-error linear complexity profile of the output sequences by-bit of single cycle T-function are presented when n=2t.
2011, 33(10): 2334-2339.
doi: 10.3724/SP.J.1146.2010.01202
Abstract:
This paper considers the issue of finding good puncturing patterns for rate-compatible LDPC codes. When studying the puncturing of LDPC codes, Ha, et al. obtain a so-called grouping and sorting puncturing scheme to maximize the number of lower k-SR nodes. Though the grouping and sorting scheme outperforms random puncturing schemes, it guarantees only single survived check node. This paper investigates the effect of multiple survived check nodes, and proposes an effective puncturing scheme called MSCN, which maximizes the number of survived check nodes. Simulation results over AWGN channels show that the proposed MSCN scheme is superior to the grouping and sorting scheme at low rates. By theoretical analysis and experimental results, it is indicated that multiple survived check nodes enhance the decoding performance of LDPC codes.
This paper considers the issue of finding good puncturing patterns for rate-compatible LDPC codes. When studying the puncturing of LDPC codes, Ha, et al. obtain a so-called grouping and sorting puncturing scheme to maximize the number of lower k-SR nodes. Though the grouping and sorting scheme outperforms random puncturing schemes, it guarantees only single survived check node. This paper investigates the effect of multiple survived check nodes, and proposes an effective puncturing scheme called MSCN, which maximizes the number of survived check nodes. Simulation results over AWGN channels show that the proposed MSCN scheme is superior to the grouping and sorting scheme at low rates. By theoretical analysis and experimental results, it is indicated that multiple survived check nodes enhance the decoding performance of LDPC codes.
2011, 33(10): 2340-2346.
doi: 10.3724/SP.J.1146.2010.01445
Abstract:
When the service capacity of a terminal is limited, how to aggregate heterogeneous terminals according to their capacity to support service application is a challenge. This paper proposes a terminal aggregative selection algorithm based on Multi-Objective Evolutionary (MOE), describes the framework of terminal aggregation and designs 0-1 programming model. The proposed algorithm determines automatically the weights of multi-index, avoiding the difficulty to specify the weights manually. Simulation results show that the proposed algorithm can produce a set of optimal Pareto solutions and the most approving solution is selected as the final decision according to preference and application requirements. Also the proposed algorithm provides an improvement to the feasibility and efficiency.
When the service capacity of a terminal is limited, how to aggregate heterogeneous terminals according to their capacity to support service application is a challenge. This paper proposes a terminal aggregative selection algorithm based on Multi-Objective Evolutionary (MOE), describes the framework of terminal aggregation and designs 0-1 programming model. The proposed algorithm determines automatically the weights of multi-index, avoiding the difficulty to specify the weights manually. Simulation results show that the proposed algorithm can produce a set of optimal Pareto solutions and the most approving solution is selected as the final decision according to preference and application requirements. Also the proposed algorithm provides an improvement to the feasibility and efficiency.
2011, 33(10): 2347-2352.
doi: 10.3724/SP.J.1146.2011.00116
Abstract:
At present, virtual network mapping algorithms obtain suboptimal solution based on constraint condition, they still have the issues of solving mapping equations complicatedly, high computation cost and lack of specific path selection method. To address these issues, a novel virtual network mapping algorithm called Valiant Load-Balancing-Virtual Network Embedding (VLB-VNE) is proposed. VLB-VNE divides the nodes of core/backbone network into several regions. And the region has full mesh logical topological structure and valiant load-balancing routing scheme. VLB-VNE is based on greedy iterative algorithm in the region level. Theoretical analysis and simulation results prove that: VLB-VNE achieves a rational and mapping easily practical network, combines nodes and links mapping, reduces computation cost and possesses optimality of valiant load-balancing network in throughput delay and routing complexity.
At present, virtual network mapping algorithms obtain suboptimal solution based on constraint condition, they still have the issues of solving mapping equations complicatedly, high computation cost and lack of specific path selection method. To address these issues, a novel virtual network mapping algorithm called Valiant Load-Balancing-Virtual Network Embedding (VLB-VNE) is proposed. VLB-VNE divides the nodes of core/backbone network into several regions. And the region has full mesh logical topological structure and valiant load-balancing routing scheme. VLB-VNE is based on greedy iterative algorithm in the region level. Theoretical analysis and simulation results prove that: VLB-VNE achieves a rational and mapping easily practical network, combines nodes and links mapping, reduces computation cost and possesses optimality of valiant load-balancing network in throughput delay and routing complexity.
2011, 33(10): 2353-2357.
doi: 10.3724/SP.J.1146.2011.00199
Abstract:
In most mobile-assisted localization schemes, mobile anchors usually follow predefined scan trajectories or move randomly. When sensors are deployed non-uniformly in various terrains with complex shapes, random and predefined trajectories lead to wasted efforts in localization and uncertain localization performance. In this paper, by utilizing deployment topology information, a novel scheme of trajectory design for mobile anchor is proposed. Based on rigidity theory, the original network is first partitioned into localization units. The shortest path traversing all units is chosen as the trajectory of mobile anchor. Anchor moves along this path and localizes units in turn. Large scale simulations show that the new scheme avoids unnecessary movements and position broadcast efficiently and accommodates all kinds of deployment scenarios smartly. Compared with classic scan based trajectory, anchor travels at much shorter path and broadcasts much fewer positions.
In most mobile-assisted localization schemes, mobile anchors usually follow predefined scan trajectories or move randomly. When sensors are deployed non-uniformly in various terrains with complex shapes, random and predefined trajectories lead to wasted efforts in localization and uncertain localization performance. In this paper, by utilizing deployment topology information, a novel scheme of trajectory design for mobile anchor is proposed. Based on rigidity theory, the original network is first partitioned into localization units. The shortest path traversing all units is chosen as the trajectory of mobile anchor. Anchor moves along this path and localizes units in turn. Large scale simulations show that the new scheme avoids unnecessary movements and position broadcast efficiently and accommodates all kinds of deployment scenarios smartly. Compared with classic scan based trajectory, anchor travels at much shorter path and broadcasts much fewer positions.
2011, 33(10): 2358-2363.
doi: 10.3724/SP.J.1146.2011.00275
Abstract:
Considering the issue of energy consumption and robustness in three-Dimensional Wireless Sensor Networks (3D-WSN), this paper builds an energy consumption and robustness trade-off model, and proves that the model has a stable equilibrium solution with the Lyapunov stability theory, then a Topology Control Algorithm based on the Trade-off Model (TCA-TM) is proposed, the optimal topology of wireless sensor networks of 3D spatial distribution is obtained. Simulation analysis illustrates TCA-TM topology can meet the robustness requirement of networks, balance energy consumption and prolong the lifetime of networks effectively.
Considering the issue of energy consumption and robustness in three-Dimensional Wireless Sensor Networks (3D-WSN), this paper builds an energy consumption and robustness trade-off model, and proves that the model has a stable equilibrium solution with the Lyapunov stability theory, then a Topology Control Algorithm based on the Trade-off Model (TCA-TM) is proposed, the optimal topology of wireless sensor networks of 3D spatial distribution is obtained. Simulation analysis illustrates TCA-TM topology can meet the robustness requirement of networks, balance energy consumption and prolong the lifetime of networks effectively.
2011, 33(10): 2364-2371.
doi: 10.3724/SP.J.1146.2010.01332
Abstract:
Based on the high data rate evolution of next generation Wireless Local Area Network (WLAN), a cross-layer rate control algorithm of MIMO system is proposed. Firstly, the limit of physical layer rate control algorithm which maximizes the throughput of physical layer and guarantees the Bit Error Rate (BER) of traffic is analyzed. Secondly, integrated with the Adaptive Modulation and Coding (AMC) technique, a cross-layer rate control algorithm based on prediction with the purpose of maximizing the throughput of Media Access Control (MAC) layer is presented. The simulation and analysis show that sub-optimal result can be obtained with the guaranteed BER, and thereby enhances the throughput of traffic. Simplicity of calculation, accuracy of prediction and efficiency of run-time are the benefits of this algorithm. The algorithm can be used in close-loop rate control,and the scene of traffic scheduling or frame retransmission.
Based on the high data rate evolution of next generation Wireless Local Area Network (WLAN), a cross-layer rate control algorithm of MIMO system is proposed. Firstly, the limit of physical layer rate control algorithm which maximizes the throughput of physical layer and guarantees the Bit Error Rate (BER) of traffic is analyzed. Secondly, integrated with the Adaptive Modulation and Coding (AMC) technique, a cross-layer rate control algorithm based on prediction with the purpose of maximizing the throughput of Media Access Control (MAC) layer is presented. The simulation and analysis show that sub-optimal result can be obtained with the guaranteed BER, and thereby enhances the throughput of traffic. Simplicity of calculation, accuracy of prediction and efficiency of run-time are the benefits of this algorithm. The algorithm can be used in close-loop rate control,and the scene of traffic scheduling or frame retransmission.
2011, 33(10): 2372-2377.
doi: 10.3724/SP.J.1146.2011.00125
Abstract:
The sparse representation based on overcomplete dictionary is a new signal representation theory. Recent activities in this field concentrate mainly on the study of dictionary design algorithm and sparse decomposition algorithm. In this paper, a novel speech signal sparse representation algorithm is proposed based on adaptive overcomplete dictionary. Considering stationary signal with autocorrelation function of exponential decay, an adaptive overcomplete dictionary is constructed in terms of the Karhunen-Love (K-L) expansion. Furthermore, an effective algorithm based on the nonlinear approximation is proposed to obtain sparse decomposition of signal with the adaptive dictionary. The experimental results indicate that short-term stationary speech signal sparse representation based on the adaptability and algebraic structure of atom in the overcomplete dictionary has higher sparsity and better reconstructive precision. The sparse representation algorithm can preferably be used in compressed sensing.
The sparse representation based on overcomplete dictionary is a new signal representation theory. Recent activities in this field concentrate mainly on the study of dictionary design algorithm and sparse decomposition algorithm. In this paper, a novel speech signal sparse representation algorithm is proposed based on adaptive overcomplete dictionary. Considering stationary signal with autocorrelation function of exponential decay, an adaptive overcomplete dictionary is constructed in terms of the Karhunen-Love (K-L) expansion. Furthermore, an effective algorithm based on the nonlinear approximation is proposed to obtain sparse decomposition of signal with the adaptive dictionary. The experimental results indicate that short-term stationary speech signal sparse representation based on the adaptability and algebraic structure of atom in the overcomplete dictionary has higher sparsity and better reconstructive precision. The sparse representation algorithm can preferably be used in compressed sensing.
2011, 33(10): 2378-2383.
doi: 10.3724/SP.J.1146.2011.00051
Abstract:
As a nonparametric classification algorithm, K-Nearest Neighbor (KNN) is very efficient and can be easily realized. However, the traditional KNN suggests that the contributions of all K nearest neighbors are equal, which makes it easy to be disturbed by noises. Meanwhile, for large data sets, the computational demands for classifying patterns using KNN can be prohibitive. In this paper, a new Template reduction KNN algorithm based on Weighted distance (TWKNN) is proposed. Firstly, the points that are far away from the classification boundary are dropped by the template reduction technique. Then, in the process of classification, the K nearest neighbors weights of the test sample are set according to the Euclidean distance metric, which can enhance the robustness of the algorithm. Experimental results show that the proposed approach effectively reduces the number of training samples while maintaining the same level of classification accuracy as the traditional KNN.
As a nonparametric classification algorithm, K-Nearest Neighbor (KNN) is very efficient and can be easily realized. However, the traditional KNN suggests that the contributions of all K nearest neighbors are equal, which makes it easy to be disturbed by noises. Meanwhile, for large data sets, the computational demands for classifying patterns using KNN can be prohibitive. In this paper, a new Template reduction KNN algorithm based on Weighted distance (TWKNN) is proposed. Firstly, the points that are far away from the classification boundary are dropped by the template reduction technique. Then, in the process of classification, the K nearest neighbors weights of the test sample are set according to the Euclidean distance metric, which can enhance the robustness of the algorithm. Experimental results show that the proposed approach effectively reduces the number of training samples while maintaining the same level of classification accuracy as the traditional KNN.
2011, 33(10): 2384-2389.
doi: 10.3724/SP.J.1146.2011.00009
Abstract:
A blind audio watermarking algorithm with self-synchronization for copyright protection is proposed. In the application of media copyright management, the decoding results should have a time precision, better robustness and fidelity. However, most of algorithms can not provide enough robustness and time precision. To deal with these problems, in this paper, spread spectrum theory and the short-time relevance of audio signal are used to generate a watermark. To improve the fidelity of audio, a psychoacoustic auditory model is further used. Moreover, special synchronization strategy and watermark message frame structure are used to get a high time precision decoding results. Experimental results show that the watermarking scheme is robust against common audio editing attacks while keeping the watermarked audio a high perceptual quality.
A blind audio watermarking algorithm with self-synchronization for copyright protection is proposed. In the application of media copyright management, the decoding results should have a time precision, better robustness and fidelity. However, most of algorithms can not provide enough robustness and time precision. To deal with these problems, in this paper, spread spectrum theory and the short-time relevance of audio signal are used to generate a watermark. To improve the fidelity of audio, a psychoacoustic auditory model is further used. Moreover, special synchronization strategy and watermark message frame structure are used to get a high time precision decoding results. Experimental results show that the watermarking scheme is robust against common audio editing attacks while keeping the watermarked audio a high perceptual quality.
2011, 33(10): 2390-2395.
doi: 10.3724/SP.J.1146.2010.00939
Abstract:
In the existing local discriminant analysis methods, weight matrices in objective functions are determined by neighborhood relationship (in original space) of samples before they are projected, without consideration of changes of the neighborhood after the projection. In order to depict the optimization goal of classification more accurately, a local discriminant projection method based on objective space is proposed, in which weight matrices in objective function are determined by the neighborhood of projected samples, namely, neighborhood in objective space. The objective function is optimized by an iterative procedure. The underlying idea of the new method is that the desired projection should make neighbors, in objective space, of the same class close and neighbors of different class apart. Experiment results show that the method overcomes effectively the problems of local discriminant analysis in original space and achieves good performance on both synthetic data and standard data set of handwriting digital.
In the existing local discriminant analysis methods, weight matrices in objective functions are determined by neighborhood relationship (in original space) of samples before they are projected, without consideration of changes of the neighborhood after the projection. In order to depict the optimization goal of classification more accurately, a local discriminant projection method based on objective space is proposed, in which weight matrices in objective function are determined by the neighborhood of projected samples, namely, neighborhood in objective space. The objective function is optimized by an iterative procedure. The underlying idea of the new method is that the desired projection should make neighbors, in objective space, of the same class close and neighbors of different class apart. Experiment results show that the method overcomes effectively the problems of local discriminant analysis in original space and achieves good performance on both synthetic data and standard data set of handwriting digital.
2011, 33(10): 2396-2401.
doi: 10.3724/SP.J.1146.2011.00339
Abstract:
In multi-beam bathymetric sonar, noise is one of the most important disadvantageous factors that restrict the estimation precision. Fixed bandwidth filter is currently widely used to suppress noise in sonar systems. On the measuring swath, the impact of noise varies with the beam angle. Considering this issue, an algorithm of variable bandwidth filter is proposed and its parameters are given in the paper. Compared with traditional method, this algorithm can not only improve the SNR but also have less computation and the structure is suitable for fast realization on FPGA. The realization structure of the algorithm is given and the engineering possibility is proved by computer simulation. The processing results of experimental data on lake prove the effectiveness of the proposed algorithm.
In multi-beam bathymetric sonar, noise is one of the most important disadvantageous factors that restrict the estimation precision. Fixed bandwidth filter is currently widely used to suppress noise in sonar systems. On the measuring swath, the impact of noise varies with the beam angle. Considering this issue, an algorithm of variable bandwidth filter is proposed and its parameters are given in the paper. Compared with traditional method, this algorithm can not only improve the SNR but also have less computation and the structure is suitable for fast realization on FPGA. The realization structure of the algorithm is given and the engineering possibility is proved by computer simulation. The processing results of experimental data on lake prove the effectiveness of the proposed algorithm.
2011, 33(10): 2402-2406.
doi: 10.3724/SP.J.1146.2011.00255
Abstract:
To solve the problem of estimating two dimensional Direction Of Arrival (DOA) using sparse representation, a novel DOA estimation method is proposed to estimate the DOAs of two-dimensional signals based on sparse representation of space angle. So the space angle is put forward to construct the dictionary. By this way, the dimension of dictionary is reduced to one-dimension from two-dimensional space, and the length of the redundant dictionary is largely reduced. Then the algorithm is extended to frequency domain, and the frequency sparse representation of space angle method is presented. Compared with the traditional high-resolution methods, the proposed method has lower SNR threshold and smaller snaps. Theoretical analysis and simulation experiments verify the algorithm has a better performance in the aspect of precision and resolution to estimate the DOAs of two-dimensional coherent signals than the MUSIC algorithm.
To solve the problem of estimating two dimensional Direction Of Arrival (DOA) using sparse representation, a novel DOA estimation method is proposed to estimate the DOAs of two-dimensional signals based on sparse representation of space angle. So the space angle is put forward to construct the dictionary. By this way, the dimension of dictionary is reduced to one-dimension from two-dimensional space, and the length of the redundant dictionary is largely reduced. Then the algorithm is extended to frequency domain, and the frequency sparse representation of space angle method is presented. Compared with the traditional high-resolution methods, the proposed method has lower SNR threshold and smaller snaps. Theoretical analysis and simulation experiments verify the algorithm has a better performance in the aspect of precision and resolution to estimate the DOAs of two-dimensional coherent signals than the MUSIC algorithm.
2011, 33(10): 2407-2412.
doi: 10.3724/SP.J.1146.2011.00070
Abstract:
A conical polarization sensitive conformal array is structured with crossed dipole elements and its data model is built, on the basis of which, a joint two Dimensional Directional Of Arrival (2D DOA) and polarization estimation algorithm is given. In the algorithm, the 2D DOA and polarization information of incident signals are de-coupled first through appropriate transformation to manifold matrix of the array, and then they are estimated separately according to rank reduction theory and Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) algorithm. The final result of joint 2D DOA and polarization estimation is achieved by employing a new designed alternative comparing parameter match algorithm. Monte-Carlo simulation results show that the proposed algorithm is competent?to solve the multiple parameter estimation problem based on conical conformal array antenna.
A conical polarization sensitive conformal array is structured with crossed dipole elements and its data model is built, on the basis of which, a joint two Dimensional Directional Of Arrival (2D DOA) and polarization estimation algorithm is given. In the algorithm, the 2D DOA and polarization information of incident signals are de-coupled first through appropriate transformation to manifold matrix of the array, and then they are estimated separately according to rank reduction theory and Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) algorithm. The final result of joint 2D DOA and polarization estimation is achieved by employing a new designed alternative comparing parameter match algorithm. Monte-Carlo simulation results show that the proposed algorithm is competent?to solve the multiple parameter estimation problem based on conical conformal array antenna.
Precession and Structural Parameter Estimation of the Cone-shaped Warhead Based on the Micro-Doppler
2011, 33(10): 2413-2419.
doi: 10.3724/SP.J.1146.2011.00120
Abstract:
Micro-motion feature is one of the effective features used for radar target recognition in the middle section of the ballistic curve. The micro-Doppler expressions of the scattering center at the conical point and two sliding scattering centers in the conical bottom are derived, firstly. The micro-Doppler of the scattering center at the conical point calculated by its micro-Doppler expression is little different to that which is getting by the Geometrical Theory of Diffraction (GTD). The other two scattering centers micro-Doppler achieved by the two methods coincide with each other. Three correlations of the micro-Doppler of the three scattering centers are founded by analyzing their micro-Doppler expressions. Then a method of precession and structural parameter estimation is proposed by using the magnitudes of the micro-Doppler at some times，which can obtain from the time-frequency analysis. Using the method to extract six precession and structural parameters in different angles of incidence is analyzed, and the simulated results validate the effectiveness of the proposed method.
Micro-motion feature is one of the effective features used for radar target recognition in the middle section of the ballistic curve. The micro-Doppler expressions of the scattering center at the conical point and two sliding scattering centers in the conical bottom are derived, firstly. The micro-Doppler of the scattering center at the conical point calculated by its micro-Doppler expression is little different to that which is getting by the Geometrical Theory of Diffraction (GTD). The other two scattering centers micro-Doppler achieved by the two methods coincide with each other. Three correlations of the micro-Doppler of the three scattering centers are founded by analyzing their micro-Doppler expressions. Then a method of precession and structural parameter estimation is proposed by using the magnitudes of the micro-Doppler at some times，which can obtain from the time-frequency analysis. Using the method to extract six precession and structural parameters in different angles of incidence is analyzed, and the simulated results validate the effectiveness of the proposed method.
2011, 33(10): 2420-2426.
doi: 10.3724/SP.J.1146.2010.01138
Abstract:
A novel approach to moving target detection is proposed for multi-channel SAR system. This approach utilizes multistage Wiener filter to suppress clutter. To improve performance of moving target detection in heterogeneous clutter environment, this new approach also combines diagonal loading techniques and non-homogeneity detector. Experimental results on measured SAR data are presented to demonstrate that compared to conventional adaptive SAR/GMTI method, the proposed method shows better clutter suppression capability and moving target detection performance in heterogeneous clutter environment.
A novel approach to moving target detection is proposed for multi-channel SAR system. This approach utilizes multistage Wiener filter to suppress clutter. To improve performance of moving target detection in heterogeneous clutter environment, this new approach also combines diagonal loading techniques and non-homogeneity detector. Experimental results on measured SAR data are presented to demonstrate that compared to conventional adaptive SAR/GMTI method, the proposed method shows better clutter suppression capability and moving target detection performance in heterogeneous clutter environment.
2011, 33(10): 2427-2432.
doi: 10.3724/SP.J.1146.2011.00117
Abstract:
A new method is proposed to estimate micro-motion parameters of space precession targets. Based on the micro-Doppler characteristic of a precession target, the Fourier transformation is applied to estimate precession parameters roughly. Then based on the time-frequency spectrum characteristic of the echo signal, coherent accumulation is applied to obtain a 3-D high resolution distribution of the target. The estimation accuracy of the parameters is refined by calculating the whole image entropy. Simulations results confirm the effectiveness of our proposed method.
A new method is proposed to estimate micro-motion parameters of space precession targets. Based on the micro-Doppler characteristic of a precession target, the Fourier transformation is applied to estimate precession parameters roughly. Then based on the time-frequency spectrum characteristic of the echo signal, coherent accumulation is applied to obtain a 3-D high resolution distribution of the target. The estimation accuracy of the parameters is refined by calculating the whole image entropy. Simulations results confirm the effectiveness of our proposed method.
2011, 33(10): 2433-2437.
doi: 10.3724/SP.J.1146.2010.01412
Abstract:
The adaptive detection of signal embedded in compound Gaussian clutter of nonhomogeneous environments, i.e., the training samples used for adaption do not share the same covariance matrix as the vector under test is considered in this paper, and the clutter can be modeled in terms of a compound Gaussian process. With known prior and some appropriate prior distribution, based on Bayesian framework, the minimum mean square error estimation of clutter covariance matrix is proposed, and the application to the adaptive normalized matched filter test is given. The results of computer simulation are presented to illustrate that the performance of the proposed detectors is better than conventional ones, especially in the present of a small number of training data.
The adaptive detection of signal embedded in compound Gaussian clutter of nonhomogeneous environments, i.e., the training samples used for adaption do not share the same covariance matrix as the vector under test is considered in this paper, and the clutter can be modeled in terms of a compound Gaussian process. With known prior and some appropriate prior distribution, based on Bayesian framework, the minimum mean square error estimation of clutter covariance matrix is proposed, and the application to the adaptive normalized matched filter test is given. The results of computer simulation are presented to illustrate that the performance of the proposed detectors is better than conventional ones, especially in the present of a small number of training data.
2011, 33(10): 2438-2444.
doi: 10.3724/SP.J.1146.2011.00123
Abstract:
A comprehensive and systematic study of the operational imaging modes for the Spaceborne/Airborne hybrid Bistatic SAR (SA-BiSAR) is made firstly, including imaging geometry, echo equation, scene width, Doppler history, and resolutions and so on. To overcome the shortcomings of the Taylor series expansion in deriving the Bistatic Point Target Reference Spectrum (BPTRS) in conventional BPTRS-resolving methods, an exact analytical BPTRS, which is derived from the one-to-one correspondence between time and azimuth frequency with no Taylor series expansions, is proposed, and the derived result is free of constraints. Finally, the validity of the proposed solution is verified by point targets simulations.
A comprehensive and systematic study of the operational imaging modes for the Spaceborne/Airborne hybrid Bistatic SAR (SA-BiSAR) is made firstly, including imaging geometry, echo equation, scene width, Doppler history, and resolutions and so on. To overcome the shortcomings of the Taylor series expansion in deriving the Bistatic Point Target Reference Spectrum (BPTRS) in conventional BPTRS-resolving methods, an exact analytical BPTRS, which is derived from the one-to-one correspondence between time and azimuth frequency with no Taylor series expansions, is proposed, and the derived result is free of constraints. Finally, the validity of the proposed solution is verified by point targets simulations.
2011, 33(10): 2445-2451.
doi: 10.3724/SP.J.1146.2011.00225
Abstract:
This paper proposes a new full-aperture imaging algorithm for ScanSAR. Firstly, the two dimensional (2-D) spectrum is obtained by the azimuth pro-filtering which adopts the idea of SPECAN. Then the Nonlinear Chirp Scaling (NCS) method is used to complete the range compression and Range Cell Migration Correction (RCMC). After that, the signal is focused in the Doppler domain by dechirping operation. Finally, geometric distortion correction is carried out via a Chirp-Z Transform (CZT). Without interpolation and coordinate transformation, the algorithm is high in computational efficiency. Both simulation and results of real data are provided to demonstrate the effectiveness of the proposed method.
This paper proposes a new full-aperture imaging algorithm for ScanSAR. Firstly, the two dimensional (2-D) spectrum is obtained by the azimuth pro-filtering which adopts the idea of SPECAN. Then the Nonlinear Chirp Scaling (NCS) method is used to complete the range compression and Range Cell Migration Correction (RCMC). After that, the signal is focused in the Doppler domain by dechirping operation. Finally, geometric distortion correction is carried out via a Chirp-Z Transform (CZT). Without interpolation and coordinate transformation, the algorithm is high in computational efficiency. Both simulation and results of real data are provided to demonstrate the effectiveness of the proposed method.
2011, 33(10): 2452-2457.
doi: 10.3724/SP.J.1146.2011.00287
Abstract:
The number of antenna elements of MIMO radar is too many when imaging for moving target with single snapshot. To solve the problem, an imaging method for MIMO radar with sparse array is proposed. Firstly the configuration of sparse antenna array is analyzed. Then, combining Compressed Sensing (CS) theory, a novel imaging algorithm for MIMO radar with sparse array is put forward. Single snapshot imaging for moving target is implemented by this algorithm, which not only can avoid the difficulty of motion compensation aroused by the targets maneuver, but also can reduce the number of antenna, it is the advantage to engineering practice. Finally, the effectiveness of this algorithm is validated by the simulative results.
The number of antenna elements of MIMO radar is too many when imaging for moving target with single snapshot. To solve the problem, an imaging method for MIMO radar with sparse array is proposed. Firstly the configuration of sparse antenna array is analyzed. Then, combining Compressed Sensing (CS) theory, a novel imaging algorithm for MIMO radar with sparse array is put forward. Single snapshot imaging for moving target is implemented by this algorithm, which not only can avoid the difficulty of motion compensation aroused by the targets maneuver, but also can reduce the number of antenna, it is the advantage to engineering practice. Finally, the effectiveness of this algorithm is validated by the simulative results.
2011, 33(10): 2458-2463.
doi: 10.3724/SP.J.1146.2011.00012
Abstract:
Synthetic aperture radar can obtain two-dimensional high resolution radar images, but it has to work in side-looking mode without forward-looking imaging capability, and can not focus stationary and moving targets simultaneously as well. Virtual aperture on the multiple-input multiple-output theory is an efficient solution to the aforementioned new problems of radar imaging. In this paper, antenna configuration and associated image formation of virtual aperture imaging are studied. Linear virtual apertures of different antenna configurations are compared in terms of imaging performance. It is theoretically proved that two transmitting elements are placed on the ends of received array is an efficient antenna configuration scheme to form a linear virtual aperture. The analytical expression of imaging resolution of this antenna configuration is derived, which is also validated with real data.
Synthetic aperture radar can obtain two-dimensional high resolution radar images, but it has to work in side-looking mode without forward-looking imaging capability, and can not focus stationary and moving targets simultaneously as well. Virtual aperture on the multiple-input multiple-output theory is an efficient solution to the aforementioned new problems of radar imaging. In this paper, antenna configuration and associated image formation of virtual aperture imaging are studied. Linear virtual apertures of different antenna configurations are compared in terms of imaging performance. It is theoretically proved that two transmitting elements are placed on the ends of received array is an efficient antenna configuration scheme to form a linear virtual aperture. The analytical expression of imaging resolution of this antenna configuration is derived, which is also validated with real data.
2011, 33(10): 2464-2470.
doi: 10.3724/SP.J.1146.2011.00028
Abstract:
This paper focuses on the system error correction of a millimeter-wave three-baseline InSAR. The system error correction scheme is presented, in order to achieve the signal amplitude and phase consistency between three channels. The effect of pulse compression, the impact of interference between channels, system phase stability, the slow time spectrum, amplitude and phase consistency level are analyzed. The unambiguous interferometric angle method based on three-baseline and the experiment on ground is presented. The effectiveness of the method proposed and the validity of the performance of millimeter-wave three-baseline InSAR are indicated by real data results.
This paper focuses on the system error correction of a millimeter-wave three-baseline InSAR. The system error correction scheme is presented, in order to achieve the signal amplitude and phase consistency between three channels. The effect of pulse compression, the impact of interference between channels, system phase stability, the slow time spectrum, amplitude and phase consistency level are analyzed. The unambiguous interferometric angle method based on three-baseline and the experiment on ground is presented. The effectiveness of the method proposed and the validity of the performance of millimeter-wave three-baseline InSAR are indicated by real data results.
2011, 33(10): 2471-2476.
doi: 10.3724/SP.J.1146.2011.00105
Abstract:
The influence of SAR system resolution to the image power spectrum density is represented. The one-dimensional circular power spectrum of SAR image is modeled based on negative exponent function and the relationship between the SNR of scene matching and the system resolution is deduced. The equations of SAR system resolution and independent pixel number are deduced from the autocorrelation function. The impact of SAR resolution to the independent number is analyzed in theory. Finally the relationship between SAR system parameters and acquisition probability is established. The simulation and experiment show that the model could describe the relationship among the SAR system resolution and the SNR of scene matching and the image independent pixel number very well. It provides the theoretical basis for the parameter design of scene matching trimble autopilot based on SAR.
The influence of SAR system resolution to the image power spectrum density is represented. The one-dimensional circular power spectrum of SAR image is modeled based on negative exponent function and the relationship between the SNR of scene matching and the system resolution is deduced. The equations of SAR system resolution and independent pixel number are deduced from the autocorrelation function. The impact of SAR resolution to the independent number is analyzed in theory. Finally the relationship between SAR system parameters and acquisition probability is established. The simulation and experiment show that the model could describe the relationship among the SAR system resolution and the SNR of scene matching and the image independent pixel number very well. It provides the theoretical basis for the parameter design of scene matching trimble autopilot based on SAR.
2011, 33(10): 2477-2482.
doi: 10.3724/SP.J.1146.2011.00193
Abstract:
Based on the bistatic scattering coefficients deduced from perturbation method and the simulated data of bistatic sea echo spectrum, Howells algorithm is adopted to derive the wave-number spectrum and to extract the information of significant wave height and wind speed. In this paper, the applicable condition of Howells algorithm is complemented. The selection principle of the retained number of singular values of the kernel matrix is determined. Inversion results show that the inversion errors of significant wave height and wind speed decrease as the wind direction tends to perpendicular. And the inversion errors also decrease as the appropriate operating frequency is selected according to the sea state (i.e. wind speed or significant wave height). If the operating frequency and the retained number of singular values of the kernel matrix are appropriate, the inversion error of significant wave height will be less than 3% and the inversion error of wind speed will be less than 1%.
Based on the bistatic scattering coefficients deduced from perturbation method and the simulated data of bistatic sea echo spectrum, Howells algorithm is adopted to derive the wave-number spectrum and to extract the information of significant wave height and wind speed. In this paper, the applicable condition of Howells algorithm is complemented. The selection principle of the retained number of singular values of the kernel matrix is determined. Inversion results show that the inversion errors of significant wave height and wind speed decrease as the wind direction tends to perpendicular. And the inversion errors also decrease as the appropriate operating frequency is selected according to the sea state (i.e. wind speed or significant wave height). If the operating frequency and the retained number of singular values of the kernel matrix are appropriate, the inversion error of significant wave height will be less than 3% and the inversion error of wind speed will be less than 1%.
2011, 33(10): 2483-2488.
doi: 10.3724/SP.J.1146.2011.00231
Abstract:
An algorithm for multi-target three-dimensional (3D) localization in bistatic Multiple-Input Multiple- Output (MIMO) radar system with uniform linear transmit array and L-shape receive array is presented. After forming a complex matrix based on ESPRIT, the receive angles of each target can be calculated from the imaginary part and real part of each eigenvalue of that complex matrix. Then the transmit angles of each target can be obtained by utilizing eigenvectors of that complex matrix and signal subspace. The receive angles and transmit angle can be paired automatically. The proposed method does not need to know the variance of noise, and the computed load is low. Simulation results verify that the method is more effective in the low SNR condition, and the mean square errors of estimated angles are close to the Cramer Rao bound.
An algorithm for multi-target three-dimensional (3D) localization in bistatic Multiple-Input Multiple- Output (MIMO) radar system with uniform linear transmit array and L-shape receive array is presented. After forming a complex matrix based on ESPRIT, the receive angles of each target can be calculated from the imaginary part and real part of each eigenvalue of that complex matrix. Then the transmit angles of each target can be obtained by utilizing eigenvectors of that complex matrix and signal subspace. The receive angles and transmit angle can be paired automatically. The proposed method does not need to know the variance of noise, and the computed load is low. Simulation results verify that the method is more effective in the low SNR condition, and the mean square errors of estimated angles are close to the Cramer Rao bound.
2011, 33(10): 2489-2493.
doi: 10.3724/SP.J.1146.2011.00132
Abstract:
According to the signal structure of China Mobile Multimedia Broadcasting (CMMB), this paper analyzes the ambiguity function of CMMB signal as illuminator of opportunity for passive radar systems. The mechanism of these ambiguity peaks is researched and compared with Europe Digital Video Broadcasting-Terrestrial (DVB-T) signal. As for the adverse effects because of the side peaks caused by cyclic prefix and Doppler ambiguity strips due to sync-signal, a method for suppressing these ambiguities is proposed. Simulation and experimental results show that the analysis of side peaks' mechanism is correct and the method can suppress side peaks effectively, which lays the foundation for target detection.
According to the signal structure of China Mobile Multimedia Broadcasting (CMMB), this paper analyzes the ambiguity function of CMMB signal as illuminator of opportunity for passive radar systems. The mechanism of these ambiguity peaks is researched and compared with Europe Digital Video Broadcasting-Terrestrial (DVB-T) signal. As for the adverse effects because of the side peaks caused by cyclic prefix and Doppler ambiguity strips due to sync-signal, a method for suppressing these ambiguities is proposed. Simulation and experimental results show that the analysis of side peaks' mechanism is correct and the method can suppress side peaks effectively, which lays the foundation for target detection.
2011, 33(10): 2494-2499.
doi: 10.3724/SP.J.1146.2011.00147
Abstract:
In the paper, the percentage of the Intrinsic Mode Function (IMFs) energy in the whole sea clutter energy is analyzed, the percentage variation affected by the target is discussed. As shown of the results, the energy of the pure sea clutter is focused on the former 3 IMFs, but the latter 6 IMFs are pervaded by the energy of the sea clutter when the target appears, and the intrinsic mode energy entropy can describe the variational distribution of the energy when the target appears. So the intrinsic mode energy entropy is proposed to detect the weak target. Compared with the target detection method directly using the box dimension and the multi-pulses CA-CFAR (100 pulses) and the CFAR target detection method in frequency domain, the method proposed improves the detection performance of the weak target in the sea clutter distinctly.
In the paper, the percentage of the Intrinsic Mode Function (IMFs) energy in the whole sea clutter energy is analyzed, the percentage variation affected by the target is discussed. As shown of the results, the energy of the pure sea clutter is focused on the former 3 IMFs, but the latter 6 IMFs are pervaded by the energy of the sea clutter when the target appears, and the intrinsic mode energy entropy can describe the variational distribution of the energy when the target appears. So the intrinsic mode energy entropy is proposed to detect the weak target. Compared with the target detection method directly using the box dimension and the multi-pulses CA-CFAR (100 pulses) and the CFAR target detection method in frequency domain, the method proposed improves the detection performance of the weak target in the sea clutter distinctly.
2011, 33(10): 2500-2505.
doi: 10.3724/SP.J.1146.2011.00053
Abstract:
To accelerate the locking speed of the Digitally Controlled Phase-Locked Loop (DCPLL), a Dynamic Bandwidth Management (DBM) algorithm for DCPLL is presented. Only when the phase error sensed by the phase detector is less than the boundary condition for three times, the proposed algorithm decreases the DCPLL bandwidth. In addition, the proposed algorithm increases the DCPLL bandwidth immediately when the sensed phase error is larger the boundary condition. To verify the proposed algorithm, a behavioral model is developed in MATLAB environment. The simulation results show that, under the same condition, the locking time of the DCPLL with the proposed algorithm is reduced to 28.6%?85.7% of the locking time with the traditional DBM algorithm. Finally, a DCPLL is implemented by CSM 0.18 m 1P6M CMOS and tested. The measured results show that the proposed algorithm can decrease the phase error rapidly and keep the DCPLL in locking status. Therefore, the proposed algorithm can avoid the limitation of traditional DBM algorithm, decrease the probability of changing the PLL bandwidth falsely, and accelerate the locking speed.
To accelerate the locking speed of the Digitally Controlled Phase-Locked Loop (DCPLL), a Dynamic Bandwidth Management (DBM) algorithm for DCPLL is presented. Only when the phase error sensed by the phase detector is less than the boundary condition for three times, the proposed algorithm decreases the DCPLL bandwidth. In addition, the proposed algorithm increases the DCPLL bandwidth immediately when the sensed phase error is larger the boundary condition. To verify the proposed algorithm, a behavioral model is developed in MATLAB environment. The simulation results show that, under the same condition, the locking time of the DCPLL with the proposed algorithm is reduced to 28.6%?85.7% of the locking time with the traditional DBM algorithm. Finally, a DCPLL is implemented by CSM 0.18 m 1P6M CMOS and tested. The measured results show that the proposed algorithm can decrease the phase error rapidly and keep the DCPLL in locking status. Therefore, the proposed algorithm can avoid the limitation of traditional DBM algorithm, decrease the probability of changing the PLL bandwidth falsely, and accelerate the locking speed.
2011, 33(10): 2506-2510.
doi: 10.3724/SP.J.1146.2011.00085
Abstract:
Considering that the Code-Aided (CA) carrier recovery algorithms perform small synchronization range and big inaccuracy in extremely low Signal to Noise Ratio (SNR) deep space communication systems, two joint assisted carrier synchronization algorithms by code and pilot are proposed. First the Log-Likelihood-Function (LLF) of CA carrier estimation is derived by Maximum-Likelihood (ML) criterion and two new CA fine synchronization algorithms which have closed-form expression are got by simplify the Maclaurin series of LLF and its derivative. And then, a coarse synchronization algorithm is proposed based on pilot symbols in order to handle larger parameter offsets and its Mean Squared Error (MSE) is also derived. Finally, two joint assisted carrier synchronization algorithms by code and pilot are got by orderly combining the coarse estimation algorithm and fine estimation algorithm. And the simulations by the LDPC-Hadamard code with rate 1/12 verify that the new algorithm can increase synchronization range and improve accuracy, achieving perfect synchronization with a certain amount of pilot symbols at extremely low SNR.
Considering that the Code-Aided (CA) carrier recovery algorithms perform small synchronization range and big inaccuracy in extremely low Signal to Noise Ratio (SNR) deep space communication systems, two joint assisted carrier synchronization algorithms by code and pilot are proposed. First the Log-Likelihood-Function (LLF) of CA carrier estimation is derived by Maximum-Likelihood (ML) criterion and two new CA fine synchronization algorithms which have closed-form expression are got by simplify the Maclaurin series of LLF and its derivative. And then, a coarse synchronization algorithm is proposed based on pilot symbols in order to handle larger parameter offsets and its Mean Squared Error (MSE) is also derived. Finally, two joint assisted carrier synchronization algorithms by code and pilot are got by orderly combining the coarse estimation algorithm and fine estimation algorithm. And the simulations by the LDPC-Hadamard code with rate 1/12 verify that the new algorithm can increase synchronization range and improve accuracy, achieving perfect synchronization with a certain amount of pilot symbols at extremely low SNR.
2011, 33(10): 2511-2515.
doi: 10.3724/SP.J.1146.2011.00290
Abstract:
In the Orthogonal Frequency Division Multiplexing (OFDM) systems, based on the studying of Peak to Average Power Ratio (PAPR) reduction by using Partial Transmit Sequence (PTS) technology, an improved PTS scheme of multi-stage optimization is proposed. This method is to find the optimal phase rotation factors by increasing the number of optimization steps and reducing the number of pre-determined phase elements in the set of each step, and change the trend of computational complexity which is higher with more disjoint sub-blocks and more predetermined phase factors. This method can be used in conjunction with suboptimal search algorithm. Analysis of computational complexity and simulation results show that, compared with traditional scheme, this method can not only largely reduce the computational complexity, but also reduce the PAPR.
In the Orthogonal Frequency Division Multiplexing (OFDM) systems, based on the studying of Peak to Average Power Ratio (PAPR) reduction by using Partial Transmit Sequence (PTS) technology, an improved PTS scheme of multi-stage optimization is proposed. This method is to find the optimal phase rotation factors by increasing the number of optimization steps and reducing the number of pre-determined phase elements in the set of each step, and change the trend of computational complexity which is higher with more disjoint sub-blocks and more predetermined phase factors. This method can be used in conjunction with suboptimal search algorithm. Analysis of computational complexity and simulation results show that, compared with traditional scheme, this method can not only largely reduce the computational complexity, but also reduce the PAPR.
2011, 33(10): 2516-2520.
doi: 10.3724/SP.J.1146.2011.00239
Abstract:
Reasonable clustering algorithm can prolong the Large Scale Wireless Sensor Network (LS-WSN) lifetime, so as to reduce the cost of using it. Up to now, most research on WSN clustering assumes that the nodes in WSN are uniformly distributed. But this assumption is different from practical LS-WSN. In this paper, a novel clustering algorithm is proposed, which is suitable for the non-uniformly distributed LS-WSNs. In the proposed algorithm, LS-WSN is clustered according to the location aware clustering method, which based on the hexagons virtual grid, then the clusters are adjusted following a game theoretic adjustment process. After the algorithm, the numbers of nodes in each cluster is nearly similar. Theoretical analysis and simulation results show that the proposed algorithm can effectively balance the number of nodes in each cluster, thus prolonging the effective lifetime of WSN.
Reasonable clustering algorithm can prolong the Large Scale Wireless Sensor Network (LS-WSN) lifetime, so as to reduce the cost of using it. Up to now, most research on WSN clustering assumes that the nodes in WSN are uniformly distributed. But this assumption is different from practical LS-WSN. In this paper, a novel clustering algorithm is proposed, which is suitable for the non-uniformly distributed LS-WSNs. In the proposed algorithm, LS-WSN is clustered according to the location aware clustering method, which based on the hexagons virtual grid, then the clusters are adjusted following a game theoretic adjustment process. After the algorithm, the numbers of nodes in each cluster is nearly similar. Theoretical analysis and simulation results show that the proposed algorithm can effectively balance the number of nodes in each cluster, thus prolonging the effective lifetime of WSN.
2011, 33(10): 2521-2525.
doi: 10.3724/SP.J.1146.2011.00270
Abstract:
In order to achieve bit synchronization of high-dynamic and weak GPS signal, a bit synchronization method based on differential coherent accumulation is proposed, called differential accumulation method. With this method, every one of complex samples after coherent integration within a navigation data bit period is multiplied with the conjugated of the previous corresponding sample that the interval between them is an integer number of navigation data bit length and the product is accumulated, and then non-coherent accumulated as a statistic to calculate the value of the 20 candidate locations, the starting position of differential coherent accumulation corresponds with the largest value is determined as navigation data bit boundary position to perform bit synchronization. Simulation results show that the differential accumulation method is suitable for high-dynamic, weak GPS signal bit synchronization.
In order to achieve bit synchronization of high-dynamic and weak GPS signal, a bit synchronization method based on differential coherent accumulation is proposed, called differential accumulation method. With this method, every one of complex samples after coherent integration within a navigation data bit period is multiplied with the conjugated of the previous corresponding sample that the interval between them is an integer number of navigation data bit length and the product is accumulated, and then non-coherent accumulated as a statistic to calculate the value of the 20 candidate locations, the starting position of differential coherent accumulation corresponds with the largest value is determined as navigation data bit boundary position to perform bit synchronization. Simulation results show that the differential accumulation method is suitable for high-dynamic, weak GPS signal bit synchronization.
2011, 33(10): 2526-2530.
doi: 10.3724/SP.J.1146.2011.00298
Abstract:
Due to suppression the influence of impulsive noise spikes (outliers) from desired signal direction of arrival in Global Positioning System (GPS) signals, an improved Householder-based MultiStage Wiener Filter (HMSWF) is proposed. The method substitutes parts of the weights of the Householder-based MultiStage Wiener Filter for the minimal module weights, which have the minimal module of the samples quotient, and adoptes in space-time anti-jamming processing in GPS receiver. The improved method has the prominent ability of restricting the influence of the impulsive noise spikes (outliers) from desired signal direction of arrival to adaptive weights. Computational simulation results indicate the method achieves better interference suppression ability and a good performance in reducing the influence of the impulsive noise spikes (outliers) to adaptive weights.
Due to suppression the influence of impulsive noise spikes (outliers) from desired signal direction of arrival in Global Positioning System (GPS) signals, an improved Householder-based MultiStage Wiener Filter (HMSWF) is proposed. The method substitutes parts of the weights of the Householder-based MultiStage Wiener Filter for the minimal module weights, which have the minimal module of the samples quotient, and adoptes in space-time anti-jamming processing in GPS receiver. The improved method has the prominent ability of restricting the influence of the impulsive noise spikes (outliers) from desired signal direction of arrival to adaptive weights. Computational simulation results indicate the method achieves better interference suppression ability and a good performance in reducing the influence of the impulsive noise spikes (outliers) to adaptive weights.
2011, 33(10): 2531-2535.
doi: 10.3724/SP.J.1146.2011.00153
Abstract:
Since human face movements distribute on a nonlinear manifold, there are inherent alignment residuals brought by the global linearity hypothesis in the traditional Principal Component Analysis (PCA) based Active Appearance Models (AAM). In this paper, a famous manifold learning method, Local Linear Embedding (LLE) is improved to model human face shape space for reducing the inherent alignment residuals. The experimental results show that the method, LLE-AAM, obtains lower alignment residuals to the tiny alterations of human face and still make successful alignment when PCA-AAM failed to some large alterations. According to the statistical analysis, LLE-AAM could reduce the residual to a certain extent.
Since human face movements distribute on a nonlinear manifold, there are inherent alignment residuals brought by the global linearity hypothesis in the traditional Principal Component Analysis (PCA) based Active Appearance Models (AAM). In this paper, a famous manifold learning method, Local Linear Embedding (LLE) is improved to model human face shape space for reducing the inherent alignment residuals. The experimental results show that the method, LLE-AAM, obtains lower alignment residuals to the tiny alterations of human face and still make successful alignment when PCA-AAM failed to some large alterations. According to the statistical analysis, LLE-AAM could reduce the residual to a certain extent.
2011, 33(10): 2536-2540.
doi: 10.3724/SP.J.1146.2011.00363
Abstract:
Betweenness centrality is a widely used indicator to measure the node importance in complex network s, but it is computationally-expensive to calculate betweenness centrality. In this paper, analysis on the traditional betweenness centrality algorithms is completed and a novel algorithm is proposed to meet the hardware design features. Based on this algorithm, parallel computing system is implemented on FPGA with task level coarse grained parallelism and pipeline based fine grained parallelism. The experimental results show that the FPGA based implementation achieves up to 4.31 times speedup compared with an 8-core CPU implementation.
Betweenness centrality is a widely used indicator to measure the node importance in complex network s, but it is computationally-expensive to calculate betweenness centrality. In this paper, analysis on the traditional betweenness centrality algorithms is completed and a novel algorithm is proposed to meet the hardware design features. Based on this algorithm, parallel computing system is implemented on FPGA with task level coarse grained parallelism and pipeline based fine grained parallelism. The experimental results show that the FPGA based implementation achieves up to 4.31 times speedup compared with an 8-core CPU implementation.
