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2005 Vol. 27, No. 6
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2005, 27(6): 841-844.
Abstract:
In order to overcome the near-far problem encountered in CDMA mobile location estimation, in this paper a mobile location method to utilize an antenna array and TSOA/AOA hybrid location technique is proposed, the GDOP distribution of different location methods are analyzed and TSOA/AOA hybrid location algorithm are provided. Simulation results under different condition show that as far as AOA measurements is relatively accurate, mobile can be exactly located by this method.
In order to overcome the near-far problem encountered in CDMA mobile location estimation, in this paper a mobile location method to utilize an antenna array and TSOA/AOA hybrid location technique is proposed, the GDOP distribution of different location methods are analyzed and TSOA/AOA hybrid location algorithm are provided. Simulation results under different condition show that as far as AOA measurements is relatively accurate, mobile can be exactly located by this method.
2005, 27(6): 845-850.
Abstract:
This paper presents a multiuser detection algorithm for the frequency hopping MFSK (M-ary Frequency Shift Keying) multiple access systems under the assumption of ideal power control. By detecting and classifying the energy levels in the frequency hopping slots of the time-frequency matrix, the interference pattern is identified and the cochannel interference is cancelled step-by-step. Theoretical analysis and computer simulation results show that the new detector has lower complexity, better convergence stability, and is suitable for the AWGN and Rayleigh fading channels.
This paper presents a multiuser detection algorithm for the frequency hopping MFSK (M-ary Frequency Shift Keying) multiple access systems under the assumption of ideal power control. By detecting and classifying the energy levels in the frequency hopping slots of the time-frequency matrix, the interference pattern is identified and the cochannel interference is cancelled step-by-step. Theoretical analysis and computer simulation results show that the new detector has lower complexity, better convergence stability, and is suitable for the AWGN and Rayleigh fading channels.
2005, 27(6): 851-856.
Abstract:
WCDMA needs to extend its downlink data rate to lOMbps or more because of the growing demand of the Internet and multimedia services. High Speed Downlink Packet Access (HSDPA) has been proposed to offer such high data rates in WCDMA technology within current 5MHz bandwidth. In order to enhance the performance of HSDPA, a novel receiver combined LMMSE chip equalizer and Interference Weighted Canceller (LMMSE-IWC) is presented. Theoretical analysis and computer simulations show that the performance of LMMSE-IWC is superior to conventional Rake, LMMSE chip equalizer.
WCDMA needs to extend its downlink data rate to lOMbps or more because of the growing demand of the Internet and multimedia services. High Speed Downlink Packet Access (HSDPA) has been proposed to offer such high data rates in WCDMA technology within current 5MHz bandwidth. In order to enhance the performance of HSDPA, a novel receiver combined LMMSE chip equalizer and Interference Weighted Canceller (LMMSE-IWC) is presented. Theoretical analysis and computer simulations show that the performance of LMMSE-IWC is superior to conventional Rake, LMMSE chip equalizer.
2005, 27(6): 857-860.
Abstract:
Against the character of HF channels, this paper presents an OFDM synchronization detection scheme, which uses m sequence to modulate the pilot symbols. Based on joint time and frequency-offset estimation, synchronization detection can be implemented using the correlation peak of the m sequence in low SNR. Theoretical analysis shows the right selection of range for decision threshold. Monte Carlo simulation results show the scheme has good performance with a reliable detection probability and a low false alarm probability under low SNR( - 10dB).
Against the character of HF channels, this paper presents an OFDM synchronization detection scheme, which uses m sequence to modulate the pilot symbols. Based on joint time and frequency-offset estimation, synchronization detection can be implemented using the correlation peak of the m sequence in low SNR. Theoretical analysis shows the right selection of range for decision threshold. Monte Carlo simulation results show the scheme has good performance with a reliable detection probability and a low false alarm probability under low SNR( - 10dB).
2005, 27(6): 861-864.
Abstract:
The influence of Doppler shifts on traditional acquisition algorithms is analyzed. A new method for spread-spectrum code acquisition of pilot symbols in the presence of large Doppler shifts is proposed, in which the outputs of partial matched filters are delivered to an Adaptive Line Enhancer (ALE) directly and an estimated frequency is produced. After frequency offset compensation, spread-spectrum code acquisition is performed by traditional spread-spectrum code acquisition algorithm. Simulation results show that the new method eliminates the influence of large Doppler shifts effectively, with fast acquisition time.
The influence of Doppler shifts on traditional acquisition algorithms is analyzed. A new method for spread-spectrum code acquisition of pilot symbols in the presence of large Doppler shifts is proposed, in which the outputs of partial matched filters are delivered to an Adaptive Line Enhancer (ALE) directly and an estimated frequency is produced. After frequency offset compensation, spread-spectrum code acquisition is performed by traditional spread-spectrum code acquisition algorithm. Simulation results show that the new method eliminates the influence of large Doppler shifts effectively, with fast acquisition time.
2005, 27(6): 865-869.
Abstract:
This paper proposes a hierarchical coding technique based on the All Phase Inverse Discrete Cosine Transform (APIDCT) interpolation. The All Phase Digital Filter (APDF) is a new type of linear phase filter. This paper compares the performances of several kinds of APDF and demonstrates that the APIDCT filter has the best performance in image interpolation. By combining the interpolation filter with multi-subsampling and adaptive arithmetic coding, a simple hierarchical image coding method is shaped up. This technique can be used to scalable coding in spatial resolution. Simulation results show that the compression ratio and restored image quality better than JPEG11 compression can be achieved by only three layers, and no block effect is found even in high compression ratio.
This paper proposes a hierarchical coding technique based on the All Phase Inverse Discrete Cosine Transform (APIDCT) interpolation. The All Phase Digital Filter (APDF) is a new type of linear phase filter. This paper compares the performances of several kinds of APDF and demonstrates that the APIDCT filter has the best performance in image interpolation. By combining the interpolation filter with multi-subsampling and adaptive arithmetic coding, a simple hierarchical image coding method is shaped up. This technique can be used to scalable coding in spatial resolution. Simulation results show that the compression ratio and restored image quality better than JPEG11 compression can be achieved by only three layers, and no block effect is found even in high compression ratio.
2005, 27(6): 870-873.
Abstract:
The differential provable security of a kind of unbalanced Feistel networks is investigated deeply. The structure of the differential correspondence between round functions whose differential probability is nonzero is given. A distribution of m sequential differential correspondences is given. If pmalt is the maximum of the probability of round function f(x), the upperbounds of the differential probability over at least 2m rounds is proven to be two times of the square of pmax and is proven to be the square of pmax when f(k, xm) is bijective. In conclusion, the unbalanced Feistel networks is discussed.
The differential provable security of a kind of unbalanced Feistel networks is investigated deeply. The structure of the differential correspondence between round functions whose differential probability is nonzero is given. A distribution of m sequential differential correspondences is given. If pmalt is the maximum of the probability of round function f(x), the upperbounds of the differential probability over at least 2m rounds is proven to be two times of the square of pmax and is proven to be the square of pmax when f(k, xm) is bijective. In conclusion, the unbalanced Feistel networks is discussed.
2005, 27(6): 874-878.
Abstract:
Through analyzing the nature of the evolution of the deterministic chaos and partitioning its state space, a deterministic chaotic system can be turned into an ergodic information source which could be used to design a Random Number Generator(RNG). The characteristics of a chaotic piecewise-linear map are also analyzed, for instance, chaotic attractor and point attractor, source entropy and redundancy, as well as the distribution of the sequence generated by the map. Further, the map is implemented in TSMC O.25um CMOS mixed-signal process utilizing switched capacitor circuit techniques. The test results indicate very good performance in anti-jamming.
Through analyzing the nature of the evolution of the deterministic chaos and partitioning its state space, a deterministic chaotic system can be turned into an ergodic information source which could be used to design a Random Number Generator(RNG). The characteristics of a chaotic piecewise-linear map are also analyzed, for instance, chaotic attractor and point attractor, source entropy and redundancy, as well as the distribution of the sequence generated by the map. Further, the map is implemented in TSMC O.25um CMOS mixed-signal process utilizing switched capacitor circuit techniques. The test results indicate very good performance in anti-jamming.
2005, 27(6): 879-883.
Abstract:
In this paper, a novel method of calculating the correlative dimension of time-series is proposed. With this method, the fractal scaleless band of time-series can be identified and the correlative dimension of time series can be calculated according to the parameters given. The results of theory analysis and Monte Carlo simulation show that the method is efficient and objective in identifying the fractal scaleless band of time-series and calculating the correlative dimension of time series.
In this paper, a novel method of calculating the correlative dimension of time-series is proposed. With this method, the fractal scaleless band of time-series can be identified and the correlative dimension of time series can be calculated according to the parameters given. The results of theory analysis and Monte Carlo simulation show that the method is efficient and objective in identifying the fractal scaleless band of time-series and calculating the correlative dimension of time series.
2005, 27(6): 884-887.
Abstract:
In speech signal transmission system, residual redundancy is still left in the parameters after source encoding. The redundancy includes non-uniform distribution and time correlation of subsequent frame. Exploiting the redundancy on bit-level, the paper is proposed iterative algorithm based on soft-in/soft-out channel and parameter estimation, and applies the algorithm to GSM EFR system. The result shows this method reduces the BER and improves SNR of decoded speech.
In speech signal transmission system, residual redundancy is still left in the parameters after source encoding. The redundancy includes non-uniform distribution and time correlation of subsequent frame. Exploiting the redundancy on bit-level, the paper is proposed iterative algorithm based on soft-in/soft-out channel and parameter estimation, and applies the algorithm to GSM EFR system. The result shows this method reduces the BER and improves SNR of decoded speech.
2005, 27(6): 888-891.
Abstract:
This paper analyzes theoretically the properties of Turbo codes and the effects of the interleaver. Some elements for devising good interleaver are pointed out in this paper. Compared with some traditional algorithms, a low-complexity method based on three-Dimensional (3-D) matrix is proposed. The simulation results demonstrate its good performance.
This paper analyzes theoretically the properties of Turbo codes and the effects of the interleaver. Some elements for devising good interleaver are pointed out in this paper. Compared with some traditional algorithms, a low-complexity method based on three-Dimensional (3-D) matrix is proposed. The simulation results demonstrate its good performance.
2005, 27(6): 892-895.
Abstract:
The offset of gain filter is dealt unsuitably with a constant 32dB in G.728 standard. That is, the short-term stationary speech signal during the duration 20~30ms is unsuitably supposed as stationary at whole time axis. It is necessary to design optimizing hybrid window for improving gain filter. In this paper, the exact expression of excitation gain is derived and an estimation method of SNRav used to optimize the parameters of hybrid window is presented. On the basis of above, this paper combines the Jayant adaptive quantization and G.728s gain prediction to propose a scheme fit for designing gain codebook of Low Delay Code Excited Linear Prediction(LD-CELP), in which the exact gain value is adaptively predicted and quantized. In this method, for adaptive quantization gain of 3 bit and 4 bit, the SNR increases by 0.5 and 6 dB separately than that of G.728. If adopting 4 bit adaptive quantization and the shape codebook of 64 codevectors, the G.728 complexity can reduce by 20% while SNR has 1 dB improvement.
The offset of gain filter is dealt unsuitably with a constant 32dB in G.728 standard. That is, the short-term stationary speech signal during the duration 20~30ms is unsuitably supposed as stationary at whole time axis. It is necessary to design optimizing hybrid window for improving gain filter. In this paper, the exact expression of excitation gain is derived and an estimation method of SNRav used to optimize the parameters of hybrid window is presented. On the basis of above, this paper combines the Jayant adaptive quantization and G.728s gain prediction to propose a scheme fit for designing gain codebook of Low Delay Code Excited Linear Prediction(LD-CELP), in which the exact gain value is adaptively predicted and quantized. In this method, for adaptive quantization gain of 3 bit and 4 bit, the SNR increases by 0.5 and 6 dB separately than that of G.728. If adopting 4 bit adaptive quantization and the shape codebook of 64 codevectors, the G.728 complexity can reduce by 20% while SNR has 1 dB improvement.
2005, 27(6): 896-899.
Abstract:
Based on the analysis of the effect on the linearization about the measurement equation and state equation, aimed to some system with linear state equation, a new algorithm named as Transforming State Space Extended Kalman Filter (TSS-EKF) is proposed to improve the robust of EKF. Simulation in single observer passive location and tracking validates that this algorithm is robust.
Based on the analysis of the effect on the linearization about the measurement equation and state equation, aimed to some system with linear state equation, a new algorithm named as Transforming State Space Extended Kalman Filter (TSS-EKF) is proposed to improve the robust of EKF. Simulation in single observer passive location and tracking validates that this algorithm is robust.
2005, 27(6): 900-904.
Abstract:
In the applications of wavelet, it is the most difficult and cumbrous to select the suitable wavelet bases. In this paper, a general construction method of biorthogonal bases of perfect reconstruction wavelet is proposed by using the transmission functions or filters. According to the conclusion, something only to do is to choice the suitable coefficients a,y(co) for constructing the wavelet bases of perfect reconstruction which has special properties. So, this conclusion is important to the applications of wavelet.
In the applications of wavelet, it is the most difficult and cumbrous to select the suitable wavelet bases. In this paper, a general construction method of biorthogonal bases of perfect reconstruction wavelet is proposed by using the transmission functions or filters. According to the conclusion, something only to do is to choice the suitable coefficients a,y(co) for constructing the wavelet bases of perfect reconstruction which has special properties. So, this conclusion is important to the applications of wavelet.
2005, 27(6): 905-907.
Abstract:
The correlation dimension is an important parameter for describing a chaotic signal. The method of extracting the correlation dimension is deeply researched in this paper. Based on the GP method, an improved algorithm of extracting the correlation dimension is given. The algorithm has the character of little calculating amount, higher accuracy and smaller aimless ability of scaling selection.
The correlation dimension is an important parameter for describing a chaotic signal. The method of extracting the correlation dimension is deeply researched in this paper. Based on the GP method, an improved algorithm of extracting the correlation dimension is given. The algorithm has the character of little calculating amount, higher accuracy and smaller aimless ability of scaling selection.
2005, 27(6): 908-913.
Abstract:
In this paper, by using the advantage of an extremely efficient and highly parallelizable algorithm deriving from the multiscaie stochastic model to deal with a lot of practical problem, a general qth-order tree-based method for multiscale modeling of stochastic dynamic processes is developed. Firstly, using the property of conditional independence of Markov processes, a qth-order tree-based method for multiscale representation of a class of process is presented. Secondly, the representation forms of the parameters in the model, such as the state transition matrix, the disturbance matrix, the initial state and the corresponding covariance are deduced by example in detail based on
In this paper, by using the advantage of an extremely efficient and highly parallelizable algorithm deriving from the multiscaie stochastic model to deal with a lot of practical problem, a general qth-order tree-based method for multiscale modeling of stochastic dynamic processes is developed. Firstly, using the property of conditional independence of Markov processes, a qth-order tree-based method for multiscale representation of a class of process is presented. Secondly, the representation forms of the parameters in the model, such as the state transition matrix, the disturbance matrix, the initial state and the corresponding covariance are deduced by example in detail based on
2005, 27(6): 914-918.
Abstract:
It is the first time to expound the watermark application under images uniting in this paper. With the affecting of JPEG lossy compressing, the universal solving scheme is proposed, and the corresponding security analysis is made. In the direction of this scheme, a watermark algorithm is proposed which can resist the JPEG lossy compressing and images uniting question. The test results prove its both characters.
It is the first time to expound the watermark application under images uniting in this paper. With the affecting of JPEG lossy compressing, the universal solving scheme is proposed, and the corresponding security analysis is made. In the direction of this scheme, a watermark algorithm is proposed which can resist the JPEG lossy compressing and images uniting question. The test results prove its both characters.
2005, 27(6): 919-923.
Abstract:
Under the requirement of running control system of remote sensing satellite station system, a running control scheme of information processing of station system based on message queues middleware - IBM WebShpere MQ is proposed. And the scheme is applied to the practical project successfully. So the scheme can be applied to the running control of integration system of multi-satellite and multi-mission remote sensing satellite constellation station system directly.
Under the requirement of running control system of remote sensing satellite station system, a running control scheme of information processing of station system based on message queues middleware - IBM WebShpere MQ is proposed. And the scheme is applied to the practical project successfully. So the scheme can be applied to the running control of integration system of multi-satellite and multi-mission remote sensing satellite constellation station system directly.
2005, 27(6): 924-927.
Abstract:
In this paper, a remote sensing images matching method based on Zernike moments and steady genetic algorithms is proposed. Genetic algorithms, which are rapid and efficient in global finding optima, are used to match the images. Considering rotation distortion, the Zernike moments of remote sensing images are used as similarity measurements. The results confirm the proposed algorithm can overcome the distortion of images and improve the efficiency while guarantee the accuracy.
In this paper, a remote sensing images matching method based on Zernike moments and steady genetic algorithms is proposed. Genetic algorithms, which are rapid and efficient in global finding optima, are used to match the images. Considering rotation distortion, the Zernike moments of remote sensing images are used as similarity measurements. The results confirm the proposed algorithm can overcome the distortion of images and improve the efficiency while guarantee the accuracy.
2005, 27(6): 928-931.
Abstract:
Different data sets relative to the same scene acquired with different view angles can be exploited to improve slant-range resolution of SAR in broadside mode. Distributed satellites SAR is a special kind of SAR system, whose transmitters and receivers are placed separately and work in different mode (broadside mode and squint mode). In this paper, data sets acquired from distributed satellites SAR system is discussed. It points out that, different angles between the radar Line Of Sight (LOS) and the satellites vertical orbital plane correspond to different bands of the ground reflectivitys spectrum. Therefore, the range resolution can be improved by using combined spectra. In addition, the influence of distributed satellites SAR systems parameters on spectral synthesis is also discussed.
Different data sets relative to the same scene acquired with different view angles can be exploited to improve slant-range resolution of SAR in broadside mode. Distributed satellites SAR is a special kind of SAR system, whose transmitters and receivers are placed separately and work in different mode (broadside mode and squint mode). In this paper, data sets acquired from distributed satellites SAR system is discussed. It points out that, different angles between the radar Line Of Sight (LOS) and the satellites vertical orbital plane correspond to different bands of the ground reflectivitys spectrum. Therefore, the range resolution can be improved by using combined spectra. In addition, the influence of distributed satellites SAR systems parameters on spectral synthesis is also discussed.
2005, 27(6): 932-935.
Abstract:
Motion error problem for airborne formation flying InSAR is analyzed. The plane interval changes (across track baseline changes) are discussed in three situations: interval increasing, interval decreasing, interval changing according to sine curve. Phase changes with baseline changes are derived quantificationally. The simulation result of plane interval changes and velocity difference are given out. Azimuth slope eliminating is adopted. Two control points are set in topographic area to compensate the phase error of baseline changes. This algorithm can improve the digital elevation model precision for whole area. The simulation results prove that the analysis is right.
Motion error problem for airborne formation flying InSAR is analyzed. The plane interval changes (across track baseline changes) are discussed in three situations: interval increasing, interval decreasing, interval changing according to sine curve. Phase changes with baseline changes are derived quantificationally. The simulation result of plane interval changes and velocity difference are given out. Azimuth slope eliminating is adopted. Two control points are set in topographic area to compensate the phase error of baseline changes. This algorithm can improve the digital elevation model precision for whole area. The simulation results prove that the analysis is right.
2005, 27(6): 936-938.
Abstract:
SAR with Displaced Phase Centers multibeam in Azimuth (DPCA) can solve the confliction between swath width and resolution, but this mode is one Pulse Repetition Frequency (PRF) restriction. In this paper, the spectrum of the signal in the azimuth direction is analyzed, and the reconstruction method of the uniform spectrum in azimuth is given when PRF deviated from the ideal PRF. DPCA with PRF alterable mode is introduced. The simulation of point target is used to analyze the effect of this new method.
SAR with Displaced Phase Centers multibeam in Azimuth (DPCA) can solve the confliction between swath width and resolution, but this mode is one Pulse Repetition Frequency (PRF) restriction. In this paper, the spectrum of the signal in the azimuth direction is analyzed, and the reconstruction method of the uniform spectrum in azimuth is given when PRF deviated from the ideal PRF. DPCA with PRF alterable mode is introduced. The simulation of point target is used to analyze the effect of this new method.
2005, 27(6): 939-942.
Abstract:
The moving parts of an aircraft, such as rotor blades, propeller blades, and jet engine compressor and turbine blades, cause a periodic modulation on the radar return signals. Though this periodic modulation can sometimes effect the Doppler tracking of the target, it can also provide important information for target identification as a radar signature. The phenomenon of the spectrum envelope modulation is analyzed in terms of electromagnetic scattering computation and experimental results of rotating blades. The results show that the blade twist is one of the important factor that impacting the spectrum distribution.
The moving parts of an aircraft, such as rotor blades, propeller blades, and jet engine compressor and turbine blades, cause a periodic modulation on the radar return signals. Though this periodic modulation can sometimes effect the Doppler tracking of the target, it can also provide important information for target identification as a radar signature. The phenomenon of the spectrum envelope modulation is analyzed in terms of electromagnetic scattering computation and experimental results of rotating blades. The results show that the blade twist is one of the important factor that impacting the spectrum distribution.
2005, 27(6): 943-947.
Abstract:
A MAC protocol, termed Dual Busy Tone Multiple Access(DBTMA), is a random access mechanism with high channel utilization for WLAN. However, it is difficult to realize the protocol with hardware. This paper proposes a new random access mechanism based on OFDM system by making simple modification on DBTMA and integrating it with power awase multi-access protocol with signalling. Furthermore, the new protocol is analysed and the result indicates that the proposed random access system shows well performance and is easy to be realized.
A MAC protocol, termed Dual Busy Tone Multiple Access(DBTMA), is a random access mechanism with high channel utilization for WLAN. However, it is difficult to realize the protocol with hardware. This paper proposes a new random access mechanism based on OFDM system by making simple modification on DBTMA and integrating it with power awase multi-access protocol with signalling. Furthermore, the new protocol is analysed and the result indicates that the proposed random access system shows well performance and is easy to be realized.
2005, 27(6): 948-951.
Abstract:
In this paper, a Dynamic Shared-Path Protection (DSPP) algorithm is proposed for double-link failures in WDM mesh networks on the condition that all links are assumed to be Share Risk Link Group (SRLG) disjoint. DSPP can dynamically adjust the link-cost according to the current state of the network, and it searches a minimum cost primary path and two minimum cost and SRLG-disjoint backup paths for each connection request, Under dynamic traffic with different load, the performances of DSPP have been investigated via simulations. The results show that DSPP not only can completely protect double-link failures but also can make the tradeoffs between the resource utilization ratio, blocking ratio, and protection-switching time.
In this paper, a Dynamic Shared-Path Protection (DSPP) algorithm is proposed for double-link failures in WDM mesh networks on the condition that all links are assumed to be Share Risk Link Group (SRLG) disjoint. DSPP can dynamically adjust the link-cost according to the current state of the network, and it searches a minimum cost primary path and two minimum cost and SRLG-disjoint backup paths for each connection request, Under dynamic traffic with different load, the performances of DSPP have been investigated via simulations. The results show that DSPP not only can completely protect double-link failures but also can make the tradeoffs between the resource utilization ratio, blocking ratio, and protection-switching time.
2005, 27(6): 952-956.
Abstract:
Finding the path satisfying two additive QoS constraints is the key question of QoS research. The linear search algorithm is one of important approximation algorithms. This paper proposes a new linear search algorithm combined with the reverse optimization scheme. If the path found by the linear search procedure does not satisfy the QoS constraints, the proper nodes of the path are chosen to make the reverse optimization. The time complexity of proposed algorithm is 0(K(m+nlog2(n))). The simulation shows that the new approach extends the search fields and improves the succeeding ratio of finding the feasible paths.
Finding the path satisfying two additive QoS constraints is the key question of QoS research. The linear search algorithm is one of important approximation algorithms. This paper proposes a new linear search algorithm combined with the reverse optimization scheme. If the path found by the linear search procedure does not satisfy the QoS constraints, the proper nodes of the path are chosen to make the reverse optimization. The time complexity of proposed algorithm is 0(K(m+nlog2(n))). The simulation shows that the new approach extends the search fields and improves the succeeding ratio of finding the feasible paths.
2005, 27(6): 957-961.
Abstract:
To deploy a multi-cell 802.11 wireless LAN system, Access Point(AP) placement and channel assignment are two primaiy design issues. For a given set of traffic demands, maximizing not only the overall system throughput, but also the fairness in resource sharing among users are aimed at, which is measured by a throughput balance index. Unlike conventional approaches that decouple AP placement and channel assignment into two phases, jointly solving the two problems for better performance is proposed. Due to the high computational complexity involved in the exhaustive searching, an efficient local searching algorithm, called patching algorithm, is designed. The simulation results show that for a typical indoor environment, patching algorithm can provide a close-to-optimal performance with much lower time complexity than the exhaustive searching.
To deploy a multi-cell 802.11 wireless LAN system, Access Point(AP) placement and channel assignment are two primaiy design issues. For a given set of traffic demands, maximizing not only the overall system throughput, but also the fairness in resource sharing among users are aimed at, which is measured by a throughput balance index. Unlike conventional approaches that decouple AP placement and channel assignment into two phases, jointly solving the two problems for better performance is proposed. Due to the high computational complexity involved in the exhaustive searching, an efficient local searching algorithm, called patching algorithm, is designed. The simulation results show that for a typical indoor environment, patching algorithm can provide a close-to-optimal performance with much lower time complexity than the exhaustive searching.
2005, 27(6): 962-966.
Abstract:
A novel medium access control algorithm is proposed in this paper. With the information of nodes Multi-Packet Reception (MPR) ability and the seeds used for producing the scheduling list, the optimal probability to access channel is determined, and the MPR ability is efficiently exploited thereby so as to improve the throughput performance of the networks. Finally, the paper tests the performance of the algorithm with an analytic model, and compares the results with the clustered protocol.
A novel medium access control algorithm is proposed in this paper. With the information of nodes Multi-Packet Reception (MPR) ability and the seeds used for producing the scheduling list, the optimal probability to access channel is determined, and the MPR ability is efficiently exploited thereby so as to improve the throughput performance of the networks. Finally, the paper tests the performance of the algorithm with an analytic model, and compares the results with the clustered protocol.
2005, 27(6): 967-972.
Abstract:
The Medium Access Control (MAC) mechanism plays a key role on supporting Quality of Service (QoS) in wireless ad hoc networks. Based on the analysis to Packet Reservation Multiple Access (PRMA), this paper gives a new MAC scheme, Distributed- PRMA (D-PRMA), which can reserve bandwidth for real-time services. D-PRMA is distributed, which is required for wireless ad hoc networks. At the same time, D-PRMA supports real-time services whose rates are different, avoids the fragment and reassembly of packets, and makes the collision duration short-lived. By simulation, the performance of D-PRMA is evaluated. The simulation results prove that D-PRMA can guarantee the bandwidth and delay of the real-time services.
The Medium Access Control (MAC) mechanism plays a key role on supporting Quality of Service (QoS) in wireless ad hoc networks. Based on the analysis to Packet Reservation Multiple Access (PRMA), this paper gives a new MAC scheme, Distributed- PRMA (D-PRMA), which can reserve bandwidth for real-time services. D-PRMA is distributed, which is required for wireless ad hoc networks. At the same time, D-PRMA supports real-time services whose rates are different, avoids the fragment and reassembly of packets, and makes the collision duration short-lived. By simulation, the performance of D-PRMA is evaluated. The simulation results prove that D-PRMA can guarantee the bandwidth and delay of the real-time services.
2005, 27(6): 973-977.
Abstract:
Protection switching is a key technique in Resilient Packet Ring(RPR). Although current protection switching scheme defined in 1EEE802.17 draft can provide sub-50ms protection switching time, it can not ensure QoS of real time service. To solve this problem, two new protection switching schemes are presented in this paper. These two schemes are respectively suitable for the two structures of RPR MAC: single-queue MAC and dual-queue MAC. The performances of these two schemes are also analyzed in this paper. Simulation results show that these schemes can ensure QoS of real-time service when protection switching occurs.
Protection switching is a key technique in Resilient Packet Ring(RPR). Although current protection switching scheme defined in 1EEE802.17 draft can provide sub-50ms protection switching time, it can not ensure QoS of real time service. To solve this problem, two new protection switching schemes are presented in this paper. These two schemes are respectively suitable for the two structures of RPR MAC: single-queue MAC and dual-queue MAC. The performances of these two schemes are also analyzed in this paper. Simulation results show that these schemes can ensure QoS of real-time service when protection switching occurs.
2005, 27(6): 978-982.
Abstract:
The rapid development of E-business network management has been promoting the broad applications on multi-mobile agents system. However, it made routing security management of this system more complex and flexible. Aimed at multi-mobile agents system, this paper proposes a new scheme of routing security management. Based on the idea of Guard Agent (Proxy Agent) whose responsibility is protecting Task Agent, this scheme introduces Trust Mechanism Verification Server and modifies the structure of traditional routing tables. It makes full use of the advantages of multi-mobile agents cooperation interaction, improves the safety and efficiency of routing and ensures optimization.
The rapid development of E-business network management has been promoting the broad applications on multi-mobile agents system. However, it made routing security management of this system more complex and flexible. Aimed at multi-mobile agents system, this paper proposes a new scheme of routing security management. Based on the idea of Guard Agent (Proxy Agent) whose responsibility is protecting Task Agent, this scheme introduces Trust Mechanism Verification Server and modifies the structure of traditional routing tables. It makes full use of the advantages of multi-mobile agents cooperation interaction, improves the safety and efficiency of routing and ensures optimization.
2005, 27(6): 983-986.
Abstract:
The number of linear independent steering vectors effected by an ElectroMagnetic (EM) Vector Sensor (VS) and an EMVS array in cumulant domain is investigated in this paper. The upper bound and the lower bound for the number of linear independent steering vectors are both derived. The conclusions are useful for determining the number of non-Gaussian narrow-band signals whose DOAs can be uniquely identified by one EMVS or an array comprising multiple EMVSs. Simulation results validate the present derivations.
The number of linear independent steering vectors effected by an ElectroMagnetic (EM) Vector Sensor (VS) and an EMVS array in cumulant domain is investigated in this paper. The upper bound and the lower bound for the number of linear independent steering vectors are both derived. The conclusions are useful for determining the number of non-Gaussian narrow-band signals whose DOAs can be uniquely identified by one EMVS or an array comprising multiple EMVSs. Simulation results validate the present derivations.
2005, 27(6): 987-990.
Abstract:
The analytical solution of spherical vector wave functions of electromagnetic fields in s-concentric homogeneous plasma anisotropic spheres is expanded in this paper. Applying the continuous boundary conditions of electromagnetic fields in (s-1) plasma anisotropic spherical shells surfaces, the unknown expansion coefficients in homogeneous s-concentric spheres and the scattering field in free space by a plane wave are derived. The numerical results are consistent by the presented method and Method of Moments (MOM) speeded up with the Conjugate-Gradient Fast-Fourier-Transform (CG-FFT) approach. A three-layer concentric plasma anisotropic spheres (the three permittivity tensors are similar) is calculated also, which conforms with the published results of the homogeneous plasma sphere. The findings presented in this paper may be applied in manufacture of new antenna, satellite communication, and other related areas.
The analytical solution of spherical vector wave functions of electromagnetic fields in s-concentric homogeneous plasma anisotropic spheres is expanded in this paper. Applying the continuous boundary conditions of electromagnetic fields in (s-1) plasma anisotropic spherical shells surfaces, the unknown expansion coefficients in homogeneous s-concentric spheres and the scattering field in free space by a plane wave are derived. The numerical results are consistent by the presented method and Method of Moments (MOM) speeded up with the Conjugate-Gradient Fast-Fourier-Transform (CG-FFT) approach. A three-layer concentric plasma anisotropic spheres (the three permittivity tensors are similar) is calculated also, which conforms with the published results of the homogeneous plasma sphere. The findings presented in this paper may be applied in manufacture of new antenna, satellite communication, and other related areas.
2005, 27(6): 991-994.
Abstract:
A method obtaining broad-band EGB(Electromagnetic Band-Gap) Structure is studied in this paper. The simulated results show that the band-width of band-gap is enlarged using method of changing period linearly, and the smoothness of pass band and band-gap are imprved using techniques of windowing units size. For the example presented in this paper, -20dB bandwithd of band-gap is increased by 20%, and the insertion loss is less than 04dB for pass-band below 3GHz. Several circuits are manufactured, and the measured results are basically accordant to simulated results.
A method obtaining broad-band EGB(Electromagnetic Band-Gap) Structure is studied in this paper. The simulated results show that the band-width of band-gap is enlarged using method of changing period linearly, and the smoothness of pass band and band-gap are imprved using techniques of windowing units size. For the example presented in this paper, -20dB bandwithd of band-gap is increased by 20%, and the insertion loss is less than 04dB for pass-band below 3GHz. Several circuits are manufactured, and the measured results are basically accordant to simulated results.
2005, 27(6): 995-998.
Abstract:
A method to effectively measure the microwave field distribution is proposed in this paper. Firstly, to quantitatively measure the intense microwave field power distribution, a measurement container and a multiplex temperature sampling and processing system are designed. Then two algorithms are manipulated to make adjustment to the sampling data. Experimental results of power field in microwave field are provided. It is feasible, dependable and also valuable for practice.
A method to effectively measure the microwave field distribution is proposed in this paper. Firstly, to quantitatively measure the intense microwave field power distribution, a measurement container and a multiplex temperature sampling and processing system are designed. Then two algorithms are manipulated to make adjustment to the sampling data. Experimental results of power field in microwave field are provided. It is feasible, dependable and also valuable for practice.
2005, 27(6): 999-1001.
Abstract:
The dynamic measurement scheme based on single camera for the airborne InSAR baseline is described in this paper. In the above measurement scheme, the calibrated camera is mainly responsible for taking pictures on the pre-designed legends on the antennas of the InSAR system at a reasonable frequency. The 3D coordinates of the antenna phase centers are calculated by the collinear equations and backward intersection algorithm. The scheme is verified feasible by the static and dynamic tests.
The dynamic measurement scheme based on single camera for the airborne InSAR baseline is described in this paper. In the above measurement scheme, the calibrated camera is mainly responsible for taking pictures on the pre-designed legends on the antennas of the InSAR system at a reasonable frequency. The 3D coordinates of the antenna phase centers are calculated by the collinear equations and backward intersection algorithm. The scheme is verified feasible by the static and dynamic tests.
2005, 27(6): 1002-1004.
Abstract:
Decision Feedback Equalizer (DFE) is widely used in practice, which is usually designed according to Minimum Mean Square Error (MMSE) criterion. A novel method is derived for calculating the DFE coefficients based on quadratic programming. Simulations show that the new method is equal to the traditional one.
Decision Feedback Equalizer (DFE) is widely used in practice, which is usually designed according to Minimum Mean Square Error (MMSE) criterion. A novel method is derived for calculating the DFE coefficients based on quadratic programming. Simulations show that the new method is equal to the traditional one.
2005, 27(6): 1005-1008.
Abstract:
Adaptive modulation can improve the system performance with high spectral efficiency. In this paper, a combining scheme of MC-CDMA and adaptive modulation is proposed in order to achieve the frequency diversity and the spectral efficiency without loss of much BER performance. The performance of the MC-CDMA system with adaptive modulation is analyzed. Simulation results also indicate the combining schemes and the channel environment will affect the efficiency of adaptive modulation algorithm in MC-CDMA systems.
Adaptive modulation can improve the system performance with high spectral efficiency. In this paper, a combining scheme of MC-CDMA and adaptive modulation is proposed in order to achieve the frequency diversity and the spectral efficiency without loss of much BER performance. The performance of the MC-CDMA system with adaptive modulation is analyzed. Simulation results also indicate the combining schemes and the channel environment will affect the efficiency of adaptive modulation algorithm in MC-CDMA systems.
