ISSN 
2008 Vol. 37, No. 2
2008, 37(2): 161-167.
Abstract:
IMT-Advanced is a tentative name used for the fourth-generation mobile communication system, which is the successor system to IMT-2000. In order to provide higher data rate and solve the issues which limit development of wireless communication system, IMT-Advanced should make breakthrough in notions and technologies. This paper starts by analyzing the principal characteristics of IMT-Advanced system, and then brings forward three problems which should be solved emergently. Indubitably, how to address the Base Stations, how to reduce transmission power, and how to allocate the frequency band are the inextricable problems to next generation communication systems. Finally, the potential key technologies related are analyzed briefly.
IMT-Advanced is a tentative name used for the fourth-generation mobile communication system, which is the successor system to IMT-2000. In order to provide higher data rate and solve the issues which limit development of wireless communication system, IMT-Advanced should make breakthrough in notions and technologies. This paper starts by analyzing the principal characteristics of IMT-Advanced system, and then brings forward three problems which should be solved emergently. Indubitably, how to address the Base Stations, how to reduce transmission power, and how to allocate the frequency band are the inextricable problems to next generation communication systems. Finally, the potential key technologies related are analyzed briefly.
2008, 37(2): 168-171.
Abstract:
A main problem in current countermeasures of side channel attack on PKC is the cost of compromising computational efficiency. Against the problem, a cryptographic implementation for modular exponentiation over finite field by coding with equivalent power consumption is presented for the goal of thwarting side channel attacks by erasing the difference of power consumption among the operational components. It is demonstrated that the expected goal of preventing timing measurement and power attack is reached to. Finally, it comes to the conclusion that one needs not compromise the computational efficiency on modular exponentiation in order to thwart side channel attack.
A main problem in current countermeasures of side channel attack on PKC is the cost of compromising computational efficiency. Against the problem, a cryptographic implementation for modular exponentiation over finite field by coding with equivalent power consumption is presented for the goal of thwarting side channel attacks by erasing the difference of power consumption among the operational components. It is demonstrated that the expected goal of preventing timing measurement and power attack is reached to. Finally, it comes to the conclusion that one needs not compromise the computational efficiency on modular exponentiation in order to thwart side channel attack.
2008, 37(2): 172-174.
Abstract:
Aiming at the drawbacks of proxy blind signature scheme, we propose a new improved proxy blind signature scheme to overcome the forgery factors. In the blind signature, a strong blind signature is constructed with three random factors. It has really completed unforgeablity and unlinkability in the electronic tractions of business in contrast against the previous ones.
Aiming at the drawbacks of proxy blind signature scheme, we propose a new improved proxy blind signature scheme to overcome the forgery factors. In the blind signature, a strong blind signature is constructed with three random factors. It has really completed unforgeablity and unlinkability in the electronic tractions of business in contrast against the previous ones.
2008, 37(2): 175-177.
Abstract:
Due to eliminating the inherent key escrow in identity-based cryptosystem and yet not needing certificates to guarantee the authenticity of public keys, the concept of certificateless public key cryptosystem is introduced. In this paper, a new certificateless signature scheme based on bilinear pairings is present. The signing algorithm of the proposed scheme is very simple and does not require any pairing computation, and the verification algorithm only needs three pairings computation. Furthermore, the scheme does not need special hash function. Our proposed scheme is more efficient than all knowing schemes in terms of computation overhead.
Due to eliminating the inherent key escrow in identity-based cryptosystem and yet not needing certificates to guarantee the authenticity of public keys, the concept of certificateless public key cryptosystem is introduced. In this paper, a new certificateless signature scheme based on bilinear pairings is present. The signing algorithm of the proposed scheme is very simple and does not require any pairing computation, and the verification algorithm only needs three pairings computation. Furthermore, the scheme does not need special hash function. Our proposed scheme is more efficient than all knowing schemes in terms of computation overhead.
2008, 37(2): 178-180,281.
Abstract:
To reduce computational complexity of the optimal multi-user detector, a novel hybrid algorithm that employs particle swarm optimization algorithm (PSO) and Hopfield neural network is presented. Then we design a novel multi-user detector in code-division multiple-access (CDMA) communication systems. Using this approach, the Hopfield neural network is embedded into the PSO to improve further the performance of the population at each generation. Such a hybridization of the PSO with the Hopfield neural network reduces its computational complexity by providing faster convergence. Simulation results are provided to show that the proposed detector has significant performance improvements over the detectors based on Hopfield neural network, genetic algorithm, and particle swarm optimization in terms of multiple access interference and near-far resistance.
To reduce computational complexity of the optimal multi-user detector, a novel hybrid algorithm that employs particle swarm optimization algorithm (PSO) and Hopfield neural network is presented. Then we design a novel multi-user detector in code-division multiple-access (CDMA) communication systems. Using this approach, the Hopfield neural network is embedded into the PSO to improve further the performance of the population at each generation. Such a hybridization of the PSO with the Hopfield neural network reduces its computational complexity by providing faster convergence. Simulation results are provided to show that the proposed detector has significant performance improvements over the detectors based on Hopfield neural network, genetic algorithm, and particle swarm optimization in terms of multiple access interference and near-far resistance.
2008, 37(2): 181-183.
Abstract:
Where the approximate processing leads error problems. In this paper, a new natural gradient blind equalization algorithm based on BSS is proposed. The underlying prior knowledge of source signals constellation is made full use of and a multi-stage clustering method is adopted to solve multi-peak problem in the new algorithm. Simulation results show that the new algorithm has higher accuracy than those only based on BBS and has higher convergence speed and less inter-symbol interference.
Where the approximate processing leads error problems. In this paper, a new natural gradient blind equalization algorithm based on BSS is proposed. The underlying prior knowledge of source signals constellation is made full use of and a multi-stage clustering method is adopted to solve multi-peak problem in the new algorithm. Simulation results show that the new algorithm has higher accuracy than those only based on BBS and has higher convergence speed and less inter-symbol interference.
2008, 37(2): 184-187.
Abstract:
In this paper, we propose aimple and efficient algorithm for code timing acquisition in direct-sequence code-division multiple-access communication system. The essential assumption is that an unmodulated pilot channel is available for the desired user. Then the correlation matrix of sampled data, where the suitable time lag is selected, contains the timing information only of desired user, while the contributions of uncorrelated interferences and noise are suppressed out. The experiment results show that more interference suppression and correct synchronization probability are achieved comparing to the conventional approach.
In this paper, we propose aimple and efficient algorithm for code timing acquisition in direct-sequence code-division multiple-access communication system. The essential assumption is that an unmodulated pilot channel is available for the desired user. Then the correlation matrix of sampled data, where the suitable time lag is selected, contains the timing information only of desired user, while the contributions of uncorrelated interferences and noise are suppressed out. The experiment results show that more interference suppression and correct synchronization probability are achieved comparing to the conventional approach.
2008, 37(2): 188-190,296.
Abstract:
Aiming at the two contrary viewpoints about the effects of mutual coupling on spatial correlation, two mutual coupling compensation techniques are employed to derive the channel capacity of multi-antenna system. Based on the electromagnetic numeric method and Monte Carlo method, it is pointed out that the effects of mutual coupling are also determined by the spatial channel parameters under the ray tracing model. As the mean angle of arrival varying, the effects of the mutual coupling will change from a detrimental factor to the beneficial ones. The equivalency of these two viewpoints is illuminated by the numeric results under Kronecker channel model.
Aiming at the two contrary viewpoints about the effects of mutual coupling on spatial correlation, two mutual coupling compensation techniques are employed to derive the channel capacity of multi-antenna system. Based on the electromagnetic numeric method and Monte Carlo method, it is pointed out that the effects of mutual coupling are also determined by the spatial channel parameters under the ray tracing model. As the mean angle of arrival varying, the effects of the mutual coupling will change from a detrimental factor to the beneficial ones. The equivalency of these two viewpoints is illuminated by the numeric results under Kronecker channel model.
2008, 37(2): 191-193,220.
Abstract:
Symbol timing delay can be estimated by employing cyclostationarity features of signals. The super performance of estimators is based on large numbers of statistical information. Thus, the observation interval is required to be quite long. However, the performance of estimators become complex when the frequency offset is considered. Due to this problem, the effect of frequency offset and the choice of parameters under this circumstance are studied. Simulation results show that the effect of frequency offset can not be ignored, especially when the observation interval is quite long. In practice, the effect of frequency offset must be considered when choosing the rational parameters.
Symbol timing delay can be estimated by employing cyclostationarity features of signals. The super performance of estimators is based on large numbers of statistical information. Thus, the observation interval is required to be quite long. However, the performance of estimators become complex when the frequency offset is considered. Due to this problem, the effect of frequency offset and the choice of parameters under this circumstance are studied. Simulation results show that the effect of frequency offset can not be ignored, especially when the observation interval is quite long. In practice, the effect of frequency offset must be considered when choosing the rational parameters.
2008, 37(2): 194-197.
Abstract:
In this paper, a new observation function of BLAST-OFDM system under non-gaussian noise is proposed, which is used for frequency selective fading channels and non-gaussian noise in application environment of BLAST system. With QR decomposition of the channel matrix, the static observation function of BLAST-OFDM system is transformed into a dynamic state space model, and then the particle filter is used for space-frequency layered detection. Making the full use of the finite alphabet of the digital modulated communication signal, the optimal proposal distribution can be chosen to produce particle and update the weight. When incorporated with current method of reducing error propagation, a new space-time layered detection algorithm is proposed. Simulation result shows the validity of the proposed algorithm.
In this paper, a new observation function of BLAST-OFDM system under non-gaussian noise is proposed, which is used for frequency selective fading channels and non-gaussian noise in application environment of BLAST system. With QR decomposition of the channel matrix, the static observation function of BLAST-OFDM system is transformed into a dynamic state space model, and then the particle filter is used for space-frequency layered detection. Making the full use of the finite alphabet of the digital modulated communication signal, the optimal proposal distribution can be chosen to produce particle and update the weight. When incorporated with current method of reducing error propagation, a new space-time layered detection algorithm is proposed. Simulation result shows the validity of the proposed algorithm.
2008, 37(2): 198-201.
Abstract:
The modified recursion lest squares (RLS) channel estimation method exploits preamble training sequences and adaptive forgetting factor to estimate channel state parameters without any prior statistics knowledge of channel in multiple input multiple outputorthogonal frequency division multiplexing (MIMO-OFDM) systems. Simulation results confirm that the RLS channel estimation method with adaptive forgetting factor (RLS-A) outperforms that with conventional forgetting factor (RLS-C) or with two-step forgetting factor (RLS-T) in both estimation accuracy and robustness. Therefore, the modified RLS channel estimation method can satisfy the requirement of the receiver for MIMO-OFDM systems.
The modified recursion lest squares (RLS) channel estimation method exploits preamble training sequences and adaptive forgetting factor to estimate channel state parameters without any prior statistics knowledge of channel in multiple input multiple outputorthogonal frequency division multiplexing (MIMO-OFDM) systems. Simulation results confirm that the RLS channel estimation method with adaptive forgetting factor (RLS-A) outperforms that with conventional forgetting factor (RLS-C) or with two-step forgetting factor (RLS-T) in both estimation accuracy and robustness. Therefore, the modified RLS channel estimation method can satisfy the requirement of the receiver for MIMO-OFDM systems.
2008, 37(2): 202-205.
Abstract:
For the multiple-input multiple output(MIMO) system without beamforming, this paper proposes an algorithm using the spacial correlation of the interference signal to cancel the co-channel interference, and presents the ML algorithm for estimating this correlation. The simulation results demonstrates that this algorithm has a 3dB gain at BER=10-2 than the method of treating the interference as Gaussian noise in 2×2 Alamouti scheme, and 2×4 has a distinct advantage in 2×4 multiplexing scheme with a strong interference.
For the multiple-input multiple output(MIMO) system without beamforming, this paper proposes an algorithm using the spacial correlation of the interference signal to cancel the co-channel interference, and presents the ML algorithm for estimating this correlation. The simulation results demonstrates that this algorithm has a 3dB gain at BER=10-2 than the method of treating the interference as Gaussian noise in 2×2 Alamouti scheme, and 2×4 has a distinct advantage in 2×4 multiplexing scheme with a strong interference.
2008, 37(2): 206-209.
Abstract:
Symbol-by-symbol detection and sequence detection are adopted in differential frequency-hopping (DFH) system. With these two detection methods, the synchronous multi-user performances of DFH system are analyzed over Rayleigh-fading channels. Simulations validate the analyses. The results of analyses and simulations prove that the DFH system with sequence detection can achieve better synchronous multi-user performance than that of conventional frequency-hopping (FH) systems.
Symbol-by-symbol detection and sequence detection are adopted in differential frequency-hopping (DFH) system. With these two detection methods, the synchronous multi-user performances of DFH system are analyzed over Rayleigh-fading channels. Simulations validate the analyses. The results of analyses and simulations prove that the DFH system with sequence detection can achieve better synchronous multi-user performance than that of conventional frequency-hopping (FH) systems.
2008, 37(2): 210-213.
Abstract:
Three main digital methods for linear frequency modulated (LFM) waveform generation are compared and analyzed. On the basis of the waveform storage method, a digital generation system scheme for ultra wide-band LFM pulse compression signals is proposed in this paper. The performances of the digital system is investigated in detail including the effects of amplitude quantization bits and the sampling frequency at digital base-band, the non-idealization of the quadrature modulator, spurs involved in the frequency multiplier, and the distortion of intermediate frequency LFM signals in time domain on the performance of output signals. The results are finally proved by computer simulations and therefore provide important theoretical bases and experiential references for parameters selection, performance evaluation, and performance optimization of ultra wide-band systems.
Three main digital methods for linear frequency modulated (LFM) waveform generation are compared and analyzed. On the basis of the waveform storage method, a digital generation system scheme for ultra wide-band LFM pulse compression signals is proposed in this paper. The performances of the digital system is investigated in detail including the effects of amplitude quantization bits and the sampling frequency at digital base-band, the non-idealization of the quadrature modulator, spurs involved in the frequency multiplier, and the distortion of intermediate frequency LFM signals in time domain on the performance of output signals. The results are finally proved by computer simulations and therefore provide important theoretical bases and experiential references for parameters selection, performance evaluation, and performance optimization of ultra wide-band systems.
2008, 37(2): 214-217.
Abstract:
This paper analyses the principle of frequency-phase scanning 3-D radar and the necessity of target IF return simulation and proposes a complete and accurate model of target IF return and its realization method. The research result is applied to evaluate the performance of frequency-phase scanning 3-D radar successfully.
This paper analyses the principle of frequency-phase scanning 3-D radar and the necessity of target IF return simulation and proposes a complete and accurate model of target IF return and its realization method. The research result is applied to evaluate the performance of frequency-phase scanning 3-D radar successfully.
2008, 37(2): 218-220.
Abstract:
The receiver autonomous integrity monitoring (RAEM) uses the redundant measurements to detect and exclude fault. The probability of missed detection is high when using the current RAIM algorithm in fault detection. An improved RAIM algorithm which can reduce the probability of missed detection is presented in this paper. The approach of fault detection and identification based on least squares residuals method is studied. The experimental results in a certain type of receiver indicate that this algorithm is effective.
The receiver autonomous integrity monitoring (RAEM) uses the redundant measurements to detect and exclude fault. The probability of missed detection is high when using the current RAIM algorithm in fault detection. An improved RAIM algorithm which can reduce the probability of missed detection is presented in this paper. The approach of fault detection and identification based on least squares residuals method is studied. The experimental results in a certain type of receiver indicate that this algorithm is effective.
2008, 37(2): 221-224.
Abstract:
Based on the method of finite difference time domain (FDTD), the analysis of the distribution of localized specific absorption in human tissues is made under the two electromagnetic radiation sources. In this paper, the imitative analysis and calculation on specific absorption rate (SAR) to the part of human body is achieved, especially head phantom, using 3D numerical electromagnetic computer software. Simulation results show that the distribution of absorption dosage of electromagnetic radiation to human body is of very asymmetry, which is effected by many parameters, such as radiant frequency, radiant intensity, exposure time, conductivity and permittivity of human tissues. Therefore, it will reduce the SAR to the human body by reducing electrical current on the surface of mobile telephone and avoiding resonance frequency of human body.
Based on the method of finite difference time domain (FDTD), the analysis of the distribution of localized specific absorption in human tissues is made under the two electromagnetic radiation sources. In this paper, the imitative analysis and calculation on specific absorption rate (SAR) to the part of human body is achieved, especially head phantom, using 3D numerical electromagnetic computer software. Simulation results show that the distribution of absorption dosage of electromagnetic radiation to human body is of very asymmetry, which is effected by many parameters, such as radiant frequency, radiant intensity, exposure time, conductivity and permittivity of human tissues. Therefore, it will reduce the SAR to the human body by reducing electrical current on the surface of mobile telephone and avoiding resonance frequency of human body.
2008, 37(2): 225-228.
Abstract:
The focusing algorithms are the key to solve the wideband signal direction of arrival (DOA) problem. Classical wideband focusing DOA estimation algorithms have such demerits as demond of initial information of DOA and several iterations as well as bad performance for real-time applications. A new type algorithm based on wideband focusing theory is presented in this paper. It does not require pre-estimations and iterations. The optimal criterion of this algorithm is the minimum mean square error (MMSE). This algorithm has the advantage of the low computational complexity for the real-time applications. Simulation based on MATLAB shows the high performance of the proposed algorithm in planar uniform circle microphone array with eight elements.
The focusing algorithms are the key to solve the wideband signal direction of arrival (DOA) problem. Classical wideband focusing DOA estimation algorithms have such demerits as demond of initial information of DOA and several iterations as well as bad performance for real-time applications. A new type algorithm based on wideband focusing theory is presented in this paper. It does not require pre-estimations and iterations. The optimal criterion of this algorithm is the minimum mean square error (MMSE). This algorithm has the advantage of the low computational complexity for the real-time applications. Simulation based on MATLAB shows the high performance of the proposed algorithm in planar uniform circle microphone array with eight elements.
2008, 37(2): 229-231.
Abstract:
The technique about how to use pipeline architecture to design high speed square root hardware is illustrated through the process of designing a square root circuit of 32 bits integer. By taking into account of the capacity of FPGA, the resources consumed by the square root hardware is analyzed. The new method to solve the extraction of a root is presented, which can deal with the 32 bits sampled data within a clock period. This method is of high precision, fast speed, easily realization. Compared with the conventional one, the division operations are avoided completely in the new algorithm. Thus, the speed of radication has increased by one time.
The technique about how to use pipeline architecture to design high speed square root hardware is illustrated through the process of designing a square root circuit of 32 bits integer. By taking into account of the capacity of FPGA, the resources consumed by the square root hardware is analyzed. The new method to solve the extraction of a root is presented, which can deal with the 32 bits sampled data within a clock period. This method is of high precision, fast speed, easily realization. Compared with the conventional one, the division operations are avoided completely in the new algorithm. Thus, the speed of radication has increased by one time.
2008, 37(2): 232-234,292.
Abstract:
This paper investigates the phenomenon of stochastic resonance of an over-damped second-order linear system, whose intrinsic frequency and the driving signal frequency is perturbed by colored noise. Based on linear-system theory and the correlation deletion method, the explicit expression of the output amplitude gain (OAG) of the system is obtained. It is shown that the OAG is a non-monotonic function of the strength, the correlation rate of the colored noise, and the frequency of the driving signal. By choosing appropriate parameters of the noise and the system, the OAG of the noisy system can be larger than that of the noise-free system, so the OAG can be increased by changed the parameters of the noise the system.
This paper investigates the phenomenon of stochastic resonance of an over-damped second-order linear system, whose intrinsic frequency and the driving signal frequency is perturbed by colored noise. Based on linear-system theory and the correlation deletion method, the explicit expression of the output amplitude gain (OAG) of the system is obtained. It is shown that the OAG is a non-monotonic function of the strength, the correlation rate of the colored noise, and the frequency of the driving signal. By choosing appropriate parameters of the noise and the system, the OAG of the noisy system can be larger than that of the noise-free system, so the OAG can be increased by changed the parameters of the noise the system.
2008, 37(2): 235-237,296.
Abstract:
The four-dimensional hyperchaos Liu system is built by adding an additional state into the three-order Liu system. Some of its basic dynamical properties are studied briefly, such as the feature of equilibrium, the hyperchaos attractor, Lyapunov exponent and fractal dimension. An electronic circuit is designed to realize the four-dimensional hyperchaos Liu system. A method of chaos synchronization between the four-dimensional hyperchaos Liu system and its duplicate system using nonlinear feedback control is proposed. Based on the stability theory, the functions of the nonlinear feedback control are determined and the range of feedback gain is derived.
The four-dimensional hyperchaos Liu system is built by adding an additional state into the three-order Liu system. Some of its basic dynamical properties are studied briefly, such as the feature of equilibrium, the hyperchaos attractor, Lyapunov exponent and fractal dimension. An electronic circuit is designed to realize the four-dimensional hyperchaos Liu system. A method of chaos synchronization between the four-dimensional hyperchaos Liu system and its duplicate system using nonlinear feedback control is proposed. Based on the stability theory, the functions of the nonlinear feedback control are determined and the range of feedback gain is derived.
2008, 37(2): 238-240,243.
Abstract:
Delay fault testing usually requires the application of consecutive two-pattern tests, which include multiple input change (MIC) test sequences and single input change (SIC) test sequences. SIC has been designated to be more effective than MIC when high robust delay fault coverage is targeted in a series of previous theoretical and experimental results. In this paper, a novel accumulator-based BIST test pattern generator (TPG) scheme is proposed for delay fault testing. Compared with previous schemes, ours has two merits:low hardware overhead and low time overhead. As accumulators are available in many very large scale integration circuits and can be reused, the proposed scheme does not introduce much hardware overhead and performance degradation and hence can be applied effectively as built in self test (BIST) test pattern generator for robustly delay fault testing.
Delay fault testing usually requires the application of consecutive two-pattern tests, which include multiple input change (MIC) test sequences and single input change (SIC) test sequences. SIC has been designated to be more effective than MIC when high robust delay fault coverage is targeted in a series of previous theoretical and experimental results. In this paper, a novel accumulator-based BIST test pattern generator (TPG) scheme is proposed for delay fault testing. Compared with previous schemes, ours has two merits:low hardware overhead and low time overhead. As accumulators are available in many very large scale integration circuits and can be reused, the proposed scheme does not introduce much hardware overhead and performance degradation and hence can be applied effectively as built in self test (BIST) test pattern generator for robustly delay fault testing.
2008, 37(2): 241-243.
Abstract:
In the application, fast Fourier transform (FFT) algorithm's speed is fast but its precision is worse whereas MUSIC algorithm has a higher precision but its real time aspect is worse. This paper analyses the characteristics of FFT algorithm and MUSIC algorithm. Using FFT algorithm to pre-estimate a signal harmonic frequency and select some effective frequecy range before using MUSIC algorithm to complete frequency search we can reduce the search area and the processing time of MUSIC algorithm greatly.
In the application, fast Fourier transform (FFT) algorithm's speed is fast but its precision is worse whereas MUSIC algorithm has a higher precision but its real time aspect is worse. This paper analyses the characteristics of FFT algorithm and MUSIC algorithm. Using FFT algorithm to pre-estimate a signal harmonic frequency and select some effective frequecy range before using MUSIC algorithm to complete frequency search we can reduce the search area and the processing time of MUSIC algorithm greatly.
2008, 37(2): 244-247.
Abstract:
A kind of media access control (MAC) protocol for data link based on dynamic priority polling mechanism is Proposed, Using OPNET, this article constructs the simulating model of a time division multiple access (TDMA) data link based on dynamic priority polling mechanism, describes modeling process, and provides and analyses simulated results of a TDMA data link's capability from four aspects:common ground station's login time, network throughput, channel using efficiency, and media access delay. Simulation results show that TDMA data link's throughput with dynamic priority polling mechanism is high, and it has excellent network access efficiency and controllability.
A kind of media access control (MAC) protocol for data link based on dynamic priority polling mechanism is Proposed, Using OPNET, this article constructs the simulating model of a time division multiple access (TDMA) data link based on dynamic priority polling mechanism, describes modeling process, and provides and analyses simulated results of a TDMA data link's capability from four aspects:common ground station's login time, network throughput, channel using efficiency, and media access delay. Simulation results show that TDMA data link's throughput with dynamic priority polling mechanism is high, and it has excellent network access efficiency and controllability.
2008, 37(2): 248-250,308.
Abstract:
A millimeter-wave transceiver with two-receiver ways and one-transmitter way is designed. It can be used for a millimeter radar. The frequency of the two-ways receiver is converted to 50 MHz from Ka-band by twice mixing. Whereas in the transmitter way, two up-converters make 50 MHz signal transfer to millimeter-wave band. Based on the analysis about the design principle of T/R moudle and various kinds of scheme, the transceiver is fabricated and tested. The performance of a power output of 1.0 W at Ka-band, a noise figure of 4.5 dB, a receiver gain of 100 dB is achieved.
A millimeter-wave transceiver with two-receiver ways and one-transmitter way is designed. It can be used for a millimeter radar. The frequency of the two-ways receiver is converted to 50 MHz from Ka-band by twice mixing. Whereas in the transmitter way, two up-converters make 50 MHz signal transfer to millimeter-wave band. Based on the analysis about the design principle of T/R moudle and various kinds of scheme, the transceiver is fabricated and tested. The performance of a power output of 1.0 W at Ka-band, a noise figure of 4.5 dB, a receiver gain of 100 dB is achieved.
2008, 37(2): 251-254.
Abstract:
The effects caused by disorder, rotating and cutting in left-handed materials (LHM) are investigated. The negative refraction effect and the transmission coefficients of various shapes of LHM are simulated by CST software based on finite integration technique. The Extracted real parts of the permittivity, permeability, and index of refraction for the standard LHM are compared with those of disordered LHM. It is found that the disorder on the split ring resonators results in a lower left-handed transmission and narrower pass bands. The left-handed transmission peak disappears when the cells of LHM are rotated. The cuts of LHM in different directions destroy the properties of LHM in different degrees.
The effects caused by disorder, rotating and cutting in left-handed materials (LHM) are investigated. The negative refraction effect and the transmission coefficients of various shapes of LHM are simulated by CST software based on finite integration technique. The Extracted real parts of the permittivity, permeability, and index of refraction for the standard LHM are compared with those of disordered LHM. It is found that the disorder on the split ring resonators results in a lower left-handed transmission and narrower pass bands. The left-handed transmission peak disappears when the cells of LHM are rotated. The cuts of LHM in different directions destroy the properties of LHM in different degrees.
2008, 37(2): 255-257,304.
Abstract:
This paper suggests an improved speech enhancement method based on human auditory masking properties. In this method, an improved noise estimation algorithm is used, then, the estimated results can be used to compute the masking threshold of the speech, after that, the coefficients of time and frequency are adjusted according to perception. The results show that the improved method leads to better signal to noise ratio, significant reduction of background noise, and unnatural structure of the residual noise.
This paper suggests an improved speech enhancement method based on human auditory masking properties. In this method, an improved noise estimation algorithm is used, then, the estimated results can be used to compute the masking threshold of the speech, after that, the coefficients of time and frequency are adjusted according to perception. The results show that the improved method leads to better signal to noise ratio, significant reduction of background noise, and unnatural structure of the residual noise.
2008, 37(2): 258-261.
Abstract:
Given the complexity of the functionality of system on chip (SOC), one of the main challenges of current IC design is no more than verification. We implemente a functional virtual prototype (FVP) according to the blueprint of unified verification methodology to solve the synchronization between design and verification in SOC development. The FVP is based on three levels of models:system-level, behavior-level, and register transfer level (RTL). The efficiency of verification can be improved by using FVP as a system-level model.
Given the complexity of the functionality of system on chip (SOC), one of the main challenges of current IC design is no more than verification. We implemente a functional virtual prototype (FVP) according to the blueprint of unified verification methodology to solve the synchronization between design and verification in SOC development. The FVP is based on three levels of models:system-level, behavior-level, and register transfer level (RTL). The efficiency of verification can be improved by using FVP as a system-level model.
2008, 37(2): 262-265.
Abstract:
In unstructured Peer-to-Peer (P2P) systems such as Gnutella, the general routing search mechanism used is to blindly flood a query to the network among peers. However, the blindly flooding search mechanism makes the whole network subjected to distributed denial of service (DDoS) attacks. In order to alleviate or minimize the bad effect due to behavior of malicious nodes making use of the flooding search mechanism, we propose the Markov-based evaluation (ME) mechanism in which reputation is applied as incentive pattern called a trusted based incentive scheme. Trust based incentive is enabled by evaluating the transaction history of the peer and changing the peer's significance or capacity within the P2P network based on this evaluation. Our simulation study shows that this approach can effectively isolate the malicious peer and its message transmitting and improve resilience against DDoS attack.
In unstructured Peer-to-Peer (P2P) systems such as Gnutella, the general routing search mechanism used is to blindly flood a query to the network among peers. However, the blindly flooding search mechanism makes the whole network subjected to distributed denial of service (DDoS) attacks. In order to alleviate or minimize the bad effect due to behavior of malicious nodes making use of the flooding search mechanism, we propose the Markov-based evaluation (ME) mechanism in which reputation is applied as incentive pattern called a trusted based incentive scheme. Trust based incentive is enabled by evaluating the transaction history of the peer and changing the peer's significance or capacity within the P2P network based on this evaluation. Our simulation study shows that this approach can effectively isolate the malicious peer and its message transmitting and improve resilience against DDoS attack.
2008, 37(2): 266-269.
Abstract:
This paper defines the importance of attack features using conditional rough entropy of knowledge and presentes a parallel algorithm of optimal feature selection in intrusion data based on conditional rough entropy. The algorithm divides the decision table of intrusion data into several sub-tables, and then the conditional rough entropy is used for the parallel computing of the sub-tables. Finally, the original decision table reduction is obtained based on the part reduction results from the sub-tables. The proposed algorithm has good performance and is good at dealing with the huge volume of data. The experimental results show that it is effective to reduce the storage requirements of the dataset and the computational cost, and it can increase the detection speed and without sacrificing the detection correctness by using the reduced feature subset.
This paper defines the importance of attack features using conditional rough entropy of knowledge and presentes a parallel algorithm of optimal feature selection in intrusion data based on conditional rough entropy. The algorithm divides the decision table of intrusion data into several sub-tables, and then the conditional rough entropy is used for the parallel computing of the sub-tables. Finally, the original decision table reduction is obtained based on the part reduction results from the sub-tables. The proposed algorithm has good performance and is good at dealing with the huge volume of data. The experimental results show that it is effective to reduce the storage requirements of the dataset and the computational cost, and it can increase the detection speed and without sacrificing the detection correctness by using the reduced feature subset.
2008, 37(2): 270-273.
Abstract:
The theory of high speed TCP congestion control algorithms are analysized in this paper. The improvement speed of TCP congestion window dynamically with bandwidth of bottleneck connection is modified, the improvement of congestion window is classified into high speed TCP and traditions TCP mode, and the switch between with them depends on the changing trend of RTT. Simulation shows that high speed TCP can modify the congestion window when the bandwidth is not fully use. And it also can change bandwidth from fully used condition into not fully used.
The theory of high speed TCP congestion control algorithms are analysized in this paper. The improvement speed of TCP congestion window dynamically with bandwidth of bottleneck connection is modified, the improvement of congestion window is classified into high speed TCP and traditions TCP mode, and the switch between with them depends on the changing trend of RTT. Simulation shows that high speed TCP can modify the congestion window when the bandwidth is not fully use. And it also can change bandwidth from fully used condition into not fully used.
2008, 37(2): 274-277.
Abstract:
In order to detect distributed denial of service (DDoS) attacks with support vector machine (SVM) measures, the feature vectors that can distinguish normal stream from attack stream are required. According to the characters of DDoS attacks, a group of relative value features are proposed. For indicating the existence and attack intensity of DDoS attack simultaneously, multi-class SVM (MCSVM) is introduced to detecting DDoS Attacks. As shown in our numeric experiments, the combination of RLT features and MCSVM can detect several kinds of DDoS attacks effectively and indicate attack intensity precisely. The detection results are better than other detection measures. Because the RLT features include more attack information than the detection measures using single attack character, a better detection result is available.
In order to detect distributed denial of service (DDoS) attacks with support vector machine (SVM) measures, the feature vectors that can distinguish normal stream from attack stream are required. According to the characters of DDoS attacks, a group of relative value features are proposed. For indicating the existence and attack intensity of DDoS attack simultaneously, multi-class SVM (MCSVM) is introduced to detecting DDoS Attacks. As shown in our numeric experiments, the combination of RLT features and MCSVM can detect several kinds of DDoS attacks effectively and indicate attack intensity precisely. The detection results are better than other detection measures. Because the RLT features include more attack information than the detection measures using single attack character, a better detection result is available.
2008, 37(2): 278-281.
Abstract:
A new role base access control (RBAC) based authentication model which can resolve virtue organization (VO) authentication problem in large scale is proposed. The new model provides security to grid system in two aspects:firstly it makes user management and authentication more precisely, secondly, it reinforces authentication strategy at local level. According to the characters of VO in the Grid, we need a new solution to relieve burden of security, hence the optimized authentication architecture is built to achieve the better performance as well as reduction of total cost of ownership.
A new role base access control (RBAC) based authentication model which can resolve virtue organization (VO) authentication problem in large scale is proposed. The new model provides security to grid system in two aspects:firstly it makes user management and authentication more precisely, secondly, it reinforces authentication strategy at local level. According to the characters of VO in the Grid, we need a new solution to relieve burden of security, hence the optimized authentication architecture is built to achieve the better performance as well as reduction of total cost of ownership.
2008, 37(2): 282-284.
Abstract:
A certified e-mail protocol is about fair exchange of a message m for its receipt. Fairness is the most important property in exchange. We modify existing W-B signcryption scheme so that it can be used by certified e-mail protocols, and based on the modified scheme we propose a new certified e-mail protocol. The protocol makes use of an off-line and transparent trusted third party only in exceptional circumstances, and has lower computation overhead and better efficiency comparing related protocol.
A certified e-mail protocol is about fair exchange of a message m for its receipt. Fairness is the most important property in exchange. We modify existing W-B signcryption scheme so that it can be used by certified e-mail protocols, and based on the modified scheme we propose a new certified e-mail protocol. The protocol makes use of an off-line and transparent trusted third party only in exceptional circumstances, and has lower computation overhead and better efficiency comparing related protocol.
2008, 37(2): 285-288.
Abstract:
In order to construct a secure architecture which possesses enough strictness and practicability using mechanisms of password, log auditing, and authority, a model of security for information system including interface logic, business logic, and abnormal activity detection is proposed in this paper. The working flows and functions of main components of the model are described. At the same time the abnormal activities in an information system are analyzed, and the working methods of abnormal activities detector, a practical format of log data, and the protecting method of log file are introduced as well.
In order to construct a secure architecture which possesses enough strictness and practicability using mechanisms of password, log auditing, and authority, a model of security for information system including interface logic, business logic, and abnormal activity detection is proposed in this paper. The working flows and functions of main components of the model are described. At the same time the abnormal activities in an information system are analyzed, and the working methods of abnormal activities detector, a practical format of log data, and the protecting method of log file are introduced as well.
2008, 37(2): 289-292.
Abstract:
The self-assembled polyelectrolyte layers were used to modify the substrate surfaces for depositing polypyrrole films via in situ polymerization and self-assembly method. The properties of the films were characterized by ultraviolet-visible spectrophotometry (UV-Vis) and atomic force microscope (AFM). The PPy films gas sensors using the interdigitated electrodes were fabricated, and the sensing properties to toxic gase NH3 at room temperature were studied. The results showed that the sensor could detect NH3 of 0~141 ppm concentrations with a high sensitivity and good response. And the effects of depositing time on the sensitivities were investigated, which showed that the best sensitivity was obtained with 20 min depositing. The sensitivities to temperature from -30℃ to +60℃ and humidity from 5.9% R.H to 59.6% R.H of the sensors were tested at last.
The self-assembled polyelectrolyte layers were used to modify the substrate surfaces for depositing polypyrrole films via in situ polymerization and self-assembly method. The properties of the films were characterized by ultraviolet-visible spectrophotometry (UV-Vis) and atomic force microscope (AFM). The PPy films gas sensors using the interdigitated electrodes were fabricated, and the sensing properties to toxic gase NH3 at room temperature were studied. The results showed that the sensor could detect NH3 of 0~141 ppm concentrations with a high sensitivity and good response. And the effects of depositing time on the sensitivities were investigated, which showed that the best sensitivity was obtained with 20 min depositing. The sensitivities to temperature from -30℃ to +60℃ and humidity from 5.9% R.H to 59.6% R.H of the sensors were tested at last.
2008, 37(2): 293-296.
Abstract:
The surface of flaky metal magnetic powders was coated by silane coupling agent. The appearance, structure and phase constitute of powders before and after treatment were characterized by SEM and RA-IR. And the powders were randomly dispersed in paraffin at a weight ratio of 5:1 for microwave electromagnetic parameters test and comparison in the frequency range of 2~18 GHz. The results show that a high resistivity film is formed on the powders surface by chemical bonding, and the real and imaginary parts of complex permittivity of sample decrease 9 in average but corresponding complex permeability decreases slightly. The coatings with thicknesses of 1 mm give a microwave absorption of 8 dB with a band width of 8.2 GHz and microwave absorption of the coated flaky metal magnetic powders is improved.
The surface of flaky metal magnetic powders was coated by silane coupling agent. The appearance, structure and phase constitute of powders before and after treatment were characterized by SEM and RA-IR. And the powders were randomly dispersed in paraffin at a weight ratio of 5:1 for microwave electromagnetic parameters test and comparison in the frequency range of 2~18 GHz. The results show that a high resistivity film is formed on the powders surface by chemical bonding, and the real and imaginary parts of complex permittivity of sample decrease 9 in average but corresponding complex permeability decreases slightly. The coatings with thicknesses of 1 mm give a microwave absorption of 8 dB with a band width of 8.2 GHz and microwave absorption of the coated flaky metal magnetic powders is improved.
2008, 37(2): 297-300.
Abstract:
In the light of physics and basic equations of GaN-based high-electron mobility transistors (HEMT) with a field-plate, an analytic model of the surface electric field distribution and peak electric field are achieved. According to our model, when the field-plate length LFP and dielectric layer thickness tox are optimized, the peak electric field decreases to 22% compared with the condition with no field plate. With a well designed field plate applied, the maximum drain voltage can be improved from 50 V to 225 V while the peak electric field remaining unchanged. The results obtained from the model agree with those from the numerical simulation reported recently. The conclusions afford a good theoretically guidance to the design for GaN HEMT with field plate.
In the light of physics and basic equations of GaN-based high-electron mobility transistors (HEMT) with a field-plate, an analytic model of the surface electric field distribution and peak electric field are achieved. According to our model, when the field-plate length LFP and dielectric layer thickness tox are optimized, the peak electric field decreases to 22% compared with the condition with no field plate. With a well designed field plate applied, the maximum drain voltage can be improved from 50 V to 225 V while the peak electric field remaining unchanged. The results obtained from the model agree with those from the numerical simulation reported recently. The conclusions afford a good theoretically guidance to the design for GaN HEMT with field plate.
2008, 37(2): 301-304.
Abstract:
Four musical excerpts representing four different emotions of ‘happy, joy, sad, and fear’ were selected as stimuli by emotions scale. The electroencephalogram was recorded simultaneously and the alpha power was analyzed with factors of brain region, valence, and intensity of the musical emotions. The results showed that the alpha power was closely related to emotional valence and intensity. The difference between ‘joy and fear’, ‘happy and fear’, and ‘fear and sad’ was statistically significant. In the parieto-occipital region, the alpha power was significantly larger in calm emotion than in intense emotion within negative emotions; meanwhile within intense emotions the alpha power was significantly larger in positive emotion than in negative emotion.
Four musical excerpts representing four different emotions of ‘happy, joy, sad, and fear’ were selected as stimuli by emotions scale. The electroencephalogram was recorded simultaneously and the alpha power was analyzed with factors of brain region, valence, and intensity of the musical emotions. The results showed that the alpha power was closely related to emotional valence and intensity. The difference between ‘joy and fear’, ‘happy and fear’, and ‘fear and sad’ was statistically significant. In the parieto-occipital region, the alpha power was significantly larger in calm emotion than in intense emotion within negative emotions; meanwhile within intense emotions the alpha power was significantly larger in positive emotion than in negative emotion.
2008, 37(2): 305-308.
Abstract:
Based on modularization, this paper proposes the 4-layer model of GD102 motion controller's driver through research on its characteristics. The four layers are kernel layer, register layer, basic command layer, and application layer. This paper analyses the function and implementation method of each layer. The communications between layers are also referred to. The driver of the motion controller is developed by the tool of DriverWorks through analyzing the composition of the kernel mode driver and the processing of the IRP in Windows2000. Some key problems during processing of program development are discussed in this paper. The driver has been applied in an open numerical control system successfully.
Based on modularization, this paper proposes the 4-layer model of GD102 motion controller's driver through research on its characteristics. The four layers are kernel layer, register layer, basic command layer, and application layer. This paper analyses the function and implementation method of each layer. The communications between layers are also referred to. The driver of the motion controller is developed by the tool of DriverWorks through analyzing the composition of the kernel mode driver and the processing of the IRP in Windows2000. Some key problems during processing of program development are discussed in this paper. The driver has been applied in an open numerical control system successfully.
2008, 37(2): 309-312.
Abstract:
A high precision data acquisition system for penetrating fuse system is presented in this paper. This system is based on a MEMS array accelerator, which extends the measurable acceleration range to 105g. In order to meet the demand of high precision measurment, real-time response, and small volume, a 8 channels parallel data acquisition circuit and a 64 order digital FIR circuit are designed on a FPGA chip. This data acquisition system is also very convenient for maintenance and upgrade.
A high precision data acquisition system for penetrating fuse system is presented in this paper. This system is based on a MEMS array accelerator, which extends the measurable acceleration range to 105g. In order to meet the demand of high precision measurment, real-time response, and small volume, a 8 channels parallel data acquisition circuit and a 64 order digital FIR circuit are designed on a FPGA chip. This data acquisition system is also very convenient for maintenance and upgrade.
2008, 37(2): 313-316.
Abstract:
The method combining fuzzy with slide mode varying structure control is applied to the motor vehicle sensotronic brake control (SBC) system. The integration uncertain border value is estimated by fuzzy inference and the soft switch control is accomplished by tanh(x) function replacing sgn(x). The automobile SBC system based fuzzy-soft switch control is designed. The computer simulation is fulfilled for this system by using Matlab/Simulink software and the braking performance is tested on the test-bed. The results show that difference between the simulation results and the test is smaller. The buffeting is reduced and its braking is smooth.
The method combining fuzzy with slide mode varying structure control is applied to the motor vehicle sensotronic brake control (SBC) system. The integration uncertain border value is estimated by fuzzy inference and the soft switch control is accomplished by tanh(x) function replacing sgn(x). The automobile SBC system based fuzzy-soft switch control is designed. The computer simulation is fulfilled for this system by using Matlab/Simulink software and the braking performance is tested on the test-bed. The results show that difference between the simulation results and the test is smaller. The buffeting is reduced and its braking is smooth.
2008, 37(2): 317-320.
Abstract:
An algorithm based on the fuzzy set theory for the placement of chips on multi-chips modules (MCM) substrate is presented. In this algorithm, any chip in MCM is suffered three apparent forces:the repulsive force between chips, the attractive force between substrate boundaries and chip, and the attractive force between substrate and substrate center. The fuzzy relationships between the forces and the placement of chips are analyzed by the fuzzy inference rules. After defuzzification by the height method, the optimal placement of chips is obtained, in which the resulting apparent force is minimized. Finally, the validity of the algorithm is verified by FEM. Furthermore, the results from the fuzzy thermal placement algorithm are compared with those from the quadrisection placement method. It shows that the chip placement obtained by the fuzzy thermal placement algorithm is more reasonable and robust than that by the quadrisection placement method.
An algorithm based on the fuzzy set theory for the placement of chips on multi-chips modules (MCM) substrate is presented. In this algorithm, any chip in MCM is suffered three apparent forces:the repulsive force between chips, the attractive force between substrate boundaries and chip, and the attractive force between substrate and substrate center. The fuzzy relationships between the forces and the placement of chips are analyzed by the fuzzy inference rules. After defuzzification by the height method, the optimal placement of chips is obtained, in which the resulting apparent force is minimized. Finally, the validity of the algorithm is verified by FEM. Furthermore, the results from the fuzzy thermal placement algorithm are compared with those from the quadrisection placement method. It shows that the chip placement obtained by the fuzzy thermal placement algorithm is more reasonable and robust than that by the quadrisection placement method.
