In this paper, an adaptive resource allocation scheme of multi-service subcarrier adjusting and borrowing for multi-user OFDM-based systems is proposed. According to channel fading condition and quality of service of users, the scheme is used to maximize the system capacity and performance by adjusting and borrowing subcarrier among multi-service. The simulation results illustrate that the scheme proposed in this paper can improve performance OFDM-based systems.

In the paper, a jointly iterative maximum-likelihood channel estimation and decoding method is proposed for space-time trellis coding. By utilizing few of pilots, it can achieve better performance than the conventional non-iterative maximum-likelihood decoding. Simulation results show that the iterative method with 4 iterations has less than 1dB loss compared to the maximum-likelihood decoding with ideal channel state information. Finally, according to the simulation results, the method also gives a reasonable choice of both the steps of iterations and the amount of pilots.

A new time and frequency synchronization method based on frequency domain correlation for an Orthogonal Frequency Division Multiplexing (OFDM) system is presented. The time synchronization and carrier frequency offset estimation can be achieved simultaneously. The algorithms described here use one training sequence of just one symbol and the design of the symbol is presented. The carrier offset estimation can be got by the correlation result of time synchronization and the frequency synchronization algorithm can extend the frequency acquisition range to nearly the whole useful OFDM signal bandwidth. The efficacy of the synchronization algorithms is demonstrated experimentally.

An optimization design method for implementing regional coverage satellite system with common-track constellation is proposed. Based on a thorough investigation on the parametric characteristics of the common-track constellation, a coded notation which can describe this type of constellation entirely is proposed and the restricted equivalent relationship to the Walker’s δ constellation is given. The optimized method of common-track constellation for regional coverage is studied, and some optimal constellation schemes for China are presented. The simulation results show that the optimized common-track constellation can provide favorable coverage performance to China area with fewer satellites. The designed constellations are appropriate for the regional coverage satellite system of China.

Compared with the quasi-static rayleigh fading model, in MIMO (Multi-Input Multi-Output) systems, the practical channel is better for the spatial correlated fast Rician fading. Considering the transmit and receive diversity advantage in MIMO system and spatiotemporal correlation in transmitter and receiver arrays, based on the simple discussion about the MIMO system and channel model, this paper derive the close-form solution of the upper bound of the average pairwise error probability of the MIMO system under spatiotemporal correlated fast Rician fading by use of multivariate statistics, and the effect of the characteristic of the mobile channel on the system performance is discussed. Finally, the simulation results are shown.

Multiple-input and Multiple-output (MIMO) is a hot mobile communication technology in future. Single cell multiple user MIMO system is interference-limited by cochannel. The contribution of this paper is: game theory is used to analyse the MIMO multiuser system, and a distributed power control algorithm is given to optimize the system resource. The simulation results show that the noncooperative game model is reasonable. And the power control algorithm is found to give a significant performance improvement for the MIMO system when compared with the system without power control.

This paper investigates the bit error rate performance influence due to variation of the power of the pilots in pilot symbol assisted BPSK modulated general two-dimensional spread spectrum systems in Rayleigh fading propagation environments. Under the circumstance, that the system’s total transmitting power is fixed, the pilot to data power ratio is optimized analytically. Simulation results accord with theoretical conclusions, both of which illuminate that the optimum pilot to data power ratio is determined by the parameters of multipath fading channels such as SNR, Doppler frequency and multipath delay. The characteristic of low pass filter also affects the optimum pilot to data power ratio.

Combining the advantages of space-time block codes and frequency-shift keying, space-time frequency-shift keying (ST-FSK), which does not require any channel state information at the transmitter and the receiver, can adopt the noncoherent ML detector under the Rayleigh fading channels. The paper deduces the noncoherent ML decision metric at the receiver with the knowledge of relative delay, and for the different SNRs it discusses the performance of binary and quaternary ST-FSK systems in the presence of distinct relative delay. Both theoretical analysis and simulation results show that, (1) lower SNR lessens the relative delay sensitivity of ST-FSK systems, but the relative delay sensitivity limits the systems’ performance for higher SNR; (2) the sensitivity makes little difference between binary and quaternary ST-FSK systems.

Power control is one of the key technologies for CDMA cellular mobile systems. In this paper, a distributed fixed-step power control algorithm is presented for CDMA cellular mobile systems. The power control problem of time-varying systems is converted to the power control problem with fixed-channel gain under the assumption that the system channel gain is time-varying and bounded. Convergence of the algorithm proposed in this paper is proved. Some simulations are given to show the effecicency of the algorithm.

The runtime of conventional SVM-MUD is too long to satisfy the requirement of real-time application. A fast algorithm based on online training of SVM (FOSVC) for multiuser detection is proposed in the paper. The algorithm distinguishes new added samples and constructs the current training data set using KKT condition in order to reduce the size of training samples. As a result, the training speed is effectively increased. Simulation results illustrate that the algorithm has a faster training speed and a smaller number of support vectors preserving the same quality of separating hyperplane. The performance of the FOSVC detectors is pretty much the same thing as that of SVM detectors, and much better than that of MMSE detectors.

Dimension-reduced blind space-time channel estimation and signal detection algorithm for MultiCarrier CDMA (MC-CDMA) system in frequency selective Rayleigh fading channel are presented. A decorrelating filter is applied to the receiving data vectors. The dimension-reduced signal of each user without Multiuser Access Interference (MAI) is got. Blind channel estimation can be performed by the rank-one approximation of whitened dimension-reduced data matrix. Then, the whitened dimension-reduced data vector as a single user model is looked, the Iterative Least Squares (ILS) detection and Minimum Mean Square Error (MMSE) detection are researched. Simulation results show the effectiveness of the proposed algorithms.

An improvement of the micro/macro beam configuration used in HAPS (High Altitude Platform System) CDMA systems is proposed, in which the model employed for the optimization of the system is complex but more practical, especially in the improvement of the array pattern and the calculation of channel interferences. The configuration is expected to satisfy the requirement of CDMA systems on HAPS, and the relief of traffic burden in hot spot areas can be achieved by embedding micro-beams in the macro-beams at the hot spot locations. The optimization is realized by the adjustment of the micro-beam for different user distributions and different hot spot locations. The numerical results show that the hot spot problem can be relieved efficiently with the presented structure, and a higher and more stable system capacity is expectable despite the variation of the user distribution.

Carrier Interferometry (CI) codes may be introduced to Orthogonal Frequency Division Multiplexing (OFDM) systems to improve BER performance and to eliminate the Peak-to-Average Power Ratio (PAPR) problem. This paper demonstrates mathematically that CI/OFDM system is identical to existing Single Carrier transmission with Frequency Domain Equalization (SC/FDE).

This paper suggests two Steepest Decreasing Constant Modulus Algorithm (SDCMA) blind detection schemes for MultiCarrier Direct Sequence-Code Division Multiple Access (MC DS-CDMA) systems, one of which is the SDCMA blind equalization, and based on the former, the other of which is proposed, i.e., the blind joint equalization and multiuser detection SDCMA algorithm. The two SDCMA schemes and subspace-based Minimum Mean-Squared Error (MMSE) detection are compared in the paper. The simulation results show that Bit Error Rate (BER) performances of the two SDCMA schemes are both superior to that of the subspace-based scheme, and the joint SDCMA scheme, which takes advantage of renewing the equalization weight vector and the multiuser detector vector at the same time, greatly improves system performance and is the best of the three schemes.

A method for constructing Low-Density Convolutional (LDC) codes with degree distributions optimized for block Low-Density Parity-Check (LDPC) codes is presented. The encoding, decoding, and short cycles elimination methods are discussed in detail. Experimental results show that the LDC codes constructed with the optimized irregular degree distributions for block LDPC codes are superior to homogeneous (i.e., regular) LDC codes.

In order to resolve the problem of Internet communication anonymity, the paper constructs one-off public key using identity-based cryptography. In this system, user only needs TC(Trust Center) issuing the private key one time, and he can generate his different public keys when uses it. So it can ensure the user’s anonymity and the disconnection among the user’s actions. And TC can reveal the user’s identity to preventing the user committing when occasion requires.

To avoid dispute about who are the actual signers, Sun first proposed a nonrepudiable threshold proxy signature scheme with known signers. Hwang et al.(2000) showed that Sun’s scheme is insecure and made an improvement on Sun’s scheme. Presently, Tzeng, Tan, Yang found that Hwang, et al.’s scheme is vulnerable against the conspiracy. This paper used the method of through intercommunion between original signer group and proxy signer group to achieve secret share and distributed keys, designed a new multi-proxy multi-signature scheme. The new scheme fully meets unforgeability and nonrepudiation requirements.

A novel buffer management algorithm named DNS(Dynamic Neural Sharing) is suggested in this paper. This algorithm utilizes the Back Propagation learning Algorithm(BPA) to manage buffer appropriately, thus reduce the packet loss in self-similar teletraffic patterns. A conclusion is drawn through two emulations that the DNS addresses the trade off between packet loss and fairness issues better than those traditional algorithms such as CP(Complete Partitioning), CS(Complete Sharing) and SPS(State Partial Sharing).

Aiming at the analysis for the service performance of independent intelligent peripheral, this paper presents the performance model based on queueing network. With the analysis of the service features and the basic information flow of the CRBT (Color Ring Back Tone) service deployed on the independent intelligent peripheral, Some performance metrics are obtained through using the approximate Mean Value Analysis(MVA) algorithm. These metrics help to find the bottleneck of the system and improve the quality of service. Finally, OPNET is used to simulate the system, and verified the accuracy of this model.

The importance of multiuser detection for CDMA-based mobile Ad hoc network is addressed in this paper. Different from conventional scheme, each terminal of the Ad hoc network in this paper is equipped with an adaptive blind linear multiuser detector. Employing slotted-Aloha protocol in MAC layer, and following full-connected network model, the throughput of Ad hoc network is studied. Theoretic analysis and simulation results show that multiuser detection can remarkably improve throughput performance of Ad hoc network.

In this paper, a new method is proposed to suppress the cross-terms of Wigner-Ville Distribution (WVD), which is based on thresholding the superimposition of multiple spectrograms. First, the spectrograms with different time-frequency resolutions are superimposed and then the superimposition is thresholded to localize the auto-term support region of the WVD. Secondly, the WVD is multiplied by the indication function of the region. In this way, a new Time-Frequency Distribution (TFD) is obtained. Unlike the traditional kernel function methods to suppress cross terms, our method not only reduces the interfering cross-terms but also preserves the superb time-frequency concentration of the WVD. The experimental results show that the method is very effective for both the multicomponent signals consisted of the LFM’s and nonlinear frequency modulation chirp signals.

This paper studies the steady-state of a robust cascade constant modulus(CM) array in alpha-stable distribution noise environment. A new signal canceller is proposed to cancel the captured signal by the previous beamformer. The convergence behavior of the canceller weight vector is examined. The behaviors of signals and alpha-stable noise transmitting along the cascade CM array are investigated. Computer simulations are presented to support this theoretical analysis.

In this paper, a MIMO channel model in the presence of polarization diversity is presented, the spatial correlation between signals and the channel capacity is analyzed, and the effect of polarization angle between receiving antennas on the spatial correlation and the channel capacity is investigated. Simulation results show that MIMO wireless system using polarization diversity is of excellent fading characteristic，and channel capacity is increased effectively.

When bit errors occur during transmission and cannot be corrected by an error correction scheme, error concealment is needed to mask damaged image at receiver. In this paper, a spatio-temporal error concealment algorithm based on fuzzy classify and mesh warping method is presented. The algorithm include two steps: First , the error blocks which are in the situation of pure translation are reconstructed. If the complicated motion such as rotation and zoom in or out is detected , the internal texture of each block is warped by a mesh-based affine transform, in order to comply with nontranslation. Experimental results show that the PSNR has been improved 1.5dB than the BMA-MBW, and 3.5dB than the BMA.

In order to resolve the problem of recognition rate decrease in condition of unideal iris image and local noise，an iris feature extracting algorithm based on local zero-crossing detection is presented in this paper. This method extracts iris texture feature by using local relativity of zero-crossing operator and texture signal, then encodes iris texture to form iris feature template depend on coefficient sign, finally classifies different patterns using similarity. Simulation results show that stable feature of unideal iris image can be extracted and high recognition rate can be achieved using the algorithm.

Preview model Parameters Evaluation RANSAC algorithm (PERANSAC) is given in vanishing point detecting. A preview model parameters evaluation selection is added in the RANSAC algorithm. With guaranteeing the same confidence of the solution as RANSAC, a very large number of erroneous vanishing point obtained from contaminated samples are discarded in the preview evaluation selection. The time of evaluating the quality of the vanishing point is reduced. RANSAC efficiency is significantly improved. PERANSAC algorithm is evaluated on real-world images, a significant increase in speed is shown and the solutions are same as RANSAC.

It is inefficient to visually retrieve image on magnanimous remote sensing raster image data base by some GIS spatial query interface. An efficient spatial visual retrieval algorithm aimed at directly storage procedure of Relational Data Base Management System (RDBMS) is described and optimized on performance on many levels in this paper after the character of magnanimous remote sensing raster image database spatial visual retrieval is studied in depth. This algorithm is implemented in a real application environment of magnanimous remote sensing raster image data base based on the spatial polygon query, ellipse query and line through query. The results of experiment demonstrate that this algorithm is stable and adaptable.

An application program, SARSIMS, is developed for spaceborne SAR. SARSIMS can be used in designing system parameters, and SARSIMS also performs analysis of system parameters, echo generating, SAR image formation, and system simulation. The design of system parameters and swath selection is completed by interactive operation. Visualization is an important characteristic of SARSIMS. Because of visualization in design procedures, SARSIMS provides an efficient method and is capable of satisfying user requirements.

In this paper Genetic Algorithms(GA) are applied to antenna pattern synthesis according to ambiguity depressing in spaceborne SAR. The ambiguity of spaceborne SAR is regarded as the objective function, and the beamwidth and the side lobe level of the antenna pattern are regarded as the constraints. The simulation results show that the ambiguity is depressed while the beamwidth and the side lobe level are well controlled via this method, which is quite helpful to spaceborne SAR system designing.

The advantages of wavelet packet transform and Trellis-Coded Quantization (TCQ) are introduced and compression algorithm for SAR raw data based on wavelet packet transform and TCQ is given. Compression performance of the algorithm on simulated and real raw data analysis is presented and compared with other techniques by different quality parameters, which shows that the algorithm is suit for compression of SAR raw data.

Speckle reducing is an important step in Synthetic Aperture Radar (SAR) image processing, ordinary methods blur image edges while reducing speckle. A SAR image filter method based on structured neibourhood model with macroscopical edge information is proposed in this paper. First multi-scale edge detector is applied to achieve principal image edges, then structured neibourhood filter is modified and used. Structured neibourhood filter adopts a series of templates reflecting regional direction information to describe image detailed property, the macroscopical edge information is introduced to constrain the selection of templates while processing. Finally simulated annealing algorithm is used to get appropriate template, the MAP estimate of the object pixel intensity can be achieved. Experiment indicates this method reduces effectively speckle while preserving image edges.

A comprehensive research on digital terrestrial TV signal based on OFDM is conduct, especially the theoretics feasibility of non-cooperative illumination using OFDM signal is analysed. It is shown that the ambiguity function of OFDM signal has good performance and OFDM signal is good for non-cooperative illumination. The result of this paper provide a theoretic foundation for the farther research of this kind of radar system.

The Content Addressable Network (CAN) is a sort of P2P overlay network. CAN realizes the efficient mapping of the file information and its storage location by using Distributed Hash Table(DHT). CAN is scalable，fault-tolerant and completely self-organizing. In this paper an introduction to the basic architecture and the principle of CAN is given first. And then some methods of CAN’s load balancing are proposed: such as largest area based uniform partitioning, uniform distributing of the keys. Finally, these methods are proved that they are effective by simulation.

Firstly, this paper analyzes some questions of trust and the fuzziness of subjective trust, based on fuzzy set theory, the fuzziness of trust is described by membership function, and how to create the fuzzy trust model has been solved. Secondly, based on the graph theory, the network is modeled as an undirected graph , and the rule of trust evaluation is defined by the aid of local information interaction. Thirdly, the model of fuzzy autonomous trust establishment based on open network environment is proposed; trust establishment strategy, the mechanism and condition of establishing a fully trusted network are studied in this paper. Finally, the influence of network topology to autonomous trust establishment is discussed through simulation experiment, and the convergence rate of autonomous trust establishment based on the small-world model ( φ-model) is analyzed in this paper, which enlightens a new way for network management.

Content protection is the key issue to perform digital content transactions on the web. It is impractical for commercial multicast assuming that all group members know the group key in traditional multicast key management schemes. The proposed design for multicast content protection and payment system is based on the secure smartcard assumption under which both attackers and card holder are not able to obtain the private key and group key stored in the smartcard. Identity-based encryption scheme is introduced in the system to avoid using public key certificates. The system can guarantee the secrecy of content transmission with other features like simplicity for identification, content authentication, key management and anonymity for payments.

Based on RSA signature and (string) oblivious transfer, an oblivious transfer protocol is proposed which solved the access control problem for an oblivious transfer protocol. The protocol proposed has the property: the only receiver who has the signature issued by the central authority can open the message which he chose; the sender can not decide whether the receiver has the signature or not. That is the identity of the receiver can not be confirmed after the protocol. Under the Decisional Diffie-Hellman(DDH) assumption the proposed scheme has provable security. The proposed scheme employs the standard RSA signature and Elgamal encryption.

The effect of cross section dimension on propagation characteristics in trapezoid tunnel is analyzed using finite element method. By varying the dimension of top side, bottom side, height, the cutoff frequency for dominant mode and the mode next to dominant and bandwidth in trapezoid tunnel are studied respectively. It comes to a useful conclusion that the increasing of top side, bottom side, height decrease the cutoff frequency and longer bottom side or lower height result in larger bandwidth.

Evaporation duct is a kind of typical anomalous profile of atmospheric refractivity, it can partly trap electromagnetic waves, as a result, the propagation characteristics are changed, which may be applied in electronic equipments such as radar, communication and ECM, etc. The purpose of this article is to study on anomalous characteristics of electromagnetic waves in evaporation duct environment through simulation methods based on electromagnetic waves propagation parabolic numerical equation and split-step Fourier algorithm technology. The experimental data of radar abnormal detection in Dalian Sea Area in October of 2003 is analyzed as an example of application to validate the abnormal characteristics of the electromagnetic waves and the anomalous detection of radar influenced by evaporation ducts.

In this paper, the resonance of compact frequency selective surface arrays is studied in particular.These new resonant cells are greatly reduced in dimensions and very compact in structures，so it is possible to realize the lower frequency selective surface.Simulation and measurement are basically in agreement.

The random perturbation of technological parameters is always existent during manufacturing, which has a definite impact on transmission performance of transmission lines. Considering the impact the stochastic model for transmission lines is proposed, and Monte Carlo method based statistical analysis method for transient simulation is presented. During the analysis process the precise integration algorithm is used to solve the transient simulation of each transmission line sample, and Jarque-Bera test is made for the normality of the model’s output, finally the worst-case estimation is given. Experimental results demonstrate that the proposed stochastic model and the statistical analysis method can evaluate the transmission performance of transmission lines effectively, and have great significance for the control and optimization of transmission lines’ fabrication process.

In this paper, a new Low Noise Amplifier (LNA) with adaptive-biasing and variable gain is presented, in which charge pump is used to convert the RF output signal of LNA into a dc control signal, the amplitude of which should be proportional to the input RF magnitude. By using this signal to control bias and gain of LNA simultaneously, the linearity of LNA is greatly improved. In 5GHz frequency, bipolar transistors exhibit better frequency and noise performance, so in this paper, BiCMOS technology is used. The LNA exhibits a noise figure of no more than 3.0dB (in the high gain mode), about 13dBm IIP3 improvement and gain tuning range of more than 15dB.

An unconditionally stable low-dropout regulator and low quiescent current is presented. The Low DropOut ( LDO) based on a high precision CMOS current reference, which is comprised of subthreshold transistors and has small temperature coefficient, provides a low quiescent current of approximately 4μA. Furthermore, by utilizing the design method of active Miller frequency compensation, the proposed LDO’s stability is independent of the load or the Equivalent Series Resistance (ESR) of the off-chip capacitor. The chip design is based on 0.5m CMOS mixed-signal process of CSMC. The simulation and experimental results show that the line and load regulations are only 2mV and 14mV, respectively. The dropout voltage is only 170mV at 150mA output current when output voltage is 3.3V. The output noise is 150μVRMS when frequency range is from 22Hz to 80 kHz.

The recommendation G.728 depends on the Levinson-Durbin algorithm to update gain filter coefficients. In this topic, it is replaced by three different methods which are the weighted L-S recursive filter, the finite memory recursive filter and the BP neural network, respectively. Using these three gain filter the speech coding effect is all better than the G.728. The weighted L-S algorithm has the best result. Its average segment SNR is higher than the G.728 about 0.76dB. It is also used to evaluate the case that excitation vector is 16 and 20 samples respectively; the weighted L-S algorithm has similarly the best result.

Whitenoise is a stream cipher proposed by the BSB Utilities Inc. In August 2003, Wu Hongjun proposed a breaking algorithm for Whitenoise. In this paper, the authors make an in-depth analysis for Wu’s breaking algorithm, and prove that the basic hypotheses of Wu are wrong, and that Wu’s algorithm can not find the correct key of Whitenoise. Furthermore, Wu’s algorithm is improved and a method obtaining the secret integer and the secret prime numbers is given. A forecast attack to Whitenoise is proposed, with which one can obtain signal for each clock. Furthermore, a think to obtain all the equivalent secret factors is given.