Code Division Duplex (CDD) is a novel duplex technique for next generation mobile communication systems. It supports the transmission for uplink and downlink at the same frequency band and the same time interval. As the power levels of uplink and downlink are of potentially great difference, the signals over uplink and downlink channels may interfere with one another seriously. In order to solve this problem, this paper proposes a novel technique to suppress the interference between uplink and downlink. First, several kinds of interferences are analyzed, and then an interference cancellation scheme combined with distributed antennas technique is proposed for base station. The interferences between mobile stations can be mitigated by the presented time slot assignment strategy based on the location technique. Finally, numerical calculations and simulation results show the effectiveness of the proposed methods.

Iterative Tree Search (ITS) is an efficient M-algorithm based soft MIMO detection scheme. However, ITS often faces the problem that Log-Likelihood Ratio (LLR) values of some detected bits can not be evaluated. Although it can be somewhat solved by setting the LLR magnitude for these bits to a constant value—LLR clipping, the system performance would be degraded. To overcome this problem, this paper presents a new M-algorithm based soft detection scheme. The scheme recursively calculates the a posterior probabilities of partial symbol sequences at each stage of the tree, based on which the LLRs of those bits from the first stage to the current one are approximately computed，and then, by using M-algorithm, retains partial symbol sequences and extends them to the next stage. The scheme can ensure that the LLR of each bit can be calculated, and provide highly reliable LLRs. Considering that the LLRs of some bits may be evaluated several times, a reduced-complexity implementation method is given in the paper. In addition, the paper suggests a simple approach for calculating the a posterior probabilities of symbol sequences. Finally, simulation results show that the proposed algorithm can obtain better performance than ITS and achieve good performance-complexity trade-off.

Cooperation between Base Stations (BSs) and collaborative transmission between Mobile Terminals (MTs) are two promising techniques for the next generation wireless communications. This paper studies the per-cell achievable uplink sum-rate and minimum E_b/N₀ of hybrid cooperative method and the interplay between the two collaborations in MIMO channels under an linear cellular model. A computational method and closed-form expression of minimum E_b/N₀ for the achievable rate of DF combine with multi-cell processing in MIMO channels is derived. Moreover, the simulation results in MIMO fading channels are presented, and the results show that the macro-diversity gain from multi-cell decoding is independent with MTs collaboration but can be linear superposition, and hybrid collaboration significantly improve the system performance. However, high interference from adjacent cells weakens effect of MTs cooperation in hybrid collaboration system.

For improving the bandwidth efficiency, a sinusoidal modulated method based on Prolate Spheroidal Wave Functions(PSWF) is proposed. The basedband modulated orthogonal waveforms is designed based on PSWF, which is time-limited and band-limited approximately. The orthogonal waveforms’ spectrum is mixed or overlapped in frequency domain. The information is modulated by multi-plexing baseband modulation. The spectrum shifting is achieved by sine carrier modulation. By simulation and analysis, the system bandwidth efficiency can be fast closed to 2 Baud/Hz and the approximating speed is greater than that of OFDM system, the power efficiency is better as well. The modulation method is easily realizable.

A cross-layer TCP fairness optimization model in mobile WiMAX is proposed, under which a TCP protocol, cross-layer TCP, is designed. The rate information from link layer of the mobile nodes and the strategy of preallocation bandwidth for ACK packet at the base station are both used to improve the quality of service of the downlink nodes, which gives throughput fairness to the downlink nodes and the uplink nodes. Experiments show that cross-layer TCP protocol can improve the fairness of the downlink nodes under the same system throughtput.

This paper utilizes the Karush-Kuhn-Tucher condition of convex programming issue and proposes a minimizing power scheme with low feedback overhead for multiuser MIMO-OFDM systems based on trellis coded modulation. Firstly, the scheme designs the codebook of rate and power and equivalent channel quantization threshold. Secondly, the subcarrier is allocated according to current channel state information and the equivalent channel gain is quantized. Finally, the base station broadcasts the result of resource allocation to users. The simulation results prove that comparing to other schemes the proposed scheme not only saves efficiently energy but also has advantage of low feedback overhead.

In the presence of heterogeneous traffic flows generated by services with different QoS requirements in Low-Earth-Orbit (LEO) satellite networks, a framework of Call Admission Control (CAC) and handover management scheme is proposed based on Optimal Multi-Threshold Channel Reservation (OMTCR) policy as well as its corresponding theoretic analysis approaches to evaluate the connection-level QoS metrics. To determine the optimal threshold parameters vector of OMTCR under given system parameters and input traffic conditions, the revenue concept in economics is referenced to formulate unconstrained and QoS-constrained system revenue objective optimization models. Results are presented to demonstrate the better performance of the proposed OMTCR than conventional Completely Sharing (CS) and Guard Channel (GC) policies under heterogeneous traffic conditions with different user QoS requirements and system revenue objectives.

A performance analytic model for underwater acoustic networks is presented in this paper. This model is established by the characteristic of underwater channel propagation and networking. Numerical simulation results indicate that the bandwidth efficiency of peer-to-peer network and centralized network both are relative with network scale, the workload of node, interval between nodes and transmitted power. The appropriated networking and protocol design can improve the communication performance of underwater acoustic networks, achieve optimum nodes’ interval for bandwidth efficiency. Research results in this paper can be use to guide application for underwater acoustic networks.

A joint source-channel decoding approach is developed to improve the reliability of image transmissions. The source coders used is the discrete wavelet transform coding, and channel coders used is the RCPC (Rate-Compatible Punctured Convolutional) coding. At the receiver, after transmitted through noise channel, a modified APRI-SOVA (a Priori Soft-Output Viterbi Algorithm) is employed which using not only soft output of the channel but reliability of the current bit providing by source decoder. The simulation results show that the approach may be better to exploit the correlation remain in the source data and use it at the receiver side in order to achieve a more reliable decoding.

JPEG2000 is a new still image compression standard based on wavelet transform. Compared with previous compression standards, it has a lot of advantages. However, in JPEG2000 the image distortion evaluation criteria is MSE, and MSE can not correlate very well with subjective ratings. So compression performance of JPEG2000 is affected greatly. In this paper, a still image compression algorithm SJPEG2000 that uses SSIM (Structural SIMilarity) as the distortion evaluation criteria is proposed under the framework of JPEG2000 standard. In order to let the compressed images retain more structural information, the algorithm intercept stream according to the contribution of the image structural information. Experimental results show that the images compressed by this algorithm retain much more structural information than original JPEG2000 and the corresponding SSIM value is also improved.

A knapsack-type public key cryptosystem is proposed. The proposed knapsack cryptosystem has the following advantages. The encryption and decryption only need addition and modular minus operations, so the encryption and decryption speed is high; The cryptosystem is constructed based on random knapsacks but not easy-to-solve knapsack problems; It is proven that if the secret key is not possessed by the attacker, the proposed cryptosystem can withstand the attacks launched by directly solving the underlying knapsack problem, including low-density attack and simultaneous Diophantine approximation attack; It is proven that the attacker can recover the secret keys if and only if he can factor a large integer. Analysis shows that the proposal is an efficient and secure public key encryption algorithm.

Grid portal is playing an important role in grid computing area. However, with the large-scale diverse resource need to be dispatched and coordinated, the portal shows its insufficient ability to deal with this complex situation and can not bear the overload of long-time transaction querying. What is worse, the users can not get their desired or expected resources. To solve these problems, grid portal recommendation architecture is presented. It consists of collaborative filter interaction layer, action layer and user render layer. In addition, a 2-way combo collaborative filter algorithm is put forward, and then the algorithm comparison is shown. Finally the experiment results improve that this architecture can be used to obtain the expected portal recommendation function and guarantee quality of personalized recommendation.

In applications like event detection, a Wireless Sensor Network (WSN) may be required to satisfy various detection latencies. In this paper, the lower bound of average detection latency is first analyzed for point coverage in a WSN. Then a polynomial distributed node sensing scheduling algorithm, which can adaptively adjust the sensing duty of sensor nodes and achieve the minimal detecting latency, is designed according to sensing tasks with various delay requirements. Furthermore, a Low-complexity Distributed Sensing Scheduling (LDSS) algorithm, which can apply to the area monitored by randomly deployed sensors is designed. Simulation results show that LDSS can obtain a lower average detecting latency than existing algorithm with acceptable overhead.

To eliminate the affect of the distribution of deployed sensor nodes on the coverage of effective communication signals in deployed areas for wireless sensor networks, an algorithm of Distributed Deployment of Coverage Probability (DDCP) is proposed based on the effective communication coverage in this paper. Assuring the deployed precision, DDCP is used to not only consider the environmental influence for uncertainties of the deployed positions of sensor nodes and communication signal attenuation, but also create the model of signal coverage to attain the optimal deployed locations and the number of sensor nodes. These ameliorate communication coverage, improve the effective of the deployment and save the resources through probability optimization. Through the simulations of different locating deployed strategies, relative data proves the advantage and correctness of DDCP.

Mobile Ad-hoc Networks (MANETs) have their fundamental characteristics, such as open medium, dynamic topology, distributed cooperation, and constrained capability. Due to the anonymous and self-organization nature of mobile nodes in the network, intermediate nodes on a communication path are expected to forward packets of other nodes so that nodes can communicate beyond their wireless transmission range. In this paper, a trusted routing selection algorithm based on multi-objectives in frequency-domain for MANETs is proposed. It is distinctly different with most of routing algorithms that select routing based on a single-objective in the time-domain. The proposed algorithm tries to analyze the secure and trusted routing based on probability theory to reduce the computation complex with the mutual transformation of probability functions between time-domain and frequency-domain. It solves the problem of finding secure and trusted routing for MANETs in the case of the lack of physical security, untrustworthy scenario and low trust levels among nodes in MANETs and malicious nodes colluding with one another to disrupt the network operation. Extensive analysis is carried out to evaluate the design of the algorithm.

In high-speed network, identifying heavy hitters precisely in time serves as great significance for both network security and network management. In order to circumvent the deficiency of the limitted computing and storage abilities in traditional traffic measurement, a novel mechanism called identifying heavy hitters based on Multi-Dimensional Counting Bloom Filter(MDCBF) is proposed. Extending the standard structure of Counting Bloom Filter(CBF) to multi-dimensional one, the mechanism can not only represent, query and count traffic flows, but also sustain real time multi-granularity measurement. Based on Apriori principle, it can realize the identification of heavy hitters through implementing renormalization of MDCBF. Experiments are conducted based on the data either randomly produced by computer or sampled from the real network trace. Results demonstrate that the proposed mechanism can achieve finer space saving without sacrificing accuracy.

Uncertain time-delay for transmitted information is often induced from local sensors to fusion node across wireless sensor networks with network constraints, and it easily results in the out-of-sequence phenomenon. Accordingly, the conventional information fusion methods are faced with difficulties and challenges. In this paper, the optimal distributed fusion for the “Out-Of-Sequence” Estimate (OOSE) information systems is studied for multisensor systems with synchronous samples and arbitrary random delay. As a result, a novel universal optimal OOSEs fusion algorithm is presented. Compared to the current “Out-Of-Sequence” Measurement (OOSM) fusion methods under the centralized estimate frame, the proposed OOSEs fusion algorithm has the outstanding advantages on fusion precision, algorithm complexity and computational efficiency etc... Brief analysis and simulations both show its validity and superiority.

Track association of multitarget is one of the key and difficult issue in the space-based optical tracking system. Traditional distributed track association methods rely on three dimension information of the tracks, are no longer applicable to the two dimensional track association issue. Therefore, the hinge angle difference is treated as statistic, a track statistical testing model is constructed, and a global optimization track association algorithm is proposed. Finally, a Monte Carlo simulation of dense targets is done, results show that the proposed algorithm has favorable performance, and can accomplish the passive multisensor multitarget track association task efficiently in dense targets scenario.

The scale self-adaptive mechanism is one of the promising research directions in the object tracking issue based on mean-shift. A typical method is to adopt Lindeberg’s scale-space theory to obtain the scale information of the target. However, the 2-D scale vector is reduced to 1-D in the existing algorithm. So it is not precise enough to portray the changing state of the object scale under affine transformation, which greatly limits the scope of application of the method. Hence, the 1-D filter in the scale dimension is extended to 2-D in this paper. Correspondingly, the 4-D scale space is constructed, then the problem is mapped into two interleaved mean-shift procedure in the spatial and scale dimension through scale space. The modified algorithm achieves the effective object tracking in spatial position and scale direction simultaneously, which enhances the self adaptability when the target scale is changing, and expands the scope of application of the algorithm.

There are two primary ways to process multi-target tracking problem. One is data association method, whose deputies are PDA and JPDA. The other is direct method without the data association, whose deputies are random sets theory and GM-PHD. Two representational algorithms are chosen from aforementioned two kinds of methods respectively, that is, JPDA and GM-PHD. Firstly, general analytical forms to evaluate calculation complexity of each algorithm are formulated by analyzing and totaling their major operation steps. Secondly, the calculation complexity of two algorithms is compared through three cases respectively, which are divided on the basis of associated complexity between states and the measurements. Finally, one example, including tracking effect and the running time, is utilized to illustrate the analytical forms of evaluating calculation complexity proposed in this paper.

Based on energy-aware mapping algorithm for NoC regular architectures, a new method, MM-Map is proposed, which can automatically map a circuit of real–time digital signal processing system onto the NoC platform with the minimum critical delay for the system in this paper. The MM-Map platform uses generic algorithm to optimize the delay-aware objective which can satisfy the specified constrains such as limitation of processing units and link bandwidth of NoC. The simulation results show that the new method can reduce the hardware cost and achieve an approximate global optimum with a simple procedure and good convergence.

Traditional multibeam bathymetry system based on FT beamforming method can not achieve high accuracy seafloor bathymetry estimation of outer beams area, while interferometric multibeam bathymetry system based on phase detection method can estimate the bathymetry information in such area with high accuracy and resolution ability. To improve the performances of traditional multibeam bathymetry system, MSB-RMU algorithm is proposed, combining the advantages of FT beamforming and phase detection methods, which has high spatial resolution ability and achieves high accuracy bathymetry estimation of both central beams area and outer beams area. The processing results of experiment data prove the efficiency, practicality and superiority of the new algorithm, which ensures the first domestic multibeam bathymetry system to achieve 6 times coverage of the water depth.

A new algorithm based on Split-Symbol Moments Estimator (SSME) is provided in this paper to estimate blindly the chip rate of Direct Sequence Spread Spectrum (DS/SS) signal. The effectiveness of this algorithm is verified by analyzing the relationship between the symbol rate and chip rate, and the relationship between chip rate and Signal-to-Noise Ratio (SNR) in Additive White Gaussian Noise (AWGN). Computer simulation shows that this algorithm can estimate the chip rate successfully in low SNR and can enhance the accuracy of the chip rate estimation by increasing the length of the processed sampling data.

In the processing of Synthetic Aperture Radar (SAR) image speckle noise reduction, maintaining the edges and textures of image are very important. This paper proposes a fractional-order multi-scale Partial Differential Equation (PDE) model by modeling the image with fractional-order derivative and negative Sobolev space, and then gives the adaptive selection method for the model parameters and the region-scale adaptive algorithm for SAR image denoising. Numerical experiments show that the new method can achieve better results in removing the noise, restraining the staircase effect and preserving edges and textures.

A parameter estimation method by imaging with the Keystone-Wigner Transform (KWT) for fast moving target is proposed. The radial velocity of fast moving target can cause the range walk and azimuth Doppler shift, so the accurate Doppler center can not be obtained only with interferometric phase, but with the range walk ratio of the target the Doppler ambiguity can then be resolved and the accurate Doppler center can be acquired. The along-track velocity of the fast moving target will result in the changing of the Doppler rate, and makes the moving target defocused in conventional SAR image. The Doppler rate can be attained with KWT after the range walk is removed, then the radial velocity can be obtained with the interferometric phase and following the along-track velocity of the target can be attained. The moving target indication is processed in the Dechirped domain, and in the case of acquiring the along-track velocity of the target both the PRF ambiguity and the phase ambiguity are taken into account, so the relocation and the velocity estimation of the fast moving target can be achieved. The processing result of measured data illustrates the effectiveness of the method.

High resolution wide swath SAR requires high power aperture product under the limit of small antenna. It also needs generating and receiving wideband signal. According to these problems, a space-time-frequency coding method based on crossed receiving is presented in this paper. This method increases power by transmitting multiple sub-bands and multiple waveforms and overcomes the limits of power aperture product. It synthesizes wideband signal by the method of crossed receiving without complicated imaging algorithm. Finally simulations show its feasibility and validity.

A 3-D inverse synthetic aperture radar imaging method based on stepped-frequency waveforms for high speed spinning targets is proposed in this paper, aiming at the signal with narrow-bandwidth. Assuming the motion compensation is completed, single-range matching filtering is performed in certain sub-pulse firstly to obtain ISAR image. Then parameters of scatters are estimated using CLEAN technique. ISAR images are obtained in different sub-pulse and different range bin. At last range synthetic profile processing is performed to get high resolution in range and the 3-D image is obtained. This method can void the Doppler influence of spinning targets on range synthetic and improve the resolution effectively. Simulations of multiple scatters validate the feasibility and superiority of the approach.

For the urgent need of the waveform for Multiple-transit and Multiple-receive SAR, three kinds of waveforms are researched and compared, which are the representative waveforms for the Multiple-transit and Multiple-receive SAR, and evaluate the practicality by simulating the distributing target. On this base, the waveform separation and energy separation rules for echoes of Multiple-transit and Multiple-receive SAR are proposed. The phase compensates and channel responses for the Double-transit and Multiple-receive SAR which uses space-time coding as waveform are also given. It is proved that this system has predominance in improving SNR than Single-transit and Single-receive SAR.

Clock jitter is one of the most importation factors that affects the Signal-to-Noise Rate(SNR). Based on Gaussian random process model and continuous-time system in time domain ,this paper analyzes the effect on baseband and intermediate frequency sampling due to clock jitter. Taking into account the quantization noise, an approximate formula of the relationship between SNR and other factors is obtained in time domain. The simulation results show that the formula also be applicable to calculate the SNR in discrete-time system. The paper also discusses the influence of clock jitter on the pulse compression of the Synthetic Aperture Radar(SAR) signal. The window function is used to weight the signal in order to suppress the side lobe in pulse compression process. Finally, several methods to reduce the clock jitter are introduced.

In this paper, the multi-static ISAR three-dimension turntable model and imaging algorithm are proposed. Furthermore, the multi-static ISAR three-dimension turntable imaging constraints are analyzed. Based on the range projection equations and azimuth doppler equations deduced by multi-static ISAR three-dimension turntable model, the positions and movement parameters of target scattering points are obtained. The multi-static ISAR three-dimension turntable model and imaging method are verified with simulation experiments.

One of the tough task that airborne bistatic radar faced is the extensive existing non-stationary of bistatic clutter which will degrades the performance of STAP remarkably. A novel bistatic modified technique named Improved joint Space-Time INterpolation Technique (ImSTINT) is introduced in this paper. Compared with traditional space-time interpolation techniques, ImSTINT minimizes the degrees of freedom of subspace clutter after transformation to the utter most, and thus eliminates the influence of non-stationary of clutter on clutter suppression in airborne bistatic radar system. Furthermore, ImSTINT has faster convergence rate and better suppression performance against mainlobe clutter.

A new algorithm of IF noise simulation for a multichannel direct spread-spectrum system is proposed. The influences between each channel of spread-spectrum signals are treated as noise in this algorithm. A new algorithm of proportional divisor that is suitable for the signals mixture of a multichannel spread-spectrum system is put forward based on this noise simulation algorithm. This algorithm is applied successfully to an IF signal simulator of one multichannel direct spread-spectrum system. The experimental results show that the precision of IF signal generated by this algorithm is much better than it generated in traditional way.

In passive millimeter wave image restoration, L-R algorithm is a simple and effective nonlinear method. However, when the noise can not be neglected, it is difficult for L-R algorithm to get good restoration. As a novel signal processing method, adaptive sparse representation has a merit of representing signal flexibly and can de-noise effectively when maintaining features of targets. A novel L-R algorithm is proposed based on adaptive sparse representation. It first de-noises by employing sparse signal representation, and then restores images by using L-R algorithm. The modified algorithm reduces the influence of noise on L-R algorithm effectively by using de-noise algorithm based on adaptive sparse representation. The imaging results of experiment data show that the modified algorithm proposed in the paper improves the performance of L-R algorithm, and it can be used in image restoration when the signal to noise ratio is low.

In the field of image segmentation, the image segmentation approach based on discrete level set can not accurately segment an image with low SNR value, and the speed of image segmentation is lower. In order to solve these problems, an alternative approach is proposed based on continuous level-set. The level-set function is modeled as a continuous parametric function using the line combination of two-dimension Lagrange basis. The difference equation is derived by minimizing the energy formulation for image segmentation. As a consequence, the minimization of the energy formulation is directly obtained in term of the Lagrange coefficient. The fast segmentation of image with low SNR value is implemented by the numerical solution of the coefficient difference equation that is solved by simple finite-difference methods. Experimental results demonstrate that the proposed approach can gain better perfect effect.

The linear theory together with the self-consistent nonlinear theory are applied to systematically study the stability of a Ka-band TE₁₁ mode ultra-high gain gyrotron Traveling-Wave Amplifier (gyro-TWA). The analysis reveals the differences between the forward-wave absolute instability and the backward-wave oscillation, as well as the suppressing effect to these self-excited oscillations by using distributed loss technique. Using properly down-tapering the magnetic in the nonlinear stage to improve the stability of the system is proposed for the first time. Based on the analysis, a Ka-band TE₁₁ mode gyro-TWA with ultra-high gain ability is designed, which adopts an electron beam with voltage of 100 kV, current of 7 A, velocity spread of 5%, and is capable of obtaining the -1 dB saturated bandwidth about 5 GHz and the highest gain about 80dB.

The field in helix TWT (Traveling Wave Tube) is studied with numerical analysis. By Numerical field analysis, neglected in the theory’s, the phenomenon is that, the master and slave face setting decides the wave propagation direction, and the helix rotation decides the field’s rotation. Also, the cross-section distribution infection in helix with different rods and vanes outsides of helix are also studied. The field cross-section distribution changes very small, almost with the Bessel function. But the impedance changes much because of the electromagnetic energy re-distribution in rods or vanes. On the other hand, accurate spatial harmonious impedance can be obtained by the spatial harmonious field numerical analysis, especially the mostly used spatial harmonious wave, the 0 and -1 spatial harmonious wave. Above this, the accuracy of the forward and backward beam-wave interaction can be improved.

In this paper, 3D second-order finite element method for electron optic system is presented. And it is implemented in Electron Optics Simulator (EOS). The results are compared between first-order finite element method and second-order finite element method. Second-order finite element method has better convergence and faster convergence rate.

A large amount of computation of particle filter limits its engineering application. According to this problem, Quasi-Monte Carlo (QMC) sampling is used to replace Monte Carlo (MC) sampling, reducing the required computation. Quasi-Monte-Carlo Gaussian Particle Filter (QMC-GPF) algorithm parallel architecture is proposed. Based on the parallel architecture, this paper lays emphasis on the implementation of the algorithm on FPGA in detail. Base 2 is used to generate Faure sequences, thus instead of multiplication and mod only bitwise XOR, which is easily to realize on FPGA, is needed to generate the sequences. Look-up tables are used in calculating the complex functions such as exponential function, which makes full use of the large number of Block RAM of FPGA. The parallel structure is designed to compute the elements of the Cholesky decomposition matrix. Infrared imaging dim small target tracking is realized on FPGA and the results show the efficiency and real time of the design.

Motion compensation is essential for wide-beam High Resolution Airborne Glacier Penetrating Radar (HRAGPR). This paper proposes a motion compensation algorithm for wide-beam airborne nadir-looking glacier penetrating radar. Based on frequency division, the wide-beam motion error is transformed to narrow beam error. The algorithm takes blocks along azimuth dimension in frequency and applies angle-variant narrow beam motion compensation in time domain. After that, all blocks are coherently added to compose the compensated data. The algorithm carries out the compensation in time domain, so it is applicable to any motion error form. This paper analyzes the spatial-variant properties of HRAGPR motion error, the principle and processing steps of the algorithm are also presented. Simulation of point target of HRAGPR with low frequency and high frequency motion error validate the effectiveness of the proposed algorithm.

This paper gives the bandwidth under different signal to noise ratios by precisely analyzing the atan phase detector, proved the result by simulation. It is concluded that the bandwidth of the loop under very low signal to noise ratio is triplicate of the bandwidth in high signal to noise ratio, which will make the error caused by short-term stability of the oscillator and the acceleration of Doppler. The signal to noise ratio decreases 10 dB, the thermal phase noise will increase 20 dB. Finally, for the purpose of steady tracking, the threshold of signal to noise ratio and the loop filter’s coefficients are given. The results of this article can be used to guide the design of the satellite navigation receiver.

A new prescaler based on new Source Coupled Logic(SCL) latch is proposed in this paper, supplying Local Oscillator (LO) for receivers. Compared to traditional static SCL latch, a clock-controlling transistor is added to reduce the time constant at sensing time, and as a result, the maximum operating frequency increases and the operating range is enlarged. A simple but to some extent accurate small signal model for this new architecture is developed, and the advantages of new design are described in detail. This prescaler’s maximum operating frequency can reach to 6.9 GHz when its current is only 1.2 mA. The prescaler is manufactured in 0.18 μm CMOS process, and it has been successfully applied to GPS receivers.

In order to solve the intra-class blind recognition problem of IFFT-based multi-carrier modulation signals under the conditions of multi-path fading background, a blind identification algorithm of multi-carrier modulation signal is proposed based on singular value decomposition of structural matrix. Without any prior knowledge of data information as well as the type and length of spreading code, this algorithm can determine the type of multi-carrier modulation signal accurately according to the number of larger non-zero singular value of structural matrix in accordance with simple criteria, and have achieved good results. It does not have to design the complexity classifier in the traditional recognition algorithm after feature extraction, and simplifies the recognition process. Both the theoretical analysis and simulation results verifie the correctness and effectiveness of the algorithm, therefore ,the algorithm has certain theoretical and practical reference value.

An out loop power control algorithm based on continuous fuzzy control is presented in this paper. The variation value of the block error rate is processed by fuzzy control, and the output value which is obtained by fuzzy control rules and defuzzification is adopted as the step size to adjust the SIR target of the inner loop power control. The algorithm can acquire the best adjusting step accurately, thus it avoids the overshoot phenomenon of the existing outer power control methods. In addition, with the variation of the network and the wireless environment, the average BLER can fast converge at the required BLER target value which meets the quality of the services. The experimental results validate the excellent properties of the algorithm.

This paper presents a strongly secure certificateless signature scheme without pairings, which is existentially unforgeable against adaptive chosen message and ID attacks. The complete security proof is given under random oracle model, assuming that the discrete logarithm problem is intractable. The scheme is more computationally efficient than others built from pairings，as there is no heavily cost pairing operation in this scheme. In addition, a security analysis is presented for Wang H G’s pairing-free certificateless public key signature, and the results show that the scheme is insecure with a concrete attack method.

The access delay of Enhanced Distributed Coordination Function (EDCF) in WLAN under error-prone channel is studied. Utilizing the Markov chain model, a model for analyzing the access delay of different priority traffic under error-prone channel is proposed, and the accuracy of the model is verified with simulation. Simulation results show that IEEE 802.11 EDCF meets the Quality of Service (QoS) of different applications by setting different accessing parameters.

Challenges of designing reliable and efficient Medium Access Control (MAC) protocols are posed for underwater acoustic sensor networks, because of hostile seawater channel condition. For hexagonal grid topology networks, this paper presents G-TDMA protocol, which improves channel utility with spatial reuse of time slots and reduces synchronic overhead by synchronizing nodes in the process of packet transmissions. In addition, G-TDMA employs guard time to avoid packet collisions due to long propagation delay and channel fluctuations. Simulation tests show that the protocol improves network performances in underwater environment.

Signcryption is a cryptographic primitive that simultaneously performs the functions of both digital signature and encryption in a way that is more efficient than signing and encrypting separately. Multi-signcryption is an extension of signcryption scheme for multi-signers performing together the signcryption operation on the same message. Two signcryption schemes, including signcryption proposed by Li et al.(2006), and multi-signcryption scheme by Zhang et al.(2008), are proved not to resist on chosen-plaintext attack and chosen-identity attack under the CPA adversary. Furthermore, the improved signcryption and multi-signcryption schemes are put forward that providing security properties including CPA, CCA2, and public verifiability, which deploy the message hidden method to resist on the chosen-plaintext attack, and multiple signer members authentication to protect the multi-signers’ ciphertexts not be interpolated.