Advanced Materials Research Vols. 945-949

Abstract: Keystroke rhythm identification, which extracts biometric characteristics through keyboards without additional expensive devices, is a kind of biometric identification technology. The paper proposes a dynamic identity authentication model based on the improved keystroke rhythm algorithm in Rick Joyce model and implement this model in a mobile phone system. The experimental results show that comparing with the original model, the false alarm rate of the improved model decreases a lot in the mobile phone system, and its growth of imposter pass rate is slower than the Rick Joyce models. The improved model is more suitable for small memory systems, and it has better performance in security and dynamic adaptation. This improved model has good application value.

Abstract: Rate compatible modulation (RCM) is a promising technology to smooth rate adaption of physical layer in wireless network, and do not request the accurate channel estimation. Since RCM demodulation adopt probability convolution operator in belief propagation algorithm, it greatly bring big computing complexity. This paper proposes fast demodulation algorithm for RCM by using log-map principle. First, we propose a new demodulation algorithm by a novel approach to convert arithmetic domain to logarithm domain. Then, we design a parallel manner that to find multivariable computation in Log-MAP algorithm for hard implementation. Finally, we evaluate fast demodulation algorithm by two evaluation metrics BER and goodput, respectively. Our analysis show that the demodulation complexity can be reduced about 90%. While experimental results show that the fast demodulation algorithm performance only has a marginal loss.

Abstract: A precoding algorithm based on the truncated polynomial expansion is proposed for massive multiple-input multiple-output system, Using the random matrix theory, the optimal precoding weights coefficient is derived for tradeoff between system throughput and precoding complexity. Finally, under different channel conditions, the simulation results show that the average achievable rate will increase infinitely approaches the regularized zero forcing precoding and has better performance than TPE scheme without optimization..

Abstract: The paper proposes an improved genetic algorithm which is applied to the problem of GPS signal acquisition.The improved genetic algorithm uses the small section method of the initial population, dynamic search range of parameter, and the adaptive crossover probability and mutation probability to search GPS signal parameters. Simulations and experiment results show that the improved genetic algorithm can search the signal parameters rapidly and precisely. The GPS signal acquisition performance is improved.

Abstract: Traditional kinematic baseline resolution usually needs one or more fixed reference station. In some special application, the reference stations could be in motion. In order to determine kinematic baselines in scenarios of moving reference stations and rovers, a KINRTK model is studied by using a baseline length constraint with three antenna configuration. The baseline and integer resolution method are given. A KINRTK experiment is done, using the data collected on ship enroute, the resolved baselines lengths are compared with the predetermined baselines, which show that the KINREK models baseline length errors are within 5cm, which can verify the effectiveness and accuracy of the model proposed and ambiguity resolution method.

Abstract: A type of BUCK/BOOST bi-directional DC-DC topology for high power occasions was presented based on the main circuit topology shortcomings of conventional BUCK/BOOST bidirectional DC-DC converter by increasing the inductance, capacitance, diode auxiliary circuits, the work process of the main circuit BUCK BOOST in the simulation state was analyzed. Select multiple sets of parameters on simulation, observe the waveform ON and OFF of main power device to determine the appropriate auxiliary circuit parameter set. The results show that: The topology suppresses large current peak of the main power device and improve the reliability.

Abstract: Current source converter is a variable structure system due to its switching nature, so that it can easily cause the output current waveform distortion and can not be accurately track the reference current. To solve the above problems, this paper proposes a new variable structure control strategy with fan-shaped sliding domain in the current source converter control system. In the control strategy, the paper deduces the switching surface and switching control law of SMVSC, and calculates the sliding existence domain based on the mathematical model of current source converter. Finally, the simulation results show that the control scheme can make current source converter have better output current waveform, fast tracking the reference current, and strong anti-interference ability. Therefore, the control scheme is correct, effective and feasible.

Abstract: This paper analyzes the basic theory of the microstrip narrow-band filter design and accomplishes the design of narrow band-pass filter whose center frequency is on L-band with the help of the Agilent ADS simulation software. The filter adopts Chebyshev’s prototype structure and consists of coupled microstrip line. Its fluctuation is less than 0.5dB and attenuation is less than 1.5dB between 1.9GHZ and 2.1GHZ .Its port Reflection coefficient less than-15dB and attenuation is greater than 20dB at 1.72GHZ and 2.3GHZ. Layout simulation meets the requirement of filter design.

Abstract: Electric energy data acquisition system is the necessary requirement to construct "Marketing" infrastructure and smart grid, change the development mode of the company and grid. To solve the problems of the 230MHz wireless private network of the electric energy data acquisition system, such as low communication rate, fewer access points, low acquisition success rate and poor real-time performance, a new-type data transmission scheme of electric energy data acquisition system is proposed. The key technologies, such as carrier aggregation, software radio, multi-antenna, networking, OFDM, safeguard and other technologies, are discussed. The new-type communication technology based on SGWM in the electric energy data acquisition system is elaborated. The experimental results show that the field application effect of the new-type 230MHz communication key technology based on SGWM in the electric energy data acquisition system is improve the interactivity, real-time instantaneity, reliability of smart grid.. Thus it provides technical support for the popularization of the information bidirectional interaction and construction of smart grid.

Abstract: Modeling and simulation of MAC layer protocols for wireless sensor networks was realized, including WOO-MAC, IEEE802.11 and S-MAC base on OPNET Modeler. On three aspects performance of the average end-to-end information delay, the end-to-end throughput and the average energy consumption, the simulation results were analyzed and research. And the results base on WOO-MAC protocol showed better performance than IEEE802.11 and S-MAC.