Advanced Materials Research Vols. 846-847

Abstract: In this paper, we study the problem of enhancing the fault tolerance of IEEE 802.11 wireless local area networks in the design stage. We aim to settle proper number of access points (APs) and carefully locate them, such that the system can tolerate AP failures while guaranteeing QoS requirement. Given a set of clients (end-users), each client has a traffic demand for Internet access. The problem of our concern is to find out the minimal number of access points and proper location, such that the fault tolerance and QoS constraint are both satisfied. That is, when there is no AP failure, the actual traffic delivery ratio for each client shall exceed the threshold. When their happens that one AP failed, the clients it served can switch to other APs with reconfiguration of the system, while providing an acceptable bandwidth. We proposed a heuristic algorithm, firstly we place one AP in each candidate place and gradually decrease the APs until no more APs can be deleted, in each step we make fault tolerance checking. Our proposed method can effectively solve the problem of tolerating to access point failure in the design phase of wireless local area networks. Simulations are conducted to show the performance of our proposed method.

Abstract: Under unfavorable wheather conditions, such as mist, dew and drizzle, contamination flashover may occur on polluted insulators. According to the properties of radiation, this paper proposes a new method for detecting the pollutant on insulators by the dual-channel Dicke radiometer based on the pollutants radiation characteristic and the theory of component emissivity. This study fully considered the effect that the radiation energy of multiple scattering and the external environment on antenna temperature, and it described by the structure of antenna temperature with matrix. A new dual-channel Dicke radiometer has been developed to measure the radiation characteristics of insulators. With a large number of data obtained by experiments, the relationship between ESDD/NSDD and the antenna temperature was researched. And it proposed an empirical formula to calculation ESDD and NSDD. This study provides a new method of detecting insulator contamination by microwave radiometer.

Abstract: The real-time prediction of micro regional market share provides decision for the analysis of micro regional marketing scheme and micro regional channel planning. More and more increasing complexion mobile network environment require real-time micro area of market share and only mastering micro regional market share can have a more comprehensive understanding of market. To solve this problem, consideration of advantages of real-time aspects of the extended Kalman filtering algorithm in predicting, we propose a real-time prediction algorithm based on the extended Kalman filter Market Share. The algorithm can be real-time prediction of mobile network market share of base station. The simulation results show that the proposed algorithm in this paper is a real-time and good prediction quality.

Abstract: It is one of the important technologies to realize the wireless network communication in the special marine environment. The fog that contains salt and water above the surface of the sea has certain influence on the attenuation of electromagnetic field in the wireless communication. The attenuation coefficient of electromagnetic wave in such medium is discussed in this paper, by replacing the permittivity of the salty fog with that of the NaCl solution. And then such attenuation coefficient will be introduced to the electromagnetic fading model with the sight considered. Finally, this paper designs a electromagnetic wave attenuation model of the sea, which could provide some suggestions for establishing wireless communication network on the sea.

Abstract: For the performance of wireless sensor network, topology control plays an important role. In order to save energy, prolong the lifetime of the network and reduce the interference between nodes, while ensuring the connectivity and reliability of data transmission, we propose a suitable scheme which is hierarchical topology control with distributed and a long-chain structure based on the monitoring of transmission and distribution lines. It is based on the study of the monitoring of transmission and distribution lines in wireless sensor network.This scheme will cluster with the deployed nodes, and fuse with data in the selected cluster head,in order to complete topology structure.To matlab optimization platform, using ant colony optimization algorithm to remove some redundant links, so that data transmit to the monitoring center reliably and complete real-time monitoring of the lines,thus prolong the lifetime of the network.

Abstract: Traditional signal generators use analog oscillator circuit as the source, which often involve multiplication, integral and differential circuit. As this method required high electrical parameters of the system, and its complex circuit structure is vulnerable to outside interference. In this paper, a new technology named Direct Digital Synthesizer, DDS technology, was applied on a FPGA chip to design a waveform generator. It can generate periodic waveform, and its frequency, phase and amplitude were adjustable. Simultaneously, DDS technology has the function of frequency and phase adjustment, so no additional circuit was needed. During the amplitude modulation design, the characteristics of reference voltage of the D/A Converter are used. The theoretical and experimental results show that the combination of DDS technology and FPGA can well generate the periodic signal waveforms, while the hardware system fabricated has strong capability of anti-jamming.

Abstract: The transmission line is an important part of electrical system. Electromagnetic interference (EMI) signals can be picked up by transmission lines in a way of conduction or radiation, and interfere the sensitive devices located in the power source end and the load end, so it is important and necessary to separate and identify the EMI source signals coupling to the transmission lines in order to guide the electromagnetic compatibility (EMC) design and the further EMI diagnosis and suppression. Fast independent component analysis (FastICA) algorithm is studied and programmed, and its feasibility and separation performance are validated via simulation of BSS of three mixed signals and the average signals to interference ratio (SIR) is approximately 30 dB. The model of crosstalk of transmission lines is built and simulated, the interference signals are separated by the FastICA algorithm, and the average SIR is over 20 dB. Periodicity and spectral characteristics of the separated interference signals are analyzed, and the identification of interference signals is realized.

Abstract: This paper analyzed several kinds of isolating DC/DC boost converting circuit. Choose isolating boost full bridge circuit as the main circuit of the DC/DC converter according to the designing requirements. Design the advanced isolating boost converting circuit, and use synchronous rectification in the full bridge rectifying circuit linked to the secondary side of the transformer to reduce the power loss of the main circuit and improve the overall efficiency. Analyze the working principle of the main circuit and the simulation mode. Considering the converter has to deal with huge power and current stress, this paper give instructions on the device selection and design method, including the selection of the lock-in tube MOSFET and transformer of the main circuit. At last, simulation of the system is run by using saber, which proves the theoretical analysis to be reasonable and correct.

Abstract: This paper introduces a new method for small diameter directional gyro inclinometer calibration with continuous measurement mode. The mathematical models referring to the relationship between the input and output of the accelerometers and the gyro are established. Experiment has been conducted for different angular speed and different positions on a three-axis turntable. We totally obtained 36 groups of experiment data of different angular speed regarding to different positions. Through the application of the established mathematical models and by means of computer aided data procession, the scale factors, installation error and static drift for the gyro inclinometer are calculated. Thus, the inclinometer calibration is implemented. It has been verified that this new calibration method enables us to quickly and effectively calibrate gyro inclinometer. The established mathematical model has been proved to be exact and effective. The whole operation is simple, quick and reliable.

Abstract: Considering the effects of temperature on output of silicon pressure sensor, this paper proposed a novel method for analyzing temperature compensation of pressure sensor by using the combination of Principal Component Analysis (PCA) and improved BP neural networks. By using PCA to extract the prime information of temperature compensation, the multi-dimensional problem is simplified, the noise error data is eliminated, the neura1 network is improved and the fault-tolerance capability is enhanced. The results indicate that this method can restrain the effects of temperature on pressure sensors effectively and enhance their stability and accuracy.