Guo Li-li

Research of Spectrum Detection Technology in Cognitive Radio

Cognitive Radio is an intelligent wireless communication system which is aware of its environment. It makes corresponding changes in operating parameters in real time and realizes dynamic spectrum access according to such a protocol that it doesn’t interfere with the licensed users in the band. Cognitive radio technologies could solve the problem of radio electromagnetic spectrum scarcity. Multitaper spectrum estimation has high accuracy and near-optimality. Singular value decomposition is used to eliminate noise of multi-sensor eigenspectrum and estimate interference temperature. The improved method of the singular value decomposition holds the accuracy and realizes interference temperature estimation.

BER Performance Of Complex Parallel Combinatory Spread Spectrum Communication System

This paper presents a novel composite parallel combinatory spread spectrum (CPC/SS) communication system. CPC/SS system can be designed to have more higher data transmission capability than spread spectrum (SS) communication system, even several times on Gaussian channels compared to ordinary parallel combinatory spread spectrum (PC/SS) system. In the proposed system, modulation of position code and state are applied to each simultaneously transmitting PN sequences. The symbol error rate and average bit error rate are analyzed to evaluate the performance of the proposed systems. Furthermore, CPC/SS system has excellent secret property than PC/SS and CDMA communication systems.

Analysis on Spatial Correlation Related with Antenna Array of MIMO System

In this paper, the spatial correlation analysis was based on a circular antenna arrays. The antenna was placed on the circle equably. So, the distance between antenna elements was considered in the analysis. At the same time, the formula of spatial correlation at the receiver was educed, which was aimed at circular antenna arrays. The correlation between antenna elements changed due to the changed antenna distance, the angle spread and the average angle of arrival direction of the signal. The antenna correlation changed with the angle spread changed. At this paper, the equality distributing of angle spread was considered. Each parameter that influenced spatial correlation was analyzed, the simulation figure demo the results derived by the formula. It was important to the analysis of the MIMO systems estimation and design.

Complex Position Code Parallel Combinatory Spread Spectrum Communication System with FEC Technique

Complex Position Code Parallel Combinatory Spread Spectrum (CPC/PC/SS) communication system with forward error correction (FEC) coding scheme is proposed in this paper, and performances are analyzed. CPC/PC/SS system with FEC coding scheme can be designed to have higher data transmission capability, even several times compared to ordinary PC/SS system on Gaussian channel.The proposed FEC coding is separately applied to the combination data of orthogonal codes and the state data of their transmitting orthogonal code, and less redundant FEC code is enough to the state data of orthogonal codes by this coding scheme. Therefore, the total information rate exceeds that offered by the conventional overall FEC coding is applied. Simulation results show that the error rate performance of the CPC/PC/SS systems equipped with the proposed FEC coding is lower than conventional PC/SS system.

BER Performance of Position Code Parallel Combinatory Spread Spectrum System

A novel position code parallel combinatory spread spectrum (PC/PC/SS) communication system is proposed in this paper. PC/PC/SS system can be designed to have higher data transmission capability, even several times compared to ordinary PC/SS system on Gaussian channel. In the proposed system, modulation of position code is applied to each simultaneously transmitting PN sequences. The symbol error rate and average bit error rate performances are analyzed to evaluate the performance of the proposed systems. Furthermore, PC/PC/SS system has excellent secret property than PC/SS and M-ary/SS systems.

Developed BP Algorithm in Moisture Content Measurement

How to reduce the measurement error caused by linear regression is the key in measuring tea moisture content with microwave transmission techniques. In this paper, an improved BP algorithm, which combines the genetic algorithm, is given for training artificial neural network to get the range of weights and thresholds. The method makes BP algorithm avoid getting into infinitesimal locally and has the merits of high prediction precision and rapid convergence. The results show that the mean squared error is 0.0116, the mean absolute error is 0.0738, the mean relative error is 0.1182 and the certain coefficient is 0.9863 between the predicted value and the real one.

CUWB multiband adaptive pulse design based on frequency domain

Traditional ultra wide band pulse not only has low spectrum utilization, but also causes interference with existing systems easily. In order to solve the problem, a cognitive ultra wide band multiband adaptive pulse is proposed combining the advantages of cognitive radio and ultra wide band communications. First system searches the available band and divides it into several subbands. Then designs the subband pulse using finite prolate spheroidal wave functions. Finally subband pulses are combined in time domain. Simulation results show that the pulse enhances the spectrum utilization efficiency and has a strong flexibility and anti-jamming capability, can seamlessly modify waveform to achieve coexistence with existing narrowband systems.

A novel Position Code Parallel Combinatory Spread Spectrum communication system

This paper presents a novel Position Code Parallel Combinatory Spread Spectrum (PC/PC/SS) communication system. PC/PC/SS system can be designed to have higher data transmission capability, even several times compared to ordinary PC/SS system on Gaussian channel. In the ordinary PC/SS system, multip1e pseudo-noise (PN) sequences are simultaneously transmitted out of a pre-assigned spreading sequence set. In the proposed system, modulation of Position Code is applied to the starting position of each simultaneously transmitting PN sequences. The symbol error rate and average bit error rate are analyzed to evaluate the performance of the proposed systems. Furthermore, PC/PC/SS system has excellent secret property than PC/SS and M-ary/SS communication systems.

Optimal IA-BP Algorithm in Moisture Content Measurement

BP algorithm has been widely used in calibrating measurement results detected by microwave resonator for improvement of accuracy. Conventional BP algorithm tends to get into infinitesimal locally, which worsens the stability of the measurement accuracy. An evolutionary neural network model based on IA-BP optimal algorithm is proposed in this paper. In the model, IA algorithm is first used for global search and then BP algorithm for local search. Experiments indicated that the IA-BP optimal algorithm effectively avoid getting into infinitesimal locally and has the merits of high prediction precision, rapid convergence, global superiority and accuracy for optimization, which improves the measurement accuracy with the mean squared error 0.0125, the mean absolute error 0.0715, the mean relative error 0.1186 and the certain coefficient 0.9965 between the predicted moisture content and the real value.