Channel Modeling And Fault Location Of Coaxial Cable Access Network

With the popularity of high-definition multimedia, interactive network games, cloud access technology and other high-bandwidth services applications, users increasingly high demand for data communication rate, so that high-speed access networks have become the focus of the current communication technology. Coaxial cable network with wide coverage, numbers of users, has got a lot of attention. A number of coaxial access technologies, such as DoCSIS (Data over Cable Service Interface Specification), EoC (Ethernet over COAX), EPoC (EPON Protocal over Coaxial Distribution Network), has arisen both at home and abroad. The coaxial cable access has become the focus of the access technology at the context of triple playThe thesis aims to study the channel characteristics of the coaxial cable distribution network and fault diagnosis. Based on the site test of coaxial cable networks and the experiment, the channel characteristics of the distribution network, such as the transmission characteristics, noise and the fault diagnosis and location are researched in the thesis, the frequency range is from5MHz～1.2GHz. The work is helpful for the understanding of the coaxial cable access technology. The main contents including:(1) The electromagnetic modeling of the splitter and tap is studied. There are three methods:ABCD matrix modeling, ADS software-based modeling and the S-parameter matrix modeling. These three methods are used to do model for the two-way splitter and one-way tap which the basic elements of the other splitter and tap. With the aid of the cascade relationship and the characteristics of the two basic elements, the other splitter and tap can be calculated. The example of each method is shown and the comparison is making among the three methods. Based on genetic algorithms, the Debye series modeling of the core which is the important part of the splitter and tap is studied, with the accurate modeling of the core, the simulated results are very agreement with the measured results of the transmission characteristics of splitter and tap.(2) Several methods are used to do modeling for the coaxial cable network, including curve fitting, ABCD matrix, S-parameter matrix and ADS software-based method, a novel and more comfortable method named "S-parameter based multipath channel modeling" is introduced. The S-parameter of the proposed modeling is obtained by the actual measurement with VNA, so that the simulated results are very close to the testing results, the relative error of amplitude-frequency curve and phase-frequency curve is almost less than5%. The simulated software based on the novel channel modeling is completed, which can estimate the transmission characteristic of channel between any two ports in the analytical network, including the amplitude-frequency curve, phase-frequency curve, group delay and the TDR.(3) The noise of the coaxial cable network channel is classified and modeled. According to the characteristic of the noise, the main noise in the cable network can be classified into three types, including background noise, narrow-band noise and the impulse noise. The probability density function of each noise is analyzed, and the measured noise is decomposed. Each noise is modeled according to the PDF, which can simulate the amplitude-frequency curve of each noise and aggregate noise.(4) Tow novel method for the fault diagnosis and location of coaxial cable network is proposed. The first one is based on the use of Principal Component Analysis (PCA) and BP Neural Network, which can calculate the type of fault (such as short circuit, open circuit, soft fault) and the location of fault. Another method is based on the Support Vector Machine (SVM) to diagnose and locate the fault.