Measurement, calibration and pre-processing of signals for single-ended subscriber line identification (original) (raw)
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Calibration and Pre-Processing of Signals for Single-Ended Subscriber Line Identification
2003
Abstract—A preprocessing algorithm is proposed to visualize the time-domain one-port scattering parameter of a subscriber line measured at the Central Office. To overcome the high line attenuation and the mismatch between the line and the measurement instrument, a preprocessing algorithm is developed to obtain numerically the impulse response of the one-port scattering parameter. The algorithm will search for a quasi-optimal base impedance for the scattering parameter; then, it will de-noise and de-alias the impulse response and will provide an estimate for the first meaningful significant reflection. Index Terms—Impulse response, scattering parameter, time alias, time-domain reflectometry (TDR), transmission lines. I.
Preprocessing of Signals for Single-Ended Subscriber Line Testing
IEEE Transactions on Instrumentation and Measurement, 2006
A preprocessing algorithm is proposed to visualize the time-domain one-port scattering parameter of a subscriber line measured at the Central Office. To overcome the high line attenuation and the mismatch between the line and the measurement instrument, a preprocessing algorithm is developed to obtain numerically the impulse response of the one-port scattering parameter. The algorithm will search for a quasi-optimal base impedance for the scattering parameter; then, it will de-noise and de-alias the impulse response and will provide an estimate for the first meaningful significant reflection.
Sequence Time Domain Reflectometry for Transmission Line Analysis
Anais do XXV Simpósio Brasileiro de Telecomunicações, 2007
This paper describes Sequence Time Domain Reflectometry (STDR), which utilizes concepts from direct sequence spread spectrum communications, as a technique for detecting impedance mismatches in telephone lines (twisted pair). The aim of this paper is to present methodologies for characterizing a subscriber loop, which is used for Digital Subscriber Line (DSL) technology, based on STDR tests. Those tests enable the TDR functionality to be incorporated into a DSL transceiver integrated circuit eliminating the need for costly test equipment. In addition to the cost savings, the characteristics of the STDR offer improved spectral compatibility, interference immunity and fault resolvability.
Sequence and spread spectrum time domain reflectometry for transmission line analysis
Proceedings of SPIE - The International Society for Optical Engineering, 2007
This paper describes Sequence Time Domain Reflectometry (STDR) and Spread Spectrum Time Domain Reflectometry (SSTDR), which utilizes concepts from direct sequence spread spectrum communications, as a technique for detecting impedance mismatches in telephone lines (twisted pair). The aim of this paper is to present methodologies for characterizing a subscriber loop, which is used for Digital Subscriber Line (DSL) technology, based on STDR and SSTDR tests. Those tests enable the TDR functionality to be incorporated into a DSL transceiver integrated circuit eliminating the need for costly test equipment. In addition to the cost savings, the characteristics of the STDR and SSTDR offer improved spectral compatibility, interference immunity and fault resolvability.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2009
Digital subscriber lines offer the possibility to deliver broadband services over the existing telephone network. Still, beforehand subscriber loops must be tested to see whether they can support high-speed data services, and at what bit rate. From the existing measurement techniques, Single Ended Line Testing is often preferred because all necessary measurements can be performed from the central office. Consequently the capacity cannot be measured directly, but should be calculated through the estimation of the loop make-up. This paper discusses some main difficulties of this identification. Moreover, in contrast to the traditional approach where the data are interpreted in the time domain, this paper presents a new approach by doing most of the processing in the frequency domain.
IEEE Journal on Selected Areas in Communications, 2002
In order to qualify a subscriber loop for xDSL transmission, the channel capacity has to be estimated, which depends on the transfer function of the network. In this paper, a method is provided to estimate the transfer function of the subscriber loop only measuring the one-port scattering parameter at the central office. We consider three types of networks according to their topology: a single line, a homogeneous network with a bridged tap, and a cascade of two line sections. For each type of network a parametric model is derived of its one-port scattering parameter and transfer function based on the physical line model VUB0. The model for the scattering parameter is used to identify the network based on the corresponding measurements by means of a maximum-likelihood estimator. The estimated parameters are substituted in the transfer function model, which is needed for the capacity estimation. The proposed models and estimators are validated by measurements and simulations. For the measurements, which were performed with a network analyzer, three types of twisted-pair cables were used: British Telecom (BT), Deutsch Telekom (FT), and Belgacom.
Single-Ended Line Testing - a White Box Approach
2000
A measurement, modelling and identification system is proposed to qualify a subscriber line with the constraint that only measurements can be conducted at the Central Office. The system uses the one-port scattering parame- ter as a base measurement of the loop. The time domain version of this scattering parameter will be pre-processed so that the features, which are the start,
TOPOLOGY ESTIMATION OF A DIGITAL SUBSCRIBER LINE
IAEME PUBLICATION, 2013
Topology estimation of a Digital subscriber line (DSL) is critical for an operator to commit a quality of service (QoS) requirement. Single Ended Loop Testing (SELT) is the most preferred and economical way for estimating the copper loop topology. A new method employing a combination of complementary code based Correlation Time Domain Reflectometry (CTDR) and Frequency Domain Reflectometry (FDR) for loop topology estimation is developed. Use of existing modem without any additional hardware in the measurement phase is the unique advantage of this method. Since the measurement is done online the effect of cross talk and AWGN is also considered. In this proposed SELT method approximate loop estimation is first obtained from CTDR measurements. An optimization algorithm based on FDR is then used to predict a more accurate loop topology. Employing FDR measured data and the FDR data of the approximate CTDR predicted topology, an objective function is defined. The objective function is then minimized using Nelder-Mead multivariable optimization method to get an accurate loop estimate. Tests carried out on typical ANSI loops shows good prediction capability of the proposed method. No prior knowledge of the network topology is required in this process. For the estimated loop topology capacity in terms of data rate is calculated and is compared with the capacity of the actual loop.
Proceedings of SPIE - The International Society for Optical Engineering, 2006
This paper presents methodologies that could be used for characterizing subscriber telephone loops that carry DSL services (ADSL and ADSL2+), by determination and analysis of frequency response, time domain reflectometry, and impulse response of the line. From this analysis, the subscriber loop length, identification and location of impairments such as bridged taps, gauge changes, and open ended termination across the line are carried out. To verify the methodologies presented, results obtained from measurements are drawn and compared to results obtained from computational simulations.