A method determines a structure of a subscriber line. The method includes searching a reference set for a match between the subscriber line and a model line of the reference set and identifying that the subscriber line has a specific physical structure. The match is based on electrical properties of the lines. The act of identifying is responsive to finding a match with one of the model lines that has the specific physical structure.

Determining the physical structure of subscriber lines

A method characterizes a customer line for data transmission. The method includes measuring electrical properties of the customer line from a central location, identifying a line model from the measurements, and identifying a modem model for a modem selected for use with the customer line. The modem model gives performance data for the selected modem. The method also predicts performance data for the customer line when operated with the selected modem by combining the line and modem models.

Predicting performance of telephone lines for data services

Using the World Wide Web at 28.8 Kbps (or less) can be a frustrating experience: a multimedia page that takes a fraction of a second to download at Ethernet speeds takes many seconds at modem rates. Two enhancements to existing infrastructure have the potential to deliver more satisfactory residential Internet access: ISDN telephone service, and upgraded cable TV networks. While ISDN dedicates bandwidth to each user, cable networks support a shared bandwidth approach similar to that used in computer Local Area Networks (LANs). This report describes the technologies and evaluates qualitative differences between the two approaches. It presents quantitative results of capital cost models based on case studies of the PSICable deployment in Cambridge, MA, and the Internet over ISDN service offered by Internex, Inc. in the San Francisco, CA area. The report finds that cable''s shared-bandwidth approach has superior economic characteristics. For example, 500 Kbps Internet access over cable can provide the same average bandwidth and four times the peak bandwidth of ISDN access for less than half the capital cost per subscriber. The economy of the shared bandwidth approach is most evident when comparing the per-subscriber cost per bit of peak bandwidth: $0.60 for the 500 Kbps cable service versus close to $16 for ISDN. Cable-based access also has better service characteristics: it can support both full-time Internet connections and higher peak bandwidths, such as a 4 Mbps cable service that provides thirty-two times the peak bandwidth of ISDN. The report concludes with an analysis of the barriers to diffusion of cable and ISDN Internet access, including business and policy factors. It finds that the closed market structure for cable subscriber equipment has not been as effective as the open market for ISDN equipment at fostering the development of needed technology. Furthermore, monopoly control of residential communications infrastructure--whether manifest as high ISDN tariffs or simple lack of interest from cable operators--limits business opportunities for Internet service providers.

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Connecting Homes to the Internet: An Engineering Cost Model of Cable vs. ISDN

This paper reviews the telephone loop plant characteristics, current DSL (digital subscriber line) technologies, recent efforts in video coding standards, and the interrelationship between DSL technologies and visual communications over subscriber lines. In overview of the loop plant characteristics we examine its physical makeup and transmission properties, where for the latter we discuss frequency and time responses of wire-pair lines and the impairments of echo, crosstalk, impulse noise, and radio frequency interference. We trace the historical development of various DSL technologies and comment on possible future evolution. Transmission technologies used in the ISDN basic-access DSL, the high bit-rate DSL, and the asymmetric DSL are portrayed. And the issue of spectrum compatibility among different transmission systems is explained. Several important video coding standards are briefly described, including ITU-T's H.261 and ISO's JPEG and MPEG series, which are either completed or emerging. The synergistic relationship between these standards and the DSL technologies is elucidated. As a result, DSL technologies provide the potential of delivering certain broadband services well in advance of direct fiber access for telephone subscribers. >

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Video on phone lines: technology and applications

A method and system for qualifying telephone lines for high speed data services. The system takes measurements on a line under test and matches those measurements to a model of a line. The model of the line is used to predict whether the line will support data services at a particular level. If the model of the line includes a service affecting condition that is removable from the line, a new model is created reflecting the line as it would appear with the service affecting condition removed. The new model is then used to predict performance. If the required performance level is predicted based on the new model, the line is categorized as a line that can not support the required level of data services, but could if repaired. In this way, an accurate and useful prediction of line performance is provided.

Method and apparatus for bridged tap impact analysis

About 2800 lines out of a total of 8,500,000 subscriber lines in Taiwan have been sampled and characterized. Various kinds of physical compositions and transmission characteristics were investigated and measured. It was found that the near-end crosstalk (NEXT) loss of Taiwan's subscriber loops is about 10 dB worse than that of US local loops. A corresponding new foam-skin PIC cable is proposed to reduce the NEXT loss. The new type of cable will be used to replace the paper cable and old foam-skin PIC cable step-by-step. Based on the measured data, the feasibility of HDSL (high bit rate digital subscriber line) service in Taiwan is studied. To improve the HDSL service distance via the existing subscriber lines, several cable models are discussed and suggested. >

W.-K. Hwang

Papers

Loop survey in the Taiwan area and feasibility study for HDSL