Digital Loop Carrier Research Articles

Measurement and Test Performance for Integrated Digital Loop Carrier for White Noise Impairment Using Interleaved Mode

This paper presents results of measurement and test performance for integrated digital loop carrier (IDLC) technology. The study focuses on cable modem termination systems (CMTSs) that are reported on assortments of operating parameters to the end user based on upstream and downstream modes that are incorporated with statistical analysis approach. The study focuses on the statistical analytical measurement for noise margins on a particular type of loops – “white noise impairment.”

Measurement and Test Performance for Integrated Digital Loop Carrier for White Noise Impairment Using Interleaved Mode

ABSTRACT This paper presents results of measurement and test performance for integrated digital loop carrier (IDLC) technology. The study focuses on cable modem termination systems (CMTSs) that are reported on assortments of operating parameters to the end user based on upstream and downstream modes that are incorporated with statistical analysis approach. The study focuses on the statistical analytical measurement for noise margins on a particular type of loops--white noise Keywords: integrated digital loop carrier, DSL, broadband, interleaved mode INTRODUCTION Service providers in the past have extensively used digital loop carriers (DLC) in delivering reliable, robust and high quality voice service to end users. Recently, telecommunications network providers (TNP) improve and change their path in broadband technologies for better services and costs reduction to customers. As a result, they increased the number of lines with extended distances from Central Office (CO) with high quality of services in voice and data. From analog technology in plain old telephone services (POTs) to digital in DLC, TNP have made great stride and break through to service providers and end-users. Digital loop carrier (DLC) technology is based on digital techniques to provide large services to users via copper lines. In today technologies, IDLC systems are broadly installed in delivering telecommunications services. Significant wiring and advantages of cost can be profited with IDLC at remote locations. In this work, the study illustrates the statistical analysis for the results of measurement of a test performance for integrated digital loop carrier (IDLC) type of white noise impairment. This paper is arranged as follows: A review of literature provides an overview of voice over digital subscriber line (VoDSL), digital subscriber line (DSL), and carrier serving area (CSA). A description of the DLC and IDLC are then presented, with a discussion and network setup following. Regression analysis is then presented, with statistical analysis and hypothesis testing on the difference between the two means, of the noise margin, of the upstream and downstream cases in the interleaved mode setup completing the section. The paper is completed with a summary of the results and the conclusion. LITERATURE REVIEW Early studies showed that the first generation integrated access systems served as a platform for delivering voice, data and voice services over multiple T1/E1 lines and OC-3 fiber link. Later studies showed that the universal digital loop carrier system (UDLC), evolved into what are now known as the integrated digital loop carrier (Opara & Etnyre, 2010) Musa, Akujuobi, & Mir (2007) indicated that when measuring call quality, three categories of study include listening quality, conversational quality and transmission quality. According to Musa et al., the objective of call quality measurement is to obtain a reliable estimate of one or more within the above categories using either subjective or objective testing methods. A baseline test for the listening quality (LQ) using voice over digital subscriber line (VoDSL) access technology has been studied (Musa, Opara, Shayib, & El-Aasser, 2010). Researchers used voice/listening quality (V/LQ) transmission with voice compression while continuously downloading files. Indeed, those results enable the efficiency of the LQ and its statistical analysis based on a digital subscriber line (DSL) service at level 1.5M/384K for each American National Standards Institute (ANSI) and carrier serving area (CSA) loops. Furthermore, based on the experimental VoDSL network architecture and the following DSL service levels 640K/ 640K, 1.5M / 384K, 3.0M/ 512K, and 1.5M/ 256K for each ANSI/CSA loops by using voice quality transmission testing with voice compression while continuously downloading files, it was found that on certain loops, all eight derived lines were not supported on IADs for VoDSL solution (Musa et al. …

Deconstructing the Divide: Extending Broadband xDSL Services to the Periphery

One of the major challenges to providing full-rate digital subscriber line (xDSL) access to residential customers in rural or remote locations is the use of existing copper infrastructure. First, copper is not particularly good for moving high frequencies over extended distances. Second, much of the existing copper in the United States is of diminished quality. Third, digital loop carriers, bridge taps, load coils, and ambient interference negatively impact data transmission. Because of these problems, the geographic reach of xDSL services is limited. To combat this limitation, providers are installing remote digital subscriber line access multiplexers (RDSLAMs). RDSLAMs seek to maximise the amount of demand covered for a peripheral neighborhood and aggregate this data traffic onto a fiber optic connection for transport back to the central office (CO) for switching. Although this is more feasible than constructing a new CO, acquiring the rights of way and installing fiber is expensive. The purpose of this paper is to examine the complexities associated with locating RDSLAMs in a competitive telecommunications market through the use of an integer programming model—the remote access hierarchical assignment problem—and a geographic information system. Pertinent policy and technology related issues in residential broadband deployment and their impacts on high-speed services such as xDSL are highlighted.

Modeling and simulation of mixed traffic on a prioritized shared medium

AbstractNetwork access systems (NAS) such as digital loop carriers (DLC) are increasingly utilizing a shared medium, such as Hybrid Fiber Coax (HFC) to provide point‐to‐multi‐point access from the public switched telephone network (PSTN) to the end user (consumer). New services, such as direct access to the packet switched network (PSN, WWW) have been added to DLC equipment in such a way as to provide for a prioritized set of services over a shared medium in an effort to take advantage of otherwise unused bandwidth. The introduction of such services requires the modeling and analysis of these network access systems. This becomes complex when considering the variability in different service type traffic characteristics. This work identifies a traffic engineering problem of prioritized circuit switched and packet switched (PSTN/PSN) traffic over the same shared medium as it may relate to “perceived” quality of service (QoS). Copyright © 2002 John Wiley & Sons, Ltd.

Digital loop carrier solutions for voice and data networks

Lucent Technologies' SLC®-2000 digital loop carrier (DLC) system has traditionally been used to provide telephony services ranging from “plain old telephone service” (POTS) to digital data systems (DDS) to integrated services digital network (ISDN) over T1 and SONET digital facilities. This paper describes how the SLC-2000 Access System has been evolved recently to support clear channels for lines that traditionally use bit robbing to carry in-band signaling information. This enhancement restores modem performance that has degraded due to robbed bit signaling (RBS) and provides subscribers with improved data services. The paper also discusses enhancements to the SLC-2000 system to provide subscriber access not only to the circuit-switched telephony network but also to the packet-switched data networks for integrated voice and data services.

The evolution of digital loop carrier

The development of systems that apply digital multiplexing technology to the loop is examined. The analog carrier foundations of the present loop are reviewed, and the introduction of digital technology is described. The maturing of digital loop carrier (DLC) systems, integration of digital switching and loop transmission, operations issues, and factors that could constrain deployment of DLCs on a large scale are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High bit rate digital subscriber line: a copper bridge to the network of the future

It is argued that the high bit rate digital subscriber line (HDSL), permitting low-cost 1.5 Mb/s copper access, will ease the transition to fiber access by accelerating the use of higher speed services. Copper will dominate over fiber customer access for at least the next ten years. During this period, the success of high-speed switched services will depend on the connectivity provided by both fiber and copper access. HDSL will initially be used to serve private-line DS 1, ISDN primary rate access, and digital loop carrier feeders. Later, the HDSL will be applied to switched services such as metropolitan area networks (MANs) and circuit switched DS1s.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A call-processing traffic study for integrated digital loop carrier applications

The results of a traffic study undertaken to determine if a 64 kb/s common-signalling channel is sufficiently fast to meet the present and future call-processing needs of integrated digital loop-carrier (IDLC) systems are presented. Bell Communications Research (Bellcore) has proposed the use of such a 64 kb/s common signalling channel in a requirement document, technical reference TR-TSY-000303, to satisfy call-processing needs across the IDLC generic interface, whenever out-of-band signalling is used. The IDLC call-processing traffic on this message-oriented common-signalling channel is characterized, and associated design requirements in TR-303 under certain modelling assumptions (Poisson arrivals and exponential service time) are examined. Under worst-case conditions, it is concluded that a critical message requiring a response within 100 ms would practically always meet that delay criterion. Critical messages requiring a response within 40 ms would fail once every 10 busy hours. Since no specific signalling response requirement of 40 ms has been found, the authors conclude that a 64 kb/s common-signalling-channel for IDLC system is sufficiently fast to achieve required signalling response times.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A generic operations system interface to support the next generation of digital loop carrier systems

The application of a generic interface between operations systems and microprocessor controlled network elements (OS/NE) to both universal and integrated DLC (digital loop carrier) systems is discussed. The high-level components of a DLC system are defined, and a generic interface between operations systems and their central office terminal of a microprocessor-controlled DLC system is described. The adaptation of the generic operations-systems interface to the DLC system for use with a generic interface between the local switching system and the remote digital terminal of an integrated DLC system is explored. Some issues associated with integrating a DLC system into a switching system are presented. >

A generic integrated maintenance interface for network elements

A generic interface specification that could be used as a common definition for maintenance functions is described. The process of developing the generic interface specification is presented, including the definition of supported functions, the description of the protocol and language used, and the detailed enumeration of the message specifications to support these functions. Generic interfaces can provide economic advantages in software development, training, and opportunities for simplification of human interfaces for remote interaction with the intelligent network element. The specific case examined is the set of messages that have been developed for system maintenance of network elements including digital loop carrier, digital terminal and cross-connect equipment, digital multiplexing and line-terminating equipment, digital switching equipment, common-channel signaling systems, supervisory systems, environmental monitors, and network timing elements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Lightguide Applications in the Loop

Traditionally, the telephone network has been dominated by voice traffic. With the rapid growth in computers, integrated workstations, automated banking machines, digital PBXs (private branch exchanges), etc., today's voice network must evolve to a wideband network that can support voice, data, and video. This changing environment puts new demands on the telephone network, especially the local access portion. Accurate forecasts for new services and the mix of services are difficult to obtain. Therefore, a network must be developed that can accommodate a wide range of services and, at the same time, change as rapidly as new services evolve. Lightwave systems and digital loop carrier offer many of the characteristics necessary for this flexible network. This article describes AT&T's DDM-1000 lightwave multiplexer and SLC® Series 5 carrier system for loop applications.

TheSLC 96Subscriber Loop Carrier System: Physical Design

The successful deployment of digital loop carrier systems by the operating companies is highly dependent on the physical and mechanical design of the electronics. A comprehensive description of the SLC® 96 subscriber loop carrier system central office and remote terminal equipment design is presented. Particular emphasis is placed on the loop plant electronics enclosures developed for operation in uncontrolled outside environments. Remote terminal thermal design guidelines are also presented, since thermal control of the environment surrounding the electronics is essential to long-term reliable operation. Throughout this paper, physical design requirements and objectives for digital loop carrier design are summarized.

TheSLC 96Subscriber Loop Carrier System: Maintenance and Operation

The success of digital loop carrier depends not only on economic considerations, but also to a great extent on the ability of the operating companies to maintain, administer, and operate this technology. This paper discusses a generalized digital loop carrier operations plan and describes the SLC® 96 carrier system features that satisfy the requirements of the operations plan. A thorough explanation of the SLC 96 carrier maintenance features is included. The paper covers system maintenance philosophy, alarm structure, and line testing methodology.

TheSLC 96Subscriber Loop Carrier System: Overview

Like all digital transmission systems, digital subscriber loop carrier seems destined to play an ever-increasing role in modern communication networks. This trend derives its strength from basic and pervasive factors: (1) the great ease with which digital transmission can support new services, particularly those related to any form of data transmission; (2) the seemingly inexhaustible potential of digital integrated circuit technology to realize ever-decreasing cost, size, and power-per-circuit function; (3) the great promise digital transmission holds for synergy with digital switching. This paper provides an overview to a series of papers that describe in detail AT&T Technologies eminently successful entry in this market, the SLC® 96 Subscriber Loop Carrier System. Emphasis is placed on the background leading to the development and the forces that shaped the system's architecture.

TheSLC 96Subscriber Loop Carrier System: Integration With the5ESSSwitching System

A new 5ESS™ switching system peripheral unit provides an efficient integrated interface to Remote Terminals (RTs) of the SLC® 96 digital subscriber loop carrier system. This unit has been named the Digital Carrier Line Unit (DCLU). Each DCLU serves up to six remote terminals [576 Plain Old Telephone Service (POTS) lines]. Each Tl line from an RT terminates on a Digital Facility Interface (DFI) circuit pack, which is the microcomputer-controlled circuit pack used in the 5ESS switching system to interface to Tl lines. The DCLU consists of up to thirty of these DFIs. For purposes of control, the DFIs are separated into two service groups of fifteen DFIs each. There is one control multiplexer circuit pack for each service group. Also there are two data multiplexer circuit packs that are shared by all thirty DFIs. The design of the DFI is described in this paper. The software structure of the 5ESS switching system is explained in general terms and then the software that had to be expanded to support integrated SLC 96 carrier systems is outlined. The paper concludes by describing the topology and traffic-handling capability of the two-stage switching network formed by the DCLU and the remote terminals that are connected to it. The first SLC 96 carrier system integrated into a 5ESS switch went into service on April 14,1984, in Spotsylvania, Virginia.

TheSLC 96Subscriber Loop Carrier System: The FiberSLCCarrier System

The advantages of digital loop carrier systems operating on wire pairs can be enhanced by the use of lightguides in place of wire pairs. Lightwave systems can provide wide bandwidth capability, small cable size, long-range repeater-less operation, and immunity to electromagnetic interferences. This article describes the development of a 1.3-μm LED/PIN based system designed specifically for the loop environment.

Description and application of the fiber SLC carrier system

The Fiber SLC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> Carder System is a repeaterless digital loop carrier that employs lightwave features for the transmission of voice and data from a telephone central office to a remote location. This paper describes the development and application of this 1.3-μm LED/p-in based system. Experience with first applications is reported along with current developments intended to increase its capacity and bring digital capability close to the customer at the DS3 bit rate (44.736 Mbits/s). Services to the customer include DS1 port capability (1.544 Mbits/s), DS2 optical paths (6.312 Mbits/s), voice, and data.

Feeder Planning Methods for Digital Loop Carrier

This paper describes three new approaches to planning for digital loop carrier (DLC) in the exchange feeder loop network. Two of these are manual planning methods that are used to determine the most economical technology for satisfying facility shortages along a feeder route. Both are based on the concept of a distance-oriented crossover point beyond which DLC is the economic relief technology. One of the methods uses a global crossover point for alt routes, and the other uses a route-specific crossover point The third approach is a mechanized toot, the Pair Gain Planning (PGP) program. PGP, which is implemented as a module within the existing Bell System loop planning system, first identifies the appropriate technology for relief and then synthesizes a specific DLC implementation plan. A discussion of system performance and projected Bell System applications of the various methods is included.

Administration of New Feeder Technology

New technologies, such as digital loop carrier (DLC) and remote switch units (RSU's) are being deployed in the subscriber network. To minimize total cost, not only must the characteristics of the device and the application be well matched, but a third factor must be considered as well-the administrative plan. This paper illustrates the ways in which the administrative plan impacts both TelCo capital and operations costs, and may even affect the subscriber. Administration of RSU's deployed for general feeder relief is considered first under existing pair gain and wire center plans. A custom designed adminstrative plan, extended office, is then shown to offer significant benefits over either of the standard alternatives. Adminstration of "giant" carrier sites is also considered. Though a modification to the pair gain plan is proposed, all the key concerns could not be addressed. Indeed, a completely satisfactory plan may not be possible until the DLC can be "integrated" with a host digital switch.

Positioning the Subscriber Loop Network for Digital Services

The need to enhance the digital transmission capability of the local loop network to provide for new services is widely recognized in the telecommunications industry. Companies around the world [1]-[3] have been working towards this goal and plan to use digital loop carrier (DLC) to meet this demand. Although this approach is generally accepted, there has been little information presented on how to plan for the evolution of the local plant. To address these pressing issues, the Bell System is introducing a concept called fundamental subscriber carrier planning (FSCP). This paper discusses the impact that digital services will have on the subscriber loop network, including loop plant design requirements necessary to position the network for up to 64 kbit/s digital services. Existing cable plant has the capability to support most digital services, but there are specific design requirements that are quite different from those required for the typical analog voiceband service. This paper reviews the need to position the loop for digital services, and substantiates the major conclusion that digital loop carrier technology offers a significant advantage when provisioning for digital services.