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TEL 355: Communication and Information Systems in Organizations

TEL 355: Communication and Information Systems in Organizations. Digital Loop Carrier (DLC) Professor John F. Clark. Definition of DLC. The local loop is the physical connection between the home or business user and the telco service provider

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TEL 355: Communication and Information Systems in Organizations

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  1. TEL 355: Communication and Information Systems in Organizations Digital Loop Carrier (DLC) Professor John F. Clark

  2. Definition of DLC • The local loop is the physical connection between the home or business user and the telco service provider • DLC uses digital technology to offer a wide range of services via copper 2X wires • The development of DLC technology is vital to the future of new online consumer services

  3. History of Subscriber Carriers • Loop carrier development originally focused on providing higher quality over longer distances • Was originally deployed in suburban and rural areas. • Relatively few lines and subscribers • Little attention paid to connection methods and signal strength (pair-gain capabilities)

  4. Analog Carrier Systems • Designed to provide phone service at distances greater than CO capabilities. • POTS and carrier multiplexer were analog • The advent of electronics in the 60s • Multiplexer connected to local exchange switch • Subscriber box served 1-8 customers • Limited technology, limited deployment • Was difficult to maintain and performance was inconsistent

  5. Digital Loop Technology • Early 70s – digital performance benefits • Improved voice quality and higher gain (12 to 1) • Added features: both analog and digital services • Reliable, easy to install and maintain • Architecture was digital on the network end and analog on the subscriber end • 96 line Remote Subscriber Terminal (RST) • Connected to a Local Exchange Terminal • T1 carrier between the terminals

  6. Early Next Generation DLCs • In the 80s – based on computer-driven Very Large Scale Integration (VLSI) technology • Primary purpose: deliver services such as • basic and primary rate ISDN • 56k and 64k data rates (DDS) • T1 and other analog services • Designed for fiber from the CO to the RST • Service to 2000 customers per RST • Widespread service was its downfall

  7. NGDLC: Rural/Suburban Uses • In the 90s – advanced computing and chip technology makes it possible & economical • Relies on software control and intelligence • Works over any infrastructure – digital T1 or T3, analog, fiber or coax • Based on a mixed network architecture and mesh topology that reflects actual suburban development patterns – its key to success

  8. NGDLC Applications • First and foremost – DLC emulation for many remaining analog carriers • Can be implemented a number of ways: • Universal DLC Emulation – old analog carriers • Drop and Insert Configuration – programmable RSTs in any network medium • Star Configuration – radiates T1, fiber, HDSL, or coax facilities • Tree/Mesh Configuration – a mixture of drop-and-insert and star topologies

  9. Special NGDLC Applications • Integrating voice and video: • Integrated Video/Telephony Point-to-Point • Integrated Video/Telephony Point-to-Multipoint • Hybrid systems that use RF technology to multiplex voice and video over coax and break out voice over 2X for the subscriber • Network flexibility allows any of these configurations to be used with any other for very cost-effective solutions

  10. Advantages of NGDLC • Very economical for suburban/rural areas • Cost effective for low line sizes • Low amount of common control overhead • Uses the existing infrastructure • Customers want more service & bandwidth • Means deploying more fiber • Implement the system and upgrade as needed • Pay for upgrades only when implemented

  11. Future Directions • Competition between HFC companies and telcos and between different telcos is driving development – especially in xDSL • Increasing use of the Internet and even higher bandwidth services is having an affect on development and on economics • Must supply increasing bandwidth while supporting narrowband economically – migration must be simple and cheap

  12. Economics • Equipment must be interchangeable and modular; common control low • Must have minimum frame-relay capability • But not paid for until required • Will move to a three-stage architecture: • Traditional TDM bus for regular traffic • SONET bus: 4 or 5 Gbps drop and insert traffic • Cell relay bus (ATM) for high bandwidth • Common control will handle all three types

  13. The Multiservice DLC • Will become a network cloud that includes multiple topologies and protocols • Incorporation of frame relay and ATM figures prominently: OC-12 and OC-48 • Because the high bandwidth infrastructure for this does not exist in many places and may never will, wireless local loop services will be required

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