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 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 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)
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 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 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 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 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 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 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 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 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 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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