DIGITAL LOOP CARRIER (DLC) A PROJECT REPORT ON DIGITAL LOOP CARRIER (DLC) SUBMITTED DURING THE VOCATIONAL TRAINING AT BSNL DURG Under the Guidance of SHRI A.B. SINGH SUBMITTED BY: Ashish Tiwari Chanchal Komal Tiwari Parul Gupta Rajat Chandra

Contents INTRODUCTION HISTORY OF SUBSCRIBER CARRIERS REASONS FOR USING DLC CONFIGURATION MORE ABOUT DLC EARLY MOTIVATIONS FOR DLC TECHNOLOGY TYPES OF DLC UNIVERSAL DLC INTEGRATED DLC DLC ARCHITECTURE ADVANTAGES OF DLC DISADVANTAGES OF DLC FUTURE DIRECTIONS CONCLUSION ACRONYM GUIDE REFERENCES

INTRODUCTION A digital loop carrier (DLC) is a system which uses digital transmission to extend the range of the local loop farther than would be possible using only twisted pair copper wires. A DLC digitizes and multiplexes the individual signals carried by the local loops onto a single data stream on the DLC segment.

History of Subscriber Carriers

Reasons for using DLC Subscriber Loop Carrier systems address a number of problems:- Electrical constraints on long loops Insufficient available cable pairs Cable route congestion (inability to add cable due to lack of space, particularly in urban street, bridge and building conduit) Construction challenges (in areas of difficult terrain) when limited cable pairs are already available Expenses due to cable cost and the associated labor intensive installation work (especially to solve the specific problems listed above )

Configuration DLC remote terminals are installed in new neighborhoods or buildings as a means of reducing the labor and complexity of installing individual local loops from the customer to the central office (CO). DLC remote terminals are typically stored in Serving Area Interfaces- metal cabinets alongside or near roadways that overlie communications rights- of -ways. With the growth in popularity of digital subscriber line (DSL) and the benefits provided by shorter metallic loops used with DLC systems, digital loop carriers are sometimes integrated with digital subscriber line access multiplexers (DSLAM). Fiber in the loop systems (FITL) accomplishes the same two primary functions DLC was intended for: pair gain and the elimination of electrical constraints due to long metallic loops.

More about DLC Typically up to 24 analog voice calls are combined into a single signal and transmitted over a single copper T-carrier system or E-carrier system. In a home, business, or other installations using DLC, the analog phone lines of individual users are connected to a local DLC box which then converts the analog signals into digital and combines them into one signal that is sent to the phone company’s CO on the single line. At the CO, the combined signal is separated back to the original signals.

Early motivations for DLC technology Loop carrier systems were ordained to solve two problems: To reduce copper cable pair requirements And to overcome electrical constraints on long loops.

DLC

Types of DLC There are two types of DLC:- UNIVERSAL DIGITAL LOOP CARRIER (UDLC) INTEGRATED DIGITAL LOOP CARRIER (IDLC)

UDLC The UDLC is a system that consists of RDTs and central office terminals (COTs). Optical systems such as synchronous optical network (SONET) can transfer signals transparently through the COT to the RDT. The RDT provides an interface between the digital transmission line and the customer’s access lines.

IDLC Integrated digital loop carrier (IDLC) is a digital line interface that has been re-engineered to integrate within a switch and shares the internal bus structure of the switch. This function is called an integrated digital terminal (IDT). Using IDT, the switch can directly communicate with a remote digital terminal (RDT) that is closer to the end customer using an efficient multi channel communication line.

DLC architecture

Advantages of DLC DLC systems also offer the ability to extend the range of access lines from the central office to the end customer as RDT effectively operates as a repeater. The DLC system offers improved efficiency through the use of existing distribution cabling systems. The cost effective transmission The ability to rapidly add, delete, or change customer services without having to dispatch an installation technician.

Disadvantages of DLC Unfortunately, DLC systems are not transparent to other systems such as DSL systems. Although it is possible to install digital subscriber line network equipment (co-locate) along with RDT equipment, the RDT equipment housings and power supplies were not originally designed to hold additional equipment.

Future Directions To understand the future of the local loop, we have to examine the elements that will drive its evolution. Competition: From the telecoms using HFC. By utilizing cable modems, HFC networks can deliver 6-8 Mbps. Internet: DSL gives telecos the opportunity to become Internet Service Providers (ISPs), which can provide another economic monthly subscription. Bandwidth-intensive services: Services to the home for telecommuters, video-on demand, videoconferencing, and high-definition television (HDTV) requires an architecture to support such demands. Infrastructure: Infrastructure must be able to support increasing bandwidth as well as cost-effectively support existing narrowband deployment. Migration: Migration must be simple and the economics of migration must be solid.

Conclusion DLC systems also offer the ability to extend the range of access lines from the central office to the end customer as the RDT effectively operates as a repeater. The DLC system offers improved efficiency through the use of existing distribution cabling systems. The cost effective transmission and the ability to rapidly add, delete, or change customer services without having to dispatch an installation technician.

Acronym Guide ATM - Asynchronous Transfer Mode DDS - Digital Data Services DLC - Digital Loop Carrier HDSL - High bit-rate Digital Subscriber Line HDTV - High-Definition Television HFC - Hybrid Fibre/Coax ISDN - Integrated Synchronous Digital Network ISP - Internet Service Providers LAN - Local Area Network NGDLC - Next-Generation Digital Loop Carrier POTS - Plain Old Telephone Service SONET - Synchronous Optical Network

References 1. http://www.dsl-list.com/DLC.htm 2. http://www.iec.org/online/tutorials/DLC/ 3. http://www.legerity.com/coreapp.php?cid=3 4. http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214331,00.html 5. http://www.transwitch.com/solutions/nextgenDLC/index.jsp

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