1. 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

2. 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

3. 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.

4. History of Subscriber Carriers

5. 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 )

6. 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.

7. 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.

8. 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.

9. DLC

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

11. 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.

12. 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.

13. DLC architecture

14. 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.

15. 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.

16. 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.

17. 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.

18. 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

19. References 1. http://www.dsl-list.com/DLC.htm

20. THANK YOU