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INSTITUTE OF TECHNOLOGY AND MARINE ENGINEERING
KOLKATA, INDIA

RUPAYAN AICH

COMP. SC. & ENGG.

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Using Telephone and Cable Networks for Data Transmission

TELEPHONE NETWORK
Telephone networks use circuit switching. The telephone network had its beginnings in the late 1800s. The entire network, which is referred to as the plain old telephone system (POTS), was originally an analog system using analog signals to transmit voice.
Topics discussed in this section:
Major Components
LATAs
Signaling
Services Provided by Telephone Networks



MAJOR COMPONENTS
Major components of Telephone network: Local loops, trunk, and switching office.

Different levels of switching offices: end offices, tandem offices, and regional offices.







Local loop: Twisted pair cable that connects the subscriber telephone to the nearest end office or local central office. It has a bandwidth of 4000 Hz for voice. The first three digits of local telephone number define the office, and the next four digits define the local loop number.
Trunks: Transmission media that handle communication between offices. It handles hundreds or thousands of connections through multiplexing. Transmission is usually through optical fibers or satellite links.
Switching office: To avoid having a permanent physical page link between any two subscribers, switches are located here. Switch connects several local loops or trunks and allows different subscribers to connect.


LATAs
LATA (Local access transport areas)
Services offered by the common carriers (telephone companies) inside a LATA are called intra-LATA services. The carrier that handles these services is called a local exchange carrier (LEC).
Intra-LATA services are provided by local exchange carriers. Since 1996, there are two types of LECs: incumbent local exchange carriers (ILEC) and competitive local exchange carriers (CLEC)
ILEC would provide main services and owns the local loop. CLEC would provide other services such as mobile telephone service, toll calls inside a LATA, ¦
Communication inside a LATA is handled by end switches and tandem switches. A call that can be completed by using only end offices is called toll-free. A call that has to go through a tandem office (intra-LATA toll office) is charged.



Point of presences (POPs)
Intra-LATA services or inter-LATA services can be provided by several LECs or IXCs sequentially. These carries interact with one another via a switching office called a POP.

SIGNALING
The tasks of data transfer and signaling are separated in modern telephone networks: data transfer is done by one network, signaling by another.



DIAL-UP MODEMS
Traditional telephone lines can carry frequencies between 300 and 3300 Hz, giving them a bandwidth of 3000 Hz. All this range is used for transmitting voice, where a great deal of interference and distortion can be accepted without loss of intelligibility.

DIGITAL SUBSCRIBER LINE
After traditional modems reached their peak data rate, telephone companies developed another technology, DSL, to provide higher-speed access to the Internet. Digital subscriber line (DSL) technology is one of the most promising for supporting high-speed digital communication over the existing local loops.
Topics discussed in this section:
ADSL, ADSL Lite, HDSL, SDSL, VDSL
ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses.
The existing local loops can handle bandwidths up to 1.1 MHz.
ADSL is an adaptive technology.The system uses a data rate
based on the condition of the local loop line.

CABLE TV NETWORKS
The cable TV network started as a video service provider, but it has moved to the business of Internet access. In this section, we discuss cable TV networks per se; in Section 9.5 we discuss how this network can be used to provide high-speed access to the Internet.
Topics discussed in this section:
Traditional Cable Networks
Hybrid Fiber-Coaxial (HFC) Network



CABLE TV FOR DATA TRANSFER
Cable companies are now competing with telephone companies for the residential customer who wants high-speed data transfer. In this section, we briefly discuss this technology.
Topics discussed in this section:
Bandwidth, Sharing, CM and CMTS,
Data Transmission Schemes: DOCSIS

CONCLUSION
Networks exists so that data may be sent from one place to another -the basic concept of data communications.
It helps in business decision making .
It increases the demand in cellular telephonic services.
It increases the development in educational system.
Its demand in Medical , Aerospace & Aeronautical Engineering.