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Transcript of TELEPHONE NETWORK
SUBMITTED TO- PROF. SHIKHA NEMA
MADE BY- PRIYANSHE YADAV(CSE)
SATYAM SONI (CSE)
INTRODUCTION OF TELEPHONE NETWORK
COMPONENTS OF TELEPHONE NETWORK
SIGNALING & SERVICES
DIGITAL SUBSCRIBER LINE-
CABLE TV NETWORK FOR DATA TRANSFER
Telephone network use circiut switching.
The telephone network had its beginnings in its late 1800s. The entire network was referred to as the PLAN OLD TELEPHONE SYSTEM(POTS). POTS was originally an analog system using analog signals to transmit voice.
The telephone network is made of three major components:
local loop is a twisted pair cable that connects the subscriber telephone to the nearest end offices or local offices.
The local loop, when used for used for voice, has a bandwidth of 4000 Hz.
The first three digits of local phone no. defines the office, and the next four digits defines the local loop number.
Trunks are transmission media that handle, the communication between offices.
A trunk normally handles hundreds of thousands of connections through multiplexing.
Transmission is usually throung optical fibers or satellite links.
The telephone company has switches located in a SWITCHING OFFICES.
A switch connects several local loops or trunks & allows a connection between several different subscriobers.
After the divestiture of 1984, the United States was divided into more than 200 LOCAL-ACCESS TRANSPORT AREA(LATAs).
A LATA can be a small or large metropolitan area.
SWITCHING OFFICES IN A LATA
The services offered by the common carriers inside a LATAs are called intra-LATAs services.
In the beginning the voice transfer communication was performed by the human operator.
THE SIGNALING SYSTEM WAS REQUIRED TO PERFORM OTHER SUCH TASKS-
Providing dial tone, ring tone, & busy tone.
transferring telephone number between offices.
maintaining & monitoring the calls.
keeping billing information.
maintain the status of telephone network equipments.
providing other functions such as caller ID, voice mail, and so on.
In the beginning, the telephone companies provided their subscribers with analog services.
These services still continue today.
These services are further categorized, as shown in flow chart.
ANALOG SWITCHED SERVICES
This is the familiar dial-up service most often encountered when a home telephone is used.
The signal on a local loop is analog, and the bandthwidth is usually betwen 0 and 4000 Hz.
It provide cheaper service to their customers.
ANALOG LEASED SERVICES
An analog leased services offers customers the opportunity to lease a line, sometimes called a dedicated line, that is permanently connected to another customer.
No dialing is needed.
Recently telephone companies began offering digital services to their subscribers.
Digital services are less sensitive to analog services to noise and other forms of interferences.
DIGITAL SUBSCRIBER LINE
After traditional modems reached their data rate, telephone companies developed antoher technology, DSL, to provide higher-speed access to the internet.
DIGITAL SUBSCRIBER LINE(DSL) technology is one of the promising for supporting high-speed digital communcation over the existing local loops.
SET OF DIGITAL SUBSCRIBER LINE
The first technology in the set is ASYMMETRIC DSl (ADSL). ADSL, like a 56k modem provides higher speed(bit rate) in the downstream direction than in the upstream direction.
That is the reason it is called aymmetric.
ADSL is an asymmetric communication technology designed for residential users, it is not suitable for businesses.
The existing local loops can handle bandwidth up to 1.1 MHz.
ADSL is an adaptive tchnology. The system uses a data rate based on the condition of the loop line.
The high-speed-rate-digital subscriber line(HDSL) was designed as an alternative to the T-1 line(1.544 Mbps).
HDSL uses 2B1Q encoding, which is less susceptible to attenuation.
The SYMMETRIC DIGITAL SUBSCRIBER LINE(SDSL) is one twisted-pair version of HDSL.
It provides full duplex symmetric communication supporting up to 768 kbps in each direction.
SDSL can be considered an alternative to ADSL.
The Very-High-Bit-Rate digital subscriber line(VDSL), an alternative approach that is similar to ADSL, uses coaxial, or twisted-pair, or fiber-optics cable for short distances.
The modulating technique is DMT.
It provides a range of bit rates (25 to 55 Mbps) for upstream communication at distances of 3000 to 10,000 ft.
CABLE TV FOR DATA TRANSFER
Cable companies are now competing with telephone companies for the residantial customers who wants high-speed data transfer.
DSL technology provides high-data-rate connections for residential subscriber over the local loop.
DSL uses existing unshielded twisted-pair cable.