Isdn

INTEGRATED SERVICE DIGITAL NETWORK

New Technology Familiarization (ISDN)

INTEGRATED SERVICE DIGITAL NETWORK A RECENT development in the Indian telecommunication network is the introduction of Integrated Services Digital Network (ISDN) in all the places. ISDN is a network that provides end-to-end digital connectivity to support a wide range of services including voice and non voice services. Users can have access using a limited set of standard multipurpose customer interface. To start with, the BSNL has introduced only narrow band ISDN leaving the broad band ISDN and Universal access ISDN. As the Internet has come already into India the introduction of ISDN is only appropriate, to serve the high profile customers in an economical way. Of course, the customers in India have been made to wait till 1996, while around 3.5. million customers world over are already enjoying ISDN service, for the main reason that digitalisation of the present telecom network combined with CCS No. 7 signalling which are prerequisite for ISDN, could be completed only in 1995. Now in almost all the major cities BSNL has commissioned new technology switches with ISDN capabilities thanks to the large scale import of equipment from advanced countries like Germany, France and Japan. ISDN has emerged as a powerful tool , by providing different services such as telephone, fax, data communication, image and picture transmission, to respond quickly to the needs and expectations of the common subscriber and the business community. A single pair of copper premises of the customer can establish at least two simultaneous independent calls either of voice or data.

ISDN CHANNELS – BASIC RATE ACCESS (BRA) Basic Rate Access (2 B + D) Single Pair of Wires BRBRAITT / MAR – 2004

B1= 64 Kbps B2= 64 Kbps D = 16 Kbps

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New Technology Familiarization (ISDN)

1.

B Channel : There are 2 B – Channels each operate at 64 kbps. Carries information for user services including Voice, Audio, Video and digital data. Total B Channel bandwidth is 128 Kbps (64 + 64).

2.

D Channel : Operate at 16 Kbps, carries signals between the User and the network. This may also carry user data packets at lower speeds up to 16 kbps.

ISDN Channels – Primary Rate Access (PRA) 1.

B Channel : There are 30 B – Channels each @ 64 kbps.

2.

D Channel : One D chl – 64 kbps for signalling.

PRIMARY RATE ACCESS (30 B + D) Two Pair of PCM

30 B Channels at 64 Kbps each 1 D at 64 Kbps

30 Channels of 64 Kbps each for speech and data 1 Channel of 64 Kbps for signaling Customer Premises Equipments : (a)

Network Terminal (NT 1) : This equipment connects the 2 wire ISDN line (U interface) from exchange for BRA – ISDN at one side and provides a standard 4 wire interface (S interface), on the other side Various Customer Premises Equipment (CPEs) can be connected on the S interface.

(b)

Terminal Adapters (TA) : A Terminal Adapter connects the S interface to one side and one or more of the following on the other side. Analog Phones, G3 FAX, answering machine, Cordless Phone etc.

Terminal types of V.24 OR (RS 232C), X-25, V.35 etc. BRBRAITT / MAR – 2004

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New Technology Familiarization (ISDN)

(c)

S – Bus & S Bus Connectors.

(d)

PC 486 AT / PC advanced or with windows.

(e)

ddon Cards for PC for direct ISDN & FTP operation.

ISDN CUSTOMER PREMISES

℡ Terminal connector

Network Terminal 1 “S” bus

NT 1

2 W cable Local N/W

“S” bus connector

Feature phone

PC

Power pack

ISDN Customer Premises

(f)

ISDN Feature Phone : The ISDN feature phone is connected at the S interface and provides voice communication with number of supplementary services.

(g)

Desk top Video Conferencing Equipments (PC based) to work at 128 Kbps. The equipment consists of one or two PC cards to be installed in the slots of IBM PC 486 or above. The cards provide interface to S Bus. A Camera, earphone, milk or telephone is supplied which will be connected to suitable connectors at one of the PCB in the tower. Suitable software is provided to work on video conferencing.

Bearer Services : A bearer service defines the transmission characteristics of a network, which consists of exchanges and transmission equipment. These services BRBRAITT / MAR – 2004

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New Technology Familiarization (ISDN) are available to the terminals at NT 1 connected to the ISDN for transfer of information. 64 Kbps Data. Packet Switching Circuit Switching. 64 Kbps Voice @ 8 KHz. Tele Services – This is obtained by connecting suitable CPE like. Telephony FAX Video Imaging]Graphics Supplementary Service : In a addition to services like speech, audio, packet, fax and tele-services, there are number of other features for calls within ISDN. These features are called supplementary services. All the following services are available to ISDN subscriber absolutely free of charge. Multiple subscriber Number : (MSN) Allows to assign multiple ISDN numbers to a single ISDN access. The calling user can select a specific terminal connected on the passive bus of the called user by dialing the specific terminal number. The MSN number is to be defined in the ISDN node.

Normally three

Directory Numbers are given free of cost. Sub Addressing ; (SUB) Allows the user to assign individual terminal addressing beyond the scope of ISDN numbering plan. The terminal sub address is to be defined by the user in the individual terminal connected on the possive bus. Calling Line Identification Presentation : (CLIP) Called ISDN subscriber gets a display of caller number Calling Line Identification Restriction (CLIR):

BRBRAITT / MAR – 2004

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New Technology Familiarization (ISDN) Allows called user restriction to prevent the presentation of calling line identify. In override mode the called user can receive CLI even if CLIR is activated. Terminal Portability (TP) : Allows the user to move his terminal from one socket to another within one given access during the active phase of the call. Call Hold : (CH) Allows the user to intercept temporarily the existing communication and then subsequently if desired retrieve that call from CH, or originate a new call or establish connection on an incoming waiting call. Closed User Group : (CUG) Allows the user to form groups for establishing calls among the predefined group of subs as members. A CUG member may belong to several CUGs. Charging Related Service : Advice of Charge : (AOC) Allows a user to receive charge information for a call during the communication or at the end of the call. Additional information transfer service : User to User signaling : (UUS) is a supplementary service which allows an ISDN user to send/receive a limited amount of information to / form another ISDN User over signaling channel. On the internal wiring in the subscribers’ premises, up to 8 ISDN terminals such as video telephones, group 4 fax machines, ISDN telephone, IBS PC, video conferencing equipment, can be directly connected.

The existing

terminal equipment such as analogue phone, push button/rotary, G3 fax (TE 2) modems, answering machines, cordless phones can be connected using a terminal adaptor. The narrow band ISDN which is also called as Basic Rate Access (BRA) has two ‘B’ channels and one “D” channel (2 B + D) for carrying voice/data in B channels and control signals in the form of messages in bit rate in D channel. Primary Rates Access (PRA), has 30 B channels and 1 D channel (30 B + D). The new technology exchanges can provide both 2 B + D and 30 B + D.

BRBRAITT / MAR – 2004

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New Technology Familiarization (ISDN) The rate of transmission on the B channel is 64 kbps for voice/data. By putting 2 B channels and 1 D channel, the rate of which is 16 kbps, the capacity of the line at the customer end may be made powerful enough to carry 144 kbps which is faster then the normal 2.4 kbps or 9.6 kbps rates prevalent in the data circuit. Data transmission is approximately 9 times faster, in ISDN lines using data terminals, than the I-NET connected terminals. The charging on ISDN line is only on duration basis compared to data transmission charged on both quantum (per kilo segment of data) and duration basis. ISDN will hence be economical for data transmission. Ordinary video conferencing between desktop monitors at two distant ends is possible with the picture of calling party and that of the called party appearing simultaneously on the screens of both monitors. Here the transfer rate of bits is 128 kbps, that is, both the B channels are used for a call. High quality video conferencing on dial up basis between any two ISDN customers at 384 kbps using three ISDN lines, is also possible. In addition to video image of participants, still pictures of documents and drawings can also be transmitted. Video images can be sent or received on auxiliary equipment such as VCR. Using a control panel the video camera can be zoomed at the local end as well as at remote end.

H0 – ch (384 kbps = 64 kbps x 6

ISDN Exchange

384 kbps unrestricted

ISDN Exchange

TE

Teleconferencing terminal

TE

S/T

Common channel signaling network

S/T

Teleconferencing terminal

D-ch

Interactive services, conversation (video), message (data) and retrieval (audio), of high quality are aimed at in the PRA – ISDN services which offer BRBRAITT / MAR – 2004

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New Technology Familiarization (ISDN) 30 channels at the disposal of subscribers. Distribution of High Definition Television

(HDTV),

high

speed

communication

and

multimedia

communications are other features of the primary rate access ISDN. Emerging Metropolitan Area Networks (MAN) such as Fiber Distributed Data Interface (FDDI) are possible as the transmission media gets upgraded to high quality optical fibre using digital solutions such as synchronous digital hierarchy (SDH). •

Calling line identification presentation (CLIP) : On an incoming call, the calling subscriber’s number is displayed on the ISDN phone before the call is answered. When engaged, if a second call arrives, it is displayed giving a choice to the subscriber to answer it.

•

Calling line identification restriction (CLIR) : By this, the calling subscriber can prevent the presentation of his number to the called subscriber.

•

Advice of charge (AOC) : Continuous display and updating of the call units to be charged for the call is available on the screen of a digital phone.

•

Multiple subscriber number :

Up to 8 terminals can be

connected on the subscriber premises wiring with separate numbers with 3 mandatory Directory numbers. •

Call forwarding service (CF) : Calls to a subscriber can be forwarded to another number under different conditions – busy, on answer and unconditional.

•

Terminal portability (TP): During conversation one terminal can be removed from the socket in one place and connected to another socket in a different place, holding the call.

•

Call hold (CH) : During conversation it is possible to hold at least two more calls. Toggling between calls is also allowed.

BRBRAITT / MAR – 2004

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New Technology Familiarization (ISDN) •

Closed user group (CUG) : Companies with offices in different cities can have their ISDN number in a closed user group and work like PABX.

The customer premises equipments are standardised by the Telecom Engineering Centre under the BSNL and approved for use by customers. BSNL will provide only a network terminal (NT 1) at the subscriber’s premises. Other equipments are to be bought/provided by the subscriber. The subscribers presently owning separate lines one each for telephone, fax, data transmission and telex, may now dispense with these by converting only one of the lines into ISDN and connecting all their terminals enjoying two simultaneous calls. BSNL has completed the network synchronization with CCITT No. 7 signaling to enable national connectivity. The Videsh Sanchar Nigam Limited will enable international connectivity. Now, X-ray image of the patients can be sent over telephone lines from remote hospital to specialty medical centres for expert diagnosis and on-line advice. For banks and industry, transmission of information of facsimile at a high rate of 64 kbps is advantageous. This is 9 times the highest speed possible now. Application of ISDN in video conferencing has the potential to reduce traveling by business executives as they can ‘inspect’ a remote site work from their chamber.

BRBRAITT / MAR – 2004

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