Introduction• OCB (OCB stands for Organe Comade type B) is a digital switching system which

supports a variety of communication needs like basic telephony, ISDN etc. • This system has been developed by CIT ALCATEL of France and therefore has

many similarities to its predecessor E-108B (also known as OCB-181 in France).• It is digital switching with signal 'T' stage switch. A maximum of 2048 PCM's can

be connected.• It support both analog and digital subscriber.• It has double remoting facilities. Subscriber access unit can be placed at a remote

place and connected to the main exchange through PCM links. Further, line concentrator can be placed at remote location and connected to the CNCL or CSND through PCMs.

• All the control units are implemented on the same type of hardware.This is called a station.

Facilities of OCB• A line can be made only incoming or outgoing.• Immediate Hot Line Facility:- The subscriber is another predetermined

subscriber on lifting the handset without dialing any number.• Delay Hot Line Facility:- When subscriber lift the handset, dial tone is provided

he can dial any number. If he doesn't dial any number, within a predetermined time, he is connected to predetermined number.

• Abbreviated Dialing:- The subscriber can recorded a short code and its corresponding full number in the memory. Later he dial this number, he has to only dial short code.

• Call Forwarding:- When activated, incoming calls to the subscriber get transferred to the number mentioned by the subscriber while activating the facilities.

• Conference Between Four Subscribers:- Two subscriber while LAN conversation can include two more subscribers by pressing button and dialing their numbers.

• Call Waiting Indication:- When a subscriber is engaged in conversation and if he get an incoming call, an indication is given in the form of tone.

Routers• A router is a networking device, commonly specialized hardware that forwards data

packets between computer networks. • When a data packet comes in one of the lines, the router reads the address

information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.

• Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node.

• The most familiar type of routers are home and small office routers that simply pass data, such as web pages, email, IM, and videos between the home computers and the Internet.

Applications• Each network interface uses the specialized computer software to enable data

packets to be forwarded from one protocol transmission system to another.

 • Routers may also be used to connect two or more logical groups of computer

devices known as subnets, each with a different sub-network address.

 • Routers may provide connectivity within enterprises, between enterprises and the

Internet, or between internet service providers' (ISPs) networks.

 • The largest routers (such as the Cisco CRS-1 or Juniper T1600) interconnect the

various ISPs, or may be used in large enterprise networks.

• Smaller routers usually provide connectivity for typical home and office networks.

How a Router works?When you send e-mail to a friend on the other side of the country, how does the message know to end up on your friend's computer, rather than on one of the millions of other computers in the world? Much of the work to get a message from one computer to another is done by routers, because they're the crucial devices that let messages flow between networks, rather than within networks.

Broadband Routers• A broadband router utilizes the Ethernet standard for wired connections. • Traditional broadband routers required Ethernet cables be run between the router,

the broadband modem, and each computer on the home network. • Newer broadband routers also incorporate wireless networking capability utilizing

the Wi-Fi standards.• Static and dynamic routes are stored in the Routing Information Base (RIB). The

control-plane logic then strips the RIB from non essential directives and builds a Forwarding Information Base (FIB) to be used by the forwarding-plane.

• A typical home or small office router showing the ADSL telephone line and Ethernet network cable connections.

B.T.S (Base Transceiver System)Structure of WiMAX BTS

• A machine called Chechus has the following part:-• Power CardTrip1• Trip 2• GAP• G.P.S• GAP• PMP2• PMP1• GAP•  • Gap is provided to add some submachine or other part of Chechus for the improvement in WiMAX.•  • G.P.S. works to trace the signal. Till the GPS is locked, the Google can't browse anything inspite the

Google page remain open.•  • Power Card is used as switch that means if one trip is switched OFF due to some error/Problem then

Trip 2 or second MCB will worked automatically. It doesn't mean that only one switch will turn ON i.e., both should be turned ON.

 

• Serially, Trip 1 or Trip 2 (or MCBs) will placed at the top of the WiMAXChechus (or system) then an Adapter will placed at the bottom of the MCBs.

• Adapter can transmit 12v DC and can recieve 48v.

 • After Adapter PMP1 and PMP2 will placed.• PMP1 is just below the PMP2 and it can cover only one sectori.e., 120 degree

ideally.

 • PMP2 having two sector. Each sector can covers 120 degree ideally/ Standard value

i.e., PMP2 can covers 240 degree (120 degree + 120 degree).

 • PMP1 is just below the PMP2.

 • 3COM switch placed below the PMP1.• There are two 3 COM switch is used one for transmission and other is used for

receiving.

 

Optical Fiber Communication• Optical Fiber used in long distance communication are covered with various coating like

Outer Jacket, Inner Jacket and buffer.• This coating prevents the interfernce of external noise or external signal into the fiber.

Due to this, noise is minimized and the chances of break of fiber is reduced. Example: • In 7 buffer of Optical fiber, 28 fibers are present. 4 fiber in each buffer. In which one

fiber is empty called Dummy, which is used for shape and strength.• Each buffer have three colors i.e., Blue, Orange, Green and No color.• In 24 fiber cable these colors are repeatable due to the presence of 6 buffer.• The colors of 12 Fiber cables in 1 buffer are Blue, Orange, Green, Brown, Grey, White,

Red, Black, Yellow, Purple, Pink and No color.• The colors of 12 Fiber cables in 2 buffer are blue and no color. • Optical Fiber Cables are of two type: Silica Fiber and G Mercury.• In BSNL, Silica Fiber is used.• In BSNL, only Single Mode fibers are used.• In TV cables,Multi Mode cables are used.• Single Mode Step Index Fibers are used in BSNL.• Core Diameter of the optical fiber should be minimum.

• Cladding of Optical Fiber Cables is approximately 125 * 10-6m.• Acceptance cone should be greater.• Radiation Cone should be smaller.• There are various Diodes used in Optical Fiber Communications, named as: LASER

Diode, LED, and Avalanche Photo Diode.• Laser Diodes are used in Long distance communicationan sends in monochromatic

and sharp manner.• Laser diodes changes electrical energy into optical energy.• LED is used for short distance and sends spreadly.• Avalanche Photo Diode is used in Radiation Receiving in optics fiber.• APD (Avalanche Photo Diode) changes Optical Energy into the Electrical energy.• PCM and MUX (TDM) technique is used in this communication. • Single mode fiber is used to send signal to long distance.• Multimode fiber is used to local or short distance due to presence of loss in it.• Pigtail is one side connector and other side fiber.• P.C. (Patch Chords) have fiber at both the sides i.e., it can be connect from both sides.• Patch cord or Pigtail is used for small distance communication like in B.S.N.L

exchange. • Plastic Paint in Optical fibers is used to avoid breaking.• Alcohal is used to clean the fiber.

Tools:• Striper is used to Peel the optical Fiber.• Fiber Cleaver is used to cut the Fiber.• Nonic Tools:- It is used to peel out the Pigtail.• Fusion Splicer:- It is used t joint the two Optical Fiber.• If ‘s’ alphabet is used in model number of Fusion Splicer, it indicated that the fiber is single mode fiber.• If ‘r’ alphabet is used in model number of Fusion Splicer, it indicated that the fiber is Ribbon fiber.• Critical angle is such that the refractive angle is vary such that the refracted ray become moving to the

normal line.• Critical angle of cone is the angle at which wave can’t be accepted.• Splicing Machine: used to joint the two optical fiber. • 4 PCM mixed and form P Q R S T• 1Q = 4P• 4Q = 1R• 4R = 1S• 4S = 1T

 

Meters: • Power Meter: used to measure the transmit power.• LASER source (stabilized LASER sources)• Optical Time Domain Reflectometer (O.T.D.R): It is used as the detector which is detect the fault of the

optical fiber.• Visible Light Field Detector

Patch Cords• A Patch Cord or Patch cable or Patch lead is an electrical or optical cable used to

connect one electronics or optical devices to another for signal routing. • As length of patch cord increases the cable are usually thicker and/or made with

more shielding to prevent signal losses (or attenuation) and the introduction of unwanted radio frequency and hum (Electromagnetic Interfernce).

• Patch cords are often made of coaxial cable with is the signal carried through the shielding core.

• Patch Cords includes microphone cable, head phone, Extension cable, XLR Connector, Tiny telephone connector, RCA connector and 1/4 TS connector cable (as well as modular Ethernet cable) and thicker, horse like cord (snake cable) used to carry video and amplified signal.

Pigtail• A fiber Pigtail is a single short usually unbuffered, optical fiber that has an optical

connector preinstalled on one end and a length of emphasized fiber at the other end. • Pigtails have female or male connectors. • Female connectors could be mounted in a patch panel to allow them to be connected

end point or other fiber rum with patch fiber. • Male connectors that can plug directly into an optical transceiver.

Telecommunication• Telecommunication is communication at a distance by technological means,

particularly through electrical signals or electromagnetic waves.• Early means of communicating over a distance included visual signals, such as

beacons, smoke signals, semaphore telegraphs, signal flags and optical heliographs. • Modern technologies for long distance communication usually involve electrical

and electromagnetic technologies, such as telegraph, telephone and tele-printer, networks, radio, microwave transmission, fibre optics and communication satellites.

GSM Architecture

• The figure below depicts only the basic elements of the network architecture.• All the BTS of one region is connected to one BSC.• All the BSC of one region is connected to one MSC.• Each MSC is fed by VLR.• Location Update is the most important part in the mobile networking area.• As the location of mobile changes, MSC comes to know as the location will updated

in it contineously and due to this reason, battery is consumed.

Setup a call:• When someone call to a number, the signal reach to BTS by antenna and then it

send the signal to the BSC from where that number is registered.• BSC sends the signal to corresponding MSC and it locate the current location of

that number.• By using gateway MSC, that MSC will connected to the cureent location's MSC and

the call will continue on that number.• The current location of that number is catch by VLR where the location update each

and every second.• Location is updated sector by sector in BTS, BTS by BTS in MSC, MSC by MSC

in VLR.

Setup a call:• When someone call to a number, the signal reach to BTS by antenna and then it send the

signal to the BSC from where that number is registered.• BSC sends the signal to corresponding MSC and it locate the current location of that

number.• By using gateway MSC, that MSC will connected to the cureent location's MSC and the

call will continue on that number.• The current location of that number is catch by VLR where the location update each and

every second.• Location is updated sector by sector in BTS, BTS by BTS in MSC, MSC by MSC in VLR.• Let us take an exammple to understand the whole procedure of call setup:• Let us consider Ram call to Shayam. Shyam has number, registered from Lucknow and

Ram has number, registered from Mainpuri.• During Call, a signal send to Mainpui's BTS under which Ram is stand in any sector.• That BTS send a signal to its corresponding BSC which communicate with the BSC of

Lucknow.• The BSC communicate with MSC and locate the current position of Shyam's number.• Let us assume Shyam is in Dehli. Then, the MSC of Lucknoe will communicate with the

MSC of Dehli via gateway MSC.• Afetr his process, the call will connect to shyam.• during this process, BTS check either Ram is legal to call Shyamor not. If he isn't legal to

call shyam then the call will break and if he is leagal than process will continue as discussed above.

 GSM Roaming

• Concept of GSM Roaming is understood by using following examples:•  • When a SIM card purchase then a number is provided (Like for BSNL a number starts from 94).

Generally, this number is called Mobile number but technically it is called ISDN ID.• When a SIM purchase, some information will filled in a form which is an applicant personal detail, like

Name, Number, Address, Date of Birth etc.• That SIM is placed in a mobile and it catches signals but a call can’t be setup till that information will not

updated on the MSC.• The MSC is divided into sub parts from which two are important. One is HSL and other is VSL.• When the data are updated on the MSC by exchange then the signal catches and call will setup. Now it is

authorised number.• A call probably can be done in the same MSC or other and in same region or other.• When the call is done in same MSC or BTS then it take much less time to connect or procedure is done as

the role of MSC is not come into picture.• When the call is done in the same region of MSC but different BTS then the calling is easy but not so s in

the previous case because BTS is involved while MSC’s role is negligible.• When calling is done in different region of MSC then the word Roaming comes.• In Roaming region, the MSC takes the detail of the number from the home MSC of number and stored in

VLR.• When a call is coming to that number then all the detail, current location, tariff (if roaming tariff is present

then the roaming charges will excludes) are checked in VLR in MSC and it is connected.