Transmission Media

Transmission Media

Magnetic Media Magnetic tape Floppy Disks Hard Disk

Magnetic Tape •Magnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic.

Features Of Magnetic Media Refers to the storage of data on a magnetized medium. Magnetic storage media can be classified as either sequential access memory or random access memory Information is accessed using one or more read/write heads. As of 2008, common uses of magnetic storage media are for computer data mass storage on hard disks and the recording of analog audio and video works on analog tape.

Contd.. Magnetic storage is also widely used in some specific applications, such as bank checks and credit/debit cards A new type of magnetic storage, called MRAM, is being produced that stores data in magnetic bits based on the GMR effect.

Benefits More Effective Bandwidth. Bandwidth is higher than ATM. For e.g. 8mm video tape -7Gb.A box (50*50*50) Can hold 1000 of tapes. So total capacity7000Gb.It can be delivered in US say 24 hrs. The effective bandwidth is 56,000 gigabits(648Gbps)which is 10000 times better than high speed ATM(622Bps). More cost Effective.0000000..0 Not affected by natural calamities

Coaxial cable Structure

Coaxial cable Characteristics Better Shielding than Twisted pair Excellent noise immunity High bandwidth. Depends upon cable length.cables(1Km)-1-2 Gbps.Longer cables low bandwidth. Longer coaxial cables require Amplifiers. Types of Coaxial cable: Base band Coaxial cable Broadband Coaxial cable

Coaxial cable Types 1)Baseband coaxial cable Used for digital transmission(50 Ohms) 2) Broadband Coaxial cable Analog Signal transmission Broadband in telephone network means anything wider than 4Khz.In computer Networking, “Broadband Cable” means any cable network used for analog transmission. Broadband networks use Standard cable Television technology. The cables can be used up to 300 MHz and can run 100km The digital signal on the Analog Network can be transmitted by using the interface consisting of electronics to convert the outgoing bit stream to the analog signal and the incoming analog signal to a bit stream.

Contd… Broadband systems are divided into multiple channels, frequently the 6 MHz channels used for television broadcasting. Each channel can be used for analog television,CD Quality audio, or digital bit stream They cover a large area so they require amplifiers to strengthen the signal. Amplifiers can transmit the signal in one direction, so to overcome the problem,2 types of Broadband Systems have been developed Dual cable Systems Single cable Systems

Applications of coaxial cable used to connect home video equipment Used in ham radio setups They used to be common for implementing computer networks, in particular Ethernet. Broadband Internet access. Long distance coaxial cable is used to connect radio networks and television networks. Micro coaxial cables are used in a range of consumer devices, military equipment, and also in ultra-sound scanning equipment

Advantages Broadband system (frequency range) Greater channel capacity Greater bandwidth Lower error rates Greater spacing between amplifiers

Disadvantages Leakage of Signal Ingress Egress

Problems with the deployment architecture Bidirectional upgrade required More expensive than Twisted Pair cable Less Flexible than UTP High installation costsSusceptible to damage from lightning strikes. Broadband cant be used effectively for digital transmission .

Wireless Transmission Wireless communication is the transfer of information over a distance without the use of electrical conductors or wire. The information is transmitted by the means of the waves such as radio, Infra Red waves etc. It can also facilitate the creation of networks in special situations, such as terrain that is unfriendly to ground cables. Political organizations determine which sections of the spectrum of light are allotted to which wireless transmission purposes.

Infrared & Millimeter Waves Used for short range communication Remote controls used in TV, VCRs & stereos use these waves Features: Cheap Easy to build Directional They do not pass through the solid objects They do not pass through the walls More secured than Radio waves in case of Eavesdropping

Contd.. No government License is required Applications Indoor wireless LANS as they cant be used for Outdoors.

Light wave Transmission Lasers are used for this communication Connect the LANS in the 2 buildings via Lasers mounted on the rooftops Laser Beams is unidirectional so every building requires laser and the photo detector. Advantages Very high Bandwidth Low cost Easy to install No requirement of FCC license.

Contd.. Disadvantage Very narrow beam Lenses are required to defocus the beam Heat from the sun causes the convection current and diverts the beam.

ISDN The regular phone line, which is used at home and offices is an analogue phone line. ISDN network is a digital communication system that is capable of producing the maximum transmission speed of 1.4Mbps. 128Kbps speed is however more common in the digital technology. It's a international communication standard for sending data, voice, video over regular digital telephone lines with data transfer rate of 64Kbps.

Contd.. ISDN uses UTP (unshielded twisted pair cable) for transmission. Types Basic Rate Interface (BRI) – It consists of two 64Kbps 2B-channels and one 16 Kbps D-channel for transmitting control information.(2B+D) Primary Rate Interface (PRI) -- It consists of 23 B-channels and one Dchannel (for U.S.) or 30 B-channels and one D-channel (for Europe/India).

Contd.. Types on the basis of Transmission Narrowband/ Base band ISDN Broadband ISDN To access the B channel, it is necessary to subscribe the ISDN phone line. Customers are also required to have some special ISDN devices, which are known as terminal adapters, which are used to communication with the telephone company switch or other ISDN devices.

ISDN Services Voice Video Data Intercom Caller ID connecting the telephone to a computer Call Forwarding & Call Conferencing Remote electricity meter Reading Alarms

How ISDN works? In an analog network the regular telephone line is used as a single transmission channel that can carry voice, video, data one at a time. With ISDN With ISDN, this same pair telephone line is logically divided into the multiple channels. A typical line has two channels.

Contd.. The first type of channel is called B channel. This channel can carry about 64Kbps of data. Typical ISDN line has 2 B channels. One channel is used for voice and other channel is used for data communication. This data/voice transmission process occurs on the regular one pair copper wire. The second type of channel is used for link and call setup. This channel is known as D channel or Delta Channel. The third channel has only 16Kbps of bandwidth.

ISDN System Architecture

A set of are defined in the ISDN Standard CCITT defined four reference points (Fig. 241): U reference point = connection between the ISDN exchange and NT1, T reference point = connector on NT1 to the customer, S reference point = interface between the ISDN PBX and the ISDN terminal, R reference point = the connection between the terminal adapter and non-ISDN terminal.

BRI & PRI

Perspective on N-ISDN N-ISDN was an attempt to replace the analog telephone system with a digital one. -ISDN basic rate is too low so for home as for business today. N-ISDN may be partly saved, but by an unexpected application: Internet access Various companies now sell ISDN adapters that combine the 2B + D channels into a single 144 kbps digital channel . So the people can access Internet over a 144 kbps digital link, instead of a 28.8 kbps analog modem link and for affordable price that may be a niche for N-ISDN for the next few years.

Broadband ISDN Logical extension of the end-to-end circuit switched data service, ISDN. The technology for B-ISDN was going to be Asynchronous Transfer Mode (ATM), which was intended to carry both synchronous voice and asynchronous data services on the same transport.

ATM The technology for B-ISDN was going to be Asynchronous Transfer Mode (ATM), which was intended to carry both synchronous voice and asynchronous data services on the same transport. Transports real-time video and audio as well as image files, text and email. ATM, as a connection-oriented technology, establishes a virtual circuit between the two endpoints before the actual data exchange begins.

Contd.. ATM is a cell relay, packet switching protocol which provides data link layer services that run over Layer 1 links. ATM exposes properties from both circuit- and small packet switched networking, making it suitable for wide area data networking as well as realtime media transport. It is a core protocol used in the SONET/SDH backbone of the public switched telephone network.