Data transmission is the way or method to transfer any kind of information from one space to another. Data transmission is the way or method to transfer any kind of information from one space to another.

Transmission Media for Transmission Media for NetworksNetworks

Communication Channel

A channel is used to convey an information signal, for example a digital bit stream, from one or several senders (or transmitters) to one or several receivers.

A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second

Data transmission is the way or method to transfer any kind of information from one space to another.

Data transmission is the way or method to transfer any kind of information from one space to another.

Criteria for Media Evaluation

Bandwidth –data carrying capacity of a channel (High bandwidth- broadband, low bandwidth-narrowband)

Bit rate - expresses the data rate capacity of a networking system

Delay - The time required to send a signal across a network

Cost of medium material

Ease of installation and Maintenance

Data transmission is the way or method to transfer any kind of information from one space to another.

Categories of Transmission Media

A. Guided media

and

B. Unguided Media

Data transmission is the way or method to transfer any kind of information from one space to another.

A. Guided Media

Guided Transmission Media uses a "cabling" system that guides the data signals along a specific path.

The data signals are bound by the "cabling" system. Guided Media is also known as Bound Media.

There 4 basic types of Guided Media:

1. Open Wire 2. Twisted Pair

3. Coaxial Cable 4. Optical Fiber

Data transmission is the way or method to transfer any kind of information from one space to another.

Bandwidth comparison

Cable Type Bandwidth

Open Cable 0 - 5 MHz

Twisted Pair 0 - 100 MHz

Coaxial Cable 0 - 600 MHz

Optical Fiber 0 - 1 GHz

Data transmission is the way or method to transfer any kind of information from one space to another.

1. Open Wire

Data transmission is the way or method to transfer any kind of information from one space to another.

2. Twisted Pair

Data transmission is the way or method to transfer any kind of information from one space to another.

Each pair would consist of a wire used for the +ve data signal and a wire used for the -ve data signal.

Any noise that appears on 1 wire of the pair would occur on the other wire. Because the wires are opposite polarities, they are 180 degrees out of phase.

Numbers of pairs are bundled together. Twisting

decreases crosstalk. When the noise appears on both wires, it cancels or nulls itself out at the receiving end.

It is mainly used for telephone system and for subscriber’s loop like LAN.

The degree of reduction in noise interference is determined specifically by the number of turns per foot. Increasing the number of turns per foot reduces the noise interference.

Data transmission is the way or method to transfer any kind of information from one space to another.

Shielded Twisted Pair

Data transmission is the way or method to transfer any kind of information from one space to another.

Advantages:

1. Easy to string 2. Cheap

Disadvantages: Subject to interference.

In comparison to others ( Coax & optical fiber) twisted pair is limited in bandwidth, distance and data rate Like if used for digital systems it requires repeater after every 2-3 Kms.

It’s low bandwidth capabilities make it unsuitable for broadband applications.

Susceptible to noise weather shielded and unshielded

UTP and STP cables

Data transmission is the way or method to transfer any kind of information from one space to another.

Categories of Twisted-Pair Cables

Category 1: The basic cabling used for voice

Category 2: Suitable for voice and data up to 4 Mbps

Category 3: Suitable for data up to 10 Mbps

Category 4: Suitable for data up to 16 Mbps

Category 5: Suitable for data up to 100 Mbps

Data transmission is the way or method to transfer any kind of information from one space to another.

3. Coaxial Cable

Coaxial Cable consists of 2 conductors. The inner conductor is held inside an insulator with the other conductor woven around it providing a shield.

An insulating protective coating called a jacket covers the outer conductor.

The outer shield protects the inner conductor from outside electrical signals.

The distance between the outer conductor (shield) and inner conductor plus the type of material used for insulating the inner conductor determine the cable properties or impedance.

Coaxial cable is a copper-cored cable surrounded by a heavy shielding and is used to connect computers in a network. Widely used for cable TV connections.

Can be used for broadband transmission.

Outer conductor shields the inner conductor from picking up stray signal from the air.

Offers High bandwidth of upto 400MBPS.

Repeater is used to regenerate the weakened signals.

Category Impedance Use

RG-59RG-59 75 Cable TV

RG-58RG-58 50 Thin Ethernet

RG-11RG-11 50 Thick Ethernet

Data transmission is the way or method to transfer any kind of information from one space to another.

(a.)

Data transmission is the way or method to transfer any kind of information from one space to another.

Advantages: Not susceptible to interference

Transmits faster

With FDM it can carry 10,000 voice channels

Disadvantages:

Heavy & bulky

Needs booster over distance. Like repeaters or amplifiers are needed every few Kms.

Data transmission is the way or method to transfer any kind of information from one space to another.

4. Optical Fiber Optical Fiber consists of thin glass fibers that can carry

information at frequencies in the visible light spectrum and beyond.

The typical optical fiber consists of a very narrow strand of glass called the Core.

Around the Core is a concentric layer of glass called the Cladding.

A typical Core diameter is 62.5 microns (1 micron = 10-6 meters). Typically Cladding has a diameter of 125 microns.

Covering the cladding is a protective coating consisting of plastic, it is called the Jacket.

Data transmission is the way or method to transfer any kind of information from one space to another.

FO Cable may have 1 to

over 1000 fibers

Optical fibers use light to send information through the optical medium.

It uses the principal of total internal reflection.

Modulated light transmissions are used to transmit the signal.

Data transmission is the way or method to transfer any kind of information from one space to another.

Principle of working

Characteristic of Fiber Optics is Refraction.

The core refracts the light and guides the light along its path.

The cladding reflects any light back into the core and stops light from escaping through it - it bounds the media!

Data transmission is the way or method to transfer any kind of information from one space to another.

Advantages:

Noise immunity: RFI and EMI immune (RFI - Radio Frequency Interference, EMI –Electro Magnetic Interference)

Security: cannot tap into cable. Hence guarantees secure transmission.

Large Capacity due to BW (bandwidth) , can handle several channels in parallel.

No corrosion

Longer distances than copper wire

Smaller and lighter than copper wire

Faster transmission rate

Highly suitable for harsh industrial environments.

Data transmission is the way or method to transfer any kind of information from one space to another.

Disadvantages :

Physical vibration will show up as signal noise.

Limited physical arc of cable. Bend it too much & it will break.

Difficult to split, Highly fragile.

Copper:

It has low resistance to electrical current and signal travels farther.

guided medium bandwidth - depends on the thickness of the wire and the

distance traveled. interference - susceptible to electromagnetic waves

generated by neighboring wires. Two main types - twisted pair and coaxial cable (coax)

Data transmission is the way or method to transfer any kind of information from one space to another.

The Advantages of Fiber over Copper:

Interference - does not cause interference; and is not susceptible to interference.

Bandwidth - handles much higher bandwidth than copper

Low attenuation - requires fewer repeaters and amplifiers (every 30 Km vs. 5Km)

Immune to power surges, failures, and other electromagnetic interference

thin and lightweight

don’t leak light; tough to tap (secure)

Data transmission is the way or method to transfer any kind of information from one space to another.

B. Unguided Media Unguided media transport electromagnetic waves Unguided media transport electromagnetic waves

without using a physical conductor. This type of without using a physical conductor. This type of communication is often referred to as wireless communication is often referred to as wireless communication.communication.

Radio WavesMicrowavesInfrared

Wireless transmission waves

Also called wireless communication. It transports electromagnetic Waves without using a physical conductor. Signals are broadcastthrough the air ( in some cases water). There are available to anyone who can receive them.

Radio Frequency Allocation – the selection of the electromagneticspectrum defined as radio communication is divided into 8 ranges,called bands, each regulated by government. These bands arerated from very low frequency (VLF) to very high frequency (EHF)

VLF and HF – this propagate very close to the surface.MF and HF – upper layers and then reflect back to the earthVHF and UHF – transmitted using line of sight – EHF and SHF – space propagation.

Frequency Bands

BandBand RangeRangePropagatioPropagatio

nnApplicationApplication

VLFVLF 3–30 KHz Ground Long-range radio navigation

LFLF 30–300 KHz GroundRadio beacons and

navigational locators

MFMF 300 KHz–3 MHz Sky AM radio

HF HF 3–30 MHz SkyCitizens band (CB),

ship/aircraft communication

VHF VHF 30–300 MHzSky and

line-of-sightVHF TV, FM radio

UHF UHF 300 MHz–3 GHzLine-of-

sightUHF TV, cellular phones,

paging, satellite

SHF SHF 3–30 GHzLine-of-

sightSatellite communication

EHFEHF 30–300 GHzLine-of-

sightLong-range radio navigation

Propagation methods

Data transmission is the way or method to transfer any kind of information from one space to another.

•Radio waves are used for multicast communications, such as radio and television, and paging systems.

• They can penetrate through walls.

•Highly regulated.

•Use omni directional antennas

Radio Waves

Omnidirectional antenna

Data transmission is the way or method to transfer any kind of information from one space to another.

•Microwaves are used for unicast communication such as cellular telephones, satellite networks,and wireless LANs.

•Higher frequency ranges cannot penetrate walls.

•Use directional antennas - point to point line of sight communications

Micro Waves

Unidirectional antennas

Terrestrial MicrowaveMicrowaves do not follow the curvature of earth

Line-of-Sight transmission

Height allows the signal to travel farther

Two frequencies for two way communication

Repeater is used to increase the distance Hop-by-Hop

Satellite Communication

Data transmission is the way or method to transfer any kind of information from one space to another.

Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.

Used in TV remotes.

Will not penetrate walls.

Infrared Waves

Data transmission is the way or method to transfer any kind of information from one space to another.

Used for line of sight transmission.

Faster than microwaves.

Adversely affected by weather.

Laser Transmission

Wireless MediaVery useful in difficult terrain where cable laying is not possible.

Provides mobility to communication nodes.

Right of way and cable laying costs can be reduced.

Susceptible to rain, atmospheric variations and Objects in transmission path.

Are subject to a lot more errors than guided media channels..

Wireless MediaIndoor : 10 – 50m : BlueTooth, WLAN

Short range Outdoor : 50 – 200m: WLAN

Mid Range Outdoor : 200m – 5 Km : GSM, CDMA, WLAN Point-to-Point, Wi-Max

Long Range Outdoor : 5 Km – 100 Km : Microwave Point-to-Point

Long Distance Communication : Across Continents : Satellite Communication