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TRANSMISSION MEDIA

& COMMUNICATION

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ZIRAMOPHI-'WANKAN' PRESENTS

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RICHARD&

HARRISON SIMON

DONE BY

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Transmission Media

Transmission media or communication channels of network meant that connecting cables or connecting media, The cables that connect two or more workstations are the communication channels. The transmission media are of mainly two types.

What do you mean by transmission media ?

Guided Media

Guided Media is that contain some conducting material to carry data or signal. Many types of cable and wires fall under this category. Each of them has its own characteristics like transmission speed, effects of noise.Guided media is also known as wired media. In this we will use wires to send our data from one place to other place.

Twisted Pair

Coaxial CableOptical Fiber

Microwave Transmission Radio waves Transmission

Satellite Transmission

Types of Guided Media

Twisted-pair cable

Twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together.Twisted-pair cable comes in two forms: unshielded and shieldedThe twisting helps to reduce the interference (noise) and crosstalk.

UTP and STP

Unshielded twisted pair cable and shielded twisted pair cable

Unshielded Twisted-pair (UTP) cable

Any medium can transmit only a fixed range of frequencies!UTP cable is the most common type of telecommunication medium in use today.

The range is suitable for transmitting both data and video.Advantages of UTP are its cost and ease of use. UTP is cheap, flexible, and easy to install.

The Electronic Industries Association (EIA) has developed standards to grade UTP.

1.Category 1. The basic twisted-pair cabling used in telephone systems. This level of quality is fine for voice but inadequate for data transmission.2.Category 2. This category is suitable for voice and data transmission of up to 2Mbps.3.Category 3.This category is suitable for data transmission of up to 10 Mbps. It is now the standard cable for most telephone systems.4.Category 4. This category is suitable for data transmission of up to 20 Mbps. 5.Category 5. This category is suitable for data transmission of up to 100 Mbps.

Categories of unshielded twisted-pair cables

Category Bandwidth Data Rate Digital/Analog Use

1 very low < 100 kbps Analog Telephone

2 < 2 MHz 2 Mbps Analog/digital T-1 lines

3 16 MHz 10 Mbps Digital LANs

4 20 MHz 20 Mbps Digital LANs

5 100 MHz 100 Mbps Digital LANs

6 (draft) 200 MHz 200 Mbps Digital LANs

7 (draft) 600 MHz 600 Mbps Digital LANs

UTP connectors

The most common UTP connector is RJ45 (RJ stands for Registered Jack).

Shielded Twisted (STP) Cable

STP cable has a metal foil or braided-mesh covering that enhances each pair of insulated conductors.

The metal casing prevents the penetration of electromagnetic noise.

Materials and manufacturing requirements make STP more expensive than UTP but less susceptible to noise.

Twisted-pair cables are used in telephones lines to provide voice and data channels.

The DSL lines that are used by the telephone companies to provide high data rate connections also use the high-bandwidth capability of unshielded twisted-pair cables.

Local area networks, such as 10Base-T and 100Base-T, also used UTP cables.

Applications

Coaxial Cable (or coax)This type of cable consist of a solid wire

core surrounded by one or more foil or wire shields, each separated by some kind of plastic insulators.

Inner core carries the signal, and the shield provides the ground.

Coaxial cable carries signals of higher frequency ranges than twisted-pair cable.

Coaxial Cable standards: RG-8, RG-9, RG-11 are used in thick Ethernet RG-58 Used in thin Ethernet RG-59 Used for TV

Types of coaxial cables

Thicknet : this form of coaxial cables is thinnet. The thicknet coaxial cable segments (while joining nodes of a network) can be up to 500 meters long. Thinnet : this form of coaxial cable is thinner and it can have maximum segment length of 185 meters that is using this cables, nodes having maximum distance of 185 meters can be joined.

Figure 7.7 Coaxial cable

Table 7.2 Categories of coaxial cables

CategoryImpedanc

eUse

RG-59 75 W Cable TV

RG-58 50 WThin

Ethernet

RG-11 50 WThick

Ethernet

BNC Connectors

Figure 7.9 Coaxial cable performance

Metal cables transmit signals in the form of electric current.

Optical fiber is made of glass or plastic and transmits signals in the form of light.

Light, a form of electromagnetic energy, travels at 300,000 Kilometers/second ( 186,000 miles/second), in a vacuum.

The speed of the light depends on the density of the medium through which it is traveling ( the higher density, the slower the speed).

Optical Fiber

Fiber construction

Types of Optical Fiber There are two basic types of fiber:

multimode fiber and single-mode fiber.

Multimode fiber is best designed for short transmission distances, and is suited for use in LAN systems and video surveillance. 

Single-mode fiber is best designed for longer transmission distances, making it suitable for long-distance telephony and multichannel television broadcast systems.

Propagation Modes (Types of Optical Fiber )

Current technology supports two modes for propagating light along optical channels, each requiring fiber with different physical characteristics: Multimode

and Single Mode.

Multimode, in turn, can be implemented in two forms: step-index or graded index.

Multimode: In this case multiple beams from a light source move through the core in different paths.

In multimode step-index fiber, the density of the core remains constant from the center to the edges. A beam of light moves through this constant density in a straight line until it reaches the interface of the core and cladding. At the interface there is an abrupt change to a lower density that alters the angle of the beam’s motion.

In a multimode graded-index fiber the density is highest at the center of the core and decreases gradually to its lowest at the edge.

Propagation Modes

Single mode uses step-index fiber and a highly focused source of light that limits beams to a small range of angles, all close to the horizontal.

Fiber SizesOptical fibers are

defined by the ratio of the diameter of their core to the diameter of their cladding, both expressed in microns (micrometers)

Type Core Cladding

Mode

50/125

50 125Multimode,

graded-index

62.5/125 62.5 125

Multimode, graded-

index

100/125

100 125Multimode,

graded-index

7/125 7 125

Single-mode

Light sources for optical fibers

The purpose of fiber-optic cable is to contain and direct a beam of light from source to target.

The sending device must be equipped with a light source and the receiving device with photosensitive cell (called a photodiode) capable of translating the received light into an electrical signal.

The light source can be either a light-emitting diode (LED) or an injection laser diode.

Fiber-optic cable connectors

The subscriber channel (SC) connector is used in cable TV. It uses a push/pull locking system. The straight-tip (ST) connector is used for connecting cable to networking devices. MT-RJ is a new connector with the same size as RJ45.

Advantages of Optical Fiber

The major advantages offered by fiber-optic cable over twisted-pair and coaxial cable are noise resistance, less signal attenuation, and higher bandwidth.

Noise Resistance: Because fiber-optic transmission uses light rather than electricity, noise is not a factor. External light, the only possible interference, is blocked from the channel by the outer jacket.

Less signal attenuationFiber-optic transmission distance is significantly

greater than that of other guided media. A signal can run for miles without requiring regeneration.

Higher bandwidthCurrently, data rates and bandwidth utilization over

fiber-optic cable are limited not by the medium but by the signal generation and reception technology available.

Advantages of Optical Fiber

The main disadvantages of fiber optics are cost, installation/maintenance, and fragility.

Cost. Fiber-optic cable is expensive. Also, a laser light source can cost thousands of dollars, compared to hundreds of dollars for electrical signal generators.

Installation/maintenanceFragility. Glass fiber is more easily broken than

wire, making it less useful for applications where hardware portability is required.

Disadvantages of Optical Fiber

Radio waves Transmission

•The Radio waves have frequencies between 3khz and1Ghz•Radio waves are Omni direction•Radio waves can penetrate buildings easily, so that are widely use for communication both indoors outdoors.•They also absorbed by rains•At high frequency, radio wave tends to travel in straight line and bounces off the obstacles.

Radio technology considers the earth as surrounded by two layers of atmosphere: the troposphere and the ionosphere.

The troposphere is the portion of the atmosphere extending outward approximately 30 miles from the earth's surface.

The troposphere contains what we generally think of as air. Clouds, wind, temperature variations, and weather in general occur in the troposphere.

The ionosphere is the layer of the atmosphere above the troposphere but below space.

Propagation of Radio Waves

Micro waves Transmission

•Micro waves electromagnetic waves having frequency between 1 GHZ and 300 GHZ. •There are two types of micro waves data communication system : terrestrial and satellite•Micro waves are widely used for one to one communication between sender and receiver, cellular phone, satellite networks and in wireless LANs.

Unguided Media

It does not contain the signal in some physical conductor or metal. Rather, it transport electromagnetic signal through air. It is also known as wireless media. Because in this we are not using any king of cable.

Infrared Waves Electromagnetic waves having frequencies from 300 GHz to 400 THz are called IR waves or Infrared waves. IR waves are used for short range communication and use line of sigh propagation.

Infrared waves cannot pass through solid objects, like walls and be easil contained in a room. They are cheap, easy to build and do not require any government license to use them.

IR waves offer very bandwidth for use.

Laser Transmission This type of transmission use thin laser to transfer data up to few kilometers. Laser beams are unidirectional, therefore this type of transmission system use line of sight propagation. In such a transmission system, a photo detector and laser is set on both sender and receiver side. Such a system offer very high band width at a very low cost. Other disadvantage is that on hot sunny days these waves are affected by hot turbulent air and miss the detector. The major problem in this transmission system is that laser beams cannot penetrate rain or thick fog.

Communication protocols

WHAT DO YOU

KNOW ABOUT

COMMUNICATION

PROTOCOLS

?

THIS MEANS THAT A FORMAL DESCRIPTION OF MESSAGE FORMATS AND THE RULES THAT TWO OR MORE MACHINES MUST FOLLOW TO EXCHANGE THOSE MESSAGES.

COMMUNICATION PROTOCOLS

CLASSIFICATION OF PROTOCOLS

COMMUNICATION PROTOCOLS

FTPHTTP TCP/IP SLIP/PPP

HTTP : (Hypertext Transfer Protocol) is the set of rules for transferring hypertext (i.e., text, graphics , image sound ,video etc.) on WWW (World Wide Web).

FTP : (File Transfer Protocol) is a standard for the exchange of files across internet.

TCP/IP : (Transmission Control Protocol / Internet protocol) is the base communication protocol of the internet. IP part of TCP/IP uses numeric IP addresses to join network segments and TCP part of TCP/IP provides reliable delivery of messages between networked computers

SLIP/PPP : SLIP (Serial Line Internet Protocol) is for delivering IP packets over dial-up lines; PPP (Point to Point Protocols) is for transmitting IP packets over serial lines

WIRELESS/MOBILE COMPUTING

Wireless communication : Wireless communication is simply data communication without the use of landlines.

Mobile computing : Mobile computing means that the computing device is not continuously connected to the base or central network.

WIRELESS VS MOBILE

EXAMPLES

Stationary computerNotebook is hotel

Wireless LANs in historic buildingsPersonal Digital Assistant (PDA)

Smart phones, pagers

Wireless/ Mobile Computing Technologies

3G and EDGEGSM

CDMAWLL SMS

EMAIL

VOICE MAIL CHAT

VIDEO CONFERENCI

NG

GSM : (Global System for Mobile) GSM uses narrow band TDMA (Time Division Multiple Access) , which allows 8 simultaneous calls on the same radio frequency. To connect to the specific service providers in these different countries , GSM uses simply switch subscriber identification module (SIM) cards.

CDMA : (Code- Division Multiple Access) uses a spread-spectrum technique where data is sent in small pieces over a number of discrete frequencies available for use. Each users signal is spread over the entire band width by unique spreading code. At the receiver and, the same unique code is used to recover the signal.

WLL : (Wireless in Local Loop) is a system that connects subscribers to the public switched telephone network (PSTN) using radio signals as a substitute for other connecting media.

3G and EDGE : (3rd Generation) and (Enhanced Data rates for Global Evolution) 3G mobile communications technology is a broadband, packet- based transmission of text, digitized voice, video and multimedia at data rates up to and possibly higher than 2 megabits per second (Mbps), offering a consistent set of services to mobile computer and phone users no matter where they are located in the world. EDGE is considered an intermediate step in the evolution of 3G WCDMA (Wideband CDMA ),although some carriers are expected to stop short of that final step

SMS : (Short Message Service) is the transmission of short text messages to and from a mobile phone , fax machine and/or IP address. Once a message is sent, it is received by Short Message Service Center (SMSC), which must then get it to the appropriate mobile device.

E-mail : (Electronic Mail) is sending and receiving messages by computer.

Voice Mail : The voice-mail refers to e-mail systems that supports audio.

CHAT : Online textual talk, in real time, is called chatting.

Video Conferencing : A two-way videophone conversation among multiple participants is called video conferencing.

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