331: STUDY DATA COMMUNICATIONS AND NETWORKS. 1. Discuss computer networks (5 hrs) 2. Discuss data communications (15 hrs)

Data Communication Network

331: STUDY DATA COMMUNICATIONS AND NETWORKS

331: STUDY DATA COMMUNICATIONS AND NETWORKS

1. Discuss computer networks (5 hrs) 2. Discuss data communications (15 hrs)

331.2: Discuss Data Communications PERFORMANCE STANDARD

◦ Given a network system, identify and illustrate the different data communications components clearly

Objectives:◦ Define elements of a communication system◦ Define data communications◦ Discuss various types of transmission media and

their characteristics◦ Discuss encoding of information tor transmission◦ Discuss types of signal & their characteristics◦ Relate data capacity of a channel and bandwidth◦ Classify media based on bandwidth◦ Discuss channel organization

SKILL AREA 331.2.3

Discuss various types of transmission media

and their characteristics

Types of transmission media twisted pair – telephone cable coaxial cable –Thick black cable used for

higher bandwidth communications than twisted pair (i.e. Optus cable)

fibre optic – data transferred through pulses of light. Extremely fast.

Non cable methods such as satellite, microwave, wireless and Bluetooth

Types of transmission media

Twisted Pair Cable

Twisted pair cable

Twisted pair Cable

Twisted pair cable application Most common medium Telephone network

◦ Between house and local exchange (subscriber loop)

Within buildings◦ To private branch exchange (PBX)

For local area networks (LAN)◦ 10Mbps or 100Mbps

Twisted pair Cable

Twisted pair cable pro and contraAdvantages Cheap Easy to work with

Disadvantages Low data rate Short range

Twisted pair Cable

Twisted pair Transmission Characteristics Analog

◦ Amplifiers every 5km to 6km Digital

◦ Use either analog or digital signals◦ repeater every 2km or 3km

Limited distance Limited bandwidth (1MHz) Limited data rate (100MHz) Susceptible to interference and noise

Twisted pair Cable

Twisted pair (UTP and STP) Unshielded Twisted Pair (UTP)

◦ Ordinary telephone wire◦ Cheapest◦ Easiest to install◦ Suffers from external EM interference

Shielded Twisted Pair (STP)◦ Metal braid or sheathing that reduces interference◦ More expensive◦ Harder to handle (thick, heavy)

Twisted pair Cable

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.

CAT cable characteristic

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

Connector The most common UTP connector is RJ45 (RJ

stands for Registered Jack).

Coaxial Cable Coaxial Cable (or coax) 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

Coaxial Cable

Coaxial Cable Used for cable television, LANs, telephony Has an inner conductor surrounded by a

braided mesh Both conductors share a common center

axial, hence the term “co-axial”

Coaxial Cable

Coax Layers

copper or aluminum conductor

insulating material

shield(braided wire)

outer jacket(polyethylene)

Coaxial Cable

Coaxial Cable

Coaxial Cable Applications: Most versatile medium Television distribution

◦ Ariel to TV◦ Cable TV

Long distance telephone transmission◦ Can carry 10,000 voice calls simultaneously◦ Being replaced by fiber optic

Short distance computer systems links Local area networks

Coaxial Cable

Coaxial Cable - Transmission Characteristics Analog

◦ Amplifiers every few km◦ Closer if higher frequency◦ Up to 500MHz

Digital◦ Repeater every 1km◦ Closer for higher data rates

Fiber Optic Cable

Fiber Optic Cable Relatively new transmission medium used

by telephone companies in place of long-distance trunk lines

Also used by private companies in implementing local data communications networks

Require a light source with injection laser diode (ILD) or light-emitting diodes (LED)

Fiber Optic Cable consists of three concentric sections

plastic jacket glass or plasticcladding fiber core

Fiber Optic Cable

Fiber Optic Cable 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).

Fiber Optic Cable

Optical Fiber

multimode step-index fiber◦ the reflective walls of the fiber move the light

pulses to the receiver multimode graded-index fiber

◦ acts to refract the light toward the center of the fiber by variations in the density

single mode fiber◦ the light is guided down the center of an

extremely narrow core

Fiber Optic Types

Fiber Optic Signals

fiber optic multimodestep-index

fiber optic multimodegraded-index

fiber optic single mode

greater capacity (bandwidth of up to 2 Gbps)

smaller size and lighter weight lower attenuation immunity to environmental interference highly secure due to tap difficulty and lack

of signal radiation

Fiber Optic Advantages

expensive over short distance requires highly skilled installers adding additional nodes is difficult

Fiber Optic Disadvantages

Unguided media, or wireless communication, transport electromagnetic waves without using a physical conductor.

Instead the signals are broadcast though air or water, and thus are available to anyone who has a device capable of receiving them.

The section of the electromagnetic spectrum defined as radio communication is divided into eight ranges, called bands.

Unguided media

Electrical conductor (or system of..) used to radiate electromagnetic energy or collect electromagnetic energy

Transmission◦ Radio frequency energy from transmitter◦ Converted to electromagnetic energy◦ By antenna◦ Radiated into surrounding environment

Reception◦ Electromagnetic energy impinging on antenna◦ Converted to radio frequency electrical energy◦ Fed to receiver

Same antenna often used for both

Antennas

transmission and reception are achieved by means of an antenna

directional◦ transmitting antenna puts out focused beam◦ transmitter and receiver must be aligned

omnidirectional◦ signal spreads out in all directions◦ can be received by many antennas

Wireless (Unguided Media) Transmission

Directional Antennas provide great efficiency of power transmission because the power can be focused into a narrow beam directed toward the station of interest.

Directional Antenna

Omnidirectional Antenna is widely used for radio broadcasting antennas, in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, wireless computer networks, cordless phones, GPS

Omnidirectional Antenna

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

Propagation of Radio Waves

Ground propagation: radio waves travel through the lowest portion of the atmosphere, hugging the earth. These low-frequency signals emanate in all directions from the transmitting antenna and follow the curvature of the planet. The distance depends on the power in the signal.

In Sky propagation, higher-frequency radio waves radiate upward into the ionosphere where they are reflected back to earth. This type of transmission allows for greater distances with lower power output.

In Line-of-Sight Propagation, very high frequency signals are transmitted in straight lines directly from antenna to antenna.

Propagation of Radio Waves

BandsBand Range Propagation Application

VLF 3–30 KHz Ground Long-range radio navigation

LF 30–300 KHz GroundRadio beacons and

navigational locators

MF 300 KHz–3 MHz Sky AM radio

HF 3–30 MHz SkyCitizens band (CB),

ship/aircraft communication

VHF 30–300 MHzSky and

line-of-sightVHF TV, FM radio

UHF 300 MHz–3 GHz Line-of-sightUHF TV, cellular phones,

paging, satellite

SHF 3–30 GHz Line-of-sight Satellite communication

EHF 30–300 GHz Line-of-sight Long-range radio navigation

Satellite is relay station Satellite receives on one frequency,

amplifies or repeats signal and transmits on another frequency

Requires geo-stationary orbit◦ Height of 35,784km

Television Long distance telephone Private business networks

Satellite Microwave

Satellite Point to Point Link

Satellite Broadcast Link

QUESTION?