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Wired –Wireless

And beyond

Chapter V

Fundamentals of telecommunications

Dr. Nazih Abdallah - Modern business computer1

Chapter objectives


Evolution from electricity to electronics

Understand telecommunication and its different technologies

From Telegraphy to telephony

Understand and recognize different telecommunication media.

From wired to wireless to T lines.

Understand frequency, wave, signal propagation and antennas.

Understand role of towers and satellites

Understand GPS technology and GPS applications.

Understand cellphone technology and applications.

Understand RADAR, infra-red and LASER and their applications

Electricity and electronics


Amber as source of ancient electricity: Greek and Arabs 1000 BC

1600: William Gilbert (father of electricity) discovered electrification of manysubstances. He coined the word “electricity”

referring to “ELECTROCUS” (Greek word for “amber”).

1873 Maxwell discovered that waves travel at speed of light and Hertz confirmed that and established the Hz as frequency unit.

1895 Marconi came up with the first radio and in 1904 John Flemmings invented the diode and Lee De Forest developed the triode and Electronics technology was born.

1960 (Atalla & Khang) invented the first silicon transistor a t Bell labs (MOS-transistor)

Transistor characteristics


Very little power consumption

Very small size.

Easiness of mass production

Availability of raw material at cheap cost.

Vacuum tube MOS semi-

conductor

Telegraphy


1825W. Sturgeon invented electromagnet

1838 SAM Morse invented the telegraph by sending electrical pulses to magnet and pull key to strike a code on a tape.

1881 US post started the service

1913: Western Union started multiplexing (8 different messages sent simultaneously over same wire)

1943 Western union merged with US post and used it in business and introduced Fac-simile service 1938 and the telex 1959

With Telex businesses could subscribe and dial each other.

1943 Congress funded first 40 miles telegraph linking Washington D.C and Baltimore.

Morse code comprises 2 symbols : a point and a dash (3points) that were like the binary enough to represent characters and symbols

Trained operators could handle 300 wpm

Light, wistles and mirrors can be used to send and receive Morse code. Still used in many areas.

Telephone


Alexander Graham Bell was the first to patent the telephone as “apparatus for

transmitting vocal or other sounds telegraphically” in 1876. His granted patent

number (#174,465).

Elisha Grey used liquid microphone to design a telephone in 1876 (five days after

the patent application of Alexander Bell). Many people believe that Bell had

stolen Grey’s invention and credit Grey for the invention of the telephone as a

complete device. Bell won the legal battle in the court.

Thomas Edison invented the carbon microphone in 1877. This Microphone used

the carbon particles as variable electronic resistance that amplifies electrical signal

and produces high quality voice and sounds. His invention was also disputed by

Emile Berliner who filed patent application in June 1877. But the patent rights

were awarded to Edison by a US court and later by a British court.

TELEPHONE STRUCTURE


Microphone

• Cable

Membrane

(Speaker)

Magnet

CARBON

PARTICULES

How it works


Transmitter converts audio signal into electrical signal and send electrical signal carrying speech modulation.

The microphone does the job by changing the resistance when you speak that result in changing the current function of your vocal audio waves

Receiver is needed to capture the electrical signals and convert them back into Audio signals and a speaker to amplify audio signal so that they will be heard by human.

The speaker on the other side using electromagnet that is magnetized by the received signal causes a thin membrane to resonate so that it reproduces the audio signals.

A transmission medium able to provide a safe pathway between sender and receiver.

Amplifiers interposed on the way to compensate the loss in decibel of the signal due to resistance encountered on the way.

Telephone evolution


High business demand in the early telephone market and the mounting pressure to develop the new technology to allow someone to speak with many other people resulted in inventing the telephone central exchange.

No direct communication was possible with the first manual exchange; instead operators answer calls and connect them to parties they ask to be connected with.

Modern automatic exchange enables everyone to directly connect to everyone else in dialing a number (automatic electronic switching work to accommodate the links all along the itinerary).

Automatic switching had deep impact on the job market; it resulted in the loss of millions of telephone operator jobs worldwide.

Because of these technological advances under business pressure, telephone technology found itself evolving toward networking technology very naturally.

Pros and Cons of telephone


The pros: Stable and reliable communication with no restraints of signal loss or influence of weather

conditions

Very well suitable to the military and business campuses.

High level of security (no wave interception to worry about especially in local and in-campus networks.

Cost is very reasonable.

No power connection required (very reliable during communication in case of prolo9nged power outage during natural disasters.

Easy networking

Easy control and updating

High voice quality

No special skills, no expertise and no training required to use it.

Telephone network extends all over the planet so you can reach anyone you want anytime you want.

The cons: Very limited mobility (fixed structure)

Difficult lay down of ground cable with digging required sometimes

Difficulties of maintenance and troubleshooting

Installation cost is high and sometimes prohibitive.

Wired media


This technology requires the transmitter and receiver to be connected to a pair of wires that form a closed electrical circuit.

Telegraphy and telephony were both wired technologies until recently telephone technology started using combined wired/wireless connection

Wired technology uses many different types of cables: Twisted pairs cable:

Consists of many pairs of twisted insulated wires protected by a hard insolation shield.

In order to make it possible to recognize the reference of subscriber, inner wires insolation is colored (each twisted pair has different color than the other).

This technology is subject to significant loss of signal strength if used in long distance communication. It is widely used for local short distance wired communication

Coaxial cable: Consists of an inner copper conductor insulated from surrounding metal braiding shield and both insulated from the outside with strong hard insulation. Inner and outer conductors travel parallel to each other that result in minimal decibel loss.

This technology is used when high quality connection is needed especially in connecting antennas, dishes, network connections, etc…

This cable is relatively very expensive. It is only used for special short distance connections.

Fiber-optic technology


Fiber optic cable: This technology is more and more used to replace copper

wire technology for wired connections. It consists of up to 800 fibers in one

shielded cable. A fiber is 1/8 mm diameter coated with an insulator its size

will be doubled to .25mm.

They are widely used in campuses, buildings, subdivisions, industrial plants, etc…

Used by cable TV and Internet providers to lay out their networks and distribute the

bulk of their services to community, subdivisions and big campuses

Provides the backbone for most business networks

Businesses usually lay much more than they need because difference in cost is not really

meaningful.

May be laid underwater in oceans to form transcontinental links.

How fiber-optic works?


Imagine a very thin very long (60 miles) pipe whose interior surface is

coated with a mirror.

If you flash a light at one end of the pipe it will travel amplified by

successive reflections and shine at the other end of the pipe (similar to

the LASAR principle).

If you install transmitter of signals at one end and a receiver to capture

the signal at the other end then each fiber will form a separate circuit

to accommodate one communication circuit or one subscriber.

Signal transmitted over the fibers are all transformed into digital (light

or no light) and that is how the transmission works.

Pros and cons of Fiber-optic


Pros:

Operates at very high speed and large capacity

Not affected by surrounding electromagnetic noise generated by motors, radio, other cables, etc…

Easier and cheaper maintenance.

Signals travel long distance without any need for amplifying and strengthening.

Cons:

They are very fragile and need to be protected from bending and passing over by transportation means, people and animals.

Need to be protected from water contamination.

Any wear or degradation in the fiber insulation will cause signal flare to affect other fibers causing quality deterioration.

High cost.

High capacity cables


T1 line: Reserved circuit that uses copper or fiber optic cables to operate over various networking

distances.

T1 data rate is 1.54 Mbps similar to symmetric DSL

Monthly Cost is about $1000 and more and mostly used by hotels, apartment buildings and subdivision and some business and college campuses where the cost can be justified.

T3 line: Use copper and fiber optic cables to operate as a reserved circuit equivalent to an

aggregation of 28 T1 lines.

Data rate is about 44.7 Mbps (1.54 x 28 = 44.7).

Monthly cost is about $3000 or more that’s why it is used as a backbone of large business network or the headquarters of big businesses and large size campuses and military bases.

Cables in general have some advantages over wireless: Compatibility with industry standards are very flexible to be tailored so that industry

standards are satisfied.

Capacity is usually higher

Reliability

Radio frequency (wave)


1- Introduction:

a. Radio telecommunications use waves propagating from antennas or dishes while

carrying the signals we need to transmit.

b. Radio signal travels at the speed of light in the vacuum (300,000 kilometers/second or

300,000,000 meters/second), that is a little more than one billion kilometers/hour.

2- Signal characteristics: Frequency and wavelength

a. Frequency = number of cycles/second or Hz/second

b. Wavelength is the distance covered by 1 cycle = 300/frequency in MHz (when the

frequency increases the wavelength decreases and when the frequency decreases the

wavelength increases accordingly).

3- Examples:

a. The wavelength of 3 MHz frequency = 300/3 = 100 meters

b. The wavelength of 30 MHz frequency = 300/30 = 10 meters

+ Analog - - - - - - - - - - - digital

Radio frequency (wave)


30 GHz – 300 GHz EHF Extremely High FrequencyMicrowave

3 GHz - 30 GHz SHF Super High Frequency mediumMicrowave

330 MHz – 3 GHz UHF Ultra High Frequency long oven Microwave

30 MHz – 330 MHz VHF Very High Frequency

3 MHz – 30 MHz HF High Frequency

300KHz – 3 MHz MF Medium Frequency

30 KHz – 300 KHz LF Low Frequency

10 KHz – 30 KHz VLF Very Low Frequency

NASA classification


Radio waves : 30 KHz- 3 GHz Height of Statue of liberty

diameter

Microwaves: 300 MHz- 300 GHz Baseball diameter

Infrared waves: 300 GHz- 400,000 GHz Human hair diameter

Visible light waves 400,000 GHz – 500,000 GHZ Red frequency

Visible light waves 500,000 GHz – 600,000 GHz yellow & green

Visible light waves 600,000 GHz – 750, 000 GHz Blue and Violet

Ultraviolet waves 750,000 GHz – 3,000,000 GHz Ultraviolet

X-Rays 100 million GHz – 1 billion GHz

Gamma rays Shortest wave with a frequency higher than X-Rays;

produced on earth by lightening, nuclear explosion and radiation

and produced in the space by the most energetic objects of the

universe.

Signal propagation


While wired telecommunication uses cables to carry signals , wireless telecommunication is based on the ability of electro-magnetic waves then known as (Hertz waves) to travel in the air at the speed of light by means of propagation from antennas.

Although German physicist Heinrich Hertz (1857-1894) is credited with building the first antenna in 1886-1888, the word “Antenna” (frequently known as aerial) is an Italian word that means pole in English was first used by Italian radio pioneer Guglielmo Marconi (1874-1937) who developed radio telecommunication into commercial and military success.

Marconi developed transmission and reception stations and antennas between 1895 and 1900 and his first antenna was a wire attached to the top of a 2.5 meters pole and running down the pole. His invention was credited by the United Kingdom with saving people who survived the Titanic disaster.

The first transatlantic transmission achieved by Marconi in 1901 used 500 feet (152.4 meters) wire as reception antenna.

How it works?


Sender (Transmitter): Signal charges cause the antenna to radiate

electromagnetic waves that travel at the speed of light in the vacuum (the

speed is slightly less in the open air due to the atmospheric conditions)

Receiver antenna intercepts radio waves (weakened by trip resistance),

sends them to electronic circuitry to get amplified and further converted

into their original type of signal at the output (audio, picture, etc…)

Types of antennas


Omnidirectional: propagate in all directions and used when there is no determined direction in sending and/or receiving signals and for medium and low frequency signal transmission.

Whip antenna: like car antenna

Turnstile antenna: high pole function as antenna,

Directional antennas: When the sending and receiving direction matter then the antenna should be directed following a given angle:

Dipole antenna first invented by Heinrich Hertz and consist of 2 rods like rabbit ears connected by a central wire. The rods are adjusted to be aligned with the signal angle.

Yagi antenna: consists of several bars fixed in parallel on an axis with a folded one reflector in the middle: this is a directional antenna used mainly in television receivers.

Parabolic or Dish antenna: a parabola like curved surface is an extremely directional antenna used mainly in microwave transmission because of its high directional selectivity.

Wireless line of sight


Goethe, (1749-1832) evoking wave propagation, said: “why is it possible to hear around corners, but not see around them?”

Although all radio signals travel at the speed of light, the frequency of the signal controls the way it is influenced by obstacles on the way.

Higher frequency are highly absorbed by obstacles and lower frequencies are more refracted, diffracted or reflected by obstacles or thru openings of buildings, cities and nature geographical landscape.

Compare the frequency to the drill bit: The faster it turns the sharper it perforates things. It can also be compared to the bullet’s velocity that enables bullet to travel a distance and hit a target.

Does that mean lower frequencies are better than higher frequencies for telecommunication purposes? The answer is “NO” because communication over long distance will add a lot of conflicting refraction, reflection and diffraction that weakens the signal and make the telecommunication impossible.

Relay – Towers


Towers as relays: To satisfy the line of sight condition necessary for radio telecommunication, service

providers use high towers to install the antennas.

Towers may be installed as free standing or on top of high rise building roofs in cities:

Since its inauguration in 1931 the Empire state building had a mast installed on its roof where (National Broadcasting Company (NBC) and several broadcasting stations installed their TV and FM broadcasting antennas’

Today the Empire State building is the hub of most radio FM and television stations and wireless Internet channels that operate in the New York area.

Satellites as relays: A telecommunication satellite works as a 300 miles high tower.

The round shape of the earth pose a natural obstacle between 2 distant locations

Telecommunication satellite orbits the earth at 200-300 miles altitude while covering a specific area.

When you look at the satellite from Earth you cannot see that it is traveling because it is matching the Earth movement for a complete cycle every 24 hours.

Other roles of relay


Radio signals traveling encounter resistance and lose a lot of

their strength. The loss is measured in decibels.

Relays intercept and retransmit signals

Relays are equipped with repeaters and transponders that

amplify signals before being retransmitted or redirected to their

destinations.

Satellites broadcast the coordinates of their location in orbit

(very important information that makes the GPS technology

possible.

Communication topology


Simplex topology:

This technology is based on the use of only one frequency channel to accommodate the

communication.

Only one station can transmit or broadcast

Examples are radio AM stations, radio FM stations, Television stations.

Half duplex technology also known as (HDX) technology

Use only one frequency channel to accommodate both transmitting and receiving of

communicating devices.

All stations can transmit and receive but not simultaneously (only one station can transmit at a

time)

Must push a button or a switch in order to switch from receiving to transmitting and vice versa.

Examples are: Citizens band (CB) radio, walkie-talkies and a lot of military radio equipment.

Walkie-talkie has low transmission power can reach a range up to one mile.

CB radios have more transmission power they can be used for a range up to 5 miles by

citizens, businesses, police and other agencies

This radio telecommunication system is not controlled by an technology protocol that enforces

transmission priorities

Transmitting station should end its transmission message by the word “over” or any other signal

that invites other stations to transmit if they wanted to.

High-frequency radio signals sent up to

30 miles through the air.

Microwave Communications

Microwave Communications

Line-of-sight communications

Microwave CommunicationsSatellite Transmission

Line-of-sight required

Networking Software

29

Full duplex


Full duplex technology also known as (FDX)

technology:

The full duplex technology basically uses 2 different frequency channels

to send and receive in each station.

Unlike half duplex that need switch from receive to send full duplex

technology allows each station to simultaneously transmit while listening

or receiving data without any switching need.

New time and frequency multiplexing technologies allow Full duplex to

use only one frequency that results in doubling the communication power

without any need for adding new towers and equipment.

Examples of FDX includes but not limited to:

Wired telephone networks.

Wireless phones known as cordless phones.

Internet telephony

Cellphone technology

GPS


The actual GPS we are using is a utility owned by the US government and operated by the government’s specialized agencies.

A Department of Defense project that started in 1973 and became fully operational for both military and civilian use in 1994.

The first satellite navigation system in the US was used in 1960 and consists of a constellation of 5 satellites.

The system in use now is the GPSIII. It is composed of 3 parts: The satellite constellation comprises 24 satellites each of them broadcasts the

coordinates of its own location in orbit.

GPS service receiving and computing devices: intercept satellite signals and compute their own location on earth by interpolation. Since we may have 24 points the center will indicate the actual location with great precision.

Control and correction service:

The computing accuracy is highly affected by the strength and accuracy of satellite signals

To maintain signal quality and correct any errors there are ground stations around the world (US, Europe, Japan, etc…) specialized in receiving signals, correcting them and retransmitting them to users

Other GPS systems


Russian GLONASS (Global Navigation Satellite System) started in 2007, also consists of 24 satellites able to provide full global coverage used by smart phones technology 4G and 5G (Sony and other phones).

China has its own GPS (Chinese satellite navigation system) known as the BeiDou system that consists now of 4 satellites with 6 more scheduled to be launched soon and the complete constellation of 35 satellites by 2020 will cover the globe.

Europe has its GPS known as the Galileo system which is advertised as a civilian-controlled alternative to the American GPS it consists of 4 satellites that will be tuned and joined by 22 other satellites by 2013.

How GPS work?


Each satellite continually send messages that have information about:

Coordinates of their location in orbit.

The time they sent the message

GPS receivers use that information in space navigation formula that enables them to compute their own position on earth with high accuracy.

More than 3 satellites must be visible in order to get accurate results.

GPS basic areas of use can be summarized by the abbreviation PNT

Positioning

Navigation

Timing

Cell Phone Technologies

A cellular network is a radio network in which a geographic area is divided into cells, with a transmission tower and station at the center of each cell, to support mobile communications.

Operational cellphone data Transmitter basically have to be operational with low transmission

power (between .5 watt and 3 watts)

Each cellular provider gets from FCC (Federal Communication

Committee) 832 different radio frequencies for a specific area of

served by that provider.

42 frequencies are used for control purposes.

Each communication call uses 2 frequencies;

Transmitting frequency

Receiving frequency

For an area of 7 cells, cellphone provider can accommodate up to 56

possible user communications simultaneously in each cell (56x7 =

392).

The low transmission powers it possible for non-adjacent cells to use

the same frequencies without any fear from interference between

conflicting calls using same frequencies.

Cellphone operational technology

Transmitter basically have to be operational with low transmission power (between .5 watt and 3 watts)

Each cellular provider gets from FCC (Federal Communication Committee) 832 different radio frequencies for a specific area of served by that provider.

42 frequencies are used for control purposes. Each communication call uses 2 frequencies;

Transmitting frequency Receiving frequency

For an area of 7 cells, cellphone provider can accommodate up to 56 possible user communications simultaneously in each cell (56x7 = 392).

The low transmission powers it possible for non-adjacent cells to use the same frequencies without any fear from interference between conflicting calls using same frequencies.

Operational technology There are two incompatible technologies to operate cellphone

networks;

Code Division multiple Access (CDMA):

Used in the USA, JAPAN and some companies in ASIA and South

America.

Phones use the same frequencies but are separated and

recognized by a different code used by the network to encode

each call.

Compare it to your possibility to recognize the guitar sound from

the drum sound from the piano sound in a music concert.

GSM/TDMA (Global System for Mobile communications/Time

Division Multiple Access).

European system used everywhere in the world even in the USA

and JAPAN. GSM is universal system.

The network assigns frequencies and time slots within each

second to each individual call (it tells your phone what frequencies

to use and what time to broadcast).

Has SIM (Subscriber Information Module) card or chip to record

information of each subscriber authorized to use to network.

CDMA/GSM GSM is global (when you travel you need only to buy

a new SIM and fit it into your cellphone and you are ready to go.

GSM/TDMA has a limited number of communication calls that may go simultaneously. This ceiling is much higher or inexistent in CDMA.

Although CDMA is the initial cellular technology, GSM is taking over because it is much more user friendly.

One disadvantage of GSM is when you are moving into neighboring cells where in TDMA/GSM you cannot use the same frequencies which may create a problem that would jeopardize efficient use of frequency spectrum.

With smartphones extensively using the web. TDMA/GSM has proven to be fit to handle data transmission and internet services better than CDMA.

RADAR

Principle: Radar technology is based on the principle of wave reflection when they hit metal target. It was developed by the German before WWII and adoption accelerated by Great Britain who thought that the Germans were developing (Death rays).

Radar system consists of

Transmitter equipped with directed dish or antenna that sends radar pulses in predefined direction

Receiver that gets weakened reflected signals, amplify them and display them on a monitor.

Signals captured help calculate: The range or distance of the target The altitude of the target The speed of the target if it is moving The direction of movement Some applications allow to analyze and make a judgment

about the shape and behavior of the shape

LASER Principle:

Simulated emission as theorized by Einstein in 1917 can be defined as the laser foundation.

Amplification and concentration of light emission power

Laser development requires the following necessary components:

Flash tube or flash lamp to provide

Gain medium that amplifies the light

A unit that supply energy to the gain medium

Feedback provided by a couple of mirrors installed on either end of the gain medium.

Topology of lasers: There are many different types of laser that use different material and therefore, different

technologies:

Crystal Laser: also called solid state laser generate lot of heat that was overcome by adding a diode with

thin disk may produce a Laser power up to one Kw.

Gas Laser: Gases were proven to amplify light and many gas Lasers were built widely used in optical

research and training labs.

Helium-neon Laser

Carbon dioxide Laser and Argon Laser

Semiconductor Laser: use electrically pumped diodes. Widely used in business equipment applications:

Laser printers

Pointers of different uses.

CD and DVD players and burners

Cutting industry

Chemical Laser: Very powerful Laser of high interest in military applications and combat Weaponry.

Hydrogen fluoride Laser

Deuterium fluoride laser

Fiber Laser: is a specific type of semiconductor laser with reduced thermal effect

Laser business apps Military: Many applications using powerful laser in

weaponry guiding and missile defense. Industry: many laser equipment sold for billions of

dollars that include and not limited to: Cutting and welding applications, components

measurement and marking. Products like printers, CD and DVD players, barcode

scanners, pointing devices and thermometers holograms Light shows. Medicine Laser Surgery and healing Eye treatment and eye laser surgery Cosmetics hair and skin treatment.

Many other activities use Lase applications mainly in forensics and many research areas

Infrared Infrared light waves are also used for short range communication of

information between computer devices.

IrDA (Infrared Data Association) is a group of computer device manufacturers that developed, implemented and still maintaining the standard.

The wave spectrum used is below the visible light waves (red waves are is the lowest visible frequencies).

Absolute line of site is needed because these waves cannot penetrate obstacles or overcome them.

Used for short distance (about 10 meters – 30 feet) in communicating and networking computer devices

Most modern computer equipment and computer devices are equipped with IrDA ports so they can communicate and exchange files without any need of connecting IrDA special accommodations.

Wireless mouse, wireless keyboard, wireless printer, wireless scanner and generally any wireless peripheral device is equipped with an infrared port and infrared transmitter and receiver.

Remote control devices use IrDA standard to transmit command to electronic equipment and electronically operated gates and other industrial features.

Light travel distance & time from space to earth

Planet Distance (Km) Time

Sun 150,000,000 8’ 20”

Mars 92,500,000 5’ 09”

Moon 384,000 ( 01.3)”

Sirius (Brightest star) 80,000,000,000,000 8.5 years

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