Chapter V
Fundamentals of telecommunications
Wired, wireless and beyond
1- Introduction:
a. Since his existence on earth man was looking to communicate with other people and
creature around him.
b. In looking for communication tools he first found some :
i. The sun and the stars and their reflection on things around him.
ii. The fire after it was invented from friction.
iii. The smoke generated by incomplete fire.
c. Then he felt the need for more effective tool that he can use to formulate his needs and
ideas in a clearer way and store them on tangible material so they can be easily
exchanged with others over a distance. Alphabet was born as it was found in ancient
traces everywhere around the world.
d. Before the alphabet man found around him tools and material to draw lines and signs
on stones or wood or large leaves and carve them on stones and wood.
e. That is what accelerated the creation of community and society including villages, cities,
counties and states.
2- Electricity and electronics:
a. Arab and Greek civilization apparently new the modern electricity about 1000 B.C
because they had amber trees and they used the amber to make beads that become
charged by rubbing so we can recognize it and things closely located around it.
b. The word “electricity” was first coined by William Gilbert referring to “electrocus” the
Greek word for amber. Around 1600 Gilbert discovered the electrification of many
substances and he is considered the father of modern electricity.
c. In 1873 Maxwell discovered the waves of electromagnetic field and that they are
traveling at the speed of light and Heinrich Hertz experimentally confirmed that
discovery and established the Hz as the unit to measure the wave cycle. Marconi used
the waves (1895) when he developed a radio.
d. John Fleming invented the rectifier diode (vacuum tube with two electrodes) in 1904
and in 1907 Lee De Forest developed the amplifier thermionic triode (three electrodes)
by adding one electrode to the diode and that was the date electronics technology was
born.
e. Vacuum tubes generate a lot of heat and consume a lot of power but they were very
helpful in powering the first telegraph, telephone, radio and computer devices and
carrying out the most needed roles in electronic circuit as rectifier, amplifier and switch.
f. The first silicon metal-oxide semiconductor transistor (MOS-transistor) was built at Bell
labs by (Atalla and Kahng).
g. The greatness of the transistor is that it imposed itself as the key active component in all
modern electronic devices and electronics technology because it was the first
component to enjoy the following characteristics:
i. Very little power consumption
ii. Very small size.
iii. Easiness of its mass production
iv. Availability of raw material at cheap cost.
Telecommunication technology
The telecommunication technology evolution can be easily matched with the electricity and electronics
evolution. Throughout its history we can track three technological avenues of electrical and electronic
telecommunications: Telegraphy, telephony and radio. The used media to send the signal used by all
technologies can be classified as wired, wireless or a combination of both.
Telegraphy
1- Introduction
a. This technology is now obsolete but it is very important to be knowledgeable about its
impact on people, society and economy and its importance in the modern
telecommunication technology evolution
b. Electrical telegraphy was the product of the electro-magnet invention in 1825 by the
British inventor William Sturgeon.
c. In 1838 Samuel Morse invented the telegraph by sending pulses of electrical current to
magnetize a magnet and strike a code on a tape (Morse code) that can be read later by
a telegraph specialist. Morse code is non-digital data representation system based on
two symbols point and dash.
i. Letters, symbols and numbers are represented with variable combinations of
dots and/or dashes that range between 2 and 6.
ii. The duration or length of dash is 3 times that of a dot
iii. Trained Morse code telegraph operator can convert up to 50 words /minute. In
1914 an automatic conversion technology was inaugurated that performs about
the double of that speed (up to 100 wpm).
iv. Other than electrical signal Morse code is transmitted using light or reflection of
mirrors or sounds. It is presently used in case of distress or conditions that
render the signal transmission impossible.
2- Telegraphy evolution after Morse
a. Morse invention was a sounding commercial and practical success and people find in it a
wonderful way to communicate and do business. In 1943 the Congress agreed to fund
$30,000 to construct a 40 miles telegraph line linking Washington D.C and Baltimore.
b. After that line was operational, Morse and associates were overwhelmed by private
business funds asking them to extend the telegraph line to Philadelphia and New York.
At the same time many telegraph businesses start providing telegraph services.
c. US postal telegraph for business and economic purposes was inaugurated in 1881 until
it merged with the Western Union in 1943.
d. Very important technological development took place in 1913. Western Union
introduced multiplexing technology that can transmit up to eight different messages
simultaneously over a single wire. 1925 the Tele-printer machine that convert and print
the Morse code was being introduced.
e. 1936 witness another technological breakthrough when Varioplex technology, that
enabled one single wire to carry 72 different transmission signals, was introduced
f. 1938 Western Union introduced the facsimile devices and facsimile service and in 1959
it introduced the Telex service and opened it for subscribers who now had the possibility
to dial each other and exchange messages directly.
Telephony
1- Introduction:
a. Telephone technology has its solid foundations established by the improved
development of telegraph technology. In attempting to improve or enhance telegraphy
Bell invented telephony.
b. Telegraph was the only technology available in telecommunications for 40 years (18361876). In 1876 electrical telephony was born.
c. Who invented the telephone? Question very difficult to answer as there were many
people involved in the creation of this technology at the same time.
d. Invention patent was and still is excessively disputed by several inventors:
i. 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).
ii. 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.
iii. 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.
2- How it all works?
a. To establish an electronic communication the system needs:
i. Transmitter to convert 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
ii. Receiver to 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 reproduce
the audio signals sent.
iii. A transmission medium able to provide a safe pathway between sender and
receiver.
iv. Amplifiers interposed on the way to compensate the loss in decibel of the signal
due to resistance encountered on the way.
b. Early systems allowed one way transmission and one way receiving (you can either
transmit or receive at a time). That was known as the simplex telecommunication.
c. Technology that allows you to transmit and receive simultaneously is known as the full
duplex technology
d. Technology that allows you to shift between both transmission and reception by means
of pushing a button or other handy switch is known as the half-duplex technology.
e. To make a call in earlier telephone technology you had to turn a handle that generate
signal able to activate the bell magnet of the receiver and the bell rings alarm the
receiver to an incoming call.
f. In modern technology each subscriber has a reference number that can be dialed to
activate the magnet that rings the bell.
3- Telephony evolution
a. Telephone technology went a long way from central exchange to dialing numbers.
b. 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.
c. 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.
d. 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).
e. Automatic switching had deep impact on the job market; it resulted in the loss of millions
of telephone operator jobs worldwide.
f. Because of these technological advances under business pressure, telephone technology
found itself evolving toward networking technology very naturally.
4- Pros and cons of the telephone: we consider here the wired telephony and not the wireless or
mixed technology.
a. The pros:
i. Stable and reliable communication with no restraints of signal loss or influence
of weather conditions
ii. Inexpensive technology. Easy to install a network with basic network
components
iii. Very well suitable to the military and business campuses.
iv. High level of security (no wave interception to worry about especially in local
and in-campus networks.
v. Cost is very reasonable.
vi. No power connection required (very reliable during communication in case of
prolo9nged power outage during natural disasters.
vii. Easy networking
viii. Easy control and updating
ix. High voice quality
x. Telephone network extends all over the planet so you can reach anyone you
want anytime you want.
b. The cons:
i. Very limited mobility (fixed structure)
ii. Difficult lay down of ground cable with digging required sometimes
iii. Difficulties of maintenance and troubleshooting
iv. No special skills, no expertise and no training required to use it.
v. Installation cost is high and sometimes prohibitive.
Wired telecommunications
1- Wired technology requires the transmitter and receiver to be connected to a pair of wires that
form a closed electrical circuit.
2- Telegraphy and telephony were both wired technologies until recently telephone technology
started using combined wired/wireless connection
3- Wired technology uses many different types of cables:
a. Twisted pairs cable:
i. Consists of many pairs of twisted insulated wires protected by a hard insolation
shield.
ii. 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).
iii. 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
b. Coaxial cable: Consists of an inner copper conductor insulated from surrounding metal
braiding shield and both insulated from the outside with strong hard insulation.
i. Inner and outer conductors travel parallel to each other that result in minimal
decibel loss.
ii. This technology is used when high quality connection is needed especially in
connecting antennas, dishes, network connections, etc…
iii. This cable is relatively very expensive. It is only used for special short distance
connections.
c. 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.
i. They are widely used in campuses, buildings, subdivisions, industrial plants,
etc…
ii. 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
iii. Provides the backbone for most business networks
iv. Businesses usually lay much more than they need because difference in cost is
not really meaningful.
v. May be laid underwater in oceans to form transcontinental links.
vi. Pros:
1. Operates at very high speed and large capacity
2. Not affected by surrounding electromagnetic noise generated by
motors, radio, other cables, etc…
3. Easier and cheaper maintenance.
4. Signals travel long distance without any need for amplifying and
strengthening.
vii. Cons:
1. They are very fragile and need to be protected from bending and
passing over by transportation means, people and animals.
2. Need to be protected from water contamination.
3. Any wear or degradation in the fiber insulation will cause signal flare to
affect other fibers causing quality deterioration.
4. High cost.
viii. How fiber technology works:
1. Imagine a very thin very long (60 miles) pipe whose interior surface is
coated with a mirror.
2. 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).
3. 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.
4. Signal transmitted over the fibers are all transformed into digital (light
or no light) and that is how the transmission works.
d. T1 line:
i. Reserved circuit that uses copper or fiber optic cables to operate over various
networking distances.
ii. T1 data rate is 1.54 Mbps similar to symmetric DSL (Digital Subscriber Line)
iii. Monthly Cost is between $350 and $1000 and more and mostly used by hotels,
apartment buildings and subdivision and some business and college campuses
where the cost can be justified.
e. T3 line:
i. Use copper and fiber optic cables to operate as a reserved circuit equivalent to
an aggregation of 28 T1 lines.
ii. Data rate is about 44.7 Mbps (the math doesn’t apply exactly in this bandwidth
case because 28 x 1.54 = 43.12 and not 44.7 which is the bandwidth of T3)
iii. Monthly cost is about $3000 - $12000 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.
f. Cables in general have some advantages over wireless:
i. Compatibility with industry standards are very flexible to be tailored so that
industry standards are satisfied.
ii. Capacity is usually higher
iii. Reliability
Wireless (Radio frequency)
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
(1.08) billion km/h
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 signal = 300/3 = 100 meters
b. The wavelength of 30 MHz frequency signal = 300/30 = 10 meters
+
Analog
- - - - - - - - - - - digital
Time
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Radio telecommunications frequency distribution
1- Frequency/wave tables:
a. Radio waves range from 300 kHz to 300 GHz distributed as follow:
i. 30 GHz – 300 GHz EHF
Extremely High Frequency
Microwave
ii. 3 GHz - 30 GHz
SHF
Super High Frequency
medium Microwave
iii. 330 MHz – 3 GHz UHF
Ultra High Frequency
long oven Microwave
iv. 30 MHz – 330 MHz VHF
Very High Frequency
v. 3 MHz – 30 MHz
HF
High Frequency
vi. 300KHz – 3 MHz
MF
Medium Frequency
vii. 30 KHz – 300 KHz LF
Low Frequency
viii. 10 KHz – 30 KHz
VLF
Very Low Frequency
b. Another NASA classification of frequencies and waves is very interesting to highlight:
i. Radio waves :
30 KHz- 3 GHz
Height of Statue of liberty diameter
ii. Microwaves:
300 MHz- 300 GHz
Baseball diameter
iii. Infrared waves:
300 GHz- 400,000 GHz Human hair diameter
iv. Visible light waves 400,000 GHz – 500,000 GHZ
Red frequency
v. Visible light waves 500,000 GHz – 600,000 GHz
yellow & green Frequency
vi. Visible light waves 600,000 GHz – 750, 000 GHz
Blue and Violet Frequency
vii. Ultraviolet waves 750,000 GHz – 3,000,000 GHz Ultraviolet frequency
viii. X-Rays
100 million GHz – 1 billion GHz
ix. 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.
2- Signal propagation
a. While wired telecommunication uses cables to carry signals from one place to another,
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.
b. 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 (18741937) who developed radio telecommunication into commercial and military success.
c. 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.
d. The first transatlantic transmission achieved by Marconi in 1901 used 500 feet (152.4
meters) wire as reception antenna.
e. How it works?
i. 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)
ii. 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…)
f. Types of antennas:
i. 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.
1. Whip antenna: like car antenna
2. Turnstile antenna: high pole function as antenna,
ii. Directional antennas: When the sending and receiving direction matter then the
antenna should be directed following a given angle:
1. 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.
2. 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.
3. 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.
3- Wireless - Line of sight telecommunication:
a. Goethe, (1749-1832) evoking wave propagation, said: “why is it possible to hear around
corners, but not see around them?”
b. 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.
c. 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.
d. 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.
e. 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.
f. Because of the extensive need for diversified wireless telecommunication the US Federal
Communication Commission (FCC) has allocated bands of frequencies to each wireless
telecommunication industrial activity; we will list below some important wireless use:
4-
5-
6-
7-
i. Radio AM: .535 - 1.7 MHz
ii. CB (Citizens Band) radio: 26.96 – 27.41 MHz
iii. Radio FM: 88 – 108 MHz
iv. TV stations: 54 – 88 MHz and 174 – 220 MHz, etc…
v. Cell phones: 824 – 849 MHz
vi. Space station (MIR): 145 – 437 MHZ
vii. Baby monitors: 49 MHz
viii. GPS (Global Positioning System): 1227 – 1575 MHz
ix. Air traffic RADAR: 960 – 1215 MHz
Relays make the coverage possible:
a. Let’s consider two locations A and B separated by a mountain.
b. Microwave transmission from both sides will be impossible because signals will be absorbed
by the mountain (they hit and die).
c. Compare it to a vehicle traveling at very high speed if it crashes the vehicle and its
passengers are most likely to die.
d. To solve the problem we need a relay on top of the mountain or a satellite covering the area
that intercepts signals and retransmit them.
Towers as relays:
a. To satisfy the line of sight condition necessary for radio telecommunication, service
providers use high towers to install the antennas.
b. Towers may be installed as free standing or on top of high rise building roofs in cities:
c. 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’
d. 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. A telecommunication satellite works as a 300 miles high tower.
b. The round shape of the earth pose a natural obstacle between 2 distant locations
c. Telecommunication satellite orbits the earth at 200-300 miles altitude while covering a
specific area.
d. 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 the relay:
a. Radio signals traveling encounter resistance and lose a lot of their strength. The loss is
measured in decibels.
b. Relays intercept and retransmit signals
c. Relays are equipped with repeaters and transponders that amplify signals before being
retransmitted or redirected to their destinations.
d. Satellites broadcast the coordinates of their location in orbit (very important information
that makes the GPS technology possible.
8- Topology of radio communication: there are 3 different types of radio telecommunications
categorized by the signal flow direction:
a. Simplex topology:
i. This technology is based on the use of only one frequency channel to accommodate
the communication.
ii. Only one station can transmit or broadcast
iii. Examples are radio AM stations, radio FM stations, Television stations.
b. Half duplex technology also known as (HDX) technology
i. Use only one frequency channel to accommodate both transmitting and receiving of
communicating devices.
ii. All stations can transmit and receive but not simultaneously (only one station can
transmit at a time)
iii. Must push a button or a switch in order to switch from receiving to transmitting and
vice versa.
iv. Examples are: Citizens band (CB) radio, walkie-talkies and a lot of military radio
equipment.
1. Walkie-talkie has low transmission power can reach a range up to one mile.
2. CB radios have more transmission power they can be used for a range up to
5 miles by citizens, businesses, police and other agencies
v. This radio telecommunication system is not controlled by an technology protocol
that enforces transmission priorities
vi. 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.
c. Full duplex technology also known as (FDX) technology:
i. The full duplex technology basically uses 2 different frequency channels to send and
receive in each station.
ii. 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.
iii. 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.
iv. Examples of FDX includes but not limited to:
1. Wired telephone networks.
2. Wireless phones known as cordless phones.
3. Internet telephony
4. Cellphone technology
GPS (Global Positioning System)
1) GPS technology
a) GPS that we are using today is a utility owned by the US government and operated by the
government’s specialized agencies.
b) Department of Defense DOD) project that started in 1973 and became fully operational for both
military and civilian use in 1994 is controlled by the GPS directorate in the US Air force.
c) The first satellite navigation system in the US was used in 1960 and consists of a constellation of
5 satellites.
d) GPS system is composed of 3 parts:
i) 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.
ii) The satellite constellation comprises 24 - 36 satellites each of them broadcasts the
coordinates of its own location in orbit.
iii) Control and correction service:
(1) The computing accuracy is highly affected by the strength and accuracy of satellite
signals
(2) 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
2) GPS evolution
a) The system in use now is GPS II whose satellite constellation is aging and the renewing process is
under contract with Lockheed-Martin
b) Satellite renewing process started in 2012 and when completed it will be GPSIII.
i) 36 satellite constellation
ii) 3 times more powerful than GPS II
iii) 3 times more accurate than GPS II
3) Other GPS systems
a) 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).
b) 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.
c) 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.
4) How GPS works?
a) Each satellite continually send messages that have information about:
i) Coordinates of their location in orbit.
ii) The time they sent the message
b) 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.
c) GPS basic categories of use can be summarized by the abbreviation PNT
i) Positioning
ii) Navigation
iii) Timing
5) Areas of GPS use
a) Excluding their very important military field of applications, GPS applications in these 3 areas
cover a thirsty market in most human, natural and economic activities and because of the
technological advance we can pretend that this huge market will never be saturated.
b) Most applications can be classified under the following titles:
i) Cellphone technology
ii) Time synchronization where we may get accuracy in the order of 10 ns
iii) Air navigation system and aircraft tracking
iv) Automotive navigation system and vehicle fleet tracking
v) Emergency and natural disaster apps
vi) People, items an pet tracking
vii) Boats and ships navigation and tracking.
viii) Map industry
ix) Travel and tours industry
x) Robotic: Robot use GPS to identify environment and direction
xi) Medical and health awareness industry
xii) Sports and recreation.
xiii) Security related activities
Cellphone Technology
1- Technology fundamentals:
a. The cellular name relate to the basic concept of the technology that consider a
geographical area (a city for example) and treat it as a whole big hexagonal cell
b. That big cell will be divided physically into smaller cells which has a size about 10 square
miles (26 kilometers) each.
c. Service for each cell is covered by an infrastructure that consists of:
i. A high tower or high rise building to hold the antennas
ii. Necessary building to house the base station equipment.
iii. Transmission equipment, power equipment and other necessary working and
operational equipment.
2- Operational data:
a. Transmitter basically have to be operational with low transmission power (between .5
watt and 3 watts)
b. Each cellular provider gets from FCC (Federal Communication Committee) 832 different
radio frequencies for a specific area served by that provider.
c. 42 frequencies are used for control purposes.
d. Each communication call uses 2 frequencies;
i. Transmitting frequency
ii. Receiving frequency
e. For an area of 7 cells, cellphone provider can accommodate up to 56 possible user
communications simultaneously in each cell (56x7 = 392).
f. The low transmission powers make it possible for non-adjacent cells to use the same
frequencies without any fear from interference between conflicting calls using same
frequencies.
3- Link between cellphone and regular ground telephone network system:
a. A mobile telephone switching office (MTSO) is assigned the role of connecting cellphone
networks with land based normal telephone network.
b. Each cellphone provider establishes and maintains all services related to that facility
that also controls all base stations in that area.
4- Cellphone operational technologies
a. There are two incompatible technologies to operate cellphone networks;
i. Code Division multiple Access (CDMA):
1. Used in the USA, JAPAN and some companies in ASIA and South
America.
2. Phones use the same frequencies but are separated and recognized by a
different code used by the network to encode each call.
3. Compare it to your possibility to recognize the guitar sound from the
drum sound from the piano sound in a music concert.
ii. GSM/TDMA (Global System for Mobile communications/Time Division Multiple
Access).
1. European system used everywhere in the world even in the USA and
JAPAN. GSM is universal system.
2. 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).
3. Has SIM (Subscriber Information Module) card or chip to record
information of each subscriber authorized to use to network.
b. How the technologies compare?
i. 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.
ii. GSM/TDMA has a limited number of communication calls that may go
simultaneously. This ceiling is much higher or inexistent in CDMA.
iii. Although CDMA is the initial cellular technology, GSM is taking over because it is
much more user friendly.
iv. 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.
v. With smartphones extensively using the web. TDMA/GSM has proven to be fit
to handle data transmission and internet services better than CDMA.
i. RADAR (Radio Detection And Ranging)
2) 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).
3) Radar system components
a) Transmitter equipped with directed dish or antenna that sends radar pulses in predefined
direction
b) Receiver that gets weakened reflected signals, amplify them and display them on a monitor.
c) Signals captured help calculate:
i) The range or distance of the target
ii) The altitude of the target
iii) The speed of the target if it is moving
iv) The direction of movement
d) Some applications allow to analyze and make a judgment about the shape and behavior of the
shape
4) Applications:
a) Although it was first used for military purposes especially by the air force, navy and air defense
Radar has proven to be very important for the civilian transportation network businesses.
b) Airplanes use radar to detect flying objects around it and secure its pathway on time to avoid
crash
c) Flight controllers use radar to guide planes in fog and severe weather conditions and ultimately
help them to land without seeing the runway.
d) Radar system is used in harbor to monitor and regulate ship traffic movement especially in bad
weather conditions.
e) Ships use radar to detect other approaching objects and avoid crash and detect and calculate its
distance from the coast.
f) Radar is used by meteorologist as the primary tool to detect weather components and make
weather forecast.
LASER (Light Amplification by Simulated Emission of Radiation)
1- Principle:
a. Simulated emission as theorized by Einstein in 1917 can be defined as the laser
foundation.
b. Amplification and concentration of light emission power
2- Laser development requires the following necessary components:
a. Flash tube or flash lamp to provide
b. Gain medium that amplifies the light
c. A unit that supply energy to the gain medium
d. Feedback provided by a couple of mirrors installed on either end of the gain medium.
3- Topology of lasers: There are many different types of laser that use different material and
therefore, different technologies:
a. 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.
b. Gas Laser: Gases were proven to amplify light and many gas Lasers were built widely
used in optical research and training labs.
i. Helium-neon Laser
ii. Carbon dioxide Laser
iii. Argon Laser
c. Semiconductor Laser: use electrically pumped diodes. They are widely used in business
equipment and applications:
i. Laser printers
ii. Pointers of different uses.
iii. CD and DVD players and burners
iv. Cutting industry
d. Chemical Laser: Very powerful Laser of high interest in military applications and combat
Weaponry.
i. Hydrogen fluoride Laser
ii. Deuterium fluoride laser
e. Fiber Laser: is a specific type of semiconductor laser with reduced thermal effect but it
is used in the same way.
4- Business applications of Laser:
a. Military: Many applications using powerful laser in weaponry guiding and missile
defense.
b. Industry: many laser equipment sold for billions of dollars that include and not limited
to:
i. Cutting and welding applications, components measurement and marking.
ii. Products like printers, CD and DVD players, barcode scanners, pointing devices
and thermometers
iii. holograms
iv. Light shows.
v. Medicine
1. Laser Surgery and healing
2. Eye treatment and eye laser surgery
3. Cosmetics hair and skin treatment.
vi. Many other activities use Lase applications mainly in forensics and many
research areas.
Infrared transmission
1- Infrared light waves are also used for short range communication of information between
computer devices.
2- IrDA (Infrared Data Association) is a group of computer device manufacturers that developed,
implemented and still maintaining the standard.
3- The wave spectrum used is below the visible light waves (red waves are is the lowest visible
frequencies).
4- Absolute line of site is needed because these waves cannot penetrate obstacles or overcome
them.
5- Used for short distance (about 10 meters – 30 feet) in communicating and networking computer
devices
6- 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.
7- Wireless mouse, wireless keyboard, wireless printer and wireless scanner and generally any
wireless peripheral device is equipped with an infrared port and infrared transmitter and
receiver.
8- Remote control devices use IrDA standard to transmit command to electronic equipment and
electronically operated gates and other industrial features.
Light trip from select space locations to planet Earth
The table below illustrates how the light travels from some landmark of our surrounding
universe and how long it takes the light to travel from there and reach the earth.
Planet
Distance (Km)
Time
Sun
150,000,000
8’ 20”
Mars
92,500,000
5’ 09”
Moon
Sirius (Brightest star)
384,000
80,000,000,000,000
01.3”
8.5 years