Unbounded / Unguided media or
wireless media doesn't use any physical connectors between the two
devices communicating. Usually the transmission is send through the atmosphere
but sometime it can be just across the rule. Wireless media is used when a
physical obstruction or distance blocks are used with normal cable media. The
three types of wireless media are:
1) RADIO WAVES
2) MICRO WAVES
3) INFRARED WAVES
1) RADIO WAVES:-
Ø
It has frequency between 10 K Hz to1 G
Hz.
Ø
Radio waves has the following types.
i.
Short waves
ii.
VHF (Very High Frequency)
iii.
UHF (Ultra High Frequency)
i.
SHORT WAVES:-
v There are different
types of antennas used for radio waves.
v Radio waves
transmission can be divided into following categories.
i.
LOW POWER, SINGLE FREQUENCY.
ii.
HIGH POWER, SINGLE FREQUENCY
i.
LOW POWER , SINGLE FREQUENCY:-
v As the name shows
this system transmits from one frequency and has low power out. The normal
operating ranges on these devices are 20 to 25 meter.
Ø
CHARACTERISTICS LOW POWER , SINGLE FREQUENCY:-
v Low cost
v Simple installation with pre-configured
v 1 M bps to 10 M bps capacity
v High attenuation
v Low immunity to EMI
ii.
HIGH POWER, SINGLE FREQUENCY:-
v This is similar to
low power single frequency. These devices can communicate over greater
distances.
Ø
CHARACTERISTICS HIGH POWER, SINGLE FREQUENCY:-
Moderate cost
Easier to install than low power single frequency
1 Mbps to 10 Mbps of capacity
Low attenuation for long distances
Low immunity to EMI
2) MICRO WAVES
Ø
Micro waves travels at high frequency than radio waves and
provide through put as a wireless network media. Micro wave transmission
requires the sender to be inside of the receiver.
Following are the
types of Micro waves.
i.
Terrestrial Micro waves
ii.
Satellite Micro waves
i.
Terrestrial Micro waves:-
Ø
Terrestrial Micro waves are used are used to transmit wireless
signals across a few miles. Terrestrial system requires that direct parabolic
antennas can be pointed to each other. These systems operate in a low Giga
Hertz range.
CHARACTERISTICS
of Terrestrial Micro waves:-
v Moderate to high cost.
v Moderately difficult installation
v 1 M bps to 10 M bps capacity
v Variable attenuation
v Low immunity to EMI
ii.
Satellite Micro waves
Ø
The main problem with aero wave communication is the curvature
of the earth, mountains & other structure often block the line of side. Due
to this reason, many repeats are required for long distance which increases the
cost of data transmission between the two points. This problem is recommended
by using satellites.
Ø
Satellite micro wave transmission is used to transmit signals
throughout the world. These system use satellites in orbit about 50,000 Km
above the earth. Satellite dishes are used to send the signals to the satellite
where it is again send back down to the receiver satellite. These transmissions
also use directional parabolic antenna’ with in line of side.
Ø
In satellite communication micro wave signals at 6 GHz is
transmitted from a transmitter on the earth through the satellite position in
space. By the time signal reaches the satellites becomes weaker due to 50,000
Km distance. The satellite amplifies week signals and transmits it back to the
earth at the frequency less than 6 GHz.
Characteristics
Satellite Micro waves:
v High cost
v Extremely difficult and hare installation.
v Variable attenuation.
v Low immunity to EMI
v High security needed because a signal send to satellite is broadcasts
through all receivers with in satellite
3) Infrared
Ø
Infrared frequencies are just below visible light. These high
frequencies allow high sped data transmission. This technology is similar to
the use of a remote control for a TV. Infrared transmission can be affected by
objects obstructing sender or receiver. These transmissions fall into two
categories.
i.
Point to point
ii.
Broadcast
i.
Point to Point: - Point to point infrared
transmission signal directly between two systems. Many lap top system use point
to pint transmission. These systems require direct alignment between many
devices.
Characteristics
of Point to point:-
v Wide range of cost
v Moderately easy installation.
v 100 k bps to 16 Mb of capacity.
v Variable attenuation.
v High immunity to EMI
ii.
Broad Cast: - These infrared transmission use
sprayed signal, one broad cast in all directions instead of direct beam. This
help to reduce the problems of proper alignment and abstraction. It also allows
multiple receiver of signal.
Characteristics
of Broad Cast:-
v In expensive.
v Single installation.
v 1M bps capacity.
v Variable attenuation.
Radio frequency
Ø radio
frequency, any frequency within the electromagnetic spectrum associated with
radio wave propagation. When an RF current is supplied to an antenna, an
electromagnetic field is created that then is able to propagate through space.
Many wireless technologies are based on RF field propagation.
Ø These
frequencies make up part of the electromagnetic radiation spectrum:
a. Ultra-low
frequency (ULF) -- 0-3 Hz
b. Extremely
low frequency (ELF) -- 3 Hz - 3 kH
c. Very low
frequency (VLF) -- 3kHz - 30 kHz
d. Low
frequency (LF) -- 30 kHz - 300 kHz
e. Medium
frequency (MF) -- 300 kHz - 3 MHz
f. High
frequency (HF) -- 3MHz - 30 MHz
g. Very high
frequency (VHF) -- 30 MHz - 300 MHz
h. Ultra-high
frequency (UHF)-- 300MHz - 3 GHz
i. Super
high frequency (SHF) -- 3GHz - 30 GHz
j. Extremely
high frequency (EHF) -- 30GHz - 300 GHz
Cellular telephone
Ø Cellular
telephone, sometimes called mobile telephone, is a type of short-wave analog or
digital telecommunication in which a subscriber has a wireless connection from
a mobile telephone to a relatively nearby transmitter. The transmitter's span
of coverage is called a cell. Generally, cellular telephone service is
available in urban areas and along major highways. As the cellular telephone
user moves from one cell or area of coverage to another, the telephone is
effectively passed on to the local cell transmitter.
Ø A
cellular telephone is not to be confused with a cordless telephone (which is
simply a phone with a very short wireless connection to a local phone outlet).
Ø The first
cellular telephone for commercial use was approved by the Federal
Communications Commission (FCC) in 1983. The phone, a Motorola DynaTAC 8000X,
weighed 2 pounds, offered just a half-hour of talk time for every recharging
and sold for $3,995.
How those it work?
• Before exploring the maximum range of a
cellular telephone, it is first important to understand how they function. In
their most basic form, cell phones are radio transponders, converting voice
sounds into radio waves, sending them to a local receiver (tower), and also
receiving radio waves from that tower. All of the additional functionality of
cell phones--text messages, web surfing, digital encoding, and so on--are
extras performed by the handset itself, converted into radio waves, and sent as
radio signals to the closest tower.
Distant cover
• Before examining the range of phones, it
is also important to observe that different types of phones, using different
technology, can transmit radio waves different distances. The Global System for
Mobile communications (GSM) standard actually limits cell phone
transmissions to 35 kilometers, though the phones themselves may be
physically capable of transmitting over greater distances. GSM technology is
nearly universal in Europe, Asia, and other continents, and is employed by
American carriers AT&T and T-Mobile. A different technology common in North
America, CDMA (short for Code Division Multiple Access), can achieve
significantly greater transmission distances, sometimes up to double the
distance of GSM phones. CDMA technology is currently used by American carriers
Sprint/Nextel and Verizon, as well as several smaller resellers of their
network services
CELLULAR
TELEPHONE EQUIPMENT
1)
Samsung Cellular Telephone Stereo
Earphones.
2) Samsung Cellular Telephone Stereo Earphone Adapter.
Adapter allows the use of any stereo earphone/headphone
with a standard 1/8" (3.5mm) stereo plug.
3) Samsung Cellular Telephone USB Data Cable
4) NOKIA Hands-Free In-Ear Cellular Telephone Earset. For use with Nokia 5100/6100 series cellphones. High-sensitivity microphone and earphone. 4 foot cord with clothing clip. Includes instructions.
5) Hands-Free In-Ear Cellular Telephone Headset.
Works with any cellular telephone that has a standard 2.5mm
headset jack. High-sensitivity microphone and earphone.
4 foot cord with clothing clip. Includes instructions.
6) Nokia AC-Operated Battery Charger.
Operates on 120VAC.
For use with Nokia cellphone models
7) Nokia AC-Operated Battery Charger.
Operates on 120VAC.
For use with Nokia cellphone models
8) Nokia Cigarette Lighter Adapter/Charger.
For use with Nokia cellphone model
9) Samsung Cigarette Lighter Adapter/Charger.
Features Short-circuit Protection and Charging LED
10) Universal Cellular Telephone Holder.
Very well made suction-mount holder quickly attaches
and removes from any glass or flat surface. Fully
adjustable with padded spring-loaded jaws that can
hold almost any item from 1 5/8" to 2 3/4" in width.
Perfect for cellphones, hand-held scanners, ham
and family radios, and GPS units.
What is 3g?
Ø 3G is the
third generation of mobile phone standards and technology. 3G supersedes 2G
technology and precedes 4G technology. 2.5G was a temporary bridge between 2G
and 3G.
Ø 3G
technologies enabled faster data-transmission speeds, greater network capacity
and more advanced network services.
Ø The first
pre-commercial 3G network launched in May 2001 by NTT DoCoMo in Japan. The
network was branded as FOMA.
Ø Following
the first pre-commercial launch, NTT DoCoMo again made history with the first
commercial launch of 3G in Japan on Oct. 1, 2001.
What is 4g?
Ø 4G stands
for Fourth Generation of wireless networks. It comes as an improvement over 3G
networks and may stand as a successor thereof. While 3G is a suite of several
wireless network protocols, 4G is basically one protocol, called WiMAX. There
is also the other standard called LTE Advanced, but WiMAX (technically termed
806.16m) is more common.
Many people use 4G and
WiMAX interchangeably. 4G standards are WAN standards, i.e. they offer
connectivity to devices over a wide area. A 4G network can cover a whole
city or country
