2. MobileComp Chap01 L01 wirelesstrans.ppt

Mobile Computing Intro

1. 1
Mobile Computing
UNIT - I
Mobile Communication

2. 2
Communication
•Communication ─ a two-way transmission
and reception of data streams
•Voice, data, or multimedia streams
transmitted in terms of signals.
•Signals from a system can be transmitted
through a fibre, wire or wireless medium.
•Transmitter send signals According to
defined regulations, recommended
standards, and protocols

3. 3
Mobile Communication
•Entails transmission of data to and from
handheld or Mobile devices
•Out of the Two or more communicating
devices At least one is handheld or mobile
•The Location of the device can vary either
locally or globally
•Communication takes place through a
wireless, distributed, or diversified network

4. 4
Transmission Modes
a. Simplexb. Half Duplex c. Full Duplex

5. 5
•Unicasting
•Multicasting
•Broadcasting

6. 6

7. Characteristics of
Mobile communication
•Fixed and wired: This configuration
describes the typical desktop computer in
an office.
•Mobile and wired: Many of today’s
laptops fall into this category; users carry
the laptop from one hotel to the next,
reconnecting to the company’s network via
the telephone network and a modem.
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8. Characteristics of
Mobile communication(2)
•Fixed and wireless: This mode is used for
installing networks, e.g., in historical
buildings to avoid damage by installing
wires.
•Mobile and wireless: This is the most
interesting case. No cable restricts the
user, who can roam between different
wireless networks.
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9. 9
Guided (Wired) Transmission
•There is Direct (Dedicated) path between
the sender and receiver.
•Metal wires and optical fibres guided or
wired transmission of data
•Guided transmission of electrical signals
takes place using four types of cables

10. 10
Four types of cables for Guided
Transmission

11. 11
Four types of cables for Guided
Transmission

12. 12
Fibre- and wire- based
transmission and their ranges

13. 13
Guided Transmission Advantages
•Transmission along a directed path from
one point to another
•Practically no interference in
transmission from any external source or
path
•Using multiplexing and coding, a large
number of signal-sources simultaneously
transmitted signals along an optical fibre,
a coaxial cable, or a twisted-pair cable

14. 14
Guided Transmission
Disadvantages
•Signal transmitter and receiver fixed
(immobile). Hence there is No mobility of
transmission and reception points.
•The Number of transmitter and receiver
systems limits the total number of
interconnections possible

15. 15
Unguided Wireless Transmission
─

16. LW, MW, SW, FM
•LW (Lower Wavelength Radio) : 30 kHz to 1
MHz (10,000 to 300 m)
•MW (Medium Wavelength Radio) : 500 kHz
to 2 MHz (600 to 150 m)
•SW (Short Wavelength Radio) : 6 to 30 MHz
(50 to 10 m)
•FM (Frequency Modulation): 87.5 to 108
MHz
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17. 17
VHF and TV-VHF

18. 18
UHF, GSM, DECT, 3G and DAD

19. 19
Super high Microwave and
Extreme High
•2 GHz to 40 GHz (15 cm to 0.75 cm)
[Microwave bands and satellite signal
bands]
•Extreme high frequency (EHF): Above 40
GHz to 10
14
Hz (0.75 cm to 3 m)

20. 20
Infrared
•Far Infrared: Optical wavelengths
between 1.0 m to 2.0 m and [ (1.5
to 3) x 10
14
Hz (0.15-0.3 THz)]
•Infrared: 0.90 m to 0.85 m in
wavelength and  (3.3 to 3.5) x 10
14
Hz
[≡ 350 to 330 THz]

21. Visible light &
Ultravoilet
•Visible Light: 0.70 m to 0.40 m in wave
length and  (4.3 to 7.5) x 10
14
Hz [≡ 430
to 750 THz]
•Ultraviolet: < 0.40 m in wavelength (>
750 THz).
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22. 22
Antennae
•Devices that transmit and receive
electromagnetic radiation.
•Most function efficiently for relatively
narrow frequency ranges
•The forms of antennae are chiefly
determined by the frequency ranges they
operate in and can vary from a single
piece of wire to a parabolic dish

23. 23
/2 Dipole Antenna
it is a /2 – long antennae for wireless transmission
of waves of wave length . It is also called a dipole
antenna because at any given instant at the both
ends A and B are 180
0
out of phase (means currents
in opposite direction).

24. 24
/4 Dipole Antenna
•it is a /4 - antennae mounted on long conducted
surface or the roof of a car or moist ground
surface for wireless transmission of waves of
wave length . At any given instant the signals at
the end C and surface D are 180
0
out of phase
(means currents in opposite direction).

25. 25
/2 Radiation pattern in z-y and x-z
planes- Identical signal amplitude
along circle

26. 26
/4 Radiation pattern in y-z and x-z
planes Radiation Pattern

27. 27
Same Antenna Radiation pattern
in x-y planes Radiation Pattern
Circular pattern means that radiated energy, and
thus signal strength, is equally distributed in all
directions in the plane.

28. 28
Directed Transmission Antenna
Radiation pattern in z-y and z-x planes
Radiation Pattern
Directed pattern means that radiated energy, and thus
signal strength, is directed along a specific direction
in the plane. A directed radiation pattern is required
between a mobile user and the base station

29. Problem 1
A 200 MHz and 2000 MHz UHF signal is to be
transmitted wirelessly. What are the lengths of the Dipole
antennas required for transmission of those signals?
Sol: i) For wave length 200 MHz
Here, f = c/ Hz = (300/) MHz
So,  = 300/f
 = 300/200
 = 1.5 m
Length of the dipole antenna = /2
So, the Length of the dipole antenna = /2 = 1.5/2 = 0.75m = 75cm.
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30. ii) For wave length 2000 MHz
Here, f = c/ Hz = (300/) MHz
So,  = 300/f
 = 300/2000
 = 0.15 m = 15cm
Length of the dipole antenna = /2
So, the Length of the dipole antenna = /2 = 15/2 = 7.5 cm.
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31. Problem 2
A dipole antenna is to be mounted on conducting surface. Calculate
the length of the required antenna for transmitting a GSM signal of
frequency 900 MHz.
Sol : Using the Classical formula f = c/ Hz = (300/) MHz
So,  = 300/f
 = 300/900
 = 0.333 m = 33.3 cm
Length of the antenna mounted on conducting surface = /4
So, the Length antenna = /4 = 33.3/4 = 8.325 cm.
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