This document discusses mobile computing and wireless communication systems. It covers topics like mobile handsets, wireless standards, WLANs, Bluetooth, and the components and architecture of mobile telecommunication systems. The key components of a wireless system are transmitters, receivers, antennas, filters, and amplifiers. It also describes the functions of these components and how they work together to transmit and receive signals. The architecture uses cellular networks with base stations that communicate via radio frequencies with mobile devices within hexagonal cells. The core network interconnects the base stations and switches to other networks like PSTN.

1. Mobile Computing
Sujesh P Lal
FISAT

2. Module - 1
• Topics to be Covered
– Introduction to Communication Technologies
• Mobile handsets
• Wireless Communication
• Server Applications
– Components of a Wireless Communication System
– Architecture of a mobile telecommunication system
– Wireless Standards
– WLANs
– Bluetooth Technology
• Bluetooth Low Energy(BLE), NFC
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3. Mobile handsets, Wireless Communication,
Server Applications
• Wireless Communication
• Wireless Networking
• Terrestrial radio system
• Satellite radio system
• Cellular communication technology
– “A technology that has revolutionized the human
society and impacted almost everybody, is the
cellular communication technology.”
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5. Components of a Wireless
Communication System
1. Transmitter
2. Receiver
3. Antenna
4. Filters
5. Amplifiers
6. Mixers
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6. Transmitter
• The input to a wireless transmitter may be voice, video,
data or other types of signal meant to be transmitted
to one or more distant receivers, called baseband
signal.
• The basic function of the transmitter is to modulate, or
encode several baseband signals onto a high frequency
carrier signal.
• A modulated high frequency signal can be radiated and
propagated more effectively and helps make more
efficient use of the radio frequency(RF) spectrum than
what we direct transmission of the individual baseband
signals can achieve.
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7. Receiver
• The receiver receives the modulated signals
and reverses the functions of the transmitter
component and thereby recovers the
transmitted baseband signal.
• The antenna of the receiver is usually capable
of receiving the electromagnetic waves
radiated from many sources over a relatively
broad frequency range.
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8. Antenna
• The function of the antenna is to convert the
electric signal from a transmitter to a propagating
electromagnetic RF wave, or viz.
• In a transceiver, a transmitter and a receiver is
co-located for supporting full duplex
communications.
• The same antenna is shared by both the
transmitter and receiver.
• There are mainly two types of antennas that are
used on wireless networks:
– Omni-directional
– Directional
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9. Filters
• Filters are key component present in all
wireless transmitters and receivers.
• Used to reject interfering signals lying outside
the operating band of receivers and
transmitters.
• Filters also reject unwanted noise signals
generated by the amplifier circuitry.
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10. Amplifiers
• Amplifier amplifies the strength (usually voltage) of a
signal
• The important specification of an amplifier include
power gain and the noise figure.
• The noise figure of an amplifier is a measure of how
much noise is added to the amplified signal by the
amplifier circuitry.
• This is most critical in the front-end of the receiver
where the input signal is very weak and it is desirable
to minimize the noise added by the receiver circuitry.
• It is necessary that the first amplifier in the receiver
circuit has as low a noise figure as possible.
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11. Mixers
• A mixer is typically used to achieve frequency
conversion at the transmitters and receivers.
• Frequency conversion is required because it is
advantageous to transmit signals at a higher
frequency, this is achieved by modulating a
carrier wave form using the original baseband
frequency.
• When a baseband signal is mixed appropriately
with a high Fz on a carrier, it can be easily and
efficiently radiated and becomes less susceptible
to noises and attenuation.
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13. Architecture
• Mobile handsets communicate over the radio access
network.
• The radio access N/W is primarily composed of the
base stations which communicate with the mobile
phones using radio Fz. electromagnetic waves.
• The coverage area is decomposed into hexagonal cells,
in each cell, a base station is located.
• Two types of radio channels are usually involved in the
communication between the base station and the
mobile handsets:
– Control channels and
– Voice Channels
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14. Architecture
• Control Channel
– Typically use frequency shift keying (FSK) and are
used for transferring control messages (data)
between the base station and mobile phones.
• Voice Channel
– Typically use frequency modulation (FM).
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15. Architecture
• A base station typically has two antennas of
different characteristics, one for receiving and the
other for transmitting.
• Which increases the ability of the base station to
receive the radio signals from the mobile phones
that use very low transmitter power levels.
• On the other hand, mobile handsets typically use
the same antenna for both receiving an
transmitting.
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16. Architecture
• The core n/w interconnects the base stations,
switches the mobile switching centre (MSC), and
also provides an interface to other networks such
as the traditional telephone n/w (PSTN) and the
internet.
• The interconnect used in the core n/w is required
to provide high speed connectivity, therefore,
usually fibre optic cables are used as the
interconnect in the core n/w.
• Based on the terrain conditions, microwave
communication is also used.
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