mobile computing

1. WIRELESS COMMUNICATION FUNDAMENTALS
Unit 1

2. Mobile Computing
• Mobile computing refers to the set of IT technologies, products,
services and operational strategies and procedures that enable end
users to access computation, information and related resources and
capabilities while mobile.
Consumers use mobile computing in several ways, including the
following:
• Internet access
• mobile communications
• web browsing
• mobile applications
• entertainment streaming media

5. A short History of wireless Communications

6. 1890s – First Wireless Communication
1900s – First Radio Broadcast
1920s – First Commercial Radio
1930s – Radar technology, Television Broadcasting
1940s – Quality Radio Services
1950s – First Satellites, the Space program
1970s – Mobile networks, GPS
1980s – First-generation mobile networks
1990s – Second-generation mobile networks, Wi-Fi
2000s – Satellite internet, 3G Networks
2010s – LTE advanced, 5G network
A short History of wireless Communications

8. Wireless Transmission
Wireless transmission is a form of unguided media. Wireless communication involves no physical link
established between two or more devices, communicating wirelessly. Wireless signals are spread over
in the air and are received and interpreted by appropriate antennas.

9. Wireless Transmission
Radio Transmission
Radio frequency is easier to generate and because of its large wavelength it can penetrate through walls and
structures alike. Radio waves can have wavelength from 1 mm – 100,000 km and have frequency ranging from 3 Hz
(Extremely Low Frequency) to 300 GHz (Extremely High Frequency).
A Radio is the simplest example of Radio wave communication. Other examples include RADAR, Satellite
communications, Bluetooth headsets, TV Broadcasts, GPS Signals, etc.

10. Microwave Transmission
Electromagnetic waves above 100 MHz tend to travel in a straight line and signals over them can be sent by beaming
those waves towards one particular station.
Because Microwaves travels in straight lines, both sender and receiver must be aligned to be strictly in line-of-sight.
Used in
Radar Communication(Weather forecast, Military Communication etc). Cooking, Drying, Heating
Infrared Transmission
Infrared wave lies in between visible light spectrum and microwaves. It has wavelength of 700-nm to 1-mm and
frequency ranges from 300-GHz to 430-THz.
Infrared wave is used for very short range communication purposes such as television and it’s remote.
Used in
Remote controls for television, stereos and other home appliances, Wireless LANs, Fire detectors. Night vision systems.

11. Signals
Signals are the physical representation of data. Users of a communication system can only exchange
data through the transmission of signals.
Signals are functions of time and location.
Signal parameters are the Amplitude A, the Frequency f, and the Phase shift φ.

12. Antennas
An antenna is a transducer that converts radio frequency (RF) fields into alternating current or vice
versa. There are both receiving and transmission antennas for sending or receiving radio
transmissions.
Transmitting Antenna - Collect electrical signals from a transmission line and converts them into
radio waves.
Receiving Antenna - collect radio waves and converts them into Electrical signals.
A signal from a transmission line or the guiding device like a co-axial cable, is given to an antenna,
which then converts the signal into electromagnetic energy to be transmitted through space.

13. Signal Propagation
• Signal Propagation is the process of spreading of Communication signals
from place to place.
• Like wired networks, wireless communication networks also have senders
and receivers of signals.
• In wireless networks, the signal has no wire to determine the direction of
propagation, whereas signals in wired networks only travel along the wire.
Transmission range: Within a certain radius of the
sender transmission is possible
Detection range: Within a second radius, detection
of the transmission is possible
Interference range: Within a third even larger
radius, the sender may interfere with other
transmission by adding to the background noise.

14. Signal Propagation

15. Signal Propagation

16. Multipath Propagation
• Multipath Propagation is the propagation phenomenon that results in radio signals reaching the receiving
antenna by two or more paths.
• Delay Spread Due to the finite speed of light, signals travelling along different paths with different
lengths arrive at the receiver at different times. This effect (caused by multi-path propagation) is called
delay spread: the original signal is spread due to different delays of parts of the signal.
• The energy intended for one symbol now spills over to the adjacent symbol, an effect which is called
intersymbol interference (ISI).

17. Modulation
• Digital modulation is the process of encoding a digital
information signal into the amplitude, phase, or frequency of the
transmitted signal.

18. Amplitude shift keying (ASK),
• Amplitude shift keying (ASK), the most simple digital modulation
scheme. The two binary values, 1 and 0, are represented by two different
amplitudes.
Frequency shift keying
A modulation scheme often used for wireless transmission is frequency
shift keying (FSK). The simplest form of FSK, also called binary FSK
(BFSK), assigns one frequency f1 to the binary 1 and another frequency f2
to the
binary 0.

19. Phase shift keying
• Phase shift keying (PSK) uses shifts in the phase of a signal
to represent data.
• Phase-shift keying is a digital modulation process which conveys data
by changing the phase of a constant frequency reference signal.
• The modulation is accomplished by varying the sine and cosine inputs
at a precise time.
• It is widely used for wireless LANs, RFID and Bluetooth communication.
• This simple scheme, shifting the phase by 180° each time the value of
data changes, is also called binary PSK (BPSK).