wireless and mobile - · pdf filewhy wireless communication 1 freedom from wires. ... indoor...

Department of Computer Science

DCS

COMSATS Institute of

Information Technology

Wireless and Mobile Communication

Rab Nawaz JadoonAssistant Professor

COMSATS IIT, Abbottabad

Pakistan

Mobile Communication


What is Wireless Communication?

Transmitting/receiving voice and data using electromagnetic waves in open space.

The information from sender to receiver is carried over a well defined channel.

Each channel has a fixed frequency bandwidth & capacity (bit rate).

Different channels can be used to transmit information in parallel and independently.

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Mobile Communication

A wireless form of communication in which voice and data information is emitted, transmitted and received via microwaves.

This type of communication allows individuals to converse with one another and/or transmit and receive data while moving from place to place.

Some examples include: cellular and digital cordless telephones; pagers; telephone answering devices; air-to-ground telecommunications; and satellite-based communications.

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What is a Mobile/Cell Phone?

A cellular phone is a portable telephone that does not use a wired connection. It connects to a wireless carrier network using radio waves.

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Cont… The Mobile phone or Cell phone is a long-

range, portable electronic device used for mobile communication.

In addition to the standard voice function of a telephone, current mobile phones can support many additional services such as

SMS for text messaging,

Email

Packet switching for access to the Internet, and

MMS for sending and receiving photos and video.

Most current mobile phones connect to a cellular network of base stations (cell sites),

which is in turn interconnected to the public switched telephone network (PSTN)

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How Cell Phone Works???

Wireless network carriers use a system of areasor "cells― served by radio communications.

The signal footprint of each radio antenna definesthe location and size of its cell.

As the mobile phone moves, the call is dropped bythe cell being exited and simultaneously picked up bythe cell being entered.

(handoff or handover concept)

The antennas can be mounted on freestandingtowers and poles etc.

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Cont…

Radio signals can be blocked by trees,buildings, hills and valleys.

A consumer needs two things to use a mobilecommunication service:

A handset (or mobile communications device)

And a phone service plan from a wireless networkcarrier or service provider.

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Frequency Spectrum

Frequency

The number of occurrences of a repeating event per unit time.

For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period – the interval between beats – is half a second (60 seconds).

Wavelength

It is the spatial period of the wave—the distance over which the wave's shape repeats.

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Typical Frequencies

• 88 MHZFM RADIO

• 200 MHZTV BROADCAST

• 900 MHZGSM PHONES

• 1.2 GHZGPS

• 1.8 GHZPCS PHONES

• 2.4 GHZBLUETOOTH

• 2.4 GHZWi-Fi

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Frequency Spectrum

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Frequency Spectrum

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Why Wireless Communication

1 Freedom from wires.

2 No bunch of wires running from here and there.

3 “Auto Magical” instantaneous communication without physical connection setup e.g.- Bluetooth, Wi-Fi.

4 Global coverage

5Communication can reach where wiring is infeasible or costly E.g. rural areas, buildings, battlefield, outer space.

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Types of Wireless Communications

RADIO TRANSMISSION:-

• Easily generated, Omni-directional , travel long distance, easily penetrates buildings.

• PROBLEMS:- Frequency dependent , relatively low bandwidth for data communication , tightly licensed by government.

MICROWAVE TRANSMISSION:-

• Widely used for long distance communication, relatively inexpensive.

• PROBLEMS:- Don’t pass through buildings, weather and frequency dependent.

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Cont…

INFRARED AND MILIMETER

WAVES:-

• Widely used for short range communication, unable to pass through solid objects , used for indoor wireless LANs, not for outdoors.

LIGHT WAVE TRANSMISSION:-

• Unguided optical signal such as laser, unidirectional, easy to install, no license required.

• PROBLEMS:- Unable to penetrate rain or thick fog , laser beam can be easily diverted by air.

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Adv. and disadv . of Wireless Communication

Advantages Working professionals can work and access Internet anywhere

and anytime without carrying cables or wires wherever they go. This also helps to complete the work anywhere on time and improves the

productivity.

A wireless communication network is a solution in areas where cables are impossible to install (e.g. hazardous areas, long distances etc.)

Wireless networks are cheaper to install and maintain

Disadvantages Has security vulnerabilities

High costs for setting the infrastructure

Unlike wired communication, wireless communication is influenced by physical obstructions, climatic conditions, interference from other wireless devices.

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Health Hazards of Handsets

Part of the radio waves emitted by a mobile telephone handset is absorbed by the human head.

The rate at which radiation is absorbed by the human body is measured by the Specific Absorption Rate (SAR), and its maximum levels for modern handsets have been set by governmental regulating agencies.

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Health Hazards of Handsets

Thermal Effects Dielectric heating, Most of the heating effect will occur at the surface of

the head, Some parts of the human head are more sensitive to

damage from increases in temperature.

Blood Brain Barrier Effects Swedish researchers have studied the effects of

microwave radiation on the rat brain. They found a leakage of albumin into brain via a permeated

blood-brain barrier.

Effects On Sleep A study showed that mobile phone signals affect

sleep patterns and possibly delay sleep onset during exposure.

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Current Wireless Systems

Cellular Systems

Wireless LANS

Satellite Systems

Paging Systems

PANs (Personal Area Networks), i.e. Bluetooth

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Electrical Sensitivity Effects

• Burning and tingling sensations in the skin of the head and extremities,

• Fatigue

• Sleep

• Disturbances

• Dizziness

• Loss of mental attention

• Headaches

• Tachycardia (heart palpitations)

• Disturbances of the digestive system

• Tumor risk

Possible Risks

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Be health conscious

For detailed knowing about the cell phone hazards, visit the cancer specific (cell phones and cancer risks) site below,

http://www.cancer.gov/about-cancer/causes-prevention/risk/radiation/cell-phones-fact-sheet

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Health Hazards of BS

Radiation is emitted by base stations.

Radiation emitted continuously and is more powerful at close quarters.

People living within 300 meters of GSM cell towers in rural areas or within 100m of base stations in urban areas complained

Fatigue

Headache

Sleep

Disruption

loss of memory

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Department of Computer Science 22

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