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8/8/2019 12. Wireless Mobile Comm. - Copy
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WIRELESS, MOBILE COMMUNICATION
SUBMITTTED BY,
K.RANGANAYAKULU GUPTHA
E-mail: [email protected]&
B.VASUDEVA RAOE-mail: [email protected] BE-ECE,
MRR INSTITUTE OF TECHNOLOGY &
SCIENCES, UDAYAGIRI,
NELLORE (DT).
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ABSTRACT:
Wireless communications is a rapidly growing segment of the communications industry,
with the potential to provide high-speed high-quality information exchange between portable
devices located anywhere in the world. Potential applications enabled by this technology
include multimedia Internet-enabled cell phones, smart homes and appliances, automated
highway systems, video teleconferencing and distance learning, and autonomous sensor
networks, to name just a few. However, supporting these applications using wireless
techniques poses a significant technical challenge.
Mobile just means portable. A laptop is a mobile device, as is a PDA or a cell phone. A
desktop would be a mobile device if you had the inclination to carry it around with you. A
wireless device has some sort of network connectivity. A cell phone is wireless, and a laptop
or PDA would be wireless if they had a wireless modem. Similarly, applications are wireless
when they connect and exchange data with a network. One of the many reasons for
developing a cellular mobile telephone system and developing it in many cities is the
operational limitations of conventional telephone systems.
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WIRELESS, MOBILE COMMUNICATION
1) WIRELESS COMMUNICATION
INTRODUCTION:
Wireless communications are nothing new. Since the earlier days of civilization, various
forms of communication took place without the advantage of physical connectivity. In tribal
jungle environment drums were a primary means of communicating. Smoking signals are
also used as a limited distance form of communication. In the nineteenth century, light
beams were used for short haul communications, particularly in military contexts. Wireless
means transmitting signals over invisible radio waves instead of wires. Garage door openers
and television remote controls were the first wireless devices to become a part of everyday
life. Now the cordless keyboard and mouse, PDAs, and digital and cellular phones are
commonplace. Wireless technologies are used for things as simple as making a phone call or
as complex as space research applications.
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WIRELESS CAN BE DIVIDED INTO THESE CATEGRIES:
Fixed wireless-the operation of wireless devices in fixed locations, such as homes and
offices. An example will be equipment connected to the Internet via specialized modems.
Mobile wireless the use of wireless devices or systems aboard motorized, moving
vehicles; examples the automotive cell phone and personal communications services
Portable wirelessthe operation of autonomous, battery-powered wireless devices or
systems outside the office, home or vehicle; examples handheld cell phones
IR wireless the use of devices that convey data via infrared radiation. Example:
portable wireless devices that normally derive their power from batteries.
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ELECTROMAGNETIC SPECTRAM
RANGE OF FREQUENCIES AND THE ASSCIATED BAND CLASSIFICATION:
FERQUENCY BAND
30GHz Extremely high frequency(EHF)
RADIO BASED SYSTEMS:
As radio-based systems emerged, wireless communication became more readily
available and easier to use. An electric transmitter was used to reproduce sound waves and
modulate human speech onto a base band radio frequency. The radio wave carrying the
transmitted signal could travel greater distances, allowing far more reliability and
minimizing the relay process. In radio transmission, human speech must first be converted to
an electrical signal. This signal is analogous to the composition of the sound-pressure
changes produced by the human voice. Radio systems propagate information in the free-
space communication obviates some of the problems faced by other transmission systems.
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ADVANTAGES:
(1) Span bodies of water, such as lakes or rivers, where a cable facility would require special
treatment to prevent seepage onto the copper conductors.
(2) Overcome transmission obstacles posed by mountains and deep valleys, where cable
costs would be prohibitive to install and difficult to maintain.
(3) Bypass the basic interconnection to the telephone provider or post telephone and
telegraph company.
RADIO PROPAGATION:
In radio propagation when the signal is transmitted through an antenna device, the signal
will travel along the earths curvature. As the signal emanates in all directions, the energyfollows the earths curvature. In some cases, reflected power off the earths surface helps
achieve the desired result. At lower frequencies, the signal follows the curve of the earths
surface in what is typically called a ground wave.
SATELLITE RADIO COMMUNICATION:
In 1960 microwave radio signals were transmitted up into the atmosphere to a repeater
floating in space. Called satellite communication, the system was originally designed to
bounce radio waves off an artificial object that was orbiting the earth. An orbiting satellite
offers several distinct advantages. A Stronger signals can be obtained, and over very long
distance the transmission signal requires only a single repeater.
The satellite can be located in a polar, inclined or equatorial orbit. The orbit may be
either circular elliptical at different heights above the surface of the earth. The system
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provide impractical for commercial use, since several satellites were needed to provide
constant communication and the moving antenna equipment required the constant reaming of
dishes. Therefore, a circular orbit around the equator at a height of 22,300 miles was
selected. A satellite at this height takes 24 hours to orbit the earth, resulting in what looks
like a stationary object. In fact, this is called ageosynchronous orbit.
LIGHT BASED SYSTEM:
Another wireless transmission system that is both reliable and inexpensive has proved to
be less popular than radio-based systems is light based system. Infrared light has long been
used as a transmission medium for short-haul local communications. The primary advantagesof infrared systems are easily transportable, typically can be setup and operating with-in an
hour, and do not require expensive licenses or right-of way permits. For all these pulses, the
main disadvantages are the limited distance and limited bandwidth. In addition, infrared
transmissions are subject to even more fading and absorption than microwave systems.
A pinpoint-beam generator in the infrared (invisible) light spectrum operates at a
frequency range of 1012-1015 and a wavelength of 10-4-10-7 to produce high-speed
communications. What should also be understood is that in this context infrared is carried in
open air-waves. If a different medium, such as very pure glass (fiber) were used, the
spectrum of the light would be in the infrared range. It is the fiber that achieves the high-
speed, reliable transmission, since the impairments of the air are overcome on the glass. The
remote controllers for TV sets, radios, lights and other appliances are use infrared signaling.
But they have all the properties of infrared transmission. They can be used only for short
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distances and are highly directional (point to point), invisible light transmitters.
BENEFITS OF WIRELESS COMMUNICATION:
Wireless dramatically improves the convenience, reliability and timeliness of
communication by allowing people to:
Remain persistently connected with others regardless of anyone's location and without
being plugged into anything
Save time and money by shaving seconds off of regular tasks such as locating people,
scanning items and receiving mission-critical alerts
Conduct daily chores effortlessly via a conveniently pocket-sized PDA
Reap the benefits of a rapid pace of innovation in a fast-growing market full of vendors
scrambling to make people's lives easier
WIRELESS SECURITY:
Security is one of the biggest barriers to any kind of wireless initiativewhether it's
implementing a WLAN in a remote office or rolling out wireless handhelds with applicationcapabilities such as e-mail or CRM data. The mobile security vendors are a force to be
reckoned with in this space. The key for IT executives is to cut through the FUD and
determine the real risks to a wireless initiative and the intended benefits. Then the decision
becomes a simple risk management, cost-benefit equation.
CHALLENGES:
Wireless throughput is generally limited compared to the wired alternatives
Uncertainty as to which technologies will remain viable long-term. Each camp (CDMA
and GSM) has several iterations of high-speed wireless service, with carriers choosing
different versions and implementing them at different times. The situation prevents
customers from counting on universal access to a given service.
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Wireless security is lagging
Dropped connections reflect the inherent limitations of wireless signals easily obstructed
by physical barriers such as tunnels, mountains and buildings, as well as radio noise and the
absence of cellular towers in a given region
Small screens in PDAs and other wireless devices limit how much a user can view at
once
Short battery lifespans mean that users must be conscientious about charging their
batteries
RECENT IMPROVEMENTS:
Wireless LANs have improved in the area of security
Devices now have color screens, more memory and faster processors, which devices such
as BlackBerrys have incorporated into their newest designs
Cellular carriers now support IP packets, meaning data can pass over existing voice
networks
Many vendors, including Microsoft, Oracle and SAP, are building wireless functionality
into new versions of their software; on the hardware side, Intel's Centrino processor now
supplies built-in wireless support
Security is improving as vendors add security features to their wireless devices to
compensate for the security limitations inherent in many legacy protocols. 802.11b showed
upwith security and standards
2) MOBILE CELLULAR COMMUNICATION:
INTRODUCTION:
One of the many reasons for developing a cellular mobile telephone system and
developing it in many cities is the operational limitations of conventional telephone systems.
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LIMITATIONS OF CONVENTIONAL TELEPHONE SYSTEMS:
Limited service capability
Poor service performance
Inefficient spectrum utilization
FREQUENCY ALLOCATON:
The FCCs decision to choose 800 MHz was made because of severe spectrum
limitations at lower frequency bands. Therefore it was hard for the FCC to allocate a
spectrum in the lower portions of the 30-400 MHz and since the services of this band had
become so crowded. On the other hand mobile radio transmission cannot be applied at10
GHz because severe propagation loss, and rain activity make the medium improper for the
mobile communications. The mobile phone system operating at 900 & 1800MHz forGSM
and 800MHz forCDMA.
BLOCK DIAGRAM:
A BASIC CELLULAR SYSTEM:
1) MOBILE UNITS:
A mobile telephone unit contains a control unit, a transceiver, and an antenna system.
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drawing unclear. The hexagonal-shaped cells fit the planned area nicely, with no overlap
between the hexagonal cells. Today these hexagonal-shaped cells have already become a
widely promoted symbol for cellular mobile communication.
HEXAGONAL CELL SITES AND THE REAL SHAPES OF THEIR COVERAGES:
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BASE STATION:
Base stations transmit power levels from a few watts to 100 watts or more, depending on
the size of the region or "cell" that they are designed to service. Base station antennae are
typically about 20-30 cm in width and a meter in length, and a height of from 15 to 50 meters
a. These antennae emit RF beams that are typically very narrow in the vertical direction but
quite broad in the horizontal direction. Because of the narrow vertical spread of the beam, the
RF field intensity at the ground directly below the antenna is low.
RADIATION FROM BASE STATION:
BASE STATIONS OF A CITY:
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1) CIRCLULAR UNCOVERED CELL
SITE2) CIRCULAR OVERLAPPED CELL SITE
3) HAEXAGONAL CELL SITE 4) REAL CELL SITE
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OPERATION OF A CELLULAR SYSTEM:
Mobile unit initialization
Mobile originated call
Network originated call
Call termination
Handoff procedure
MAKING A CALL:
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CONCLUSION:
Wireless communication has entered the mainstream as vendors refine the throughput,
stability, security and affordability of an ever-growing range of supported wireless
applications. In the wireless world, your colleagues' whereabouts become totally transparent
as you remain persistently connected with one another in real-time even if some of your
colleagues are flying cross-country.
IT IS NEVERTHELESS TO SAY THE WORLD IS BECOME AS THE WIRELESS
WORLD.
BIBLIOGRAPHY:
1) William C.Y. Lee, MOBILE CELLULAR TELECOMMUNICATION SYSTEM,
McGraw Hill Book Company, 2002.
2) Behrouaz A. Forouzon, DATA COMMUNICATION AND NETWORKING, Tata
McGraw Hill Company, second edition, 2005.
3) Theodore S.Rappaport, WIRELESS. COMMUNICATION, PEARSON
EDUCATION, 2002
4) Regis J.bates, WIRELESS NETWORKED COMMUNICATIONS, McGraw Hill Book
Company, 1995.
5) http://wikimediafoundation.org/
6) http://en.wikipedia.org/wiki/Wireless
7) http://www.stanford.edu/class/ee359/
8) http://www.rfcafe.com/references/electrical/wireless_comm_specs.htm
9) http://www.cio.com/communications/edit/120701_abc_wireless.html
10) http://www.cio.com/technology/wireless/
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http://wikimediafoundation.org/http://en.wikipedia.org/wiki/Wirelesshttp://www.stanford.edu/class/ee359/http://www.rfcafe.com/references/electrical/wireless_comm_specs.htmhttp://www.cio.com/communications/edit/120701_abc_wireless.htmlhttp://www.cio.com/technology/wireless/http://wikimediafoundation.org/http://en.wikipedia.org/wiki/Wirelesshttp://www.stanford.edu/class/ee359/http://www.rfcafe.com/references/electrical/wireless_comm_specs.htmhttp://www.cio.com/communications/edit/120701_abc_wireless.htmlhttp://www.cio.com/technology/wireless/8/8/2019 12. Wireless Mobile Comm. - Copy
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