24-12-2012, 01:31 PM
WIRELESS AND MOBILE COMPUTING AND COMMUNICATION
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ABSTRACT
Undoubtedly, Wireless networks are changing the way people connect to each other and that very fast. This research work, cover some important details and necessary things which have to be known by anyone who is making use of any wireless devices. The seminar includes an introduction part and overview; how the wireless technology works skip through general types of wireless networks and their applications to wireless standards, to later on continue with wireless software and also with the wireless security. Due to the limitation on the scope of this research work more advance features on how the technology works were not included, but the basics of wireless computing were discussed.
INTRODUCTION
Wireless computing allows you to be free of cables. Wireless computing is using a mouse, keyboard and other input devices without any wires or cables connected to them. It also refers to connecting a computer to the Internet without any wires or cables; signals are transmitted over radio waves.
Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or the entire communication path. Some monitoring devices, such as intrusion alarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless.
AIMS AND OBJECTIVES
The aims and objective of this seminar is to explore the technology behind wireless computing the advancement so far and the expectation of the future wireless computing devices.
History of Wireless Computing
Guglielmo Marconi, the inventor of the wireless telegraph, is widely credited with developing wireless computing. He sent and received his first radio wave in 1895. Without radio waves, wireless computing would never have developed into what it is today. Even with Marconi receiving so much credit, no one person is responsible for inventing this form of computing.
The first wireless transmitters went on the air in the early 20th century using radiotelegraphy (Morse code). Later, as modulation made it possible to transmit voices and music via wireless, the medium came to be called "radio." With the advent of television, fax, data communication, and the effective use of a larger portion of the spectrum, the term "wireless" has been resurrected.
HOW WIRELESS WORKS
For individuals who are only occasional end users of atechnology there is little need to invest the time and energy to understand the underlyingtechnology. Also, if the device is a basic commodity item, such as a standard handheldcalculator or desktop telephone, there is little advantage to understanding the technology inorder to troubleshoot if the device should fail. The easiest and cheapest solution is simply tobuy another one.
Knowing how wireless workscan become an important tool in troubleshooting aWLAN that is not functioning correctly.
Although access points (APs) are no longer expensive items to purchase, often the problemwith a wireless network does not lie with the equipment but instead with the signal that isbeing transmitted and obstructions to that signal. Knowing how a wireless signal istransmitted can help in isolating and correcting problems.
In this chapter you explore the fundamentals of how wireless technology works. Althoughwireless transmissions can take place using infrared or radio waves as discussed later in this presentation radio transmission is the preferred method used today. Youbegin by looking at the principles behind sending voice and data through radio wavetransmissions. Next, you learn how radio frequency waves actually behave and how thisbehavior can be measured. Finally, you find out about one of the most important elementsof a radio wave system, namely the antenna.
ANTENNAS
One of the most important components of any wireless system is its antenna. Without antennas radio waves would be unable to travel long distances. In this section you explore how antennas work, their characteristics, and the various types of antennas.
Antenna Concepts
Radio waves are transmitted and received by using an antenna. An antenna is a copper wire or similar device that has one end up in the air and the other end connected to the ground or a grounded device. When transmitting, the radio waves are directed to strike this wire (the length of an antenna should be about 1⁄4 of the wavelength). This will set up electrical pressure (voltage) along the wire. This pressure will cause a small electrical current to flow up and down the wire. The voltage causes the electricity in the antenna to move back and forth at the same frequency as the radio waves. Broadcasting or sending out radio waves is accomplished by forcing the electricity in the antenna to move at the same frequency as the radio waves. An antenna is also used to pick up transmitted radio signals. The electricity in the receiving antenna moves back and forth in response to the radio signals reaching it. The motion causes a voltage that leads from the antenna into the receiver.
RADIO WAVE TRANSMISSION PRINCIPLES
Understanding the principles of radio wave transmission is important not only for troubleshootingwireless LANs but also to create a context for understanding wireless terminology. In thispresentation we would explore the fundamentals of radio waves and how they can transmit data.
What Are Radio Waves?
Traditional wired communications use copper wires or fiber optic cables to send and receivedata. Wireless transmissions, of course, do not use these or any other visible media. Instead,data travels on invisible radio waves.
WPAN (Wireless Private Area Network)
WPAN technologies enable users to establish ad hoc, wireless communications for devices(such as PDAs, cellular phones, or laptops) that are used within a personal operating space(POS). A POS is the space surrounding a person, up to a distance of 10 meters. Currently, thetwo key WPAN technologies are Bluetooth and infrared light. Bluetooth is a cable replacementtechnology that uses radio waves to transmit data to a distance of up to 30 feet. Bluetooth data can be transferred through walls, pockets, and briefcases. Technology development for Bluetoothis driven by the Bluetooth Special Interest Group (SIG), which published the Bluetooth version 1.0specification in 1999. Alternatively, to connect devices at a very close range (1 meter or less),users can create infrared links.To standardize the development of WPAN technologies, IEEE has established the 802.15working group for WPANs. This working group is developing a WPAN standard, based on theBluetooth version 1.0 specification. Key goals for this draft standard are low complexity, lowpower consumption, interoperability, and coexistence with 802.11 networks.”
WLAN (Wireless Local Area Network)
At this point in time, wireless connectivity solutions can be grouped into three main categories.All these use Radio Frequency (RF) technology to transmit data through the air. The first category,wireless local area networking (WLAN), transmits data between a wired network and a mobileuser or users. Its origins lie in the encrypted radio signals sent by allied operativesacross enemy lines during World War II. Referred to as “spread spectrum technology,” thewartime messages paved the way for the first computational wireless network, which was createdin 1971 at the University of Hawaii. The project, called ALOHNET, had seven computers set up onfour islands communicating with one central computer on Oahu, none of them using phone lines(Bautts, 2005). In a modern-day example of WLAN technology, businesses commonly issuenetwork-connected laptops with wireless cards to their employees to replace desktop computers.This allows their employees to be productive anywhere within the bounds of the corporatenetwork. It also encourages collaboration by giving them the ability to form ad hoc work groups. Incertain situations, it can provide employees with incentives to use their computers at home or incoffee shops, where they may do work outside of traditional work hours. In this case, because theemployees’ work time seeps into their leisure time, a perceived benefit for the employee (the useof a computer with wireless capabilities) becomes a very real benefit for the employerWireless LANs operate using a transceiver device to send and receive data.