Abstract and full paper on WIFI ( WIRELESS FIDELITY ) - creativeworld9

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Thursday, April 14, 2011

Abstract and full paper on WIFI ( WIRELESS FIDELITY )



Technology is no longer judged by its technical brilliance, but by the return on investment (both tangible and intangible). This in turn, is dictated by the killer application for that technology. Wireless Networks fit into this because the technology has been around long enough and can provide enough benefits to be seriously considered for deployment.
At the enterprise, it provides communication support for mobile computing. It overcomes and, in fact, annihilates the physical limitation of wired networks in terms of adaptability to a variation in demand. Network connectivity in a company’s meeting room is a classic example. The number of users using that room would vary for different meetings
Mobility is another feature by wireless. Mobile users can be truly mobile, in that hey don’t need to be bound to their seats when connecting to the network. Mobility, however is not only associated with users, it’s also associated with the infrastructure itself
This leads to other provision of wireless, that of scalability. It really helps in extending your network. It also becomes important if an enterprise has a rented office and needs to shift to a new place. Wi-Fi, or wireless fidelity, is freedom: it allows you to connect to the internet from your couch at home, a bed in a hotel room, or a conference room at work without wires. It is a wireless technology like cell phones, Wi-Fi enabled computers send and receive data indoors and outdoors; anywhere within the range of the base station. And the best thing of all, Wi-Fi is fast. In fact, it’s several times faster than the fastest cable modem connection.

1. IEEE 802.11b Wireless Networking Overview
Approval of the IEEE 802.11 standard for wireless local area networking (WLAN) and rapid progress made toward higher data rates have put the promise of truly mobile computing within reach. While wired LANs have been a mainstream technology for at least fifteen years, WLANs are uncharted territory for most networking professionals.
 In September of 1999, the Institute of Electrical and Electronic Engineers (IEEE) ratified the specification for IEEE 802.11b, also known as Wi-Fi. IEEE 802.11b defines the physical layer and media access control (MAC) sub layer for communications across a shared, wireless local area network (WLAN).
            At the physical layer, IEEE 802.11b operates at the radio frequency of 2.45 gigahertz (GHz) with a maximum bit rate of 11 Mbps. It uses the direct sequence spread spectrum (DSSS) transmission technique. At the MAC sub layer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol.
A wireless station with a frame to transmit first listens on the wireless medium to determine if another station is currently transmitting (this is the carrier sense portion of CSMA/CA). If the medium is being used, the wireless station calculates a random back off delay. Only after the random back off delay elapses can the wireless station again listen for a transmitting station. By instituting a random back off delay, multiple stations that are waiting to transmit do not end up trying to transmit at the same time (this is the collision avoidance portion of CSMA/CA).  Collisions can occur and, unlike with Ethernet, they might not be detected by the transmitting nodes. Therefore, 802.11b uses a Request to Send (RTS)/Clear to Send (CTS) protocol with an Acknowledgment (ACK) signal to ensure that a frame is successfully transmitted and received.

There are two kinds of wireless networks:
a.         An ad-hoc, or peer-to-peer wireless network consists of a number of computers each equipped with a wireless networking interface card. Each computer can communicate directly with all of the other wireless enabled computers. They can share files and printers this way, but may not be able to access wired LAN resources, unless one of the computers acts as a bridge to the wired LAN using special software. (This is called "bridging")

Figure 1: Ad-Hoc or Peer-to Peer Networking.
Each computer with a wireless interface can communicate directly with all of the others.

b. A wireless network can also use an access point, or base station. In this type of network the access point acts like a hub, providing connectivity for the wireless computers. It can connect (or "bridge") the wireless LAN to a wired LAN, allowing wireless computer access to LAN resources, such as file servers or existing Internet Connectivity.
There are two types of access points:
i.          Dedicated hardware access points (HAP) such as Lucent's WaveLAN, Apple's Airport Base Station or WebGear's AviatorPRO. (See Figure 2). Hardware access points offer comprehensive support of most wireless features, but check your requirements carefully.
ii.         Software Access Points which run on a computer equipped with a wireless network interface card as used in an ad-hoc or peer-to-peer wireless network. (See Figure 1) The Vicomsoft InterGate suites are software routers that can be used as a basic Software Access Point, and include features not commonly found in hardware solutions, such as Direct PPPoE support and extensive configuration flexibility, but may not offer the full range of wireless features defined in the 802.11 standard.
With appropriate networking software support, users on the wireless LAN can share files and printers located on the wired LAN and vice versa. Vicomsoft's solutions support file sharing using TCP/IP.

Figure2: Hardware Access Point
Wireless connected computers using a Hardware Access Point.

Figure3:  Software Access Point
 Wireless connected computers using a Software Access Point.

How can I use a wireless network to share an Internet connection?
Once you realize that wireless cards are analogous to Ethernet cards and that empty space is analogous to Ethernet cabling, the answer to this question becomes clear. To share an Internet connection across a LAN you need two things:
•          an Internet sharing hardware device or software program
•          a LAN
If your LAN is wireless, the same criteria apply. You need a hardware or software access point and a wireless LAN. Any computer equipped with a wireless network card running suitable Internet sharing software can be used as a software access point. (See Figure 4) A number of vendors offer hardware access points.
A hardware access point may provide Internet Sharing capabilities to Wired LAN computers, but does not usually provide much flexibility beyond very simple configurations. (See Figure 5)

Figure 4: Software Access Point with Internet.
Wireless connected computers using a Software Access Point for shared Internet access.

Figure 5: Hardware Access Point with Internet.

Wireless connected computers using a Hardware Access Point for shared Internet access.

If I have more than one hardware access point, how can I share a single Internet connection?
If an existing wired LAN already has an Internet connection, then the hardware access points simply connect to your LAN and allow wireless computers to access the existing Internet connection in the same way as wired LAN computers.

IEEE 802.11:-
Wireless networking hardware requires the use of underlying technology that deals with radio frequencies as well as data transmission. The most widely used standard is 802.11 produced by the Institute of Electrical and Electronic Engineers (IEEE). This is a standard defining all aspects of Radio Frequency Wireless networking
A wireless computer can "roam" from one access point to another, with the software and hardware maintaining a steady network connection by monitoring the signal strength from in-range access points and locking on to the one with the best quality. Usually this is completely transparent to the user; they are not aware that a different access point is being used from area to area. Some access point configurations require security authentication when swapping access points, usually in the form of a password dialog box.
Access points are required to have overlapping wireless areas to achieve this as can be seen in the following diagram:

Figure6: Roaming.
A user can move from Area 1 to Area 2 transparently. The Wireless networking hardware automatically swaps to the Access Point with the best signal.

Not all access points are capable of being configured to support roaming. Also of note is that any access points for a single vendor should be used when implementing roaming, as there is no official standard for this feature.

          You get greater mobility. Since you're un ethered, you can move around with your laptop, and as long as you stay within range of your access point, you won't lose your connection. (You can usually rove about 75 to 150 feet from the access point if you're indoors; farther if you're outdoors.) So, go ahead and send e-mail while you lounge on the deck, or surf the web from the kitchen.
          You get quick, easy installation. There are no wires to fish through walls or run along baseboards, so you won't need to drill holes in your floors or drywall. Because of this, a Wi-Fi network can be set up in a matter of minutes (not including the time it takes to configure the security measures.
          It's fairly fast. For providing such serious gains in convenience and ease of installation, Wi-Fi doesn't require a significant tradeoff in speed. The version of Wi-Fi most recently implemented for the majority of consumer electronics and home computers — known to engineers as IEEE 802.11g — transfers data in the 2.4GHz frequency band, at speeds up to 54 Megabits per second. That's almost five times faster than the previous version, and faster than a wired Ethernet network (10Base-T). Plus, the current standard is backwards-compatible with the previous one (the still-popular 802.11b), so if you already own older gear, your brand-new Wi-Fi hardware will work with it to deliver up to 11Mbps data transfer (the maximum speed of the 11b standard).

Disadvantages of Wi-FI
•          The 802.11b and 802.11g flavors of Wi-Fi use the 2.4 Ghz spectrum, which is crowded with other devices such as Bluetooth, microwave ovens, cordless phones, or video sender devices, among many others. This may cause a degradation in performance. Other devices which use microwave frequencies such as certain types of cell phones can also cause degradation in performance.
•          Power consumption is fairly high compared to other standards, making battery life and heat a concern.
•          Not always configured properly by user. Commonly uses WEP (Wired Equivalent Privacy) protocol for protection, though has been shown to be easily breakable. Newer wireless solutions are slowly providing support for the superior WPA (Wi-Fi Protected Access) protocol, though many systems still employ WEP.

Today, Wi-Fi is mainly used for making easy connections between a home computer and the Internet. But soon, we'll see even friendlier and easier solutions for all kinds of wireless transmissions — including streaming of music and video. This article is just a first step toward understanding Wi-Fi. Keep an eye on the Advisor as we continue to keep you up-to-date on this hot technology!

1. Data over wireless networks             -Gilbert Held 
2. Electronics for you (magazine) June 2003 & February 2003
3. Electronics today (magazine) March 2003
4. A Technical tutorial on the IEEE 802.11 protocol - Pablo Brenner
Abstract and full paper on WIFI ( WIRELESS FIDELITY ) Reviewed by creativeworld9 on 10:40 AM Rating: 5  WIRELESS FIDELITY ABSTRACT Technology is no longer judged by its technical brilliance, but by...


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