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17-01-2010, 10:33 AM
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wifi seminar report

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ABSTRACT
Wi-Fi, which stands for Wireless Fidelity, is a radio technology that networks computers so they connect to each other and to the Internet without wires .Users can share documents and projects, as well as an Internet connection among various computer stations, and easily connect to a broadband Internet connection while traveling. By using a Wi-Fi network, individuals can network desktop computers, laptops and PDAs and share networked peripherals like servers and printers.
A Wi-Fi network operates just like a wired network, without the restrictions imposed by wires. Not only does it enable users to move around be mobile at home and at work , it also provides easy connections to the Internet and business networks while traveling .The technologies used in this field are one of the best in the wireless space . It is fairly easy to set up a Wi-Fi enabled network at home or a small office.

INTRODUCTION
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 at a conference room at work without wires. How? Wi-Fi is a wireless technology like a cell phone. Wi-Fi enabled computers send and receives data indoors and out: anywhere within the range of a base station. And the best thing of all, itâ„¢s fast. In fact, itâ„¢s several times faster than the fastest cable modem connection.
However, you only have true freedom to be connected anywhere if your computer is configured with a Wi-Fi CERTIFIED radio (a PC Card or similar device). Wi-Fi certification means that you will be able to connect anywhere there are other Wi-Fi CERTIFIED products-whether you are at home, the office or corporate campus, or in airports, hotels, coffee shops and other public areas equipped with a Wi-Fi access available.
The Wi-Fi certified logo is your only assurance that the product has met rigorous interoperability testing requirements to assure products from different vendors will work together .The Wi-Fi CERTIFIED logo means that itâ„¢s a safe buy.
Wi-Fi certification comes from the Wi-Fi Alliance, a nonprofit international trade organization that tests 802.11-based wireless equipment to make sure it meets the Wi-Fi standard and works with all other manufacturersâ„¢ Wi-Fi equipment on the market .Thanks to the Wi-Fi Alliance, you donâ„¢t have to read the fine print or study technicaljournals:if it says Wi-Fi, it will work.
WIRELESS NETWORKING COMPONENTS
Wi-Fi is a friendly term for IEEE 802.11b Ethernet standard. It operates in the unlicensed frequency band of 2.4 Ghz with a maximum data rate of 11 Mbps.
IEEE 802.11b wireless networking consists of the following components:
Stations
A station (STA) is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client. Wireless clients can communicate directly with each other or through a wireless access point (AP). Wireless clients are mobile.

Wireless Access Points
a. A wireless AP is a wireless network node that acts as a bridge between STAs and a wired network. A wireless AP contains:
b. At least one interface that connects the wireless AP to an existing wired network (such as an Ethernet backbone).
c. A wireless network device with which it creates wireless connections with STAs.
d. IEEE 802.1D bridging software, so that it can act as a transparent bridge between the wireless and wired networks.
The wireless AP is similar to a cellular phone network's base station. Wireless clients communicate with both the wired network and other wireless clients through the wireless AP. Wireless APs are not mobile and act as peripheral bridge devices that extend a wired network.


OPERATION MODES
IEEE 802.11 defines two operating modes: Ad hoc mode and Infrastructure mode.
AD HOC MODE: In ad hoc mode, also known as peer-to-peer mode, wireless clients communicate directly with each other (without the use of a wireless AP). Two or more wireless clients who communicate using ad hoc mode form an Independent Basic Service Set (IBSS). Ad hoc mode is used to connect wireless clients when a wireless AP is not present.

INFRA STRUCTURE MODE
: In infrastructure mode, there is at least one wireless AP and one wireless client. The wireless client uses the wireless AP to access the resources of a wired network. The wired network can be an organization intranet or the Internet, depending on the placement of the wireless AP.

A single wireless AP that supports one or multiple wireless clients is known as a Basic Service Set (BSS). A set of two or more wireless APs that are connected to the same wired network is known as an Extended Service Set (ESS). An ESS is a single logical network segment (also known as a subnet), and is identified by its Service Set Identifier (SSID). If the available physical areas of the wireless APs in an ESS overlap, then a wireless client can roam, or move from one location (with a wireless AP) to another (with a different wireless AP) while maintaining Network layer connectivity.

RADIO TECHNOLOGY

Wi-Fi network uses radio technology called IEEE 802.11b to provide secure, fast, reliable, wireless connectivity. 11b defines the physical layer and media access control (MAC) sublayer 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 sublayer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol
DIRECT SEQUENCE SPREAD SPECTRUM
Direct Sequence is the best known Spread Spectrum Technique. A DSSS transmitter converts an incoming data stream into a symbol stream where each symbol represents a group of one or more bits. Using a phase varying modulation technique, DSSS transmitter modulates or multiplies each symbol with a noise like code called Ëœchipâ„¢ sequence. This is also called processing gain. The multiplication operation in a DSSS transmitter artificially increases the used bandwidth based on the length of chip sequence.

When receiving the DSSS signal, a matched filter correlator is used. The correlator removes the PN sequence and recovers the original data stream. As shown in figure, the PN sequence spreads the transmitted bandwidth of the resulting signal (thus the term, spread spectrum) and reduces peak power. Note however, that total power is unchanged. Upon reception, the signal is correlated with the same PN sequence to reject narrow band interference and recover the original binary data (Fig. 5b). Regardless of whether the data rate is 1, 2, 5.5, or 11 Mbps, the channel bandwidth is about 20 MHz for DSSS systems. Therefore, the ISM band will accommodate up to three non-overlapping channels

CARRIER SENSE MULTIPLE ACCESS/COLLISION AVOIDANCE
The basic access method for 802.11 is the Distributed Coordination Function (DCF) which uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA). This requires each station to listen for other users. If the channel is idle, the station may transmit. However if it is busy, each station waits until transmission stops, and then enters into a random back off procedure. This prevents multiple stations from seizing the medium immediately after completion of the preceding transmission.


Packet reception in DCF requires acknowledgement as shown in figure. The period between completion of packet transmission and start of the ACK frame is one Short Inter Frame Space (SIFS). ACK frames have a higher priority than other traffic. Fast acknowledgement is one of the salient features of the 802.11 standard, because it requires ACKs to be handled at the MAC sublayer.
Transmissions other than ACKs must wait at least one DCF inter frame space (DIFS) before transmitting data. If a transmitter senses a busy medium, it determines a random back-off period by setting an internal timer to an integer number of slot times. Upon expiration of a DIFS, the timer begins to decrement. If the timer reaches zero, the station may begin transmission. However, if the channel is seized by another station before the timer reaches zero, the timer setting is retained at the decremented value for subsequent transmission.
OPERATION BASICS
When a wireless adapter is turned on, it begins to scan across the wireless frequencies for wireless APs and other wireless clients in ad hoc mode. Assuming that the wireless client is configured to operate in infrastructure mode, the wireless adapter chooses a wireless AP with which to connect. This selection is made automatically by using SSID and signal strength and frame error rate information. Next, the wireless adapter switches to the assigned channel of the selected wireless AP and negotiates the use of a port. This is known as establishing an association.
If the signal strength of the wireless AP is too low, the error rate too high, or if instructed by the operating system (in the case of Windows XP), the wireless adapter scans for other wireless APs to determine whether a different wireless AP can provide a stronger signal or lower error rate. If such a wireless AP is located, the wireless adapter switches to the channel of that wireless AP and negotiates the use of a port. This is known as reassociation.
Reassociation with a different wireless AP can occur for several reasons. The signal can weaken as either the wireless adapter moves away from the wireless AP or the wireless AP becomes congested with too much traffic or interference. By switching to another wireless AP, the wireless adapter can distribute the load to other wireless APs, increasing the performance for other wireless clients. You can achieve contiguous coverage over large areas by placing your wireless APs so that their signal areas overlap slightly. As a wireless client roams across different signal areas, it can associate and reassociate from one wireless AP to another, maintaining a continuous logical connection to the wired network.
RANGE IN A Wi-Fi NETWORK
One of the factors that affect the range of a Wi-Fi network is the distance of the client devices to your base station. In an open area with no walls, furniture or interfering radio devices you may be able to get a range of 500 feet or more from your base station to the Wi-Fi equipped computer. In fact you could get a signal from up to a mile away depending on the antennas you use and environmental conditions.
Many base stations can also act as relay stations for your network. For example if you locate one Wi-Fi equipped computer 100 feet away from your base station, another Wi-Fi computer 100 feet away in another direction and then position your base station in the middle, you can create a network with a range of 200 feet from the Wi-Fi computer to the other.
Wi-Fi, or IEEE 802.11b, speed decreases the farther you move away from your network. For example when you are close to the base station your Wi-Fi computer should be able to get the full 11Mbps data rate. Move farther away, and depending on the environment, the data rate will drop to 2Mbps, and finally to 1Mbps. But getting just 1Mbps throughput is still a perfectly acceptable performance level. 1Mbps is faster than most DSL and cable connections, which means itâ„¢s still a satisfactory high speed transmission if you are sending and receiving e-mail, cruising the internet or just performing data entry tasks from a mobile computer.

AREA
Maximum Range
Range at 11Mbps
Outdoors/open Space with standard antennae
750-1000 feet
150-350 feet
Office/light industrial setting
250-350 feet
100-150 feet
Residential setting
125-200 feet 60-80 feet

SECURITY
Because wireless is a shared medium, everything that is transmitted or received over a wireless network can be intercepted. Encryption and authentication are always considered when developing a wireless networking system. The goal of adding these security features is to make wireless traffic as secure as wired traffic. The IEEE 802.11b standard provides a mechanism to do this by encrypting the traffic and authenticating nodes via the Wired Equivalent Privacy (WEP) protocol.
The IEEE 802.11 standard defines the following mechanisms for wireless security:
a. Authentication through the open system and shared key authentication types
b. Data confidentiality through Wired Equivalent Privacy (WEP)
Open system authentication does not provide authentication, only identification using the wireless adapter's MAC address. Open system authentication is used when no authentication is required. Some wireless APs allow the configuration of the MAC addresses of allowed wireless clients. However, this is not secure because the MAC address of a wireless client can be spoofed.
Shared key authentication verifies that an authenticating wireless client has knowledge of a shared secret. This is similar to preshared key authentication in Internet Protocol security (IPsec). The 802.11 standard currently assumes that the shared key is delivered to participating STAs through a secure channel that is independent of IEEE 802.11. In practice, this secret is manually configured for both the wireless AP and client. Because the shared key authentication secret must be distributed manually, this method of authentication does not scale to a large infrastructure mode network (for example, corporate campuses and public places, such as malls and airports). Additionally, shared key authentication is not secure and is not recommended for use.
WIRED EQUIVALENT PRIVACY (WEP)
WEP utilizes RC42, a symmetric algorithm known as a stream cipher, for encryption. A symmetric algorithm is one that relies on the concept of a single shared key (as opposed to a public key) that is used at one end to encrypt plaintext (the data) into ciphertext (the encrypted data), and at the other end to decrypt it - convert the ciphertext back to plaintext. Thus, the sender and the receiver share the same key, and it must be kept secret.
Stream ciphers encrypt data as it is received, as opposed to block ciphers that collect data in a buffer and then encrypt it a block at a time. Stream ciphers are tempting to use for applications requiring hardware implementation (i.e. wireless LAN cards), because they can be implemented very efficiently in silicon.
WEP VULNARABILITIES
Not long after WEP was developed, a series of independent research studies began to expose its cryptographic weaknesses. Even with WEP enabled, third parties with a moderate amount of technical know-how and resources could breach WLAN security. Three key difficulties were identified:
1. WEP uses a single, static shared key. It remains the same unless a network administrator manually changes it on all devices in the WLAN, a task that becomes ever more daunting as the size of the WLAN increases.
2. At the time of its introduction, WEP employed a necessarily short 40-bit encryption scheme. The scheme was the maximum allowed by US export standards at that time. In 1997, the US government deemed the export of data cryptography to be as threatening to national security as the export of weapons of mass destruction. By necessity, Wi-Fi security had to be weak if the specification was to be adopted as an international standard and if products were to be freely exported.
3. Other technical problems contributed to its vulnerability, including attacks that could lead to the recovery of the WEP key itself.
Together, these issues exposed that WEP was not sufficient for enterprise-class security.
VIRTUAL PRIVATE NETWORKS (VPNs)
Virtual Private Network technology (VPN) has been used to secure communications among remote locations via the Internet since the 1990s. A familiar and already widely used technology in the enterprise, it can readily be extended to Wi-Fi WLAN segments on existing wired networks. Although VPNs were originally developed to provide point-to-point encryption for long Internet connections between remote users and their corporate networks, they have recently been deployed in conjunction with Wi-Fi WLANs. When a WLAN client uses a VPN tunnel, communications data remains encrypted until it reaches the VPN gateway, which sits behind the wireless AP. Thus, intruders are effectively blocked from intercepting all network communications. Since the VPN encrypts the entire link from the PC to the VPN gateway in the heart of the corporate network, the wireless network segment between the PC and the AP is also encrypted. This is why VPNs have been recommended to help secure Wi-Fi.
While VPNs are generally considered an enterprise solution, integrated products that offer VPN pass-through connections, firewalls and routers are available to accommodate telecommuters who work from home. Although they provide excellent security, VPNs are not self-managing. User credentials and, often, VPN software must be distributed to each client. However, when properly installed, VPNs extend the high level of security they provide on wired networks to WLANs. In fact, some Wi-Fi vendors themselves have utilized VPNs in networks to secure their own internal Wi-Fi networks.
Wi-Fi PROTECTED ACCESS
Wi-Fi Protected Access is a specification of standards-based, interoperable security enhancements that strongly increase the level of data protection and access control for existing and future wireless LAN systems. Designed to run on existing hardware as a software upgrade, Wi-Fi Protected Access is derived from and will be forward-compatible with the upcoming IEEE 802.11i standard. When properly installed, it will provide wireless LAN users with a high level of assurance that their data will remain protected and that only authorized network users can access the network.
Wi-Fi Protected Access had several design goals, i.e.,: be a strong, interoperable, security replacement for WEP, be software upgradeable to existing Wi-Fi CERTIFIED products, be applicable for both home and large enterprise users, and be available immediately. To meet these goals, two primary security enhancements needed to be made. Wi-Fi Protected Access was constructed to provide an improved data encryption, which was weak in WEP, and to provide user authentication, which was largely missing in WEP.
Enhanced Data Encryption through TKIP
To improve data encryption, Wi-Fi Protected Access utilizes its Temporal Key Integrity Protocol (TKIP). TKIP provides important data encryption enhancements including a per-packet key mixing function, a message integrity check (MIC) named Michael, an extended initialization vector (IV) with sequencing rules, and a re-keying mechanism. Through these enhancements, TKIP addresses all WEPâ„¢s known vulnerabilities.
Enterprise-level User Authentication via 802.1x and EAP
WEP has almost no user authentication mechanism. To strengthen user authentication, Wi-Fi Protected Access implements 802.1x and the Extensible Authentication Protocol (EAP). Together, these implementations provide a framework for strong user authentication. This framework utilizes a central authentication server, such as RADIUS, to authenticate each user on the network before they join it, and also employs mutual authentication so that the wireless user doesnâ„¢t accidentally join a rogue network that might steal its network credentials.

ADVANTAGES

a. flexible: With a wireless network you and your staff can have uninterrupted access to people, information and tools as you and they move through the workplace with your mobile PC.
b. responsive: As you change your business operations your wireless network can change with you.
c. customized: Your wireless network can be configured the way you want it.-even combined with your current wired network.
d. fast: From 11 to 54 Mbps throughput and advanced roaming capabilities provide reliable access to e-mail, the Internet, file sharing and other network resources away from the desk.
e. cost-effective: Expand and extend your existing network by simply adding more adapters and access points. Planning is a no brainier as you need to buy only what you need.
f. secure: Current standards utilizes 64- and 128-bit WEP encryption and help guard the network from intruders and protect data in transit. Add in technology and you have increased WLAN protection important for mission-critical data.
In addition to the hard benefits of increased efficiency, productivity, manageability and cost savings, wireless networks will certainly make a ËœThis is a technology savvy companyâ„¢ statement to the world.
LIMITATIONS
o It has a limited bandwidth of about 83.5 MHz.
o Frequency spectrum used by IEEE 802.11b is shared by many other systems like microwave ovens, cordless phones etc. This frequency sharing causes interference problem.
o Security techniques are not reliable yet.

FUTURE TRENDS
IEEE 802.11a
The 802.11a supplement to 802.11 was published in 1999. It uses Orthogonal Frequency Division Multiplexing (OFDM) to provide data rates to 54 Mbps in the 5 GHz U-NII bands. In addition to being uncrowded, more spectrums in the U-NII bands allow room for 12 non-overlapping channels, compared to just three in the 2.4 GHz ISM bands. Both of these factors make operating in the U-NII bands far less prone to interference.
However, at 5 GHz, more path loss occurs due to increased absorption of the RF energy by walls and other solid objects. This, combined with a decrease in range due to the higher data rates, may require that more access points be installed to effectively cover an area comparable to that of 802.11b.
IEEE 802.11g
The 802.11g task group is working on a supplement to the 802.11 standard that defines a technology for operation at 2.4 GHz that offers higher data rates (up to 22 Mbps) using OFDM, while remaining backwards compatible to 802.11b. In addition, the supplement will specify even higher data rates using two different methods (up to 33 Mbps using PBCC-DSSS and up to 54 Mbps using CCK-OFDM) which manufactures can optionally incorporate. When compared to 802.11a, 802.11g offers the advantages of lower cost, backwards compatibility to existing 802.11b equipment, and less path loss than 802.11a. This translates into higher data rates for a given range, or increased range for a given data rate.

CONCLUSION
Wi-Fi provides freedom: freedom to physically move around your home or business and still stay connected to the Internet or local network; freedom to grow and move an office or business without having to install new cables and wires; freedom to be connected while traveling and on the road. Wireless HotSpots (airports, hotels, coffee shops, convention centers and any other place where someone can connect to a wireless network) are being installed worldwide. All this means Wi-Fi truly does provide unprecedented freedom. Plus, it is cool, and it is fun “ as those in the know say, Once you go wireless, you will never want to use a cable again.
There are real and measurable benefits to using a wireless network versus a standard wired network. For a home installation customer, the greatest benefit is that there are no wites needed: you donâ„¢t need to drill holes in walls and floors; you donâ„¢t need to drag cables or hide them under rugs. One Wi-Fi access point can provide network access for any typically sized home.And if you live in a rental or a historical building, you may not be allowed to drill holes-that makes wireless your only solution.
Wi-Fi use is growing fast in homes, public access areas and businesses- both large and small. The Wi-Fi Alliance is active with many industry organizations and is working closely with manufacturers to make sure that existing Wi-Fi gear is compatible with wireless technologies developed in future.

REFERENCES
1. Wi-Fi: Whatâ„¢s next, Paul S.Henry, Hui Luo, IEEE Communications Magazine, December 2002.
2. Wireless LANs and smart homes, Mahmoud Nagnshineh, IEEE Wireless Communications, August 2002.
3. Why Wi-Fi is so hot, Data Quest, June 2003.
4. Overview of IEEE 802.11 Security, http://www.techonline.com.
5. Wireless Networking Handbook, Jim Geier.
6. Wireless Digital Communications, Dr. Kamilo Feher.


CONTENTS
1. INTRODUCTION 1

2. WIRELESS NETWORKING COMPONENTS 2
3. OPERATION MODES 4

4. RADIO TECHNOLOGY 6
5. SECURITY 13
6. ADVANTAGES 18
7. LIMITATIONS 19
8. FUTURE TRENDS 20
9. CONCLUSION 21
10. REFERENCES 22

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11-02-2010, 09:06 PM
Post: #2
RE: wifi seminar report

.doc  Wi-Fi (Wireless Fidelity).doc (Size: 228.5 KB / Downloads: 394)

ABSTRACT
Wi-Fi, which stands for "Wireless Fidelity", is a radio technology that networks computers so they connect to each other and to the Internet without wires .Users can share documents and projects, as well as an Internet connection among various computer stations, and easily connect to a broadband Internet connection while traveling. By using a Wi-Fi network, individuals can network desktop computers, laptops and PDAs and share networked peripherals like servers and printers.
A Wi-Fi network operates just like a wired network, without the restrictions imposed by wires. Not only does it enable users to move around be mobile at home and at work , it also provides easy connections to the Internet and business networks while traveling The technologies used in this field are one of the best in the wireless space . It is fairly easy to set up a Wi-Fi enabled network at home or a small office.
INTRODUCTION
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 at a conference room at work without wires. How Wi-Fi is a wireless technology like a cell phone. Wi-Fi enabled computers send and receives data indoors and out: anywhere within the range of a base station. And the best thing of all, it's fast. In fact, it's several times faster than the fastest cable modem connection.
¢ However, you only have true freedom to be connected anywhere if your computer is configured with a Wi-Fi CERTIFIED radio (a PC Card or similar device). Wi-Fi certification means that you will be able to connect anywhere there are other Wi-Fi CERTIFIED products-whether you are at home, the office or corporate campus, or in airports, hotels, coffee shops and other public areas equipped with a Wi-Fi access available.
The Wi-Fi certified logo is your only assurance that the product has met rigorous interoperability testing requirements to assure products from different vendors will work together The Wi-Fi CERTIFIED logo means that it's a "safe" buy.
Wi-Fi certification comes from the Wi-Fi Alliance, a nonprofit international trade organization that tests 802.11-based wireless equipment to make sure it meets the Wi-Fi standard and works with all other manufacturers' Wi-Fi equipment on the market Thanks to the Wi-Fi Alliance, you don't have to read the fine print or study technicaljournals:if it says Wi-Fi, it will work.
WIRELESS NETWORKING COMPONENTS
Wi-Fi is a friendly term for IEEE 802.11b Ethernet standard. It operates in the unlicensed frequency band of 2.4 Ghz with a maximum data rate of 11 Mbps.
IEEE 802.11b wireless networking consists of the following components:
Stations
A station (STA) is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client. Wireless clients can communicate directly with each other or through a wireless access point (AP). Wireless clients are mobile.



Figurel. Wireless station









¢ Wireless Access Points
A wireless AP is a wireless network node that acts as a bridge between STAs and a wired network. A wireless AP contains:
¢ At least one interface that connects the wireless AP to an existing
wired network (such as an Ethernet backbone).

A wireless network device with which it creates wireless connections with STAs. ¢ IEEE 802.1D bridging software, so that it can act as a transparent bridge between the wireless and wired networks.

The wireless AP is similar to a cellular phone network's base station. Wireless clients communicate with both the wired network and other wireless clients through the wireless AP. Wireless APs are not mobile and act as peripheral bridge devices that extend a wired network.
OPERATION MODES
IEEE 802.11 defines two operating modes: Ad hoc mode and Infrastructure mode.

AD HOC MODE: In ad hoc mode, also known as peer-to-peer mode, wireless clients communicate directly with each other (without the use of a wireless AP). Two or more wireless clients who communicate using ad hoc mode form an Independent Basic Service Set (IBSS). Ad hoc mode is used to connect wireless clients when a wireless AP is not present.



Figure 3: The ad-hoc network structure in the 802.11 protocol

INFRA STRUCTURE MODE: In infrastructure mode, there is at least one wireless AP and one wireless client. The wireless client uses the wireless AP to access the resources of a wired network. The wired network can be an organization intranet or the Internet, depending on the placement of the wireless AP.





Figure 4: The infrastructure network structure in the 802.11 protocol

A single wireless AP that supports one or multiple wireless clients is known as a Basic Service Set (BSS). A set of two or more wireless APs that are connected to the same wired network is known as an Extended Service Set (ESS). An ESS is a single logical network segment (also known as a subnet), and is identified by its Service Set Identifier (SSID). If the available physical areas of the wireless APs in an ESS overlap, then a wireless client can roam, or move from one location (with a wireless AP) to another (with a different wireless AP) while maintaining Network layer connectivity.
RADIO TECHNOLOGY
Wi-Fi network uses radio technology called IEEE 802.11b to provide secure, fast, reliable, wireless connectivity. 11b defines the physical layer and media access control (MAC) sublayer 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 sublayer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol


DIRECT SEQUENCE SPREAD SPECTRUM
Direct Sequence is the best known Spread Spectrum Technique. A DSSS transmitter converts an incoming data stream into a symbol stream where each symbol represents a group of one or more bits. Using a phase varying modulation technique, DSSS transmitter modulates or multiplies each symbol with a noise like code called 'chip' sequence. This is also called processing gain. The multiplication operation in a DSSS transmitter artificially increases the used bandwidth based on the length of chip sequence.
When receiving the DSSS signal, a matched filter correlator is used. The correlator removes the PN sequence and recovers the original data stream. As shown in figure, the PN sequence spreads the transmitted bandwidth of the resulting signal (thus the term, "spread spectrum") and reduces geak power. Note however, that total power is unchanged. Upon reception, the signal is correlated with the same PN sequence to reject narrow band interference and recover the original binary data (Fig. 5b). Regardless of whether the data rate is 1, 2, 5.5, or 11 Mbps, the channel bandwidth is about 20 MHz for DSSS systems. Therefore, the ISM band will accommodate up to three non-overlapping channels



Figure 6a. Effect of PN Sequence on Transmit Spectrum



Figure 6b. Received Signal is Correlated with PN to Recover Data and Reject
Interference

2.4000 Ch-1 Ch<6 Ch.W 2.483!
GHz GH2


Figure 7. Three Non-Overlapping DSSS Channels in the ISM Band
CARRIER SENSE MULTIPLE ACCESS/COLLISION AVOIDANCE
The basic access method for 802.11 is the Distributed Coordination Function (DCF) which uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA). This requires each station to listen for other users. If the channel is idle, the station may transmit. However if it is busy, each station waits until transmission stops, and then enters into a random back off procedure. This prevents multiple stations from seizing the medium immediately after completion of the preceding transmission.


DIFS
”o
Src Data
i
Dest SIFS”PH l<3-
Other DIFS -O «a i>J Contention Window
IIIII / NpXt MVW
j, Defer Aeeew ^ Backoff after Defer





Figure 8. CSMA/CD Back-off Algorithm

Packet reception in DCF requires acknowledgement as shown in figure. The period between completion of packet transmission and start of the ACK frame is one Short Inter Frame Space (SIFS). ACK frames have a higher priority than other traffic. Fast acknowledgement is one of the salient features of the 802.11 standard, because it requires ACKs to be handled at the MAC sublayer.
Transmissions other than ACKs must wait at least one DCF inter frame space (DIFS) before transmitting data. If a transmitter senses a busy medium, it determines a random back-off period by setting an internal timer to an integer number of slot times. Upon expiration of a DIFS, the timer begins to decrement. If the timer reaches zero, the station may begin transmission.
However, if the channel is seized by another station before the timer reaches zero, the timer setting is retained at the decremented value for subsequent transmission.


OPERATION BASICS
When a wireless adapter is turned on, it begins to scan across the wireless frequencies for wireless APs and other wireless clients in ad hoc mode. Assuming that the wireless client is configured to operate in infrastructure mode, the wireless adapter chooses a wireless AP with which to connect. This selection is made automatically by using SSID and signal strength and frame error rate information. Next, the wireless adapter switches to the assigned channel of the selected wireless AP and negotiates the use of a port. This is known as establishing an association.

If the signal strength of the wireless AP is too low, the error rate too high, or if instructed by the operating system (in the case of Windows XP), the wireless adapter scans for other wireless APs to determine whether a different wireless AP can provide a stronger signal or lower error rate. If such a wireless AP is located, the wireless adapter switches to the channel of that wireless AP and negotiates the use of a port. This is known as reassociation.
Reassociation with a different wireless AP can occur for several reasons. The signal can weaken as either the wireless adapter moves away from the wireless AP or the wireless AP becomes congested with too much traffic or interference. By switching to another wireless AP, the wireless adapter can distribute the load to other wireless APs, increasing the performance for other wireless clients. You can achieve contiguous coverage over large areas by placing your wireless APs so that their signal areas overlap slightly. As a wireless client roams across different signal areas, it can associate and reassociate from one wireless AP to another, maintaining a continuous logical connection to the wired network.
RANGE IN A Wi-Fi NETWORK
One of the factors that affect the range of a Wi-Fi network is the distance of the client devices to your base station. In an open area with no walls, furniture or interfering radio devices you may be able to get a range of 500 feet or more from your base station to the Wi-Fi equipped computer. In fact you could get a signal from up to a mile away depending on the antennas you use and environmental conditions.
Many base stations can also act as relay stations for your network. For example if you locate one Wi-Fi equipped computer 100 feet away from your base station, another Wi-Fi computer 100 feet away in another direction and then position your base station in the middle, you can create a network with a range of 200 feet from the Wi-Fi computer to the other.
Wi-Fi, or'IEEE 802.11b, speed decreases the farther you move away from your network. For example when you are close to the base station your Wi-Fi computer should be able to get the full 11Mbps data rate. Move farther away, and depending on the environment, the data rate will drop to 2Mbps, and finally to 1Mbps. But getting just 1Mbps throughput is still a perfectly acceptable performance level. 1Mbps is faster than most DSL and cable connections, which means it's still a satisfactory high speed transmission if you are sending and receiving e-mail, cruising the internet or just performing data entry tasks from a mobile computer.


¦
AREA Maximum Range Range at 11Mbps
Outdoors/open .Space with standard antennae 750-1000 feet 150-350 feet
Office/light industrial setting 250-350 feet 100-150 feet
Residential setting 125-200 feet ¢60-80 feet
SECURITY
Because wireless is a shared medium, everything that is transmitted or received over a wireless network can be intercepted. Encryption and authentication are always considered when developing a wireless networking system. The goal of adding these security features is to make wireless traffic as secure as wired traffic. The IEEE 802.11b standard provides a mechanism to do this by encrypting the traffic and authenticating nodes via the Wired Equivalent Privacy (WEP) protocol.

The IEEE 802.11 standard defines the following mechanisms for wireless security:
¢ Authentication through the open system and shared key authentication types
¢ Data confidentiality through Wired Equivalent Privacy (WEP)

Open system authentication does not provide authentication, only identification using the wireless adapter's MAC address. Open system authentication is used when no authentication is required. Some wireless APs allow the configuration of the MAC addresses of allowed wireless clients. However, this is not secure because the MAC address of a wireless client can be spoofed.
Shared key authentication verifies that an authenticating wireless client has knowledge of a shared secret. This is similar to preshared key authentication in Internet Protocol security (IPsec). The 802.11 standard currently assumes that the shared key is delivered to participating STAs through a secure channel that is independent of IEEE 802.11. In practice, this secret is manually configured for both the wireless AP and client. Because the shared key authentication secret must be distributed manually, this method of authentication does not scale to a large infrastructure mode network (for example, corporate campuses and public places, such as malls and airports).
Additionally, shared key authentication is not secure and is not recommended for use.

WIRED EQUIVALENT PRIVACY (WEP)
WEP utilizes RC42, a symmetric algorithm known as a stream cipher, for encryption. A symmetric algorithm is one that relies on the concept of a single shared key (as opposed to a public key) that is used at one end to encrypt plaintext (the data) into ciphertext (the encrypted data), and at the other end to decrypt it - convert the ciphertext back to plaintext. Thus, the sender and the receiver share the same key, and it must be kept secret.
Stream ciphers encrypt data as it is received, as opposed to block ciphers that collect data in a buffer and then encrypt it a block at a time. Stream ciphers are tempting to use for applications requiring hardware implementation (i.e. wireless LAN cards), because they can be implemented very efficiently in silicon.


WEP VULNARABILITIES
Not long after WEP was developed, a series of independent research studies began to expose its cryptographic weaknesses. Even with WEP enabled, third parties with a moderate amount of technical know-how and resources could breach WLAN security. Three key difficulties were identified:
1. WEP uses a single, static shared key. It remains the same unless a network administrator manually changes it on all devices in the WLAN, a task that becomes ever more daunting as the size of the WLAN increases.
2. At the time of its introduction, WEP employed a necessarily short 40-bit encryption scheme. The scheme was the maximum allowed by US export standards at that time. In 1997, the US government deemed the export of data cryptography to be as threatening to national security as the export of weapons of mass destruction. By necessity, Wi-Fi security had to be weak if the specification was to be adopted as an international standard and if products were to be freely exported.

3. Other technical problems contributed to its vulnerability, including attacks that could lead to the recovery of the WEP key itself.

Together, these issues exposed that WEP was not sufficient for enterprise-class security.

VIRTUAL PRIVATE NETWORKS (VPNs)
Virtual Private Network technology (VPN) has been used to secure communications among remote locations via the Internet since the 1990s. A familiar and already widely used technology in the enterprise, it can readily be extended to Wi-Fi WLAN segments on existing wired networks. Although VPNs were originally developed to provide point-to-point encryption for long Internet connections between remote users and their corporate networks, they have recently been deployed in conjunction with Wi-Fi WLANs. When a WLAN client uses a VPN tunnel, communications data remains encrypted until it
0
reaches the VPN gateway, which sits behind the wireless AP. Thus, intruders are effectively blocked from intercepting all network communications. Since the VPN encrypts the entire link from the PC to the VPN gateway in the heart of the corporate network, the wireless network segment between the PC and the AP is also encrypted. This is why VPNs have been recommended to help secure Wi-Fi.

While VPNs are generally considered an enterprise solution, integrated products that offer VPN pass-through connections, firewalls and routers are available to accommodate telecommuters who work from home. Although they provide excellent security, VPNs are not self-managing. User credentials and, often, VPN software must be distributed to each client. However, when properly installed, VPNs extend the high level of security they provide on wired networks to WLANs. In fact, some Wi-Fi vendors themselves have utilized VPNs in networks to secure their own internal Wi-Fi networks.


Wi-Fi PROTECTED ACCESS
Wi-Fi Protected Access is a specification of standards-based, interoperable security enhancements that strongly increase the level of data protection and access control for existing and future wireless LAN systems. Designed to run on existing hardware as a software upgrade, Wi-Fi Protected Access is derived from and will be forward-compatible with the upcoming IEEE 802.11 i standard. When properly installed, it will provide wireless LAN users with a high level of assurance that their data will remain protected and that only authorized network users can access the network.

Wi-Fi Protected Access had several design goals, i.e.,: be a strong, interoperable, security replacement for WEP, be software upgradeable to existing Wi-Fi CERTIFIED products, be applicable for both home and large enterprise users, and be available immediately. To meet these goals, two primary security enhancements needed to be made. Wi-Fi Protected Access was constructed to provide an improved data encryption, which was weak in WEP, and to provide user authentication, which was largely missing in WEP.


Enhanced Data Encryption through TKIP
To improve data encryption, Wi-Fi Protected Access utilizes its Temporal Key Integrity Protocol (TKIP). TKIP provides important data encryption enhancements including a per-packet key mixing function, a message integrity check (MIC) named Michael, an extended initialization vector (IV) with sequencing rules, and a re-keying mechanism. Through these enhancements, TKIP addresses all WEP's known vulnerabilities.
Enterprise-level User Authentication via 802.1x and EAP
WEP has almost no user authentication mechanism. To strengthen user authentication, Wi-Fi Protected Access implements 802.1x and the Extensible Authentication Protocol (EAP). Together, these implementations provide a framework for strong user authentication. This framework utilizes a central authentication server, such as RADIUS, to authenticate each user on the network before they join it, and also employs "mutual authentication" so that the wireless user doesn't accidentally join a rogue network that might steal its network credentials.
SPECIAL FEATURES OF Wi-Fi
Unlike today's wired network, a Wi-Fi network requires little more than an access point(AP). Access to a Wi-Fi- network does not require an expensive connection to each user. Wi-Fi technology is also far less expensive to deploy than the limited wireless technologies of currently existing cellular servicing providers.
Access to a Wi-Fi broad band can be provided both outdoors and indoors. Whether from an outdoor cafe or a park bench a person can access the Internet if they are in range of a service station. Such a Wi-Fi broadband is much power full and can transmit data at a rate of 11 Mbps which is sufficient for all types of multimedia.
Many schools and businesses have unsuitable building layouts or walls that cannot be wired for various reasons making it difficult or impossible to build a wired network. Wi-Fi is a very cost effective alternative in these environments.
A Wi-Fi network can provide many benefits for the society. It can provide local hospitals.
Though the radio waves are of relatively high frequency, they are not powerful enough to pass through multiple layers of building materials. Specifically radio waves are completely blocked by steel. For this reasons the factors deciding performance are proximity to access point and the degree tc which the signal is blocked by the surroundings.
As more computers begin to communicate with the same access point ,a bottleneck occurs. An access point has a finite amount of network bandwidth tc which it is physically linked. As a result, all computers that are associated with a specific access point must share the same bandwidth. More computers means the possibility for a slower network connection.
Since Wi-Fi technology is constantly improving these shortcomings will get removed soon.
ADVANTAGES
It's flexible: With a wireless network you and your staff can have uninterrupted access to people, information and tools as you and they move through the workplace with your mobile PC.

It's responsive: As you change your business operations your wireless network can change with you.

It's customized: Your wireless network can be configured the way you want it.-even combined with your current wired network.

It's fast: From 11 to 54 Mbps throughput and advanced roaming capabilities provide reliable access to e-mail, the Internet, file sharing and other network resources away from the desk.

It's cost-effective: Expand and extend your existing network by simply adding more adapters and access points. Planning is a no brainier as you need to buy only what you need.

It's secure: Current standards utilizes 64- and 128-bit WEP encryption and help guard the network from intruders and protect data in transit. Add in technology and you have increased WLAN protection important for mission-critical data.
In addition to the "hard " benefits of increased efficiency, productivity, manageability and cost savings, wireless networks will certainly make a This is a technology savvy company' statement to the world.
LIMITATIONS

It has a limited bandwidth of about 83.5 MHz.


¢ Frequency spectrum used by IEEE 802.11b is shared by many other systems like microwave ovens, cordless phones etc. This frequency sharing causes interference problem.


¢ Security techniques are not reliable yet.
FUTURE TRENDS
IEEE 802.11a
The 802.11a supplement to 802.11 was published in 1999. It uses Orthogonal Frequency Division Multiplexing (OFDM) to provide data rates to 54 Mbps in the 5 GHz U-NII bands. In addition to being uncrowded, more spectrums in the U-Nll bands allow room for 12 non-overlapping channels, compared to just three in the 2.4 GHz ISM bands. Both of these factors make operating in the U-NII bands far less prone to interference.
However, at 5 GHz, more path loss occurs due to increased absorption of the RF energy by walls and other solid objects. This, combined with a decrease in range due to the higher data rates, may require that more access points be installed to effectively cover an area comparable to that of 802.11b.

IEEE 802.11g
The 802.11g task group is working on a supplement to the 802.11 standard that defines a technology for operation at 2.4 GHz that offers higher data rates (up to 22 Mbps) using OFDM, while remaining backwards compatible to 802.11b. In addition, the supplement will specify even higher data rates using two different methods (up to 33 Mbps using PBCC-DSSS and up to 54 Mbps using CCK-OFDM) which manufactures can optionally incorporate. When compared to 802.11a, 802.11g offers the advantages of lower cost, backwards compatibility to existing 802.11b equipment, and less path loss than 802.11a. This translates into higher data rates for a given range, or increased range for a given data rate.
CONCLUSION
Wi-Fi provides freedom: freedom to physically move around your home or business and still stay connected to the Internet or local network; freedom to grow and move an office or business without having to install new cables and wires; freedom to be connected while traveling and on the road. Wireless "HotSpots" (airports, hotels, coffee shops, convention centers and any other place where someone can connect to a wireless network) are being installed worldwide. All this means Wi-Fi truly does provide unprecedented freedom. Plus, it is cool, and it is fun - as those in the know say, "Once you go wireless, you will never want to use a cable again."
There are real and measurable benefits to using a wireless network versus a standard wired network. For a home installation customer, the greatest benefit is that there are no wites needed: you don't need to drill holes in walls and floors; you don't need to drag cables or hide them under rugs. One Wi-Fi access point can provide network access for any typically sized home.And if you live in a rental or a historical building, you may not be allowed to drill holes-that makes wireless your only solution.
Wi-Fi use is growing fast in homes, public access areas and businesses- both large and small. The Wi-Fi Alliance is active with many industry organizations and is working closely with manufacturers to make sure that existing Wi-Fi gear is compatible with wireless technologies developed in future.
REFERENCES
1. "Wi-Fi: What's next", Paul S.Henry, Hui Luo, IEEE Communications Magazine, December 2002.
2. "Wireless LANs and smart homes", Mahmoud Nagnshineh, IEEE Wireless Communications, August 2002.
3. "Why Wi-Fi is so hot", Data Quest, June 2003.
4. "Overview of IEEE 802.11 Security", http://www.techonline.com.
5. Wireless Networking Handbook, Jim Geier.
6. Wireless Digital Communications, Dr. Kamilo Feher.

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22-03-2010, 07:59 PM
Post: #3
RE: wifi seminar report
Configuring Security Featuers For Wi-Fi (Wireless) Broad Band Access
Recently Intelligence agencies  have found that terrorists were using unsecured wi-fi connections for sending their

emails. BSNL as an ISP is helpless in tracing the user credentials in such cases.
To educate our customers , this presentation provides an overview of configuring Wi-Fi security features at both PC

or LAPTOP & ADSL Modem Level.

Open the browser and type the url http://192.168.1.1.
Type username admin and password admin in login window


Step 2: Select the required SSID (Service Set IDentifier) and Network Authentication. Enable WEP

Encryption using the pull down menu. The following screen will appear.

Step 3 :

Select encryption strength as 128bit or 64bit.

Enter the network key
- 5 ASCII characters for 64 bit encryption - 13 ASCII characters for 128 bit encryption

Four network keys can be entered.
Select one network key as the current network key.
CONTINUED¦



Enable the WPA-PSK network authentication from the pull down menu if you desire to use the security as

WPA-PSK method of security. Enter the pre-shared key value in the WPA Pre-Shared Key field.








Click on Save / Apply Button




Wi-Fi Configuration in PC/Laptop

You need to configure same WEP key in your PC/Laptop which you have entered in CPE wi-fi security configuration.
For this go to the properties of Wi-Fi connection,
select the tab Wireless Networks.
Select the wi-fi network name ( more than one networks may be present in your area, identify your network by SSID

name which is configured in modem. Normally the CPE model name ( say WA1003A) is factory default SSID setting) and

click on Properties.
Look for field Data Encryption and network ID, select WEP as Data Encryption and enter the network ID which you

have entered in CPE configuration as Encryption Key.
NOTE: These steps may be different for different client Wi-Fi hardware/software. The screen shots of a typlical

example are given below.

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28-05-2010, 09:48 PM
Post: #4
RE: wifi seminar report

.doc  WIFI SEMINAR.doc (Size: 42.5 KB / Downloads: 204)

WI-FI
{{*WiFi or Wireless Fidelity refers to the technology based on the radio transmission of internet protocol data from an internet connection wirelessly to a host computer. Most often the internet connection is a higher speed one such as satellite, DSL or cable rather than slower dial-up connections. It is essentially a wireless connection between your computer and the internet connection. Apple Computer using the WiFi transmitter called Airport. Famous for its ease of use, Apple made connecting wirelessly to the internet from most anywhere in your house a simple task. Today many other companies have successfully entered the marketplace and the majority of laptop computers sold today are WiFi enabled. These are usually public areas such as coffee shops or fast food restaurants where WiFi signals are available for internet access at a price. WiFi networks use radio technologies called IEEE 802.11b or 802.11a to transmit data from the internet connection to the host computer (e.g. your laptop). These technologies provide reliable and fast wireless connectivity and to some degree a level of security.Wi-Fi networks operate in the unlicensed 2.4 and 5 GHz radio bands, with an 11 Mbps (802.11b) or 54 Mbps (802.11a) data rate
*History of Wi-Fi

Back in 1991 Wi-Fi was invented by NCR Corporation/AT&T (later on Lucent & Agere Systems) in Nieuwegein, the Netherlands. Initially meant for cashier systems the first wireless products were brought on the market under the name WaveLAN with speeds of 1Mbps/2Mbps. Vic Hayes who is the inventor of Wi-Fi has been named 'father of Wi-Fi' and was with his team involved in designing standards such as IEEE 802.11b, 802.11a and 802.11g. In 2003, Vic retired from Agere Systems. Agere Systems suffered from strong competition in the market even though their products were cutting edge, as many opted for cheaper Wi-Fi solutions. Agere's 802.11abg all-in-one chipset (code named: WARP) never hit the market, Agere Systems decided to quit the Wi-Fi market in late 2004.
*PROCESS OF WIFI:Wifi that allows an internet connection to be broadcast through radio waves . The signals are broadcast from antennas from top of tall buildings The waves can be picked up by wifi receivers attached to computers, personal digital assiment .
Computers equipped with wifi cards pick up signals when they come within range of a wifi network .software in computer searches for signals and network prompts user to enter a password and username.Fee based network ask for a credit card number too.
Wifi card assigns your computer an internet address }}}SHEFALI


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*Devices

(1)Wireless adapters: Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as PCI, miniPCI, USB, ExpressCard, Card bus and PC card. Most newer laptop computers are equipped with internal adapters. Internal cards are generally more difficult to install.
(2)Wireless routers: Wireless routers integrate a WAP, Ethernet switch, and internal Router firmware application that provide IP Routing, NAT, and DNS forwarding through an integrated WAN interface. A wireless router allows wired and wireless Ethernet LAN devices to connect to a (usually) single WAN device such as cable modem or DSL modem. A wireless router allows all three devices (mainly the access point and router) to be configured through one central utility. This utility is most usually an integrated web server which serves web pages to wired and wireless LAN clients and often optionally to WAN clients. This utility may also be an application that is run on a desktop computer such as Apple's AirPort.
(3)Wireless network bridges connect a wired network to a wireless network. This is different from an access point in the sense that an access point connects wireless devices to a wired network at the data-link layer. Two wireless bridges may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes.
(4)Wireless range extenders or wireless repeaters can extend the range of an existing wireless network. Range extenders can be strategically placed to elongate a signal area or allow for the signal area to reach around barriers such as those created in L-shaped corridors.
(5)Aerials and connectors:Most commercial devices (routers, access points, bridges, repeaters) designed for home or business environments use either RP-SMA or RP-TNC antenna connectors. PCI wireless adapters also mainly use RP-SMA connectors. Most PC card and USB wireless only have internal antennas etched on their printed circuit board while some have MMCX connector or MC-Card external connections in addition to an internal antenna. cards found in various wireless appliances contain all of the connectors listed.
* GENERAL STANDARDS OF WIFI:

Wireless networking comes in three major standards: 802.11b, 802.11a and 802.11g. Each of these standards has benefits and disadvantages. When selecting a networking standard you should carefully consider your needs in terms of range, building layout, and budget.

802.11b The standard wireless type is 802.11b. It has a maximum speed of 11 Mbps, with a maximum operating range of 300 ft. indoors and 500 ft. in an open area. The distance from the access point directly determines the speed of the connection. At 50 feet the speed is normally 11 Mbps. At ranges of 200-400 feet speed may fall to 1 Mbps or lower which can cause signals to drop off at random times, as well as the connection being slow. 802.11b operates on the popular 2.4 GHz frequency band, which can cause problems with cordless phones and microwave ovens on rare occasions.
802.11a In comparison to 802.11b, 802.11a is faster, however equipment using this standard is often more expensive. It provides a significant increase in speed (up to 54 Mbps) but with a shorter operating range. At distances over 100 feet the speed decreases, but at close ranges, speed will normally be between 22-40 Mbps. This equipment utilizes the 5 GHz range, which means more reliability, especially if you have other wireless networks in the same area.
802.11g A new line of products from wireless manufacturers combines the concepts of both 802.11a and 802.11b. Known as ?G?technology (802.11g), it features the speed of 802.11a equipment, but is completely backward compatible with existing 802.11b networks. It is slightly cheaper than the 802.11a technology, but still uses the 2.4 GHz band, so it can still cause problems with other devices. It bridges the gap between 802.11a and b, while providing an easy upgrade path for an existing ?b?network. The range is about the same as 802.11b. This standard is not compatible with 802.11
FAULTS IN WI-FI system
#Threats to security

The most common wireless encryption standard, Wired equivalent privacy or WEP, has been shown to be easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2), which began shipping in 2003, aims to solve this problem and is now available on most products. Wi-Fi Access points typically default to an "open" (encryption-free) mode. Novice users benefit from a zero-configuration device that works out of the box, but this default is without any wireless security enabled, providing open wireless access to their LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). Wi-Fi networks that are open (unencrypted) can be monitored and used to read and copy data (including personal information) transmitted over the network, unless another security method is used to secure the data, such as a VPN or a secure web page.
#Population

Many 2.4 GHz802.11b and 802.11g access points default to the same channel on initial startup, contributing to congestion on certain channels. To change the channel of operation for an access point requires the user to configure the device.
# Channel pollution

Standardization is a process driven by market forces. Interoperability issues between non-Wi-Fi brands or proprietary deviations from the standard can still disrupt connections or lower throughput speeds on all user's devices that are within range, to include the non-Wi-Fi or proprietary product. Moreover, the usage of the ISM band in the 2.45 GHz range is also common to Bluetooth,WPAN “CSS,ZigBee and any new system will take its share.Wi-Fi pollution, or an excessive number of access points in the area, especially on the same or neighboring channel, can prevent access and interfere with the use of other access points by others, caused by overlapping channels in the 802.11g/b spectrum, as well as with decreased signal-to-noise ratio (SNR) between access points. This can be a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points. Additionally, other devices use the 2.4 GHz band: microwave ovens, security cameras, Bluetooth devices and (in some countries) Amateur radio, video senders, cordless phones and baby monitors, all of which can cause significant additional interference. General guidance to those who suffer these forms of interference or network crowding is to migrate to a Wi-Fi 5 GHz product, (802.11a, or the newer 802.11n if it has 5 GHz support) because the 5 GHz band is relatively unused, and there are many more channels available. This also requires users to set up the 5 GHz band to be the preferred network in the client and to configure each network band to a different name (SSID). It is also an issue when municipalities,[9] or other large entities such as universities, seek to provide large area coverage. This openness is also important to the success and widespread use of 2.4 GHz Wi-Fi.

#USES:

(1) A Wi-Fi enabled device such as a PC, game console, cell phone, MP3 player or PDA can connect to the Internet when within range of a wireless network connected to the Internet. Hotspots can cover as little as a single room with wireless-opaque walls or as much as many square miles covered by overlapping access points. Wi-Fi has been used to create mesh networks
(2).In addition to restricted use in homes and offices, Wi-Fi is publicly available at Wi-Fi hotspots provided either free of charge or to subscribers to various providers. Free hotspots are often provided by businesses such as hotels, restaurants, and airports who offer the service to attract or assist clients. Sometimes free Wi-Fi is provided by enthusiasts, or by organizations or authorities who wish to promote business in their area. Metropolitan-wide WiFi (Muni-Fi) already has more than 300 projects in process.
(3) Wi-Fi also allows connectivity in peer-to-peer (wireless ad-hoc network) mode, which enables devices to connect directly with each other. This connectivity mode is useful in consumer electronics and gaming applications.
(4)When the technology was first commercialized there were many problems because consumers could not be sure that products from different vendors would work together. The Wi-Fi Alliance began as a community to solve this issue so as to address the needs of the end user and allow the technology to mature. The Alliance created the branding Wi-Fi CERTIFIED to show consumers that products are interoperable with other products displaying the same branding.
(5)Many consumer devices use Wi-Fi. Amongst others, personal computers can network to each other and connect to the Internet, mobile computers can connect to the Internet from any Wi-Fi hotspot, and digital cameras can transfer images wirelessly.
(6)Routers which incorporate a DSL or cable modem and a Wi-Fi access point are often used in homes and other premises, and provide Internet access and internetworking to all devices connected wirelessly or by cable into them. Devices supporting Wi-Fi can also be connected in ad-hoc mode for client-to-client connections without a router.
(7) Wi-Fi enables wireless voice applications (VoWLAN or WVOIP).
}}}shubham
ADVANTAGES OF WIFI:

(1) Wi-Fi allows LANs to be deployed without cabling for client devices, so reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, there wireless LANs are useful .
(2) As of 2007 wireless network adapters are built into most modern laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices. Wi-Fi has become widespread in corporate infrastructures.
(3) Different competitive brands of access points and client network interfaces are inter-operable at a basic level of service. Products designated as "Wi-Fi Certified" by the Wi-Fi Alliance are backwards inter-operable. Wi-Fi is a global set of standards. Unlike mobile telephones, any standard Wi-Fi device will work anywhere in the world.
(4) Wi-Fi is widely available in more than 250,000[citation needed] public hotspots and tens of millions of homes and corporate and university campuses worldwide. WPA is not easily cracked if strong passwords are used .
(5) Unlike packet radio systems, Wi-Fi uses unlicensed radio spectrum and does not require regulatory approval for individual deployers.
(6) Wi-Fi products are widely available in the market. Different brands of access points and client network interfaces are interoperable at a basic level of service.
(7) Competition amongst vendors has lowered prices considerably since their inception.
(8).Wi-Fi is a global set of standards. Unlike cellular carriers, the same Wi-Fi client works in different countries around the world.
*Disadvantages of wifi:

(1) Spectrum assignments and operational limitations are not consistent worldwide.
(2.) Some countries, such as Italy, formerly required a 'general authorization' for any Wi-Fi used outside an operator's own premises, or require something akin to an operator registration.[citation needed] Equivalent isotropically radiated power (EIRP) in the EU is limited to 20 dBm (0.1 W).
(3.) Power consumption is fairly high compared to some other low-bandwidth standards, such as Zigbee and Bluetooth, making battery life a concern.
(4.) The most common wireless encryption standard, Wired Equivalent Privacy or WEP, has been shown to be easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2), which began shipping in 2003, aims to solve this problem and is now available on most products. Wi-Fi Access Points typically default to an "open" (encryption-free) mode. Novice users benefit from a zero-configuration device that works out of the box, but this default is without any wireless security enabled, providing open wireless access to their LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). Wi-Fi networks that are open (unencrypted) can be monitored and used to read and copy data (including personal information) transmitted over the network, unless another security method is used to secure the data, such as a VPN or a secure web page.
(5.) Many 2.4 GHz 802.11b and 802.11g Access points default to the same channel on initial startup, contributing to congestion on certain channels. To change the channel of operation for an access point requires the user to configure the device.
(6.) Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor range with improved (directional) antennas can be several kilometres or more with line-of-sight.
(7) Wi-Fi performance also decreases exponentially as the range increases.
(8) Wi-Fi pollution, or an excessive number of access points in the area, especially on the same or neighboring channel, can prevent access and interfere with the use of other access points by others, caused by overlapping channels . This can be a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points.
(9) It is also an issue when municipalities or other large entities such as universities, seek to provide large area coverage. This openness is also important to the success and widespread use of 2.4 GHz Wi-Fi.

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08-06-2010, 04:41 PM
Post: #5
RE: wifi seminar report

.doc  wifi_doc.doc (Size: 76.5 KB / Downloads: 206)

WI-FI

Presented By:
T.Y.ARCHANA K.GAYATHRI.
CSIT 4/4 CSIT 4/4
SNIST



ABSTRACT


Wi-Fi is quickly gaining in popularity with access points across the United States increasing by approximately 100% in 2003. Wi-Fi refers to a set of wireless networking technologies more specifically referred to as 802.11a 802.11b and 802.11g. These standards are universally in use around the globe, and allow users that have a Wi-Fi capable device, like a laptop or PDA, to connect anywhere there is a Wi-Fi access point that is available. The three standards that are referred to signify the speed of the connection they are capable of producing. 802.11b (which transmits at 11 Megabits per Second) is the most common, although it is quickly getting replaced by the faster Wi-Fi standards. Both 802.11a and 802.11g are capable of 54 MBPS, with 802.11a adding additional capabilities. Across the board, all of these Wi-Fi standards are fast enough to generally allow a broadband connection. Wi-Fi is an emerging technology that will likely be as common as electrical outlets and phone lines within a few years. Wi-Fi adds tremendous levels of convenience and increased productivity for workers whose offices are equipped with Wi-Fi, as well as travelers that can increasingly access Wi-Fi in airports, coffee shops, and hotels around the world.

Definition of Wi-Fi:


Wi-Fi stands for Wireless fidelity - a radio-frequency technology that allows laptop or handheld computer users in the vicinity of a 'hotspot' to access the Web or corporate networks. Wireless fidelity, defined by the Australian Communications Authority (2004:210) as Used generically to refer to WLAN (IEEE 802.11) technology providing short-range, high data rate connections between mobile data devices and access points connected to a wired network. Wireless fidelity; Wireless Ethernet Compatibility Allianceâ„¢s (WECA) brand identity for the IEEE 802.11b standard; WECA certification that ensures productsâ„¢ compatibility. This is another name for IEEE 802.11. It is a term coined by the Wireless Ethernet Compatibility Alliance (WECA). Products certified as Wi-Fi by WECA are interoperable with each other even if they are from different manufacturers. A user with a Wi-Fi product can use any brand of Access Point with any other brand of client hardware that is built to the Wi-Fi standard.


How Does Wi-Fi Work?

The wide use of notebook and other portable computers has driven advances in wireless networks. The most common use for a wireless network is to connect a single notebook computer to a broadband internet connection. Wireless networks use either infrared or radio- frequency transmissions to link these mobile computers to networks. Wi-Fi networks use radio technologies called IEEE 802.11b or 802.11a to provide a secure, fast, and reliable wireless connection. IEEE stands for Institute of Electrical and Electronics Engineers, New York, which is a membership organization that includes engineers, scientists and students in electronics and allied fields.
It has more than 300,000 members and is involved with setting standards for computers and communications. The international standard for wireless networking uses a frequency of 2.4-2.4835GHz. These frequencies are common in microwaves, and cord less phones.
Wi-Fi functions through a transmitting antenna which is usually linked to a DSL or high-speed land-based Internet connection and uses radio waves to beam signals. Another antenna, which is in the laptop or PC, catches the signal. The signal, usually l, has a range of about 300 feet for most home connections. The farther the user is from the signal, the slower the connection speed. Wireless LANS have capacity speeds from less than 1 Mbps to 8 Mbps. Wi-Fi can easily be expanded in the home or business with the simple step of plugging in a card or a USB connection to the new computer or other Wi-Fi certified product. No cords or cables, or wires are necessary.
Specifications:
Wi-Fi is based on the IEEE 802.11 specifications. There are currently four deployed 802.11 variations: 802.11a, 802.11b, 802.11g, and 802.11n. The b specification was used in the first Wi-Fi products. The g and n variants are the ones most often sold as of 2005.
Wi-Fi specifications
Specification Speed Frequency
Band Compatible
with
802.11b
11 Mb/s 2.4 GHz b
802.11a
54 Mb/s 5 GHz a
802.11g
54 Mb/s 2.4 GHz b, g
802.11n
100 Mb/s 2.4 GHz b, g, n


In most of the world, the frequencies used by Wi-Fi do not require user licenses from local regulators (eg, the Federal Communications Commission in the US). 802.11a equipment, using a higher frequency, has reduced range, all other things being equal.





Standards of Wi-Fi:

Before you do anything, including buy a single piece of equipment, the first order of business for your home wireless local area network (WLAN) is to determine the type of wireless technology that is most appropriate for your environment. Because each has its own characteristics, strengths, and weaknesses, you'll find some are better suited than others to your particular situation. In the world of WLAN standards there are several you can choose from today, and more on the horizon. While many are similar in the way they operate or the type of equipment they use, there are also key differences that you must be aware of. When comparing the different standards, it's easy to get caught up in a lot of the technical minutiae that differentiate them. When all is said and done though, you'll find three major factors that you need to concern yourself with--cost, speed, and range.

802.11b/2.4GHz vs. 802.11a/5GHz

There are currently two major WLAN standards, and both operate using radio frequency (RF) echnology. The two standards have heretofore been colloquially referred to as 802.11b and 802.11a -- together they're collectively called Wi-Fi .To reduce confusion, however, the wireless standard group called the Wi-Fi Alliance will refer to the two
technologies as 2.4GHz and 5GHz, respectively, as least on product packaging. These monikers refer to the frequency band that each technology utilizes. In the alphabet, "a" comes before "b." In the world of wireless networking though, "b" definitely came before "a." The 802.11b specification was the first to be finalized and reach the marketplace.

Performance

802.11b/2.4GHz devices operate in an unlicensed radio band and transmit data on the same frequency as some household appliances, including some cordless phones and even microwave ovens. The 802.11b specification provides for a bandwidth rating of 11 Megabits per second (Mbps). This is just a theoretical maximum, however. Wireless networks, as well as wired LANs, never let you obtain that level of performance, or even close to it. The actual throughput you can expect to obtain from an 802.11b network will typically be between 4 and This level of performance is more than sufficient for most rudimentary computing tasks. When you consider that a typical broadband DSL or cable modem connection might provide you with from 600kbps to 1.6Mbps of downstream bandwidth, you can see that the speed of 802.11b is not be an impediment to activities like Web browsing, e-mail, file transfer, running applications, and even streaming Internet-based audio and video.
On the other hand, it's not hard to envision scenarios where your bandwidth needs might be greater -- when you want to quickly transfer very large files like graphics, audio, or video or stream those same audio and video files, like your collection of MP3s or home movies on your hard disk.
If you often see the need for more speed, consider 802.11a. Products based on this 5GHz specification offer higher performance. 802.11a has a maximum bandwidth of 54Mbps, almost five times that of 802.11b. Like its predecessor though, you won't see anything near that in the real world. Instead, expect a maximum throughput of between 20 and 25Mbps -- still five times what you get from 802.11b.

Designing a Wi-Fi Network:
Step 1”Planning
Setting Up A Wireless Network:
Once you've decided to free yourself by "going wireless," you can reap all the benefits of mobile computing ” and it's simple and easy to set up and operate a wireless network. Here's how to plan for, install and operate your Wi-Fi network
¢ What Makes Up a Wireless Network?
¢ Do I Need a Peer-To-Peer Network, or One with a Base Station (An Access Point Or Gateway)?
¢ What Are the Wi-Fi Radio Options For My Laptops, Desktops and PDAs?
¢ Planning for Access Points and Gateways
¢ How Many Users Can Use a Single Access Point?
¢ Choosing Components for Your Network
¢ Count The Total Number of Users and Computers
¢ Place a Wi-Fi Radio In Each Computer
¢ Determine the Number Of Base Stations (Access Points or Gateways) You Need
¢ How Do You Connect Your Wi-Fi Network to the Internet?
¢ How Do You Make Printers Work on Your Wi-Fi Network?
¢ Can You Share Devices on Your Network to Save Money?
Step 2”Selection
Types of Equipment
There are currently two types of Wi-Fi components you'll need to build your home or office network: Wi-Fi radio (also known as client devices) devices (desktops, laptops, PDAs, etc.), and access points or gateways that act as base stations. A third type, Wi-Fi equipped peripherals, are emerging and will soon be commonplace. This group includes printers, scanners, cameras, video monitors, set-top boxes and other peripheral equipment
¢ PC Card Radio
¢ Mini-PCI Modules and Embedded Radios
¢ USB Adapters
¢ PCI and ISA Bus Adapters
¢ Compact Flash and Other Small-Client Formats




Step 3 ” Set Up

10 Easy Steps to Setting Up Your Home or Small Office Network
Wi-Fi networks are easy to set up and operate but if you've never done this before the process may seem daunting and most likely you don't know where to start. Use this step-by-step guide to help you through the process of planning and setting up your wireless network
1. Count Your Computers
2. Pick out the Right Kind of Wi-Fi Radios for Your Computers
3. Decide Between a Wi-Fi Gateway or Access Point
4. Get the Right Wi-Fi Radio and Accessories
5. Read the Installation Instructions
6. Read the Instructions Again
7. Install Your Access Point or Gateway First
8. Install the First Wi-Fi Radio Device
9. Configure the Access Point
10. Connect the Rest of Your Computers and the Printer

Step 4”Adding Wi-Fi to a Desktop Computer

The procedures necessary to complete these steps are often different for each manufacturer. Whenever you see this image, you should look in your specific product manual for the correct procedure to follow.
¢ USB Radio Installation
¢ PCI Adapter Installation
¢ Is a USB or a PCI Solution Better For You?
You can easily add Wi-Fi to a laptop computer, but some desktop computers can take a little more effort. For most laptops, you simply slide in a Type II PC Card Wi-Fi radio, install the software, and you're up and running. Since very few desktop computers provide PC Card slots, they require a USB [Universal Serial Bus] Wi-Fi radio adapter or a PCI-based [Peripheral Component Interconnect] Wi-Fi radio adapter to connect to a Wi-Fi network

Step 5”Security
Securing your Wi-Fi Network

Here are a few simple steps you can take to maximize the security of your wireless network and to protect your data from prying eyes and ears. This section is intended for the home, home office and small office user. The procedures necessary to complete these steps are often different for each manufacturer. Whenever you see this image, you should look in the encryption or security section of your specific product manual for the correct procedure to follow.
¢ Deploy WPA„¢ (Wi-Fi Protected Access„¢) or WPA2„¢
¢ Change Your Default Password
¢ Close Your Network (If Possible)
¢ Change Your Network Name
¢ Move Your Access Point
¢ Use MAC Control Tables
¢ Other Simple Solutions
¢ Use a VPN (Virtual Private Network)
¢ Additional Information

Why Wi-Fi?

Because chances are that, within the next year or so, you'll use Wi-Fi regularly at work, at home, or on the road. You may well depend on Wi-Fi as much as you do your cell phone, your laptop computer, or your personal digital assistant (PDA). In fact, all those devices increasingly come ready to work with Wi-Fi. (One example: By 2007, according to IDC Research of Framingham, Mass., 98% of all new notebok PCs will be sold with Wi-Fi capability). That means the next time you invest in hardware, you're likely to invest in the Wi-Fi label as well. So it makes sense to learn what Wi-Fi does well -- and where it still needs work.
Wi-Fi refers to products certified to work with the high-tech industry's global standard for high-speed wireless networking .Hardware carrying the Wi-Fi logo has passed rigorous testing by the Wi-Fi Alliance, a trade association based in Mountain View, Calif. Certification means that, regardless of which company manufactured it, the equipment should play nicely with other Wi-Fi devices and networks.
As Wi-Fi compatibility grows -- to date, the alliance has certified nearly 865 products -- so has its popularity. Currently, about 4.7 million Americans regularly use Wi-Fi, according to Stamford, Conn.-based research group Gartner Inc. In four years, that figure will grow to 31 million users in the United States alone.
Why is Wi-Fi so widespread:
It's fast. Wi-Fi's latest version is many times faster than DSL or cable connections, and literally hundreds of times faster than those old dial-up connections. That's particularly handy when you're working on the run, on the road, or from home: If you've ever watched seconds tick by while watching Web pages load, you'll appreciate the potential productivity gain.
It's convenient. As soon as a Wi-Fi-equipped device is within range of a base station, it's online. With no wires, you can move your laptop computer from place to place -- for instance, from your office to a conference room down the hall -- without losing your network connection. (For an online calculator that can help determine ROI on an in-house wireless network," Resources."). When traveling, you can set up shop anyplace equipped with a Wi-Fi network: another company's office, a hotel room, or a convention center.
It's everywhere. Public Wi-Fi access sites -- or "hot spots" -- are multiplying faster than rabbits on Viagra. They're in bookstores, airport lounges, fast-food restaurants (including some McDonald's and Schlotzky's Deli outlets), and coffee shops (including many Starbucks outlets). In addition, local merchants from Cincinnati to Athens, Ga., to Portland, Ore., are footing the bill for bigger hot spots, accessible throughout a business district or neighborhood.
Some companies charge for hot-spot use; others offer free access. All hope they're creating environments where tech-savvy customers will linger -- and, presumably -- spend more money on coffee, books, sandwiches, or whatever the hot-spot host sells. Does the idea pay off? Overall, it's too early to tell. Ultimately, the answer will affect how fast the public hot-spot market heats up. In June 2003, IDC, the Framingham, Mass.-based research company, estimated that the number of commercial Wi-Fi sites would grow 57% annually over the next five years -- but warned that the market is young, volatile, and based on unproven business models. In other words, if hot spots don't generate revenue, expect that growth rate to stall.
For all its wonders, the Wi-Fi world comes with some drawbacks. Among them:
Range: Although you lose the wires, you're still limited to the base station's range, typically 75 to 150 feet indoors and a few hundred feet outdoors, depending on equipment, radio frequency, and obstructions.
Power drain: Networks using early versions of Wi-Fi technology tend to quickly gobble power -- a disadvantage for battery-dependent laptop users.
Interference: Nearby microwave ovens and cordless phones, particularly older models, can slow down Wi-Fi transmissions.
Security: Here's the downside of providing fast, easy access: outsiders can sometimes get into your wireless networks as fast and easily as you can. Check with hardware vendors about the latest security precautions and products. The Wi-Fi Alliance currently recommends using Wi-Fi Protected Access (WPA) technology, which both authenticates users and encrypts data. Look for even tougher security measures within the next year.
Advantages of Wi-Fi:

¢ Unlike packet radio systems, Wi-Fi uses unlicensed radio spectrum and does not require regulatory approval for individual deployers.
¢ Allows LANs to be deployed without cabling, potentially reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.
¢ Wi-Fi products are widely available in the market. Different brands of access points and client network interfaces are interoperable at a basic level of service.
¢ Competition amongst vendors has lowered prices considerably since their inception.
¢ Many Wi-Fi networks support roaming, in which a mobile client station such as a laptop computer can move from one access point to another as the user moves around a building or area.
¢ Many access points and network interfaces support various degrees of encryption to protect traffic from interception.
¢ Wi-Fi is a global set of standards. Unlike cellular carriers, the same Wi-Fi client works in different countries around the world.

Disavantages of Wi-Fi:

¢ Use of the 2.4 GHz Wi-Fi band does not require a license in most of the world provided that one stays below the local regulatory limits and provided one accepts interference from other sources, including interference which causes your devices to no longer function. It is sometimes claimed that Amateur Radio operators have permission to boost the power on their Wi-Fi transmitters up to the legal maximum for their Amateur Radio license class under some conditions; this is not permitted in the US, nor in most locations.
¢ Legislation/regulation is not consistent worldwide; most of Europe allows for an additional 2 channels over those allowed for b and g; Japan has one more on top of that - and some countries, like Spain, prohibit use of the lower-numbered channels. Furthermore some countries, such as Italy, used to require a 'general authorization' for any WiFi used outside the owned premises; or required something akin to operator registration.
¢ The 802.11b and 802.11g flavors of Wi-Fi use the 2.4 GHz spectrum, which is crowded with other equipment such as Bluetooth devices, microwave ovens, cordless phones (900 MHz or 5.8 GHz are, therefore, alternative phone frequencies one can use to avoid interference if one has a Wi-Fi network), or video sender devices, among many others. This may cause a degradation in performance. Other devices which use these microwave frequencies can also cause degradation in performance.
¢ Closed access points can interfere with properly configured open access points on the same frequency, preventing use of open access points by others.
¢ Power consumption is fairly high compared to other standards, making battery life and heat a concern.


Wi-Fi Security:


WiFi equipment could be used to steal personal information (passwords, financial information, identity information, and so on) transmitted from Wi-Fi users, if sensible protections are not used.
The first and most commonly used wireless encryption standard, Wired Equivalent Privacy or WEP, has been shown to be easily breakable even when correctly configured. Most wireless products now on the market support the Wi-Fi Protected Access(WPA) encryption protocol, which is considered much stronger, though some older access points have to be replaced to support it. The adoption of the 802.11i standard (marketed as WPA2) makes available a rather better security scheme ” when properly configured

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