28-05-2010, 09:48 PM
[attachment=3630]
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
{
*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.
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
{
*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.
