Navas Wireless Wiki - User contributions [en]

Wi-Fi How To

2010-08-13T03:56:24Z

JeffLiebermann: /* Measure wireless network performance */

{{Welcome}}
{{GoogleSearch}}
{{Contributions}}

{{Donate}}

'''Collection of "how to" step-by-step recipies for making Wi-Fi work better.'''

{{Wi-Fi Articles}}
__FORCETOC__
== Get started ==
'''<big>[http://www.smallnetbuilder.com/content/view/24861/99/ Wireless Networking Need To Know 2006]</big>'''

== Measure wireless network performance ==
* Internet speed testing (''e.g., ''[http://nitro.ucsc.edu/ NDT]) probably ''won't'' tell you anything about your wireless network performance (because wireless is normally faster than an Internet connection).
* Instead, measure data transfer throughput between two computers on your network, using software tools such as:
** [http://dast.nlanr.net/Projects/Iperf/ Iperf]
** [http://code.google.com/p/xjperf/ Jperf]
** [http://freshmeat.net/projects/netio/ Netio]
* Wireless to ''wireless'' speed will probably be much less than wireless to ''wired'' speed, because ''only one wireless link in one direction can be active at any one time''.

== Network Monitoring ==
Monitor network throughout, amount of data sent/received, etc.

See ''[[Wi-Fi#Network Monitors|Network Monitors]]''.

== Why and How to do a Site Survey ==
''See [[Wi-Fi#Site_Survey_Tools|Site Survey Tools]]''
* [http://www.networkcomputing.com/showArticle.jhtml?articleID=188500632 Crash Course: Wireless Site Surveys]
* [http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00805e9a96.shtml Wireless Site Survey FAQ] (Cisco)

== Wireless LAN layout ==
{|
|[[Image:Wireless LAN Channel Grid.png]]
|Single floor (horizontal) layout and channel assignments of multiple access points (all with the same unique [[wikipedia:Service set identifier|SSID]]) for maximum coverage with minimum interference.
|-
|For multiple floors (vertical) layout, stagger the vertical arrangement.
|[[Image:Wireless LAN Channel Grid multi floors.png]]
|}

== Use a wireless router as a wireless access point ==
# Set [[wikipedia:IP address|IP address]] (manually)
#* In the ''same address range'' as your other devices
#* That ''doesn't conflict'' with any other device (''e.g.,'' router)
# Disable internal [[wikipedia:Dynamic Host Configuration Protocol|DHCP]] server.
# Connect ([[wikipedia:Ethernet|Ethernet]]) cable to ''[[wikipedia:Local area network|LAN]]'' port, not [[wikipedia:Wide area network|WAN]]/Internet port.
#* Nothing connected to WAN/Internet port.
#* May need to use ''[[wikipedia:Ethernet crossover cable|crossover]]'' type cable.
# Disable any wireless-to-wired isolation feature.

== Two wireless networks on one router ==
:''Based on [http://www.wi-fiplanet.com/tutorials/article.php/10724_3714521_1 Implementing Inexpensive Multiple SSID Networks]<br>[Wi-Fi Planet.com Tutorial by Eric Geier, December, 2007]''

Two separate wireless networks are a good way to isolate private and public/guest network clients, where:
* ''Private'' network clients have access not only to the Internet, but also to each other (file and/or printer sharing), wired and wireless
* ''Public/guest'' network clients have access ''only'' to the Internet, ''not'' to each other (see [[Wi-Fi#Wireless Isolation|Wireless Isolation]]), and ''not'' to the private clients

While some wireless routers have this capability built-in (see [[Wi-Fi#Guest Account|Guest Account]]), it can also be done with [[wikipedia:Linksys WRT54G series#Third-party firmware projects|third party firmware]], which can provide additional functionality as well.

The following procedure is for ''two separate wireless networks'' using [http://www.dd-wrt.com DD-WRT] (on [http://www.dd-wrt.com/dd-wrtv3/dd-wrt/hardware.html supported devices]) with the web browser interface (as of v24 preSP2 Beta build 12533).
For ''more than two'' separate wireless networks, consult the reference above.
# '''Configure two wireless networks: ''Wireless → Basic Settings'''''
#* ''Wireless Physical Interface '''wl0'''''
#** This will be the ''private'' wireless network
#** ''Recommendation'': Click ''Disable'' for ''Wireless Network Name (SSID)'' broadcast to avoid conflict with the visible public/guest wireless network [see ''Overcoming Multiple SSID (Not BSSID) Connectivity Issues'' in the reference above]
#* ''Virtual Interfaces''
#** Click ''Add'' to create the ''public/guest'' wireless network, which will be<br>''Virtual Interfaces '''wl0.1'''''
#** Enter a '''unique''' ''Wireless Network Name (SSID)'' (e.g., ''John Doe's Guest Wireless'')
#** Click ''Enable'' for ''AP Isolation'' (to isolate public/guest wireless clients from each other)
#** Click ''Unbridged'' for ''Network Configuration''
#** For ''IP Address'', enter a '''different [[wikipedia:Subnetwork|subnet]]''' from the private network (which is 192.168.<u>1</u>.1 by default):<br>192.168.<u>2</u>.1
#** For ''Subnet Mask'', enter:<br>'''255.255.255.0'''
#* Click ''Save'' (and do '''not''' click ''Apply Settings'')
# '''Configure wireless network security: ''Wireless → Wireless Security'''''
#* Enter desired security for each wireless network
#* '''WPA2 Personal with a strong passphrase is recommended.''' (WEP and WPA-TKIP are '''not''' secure!)
#* ''Note'': DD-WRT v24 preSP2 Beta build 12533 will ''not'' properly authenticate WPA Personal or WPA2 Personal after a reboot ([http://www.dd-wrt.com/dd-wrtv2/bugtracker/view.php?id=3729 bug 003729]), only WEP.
#* Click ''Save'' (and do '''not''' click ''Apply Settings'')
# '''Configure DHCP for public/guest wireless: ''Services → Services → DNSMasq'''''
#* In ''Additional DNSMasq Options'' enter:<code><br>   interface=wl0.1<br>   dhcp-option=wl0.1,3,192.168.2.1<br>   dhcp-option=wl0.1,6,192.168.1.1<br>   dhcp-range=wl0.1,192.168.2.100,192.168.2.249,255.255.255.0,1440m</code>
#* Click ''Save'' (and do '''not''' click ''Apply Settings'')
# '''Configure firewall to isolate public/guest from private: ''Administration → Commands → Command Shell'''''
:* Enter the ''Commands'':<code><br>   iptables -I INPUT -i wl0.1 -m state --state NEW -j logaccept<br>   iptables -I FORWARD -i wl0.1 -o br0 -j logdrop<br>   iptables -I FORWARD -i br0 -o wl0.1 -j logdrop</code>
:* Click ''Save Firewall''
:* Click the '''''Management''''' tab
:* Click ''Apply Settings'' (down at the bottom)

== Isolate Two Networks ==
[[Image:Isolated Networks.png|right|frame|Two Networks with Internet access that are isolated from each other]]
Isolate two local networks from each other with both able to access the same Internet connection using low-cost routers:
* Use three (3) routers (A, B, and C)
* Connect network A to the wireless and/or LAN ports on router A
* Connect network B to the wireless and/or LAN ports on router B
* Connect router A and router B WAN (Internet) ports to LAN ports on router C
* Connect the WAN (Internet) port on router C to the Internet
Notes:
* Routers A and B can be wired and/or wireless.
* This method involves Double NAT, which can sometimes cause problems. (See [[wikipedia:Session Traversal Utilities for NAT|Session Traversal Utilities for NAT]])
* The same effect can also be achieved with a single router that supports [[wikipedia:Virtual LAN|Virtual LAN]] (VLAN) without double NAT, although it may be less secure.

== WPA/WPA2 ==
'''[[wikipedia:Wi-Fi Protected Access#WPA2|WPA2]] is strongly preferred''', because
* '''[[wikipedia:Wired Equivalent Privacy#Flaws|WEP can be easily cracked]]'''
* '''[[wikipedia:Wi-Fi Protected Access#Weakness in TKIP|WPA-TKIP can now be cracked]]'''
There are two forms of WPA/WPA2:
* ''Personal'' or PSK (Pre-Shared Key)
* ''Enterprise'' ([[wikipedia:RADIUS|RADIUS]] authentication)

=== Use WPA Personal with Windows 98/Me/2000 ===
Microsoft provides [http://www.microsoft.com/technet/itsolutions/network/wifi/wififaq.mspx#EMF WPA/WPA2 support for Windows XP]. For earlier versions of Windows, third-party software must be used:
* [http://www.wirelesssecuritycorp.com/wsc/public/WPAAssistant.do McAfee] (free for WPA-PSK)
* [http://www.juniper.net/customers/support/products/oac.jsp Odyssey Access Client] (commercial)
* [http://hostap.epitest.fi/wpa_supplicant/ wpa_supplicant] (free, for Linux, BSD, and Windows)

=== Use WPA/WPA2 Enterprise ===
WPA Enterprise enhances security and is preferred over WPA because each client is authenticated separately. (Sharing a key is a security risk.) Practical authentication ([[wikipedia:RADIUS|RADIUS]]) solutions for small wireless networks include:
* [http://us.zyxel.com/web/product_family_detail.php?PC1indexflag=20040520161256&CategoryGroupNo=1FD9B843-06BE-448D-B770-5383D40CD32E ZyXEL G-2000 Plus] (wireless router with built-in PEAP server)

== Secure a wireless network ==
''Why'' to do it: [http://www.news.com/Worried-about-Wi-Fi-security/2100-7347_3-5540969.html Worried about Wi-Fi security?]

''What'' to do:
# Change the [[wikipedia:Service set identifier|SSID]] to something truly unique (''e.g., ''instead of ''linksys'' or ''NETGEAR'', something like ''John Doe's private wireless'').
# Use some form of [[wikipedia:Wi-Fi Protected Access#WPA2|WPA2]] with a [[wikipedia:Passphrase#Passphrase selection|strong passphrase]]. ''(WEP and WPA-TKIP are '''not''' secure.)''
# Use a [[wikipedia:Personal firewall|personal firewall]] (software firewall) on ''all'' networked computers (wired or wireless).
# [[#Secure network shares|Secure ''all'' network shares]]
# Either ensure remote access to the wireless administrator interface is disabled, or set a [[wikipedia:Password strength|strong]] wireless administrator password.
* For more information, see ''[[Wi-Fi#Wi-Fi Security|Wi-Fi Security]]'' and ''[[Wikibooks:Wifi/Security]]''.
** For things ''not'' to do, see ''[[Wi-Fi#Wi-Fi Security Myths|Wi-Fi Security Myths]]''.

=== Secure WDS ===
WPA ([[wikipedia:Wi-Fi Protected Access|Wi-Fi Protected Access]]) cannot normally be used to secure WDS ([[wikipedia:Wireless Distribution System|Wireless Distribution System]]) wireless repeating/range extension. However, according to the [http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci1104925,00.html TechTarget Expert Answer Center], current versions of the following products support WDS with WPA (albeit likely only with products from the same vendor):
* Apple Airport
* Sveasoft Alchemy
* Belkin 802.11g Wireless Network Access Point
* 3COM OfficeConnect Wireless 108 Mbps 11g PoE Access Point
* Corinex Wireless to Powerline Router G

== Setup a hotspot ==

'''See:'''
* [http://searchsecurity.techtarget.com/general/0,295582,sid14_gci1167675,00.html?track=wsland Controlling WLAN access on a tight budget]
* '''[ftp://download.intel.com/business/bss/infrastructure/wireless/deployment/hotspot.pdf Intel Wireless Hotspot Deployment Guide] ''(link currently broken)'''''
** [http://www.nor-tech.com/solutions/dox/Wi-Fi_Hotspot_Deployment_Guide.pdf Non-Intel link #1] (11/2003 version)
** [http://802.11junk.com/jeffl/crud/Intel%20HotSpot%20Guide.pdf Non-Intel link #2] (9/2005 version)
* '''[[Wi-Fi#Wireless Isolation|Wireless Isolation]]'''
* [[Wikipedia:Hotspot (Wi-Fi)]]
* [[Wikipedia:Captive portal]]

'''Liability:'''

* [http://www.bitlaw.com/internet/isp.html ISP Liability]
* [http://www.libertolaw.com/2-99.html New Law Limits ISP Liability for Copyright Infringement]

=== Hotspot hardware ===
Products that provide "[[Wikipedia:Captive portal|captive portal]]" or splash page functionality:

* D-Link
** [http://www.dlink.com/products/?sec=0&pid=173 Airspot DSA-3100 Public/Private Hot Spot Gateway]
** [http://www.dlink.com/products/?sec=0&pid=402 Airspot DSA-3200 Wireless G Public/Private Hot Spot Gateway]
** [http://www.dlink.com/products/?sec=0&pid=349 Airspot DSA-5100 Public/Private Hot Spot Gateway]
* [http://www.instanthotspot.com/ Instant HotSpot]
* [http://www.linksysinfo.org/forums/showthread.php?t=47282 Linksys WRT54GL with modified firmware] (Linksysinfo.org)
** See also ''[[Wi-Fi#3rd-party Firmware|Wi-Fi 3rd-party Firmware]]''
* [http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=94&scid=&pid=1422 SMCWHSG44-G EliteConnect Wireless Hotspot Gateway]
* [http://www.sonicwall.com/products/tz150_wireless.html SonicWALL TZ 150 Wireless]
* [http://us.zyxel.com/products/model.php?indexcate=1028015363 ZyAIR B-4000 Turn-key Hotspot Gateway]

=== Hotspot firmware ===
3rd-party firmware that provides "[[Wikipedia:Captive portal|captive portal]]" or splash page functionality:
* [http://www.dd-wrt.com DD-WRT] supports:
** [http://www.chillispot.info/ ChilliSpot]
** [http://www.sputnik.com/ Sputnik]
** [http://dev.wifidog.org/ WiFiDog]

=== Hotspot software ===
Products that provide "[[Wikipedia:Captive portal|captive portal]]" or splash page functionality:
* [http://www.dnsredirector.com DNS Redirector] (Runs on Windows XP/2K/2K3 using any existing AP hardware)
* [http://www.freeradius.org/ Free RADIUS] (open source [[wikipedia:RADIUS|RADIUS]] server)
* [http://www.publicip.net/ ZoneCD] (Public IP)

=== Hotspot systems ===
Turnkey hardware and software:
* [http://www.hotspotsystem.com/ HotSpotSystem.com]

=== Controlling "squatters" and "leeching" ===
Of varying effectiveness:
# Password from the operator that must be entered on the initial splash or signon page, changed periodically.
# WEP or WPA key that changes periodically.
# Drastically reduced transmit power on the access point.
# Distance measuring devices that can tell if the client is inside or outside.
# Turn off wireless during off hours.
# Don't provide electrical power (limiting use to battery capacity).
# Download quotas and [[wikipedia:Quality of service|Quality of Service]] (QoS). These are rule based quotas for what an individual client may download. QoS is also good for preventing a user from hogging all your bandwidth. However, administration is tricky and there are ways around quotas.

=== Mobile hotspot ===
* Mobile [[wikipedia:Recreational vehicle|RV]] systems
** [http://www.radiolabs.com/products/wireless/waverv.php WaveRV]
* RV hotspots
** [http://www.wififreespot.com/rv.html Free Wi-Fi in RV Parks and Campgrounds]
** [http://www.modemfriendly.com/ Guide to Modem Friendly Campgrounds]
** [http://www.rversonline.org/RVMFHSE.html List of Free or low cost WiFi RV Parks]
** [http://www.rvtravel.com/wifi.html RV Park WiFi Hotspots]
** [http://www.rv-wireless-internet.com/ RV Wireless Internet]
* RV hotspot providers
** [http://www.rvwifi.com/ RVwifi]
** [http://www.wifirv.com/ WiFiRV]

== Secure Internet access in a public hotspot ==
* Wireless transmissions on a public [[wikipedia:Hotspot (Wi-Fi)|hotspot]] are typically [[wikipedia:Encryption|unencrypted]], and thus '''exposed to snooping'''.
* All computers on a public hotspot are typically exposed to each other, and thus '''vulnerable to network attacks'''.

=== Use a software firewall ===
* A good software "[[wikipedia:Firewall (networking)|firewall]]" will protect your computer from network attacks.
* '''See ''[[Wi-Fi#Software Firewall|Wi-Fi Software Firewall]]''.'''

=== Secure network shares ===
* Use ''[[Wi-Fi#What Makes for a Strong Password or Passphrase?|strong passwords]]'' on ''all system accounts'' (including Administrator) and on ''all [[Wikipedia:User (computing)|user accounts]]''.
* Microsoft Windows
*# Use ''[http://support.microsoft.com/default.aspx?kbid=304040 Simple File Sharing]'' (Windows XP only); or
*# Make sure that ''all network shares are secured with strong passwords'' (all versions of Windows). Use ''Control Panel'' → ''Administrative Tools'' → ''Computer Management'' → ''Shared Folders'' → ''Shares'' to review and check ''Properties'' of all network shares.

=== Use SSL/TLS for email access ===
* Using standard [[wikipedia:Post Office Protocol|POP3]]/[[wikipedia:Simple Mail Transfer Protocol|SMTP]] email protocols for email over wireless is '''very dangerous''' because '''passwords aren't encrypted'''. '''''Use of '''[[wikipedia:Transport Layer Security|SSL/TLS]]''' is the best way to secure email connections.'''''
* Email connections can be secured by using a [[wikipedia:Web-based email|Web-based email]] (webmail) service that supports SSL/TLS connections. ''Make sure your browser displays a padlock icon (just below) throughout your email session.'' Such services include:
** Google Mail (Gmail) (free) '''''if''''' you use this link ''after ''login: https://mail.google.com/
* POP3/SMTP sessions can also be protected if the email provider supports SSL/TLS. Such providers include:
** [http://mail.google.com Google Mail] (Gmail) (free) (Help available on configuring many email clients)
* Even with SSL/TLS, '''email is still vulnerable to snooping''' on the public Internet unless individual messages are encrypted (''e.g., ''with [http://www.imc.org/smime-pgpmime.html S/MIME or OpenPGP]).

=== Use SSL/TLS for sensitive Web pages ===
* Use of ''any ''website for sensitive information (''e.g., ''social security number, credit card number, on-line banking, on-line investments, ''etc.'') should '''always be protected by means of [[wikipedia:Transport Layer Security|SSL/TLS]]'''. The [[wikipedia:Uniform Resource Locator|URL]] (link) should start with '''https'''. ''Make sure your browser displays a padlock icon ([https://.]) throughout your session.''

=== Use VPN to protect all transmissions ===
* VPN ([[wikipedia:Virtual private network|Virtual Private Networking]]) is used to construct and connect private networks using the public [[wikipedia:Internet|Internet]]. Communications are secured by means of some type of [[wikipedia:Encryption|encryption]], depending on the specific type of VPN. SSL VPN can offer a good solution to this security problem - www.thewifishop.net
* '''See ''[[Wi-Fi#VPN Service Providers|Wi-Fi VPN Service Providers]]''.'''

== Give Wi-Fi preference over wired Ethernet (or vice versa) ==

Interface [[wikipedia:Routing#Routed versus routing protocol|routing Metrics]] control which interface will be used at any given time.

=== Microsoft Windows ===

* Automatic route Metrics:
:{| border="1"
! Interface
! align="center" | Metric
|-
| align="right" | '''100'''BaseT wired Ethernet
| align="center" | 20
|-
| align="right" | 802.11'''a/g''' Wi-Fi
| align="center" | 25
|-
| align="right" | '''10'''BaseT wired Ethernet
| align="center" | 30
|-
| align="right" | 802.11'''b''' Wi-Fi
| align="center" | 30
|}

* To display route Metrics, Run<br><code>%COMSPEC% /K ROUTE PRINT</code>
** For which Interface is which IP address, Run<br><code>%COMSPEC% /K IPCONFIG /ALL</code>
** Preference is given to the lowest Metric, or to the first bound Interface for equal Metrics, as shown for ''Default Route''.

* Route Metrics can be controlled with the ''Interface Metric'' option in ''Advanced TCP/IP Settings'' for a Connection.
** To give Wi-Fi preference over any wired Ethernet, set the Metric of Wireless to 10.
** To give any wired Ethernet preference over Wi-Fi, set the Metric of Wireless to 40.

== Make a Wi-Fi antenna or reflector for cheap ==
* [http://www.FreeAntennas.com www.FreeAntennas.com]
** ''Really works!''
** Can help even when antenna isn't replaceable
* [[Wikipedia:Cantenna]]
* [http://www.oreillynet.com/cs/user/view/wlg/1124 Coffee Cantenna]
* [http://www.seattlewireless.net/DirectionalWaveguide?action=show&redirect=TinCantenna TinCantenna]
* [http://www.binarywolf.com/249/ Do-It-Yourself Wireless Antennas Update and Resource Center]
Amount of antenna improvement:
* Standard "rubber duck" [[wikipedia:Antenna gain|antenna gain]] (effectiveness) is about 2 dBi.
* It takes an ''increase of 6 dB to double range''. Thus:
:{| border="1"
| align="right" |  Antenna:
|   2 dBi 
|   8 dBi 
|   14 dBi 
|   ''etc.''  
|-
| align="right" |  Range:
| align="center" | 1x
| align="center" | 2x
| align="center" | 4x
| align="center" | ''...''
|}

== Add additional Wi-Fi access points (to increase coverage) ==
* Configure all access points with ''same [[wikipedia:Service set identifier|SSID]]''
* Ideally use different ''[[Wi-Fi#Wi-Fi Channels|minimally interfering channels]]'' (1, 6, 11)
* Place them:
** 'back-to-back' with [[wikipedia:Directional antenna|directional antennas]] in opposite directions, or
** in different locations.
* Additional access points best connected by wire to router, by means of
** Standard [[wikipedia:Ethernet|Ethernet]] cable
** [[wikipedia:HomePlug Powerline Alliance|Powerline networking]]
*** [http://www.actiontec.com/products/product.php?pid=48 Actiontec MegaPlug 85Mbps Powerline Ethernet Adapter Kit] (as low as $70 for the kit)
*** [http://www.linksys.com/servlet/Satellite?c=L_Product_C2&childpagename=US/Layout&cid=1166859583396&pagename=Linksys/Common/VisitorWrapper Linksys PLK200 PowerLine AV Ethernet Adapter Kit] (as low as $120 for the kit)
** [[wikipedia:HomePNA|Phoneline networking]]
** [[wikipedia:Multimedia over Coax Alliance|TV cable networking]] (Ethernet over coax)
*** [http://www.coaxsys.com/ Coaxsys]
*** [http://www.multilet.us/ Multilet]
* Wireless repeater or [[wikipedia:Wireless Distribution System|WDS]] can be used, but:
** Can be difficult to get working
** Wireless throughput is cut in half

== Configure a Wi-Fi client bridge ==

For background, see ''[[Fast Fixes to Wi-Fi Problems#Can't connect to Wi-Fi client bridge and Internet at the same time|Can't connect to Wi-Fi client bridge and Internet at the same time]]''.

'''Problem:''' The [[wikipedia:Network card|NIC]] on a local computer needs a manually-assigned IP on the same subnet to connect to the client bridge config interface but then can't access the Internet, and when configured for DHCP through the client bridge can then talk to the Internet but not the client bridge.

'''Solutions:'''
# [[wikipedia:Multihoming|Multihoming]] of the NIC (single link, multiple IP addresses)
#* For Microsoft Windows XP, see "Configuring Multiple IP Addresses on a Network Adapter" in [http://www.microsoft.com/technet/prodtechnol/winxppro/reskit/c24621675.mspx Configuring IP Addressing and Name Resolution]. ''Note:'' This only works with all manual addresses, not DHCP, which can be problematic when roaming unless managed with configuration manager software (see below)
# Two NICs in one computer, both connected to the client bridge:
#* one manually configured to talk to the client bridge config
#* the other with DHCP for the Internet
# Different computers for
#* client bridge config (manually configured)
#* Internet access (DHCP)
# Connection manager software for rapid changing of NIC configuration profiles
#* [http://www.boingo.com/download.html Boingo Wi-Fi software] (free)
#* [http://www.mobilenetswitch.com/ Mobile Net Switch]
#* [http://www.netswitcher.com/ NetSwitcher]

== Test and compare user interfaces ==
Product simulators:
* [http://support.dlink.com/faq/view.asp?prod_id=1457 D-Link]
* [http://www.linksysdata.com/ui/ Linksys]

== Wireless Broadband (3G) Routers ==
Use [[wikipedia:3G|3G]] cellular data instead of DSL or cable modem:
* [http://www.evdoinfo.com/ EVDO info]
* [http://www.junxion.com/ Junxion Box] (works with CDMA or GSM)
* [http://www.kyocera-wireless.com/kr1-router/ Kyocera KR1 Mobile Router]
* [http://www.nexusisr.com/ Nexus Hawk] (works with 802.11a/b/g, GSM and CDMA simultainiously)
* [http://www.topglobalusa.com/ Top Global routers]

{{Tip|tiptext=Use of cellular data service as a non-mobile DSL/cable modem replacement may be against the terms of service of a given carrier (''e.g., ''Verizon Wireless).}}

== Make shore Wi-Fi work better on a boat ==

See ''[[Wi-Fi on a Boat]]''

== Share USB devices over Wi-Fi ==

New bi-directional USB 2.0 servers provide more functionality than older USB servers, including support for multi-function printers.

* '''Wireless USB 2.0 servers'''
** [http://www.silexamerica.com/us/products/network/usb/index.php?option=com_content&task=view&id=31 Silex SX-2000WG Hi-Speed Wireless USB Device Server]
* '''Wired USB 2.0 servers''' (Can be adapted to Wi-Fi by cabling to [[Wi-Fi#Wireless Access Point|wireless access point]] or [[Wi-Fi#Wireless Router|wireless router]], or with a [[Wi-Fi#Wireless Ethernet Bridges|wireless Ethernet [client] bridge]].)
** [http://www.iogear.com/main.php?loc=product&Item=GMFPSU22W6 IOGEAR 2-Port USB 2.0 Multi-Function Print/Storage Server]
** [http://www.keyspan.com/products/u2s2a/homepage.spml Keyspan USB 2.0 Server]
** [http://www.zonetusa.com/DispProduct.asp?ProductID=237 Zonet ZPS2000 Multi-Function USB 2.0 Print Server]

== Share your Internet with a neighbor via Wi-Fi ==
* See:
** ''[[Wi-Fi#Wireless Isolation|Wireless Isolation]]''
** ''[[#Two wireless networks on one router|Two wireless networks on one router]]''
** ''[[#Setup a Hotspot|Setup a Hotspot]]''
{{Tip|tiptext=Opening up your Internet to outsiders may violate your ISP's terms of service and can be a serious security risk.}}

== Extend Wi-Fi through a brick wall ==

* Do you really need to go through a brick wall? Try going around the wall, with a directional antenna on the router site, and a reflector, above, below, or to the side of the wall. Reflectors can be as simple as a sheet of heavy aluminum foil, or you can use a pair of directional antennas wired back-to-back if more signal is needed.
* Run a cable from one of wireless router's antenna connectors around or (drilled) through the wall, and on the other side of the wall attach an antenna.
* Run Cat-5 or better cable from one of wireless router's RJ45 ports around or (drilled) through the wall, and on the other side of the wall attach a wireless access point.
* Use [[wikipedia:HomePlug Powerline Alliance|powerline]], [[wikipedia:HomePNA|phoneline]], or [[wikipedia:Multimedia over Coax Alliance|coax]] networking to attach a wireless access point on the other side of the wall, if any of these cables are available on both sides of the wall.

== Block Wi-Fi signal ==
[[wikipedia:Mobile phone jammer|Jamming]] isn't lawful (in the USA at least), but these methods are:
* Paint with [[wikipedia:Radio frequency|RF]] shielding (e.g., [http://www.lessemf.com/paint.html Y-Shield], claimed attenuation of 40 dB per layer)
* [http://www.baesystems.com/ProductsServices/ss_tes_atc_adv_mat_stealthy.html Stealthy wallpaper]
* [http://www.tempestusa.com/DataStop.html RF shielding glass]

== Roam seamlessly (using VPN) ==
Information:
* [http://www.mobileinfo.com/Hot_Topics/MobileIP.htm Mobile IP] (MobileInfo.com)
* RFC 2002 IP Mobility Support
* [http://www.isoc.org/inet2001/CD_proceedings/T40/inet_T40.htm Network design with Mobile IP]
Products:
* [http://www.birdstep.com/wireless_infrastructure/mobile_ip.php3 Birdstep Intelligent Mobile IP Client]
* [http://www.cisco.com/en/US/products/ps6744/products_data_sheet0900aecd8035da89.html Cisco Mobile Client for Windows 2000, XP]
* [http://www.ipunplugged.com/products.asp?mi=2.3 ipUnplugged]
* [http://www.ecutel.com/solutions/viatores.asp Viatores Mobile IP VPN]
{{TODO}}

== Wake on LAN ==
* See [[Wikipedia:Wake-on-LAN]]

* For Wake-on-LAN from 'outside' a router (''e.g.,'' over the Internet), what's needed is router support for ''directed broadcasts'', which most low-end routers lack because directed-broadcasts is a security risk (''e.g.,'' [[wikipedia:Smurf attack|Smurf attack]]) and isn't of much interest to the home/[[wikipedia:Small office/home office|SOHO]] market in any event. Thus this is normally found only in more sophisticated products.

* Products with Wake-On-LAN support:
** [http://www.buffalotech.com/products/product-detail.php?productid=88 Buffalo AirStation 125 High-Speed Mode Wireless Secure Remote Gateway]

== Make a Wi-Fi enclosure ==
{{TODO}}

== Microsoft Windows ==

=== File and Printer Sharing ===
* PracticallyNetworked
** [http://www.practicallynetworked.com/sharing/xp/filesharing.htm Windows XP Simple File Sharing]
** [http://www.practicallynetworked.com/sharing/xp_filesharing/index.htm Windows XP Professional File Sharing]
* Microsoft
** [http://www.microsoft.com/downloads/details.aspx?FamilyID=87C0A6DB-AEF8-4BEF-925E-7AC9BE791028&displaylang=en File and Printer Sharing with Microsoft Windows]
** [http://www.microsoft.com/downloads/details.aspx?familyid=fd7fd48d-6b4a-448e-a632-076f98a351a2&displaylang=en Troubleshooting File and Printer Sharing in Microsoft Windows XP]

=== Windows Security ===
* Windows XP
** [http://www.microsoft.com/downloads/details.aspx?familyid=2d3e25bc-f434-4cc6-a5a7-09a8a229f118&displaylang=en Windows XP Security Guide]
*** [http://www.microsoft.com/technet/security/prodtech/windowsxp/secwinxp/default.mspx Overview of the Windows XP Security Guide]
** [http://www.microsoft.com/downloads/details.aspx?familyid=9faba6ed-2e9c-44f9-bc50-d43d57e17078&displaylang=en Step-by-Step Guide to Securing Windows XP Professional in Small and Medium Businesses]
* Windows Vista
** [http://www.microsoft.com/downloads/details.aspx?familyid=A3D1BBED-7F35-4E72-BFB5-B84A526C1565&displaylang=en Windows Vista Security Guide]
* [http://www.microsoft.com/technet/security/default.mspx TechNet Security Center]

=== Troubleshooting Resources ===

* [http://support.microsoft.com/kb/313242/ How to troubleshoot wireless network connections in Windows XP]
* [http://support.microsoft.com/kb/314067/ How to troubleshoot TCP/IP connectivity with Windows XP]
* [http://support.microsoft.com/kb/102908/ How to Troubleshoot TCP/IP Connectivity with Windows 2000 or Windows NT]
* [http://support.microsoft.com/kb/325487/ How to troubleshoot network connectivity problems]
* [http://support.microsoft.com/kb/314095/ How to troubleshoot possible causes of Internet connection problems in Windows XP]
* [http://support.microsoft.com/kb/299357/ How to reset Internet Protocol (TCP/IP) in Windows XP]
* [http://support.microsoft.com/kb/813936/ How to Set Up a Small Network with Windows XP Home Edition]
* [http://support.microsoft.com/kb/308007/ How to troubleshoot home networking in Windows XP]
* [http://support.microsoft.com/kb/314073/ How to troubleshoot network printing problems in Windows XP]
* [http://support.microsoft.com/kb/243075/ How to Troubleshoot Network Printing Problems]
* [http://support.microsoft.com/kb/314831/ Basic L2TP/IPSec Troubleshooting in Windows XP]
* [http://support.microsoft.com/kb/837243/en-us Availability and description of the Port Reporter tool] (logs TCP and UDP port activity)
* [http://support.microsoft.com/kb/839013/en-us How to install the Microsoft Loopback adapter in Windows XP]

=== Configure manual IP address ===
# ''Start'' → ''Control Panel'' → ''Network Connections''
# Right-click on desired network connection, and select ''Properties'' on the pop-up menu
# Scroll the connection ''item'' list if necessary and double-click ''Internet Protocol (TCP/IP)''
# Select ''Use the following IP address''
# Enter desired ''IP address'' (must be in the ''same subnet'' as other local network devices, typically something like ''192.168.0.100'' or ''192.168.1.100'', depending on whether other devices are in ".0." or ".1." ''etc.'')
# Enter appropriate ''Subnet mask'' (typically ''255.255.0.0'')
# Enter ''Default gateway'' (often the address of your router, something like ''192.168.0.1'' or ''192.168.1.1'')
# If needed, configure ''DNS servers'' (obtained from your ISP)
# Click ''OK'' to close all windows

=== Configure automatic IP address ===
''e.g., ''by DHCP
# ''Start'' → ''Control Panel'' → ''Network Connections''
# Right-click on desired network connection, and select ''Properties'' on the pop-up menu
# Scroll the connection ''item'' list if necessary and double-click ''Internet Protocol (TCP/IP)''
# Select ''Obtain an IP address automatically''
# Select ''Obtain DNS server address automatically''
# Click ''OK'' to close all windows

=== Reset Internet Protocol (TCP/IP) in Windows XP ===
* See ''[http://support.microsoft.com/kb/299357/ How to reset Internet Protocol (TCP/IP) in Windows XP]'' (KB 299357)

=== Display network adapter configuration ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K IPCONFIG /ALL</code>
# Press [Enter]

=== Release DHCP lease ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K IPCONFIG /RELEASE</code>
# Press [Enter]

=== Renew DHCP lease ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K IPCONFIG /RENEW</code>
# Press [Enter]

=== Flush DNS cache ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K IPCONFIG /FLUSHDNS</code>
# Press [Enter]

=== Display ARP cache (table) ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K ARP -A</code>
# Press [Enter]

=== Flush ARP cache (table) ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K NETSH INTERFACE IP DELETE ARPCACHE</code>
# Press [Enter]

=== Display active network connections and listening ports ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K NETSTAT -A</code>
# Press [Enter]

=== Display Ethernet statistics ===
# Click ''Start'' → ''Run''
# Type:
#* <code>%COMSPEC% /K NETSTAT -E</code>   [standard display]
#* <code>%COMSPEC% /K NETSTAT -E -S</code>   [detailed display]
# Press [Enter]
* For a repeating display, add the repeat interval in seconds to the end of the above commands; ''e.g. ''<code>%COMSPEC% /K NETSTAT -E 10</code>   [repeats at 10 second intervals]
* '''See also ''[[Wi-Fi#Network Monitors|Wi-Fi Network Monitors]]''.'''

=== Display Windows networking connections ===
# Click ''Start'' → ''Run''
# Type:<br><code>%COMSPEC% /K NBTSTAT -S</code>
# Press [Enter]

[[Category:Wi-Fi]]

Wi-Fi

2009-03-15T20:21:02Z

JeffLiebermann: /* Performance and Speed */

{{Welcome}}
{{GoogleSearch}}
{{Contributions}}

{{Donate}}

'''This article covers the practical aspects of wireless access to the Internet via Wi-Fi.'''

{{Wi-Fi Articles}}

== Introduction to Wi-Fi ==
[[Image:Wi-Fi Logo.svg.png|thumb|Wi-Fi logo]]
[[wikipedia:Wi-Fi|Wi-Fi]] [[wikipedia:wireless|wireless]] [[wikipedia:Computer networking|networks]] provide all the functionality of wired networks, without the need for physical connections. Data is sent over various [[wikipedia:radio frequency|radio frequencies]] depending on the service. Typical Wi-Fi connection speeds are 11 and 54 [[wikipedia:Megabit per second|Mbps]]. In practice, throughput is about half the connection speed. Wireless Networks basically consists of computers equipped with wireless [[wikipedia:Network card|NICs]], which may be [[wikipedia:Universal Serial Bus|USB]], [[wikipedia:Peripheral Component Interconnect|PCI]], [[wikipedia:Mini PCI|Mini PCI]], [[wikipedia:Compact flash|CF]] card, [[wikipedia:PC card|PCMCIA/CardBus]], or other interface. Connectivity to a wired network requires a wireless ''access point'' (AP) used as a [[wikipedia:Bridging (networking)|bridging]] device. Connectivity to the Internet usually requires a ''wireless router'', which includes an access point. AP's are typically located near the centre of the wireless client concentration.

== Related Resources ==

* [[Wikipedia:Wi-Fi]]
* [[Wikipedia:IEEE 802.11]]
* [http://www.wifi-forum.com/ WiFi-Forum]
* [http://www.telecomspace.com/wirelessnw-wifi.html WiFi Resources]
* [http://www.practicallynetworked.com/ PracticallyNetworked.com] (reviews, troubleshooting and tutorials)
* [http://www.tomsnetworking.com/wireless_tn/index.html Tom's Networking: Wireless] (articles, reviews, and how to's)
* [http://scratchpad.wikia.com/wiki/MeshNetworking Locust world mesh networking wiki]
* [http://www.amw1.com/tips Setting up a wireless network]
* [http://www.microsoft.com/windowsxp/using/networking/default.mspx Home and Small Office Networking with Windows XP]
** [http://www.microsoft.com/windowsxp/using/networking/getstarted/default.mspx Get started with home networking]
** [http://www.microsoft.com/technet/prodtechnol/winxppro/maintain/wifisoho.mspx Configuring Windows XP IEEE 802.11 Wireless Networks for the Home and Small Business]

== The Three Rules of Wireless Networking ==
# It never goes as fast as they say it does<br>
# It never goes as far as they say it does<br>
# It never sets up as easily as they say it does<br>
: [[http://www.smallnetbuilder.com/content/view/24861/99/ Wireless Networking Need To Know 2006]]

== Getting Started ==

'''<big>See ''[http://www.smallnetbuilder.com/content/view/24861/99/ Wireless Networking Need To Know 2006]''</big>'''

== Essential Checklist ==
{|
| [[Image:CheckBox.gif]] || '''Use [[wikipedia:Wi-Fi Protected Access|WPA]] security'''. If you don't do this, assume ''you will get [[wikipedia:Hacker (computer security)|hacked]]''. ''[[wikipedia:Wired Equivalent Privacy|WEP]] is essentially worthless''. Replace wireless equipment that doesn't support WPA. Seriously. (''See [[#Wi-Fi Security|Wi-Fi Security]]'')
|-
| [[Image:CheckBox.gif]] || '''Use a ''strong'' WPA passphrase'''. A good way to do that is with [[wikipedia:Diceware|diceware]] words. (''See [[#What Makes for a Strong Password or Passphrase?|What Makes for a Strong Password or Passphrase?]]'') Write your passphrase on a label and stick it on the bottom of your wireless router so you won't forget it. (If someone gets to your wireless router, you are compromised regardless.)
|-
| [[Image:CheckBox.gif]] || '''Make your wireless [[wikipedia:Service set identifier|SSID]] unique'''. This helps avoid network collisions. A good way to do this is to use your address, phone number, and/or name for your SSID (making it easy for you to be contacted if something is wrong with your wireless network).
|-
| [[Image:CheckBox.gif]] || '''Don't bother with SSID hiding or [[wikipedia:MAC address|MAC address]] filtering'''. They ''don't do any real good'' (improve security) but they can ''cause you grief''. (''See [[#Wi-Fi Security Myths|Wi-Fi Security Myths]]'')
|-
| [[Image:CheckBox.gif]] || '''Turn off [[wikipedia:Universal Plug and Play|Universal Plug and Play]]''' (UPnP) in your wireless router. Because most consumer-grade wireless routers lack UPnP [[wikipedia:Authentication|authentication]] they are vulnerable to attack. (''See [[wikipedia:Universal Plug and Play#Lack of Authentication|Problems with UPnP, Lack of Authentication]]'')
|-
| [[Image:CheckBox.gif]] || '''Set a ''strong'' password''' on the administration interface of your wireless router. Again, [[wikipedia:Diceware|diceware]] is a good way to do that.
|-
| [[Image:CheckBox.gif]] || '''Turn off remote administration.''' If your wireless router supports remote administration, ''turn it off'' (unless you really know what you're doing).
|-
| [[Image:CheckBox.gif]] || '''Configure Windows ''not'' to connect to open networks automatically.''' See [http://compnetworking.about.com/od/wirelesshotspots/qt/noautoconnect.htm Do Not Auto-Connect to Open Wi-Fi Networks]
|-
| [[Image:CheckBox.gif]] || '''On unsecured Wi-Fi use [[#VPN|VPN]]''' (Virtual Private Networking). Otherwise your wireless traffic can be ''snooped and compromised''. ''(See [[Wi-Fi How To#Secure Internet access in a public hotspot|Secure Internet access in a public hotspot]])''
|}

== Wi-Fi Network Types ==

=== Infrastructure ===
[[Image:Infrastructure.png|thumb|right|Star topology of<br>Infrastructure WLAN]]
The [[wikipedia:Network topology|network topology]] of an Infrastructure [[wikipedia:Wireless LAN|Wireless LAN]] (WLAN) is a [[wikipedia:Point-to-multipoint|point-to-multipoint]] ''[[wikipedia:Star network|star]]'', with a single central controller (wireless access point or wireless router), and one or more wireless clients.
* Clients can connect to one and only one access point, and not to other clients.
* An access point can only connect to clients, not to other access points.
Some products can be switched between different modes; ''e.g., ''either an access point or a client bridge, but not both at the same time.

Most Wi-Fi WLANs are Infrastructure.

=== Ad Hoc ===
[[Image:AdHoc.png|thumb|right|Full Connected topology<br>of Ad Hoc WLAN]]
The [[wikipedia:Network topology|network topology]] of an [[wikipedia:Mobile ad-hoc network|Ad Hoc]] [[wikipedia:Wireless LAN|Wireless LAN]] (WLAN) is fully connected matrix, with two or more wireless clients connecting to each other, without any central controller.

Connecting an Ad Hoc network to other networks (''e.g.,'' the public [[wikipedia:Internet|Internet]]) typically involves [[wikipedia:Network bridge|bridging]] or [[wikipedia:Routing|routing]] in one of the wireless clients (''e.g.,'' [http://support.microsoft.com/kb/234815/ Windows Internet Connection Sharing]) to some other network connection.

== Wi-Fi Channels ==
Wi-Fi uses spectrum near 2.4 GHz, which is standardized and ''unlicensed'' by international agreement, although the exact frequency allocations vary slightly in different parts of the world, as does maximum permitted power. However, channel numbers are standardized by frequency throughout the world, so authorized frequencies can be identified by channel numbers.

<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td>     </td>
<td>
<table style="font-size: 90%; line-height: 1.1em;" border="1" cellpadding="0" cellspacing="0">
<tr>
<th colspan="8" bgcolor="#ffffee">Wi-Fi Channels </th>
</tr>
<tr>
<th bgcolor="#ffffee"> Channel  </th>
<th bgcolor="#ffffee"> Center Freq (GHz)  </th>
<th bgcolor="#ffffee"> Americas  </th>
<th bgcolor="#ffffee"> EMEA  </th>
<th bgcolor="#ffffee"> France  </th>
<th bgcolor="#ffffee"> Israel  </th>
<th bgcolor="#ffffee"> China  </th>
<th bgcolor="#ffffee"> Japan  </th>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">1 </td>
<td align="center" bgcolor="#ffffee">2.412 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">2 </td>
<td align="center" bgcolor="#ffffee">2.417 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">3 </td>
<td align="center" bgcolor="#ffffee">2.422 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">4 </td>
<td align="center" bgcolor="#ffffee">2.427 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">5 </td>
<td align="center" bgcolor="#ffffee">2.432 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">6 </td>
<td align="center" bgcolor="#ffffee">2.437 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">7 </td>
<td align="center" bgcolor="#ffffee">2.442 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">8 </td>
<td align="center" bgcolor="#ffffee">2.447 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">9 </td>
<td align="center" bgcolor="#ffffee">2.452 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">10 </td>
<td align="center" bgcolor="#ffffee">2.457 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">11 </td>
<td align="center" bgcolor="#ffffee">2.462 </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">12 </td>
<td align="center" bgcolor="#ffffee">2.467 </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">13 </td>
<td align="center" bgcolor="#ffffee">2.472 </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">Y </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
<tr>
<td align="center" bgcolor="#ffffee">14 </td>
<td align="center" bgcolor="#ffffee">2.484 </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">  </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee"> </td>
<td align="center" bgcolor="#ffffee">Y </td>
</tr>
</table>
</td>
</tr>
</table>
* EMEA = Europe, Middle East and Asia (except where otherwise specified)
* Maximum permitted power varies by region.
* Channel spacing is 0.005 GHz (5 MHz), except for channel 14 (which is ignored for much that follows).
* Each channels overlaps its neighbors, with the amount of interference decreasing the farther apart they are.
* Most interference is with the two adjacent channels in each direction (above and below); ''e.g., ''channel 6 mostly interferes with channels 4, 5, 7 and 8.
* There is significant interference with two more channels in each direction; ''e.g., '' channel 6 also has significant interference with channels 2, 3, 9 and 10.
* There can even be some interference beyond four channels in each direction, particularly with strong transmitters; ''e.g., '' channel 6 can interfere with channels 1 and 11.
* As a good rule of thumb, there should be minimal interference between channels that are ''five numbers apart'', except channel 14, which has minimal interference with other channels.
* In the USA:
** There are ''three minimum interference channels'': 1, 6, 11.
** For four channels with somewhat more interference that may still be usable, channels can be three or four numbers apart:
<table border="0" cellpadding="0" cellspacing="0" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="20%"></td>
<td>
<table border="1" cellspacing="0" cellpadding="2" width="100%">
<tr>
<th bgcolor="#FFFFEE" nowrap>Option #1</th>
<th bgcolor="#FFFFEE" nowrap>Option #2</th>
<th bgcolor="#FFFFEE" nowrap>Option #3</th>
</tr>
<tr>
<td align="center" bgcolor="#FFFFEE" nowrap>1, 4, 7, 11</td>
<td align="center" bgcolor="#FFFFEE" nowrap>1, 4, 8, 11</td>
<td align="center" bgcolor="#FFFFEE" nowrap>1, 5, 8, 11</td>
</tr>
</table>
</td>
</tr>
</table>
References:
* [http://www.itu.int/ITU-T/wtsa-04/files/itinfo_lan.doc Channels, Power Levels, and Antenna Gains]. ''Cisco Aironet 1200 Series Access Point Software Configuration Guide for VxWorks. ''Retrieved on 2007-06-18.
* Mitchell Burton (Cirond Technologies). [http://www.techonline.com/community/ed_resource/tech_paper/21668 Channel Overlap Calculations for 802.11b Networks]. (PDF) ''White Paper. ''TechOnLine (registration required but free). Retrieved on 2006-06-14.
* John Ross. [http://www.nostarch.com/download/wifi_01.pdf How Wi-Fi Works]. (PDF) ''The Book of Wi-Fi (ISBN 1-886411-45-X). ''No Starch Press (March 2003, 288 pp). Retrieved on 2006-06-14.
* [[Wikipedia:IEEE 802.11#Channels and international compatibility]]

== Wi-Fi Hardware ==

=== Wireless Access Point ===

A Wireless Access Point (AP) is the central bridge device used in an Infrastructure (as opposed to Ad Hoc) wireless network. (See [[Wi-Fi#Wi-Fi Network Types|Wi-Fi Network Types]]) Traffic from the wireless side of the bridge is sent to the [[wikipedia:Ethernet|Ethernet]] (wired) side of the bridge, and ''vice versa''. The wireless access point controls all traffic with wireless client radios.

'''Note''': A wireless router, which is often less expensive than a wireless access point, can be configured to work as just a wireless access point -- see [[Wi-Fi How To#Use a wireless router as a wireless access point|Wi-Fi How To Use a wireless router as a wireless access point]].

=== Wireless Router ===

A wireless router typically consists of three sections:
# ''[[wikipedia:Ethernet|Ethernet]] [[wikipedia:Router|router]]'', including:
#* [[wikipedia:Dynamic Host Configuration Protocol|DHCP]] client and server
#* [[wikipedia:Network address translation|NAT]]([[wikipedia:Port address translation|PAT]])
#* [[wikipedia:Firewall (networking)|Firewall]] (sometimes, not always -- ''NAT alone is '''not''' a real firewall'')
# ''Ethernet [[wikipedia:Network switch|switch]]''
# ''Wireless access point'' (radio)
Some boxes also include either:
* [[wikipedia:Digital Subscriber Line|DSL]] [[wikipedia:Modem|modem]]
* [[wikipedia:Cable modem|Cable modem]]
'''Note''': A wireless router, which is often less expensive than a wireless access point, can be configured to work as just a wireless access point -- see [[Wi-Fi How To#Use a wireless router as a wireless access point|Wi-Fi How To Use a wireless router as a wireless access point]].

=== Wireless Bridge ===

All [[wikipedia:IEEE 802.11|802.11]] wireless is [[wikipedia:Bridging (networking)|bridging]], where everything is done on [[wikipedia:Data link layer|Layer 2]].
[[wikipedia:IP address|IP addresses]] are used only for configuration of the access points. [[wikipedia:Wi-Fi|Wi-Fi]] encapsulates
[[wikipedia:IEEE 802.3|802.3 Ethernet]] [[wikipedia:Packet|packets]] inside 802.11 wireless packets.

==== Wireless Bridge Types ====

* Single [[wikipedia:MAC address|MAC address]] client adapter
: Common client radio used in workstations, laptops, and PDA's. Limited to connecting one computer to an infrastructure access point.

* Multiple MAC address client adapter
: Client wireless adapter that can bridge more than one MAC address. Used for connecting more than one computer via a single wireless link to an infrastructure access point.

* Point-to-point wireless bridge
: Two identical radios used to connect two networks. Same as transparent bridge. Will bridge more than one MAC address.

* Transparent bridges.
: Bridges more than one MAC address. Same as point to point bridge.

* Point-to-multipoint wireless bridge
: Three or more identical radios used to connect multiple networks. Bridge more than one MAC address

* Workgroup bridge
: Bridges a limited number of MAC addresses (usually 4, 8, or 16) to an infrastructure access point. (Examples: 3Com 3CRWE675075, 3CRWE83096A, Cisco AIR-WGB352)

* Game adapter
: Muddled marketing term for either a workgroup bridge or single MAC address client adapter. Bridges an indeterminant number of MAC addresses. Some do one MAC, some do more. Good luck.

* Wireless [[wikipedia:Repeater|repeater]]
: [[wikipedia:Store and forward|Store-and-forward]] repeater. Repeats all packets it hears for a configured [[wikipedia:Service set identifier|SSID]]. Also repeats all broadcasts. Used to extend the range or coverage of a wireless network.

* [[wikipedia:Wireless Distribution System|WDS]] bridge
: Simultaneously act as a bridge and as an access point. Used to extend the range or coverage of a network. Wireless users can connect to any WDS bridge as if were an access point. WDS bridge radios talk to each other as if they were transparent bridge radios.

* Wireless [[wikipedia:Ethernet|Ethernet]] [[wikipedia:Network switch|switch]]
: Multiple simple access point radios connected to a central intelligent switch. Offers centralized management and monitoring. Very easy to expand. Note that a switch is a bridge with more than two ports.

==== Wireless Ethernet Bridges ====
''Note: There are '''limits''' on how many units ([[wikipedia:MAC address|MAC addresses]]) these products are able to bridge (even with a separate wired hub or switch). Some (which may be called "game adapter") are only able to bridge a '''single''' MAC address. Some (but not necessarily all) bridges able to handle more than one MAC address are identified with '''multi''', with a number in parentheses if the specific limit is known. This information may '''not''' be reliable, and should be '''verified''' before making a purchase!''

* '''Actiontec'''
** [http://www.actiontec.com/products/home_networking/54mbps_eth_adapter/index.php 54 Mbps Wireless Ethernet Adapter]

* '''Airlink'''
** [http://www.airlink101.com/products/ap411w.php AP411W Super G Wireless Access Point] '''''multi'''''
** [http://www.airlink101.com/products/ap421w.php AP421W Super G Multi-function Access Point] '''''multi'''''
** [http://www.airlink101.com/products/ap431w.php AP431W Super G Multi-function Access Point] '''''multi'''''

* '''Alfa Network'''
** [http://dplanet.biz/alfa.com/ AIP-W610H High-Power 400mW 802.11b/g Router] '''''multi'''''<br>(support for access point, client bridge, WDS, and access point + WDS modes)

* '''Belkin'''
** [http://catalog.belkin.com/IWCatProductPage.process?Product_Id=136486 F5D7130 Wireless G Access Point] '''''multi'''''
** [http://catalog.belkin.com/IWCatProductPage.process?Product_Id=154416 F5D7330 Wireless G Gaming Adapter]

* '''Buffalo'''
** [http://www.buffalotech.com/products/product-detail.php?productid=118&categoryid=29 WLI-TX4-G54HP Wireless-G MIMO Performance Ethernet Converter] '''''multi'''''

* '''D-Link'''
** [http://www.dlink.com/products/?pid=383 DGL-3420 Wireless 108AG Gaming Adapter]
** [http://www.dlink.com/products/?pid=482 DPR-1260 RangeBooster G Multifunction Print Server]<br>''Can be used to bridge an Ethernet device.''
** [http://www.dlink.com/products/?pid=292 DWL-2100AP High Speed 2.4GHz (802.11g) Wireless 108Mbps Access Point] '''''multi'''''
** [http://www.dlink.com/products/?pid=303 DWL-2700AP Wireless 802.11g Outdoor AP/Bridge] '''''multi'''''
** [http://www.dlink.com/products/?pid=376 DWL-7700AP Wireless AG Outdoor AP/Bridge] '''''multi'''''
** [http://support.dlink.com/products/view.asp?productid=DWL%2D810%2B DWL-810+ Ethernet to Wireless Bridge] '''''multi'''''
** [http://support.dlink.com/products/view.asp?productid=DWL%2DG810 DWL-G810 Ethernet to Wireless Bridge]
** [http://www.dlink.com/products/?pid=333 DWL-G820 High-Speed Wireless Gaming Adapter]

* '''Hawking'''
** [http://www.hawkingtech.com/products/productlist.php?CatID=19&FamID=82&ProdID=177 HWBA54G Wireless-G Multi-Function AP/Bridge] '''''multi'''''

* '''Linksys'''
** [http://www.linksys.com/servlet/Satellite?c=L_Product_C2&childpagename=US%2FLayout&cid=1118334782530&pagename=Linksys%2FCommon%2FVisitorWrapper WET54G Wireless-G Ethernet Bridge] '''''multi'''''
** [http://www.linksys.com/servlet/Satellite?c=L_Product_C2&childpagename=US%2FLayout&cid=1115416829491&packedargs=site%3DUS&pagename=Linksys%2FCommon%2FVisitorWrapper WGA54AG Wireless A/G Game Adapter]
** [http://www.linksys.com/servlet/Satellite?c=L_Product_C2&childpagename=US%2FLayout&cid=1115416826619&packedargs=site%3DUS&pagename=Linksys%2FCommon%2FVisitorWrapper WGA54G Wireless-G Game Adapter]

* '''Motorola'''
** [http://broadband.motorola.com/consumers/products/we800g/ WE800G Wireless Ethernet Bridge]

* '''NETGEAR'''
** [http://www.netgear.com/Products/WirelessAccessPoints/WirelessAccessPoints/WAG102.aspx?detail=Specifications WAG102 ProSafe Dual Band Wireless Access Point] '''''multi'''''
** [http://www.netgear.com/Products/WirelessAccessPoints/WirelessAccessPoints/WAG302.aspx?detail=Specifications WAG302 ProSafe Dual Band Wireless Access Point] '''''multi'''''
** [http://www.netgear.com/Products/WirelessAccessPoints/WirelessAccessPoints/WG102.aspx?detail=Specifications WG102 Prosafe 802.11g Wireless Access Point] '''''multi'''''
** [http://www.netgear.com/Products/WirelessAccessPoints/WirelessAccessPoints/WG302.aspx?detail=Specifications WG302 Prosafe 802.11g Wireless Access Point] '''''multi'''''
** [http://www.netgear.com.au/products/prod_details.asp?prodID=209 WGE101 54 Mbps Wireless Ethernet Bridge] '''''multi'''''
** [http://www.netgear.com/Products/PrintServers/WirelessPrintServers/WGPS606.aspx WGPS606 54Mbps Wireless USB print server with 4-port switch] '''''multi'''''<br>''Can be used to bridge Ethernet devices.''

* '''SMC'''
** [http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=94&scid=&pid=365 SMC2582W-B EliteConnect Wireless Bridge] '''''multi'''''
** [http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=94&scid=&pid=1487 SMC2585W-G EliteConnect Wireless Bridge] '''''multi'''''
** [http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=94&scid=&pid=373 SMC2586W-G EliteConnect Wireless Bridge] '''''multi'''''
** [http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=5&scid=&pid=586 SMC2870W EZ Connect g Wireless Ethernet Bridge] '''''multi'''''
** [http://www.smc.com/index.cfm?event=viewProduct&localeCode=EN_USA&cid=5&scid=84&pid=1474 SMCWEBT-G EZ Connect g Wireless Ethernet Bridge] '''''multi'''''

=== Adapter Types ===

* [[Wikipedia:Peripheral Component Interconnect|PCI]]
* [[Wikipedia:Mini PCI|Mini PCI]]
* [[Wikipedia:Universal Serial Bus|USB]]
* [[Wikipedia:PC card|PC Card]]

=== Link Calculations ===

The easiest way to do this is by example. Your setup and numbers will vary. This is the [[wikipedia:Best, worst and average case|best case]] solution, with no consideration for atmospherics, [[wikipedia:Fresnel zone|Fresnel zone]] edge diffraction, folliage attenuation, and non-line of sight effect. [[wikipedia:Fade margin|Fade margin]] only gets worse, never better.

We'll use a pair of Linksys [http://www.linksysinfo.org/modules.php?name=Content&pa=showpage&pid=6 WRT54G v4] 802.11g with [http://www.dd-wrt.com DD-WRT] alternative firmware setup as a transparent bridge. This makes it easy because both sides are the same. The transmit output is about +17 [[wikipedia:DBm|dBm]]. The WRT54G will be mounted in a weatherproof box somewhere near the antenna with a single 3 ft cable (pigtail) using LMR-240 [[wikipedia:Coaxial cable|coax]] with a loss of about 4 [[wikipedia:Decibel|dB]] including connectors.

Next, we gotta do some guesswork. I'll assume that we can live with about 6 [[wikipedia:Megabit per second|Mbits/sec]] [[wikipedia:Throughput|thruput]]. That means the connection speed will be about twice that or 12 Mbits/sec. The receiver sensitivity varies with the speed and modulation type. The following is from the Dlink DI-624 datasheet but is close enough for most similar 802.11g radios:

<table border="0" cellpadding="0" cellspacing="0" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="30">
</td>
<td>
<div align="center">
<table border="1" cellspacing="0" width="100%" cellpadding="2">
<tr height="17" >
<th bgcolor="#FFFFEE" >Mbps</th>
<th bgcolor="#FFFFEE" >Type</th>
<th bgcolor="#FFFFEE" >PER</th>
<th bgcolor="#FFFFEE" >dBm</th>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >54</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-68</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >48</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-68</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >36</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-75</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >24</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-79</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >18</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-82</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >12</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-84</td>
</tr>
</table>
</div>
</td>
<td width="20" ></td>
<td>
<div align="center">
<table border="1" cellspacing="0" width="100%" cellpadding="2">
<tr height="17" >
<th bgcolor="#FFFFEE" >Mbps</th>
<th bgcolor="#FFFFEE" >Type</th>
<th bgcolor="#FFFFEE" >PER</th>
<th bgcolor="#FFFFEE" >dBm</th>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >11</td>
<td align="center" bgcolor="#FFFFEE" >CCK</td>
<td align="center" bgcolor="#FFFFEE" >8%</td>
<td align="center" bgcolor="#FFFFEE" >-82</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >9</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-87</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >6</td>
<td align="center" bgcolor="#FFFFEE" >OFDM</td>
<td align="center" bgcolor="#FFFFEE" >10%</td>
<td align="center" bgcolor="#FFFFEE" >-88</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >5.5</td>
<td align="center" bgcolor="#FFFFEE" >CCK</td>
<td align="center" bgcolor="#FFFFEE" >8%</td>
<td align="center" bgcolor="#FFFFEE" >-85</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >2</td>
<td align="center" bgcolor="#FFFFEE" >QPSK</td>
<td align="center" bgcolor="#FFFFEE" >8%</td>
<td align="center" bgcolor="#FFFFEE" >-86</td>
</tr>
<tr height="17" >
<td align="center" bgcolor="#FFFFEE" >1</td>
<td align="center" bgcolor="#FFFFEE" >BPSK</td>
<td align="center" bgcolor="#FFFFEE" >8%</td>
<td align="center" bgcolor="#FFFFEE" >-89</td>
</tr>
</table>
</div>
</td>
</tr>
</table>

12 Mbps connect speed thus sets the receiver sensitivity at -84 dBm.

'''PER''' (Packet Error Rate) is similar to BER (Bit Error Rate) but is easier to measure. You would not want to operate at a 10% PER error rate. 1 in 10 packets trashed is useable, but no fun. This is approximately the same as a BER of 1E10<sup>5</sup>, which is one of the common reference levels for measuring receiver sensitivity. Again, these are measurement reference levels, not operating points.

Next, we must guess the fade margin. Fade margin or system operating margin is how much stronger the
operating level is above the receiver reference level. 20 dB is considered to be a good minimum. In other words, your operating signal level must be 100 times stronger than the receiver sensitivity
or the link is going to be flaky and unreliable.

The relationship between fade margin and reliability is:
<table border="0" cellpadding="0" cellspacing="0" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="30"></td>
<td>

<table border=1 cellpadding=2 cellspacing=0 width=100%>
<tr height=17>
<th bgcolor="#FFFFEE">SOM dB</th>
<th bgcolor="#FFFFEE">Reliability %</th>
<th bgcolor="#FFFFEE">Downtime per
year</th>
</tr>
<tr height=17>
<td>

<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=right bgcolor="#FFFFEE">8</td>
<td bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">18</td>
<td bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">28</td>
<td bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">38</td>
<td bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">48</td>
<td bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">58</td>
<td bgcolor="#FFFFEE"> </td>
</tr>
</table>

</td>
<td>

<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=right bgcolor="#FFFFEE">90</td>
<td bgcolor="#FFFFEE"></td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">99</td>
<td bgcolor="#FFFFEE"></td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">99</td>
<td bgcolor="#FFFFEE">.9</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">99</td>
<td bgcolor="#FFFFEE">.99</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">99</td>
<td bgcolor="#FFFFEE">.999</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">99</td>
<td bgcolor="#FFFFEE">.9999</td>
</tr>
</table>

</td>
<td align=right>

<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=right bgcolor="#FFFFEE">876</td>
<td bgcolor="#FFFFEE"></td>
<td bgcolor="#FFFFEE">hours</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">88</td>
<td bgcolor="#FFFFEE"></td>
<td bgcolor="#FFFFEE">hours</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">8</td>
<td bgcolor="#FFFFEE">.8</td>
<td bgcolor="#FFFFEE">hours</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">53</td>
<td bgcolor="#FFFFEE"></td>
<td bgcolor="#FFFFEE">minutes</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">5</td>
<td bgcolor="#FFFFEE">.3</td>
<td bgcolor="#FFFFEE">minutes</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">32</td>
<td bgcolor="#FFFFEE"></td>
<td bgcolor="#FFFFEE">seconds</td>
</tr>
</table>

</td>
</tr>
</table>

</td>
</tr>
</table>
99% reliability might sound great, but that means your link will be useless for 1% of the year, or 3.6 days per year. Don't go below 20 dB fade margin, which is 70 hours of downtime per year.

Plugging the above guesswork into a suitable [http://www.terabeam.com/support/calculations/som.php Link Calculator] and trying various [[wikipedia:Antenna gain|antenna gains]] until we get a 20 dB fade margin:
<table border="0" cellpadding="0" cellspacing="0" width="60%" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="30"></td>
<td>
<table border="1" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td>
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>TX power </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>TX coax loss </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>TX ant gain </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>Distance </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>RX ant gain </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>RX coax loss </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>RX sens </td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFEE" nowrap>Fade margin </td>
</tr>
</table>
</td>
<td>
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr>
<td bgcolor="#FFFFEE" nowrap> +15 dBm</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> 4 dB (3 ft LMR-240 plus a mess of
connectors)</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> unknown</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> 2 miles</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> unknown</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> 4 dB (same at other end)</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> -84 dBm (at 12 Mbits/sec)</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> 20 dB</td>
</tr>
</table>
</td>
</tr>
</table>
</td>
</tr>
</table>
yields a minimum antenna gain of +21 dBi. Any less than +21 dBi antenna gain will result in insufficient fade margin and a corresponding loss in link reliability. That makes the required antenna to be a [[wikipedia:Parabolic antenna|dish]]. We can use a lower gain antenna by running at a slower speed, shorter coax, or more transmit power at ''both'' ends.

'''Online link calculators:'''
* [http://www.terabeam.com/support/calculations/som.php System Operating Margin (Terabeam Wireless)]
* [http://my.athenet.net/~multiplx/cgi-bin/wireless.main.cgi Wireless Network Link Analysis (Green Bay Professional Packet Radio)]
* [http://www.connect802.com/antenna_c_main.php Antenna System Designer (Connect802)]

=== Performance and Speed ===

Wireless connection speed and thruput are quite different. The wireless may offer a connection speed of 54 Mbits/sec, but the actual thruput is considerably less, typically less than half. That's because of management packet overhead, [[wikipedia:IEEE 802.11|802.11b]] compatibility, inter-symbol gaps, and necessary timing delays. Also, note that wireless is [[wikipedia:Duplex (telecommunications)|half-duplex]], where only one radio in a given airspace can transmit at a time.

This is taken from an [http://www.atheros.com/pt/whitepapers/atheros_range_whitepaper.pdf Atheros paper] with some additions and corrections.
<table border="0" cellpadding="0" cellspacing="0" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="30"></td>
<td>
<table border=1 cellpadding=2 cellspacing=0 width="100%">
<tr height=17>
<th bgcolor="#FFFFEE">Wi-Fi type</th>
<th bgcolor="#FFFFEE">Non-overlapping<br>
Channels</th>
<th bgcolor="#FFFFEE">Modulation</th>
<th bgcolor="#FFFFEE">Max Link</th>
<th bgcolor="#FFFFEE">Max TCP</th>
<th bgcolor="#FFFFEE">Max UDP</th>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE" align="left" nowrap> 802.11b only</td>
<td align=center bgcolor="#FFFFEE">  3</td>
<td align="center" bgcolor="#FFFFEE">CCK</td>
<td align=center bgcolor="#FFFFEE">  11</td>
<td align=center bgcolor="#FFFFEE">  5.9</td>
<td align=center bgcolor="#FFFFEE">  7.1</td>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE" align="left" nowrap> 802.11g with 802.11b </td>
<td align=center bgcolor="#FFFFEE">  3</td>
<td align="center" bgcolor="#FFFFEE">OFDM/CCK</td>
<td align=center bgcolor="#FFFFEE">  54</td>
<td align=center bgcolor="#FFFFEE">14.4</td>
<td align=center bgcolor="#FFFFEE">19.5</td>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE" align="left" nowrap> 802.11g only</td>
<td align=center bgcolor="#FFFFEE">  3</td>
<td align="center" bgcolor="#FFFFEE">OFDM</td>
<td align=center bgcolor="#FFFFEE">  54</td>
<td align=center bgcolor="#FFFFEE">24.4</td>
<td align=center bgcolor="#FFFFEE">30.5</td>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE" align="left" nowrap> 802.11g turbo</td>
<td align=center bgcolor="#FFFFEE">  1</td>
<td align="center" bgcolor="#FFFFEE">OFDM</td>
<td align=center bgcolor="#FFFFEE">108</td>
<td align=center bgcolor="#FFFFEE">42.9</td>
<td align=center bgcolor="#FFFFEE">54.8</td>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE" align="left" nowrap> 802.11a</td>
<td align=center bgcolor="#FFFFEE">13</td>
<td align="center" bgcolor="#FFFFEE">OFDM</td>
<td align=center bgcolor="#FFFFEE">  54</td>
<td align=center bgcolor="#FFFFEE">24.4</td>
<td align=center bgcolor="#FFFFEE">30.5</td>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE" align="left" nowrap> 802.11a turbo</td>
<td align=center bgcolor="#FFFFEE">  6</td>
<td align="center" bgcolor="#FFFFEE">OFDM</td>
<td align=center bgcolor="#FFFFEE">108</td>
<td align=center bgcolor="#FFFFEE">42.9</td>
<td align=center bgcolor="#FFFFEE">54.8</td>
</tr>
</table>
</td>
</tr>
</table>
The paper claims that encryption is enabled for these calculations, but the numbers seem to indicate that these number are for encryption disabled. (Don't know for sure.) The maximum [[wikipedia:Transmission Control Protocol|TCP]] and maximum [[wikipedia:User Datagram Protocol|UDP]] are the theoretical maximum [[wikipedia:Throughput|throughput]] rates. No calculations for Turbo and SuperG modes yet.

There is also a relationship between speed and range. The following table is from a paper by Intel on
[ftp://download.intel.com/business/bss/infrastructure/wireless/deployment/hotspot.pdf wireless hotspot deployment] for 802.11b/g.
<table border="0" cellpadding="0" cellspacing="0" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="30"></td>
<td>
<table border=1 cellpadding=2 cellspacing=0 width=100%>
<tr height=17>
<th width=50% bgcolor="#FFFFEE" nowrap>Rate Mbps</th>
<th width=50% bgcolor="#FFFFEE" nowrap>Range ft</th>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE">
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=right bgcolor="#FFFFEE">1</td>
<td bgcolor="#FFFFEE"></td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">2</td>
<td bgcolor="#FFFFEE"></td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">5</td>
<td bgcolor="#FFFFEE">.5</td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">6</td>
<td bgcolor="#FFFFEE"></td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">9</td>
<td bgcolor="#FFFFEE"></td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">11</td>
<td bgcolor="#FFFFEE"></td>
</tr>
</table>
</td>
<td bgcolor="#FFFFEE">
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=center bgcolor="#FFFFEE">350</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">250</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">180</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">300</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">250</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">150</td>
</tr>
</table>
</td>
</tr>
</table>
</td>
<td width="20"></td>
<td>
<table border=1 cellpadding=2 cellspacing=0 width=100%>
<tr height=17>
<th width=50% bgcolor="#FFFFEE" nowrap>Rate Mbps</th>
<th width=50% bgcolor="#FFFFEE" nowrap>Range ft</th>
</tr>
<tr height=17>
<td bgcolor="#FFFFEE">
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=right bgcolor="#FFFFEE">12</td>
<td align=left bgcolor="#FFFFEE">   </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">18</td>
<td align=left bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">24</td>
<td align=left bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">36</td>
<td align=left bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">48</td>
<td align=left bgcolor="#FFFFEE"> </td>
</tr>
<tr height=17>
<td align=right bgcolor="#FFFFEE">54</td>
<td align=left bgcolor="#FFFFEE"> </td>
</tr>
</table>
</td>
<td bgcolor="#FFFFEE">
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=17>
<td align=center bgcolor="#FFFFEE">200</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">170</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">140</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">100</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">  95</td>
</tr>
<tr height=17>
<td align=center bgcolor="#FFFFEE">  90</td>
</tr>
</table>
</td>
</tr>
</table>
</td>
</tr>
</table>
The rather optimistic ranges listed are probably with a better than standard [[wikipedia:Omnidirectional antenna|omnidirectional antenna]] and with unobstructed [[wikipedia:Line of sight|line of sight]]. There are similar charts in the Intel [[wikipedia:Hotspot (wifi)|Wi-Fi hotspot]] paper for other [[wikipedia:Radio frequency|frequencies]] and [[wikipedia:Communications protocol|protocols]].

=== Attenuation ===
Solid objects greatly [[wikipedia:Attenuation|attenuate]] (reduce) Wi-Fi radio signals, so clear line of sight is best. The amount of attenuation is expressed in dB, where each 3 dB of attenuation is a power loss of 1/2.

==== Indoor ====
:{| border="1" cellpadding="2" cellspacing="0" width="60%" style="background:#FFFFEE; font-size:90%; line-height:1.1em;"
|+'''Attenuation Properties of Common Building Materials'''
!Building Material
!2.4 GHz Attenuation
|-
|Solid Wood Door 1.75"
|align="center"|  6 dB
|-
|Hollow Wood Door 1.75"
|align="center"|  4 dB
|-
|Interior Office Door w/Window 1.75"/0.5"
|align="center"|  4 dB
|-
|Steel Fire/Exit Door 1.75"
|align="center"|13 dB
|-
|Steel Fire/Exit Door 2.5"
|align="center"|19 dB
|-
|Steel Rollup Door 1.5"
|align="center"|11 dB
|-
|Brick 3.5"
|align="center"|  6 dB
|-
|Concrete Wall 18"
|align="center"|18 dB
|-
|Cubical Wall (Fabric) 2.25"
|align="center"|18 dB
|-
|Exterior Concrete Wall 27"
|align="center"|53 dB
|-
|Glass Divider 0.5"
|align="center"|12 dB
|-
|Interior Hollow Wall 4"
|align="center"|  5 dB
|-
|Interior Hollow Wall 6"
|align="center"|  9 dB
|-
|Interior Solid Wall 5"
|align="center"|14 dB
|-
|Marble 2"
|align="center"|  6 dB
|-
|Bullet-Proof Glass 1"
|align="center"|10 dB
|-
|Exterior Double Pane Coated Glass 1"
|align="center"|13 dB
|-
|Exterior Single Pane Window 0.5"
|align="center"|  7 dB
|-
|Interior Office Window 1"
|align="center"|  3 dB
|-
|Safety Glass-Wire 0.25"
|align="center"|  3 dB
|-
|Safety Glass-Wire 1.0"
|align="center"|13 dB
|}
:[Source: [http://www.3com.com/other/pdfs/products/en_US/101900.pdf 3Com Wireless Antennas Product Guide]]

==== Outdoor ====
{{TODO}}

=== Repeaters ===
{{TODO}}

=== Antennas ===
==== Antenna Manufacturers ====
* [[#Hawking|Hawking]]
* [[#Linksys|Linksys]]

==== Do It Yourself ====
* See [[Wikibooks:Wifi:Building an antenna]]
* [http://www.ab9il.net/wlan-projects/wifi1.html AB9IL WLAN Antenna Projects]

=== Manufacturers ===

==== Belkin ====
* '''[http://belkin.com Belkin home page]'''

==== Buffalo Technology ====
* '''[http://buffalotech.com Buffalo Technology home page]'''
* [http://buffalotech.com/products/product-detail.php?productid=117&categoryid=30 WHR-G54S Wireless-G High Speed Router & Access Point]
** [http://www.gilanet.com/ohlandl/NIC/whr-g54s.html Notes on the Buffalo Technology WHR-G54S]

==== D-Link ====
* '''[http://dlink.com D-Link home page]'''
* [ftp://ftp.dlink.com/Gateway/ Firmware downloads] (including [[Wikipedia:Release cycle|beta]] versions)
* [http://support.dlink.com/faq/view.asp?prod_id=1457 Product simulators] (user interfaces)

==== Hawking Technology ====
* '''[http://hawkingtech.com Hawking Technology home page]'''
* [http://www.hawkingtech.com/products/index.php?CatID=32&FamID=58 High-Gain Range Extending Antennas]
* [http://hawkingtech.com//support/details.php?CatID=19&FamID=13&ProdID=147&Rev=M HWR54G Hi-Speed Wireless-G Router] '''''Revision M'''''
** '''BUG:''' Firmware Version 1.0 Release 11 is unable to properly renew DHCP leases on [http://comcast.com/Benefits/CHSIBenefits.asp?LinkID=51 Comcast cable Internet]. '''Fixed in Version 1.1 Release 22'''. As of May 2006, the only way to get this firmware is by an '''[mailto:techsupport@hawkingtech.com?subject=HWR54G%20Rev%20M%20firmware%20Version%201.1%20Release%2022%20(or%20later) email request to Hawking Support]''' ''('''not''' phone)''.

==== Intel ====
* '''[http://www.intel.com/network/connectivity/products/wireless/index.htm Intel Wireless Networking]'''

==== Linksys ====
* '''[http://linksys.com Linksys home page]''' (part of [http://cisco.com Cisco Systems])
* Antennas
** [http://www.linksys.com/servlet/Satellite?blobcol=urldata&blobheadername1=Content-Type&blobheadername2=Content-Disposition&blobheadervalue1=application%2Fpdf&blobheadervalue2=inline%3B+filename%3DHGA7S-DS%252C0.pdf&blobkey=id&blobtable=MungoBlobs&blobwhere=1130803982737&ssbinary=true HGA7S High-Gain (7 dBi) Omni with R-SMA connector]
** [http://www.linksys.com/servlet/Satellite?blobcol=urldata&blobheadername1=Content-Type&blobheadername2=Content-Disposition&blobheadervalue1=application%2Fpdf&blobheadervalue2=inline%3B+filename%3Dhga7t-ds.pdf&blobkey=id&blobtable=MungoBlobs&blobwhere=1130803982775&ssbinary=true HGA7T High-Gain (7 dBi) Omni with R-TNC connector]
* [http://www.linksysInfo.org LinksysInfo.org] Good source of information on Linksys products
* [http://www.linksysdata.com/ui/ Product simulators] (user interfaces)
* [[Wikipedia:WRT54G]] (including related models)

==== Motorola ====
* '''[http://broadband.motorola.com/consumers/home_networking.asp Motorola Home Networking]'''
* [http://broadband.motorola.com/consumers/products/wps870g/default.asp WPS870G Wireless Print Server]
** 6/2006: WPA-PSK reportedly doesn't work. Replace product with something else.

==== NETGEAR ====
* '''[http://netgear.com NETGEAR home page]'''
* WG511 PC Card
** Version 1 (v1) has about the best range and performance of readily available 802.11g PC Card adapters
** Version 2 (v2), a different design, isn't as good as Version 1.

==== 3Com ====
* '''[http://www.3com.com/wireless 3Com Wireless]'''

==== 2Wire ====
* '''[http://www.2wire.com/ 2Wire home page]'''

=== 3rd-party Firmware ===
Replacing the standard firmware in certain wireless routers and access points (''e.g.,'' [[wikipedia:WRT54G|Linksys WRT54GL]]) can provide greatly increased functionality (''e.g.'' [[wikipedia:Hotspot (Wi-Fi)|hotspot]] capability) and improved stability, although a fair amount of technical skill may be needed. For specific features and supported products, see:
* '''[http://www.dd-wrt.com/dd-wrtv2/ddwrt.php DD-WRT]'''
** [http://www.howtoforge.com/wifi_hotspot_setup How To Setup a Wi-Fi Hotspot]
** [http://www.sputnik.com/ Sputnik] (for setting up secure hotspots)
* '''[http://openwrt.org/ OpenWRT]'''
** [http://www.chillispot.org/ ChilliSpot] (for setting up secure hotspots)
** [http://wiki.openwrt.org/HotspotOpenvpnHowto?highlight=%28HowTo%29 HotspotOpenvpnHowto] (hotspot with private VPN access)
** [http://www.wifitastic.com/ WiFiTastic] (for setting up secure hotspots)
* '''[http://www.sveasoft.com/ Sveasoft]'''

Replacing the standard firmware in certain wireless routers and access points (''e.g.,'' [[wikipedia:rtl8186|ZyxelP330W]]) can provide greatly increased functionality (''e.g.'' [[wikipedia:Hotspot (Wi-Fi)|hotspot]] capability) and improved stability, although a fair amount of technical skill may be needed. For specific features and supported products, see:

* '''[http://rtl8186.sf.net Wive (firmware for rtl8186 SoC based routers)]'''
* '''[http://wive-ng.sf.net Wive-NG (next generation firmware for rtl8186 SoC based routers)]'''

== Wi-Fi Software ==
=== Connection Managers ===
Software for rapid changing of network configuration profiles.
* [http://www.boingo.com/download.html Boingo Wi-Fi software] (free)
* [http://www.mobilenetswitch.com/ Mobile Net Switch]
* [http://www.netswitcher.com/ NetSwitcher]

=== Network Monitors ===
Monitor network throughout, amount of data sent/received, ''etc.'' Recommended products are shown in bold.
* [http://www.snapfiles.com/get/bwvista.html Bandwidth Vista]
* [http://www.e-systems.ro/bandwidth_monitor.htm Emsa Bandwidth Monitor]
* '''[http://www.snapfiles.com/get/novatrafstats.html MZL & Novatech TrafficStatistic]'''
* '''[http://readerror.gmxhome.de/ NetMeter]'''
* [http://www.snapfiles.com/get/netmon.html Netmon]
* [http://www.snapfiles.com/get/netspeed.html NetSpeed]
* [http://www.analogx.com/contents/download/network/nsl.htm NetStat Live]
* [http://majorgeeks.com/Network_Traffic_Monitor_d1858.html Network Traffic Monitor]
* '''[http://www.snapfiles.com/get/tslanmon.html Tong Software LAN Monitor]'''
* [http://www.snapfiles.com/get/itindicator.html Interface Traffic Indicator]

=== Site Survey Tools ===
''See [[Wi-Fi How To#Why and How to do a Site Survey|Why and How to do a Site Survey]]''
* Free tools
** [http://www.kismetwireless.net/ Kismet]
** [http://www.stumbler.net/ Network Stumbler]

=== WEP cracking ===
* [http://airsnort.shmoo.com/ Airsnort]

== Wi-Fi Speed ==
* The raw speed reported by your wireless network adapter is ''not'' necessarily a reliable indicator of actual raw speed. The reason is that transmit speed fluctuates according to the wireless error rate, and when the wireless link is idle, unrealistic speed may be reported (since no errors are occuring when the wireless link is idle).
* Data can only flow on ''one'' wireless link in ''one'' direction at any one time, which means that the ''maximum data transfer rate will be well below half of the raw wireless network speed''.
* To measure Wi-Fi speed, see ''[[Wi-Fi How To#Measure wireless network performance|Wi-Fi How To Measure wireless network performance]]''.

== Wi-Fi Safety ==

=== Anti-Virus (free) ===
''If you're not already protected, then you're probably already infected!''

'''Resident protection'''
* [http://www.free-av.com/ Avira AntiVir Personal Edition Classic]
** Very good, but occasionally pops up a ''nag screen''
*** ''[http://groups.google.com/group/alt.comp.anti-virus/msg/909eb6a8756fd6f0 How to eliminate the nag screen] (Windows XP Pro only)''
* '''[http://comodo.com COMODO Internet Security] (very good, includes very good firewall)'''
* [http://free.grisoft.com/ Grisoft AVG Free]
** Not quite as good, but still very good, and ''no nagging''
'''Online scanners''' (good when you think you might be infected)
* [http://housecall.trendmicro.com/ Trend Micro HouseCall]
* [http://www.pandasoftware.com/products/activescan/ Panda ActiveScan]
* [http://www.kaspersky.com/scanforvirus Kaspersky Lab]
* [http://us.mcafee.com/root/mfs/ McAfee FreeScan]

=== Anti-Spyware (free) ===
''Run only one resident protection at any given time.<br>(Multiple scanners are OK, and may be needed in difficult cases.)''
* '''[http://www.microsoft.com/athome/security/spyware/software/ Microsoft Defender]'''
** Very good protection
** Only works on [http://www.microsoft.com/genuine/downloads/WhyValidate.aspx?displaylang=en "genuine" Windows]
'''Other good anti-spyware''' (''e.g., ''for on-demand scanning)
* [http://www.lavasoft.com/software/adaware/ Ad-Aware Free] (not effective against all threats)
* [http://www.safer-networking.org/ Spybot Search & Destroy] (not effective against all threats)
'''Diagnostic tools for spyware'''
* [http://www.tomcoyote.org/hjt/ HijackThis]

== Wi-Fi Security ==

*See:
** [[wikibooks:Wifi:Security|WiFi:Security]]
** [http://www.drizzle.com/~aboba/IEEE/ The Unofficial 802.11 Security Web Page]
** [http://blogs.zdnet.com/Ou/index.php?p=42 Simple advice for securing your home wireless LAN]

=== Wi-Fi Security Myths ===

* '''[http://blogs.zdnet.com/Ou/index.php?p=43 The six dumbest ways to secure a wireless LAN]''' (Wireless LAN security hall of shame)
** MAC filtering (absolutely worthless)
** SSID hiding (doesn't really work, causes needless grief)
*** [http://www.trusecure.com/cgi-bin/download.cgi?ESCD=W0149&file=wp_ssid_hiding.pdf Debunking the Myth of SSID Hiding] (registration required)
** LEAP authentication (can be rapidly cracked)
** Disable DHCP (waste of time)
** Antenna placement (hackers have better antennas than you do)
** Just use 802.11a or Bluetooth (have nothing to do with security)
* '''[http://www.oreillynet.com/pub/a/wireless/excerpt/wirlsshacks_chap1/ Dispelling the Myth of Wireless Security]'''

=== Intruder Detection ===

* [http://home.comcast.net/~jay.deboer/airsnare/ AirSnare]

=== WEP ===
* See [[Wikipedia:Wired Equivalent Privacy]] (WEP)
* ''WEP can be easily cracked and is ''not'' secure. Use WPA instead.''
** [http://www.smallnetbuilder.com/content/view/24244/98/ How To Crack WEP]
** [http://www.securityfocus.com/infocus/1814 WEP: Dead Again]
* WEP keys can usually be entered in either ''ASCII format ''(all letters, numbers, ''etc.'') or ''hex (hexadecimal) format ''(only 0-9 and A-F), and the difference can result in (frustrating) key mismatch. To avoid this problem, ''enter all keys in hex'' (using only symbols 0-9 and A-F).
<table border="0" cellpadding="0" cellspacing="0" style="font-size:90%; line-height:1.1em;">
<tr>
<td width="40"> </td>
<td>
<table border="1" cellspacing="0" cellpadding="2">
<tr>
<th rowspan="2" bgcolor="#FFFFEE" nowrap> WEP Type (Bits)</th>
<th colspan="2" bgcolor="#FFFFEE" nowrap> Number of key characters</th>
</tr>
<tr>
<th bgcolor="#FFFFEE">ASCII</th>
<th bgcolor="#FFFFEE">Hex</th>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> WEP64 (40)</td>
<td align="center" bgcolor="#FFFFEE">5</td>
<td align="center" bgcolor="#FFFFEE">10</td>
</tr>
<tr>
<td bgcolor="#FFFFEE" nowrap> WEP128 (104)</td>
<td align="center" bgcolor="#FFFFEE">13</td>
<td align="center" bgcolor="#FFFFEE">26</td>
</tr>
</table>
</td>
</tr>
</table>

=== WPA ===
* See [[Wikipedia:Wi-Fi Protected Access]] (WPA)
{{Tip|tiptext=WPA can be cracked if a weak passphrase is used!<br>See [[#What Makes for a Strong Password or Passphrase?|What Makes for a Strong Password or Passphrase?]]}}

=== Universal Plug and Play ===
Turn off [[wikipedia:Universal Plug and Play|Universal Plug and Play]] (UPnP) in your wireless router. Because most consumer-grade wireless routers lack UPnP [[wikipedia:Authentication|authentication]] they are vulnerable to attack. (''See [[wikipedia:Universal Plug and Play#Lack of Authentication|Problems with UPnP, Lack of Authentication]]'')

=== SSL/TLS ===
* [[Wikipedia:Transport Layer Security|Wikipedia:SSL/TLS]] (Secure Sockets Layer/Transport Layer Security)
* See:
** [[Wi-Fi How To#Use SSL/TLS for email access|Wi-Fi How To Use SSL/TLS for email access]]
** [[Wi-Fi How To#Use SSL/TLS for sensitive Web pages|Wi-Fi How To Use SSL/TLS for sensitive Web pages]]

=== Software Firewall ===
* A good software "[[wikipedia:Firewall (networking)|firewall]]" will protect your computer from network attacks, particularly on [[wikipedia:Encryption|unencrypted]] Wi-Fi networks (''e.g., ''public [[wikipedia:Hotspot (Wi-Fi)|hotspots]]).
* If running Microsoft Windows XP:
*# Update with SP2 (Service Pack 2), and install ''all'' security updates.
*# Make sure the Windows Firewall is enabled for the wireless connection.
* Good free software firewalls
** [http://www.personalfirewall.comodo.com/ Comodo Personal Firewall]
** [http://www.sunbelt-software.com/kerio.cfm Sunbelt Kerio Personal Firewall] (full download reverts to free basic version after 30 days)
** [http://www.zonelabs.com/store/content/catalog/products/sku_list_za.jsp?dc=12bms&ctry=US&lang=en&lid=nav_za ZoneAlarm]

=== VPN ===
VPN ([[wikipedia:Virtual private network|Virtual Private Networking]]) is used to construct and connect private networks using the public [[wikipedia:Internet|Internet]]. Communications are secured by means of some type of [[wikipedia:Encryption|encryption]], depending on the specific type of VPN. In general, there are two kinds of VPN:
* ''Remote-access'', in which both payload and data are encrypted.
* ''Site-to-site'', in which only data are encrypted.

==== VPN Resources ====
* '''[http://www.vpnlabs.com/ VPN Labs]''' (open community for researching, reviewing, and discussing VPN)

==== VPN Service Providers ====
* '''[http://www.anchorfree.com/hotspot-shield/ AnchorFree Hotspot Shield]''' (ad banners)
* [http://www.hotspotvpn.com/ HotSpotVPN] (commercial)
* [http://www.iopus.com/iPig/ iPIG] (10 MB free, commercial thereafter)
* '''[http://www.jiwire.com/hotspot-helper.htm JiWire Hotspot Helper]''' (commercial)
* [http://publicvpn.com/ PublicVPN.com] (commercial)
* [http://vpnprivacy.com VPN Privacy] anonymous PPTP (commercial)
* [http://www.witopia.net/ WiTopia] (commercial)

=== What Makes for a Strong Password or Passphrase? ===

*See ''[[Wikipedia:Password strength]]''
*See also:
** [[wikipedia:Password|Password]]
** [[wikipedia:Passphrase|Passphrase]]
** [http://world.std.com/~reinhold/diceware.html Diceware Passphrase Home Page]
** [http://passwordsafe.sourceforge.net/ Password Safe] (generates and stores passwords securely)

=== Wireless Isolation ===

* If you want to open up wireless to outsiders (even just a neighbor), look for a wirelesss router with an '''isolation''' feature that blocks wireless-to-wired networking, most often found in [[#Hotspot Routers|"hotspot" routers]].
* If you also have wireless devices, then look for a wireless router or access point with a '''wireless isolation''' feature that blocks peer-to-peer wireless networking (''e.g.,'' [http://www.netgear.com/products/details/WG302.php NETGEAR WG302]).

=== Guest Account ===

A good alternative to [[#Wireless Isolation|Wireless Isolation]] is a '''Guest Account''' feature that not only isolates wireless guests from your own wireless (and wired) networking, but also can provide security ([[wikipedia:Wi-Fi Protected Access|WPA]]) for your guests. Products with such capability include:
* [http://catalog.belkin.com/IWCatProductPage.process?Product_Id=377018 Belkin N1 Vision wireless router F5D8232-4]<br>(different SSID for Private and Guests)
* [http://www.myessentialssupport.com/product/?pid=ME1004-R My Essential G Router ME-1004R] (Belkin)<br>(same SSID for Private and Guests, different WPA passphrases)

=== What is Wardriving? ===

* See [[wikibooks:Wifi:Wardriving|Wifi:Wardriving]]

== Wi-Fi Hotspots ==

* See ''[[Wi-Fi How To#Setup a hotspot|How to Setup a hotspot]]''

=== Free Public HotSpot Directories ===
* '''USA (and other countries)'''
** [http://www.anchorfree.com/ AnchorFree]
** [http://www.jiwire.com/ JiWire]
** [http://metrofreefi.com/ MetroFreeFi]
** [http://wififreespot.com/ Wi-Fi-FreeSpot Directory]
** [http://www.wifinder.com/ WiFinder]
* '''Australia'''
** [http://www.wifisearch.com.au/ Australian HotSpots]

=== Commercial Hotspots ===

* '''Directories'''
** [http://airportwifiguide.com/ AirportWiFiGuide.com] (U.S. Airports)
** [http://www.jiwire.com/ JiWire]
** [http://www.wifinder.com/ WiFinder]
* '''Networks'''
** [http://www.airpath.com/ Airpath]
** [http://www.sbc.com/gen/general?pid=1080&cdvn=localize&prod-snip=freedomlink_bus at&t (SBC) FreedomLink]
** [http://www.boingo.com/ Boingo]
** [http://www.stsn.com/ iBAHN]
** [http://www.icoacorp.com/ ICOA]
** [http://www.ipass.com/ iPass]
** [http://www.nnu.com/ NetNearU]
** [http://www.sprint.com/business/products/products/sprintPCSWI-FIAccess.jsp Sprint]
** [http://hotspot.t-mobile.com/ T-Mobile]
** [http://www.wayport.com/ Wayport]
** [http://www.weroam.com/ WeRoam]

== Special Wi-Fi Applications ==

=== Marine ===

See ''[[Wi-Fi on a Boat]]''

=== Mesh networks ===

Mesh is a wireless co-operative communication infrastructure between multiple individual wireless transceivers (''i.e., ''a wireless mesh) that have [[wikipedia:Internet Protocol|IP]] networking capabilities.

More information:

* [[wikipedia:Wireless mesh network|Wireless mesh network]] (Wikipedia)
* [[w:c:newmedia:Mesh Networks|Mesh Networks]] (new media Wikia)
* [http://www.locustworld.com/ LocustWorld]
* [http://pdos.csail.mit.edu/roofnet/doku.php RoofNet]
** [http://meraki.net/ Meraki Networks]
* [http://www.americasnetwork.com/americasnetwork/data/articlebrief/americasnetwork/412002/34898/article.pdf Rooftop Networks] (Nokia)

=== Streaming Audio to Home Stereo ===

* '''Media Adapter with computer as server:'''
** Wired Media Adapter with a Wi-Fi-Ethernet bridge/gaming adapter (''e.g.,'' [http://www.hauppauge.com/html/mediamvp_datasheet.htm Hauppauge MediaMVP] with [http://www.linksys.com/ Linksys WRT54G] as client bridge)
** Wireless Media Adapter (''e.g.,'' [http://www.apple.com/airportexpress/ Apple Airport Express] driven by [http://www.apple.com/itunes/ Apple iTunes software])
* '''Standalone Internet radio connecting to Wi-Fi network:'''
** Wired Internet radio with a Wi-Fi-Ethernet bridge/gaming adapter (''e.g.,'' [http://www.slimdevices.com/ Slim Devices Squeezebox] with [http://www.linksys.com/ Linksys WRT54G] as client bridge)
** Wireless Internet radio

== Troubleshooting Wi-Fi ==

=== Interference ===

* '''Checklist of possible interference sources:'''
:{|
| [[Image:CheckBox.gif]] || [[wikipedia:Microwave oven|Microwave oven]]
|-
| [[Image:CheckBox.gif]] || 2.4 Ghz video or [[wikipedia:Security camera|security camera]] link ([[wikipedia:X10 (industry standard)|X10]]).
|-
| [[Image:CheckBox.gif]] || Municipal [[wikipedia:Wireless|wireless]] [[wikipedia:Telecommunications network|network]].
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Bluetooth|Bluetooth]] devices ([[wikipedia:Mouse (computing)|mouse]], [[wikipedia:Telephone|phone]], [[wikipedia:Personal digital assistant|PDA]], [[wikipedia:Headphones|headset]], [[wikipedia:Cell phone|cell phone]], ''etc.'')
|-
| [[Image:CheckBox.gif]] || Portable [[wikipedia:Wireless|wireless]] [[wikipedia:TV camera|TV camera]] used at sports events.
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Frequency-hopping|Spread spectrum Frequency hopping]] [[wikipedia:Cordless telephone|cordless phones]] (''e.g.,'' [[wikipedia:Panasonic|Panasonic]] Gigarange)<br><small>Note: 2.4 GHz phones are not an issue in the UK(Eur), as [[wikipedia:Digital Enhanced Cordless Telecommunications|DECT]] phones operate from 1.88 GHz to 1.9 GHz.</small>
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Wi-Fi|Wi-Fi]] (IEEE 802.11b/g) wireless [[wikipedia:Computer keyboard|keyboard]], [[wikipedia:Personal digital assistant|PDA]], and/or [[wikipedia:Cell phone|cell phone]].
|-
| [[Image:CheckBox.gif]] || 2.4 GHz [[wikipedia:Wireless|wireless]] [[wikipedia:Gamepad|gamepad]] and/or controller.
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Electrodeless lamp|RF Excited Lighting]] (''e.g.,'' Fusion Lighting).<br>''See [http://www.bwianews.com/2001_11_01_archive.html Part 18 RF Lighting, A Potential "Extinction Level Event" For Communications Users Of The 2.4 GHz Band]''
|-
| [[Image:CheckBox.gif]] || 2.4 GHz [[wikipedia:Wireless|wireless]] [[wikipedia:Baby monitor|baby monitor]].
|-
| [[Image:CheckBox.gif]] || 2.4 GHz [[wikipedia:Amateur radio|ham radio]] operation.
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Wisp|WISP]] (Wireless Internet Service Providers) which may be using non-[[wikipedia:Wi-Fi|Wi-Fi]] type of [[wikipedia:Modulation|modulation]] (''e.g.,'' [[wikipedia:WiMax|WiMAX]]).
|-
| [[Image:CheckBox.gif]] || Breezecom/Alvarion/Symbol/Raylink [[wikipedia:Frequency-hopping|spread spectrum frequency hopping]] [[wikipedia:Telecommunications network|networks]].
|-
| [[Image:CheckBox.gif]] || Western Multiplex or Proxim non-[[wikipedia:Wi-Fi|Wi-Fi]] [[wikipedia:Wireless|wireless]] links (''e.g.,'' [[wikipedia:Lynx (protocol)|Lynx]]).
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Homerf|HomeRF]] [[wikipedia:Frequency-hopping|spread spectrum frequency hopping]] [[wikipedia:Telecommunications network|network]].
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Zigbee|ZigBee]] [[wikipedia:IEEE 802.15|IEEE 802.15.4]] [[wikipedia:Sensor|sensor]] [[wikipedia:Wireless|wireless]] [[wikipedia:Telecommunications network|network]].
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Microwave|Microwave]] [[wikipedia:Drying (food)|fruit drying]] oven, plastic mold preheater.
|-
| [[Image:CheckBox.gif]] || [[wikipedia:Instability|Unstable]] high power [[wikipedia:Wi-Fi|Wi-Fi]] [[wikipedia:Power amplifier|power amplifier]] spewing [[wikipedia:Radio frequency|RF]] "garbage".
|}
* '''Resources on interference'''
** [http://www.wi-fiplanet.com/tutorials/article.php/953511 Minimizing 802.11 Interference Issues]
** [http://www.networkworld.com/columnists/2004/0816wizards.html Stop the interference!]

* '''Checking for Wi-Fi networks'''
** [http://www.stumbler.net/ Network Stumbler]
** [http://www.kismetwireless.net/ Kismet]
** [http://www.kasuei.com/hitchhiker/ Hitchhiker]

* '''Non-interfering Wi-Fi channels'''<br>Closely spaced Wi-Fi channels overlap, and signals on two different channels can interfere with each other, especially when they are less than 5 channels apart, with the amount of interference decreasing with increasing channel separation. (Thus channels 1 and 3 interfere less with each other than channels 1 and 2.) ''For minimum interference between different Wi-Fi networks, '''first try channels 1, 6, and 11''', which have minimal overlap.''

=== Poor Signal ===

* See [[#Antennas|Antennas]].

=== SSID Conflict ===

:When two networks have the same [[wikipedia:SSID|SSID]], wireless devices on one network may try to connect to the other network (because they look like the same network), which can cause problems. This can easily happen when two different networks use hardware from the same vendor with the same default SSID. ''To avoid such problems, '''configure a unique SSID''' for your network that won't conflict with other networks, now or in the future.''

=== MAC Address Cloning ===
{{Stub}}

[[Category:Wi-Fi]]