Long-Distance WiFi
Increasing Range



Power increase

Another way of adding range uses a power amplifier. Commonlyknownas "range extender amplifiers" these small devices add usually around ½watt of power to the antenna. these amplifiers have been tested to givemore than 5x the range to an existing network. In the case of thepopular Linksys WRT54G The RadioLabs 2.4 GHZ range extender amplifierincreases the stock power of the WRT54G from +18dBm (63 mW) to +27dBm(500 mW), a 9dB (8x) increase.[2] These power amplifiersoffer a cheap, minimal setup that can easily be added to existingnetworks in places where law allows.



Broadband &Wireless Communication Resource

High-gain antennas andprotocol hacking

Specially-shaped antennas can be used to increase the range ofa

Wi-Fi transmission without a drastic increase of transmission power.Parabolic high-gain antennas allow transmitting a narrow beam overdistances of several kilometers. Alternatively, a low-cost approach canbe used to increase the range of a Wi-Fi transmission using very simpleenhanced antennas while keeping standard hardware (see "www.usbwifi.orcon.net.nz/").

The standard 802.11protocol stacks can also be modified to make them more suitable forlong distance, point-to-point usage, at the risk of breakinginteroperability with other Wi-Fi devices and suffering interferencefrom transmitters located near the antenna. These approaches are usedby the TIER project (see "Rethinking Wireless in the Developing World").




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Obstacles tolong-range Wi-Fi

Methods that stretch the range of a Wi-Fi connection may alsomake it fragile and volatile, due to mundane problems including:

 Phones

Many cordless phones in the US and Canada use the 2.4GHzfrequency,the same frequency at which Wi-Fi standards b, g and n operate. Thiscan cause a significant decrease in speed, or sometimes the totalblocking of the Wi-Fi signal when a conversation on the phone takesplace. There are several ways to avoid this though, some simple, andsome more complicated.

  • Buy/Use wired phones.
  • Buy 5.8GHz or 900MHz phones, commonly available today.
  • Use VoIP/WiFi phones; these share the WiFi base stationsand participate in the WiFi contention protocols.
  • Test several different Wi-Fi channels to avoid the phonechannels.

The last will sometimes not be successful, as numerouscordless phones use a feature called Digital Spread Spectrum.This technology was designed to ward off eavesdroppers, but the phonewill change channels at random, leaving no Wi-Fi channel safe fromphone interference.

 Car alarms

Certain car manufacturers use the 2.4GHz frequency for their caralarminternal movement sensors. These devices broadcast on 2.45GHz (betweenchannels 8 and 9) at a strength of 500mW. Because of channel overlap,this will cause problems for channels 6 and 11 which are commonly useddefault channels for Wi-Fi connections. Because the signal istransmitted as a continuous tone, it causes particular problems forWi-Fi traffic. This can be clearly seen with spectrum analysers.

Landscape interference

Obstacles are among the biggest problems when setting up along-range Wi-Fi. Trees and forests degrade the microwavesignal, and rolling hills make it difficult to establish Line-of-sight propagation.

In a city, buildings will impact integrity, speed andconnectivity.Steel frames partly reflect radio signals, and concrete or plasterwalls absorb microwave signals significantly, but sheet metal in wallsor roofs may efficiently reflect Wi-Fi signals,causing an almost total loss of signal.

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