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Wireless Signal Tweaking

Discussion in 'Articles' started by Toxic, Oct 20, 2005.

  1. Toxic

    Toxic Administrator Staff Member

    Everyone will at sometime experience Wireless problems. This can be put down to a number of things, and most users blame the router. Problem is the router is one of many parts to the equation.

    Interference is the main problem with Wireless signals.

    Channel selection is very important. The wrong channel selection on your wireless router can cause hours of pain and stuffing. Interference around your home will affect your Wi-Fi network. Selecting the correct channel can save you hours of grief by removing the interference that is associated with certain wifi chanels.

    I have placed below some data I required from a 2 day Wireless Networking course I was on last March 2006. This Info will give you a breakdown of the channels and why selection is important.

    The table below lists the ETSI specified frequencies and corresponding channel for European operation of Direct Sequence Spread Spectrum:

    Channel No.European Frequencies
    1 - 2401 - 2423 MHz
    2 - 2406 - 2428 MHz
    3 - 2411 - 2433 MHz
    4 - 2416 - 2438 MHz
    5 - 2421 - 2443 MHz
    6 - 2426 - 2448 MHz
    7 - 2431 - 2453 MHz
    8 - 2436 - 2458 MHz
    9 - 2441 - 2463 MHz
    10 - 2446 - 2468 MHz
    11 - 2451 - 2473 MHz
    12 - 2456 - 2478 MHz
    13 - 2461 - 2483 MHz

    Each Channel is 22 MHz wide and uses a 1 MHz carrier frequency. As you can see from the table, the channels are spaced at 5 MHz intervals.
    e.g. Channel 1 operates from 2401-2.423 GHz

    Out of the 13 Channels available in most European countries under the ETSI standard in the 2.4 GHz ISM band (which covers 802.11b and 802.11g) only 3 channels are unique. 1, 7, 13 (preferred) do not cross over at all against each others frequencies, and for this reason we tend to use these most as the preferred channels for transmissions.

    Channels 2, 3, 4, 5, 6, 8, 9, 10, 11, 12 all overlap into other channels beside themselves, and this can cause interference to any other transmission signal.

    Note: 1, 6, 11 are also unique since US channels are limited to 1-11, however for ETSI and this guide we will use 1, 7, 13 as they are the furthest apart as well.
    When setting up your wireless network you should take into consideration other Wireless Cells active in your area, and change SSID and Channels to accommodate you and your neighbours.

    Security of your Wireless Cell is another story which is articled here:

    Wireless Security - How secure is your Wireless Network?

    Further more there are also a few things to tweak your wireless router to get the best out of the signal without loosing connection.

    First of all try updating to the latest firmware. Linksys may have tweaked or fixed a problem with the wireless signal and therefore a new firmware may help. Your Wireless client devices may also have new firmware/drivers that fix issues.

    Position the Router in the highest place possible. dont put it in the basement this will affect wireless signal strength.

    If your wireless devices are all 54G then if possible set your router to G only. if not set Wireless to B only (unless you have B and G devices) though B mode will give better signal than G

    Adjusting the "RTS Threshold" can help alleviate Packet loss. If one of the Wireless computers can obtain an IP address but can not ping, then set the "RTS Threshold" to something lower. (no lower than 2304 though)

    Adjusting the "Beacon Interval" can help association problems. If there is a wireless adapter that is able to see the access point, but is unable to get locked, try adjusting the "Beacon Interval" to 50

    Adjusting the "Fragmentation Threshold" can help association problems. If there is a wireless adapter that is able to see the access point, but is unable to get locked, try adjusting the "Fragmentation Threshold" to something lower. (no lower than 2304 though)

    Speed issues are abundant. If you have just one or two clients, enabling frameburst will help. Make sure CTS is disabled.

    Try WEP security instead of WPA as signal strength seems to be reduced in WPA. however WEP is less secure. WPA2 being the prefered security option.

    If your PCI wireless adapter is still having problems this may be down to a IRQ conflict. Try moving your PCI network card to a different slot on your Motherboard. Also changing Drivers may help.

    Adding a Directional Antenna to your wireless PC's will help in reception. The DLink DWL-M60AT is a very good example of a Directional antenna that can be added to most Wireless PCI Network cards with easy and gives better results than boosting a signal via a firmware upgrade.

    WRT54G/GS and WAP54G ONLY

    There are a number of 3rd party firmwares that have been developed which will allow you to adjust the signal strength output of the routers. check the downloads for such firmware upgrades. , HyperWRT, Tomato, DD-WRT, HyperWAP, EWRT, MustDie WAP, Sveasoft, OpenWRT, and, WifiBox projects all have various firmwares for the signal strength tweak. make sure your router model and version number will work with the router in question.

    The default for most linksys Routers is 18mW. you can increase this drastically with a 3rd party firmware with upto a max of 251mW (outside use only please)

    Putting the transmission rate beyond 100mW is illegal in ETSI/FCC standards. 251mW is obtainable from the WRT54G chipset but this could affect your health. Do not do this unless it is outside and you are broadcasting long distances. Also Heat can be an issue of the radio chipset when putting the power up to 251mW, and the signal gets "dirty" and channels either side of the one you have select can be affected.

    One other thing:

    The signal strength maybe adequate but the reception is the problem. you can sometimes gain better signal strength by adding a reflector than adding any bigger antennas.

    For more information about making a reflector checkout this website.

    Free Antennas

    Here are is a short list on common causes of interference:

    WINDOW IN BRICK WALL = 2dB

    METAL FRAME, GLASS WALL INTO BUILDING = 6dB

    OFFICE WALL = 6dB

    METAL DOOR IN OFFICE WALL = 6dB

    CINDER WALL = 4dB

    METAL DOOR IN BRICK WALL = 12.4dB

    BRICK WALL NEXT TO METAL DOOR = 3dB

    Linksys suggests that you place your Access Point as high as possible. If your network goes through multiple floors, try to place the Access Point on the upper floor. If you want to connect while you're outside, place the AP near a window. Keep it away from large metal objects such as filing cabinets. Also, try to keep the AP's away from operating microwave ovens and 2.4GHz cordless phones. In addition, if you use 2.4 GHz phones and experience interference, try using a different channel on the phone.

    I hope this helps some of you.
     

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