Understanding Wi-Fi's two spectrum bands - The Diigo Meta page

• 09 Jul 11
  

  Denise Martin

  • Apple’s new base stations now automatically choose a higher-numbered channel by default if there’s one available. If your station is choosing a lower channel in the 5GHz band, you may want to override that choice and choose a higher channel manually in order to get the signal strength you deserve.

     

    You can override this by using AirPort Utility and forcing a choice:
  • • Launch AirPort Utility, select your base station, and click on Manual Setup.
     
    • Click on the AirPort icon and then on the Wireless tab.
     
    • Select Manual from the Radio Channel Selection menu.
     
    • Note the channel displayed, such as 36 (5 GHz). If the channel number is from 36 to 48, click on the Edit button.
     
    • Select a higher-numbered channel, starting at 149.
  • (These instructions are for a simultaneous dual-band base station. For a one-band-at-a-time 802.11n base station, hold down the Option key and then click on Channel in step 3, and then select the channel from the pop-up menu that appears. Radio Mode must be set to “802.11n (802.11a compatible)” or “802.11n only (5GHz)” for 5GHz channel options to appear on those 802.11n base stations.)
  • With the channel selection set to Automatic, the base station may be avoiding a higher-numbered channel because of interference, although that should be unlikely. If you choose 149 or higher and have problems with your network, try the other three options in succession (153, 157, and 161), and if you still have trouble, switch back to automatic and see if problems go away.

  • Speed: There’s one more variable in the mix—speed, more properly measured as throughput, or the actual amount of data that can be carried over a medium whether radio waves or wire. Wi-Fi’s speed drops by increments the further you are from a base station with a client adapter in a computer or handheld, or when interference prevents signals from being cleanly received.

     

      Problem: Slow connection speeds. When checking with AirPort Utility (see Check your Wi-Fi speeds), an 802.11n device is connecting in 5 GHz at 130 Mbps or slower.

     

      Solution: Make sure wide channels are enabled. With 802.11n, a Wi-Fi base station can create a connection over a wide channel, which uses twice the frequency range as a regular channel. Apple and some other makers opted against allowing wide channels in 2.4GHz, because there’s already so much interference it might have only muddied signals further.

     

    In 5GHz, however, where interference is much lower and channels more numerous, Apple automatically enables wide channels. Check that this option has been turned on, if you’re not seeing rates up to 270 Mbps, the highest raw data rates.

     
     
    1. Launch AirPort Utility, select your base station, and click on Manual Setup.
     
    2. Click on the AirPort icon and then on the Wireless tab.
     
    3. Click on the Wireless Options button.
     
    4. Make sure that Use Wide Channels is checked.
     
    5. If not, check the box, click Done, and click Update to restart the base station.
     
     

      Problem: Low data rates. Specifically, when you look in AirPort Utility, you notice low data rates in either or both the 2.4GHz and 5GHz bands.

     

      Solution: If your base station is far away from where your clients are connecting, see if you can move it closer, or add a second base station that extends the network.

     

    Also check for interference. If removing potential sources or moving the base station away from possible sources improves speeds, that’s your problem (and your solution).
  • there are cases where you need to tweak the settings. You may want to set a channel manually, and you may want to split your 2.4GHz and 5GHz networks on a simultaneous dual-band base station into two unique networks.

  • To split the bands in two:

     
     
    1. Launch AirPort Utility, select your base station, and click on Manual Setup.
     
    2. Click on the AirPort icon and then on the Wireless tab.
     
    3. Click on the Wireless Options button.
     
    4. Check the 5GHz Network Name box, and provide a new name for the 5GHz network.
     
    5. Click on the Done button and then on the Update button. All other wireless options remain the same, including encryption.
  • There’s an alternate way to use AirPort Utility to keep 802.11a/b/g devices from connecting to your network on the 5GHz band: In the Wireless tab’s Radio Mode pop-up menu, you can reveal extra choices for what standards are supported in each spectrum band by holding down the Option key and clicking on the menu.
  • By default, full backwards compatibility is chosen: 802.11b/g/n for 2.4 GHz and 802.11a/n for 5GHz. Instead, choose “802.11n only (5 GHz) - 802.11b/g/n” to disable 802.11a in 5GHz.

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• 20 May 09
  

  Graham Lawrence

  macworld wifi two bands time capsule

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