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Wireless Networking and the 5 GHz RF Range.

with 8 comments

As I speak with other IT professionals concerning wireless networking, one thing that seems to shock people is when I start talking about the 5 GHz RF range. Usually the first thing they say is along the lines of “You are still using that?”, most people still see the 5 GHz range associated with the 802.11a standard and nothing more, while it’s true potential is finally coming to light (and people are now seeing the limitations of the 2.4 GHz frequency).

Since this topic can get in depth, and I prefer to keep my posts to a decent length, and to the point, we will jump into the advantages of utilizing the 5 GHz range:

  1. Less congestion, anyone who has been administrating or implemented a wireless knows how many other devices are using the 2.4 GHz range everything from BlueTooth devices (which is found in almost every phone), microwaves (found in office lunch/break rooms), to cordless phones. More particularly microwaves and cordless phones they will congest the 2.4 GHz spectrum without regard for any other device using the RF band. The 5 GHz does not suffer from as much interference as the 2.4 GHz  range does, of course proper survey’s should be done prior to rolling out a Wi-Fi network just to be sure.
  2. More non-overlapping channel, the 5 GHz range consists of 3 bands. These bands provide us with 21 non-overlapping channels this gives us the ability to more densely pack an area with 802.11a/n access points. Decreasing the amount of clients per AP (With proper load balancing) providing increased throughput, and making roaming a seamless process. Where as the 2.4 GHz range only gives us 3 non-overlapping channels (1, 6, 11). Detailed information on each UNII band can be found below.
  3. Channel Bonding. While you can perform channel bonding in the 2.4 GHz it is better suited for the 5 GHz range. Channel bonding is how you achieve speeds up to 600 Mbps in 802.11n it does this by making the channels 40 MHz wide compared to 20 MHz wide. Channel bonding at the 5 GHz range still leaves you with 12 non-overlapping channel, while channel bonding in the 2.4 GHz range gives you 1 (possibly 2) channel.
  4. Future use. The next wireless standard after 802.11n, is most likely going to be 802.11ac which is promising us Wi-Fi speeds in the Gbps’s it plans to accomplish this by using 40, 80, or 160 MHz wide channels this is going to rule out the 2.4 GHz range completely. (Unless it’s changed.)
  • UNII-1/Lower Band (5.150 to 5.250 GHz) Non-overlapping channels 36, 40, 44, 48
  • UNII-2/Middle Band (5.250 to 5.350 GHz) Non-overlapping channels 52, 56, 60, 64
  • UNII-2 Extended (5.470 to 5.725 GHz) Non-overlapping channels 100, 104, 108, 112, 120, 124, 128, 136, 140
  • UNII-3/Upper Band (5.725 to 5.825 GHz) on-overlapping channels 149, 153, 157, 161, 165

Written by Stephen J. Occhiogrosso

November 22, 2010 at 3:33 PM

8 Responses

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  1. Hi,

    Good information. As for the 12 non overlapping channels with 40 MHz, are all the 12 channels available for use in USA ? Also, how about the Dynamic Frequency Allocation (DFS) ? I have read in other websites that it is better to use the channels which are without DFS capability. Is that true ? In reality are all 12 non overlapping channels used while using 802.11n ?

    Sudarshan Prasad

    July 24, 2011 at 10:50 PM

  2. DFS/TPC will only effect the UNII2 and UNII-2 extended bands. This is an FCC restriction for those in the US and Canada. This information is also part of 802.11h standard.

    This is only unforced because they UNII2 and UNII2e bands were intended for both indoor and outdoor deployments while the UNII1 bands were only intended for indoor deployments. Since the UNII2 and UNII2e bands are intended for outdoor deployments they enforced the TPC and DFS restrictions so the WLAN’s do not interfere with radar.

    Each UNII band also has different transmit power requirements that should also be taken into consideration, while their are 12 available 5 GHz channels (that can be 40 MHz wide) in reality it’s up to the network engineer to decide if it’s feasible to use them all and what kind of channel re-use policy should be implemented. Typically during a site survey.

    Hope this helps.


    July 25, 2011 at 1:07 PM

  3. […] Wireless Networking and the 5 GHz RF Range with 469 views […]

    • I want to know Channel bonding in brief. Can anybody suggest me and how can we test it. Even I read channel bonding is supported only in 5GHz. Is it true?


      November 2, 2011 at 4:18 AM

      • The only.true way to see channel bonding is by using a spectrum analyzer. This will show you the RF lobes and which frequencies it is using when you bond channels they will be 40 MHz wide compared to 20 MHz so the RF lobe will be twice as wide. Wi-Spy offers some spectrum analyzers.


        November 2, 2011 at 7:07 AM

  4. Note that the FCC took away the 5600-5650 MHz band in 2010, when they laid out DFS. So there are not 23 but 21 channels now. (you forgot 165 in your list)

    Joel Snyder

    June 24, 2012 at 2:48 PM

  5. […] Wireless Networking & the 5 GHz RF Range with 2,262 views. […]

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