• By (Deleted User)

    Network World's Wireless in the Enterprise Newsletter, 02/15/06
    U.S. now allows full-5GHz Wi-Fi networking
    By Joanie Wexler
    Last month, the FCC officially opened up the use of the middle band of the Unlicensed National Information Infrastructure (UNII) spectrum (5.470 GHz to 5.725 GHz) to 54Mbps 802.11a Wi-Fi networks in the United States. The band adds another 255 MHz and 11 channels to the existing 325 MHz and 13 channels available for Wi-Fi in this band.

    As of January 20, any products that apply for certification in the 5.470 GHz to 5.725 GHz band or in the lower end of the UNII band at 5.25 GHz to 5.35 GHz, were required to support dynamic frequency selection (DFS) and transmit power control (TPC) to minimize interference, per a February 2005 FCC order.

    If you've already got equipment running in the lower band installed, don't worry - you're grandfathered.

    DFS and TPC are part of 802.11h, the European "flavor" of 802.11a. DFS dynamically instructs a transmitter to switch to another channel under particular conditions, such as the presence of a radar signal.

    Setting the transmit power of the access point and the client adapter can allow for different coverage area sizes and for the client to conserve battery life. For example, it helps to reduce transmit power in areas with high user density to avoid interference. It can also help with security by keeping transmit ranges confined so there is less chance of signals spilling out into the street or to neighboring offices.

    Both the 5-GHz and 2.4-GHz spectrum ranges are likely to be component of future 802.11n networks. While the 5-GHz range has its issues with inconsistent global regulation (see Monday's newsletter), the 2.4-GHz band supporting 802.11g and 802.11b faces its own hurdles. I'll discuss those next time.

  • AWESOME POST Joel. Thanks a million for passing along this info.


  • Here is some more good info on it from Joel's guys at Cisco.

  • Thanks Ben.

    Did anyone notice that last statement in the Cisco doc Ben posted? Holy cow - that's great information!


  • I didn't even notice that. That is great news. Remember, that is only the FCC's rules. Local authorities (or people who think they are in positions of authority like HOAs) may still give you a hard time.

  • I just read the FCC Order (06-12), dated Feb 16, 2006.

    This brings up major implications for site surveys. Yeeks! Suppose that ABC Company pays for a site survey, whether manual or predictive, then everything is installed according to the site survey. It all works fine, and everyone is happy.....UNTIL....the system's internal rules (which are only too happy to comply with FCC regs of course) start switching power levels and channels at will because of some nearby interference. The site survey has just gone into the toilet.

    This scenario lends itself to auto-configuring technologies, such as AutoCell. Some switch vendors have also implemented features that allow the WLAN switch to recalibrate and rearrange the channel reuse pattern and power outputs at the APs. This is basically the same thing. Static environments have suddenly been obsoleted - more or less by FCC regs.

    Another thing that comes to mind.... Meru Networks. Their technology is astonishing, but they operate each system on a single channel to achieve "zero handoff." They can have multiple overlaid systems, each acting independently on a single channel. Their whole system wouldn't suddenly say, "hey, one of my APs sees lots of noise...let me switch my whole network do a different channel." Man, I'm interested to see what they say about this one.


  • Devin,

    Can you post a link to that? Thanks in advance.


  • By (Deleted User)


    Does the FCC allow for DFS and TPC in the ISM band of 2.4 GHz? Or is this the vendor proprietary way of making WLANs operate in that band? I haven't seen this in operation much, as all the enviroments we install are static as well.

    I know it DFS and TPC was reserved for the 5 GHz UNII band due to radar interference. If the FCC allows this 5 GHz flux capacitor of the APs, all Service Level Agreements (SLAs) for the install are null and void right?

    I see your point on the site survey issue too, we will start powering the APs and client cards at 5mW instead of 50 mW. No, I think we'll set it to 1 mW? No not enough, let's go back let's go to channel 6, no channel 11, no channel 1.

    BLUF it's more commission for the sales team ? :)

  • Compughter,

    I've seen systems that have DFS and TPC functionality for both 802.11a/h and 802.11b/g. Once the functionality is put into the a/b/g/h device for one radio (802.11a), why not implement the functionality for both radios? It only makes sense really.

    The difference is that there are no FCC requirements in the 2.4 GHz ISM band that I know of... yet. :)

    You are right - this is going to be a mess for 802.11a networks.


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