Mobile Sands

January 31, 2009

White space spectrum unlikely to enable new ISPs

Filed under: 3G, white space — AJ @ 9:29 pm

FCC’s 11/14/08 announcement to open up TV-band white spaces has been hailed as a great step forward for wireless inovation, and countries around the world seem eager to follow in FCC’s footsteps . There is lot of excitement about this spectrum because it has excellent propogation characterstics.  In my opinion, even though this spectrum may enable some new consumer electronics applications,  this spectrum is unlikely to create any new service providers.

Some background… White spaces exist because TV broadcasters have to do frequency planning. A channel that is used in Los Angeles cannot be used in Orange County or San Bernandino and vice versa. After the DTV transition is over, LA will be using 11 channels (7, 9, 1, 13, 28, 31, 34, 36, 41, 42, 43) in the VHF and UHF band, leaving 40 channels unutilized.

After years of investigation, FCC decided to allow unlicensed devices to operate in this spectrum subject to certain conditions.  Here is a quick summary of FCC’s Notice of Proposed Rule Making (NPRM) on this topic. 

  • Unlicensed TVBDs are expected to protect all services that operate in TV bands today. This includes broadcast TV, wireless microphones, medical telemetry, radio astronomy and land-mobile radio systems
  • Unlicensed TVBDs are not allowed to operate in any channel being used for Broadcast TV (i.e. generate no co-channel interference)
  • Based on rules for adjacent channel operation, maximum transmit power and spectrum sensing, unlicensed TVBDs can be of two kinds: Fixed and Personal/Portable.
  • Fixed devices
    • Use channels 2-51, with the exception of channels 3, 4 and 37
    • Maximum transmit power (EIRP) of 4 W with directional antennas
    • No adjacent channel operation with TV
    • Support spectrum sensing, and detect signals as low as -114 dBm
    • Determines its location; accesses a database of existing services
  • Personal/Portable devices
    • Use channels 21-51, with the exception of channel 27
    • Maximum transmit power of 100 mW. No directional antennas allowed
    • Maximum transmit power limited to 40 mW in channels adjacent to TV
    • Spectrum sensing, location determination, and access to database of existing services required, unless device is operating under control of a fixed device

Notice that the FCC does not allow fixed devices to operate in adjacent channels and requires portable devices to reduce their peak power. This restriction reduces the amount of “white space” spectrum available to a new ISP considerably. Going back to the LA example, once we removes channels 2, 3, 4, 37 and all adjacent channels from the list of available channels, a “white space” ISP has only16 channels, not 40. Though sixtenn channels provide 96 MHz, an ISP must be prepared to share it with other users like wireless microphones and personal/portable TVBDs.

More white space spectrum is available outside major metro areas but these areas also have abundant and inexpensive PCS, Cellular and AWS spectrum. Despite its better propogation characterstics, Unlicensed TV band spectrum does not cover much more than licensed PCS or AWS spectrum because the transmit power of unlicensed TVBDs is limited. As a result, an operator/ISP that deploys a proven 3G/4G technology in licensed bands is guaranteed to do better than on ISP that uses yet-to-be developed “white space” technology.

Any ISP using it in a large metropolitan area will also have to contend with three to four established competitors (cable, DSL, WiMAX and LTE). Technology required to build a commercial white space system is barely on the drawing board. The IEEE standard (802.22) that is being developed for white spaces is far from completion and in its current state does not meet FCC rules.  Even if lots of vendors get behind this standard, it will be at least four years before commercial base stations and devices can be available at reasonable price points. By that time, it is debatable how much unmet demand will exist, in the US or outside.

I think things can be more interesting for personal/portable devices, but that is the topic of another blog entry.




  1. […] one my previous posts, I had argued that the amount of white space spectrum available (as currently defined in FCC’s NPRM) is just not sufficient for… in urban areas.  But I was still optimistic about the use of white space spectrum for consumer […]

    Pingback by White Space Spectrum Gone Missing? Just 1 Vacant Channel in LA, NY and SF « MobileSand - Amit Jain’s Blog — February 25, 2009 @ 3:51 pm

  2. […] made the spectrum useless for both – providing broadband access or local area networking (see posts from last year). Though I am skeptical of the FCC’s “Super Wi-Fi” claims, I do think the revised rules make […]

    Pingback by White Space Spectrum Becomes Available With Simplified Rules | Mobile Sands — September 27, 2010 @ 12:34 am

  3. Good post. I learn something totally new and challenging on sites I stumbleupon on a daily basis.
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    Comment by Facebook — February 2, 2013 @ 3:09 pm

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