Thursday, February 7, 2013

Wi-Fi May Get A Capacity Boost, Thanks to the FCC

Have you heard the news? Wi-Fi stands to be the glorious recipient of much more capacity. However, this is not set in stone; far from it. It depends on spectrum policy decisions the FCC is weighing right now, with the help of Congress and the NTIA (a federal agency that advises the President on telecommunications and information policy issues) .

If Wi-Fi is the lucky recipient of more unlicensed spectrum, what would it look like?

Proposed New 5 GHz Wi-Fi Channels
What does this mean for Wi-Fi networks?
  1. More channels, and MUCH more capacity! When we exclude channels 120, 124, and 128 which can't be used due to TDWR restrictions, we get:
    • 20 MHz - 12 additional channels, 54% more than we have today (22 channels) = 34 total channels!
    • 40 MHz - 6 additional channels, 60% more than we have today (10 channels) = 16 total channels!
    • 80 MHz - 3 additional channels, 60% more than we have today (5 channels) = 8 total channels!
    • 160 MHz - 2 additional channels, 200% more than we have today (1 channel) = 3 total channels!
  2. Realistic use of 80 MHz and 160 MHz channel width in multi-AP enterprise environments. As I previously stated, the sparse amount of channels available at 80 MHz and 160 MHz channel widths make them impractical for use in enterprise environments due to inadequate channel spacing and co-channel interference. With this additional spectral capacity, sufficient channels will be available to allow the use of 80 MHz channels in most environments, and 160 MHz channel use in many office environments. The only likely holdout where these larger channel widths would not be appropriate are in very high density deployments. (Further reading: The Impact of 802.11ac Gigabit Wi-Fi on Enterprise WLANs).
Here's a breakdown of how this U.S. spectrum policy initiative got started and what remains to be done (Further reading: The Need for a Balanced U.S. Spectrum Policy):
  • Feb 2012 - Congress passed the Middle Class Tax Relief Act of 2012, which includes stipulations to investigate the use of 195 MHz of additional 5 GHz spectrum for unlicensed use, among other frequency bands.
  • Jul 2012 - The President's Council of Advisors on Science and Technology (PCAST) released a report supporting immediate methods to begin realizing the full potential of federal held spectrum to spur economic growth, largely through spectrum sharing techniques.
  • Jan 2013 - FCC Chairman Genachowski announced the effort to open more spectrum for unlicensed use at CES. (Further reading: Spectrum: The Gift that Gives You Faster 802.11ac).
  • Jan 2013 - NTIA released their initial study on spectrum sharing in these 5 GHz bands with existing primary users, mostly federal radar systems, and the risk of interference. (Further reading: NTIA weighs in on FCC's 195 MHz spectrum announcement).
  • Feb 2013 - The FCC Notice of Proposed Rulemaking (NPRM) is due on 20-Feb and will outline the proposed spectrum policy. It will detail what bands are allowed for unlicensed use and what spectrum sharing and interference mitigation techniques are required to protect existing primary users. This NPRM will be crucial to understanding how much capacity Wi-Fi will gain, whether or not existing equipment will be compatible with a firmware upgrade, if new hardware is required, and the technical requirements that will dictate the feasible timeline for implementation and use.
Update - The FCC released the 5 GHz NPRM as expected on Feb 20th. Matthew Gast over at Aerohive Networks provided a good analysis of the NPRM. It looks like further in-depth study on the spectrum sharing and interference mitigation techniques will take until late 2014, and we could possibly get approval to use the new spectrum by early 2015.

It's worth noting that the European Commission is considering a similar course of promoting unlicensed spectrum policy [Full PDF, EESC Opinion Feb 2013].

This rulemaking is no small matter. The FCC spectrum policy defined over the course of 2013 will influence Wi-Fi network design and performance for the next decade (or more)! Just take a look at how the initial FCC rulemaking allowing unlicensed spectrum use in 1985 has influenced wireless networks to date, over a quarter-century later.

Here's to hoping 2013 brings a new infusion of unlicensed spectrum for the masses!



  1. Nice article..and a very well written blog...

  2. very informative, keep it up!