Wednesday, February 20, 2013

FCC Opens More 5GHz Spectrum


In an effort to accelerate the growth and expansion of new Wi-Fi technology, the FCC proposes to increase the available unlicensed spectrum by 35%, adding 195 MHz of additional spectrum in the 5 GHz band. This rule proposal today follows through with FCC chairman Julius Genachowski’s announcement at CES earlier this year (See Post).

The Unlicensed National Information Infrastructure band three (U-NII-3) will receive an addition 25MHz of spectrum and the rules for U-NII-3 (15.407) devices are proposed to align with those of digitally modulated devices (15.247). This will provide consistent rules across 125 MHz of spectrum. The rules propose to remove the 5.725 – 5.85 GHz band from section 15.247, and amend the U-NII band rules to maintain many of the technical rules that currently make certifying to 15.247 more attractive; however some of the more restrictive requirements of 15.407 will remain.

Summary of some of the proposed 15.247/15.407 technical changes;

  • 15.247 will remove 5.725 - 5.850 GHz (devices using this band now under 15.407)
  • Frequency band, 15.407 expanded from 5.825 to 5.85 GHz
  • Power, 15.407 will fix limit at 1W as in 15.247 instead of lesser of 1W or 17 dBm + 10 log B
  • PSD, 15.407 to use Power Spectral Density of 15.247 (possible change of measurement BW to 1 MHz)
  • Emission Bandwidth, 15.407 will adopt min 6 dB bandwidth of 15.247
  • Antenna Gain, 15.407 to retain 23 dBi maximum no penalty antenna gain  for point to point
  • Unwanted Emissions limits of 15.407 will remain, more stringent than 15.247
  • Peak to Average ratio of 13dB in 15.407 will remain, no such requirement in 15.247

The new rules are seeking comment on potential security features that will be required by manufacturers and implemented in any digitally modulated device capable of operating in the U-NII bands to prevent 3rd parties from reprogramming devices to operate outside of the device’s certified parameters.

The proposal also notes potential “mitigation” techniques such as a database registration process combined with geo-location technology to determine whether there is a potential for interference to radar systems such as the TDWR.

There are several changes proposed to improve the reliability of “Dynamic Frequency Selection” DFS, namely lowering permitted Power Spectral Density (PSD) for lower powered devices using relaxed sensing threshold, modifying the Bin-1 radar waveform and removing the uniform channel loading requirement. The rules make clear that any device subject to DFS and that is capable of initiating a network, must have radar detection functionality and must be approved with that capability.

It is suggested that devices could operate in the new U-NII-2B band under the same technical framework specified in 15.407 for U-NII-2A and U-NII-2C opening operation up to the 475 MHz continuous band from 5.25 to 5.725 GHz. It is also noted that should the U-NII-3 band be increased to the proposed 5.85 GHz upper limit, then the same technical framework applicable to U-NII-3 could be applied to devices operating in the U-NII-4 band allowing operation across the continuous 200 MHz spectrum. The proposal seeks whether and how to integrate DFS into the new U-NII-2B and U-NII-4 bands.

It is noted that up to 12 months after adoption of any new or modified rules, devices could still be certified under the old rules. After 12 months, all new certifications for U-NII devices must be under the new rules. Up to 2 years after adoption of any new or modified rules, the FCC will permit Class II permissive changes to equipment certified prior to the 12 month transition date. At the end of the 2 year transition period, devices will not be permitted to be sold, manufactured, installed, imported or marketed in the United States unless they are certified under the new rules. It is explained that devices that are already installed or in use should be grandfathered for the life of the equipment.

The Notice of Proposed Rulemaking is set with a 45 day comment period, and a 75 day reply comment period. The changes proposed are far too numerous for this post to cover in toto, for the technical details, a link is provided in the reference section.


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