Ofcom Proposes TV White Space Coexistence
Says interference margins could be reduced based on experience
September 12, 2013
United Kingdom telecom regulator Ofcom has issued a consultation titled TV white spaces: approach to coexistence
that describes how it plans to prevent interference to existing services in the 470 to 790 MHz UHF TV band.
Ofcom explained: “Our overall approach to ensuring a low probability of harmful interference to other services in and adjacent to the UHF TV band is to err on the side of caution at this early stage, setting parameters that we believe we may be able to relax in the future in the light of more experience. Later this year, we will test our proposals to the extent practicable in a pilot program comprising a number of trials around the UK by a range of service providers. As part of the pilot we will allow increased power levels to be used for limited time periods to assist with this testing. We will refine our coexistence proposals in light of evidence both from the pilot and from stakeholders with a view to finalizing them in the summer of next year ahead of the launch of a full, nationwide solution in the third quarter of 2014.”
Ofcom proposed documenting a set of parameters and algorithms to ensure protection of digital terrestrial TV broadcast services, licensed users of equipment for program creation and special event coverage, as well as services adjacent to the UHF TV band.
Ofcom has already completed initial modeling of the potential effects of its coexistence proposals on the amount of white space spectrum that will be available.
It found: “The constraints required for DTT (digital television transmission) mean that the best performing white space devices can radiate at the maximum permitted power level in three or more 8 MHz channels at around 90 percent of households in the U.K. This figure falls to around 70 percent for less well-performing devices. However, at lower power levels, devices can access considerably more channels and do so from a larger number of locations.”
With regard to wireless microphones, Ofcom found that such devices is”…only likely to impose material additional constraints on white space availability in some locations,” estimating that when combined with DTV transmission constraints they might reduce the availability of white space in Central London, “…so that better-performing devices would only be able to operate at maximum power in nine or more channels at around 90 percent of households. The report noted that in contrast, in Glasgow, Scotland there would be almost no impact on availability.
I previously reported on Ofcom's plans for a U.K. white space project
and described Ofcom rules for white space devices are similar to our FCC rules