UHF2 realignment study - Ofcom Licensing

The benefits of using MASTS in particular for UHF2 assignments is the ability to quantify
the spectrum quality in terms of interference, and determine the amount of available
spectrum for use in the band. Ultimately, MASTS will be used to make more effective
assignments due to the predictive nature of analysis of the interference environment. This
will result in either more channels available for assignment in the same frequency band or
being able to ‘squeeze’ more geographical users from the existing channels. Using the
MASTS algorithm a ‘Band Alignment tool’ was developed and in 2004 it was calculated that
if the assignments were re-packed in the UHF2 band then Ofcom could have had a
spectrum yield of between 2-3MHz 50 .
This tool will assign spectrum based on a set of rules and technical criteria (introduced in
the new (TFAC)) that will determine the spectrum quality and protection requirements. The
tool is also able to take account of terrain and other assignments thereby defining which
frequencies can be used in a particular location. This is a change to the current primary
practice of establishing a generic protection distance between base stations for particular
licence classes.
When the MAST tool is used to assign channels in the UHF2 band, in its current unaligned
state, it is likely that a few more assignments may be made in spectrum otherwise thought
as full. This packing of assignments may lead to incumbents being subjected to more
interference than previously experienced. However it should be noted that all assignments
suffer from interference; the difference with MASTS is that the level of interference will be
planned and part of the licence conditions.
The MASTS process is underpinned by the Technically Assigned licence product for
shared and exclusive use. An assignment can be identified for an activity factor, which is a
measure of what percentage of time an assignment is transmitting. For example, a shared
assignment is an assignment that transmits no more than 50% of the time in its busiest
hour. An exclusive assignment is one that either transmits up to 100% of the time, more
than 50% of the time in its busiest hour or requires extra protection because of either
business or safety critical reasons. The activity factor determines the amount of time that
an assignment may block another assignment from transmitting at that point in time.
With the nature of Business Radio in a shared environment, there may be instances when
a user exceeds the activity factor (as defined by their assignment type) over a short period.
If there are continual breaches of the guideline criteria then it may be necessary to liaise
with the users concerned and move them to Exclusive status or move them to a different
channel (where possible).
MASTS will benefit users of the UHF2 band as it can be used to help reduce the likelihood
of interference by way of more carefully assigning spectrum. MASTS will have the ability to
coordinate aligned and non-aligned UHF2 frequencies that should there be alignment of
the band there are tools in place to aid the development of new systems helping prevent
50 According to the Radiocommunications Agency/Ofcom
240689 - 450-470 Study Final Print
Version (Dec08).doc
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