FINAL REPORT - Stakeholders - Ofcom

HiperLAN) are not used. ERC Report 015 deals with sharing between HiperLAN and
radar operating at 5 GHz and concludes,
“This report has studied the possibility of RLANs sharing with radar in the radiolocation
bands around 5.5 GHz and has assessed the potential for interference from radar
systems to RLANs. Using free space propagation formulae, the required separation
distance between radars and RLANs is limited by the Radio Horizon (50 km for ground
based radar and 340 km for airborne radar). However, this is the worse case and does
not take into account terrain or building attenuation. Further calculations show that the
RLAN could tolerate interference from between 5 and 14 radars at a given time. This is
unlikely to reflect the majority of situations where RLANs will be used (mainly urban areas
at some distance from radar installations), and the geographical distribution of interfering
sources will probably be less than 5 radars within a radius of 50 km. Where an RLAN is
operating within line of sight of one or more radars, the system throughput will be reduced
but still within acceptable limits.”
There are also a number of assignments to Programme Making and Special Events
(PMSE) in the range 5480 – 5815 MHz. These are used for temporary point-to-point video
links as well as radio cameras and portable video links. PMSE transmissions in this band
have a maximum ERP of 40dBW and, where the allocation overlaps with the maritime
radionavigation band, the frequencies must not be used within 10km of the coast. The
fact that these allocations are licensed and co-ordinated means that protection of
maritime services can be, so far as possible, ensured.
ERO Report 006 investigated the potential for sharing between PMSE and radar services
in the frequency band 2700 – 2900 MHz; whilst this is an aeronautical radar band the
findings are, nonetheless, relevant. Fundamentally, the report argues that the coordination
distances between aeronautical radar and PMSE video links was such that it
would require international co-ordination in most cases, and thus be time-consuming. The
report’s overall conclusion was that it would not be possible to share between
(aeronautical) radar and PMSE.
A paper by SE34 considering measures of spectral efficiency for radars (SE34(01)35)
concludes:
“In describing the ways in which radars occupy parts of the spectrum in bandwidth,
time, space and polarization, the opportunities of sharing have been mentioned.
This paper started with a statement that radars do not easily share with other
services. As has been shown there are some limited opportunities for radars to
share with other radars. These cases do not extend to sharing with other services
within the coverage area of the radar except in special circumstances. In general it
is concluded again that radars do not share their spectrum easily”
The key here is that radars do not share well within the coverage area of the radar. With
maritime radar being focussed around the coastline, there are still potential sharing
opportunities inland.
Reduction in available spectrum
In discussions with radar users, it would appear that there is not yet strong evidence of
congestion in the radar bands at present (even in busy shipping lanes such as the English
Channel). Such congestion would appear as numerous unidentified dots on the radar
display. The systems employed by maritime radar systems to block interference from
other radars clearly enable a good degree of sharing.
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