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FINAL REPORT - Stakeholders - Ofcom

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3.4.5.3 ILS<br />

ILS frequencies will be protected for the foreseeable future – even if MLS and GLS are<br />

implemented, these systems are expensive, and will not provide additional functionality<br />

for many users (i.e. they have a negative cost-benefit case for new equipment).<br />

ICAO Annex 10 and CAA Cap 670 define the standards and performance limits on ILS<br />

operation.<br />

3.4.5.4 VHF VOR<br />

EUROCONTROL strategies recommend the rationalisation of the European navigational<br />

infrastructure – as part of this, the decommissioning of VORs is proposed within 2010<br />

timescales. With the WRC 2003 decision to allow primary use of the VHF spectrum by<br />

aeronautical mobile radionavigation services, further pressure is expected to be placed<br />

for the decommissioning of VORs.<br />

Note however that issues exist with the full phase-out of VORs (and NDBs). Firstly,<br />

General Aviation will be forced to equip with GNSS or RNAV computers. A low-cost<br />

system for GA is essential before this can happen. Secondly, there is the proposed<br />

reliance on RNAV for navigation, with no back-up to this method. Studies are currently<br />

on-going in EUROCONTROL investigating the potential impact of a solely RNAV future<br />

environment.<br />

Protection is also afforded to, and from, the FM broadcasting services operating in the 87-<br />

108MHz band.<br />

3.4.5.5 C-Band MLS<br />

The spectrum allocated to MLS by ITU extends from 5000 to 5250 MHz but ICAO<br />

currently specifies only the sub-band from 5030 to 5090 MHz and reserves the upper<br />

band for future use. The lower 30 MHz were allocated to GNSS at the World Radio<br />

Conference in 2000. Fixed Satellite Services operate in the 5090 to 5150 MHz band on a<br />

non-interference basis. WRC-03 modified Radio Regulation footnotes 5.444 & 5.444A<br />

and Resolution 114 (Rev.WRC-03) which relates to this band.<br />

3.4.5.6 L-Band DME<br />

ICAO Annex 10 specifies strict co-channel and adjacent channel geographical separation<br />

criteria. This becomes an issue when looking at full DME coverage across the ECAC area<br />

to support RNP-RNAV operations. A regulated PFD (power flux density) may be the best<br />

way to ensure cross-channel interference is minimised; WRC-03 proposed this solution,<br />

but no firm decision has yet been taken.<br />

The ITU in Recommendation M.1639 has determined an EPFD (equivalent power flux<br />

density) limit for RNSS in the L-Band (particularly 1164-1215MHz), to protect ARNS – the<br />

methodology can be found in ITU Recommendation M.1642. In the short term, the focus<br />

is upon the protection of ARNS. In the much longer term, as GNSS becomes more<br />

prevalent in aviation, it could be argued that the focus will shift to prioritise the protection<br />

of GNSS signals. This will depend on the ability of the relevant bodies to prove the<br />

performance of sole-means GNSS-based solutions.<br />

3.4.5.7 L-Band GNSS<br />

GNSS is constrained by strong standardisation and regulatory requirements. GNSS<br />

signals impact on currently used ground-based navigation aids such as DMEs and<br />

primary radars. In order to protect existing ARNS allocations, the ITU has imposed an<br />

aggregate EPFD limit on all RNSS signals.<br />

Page 104

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