Part 1 Introduction
1.1 Name of these Guidelines [see Note 1]
These Guidelines are the Radiocommunications Advisory Guidelines (Managing Interference to Apparatus Licensed Receivers — 3.4 GHz Band) 2000.
1.2 Commencement
These Guidelines commence on 17 July 2000.
1.3 Purpose of these Guidelines
These Guidelines set out compatibility requirements for point to multipoint fixed service receivers operating under apparatus licenses in the 3400-3700 MHz band with respect to transmitters operated under a spectrum licence. The compatibility requirements are set out in Part 3.
1.4 Interpretation
In these Guidelines, unless the contrary intention appears:
commencement date means the date these Guidelines commence.
in‑band:
(a) for a transmitter operated under a spectrum licence, or for a receiver operated within the space of a spectrum licence: and
(b) for a transmitter or a receiver operated under an apparatus licence; means the frequencies within a frequency band to which the licence relates.
incumbent, for a receiver, means a receiver that has part of the frequency band of its spectrum access, and its location, within the re-allocation of the 3.4 GHz band when that band was re‑allocated.
Marketing Plan means the Radiocommunications Spectrum Marketing Plan (3.4 GHz Bands) 2000.
out‑of‑band interference means interference relating to selectivity (except when caused by in‑band emissions), blocking, intermodulation immunity and spurious response immunity.
point to multipoint fixed service receiver means a receiver in a point to multipoint system that is licensed as a point to multipoint station.
RALI FX14 means the Radiocommunications Assignment and Licensing Instruction No.FX14 issued by the ACMA, as in force from time to time, copies of which are available from the ACMA.
RALI FX19 means the Radiocommunications Assignment and Licensing Instruction FX19 issued by the ACMA, as in force from time to time, copies of which are available from the ACMA.
RALI MS3 means the Radiocommunications Assignment and Licensing Instruction No.MS3 issued by the ACMA, as in force from time to time, copies of which are available from the ACMA.
section 145 determination means the Radiocommunications (Unacceptable Levels of Interference – 3.4 GHz Band) Determination 2000.
3.4 GHz band means the following frequency bands:
(a) 3425 MHz – 3475 MHz;
(b) 3475 MHz – 3492.5 MHz;
(c) 3542.5 MHz – 3575 MHz.
3.4 GHz frequency segments means the 3425-3442.5 MHz and 3475‑3492.5 MHz segments of the 3.4 GHz band.
3.6 GHz band means the frequency band 3575-3700 MHz.
Part 2 Background
2.1 Application of these Guidelines
These Guidelines apply to:
(a) receivers of apparatus licensed services operating in the 3400‑3700 MHz band that are outside designated spectrum space; and
(c) incumbent receivers.
2.2 Background
(1) At the commencement date, the 3.4 GHz frequency segments are available for apparatus licensing in regional and remote areas of Australia only. The ACMA has placed an embargo on the issue of new apparatus licences in these frequency segments in the geographic areas specified in RALI MS 3, with effect from 31 August 1998. Systems operating under apparatus licences in the embargoed areas that were licensed before the embargo date are regarded as incumbent services and will be subject to re‑allocation provisions.
Note For the reallocation period, see the declaration under s 153B.
(2) The 3.6 GHz band is available for apparatus licensing in regional and remote areas of Australia only. The ACMA has placed an embargo on the issue of new apparatus licences for this band in the geographic areas specified in RALI MS3.
(3) Apparatus licence applications are subject to the frequency assignment requirements detailed in RALI FX14 and RALI FX19. In certain locations, additional coordination requirements apply due to the shared nature of frequencies in those areas.
Part 3 Compatibility requirements
3.1 Types of interference
(1) There are a number of interference mechanisms that need to be considered in order to protect the receivers of these apparatus licensed services from devices operating under spectrum licences.
(2) Receivers may suffer interference from unwanted emissions generated by the presence of a spectrum licensed transmitter. Unwanted emissions are by‑products of a transmitter’s emission. They include modulation products, broadband noise, harmonics, intermodulation products, transient signals, and other spurious signals. Modulation products from transmitter emissions may reduce the adjacent channel isolation between systems and cause adjacent channel interference.
(3) Receivers may also suffer interference due to the effects of blocking, intermodulation and spurious response from high level emissions from transmitters. Blocking occurs in a receiver when high level off‑tune signals cause a degradation in the quality of the wanted output signal, produced by the overloading of the receiver’s front‑end. Intermodulation products can be generated in the input stages of receivers in the presence of two or more high level signals at the receiver input.
3.2 Types of compatibility requirements
(1) These interference mechanisms and co‑ordination requirements result in in‑band compatibility requirements across area boundaries and out‑of‑band compatibility requirements across frequency boundaries.
3.3 In‑band compatibility requirements across area boundaries
(1) For receivers outside spectrum space that were licensed before the date of the Marketing Plan, the requirements are set out in clause 3.9. These requirements apply only while the apparatus licence is in force.
(2) For receivers outside spectrum space that were licensed after the date of the Marketing Plan, licensees must accept emission levels as long as those levels are not unacceptable because of clause 7 (3) of the section 145 determination.
(3) For incumbent receivers, the requirements are set out in clause 3.9. These requirements apply from the time of re‑allocation until the end of the re‑allocation period.
3.4 Out‑of‑band compatibility requirements across frequency boundaries
(1) Out‑of‑band compatibility requirements are managed with coordination procedures and supported with interference settlement based on ‘first‑in‑time’ registration as set out below.
3.5 Out‑of‑band compatibility requirements: receivers outside spectrum space
(1) This clause applies to apparatus licensed receivers that are outside designated spectrum space, whether their apparatus licence is issued before or after the date of the Marketing Plan.
(2) Apparatus licensed receivers:
(a) are to be provided with out‑of‑band protection from interference caused by frequency adjacent transmitters operated under spectrum licences that are registered after the issue date of the apparatus licence under which the receiver operates; and
(b) must accept interference from frequency adjacent transmitters that are registered before the issue date of the apparatus licence and whose interference potential does not increase after that date through variation of the registered device details.
Note The interference potential for a transmitter operated under a spectrum licence increases when the emission centre frequency changes, the effective occupied bandwidth increases, or the device boundary expands.
3.6 Out‑of‑band compatibility requirements: incumbent receivers
Incumbent receivers are provided with out‑of‑band protection from interference cause by frequency adjacent transmitters operated under spectrum licences from the time of re‑allocation until the end of the re‑allocation period.
3.7 Propagation
(1) Radio waves propagate in a number of different ways due to many factors, for example:
(a) frequency;
(b) terrain;
(c) atmospheric conditions;
(d) path length.
(2) As a result, a number of propagation models have been developed to predict path loss. Part 4 contains various propagation models to provide guidance on the choice of suitable models to be used in determining whether the compatibility requirements have been met.
3.8 Maximising spectrum utility and efficiency
(1) To meet the compatibility criteria set out in clause 3.9, when deploying new systems spectrum licensees may find it necessary to incorporate additional hardware such as filters to their transmitters (above the normal system configurations). This may be particularly needed when stations are planned to be close to apparatus licensed services in terms of either frequency or distance. Where this is not sufficient to ensure protection to potentially affected apparatus licensees’ receivers, negotiations between the affected parties, with a view to reduced (but acceptable) protection or the fitting of additional protection devices (filters etc) to receivers, may be able to resolve such situations.
(2) Similarly, apparatus licensees may find it necessary to negotiate with spectrum licensees when planning the deployment of their transmitters, to meet the compatibility requirements for the protection of registered receivers operating in spectrum licensed space.
Note 1 For these requirements, see the Radiocommunications Advisory Guidelines (Managing Out‑of‑band Interference in Receivers Operating in Spectrum Licensed Space–3.4 GHz Band) 2000 and the section 145 determination.
Note 2 The requirements will also be included in licence conditions, where necessary.
3.9 Compatibility requirements for point to multipoint fixed service receivers
(1) The compatibility requirements for point to multipoint fixed service receivers are as set out in RALI FX14 and RALI FX19.
(2) The assignment principles of RALI FX14 are based on the concept of point to multipoint services using cellular technology. ITU Recommendation R.757 (Basic system requirements and performance objectives for fixed wireless local loop applications using cellular type mobile technologies) provides advice on grade service and availability requirements for these services.
(3) The assignment principles of RALI FX19 are deliberately biased towards permitting a high level of spectrum re‑use while affording reasonable (though not excessive) levels of protection to the notional point to multipoint fixed service area. The maximum unwanted signal level for point to multipoint fixed service receivers has been based on a level equivalent to the noise floor of the receiver.
Part 4 Propagation models
4.1 Types of propagation models
(1) A number of propagation models have been developed to estimate the path loss between a transmitter and receiver. The choice of a particular propagation model will depend on a number of factors, for example:
(a) the terrain between the radio path end points; and
(b) any obstructions on the path either natural or man‑made; and
(c) the heights of the transmit and receive antennas.
(2) Propagation models can be classified into two different types; point‑to‑point and point‑to‑area.
(3) ITU Recommendation P.1144 provides guidance on the applications of the various propagation models developed internationally by the ITU. Table 1 is an extract of the 1995 issue of ITU Recommendation P.1144 and provides a summary of the ITU propagation models relevant to services operating in the 3.4 GHz band and 3.6 GHz band. The models provide an estimation of either path loss or received field strength.
(4) Most models include statistical evaluation of path loss or signal levels expected at certain percentages of locations for certain percentages of times. Some propagation models produce a result that represents the median signal level. The median signal level corresponds to a level that is exceeded 50% of the time in 50% of locations. The median level is useful for estimating coverage. It is not suitable for interference calculations as interference for 50% of the time is generally considered unacceptable. Therefore, care must be taken when using propagation models to predict interference levels to ensure that the result represents the signal level exceeded for a sufficiently small percentage of locations for a sufficiently low percentage of time, as appropriate for the circumstance. Median signal levels may be converted to other time and location percentages (eg, 1% of the time and 10% of locations) by applying appropriate correction factors.
4.2 Point‑to‑point models
(1) Point‑to‑point models allow the prediction of path loss between a fixed transmitter and a fixed receiver. Two of the main propagation modes are:
(a) free space loss (line‑of‑sight); and
(b) diffraction loss, including smooth earth diffraction and diffraction over obstacles and irregular terrain (known as “knife‑edge diffraction”).
(2) The free space loss propagation model is usually used where paths are line‑of‑sight and there are no obstructions within the first Fresnel zone for a given k‑factor. This usually occurs with services located on high sites such as mountain tops, towers or buildings.
(3) The diffraction loss propagation model is typically used where paths are obstructed by the earth’s curvature or terrain. The model gives a loss due to diffraction which must be added to the free space loss to give the total path loss.
(4) A plot of the terrain profile is usually generated to determine which propagation model is most appropriate to a particular propagation path.
(5) Information on how to determine propagation losses due to free space and diffraction over a spherical earth, obstacles and irregular terrain can be found in ITU‑R Recommendation P.526. Additional propagation loss due to effects such as tropospheric scatter, ducting, layer reflections and clutter can be found in ITU‑R Recommendation P.452. Other models such as the Longley‑Rice model in the point‑to‑point mode may also be suitable.
4. 3 Point‑to‑area models
(1) Point‑to‑area models provide for the prediction of field strength levels in a geographic area from a base station transmitter. They are useful for estimating the coverage area of base stations in which receivers are to be protected from interference and to estimate interference to mobile/fixed receivers from other services. They are statistical in nature and usually based on the statistical analysis of measured data and take into account factors such as Raleigh fading, shadowing and clutter loss.
(2) ITU‑R Recommendation P.529 provides guidance on the prediction of field strength for the land mobile service in the VHF and UHF bands. It contains
(a) curves for predicting median field strengths for 50% of locations for 50% of the time under average conditions; and
(b) correction factors that can be used to refine the average predictions to take account of the terrain.
(3) The curves are based on measurements made by Okamura and Hata in Japan. They are normally applied to mobile applications where the base station antenna is high and the mobile antenna is low (typically 1.5 metres above ground). Correction factors can be applied to the curves to accommodate other percentages of time and percentages of locations.
(4) Other point‑to‑area models such as those developed by COST (COST231‑Hata) or Longley‑Rice in the point‑to‑area mode may also be appropriate as they include factors for clutter (buildings, trees etc) with low receive antenna heights.