This section summarises:
- the technical framework underpinning licensing in the 27 GHz Band,
- the purpose and operation of the s.145 Determination of Unacceptable Interference,
- the three Advisory Guidelines that manage in-band and out-of-band interference with other services; and
- other important information about the technical framework
The technical framework for the 27 GHz band has been established by the ACMA to support broadband wireless access (BWA) services provided by two-way fixed point-to-point and point-to-multipoint radio-communications systems. It has evolved from the technical frameworks of previous spectrum licence allocations, in particular those established to support broadband wireless access (BWA) services.
The framework aims to minimise negotiation necessary between adjacent licensees for the management of both in-band and out-of-band interference in most circumstances. Nonetheless, spectrum licensees may negotiate among themselves and, where relevant, apparatus licensees, for alternative management arrangements regarding emission levels.
Spectrum licensees should note, however, that alternative arrangements are not possible unless all affected and potentially affected licensees have agreed to them. Included in these flexibility provisions is a prescribed Form of Agreement (included in the Radiocommunications Spectrum Marketing Plan (27 GHz Band) 2000. The Form of Agreement provides a template for any agreements that relate to spectrum licensees agreeing to accept emissions that would, in the absence of those agreements, exceed the core conditions of their spectrum licence(s). For example, spectrum licensees might agree alternative arrangements with other licensees for higher levels of emission outside the frequency band of the spectrum licence, or for higher levels of radiated power across a geographic area boundary, than would have otherwise been allowed. New flexibility within the core conditions of licences gives effect to such arrangements between licensees.
Licensees are advised to review carefully the arrangements set out for agreements between spectrum licensees, and between spectrum licensees and others, contained in the Radiocommunications Spectrum Marketing Plan (27 GHz Bands) 2000.
The inherent flexibility of a spectrum licence acquired in this allocation is left for the licensee to determine. This should, however, be based on a careful technical and commercial assessment before the auction, in order to confirm that the desired spectrum space is sufficient to sustain the performance of the network and equipment the bidder desires to operate. The spectrum lots and subsequently issued licences are not pre-designed to accommodate any particular standard. They may accommodate the operation of a particular standard, as well as non-standard equipment, at a particular location and frequency, depending on the size and shape of the licence acquired.
The technical framework is crafted using four regulatory elements. They are:
- licence core conditions, which are mandatory requirements made under the s.66 of the Radiocommunications Act 1992 (the Act);
- other licence conditions, made under s.71 of the Act;
- a Determination of Unacceptable Interference for the purpose of device registration, made under s.145 of the Act; and
- Radiocommunications Advisory Guidelines, made under s.262 of the Act.
The licence core conditions and the Determination of Unacceptable Interference are used to keep significant levels of emission within the spectrum space of the licence. Other licence conditions are used to protect the satellite receivers of international space services.
The advisory guidelines provide a framework for the coordination of specific devices as required, usually associated with domestic spectrum licensed and apparatus licensed services operating within the limits of the 27 GHz band and surrounding spectrum.
The technical framework is predicated on the assumptions that:
- spectrum and apparatus licensees will employ good engineering practice in establishing and maintaining their services;
- receivers employed by spectrum licensees will, as a minimum, meet the minimum receiver performance levels set out in Schedule 1 of the Radiocommunications Advisory Guidelines (Managing Interference from Non-spectrum-licensed Transmitters - 27 GHz Band) 2000 (see also Receiver Performance below); and
- spectrum licensees will be responsible for managing interference that they, or their third party authorisees, cause to their own services.
The following general principles underpin this technical framework:
- the ACMA has attempted to provide the maximum flexibility to spectrum licensees to establish services;
- Emission limits have been specified as absolute power levels rather than power levels relative to transmitter power, allowing licensees to strike a balance between the maximum radiated power of a device and its out-of-band performance.
- The core conditions indirectly specify frequency stability by requiring the emission limits outside the band to be maintained under all conditions. A licensee is able to balance device emission bandwidths against frequency stability, including considerations of transmitter transient behaviour, by providing internal ‘guard bands’ as necessary.
- Spectrum licensees have the responsibility to manage interference that arises within 200 metres of devices registered under their licences.
- The size of the Standard Trading Unit (50 MHz) provides a sufficient band of spectrum for licensees to provide their own guard band arrangements to manage interference between themselves and other licensees.
The interference mechanisms that the technical framework seeks to manage are those caused by:
- unwanted in-band emissions;
- emissions falling outside the frequency band of the licence;
- transient unwanted emissions such as those caused by switching a transmitter on or off; and
- intermodulation effects.
In the 27 GHz band these four mechanisms are dealt with by a combination of the core conditions relating to out-of-area and out-of-band emissions, other licence conditions, and those parts of the registration process which give effect to those conditions at the point of registration of devices prior to their operation. It should be noted that agreements between licensees can only continue to apply while the size and the shape of the spectrum space owned by licensees remain unchanged. Where trading of licences takes place and new boundaries are formed, these agreements will need to be re-negotiated. This re-negotiation can occur at any time, that is, before or after the trade, so that there is no loss of flexibility to licensees.
When trading occurs by means of the division of spectrum space, and agreements are not in place, a check will be required to ensure that devices meet the requirements of the licence within the changed spectrum space. The comments made within this chapter indicating how the interference management regime might affect proposed services and spectrum utility are not intended to be exhaustive. Potential spectrum licensees are reminded to take such expert technical and other advice as they consider necessary to inform themselves of possible effects on their proposed services.
Licence core conditions
This part of the section explains what the core conditions of the licence are intended to achieve (a sample licence can be found in Schedule 5 of the Radiocommunications Spectrum Marketing Plan (2 GHz Band) 2000, and how the emissions subject to those conditions are further managed under the technical framework.
For each licence, the core conditions set out:
- the geographic area;
- the frequency band;
- the out-of-area emission limits; and
- the out-of-band emission limits.
The geographic area or aggregate of areas within which the operation of radiocommunications devices is authorised by the licence is described in Part 3 of Licence Schedule 1.
[Note: The coordinate system used in Part 3 of Licence Schedule 1 is different to the coordinate system used to describe the licence areas in Schedule 2 of the Marketing Plan.]
The frequency band of the licence within which the operation of radiocommunications devices is authorised by the licence consists of the contiguous range of frequencies between the upper and lower frequency limit set out in Part 2 of Licence Schedule 1.
Out-of-area emission limits, through the Determination of Unacceptable Interference, protect geographically adjacent licensees. A fixed transmitter operated under a 27 GHz spectrum licence may be located anywhere in the geographic area of the licence. However, emissions from the transmitter may not cause the radiated powers outside the geographic bounds of the licence to exceed the limit imposed by core conditions 3 to 6 of the licence; as mentioned previously these limits can be extended by agreement with adjacent licensees.
The out-of-area radiated power limit for a wide beamwidth transmitter (where the antenna beamwidth is greater than 5 degrees) is 65 dBm/MHz. The out-of-area radiated power limit for a narrow beamwidth transmitter is 79 dBm/MHz. These limits are such that currently available commercial transmission equipment can be operated in most configurations without restriction arising from these core conditions, up to the boundary of the licence.
They are the same as provided for in the technical framework for the 28 GHz and 31 GHz spectrum licensed bands. It should be noted that the definition of the out-of-area limit effectively places a cap on the radiated power of transmitters anywhere in the area of the licence.
The distinction between wide beamwidth and narrow beamwidth transmitters takes into account the difference in their potential to cause interference to other services. This distinction is used throughout the technical framework. The antenna beamwidth indirectly distinguishes between hub transmitters in point-to-multipoint systems and subscriber transmitters in point-to-multipoint systems or transmitters in point-to-point systems.
Out-of-band emission limits, through the Determination of Unacceptable Interference,protect licensees in adjacent spectrum. Out-of-band emission limits are imposed by core conditions 7 to 16 of the licence. They are the same as provided for in the technicalframework for the 28 GHz and 31 GHz spectrum licensed bands. These levels may be varied through negotiated agreement with affected adjacent licensee. The form of agreement described previously also applies to these agreements with spectrally adjacent licensees. A licensee or accredited person must work out the radiated power of the device within bandwidths outside the frequency band of the licence using good engineering practice to establish whether the operation of a device will cause ‘unacceptable interference’ by breaching these emission limits. If the power so calculated is greater than a figure specified in the relevant licence condition, two things follow:
- if the device is not yet registered the ACMA will generally refuse to register it, because the interference that it would cause will be ‘unacceptable interference’ within the meaning of s.145 of the Act, (unless, for example, all relevant licensees agree alternative arrangements);
- if the device is already registered - there will be a breach of the core licence condition, unless, all relevant licensees have agreed to the alternative arrangements. Out-of-band emission limits have been expressed in the form of absolute levels, rather than levels relative to the transmitter output power, to allow licensees to operate transmitters with an optimised balance between power and out-of-band emission suppression.
The limits for out-of-band emissions have been chosen to enable adjacent STU operation beyond the licensee 200m interference management zone.
Other licence conditions
Whilst core conditions go some way to limit interference to adjacent services their primary purpose is to define the coverage of the spectrum licence. Some additional protection from interference may be required beyond that provided indirectly through the core conditions.
One method of implementing this protection is by including other conditions in the licence. For the 27 GHz technical framework, a number of conditions have been added to protect international space services with which this band is shared.
Protection for space services
Under ITU Radio Regulations the 27 GHz band is shared with the inter-satellite service (ISS) and the earth-exploration-satellite service (ESS)(space to earth). The 27 GHz band is also shared with the fixed-satellite service (FSS)(Earth-to-space). The ACMA is including a number of conditions to protect satellite receivers in these services.
General limits on terrestrial transmitters are specified in ITU Radio Regulations Chapter SVI, Article S21 Terrestrial and Space Services sharing Frequency Bands above 1 GHz.
- The maximum true mean power of a transmitter must not exceed 40 dBm; and
- The maximum radiated true mean power radiated from the antenna of a transmitter must not exceed 85 dBm.
Further to these general limits, in 1997 international agreement was reached on technical limits for fixed services in the band 25.25-27.5 GHz to enable sharing with the ISS.
Recommendation ITU-R F.1249 Maximum Equivalent Isotropically Radiated Power of Transmitting Stations in the Fixed Service Operating in the Frequency Band 25.25-27.5 GHz Shared with the Inter-Satellite Service specifies EIRP limits in the direction of the Geostationary Orbit (GSO) for all fixed services in the band. The following additional limits exist in the direction of the specific GSO locations (see following table) and all other GSO locations:
- Generally, a narrow beamwidth transmitter must not radiate a maximum true mean power exceeding 54 dBm/MHz above the horizontal plane in the direction of the specified GSO locations.
- An exception is that a transmitter in which automatic power control is implemented may increase its power by an amount not exceeding the attenuation due to precipitation, up to a maximum of 63 dBm/MHz.
- In the direction of all other GSO locations the limit is 63 dBm/MHz. The ACMA has incorporated these limits as licence conditions, but may allow levels greater than these limits on a case by case basis if the licensee shows that the recommendations of ITU-R F.1249 have been met.
Specified Geostationary Orbit Locations
16.4o E, 21.5o E, 47o E, 59o E, 85o E, 90o E, 95o E, 113o E, 121o E, 160o E, 177.5o E, 174o W, 171o W, 170o W, 160o W, 139o W, 62o W, 49o W, 46o W, 44o W, 41o W, 32o W, 16o W
NOTE: These are the GSO locations identified in ITU-R SA.Doc.7/97 and ITU-R SA.1276 as referred to in Recommendation ITU-R F.1249 (1997) and Draft New Recommendation ITU-R F.[PMP]. Copies are available from the ACMA. Subsequent ITU-R work made it clear that Recommendation F.1249, which was developed from technical considerations of point-to-point systems, was not suitable to address sharing between the ISS and the hubs (wide beamwidth transmitters) of point-to-multipoint systems. Accordingly, ITU-R Joint Rapporteur Group 7D/9D has recently developed Draft New Recommendation (DNR) ITU-R F.[PMP] Technical and Operational Requirements that Facilitate Sharing between Point-to-Multipoint Systems in the Fixed Service and the Inter-Satellite Service in the Band 25.25-27.5 GHz, for accelerated approval.
The ACMA has added the following limits in the direction of the specific GSO locations and in all other directions to implement the recommendations of the DNR:
- Generally, a wide beamwidth transmitter must not radiate a maximum true mean power exceeding 38 dBm/MHz at angles above the horizontal plane less than or equal to 20 degrees, and that are in the directions of the specified GSO locations. Above 20 degrees and up to 90 degrees above the horizontal plane the level decreases with increasing angle down to 31.4 dBm/MHz at 90 degrees.
- Generally, a wide beamwidth transmitter must not radiate a maximum true mean power exceeding 44 dBm/MHz at angles above the horizontal plane less than or equal to 5 degrees, for any other directions than toward the GSO locations. Above 5 degrees and up to 90 degrees above the horizontal plane the level decreases with increasing angle down to 31.4 dBm/MHz at 90 degrees.
- Automatic power control may be used up to a radiated maximum true mean power of 47 dBm/MHz.
The ACMA may allow levels greater than these limits on a case-by-case basis if the licensee shows that the recommendations of the DNR have been met. Should the DNR be changed during its progression to becoming a Recommendation the ACMA may reflect these changes in changes to the licence conditions.
Interference management at sites
The licence also includes a condition requiring the licensee to manage interference within 200m of a device operated under this licence. This condition has been included due to the difficulty in specifying emission limits to prevent interference between a large range of services that may operate in close proximity at prime radiocommunications sites.
To manage out-of-band interference, spectrum licensees may for example have to utilise guard bands between licensees, install filters at the edges of their spectrum, and/or negotiate with adjacent licensees either to employ transmitter filtering or avoid placing transmitters near the frequency boundary at certain locations.
Determination of Unacceptable Interference
Before a transmitter can be operated under a spectrum licence its details must be recorded in the Register of Radiocommunications Licences. The ACMA may refuse to register a device if the licensee or accredited person cannot show that the requirements deemed to prevent unacceptable interference are met. Consequently the ACMA requires that each registration be issued a certificate in accordance with the Radiocommunications (section 145(3) Certificates) Determination 2000. There are three options available to licensees and accredited persons to issue a certificate.
The first option is to meet the requirements detailed in the relevant determination made by the ACMA under section 145(4) of the Radiocommunications Act 1992 (s.145 Determination) - see the Radiocommunications (Unacceptable Levels of Interference – 27 GHz Band) Determination. The s.145 Determination sets out basic requirements to manage unacceptable levels of interference, and states that:
- that the core conditions of the licence are met;
- that other conditions of the licence are met;
- that full details of the transmitter are provided for the register; and
- that the transmitter is not attached to a balloon higher than 100m above the ground.
The Determination also sets out the definition of a group of transmitters and a group of receivers for the purpose of simplifying registration of those devices. The Determination specifies how the registration details for a group of transmitters and receivers must be calculated.
If a devices does not comply with the Radiocommunications (Unacceptable Levels of Interference – 27 GHz Band) Determination there are two alternative options available to an accredited person to issue certificates for device registration:
- show that sufficient guard space has been allocated to manage potential interference within the spectrum space of the licensee; or
- obtain written agreement from all affected licensees to accept a higher level of interference.
Guidance on the registrations of radiocommunications devices via guard space and agreements is provided in the information paper Registration of radiocommunications devices under spectrum licences (Word [.docx] or PDF formats).
The corollary of this aspect of interference management is that spectrum licensees must expect that certain levels of emission will legitimately cross their geographic (and spectrum) boundaries from points within other spectrum licensed areas. Accordingly, when considering what services they might establish within their own geographic areas, spectrum licensees should take into account the fact that transmitters may be located at certain points within other spectrum licensed areas. Furthermore, those transmitters may radiate power into the spectrum licensee’s area at any level up to that allowed under the relevant s.145 determination of unacceptable interference, or levels otherwise negotiated with the relevant spectrum licensees.
The ACMA recommends that radiocommunications devices be registered at the system design stage. This will enable other licensees, if they wish, to re-check the coordination and if an obvious error is detected, negotiate directly with the spectrum licensee before further costs are incurred when transmitters cannot be operated due to interference. The registration of devices that are never intended to be operated is not recommended because this has the potential to inhibit unnecessarily the operation of adjacent licensees’ devices through coordination requirements. .
There are three Radiocommunications Advisory Guidelines made under s.262 of the Act issued by the ACMA associated with spectrum licensing of the 27 GHz band. They are:
- Radiocommunications Advisory Guidelines (Managing Interference from Non-spectrum-licensed Transmitters—27 GHz band) 2000; and
- Radiocommunications Advisory Guidelines (Protection of Non-spectrum-licensed Receivers—27 GHz band) 2000; and
- Radiocommunications Advisory Guidelines (Managing Interference between 27 GHz and 28 GHz Spectrum Licensed Services) 2000.
These guidelines do not bind licensees or the ACMA. The ACMA has adopted this approach in order to provide the maximum flexibility for both spectrum and apparatus licensees in how they arrange their affairs so as to avoid interference with each other’s services. The ACMA is prepared to consider alternative interference management arrangements agreed between spectrum licensees and, where relevant, apparatus licensees. Spectrum licensees should note, however, that the ACMA will not give effect to alternative arrangements unless all affected and potentially affected licensees have agreed to them (subsequent trading of spectrum will affect any agreements made previously). Licensees who cannot resolve interference issues between themselves may expect the ACMA to have regard to the guidelines in dealing with such disputes.
Managing interference from non-spectrum-licensed transmitters
The Radiocommunications Advisory Guidelines (Managing Interference from Non-spectrum-licensed Transmitters-27 GHz band) 2000 contains information for spectrum licensees on managing interference from non-spectrum-licensed services. Whilst there are no services licensed in Australia to operate in the 27 GHz band licensees should be aware that there are emissions from satellite services to be considered in planning services. Only registered receivers will receive protection in the planning of services by the ACMA. For the case of managing interference from out-of-band services the ACMA has in this guideline set out a minimum performance level for receivers in the 27 GHz band and a compatibility requirement for transmitters of non-spectrum-licensed services. These criteria form a model on the basis of which spectrum and apparatus licensees are expected to develop co-ordination procedures for the management of interference to each other’s services, using good engineering practice.
Protection of non-spectrum-licensed receivers
The Radiocommunications Advisory Guidelines (Protection of Non-spectrum-licensed Receivers-27 GHz band) 2000 contains information for spectrum licensees regarding protection they should provide to non-spectrum-licensed receivers. Whilst there are currently no services licensed in Australia to operate in the 27 GHz band licensees should be aware that there are relevant international space services. Most of the requirements to protect these space services are related to protection of satellite receivers and have been included as conditions of the licence. Licensees should be aware that because of technological change these guidelines and licence conditions may change over the 15 year period of the spectrum licence. Licensees are encouraged to support the future deployment in Australia of earth stations intended to receive signals from Earth-exploration satellites for scientific purposes in the 27 GHz band, should this occur in the future.
Managing interference between 27 GHz and 28 GHz spectrum licensed services
The Radiocommunications Advisory Guidelines (Managing Interference between 27 GHz and 28 GHz Spectrum Licensed Services) 2000 sets out the relationship between spectrum licensed services in the abutting 27 GHz and 28 GHz bands. The relationship between spectrum licensees in the 27 GHz band and the 28 GHz band is the same as the relationship between spectrum licensees within the same band.
As mentioned previously, licensees will need to take account of the emission limits permitted under the technical framework when deciding the level of performance they require for their receivers. Receivers will cope with emission levels with differing degrees of success, depending on their interference susceptibility. A receiver with poor performance would normally deny large amounts of spectrum space for transmitters in order to protect it from interference.
The ACMA does not intend to enforce receiver standards. It is for each licensee to balance the cost of receiver performance against the cost of spectrum space denied to their transmitters. Poor receiver performance is only an issue when a licensee attempts to use spectrum space belonging to an adjacent licensee as part of the receiver protection requirement.
The framework provides for the operation of receivers that have an interference susceptibility commensurate with that achieved by current technology and intends for this level of performance to guide the interference settlement process. Receivers with poor interference susceptibility performance can be used, but in those cases licensees may have to use more of their own spectrum space as guard space. For example, interference that results from a receiver having an RF or IF bandwidth that is larger than the frequency band of the licence will be the licensee’s responsibility. It is the licensee’s responsibility to use receivers in a manner that is both consistent with good engineering practice and effectively copes with the levels of emissions permitted under the technical framework.
The ACMA has placed no constraints on the deployment of transmitters under the 27 GHz technical framework. Likewise the ACMA does not intend to impose deployment constraints on receivers. This means that the onus will lie on spectrum licensees to determine the best siting for their receivers, having regard to the overall technical framework and the rights of other licensees. It is important to note that the technical framework does not provide any protection from intermodulation effects where transmitters are sited within 200 metres of each other. Spectrum licences in the 27 GHz band include a condition that has the effect of requiring spectrum licensees to come to an arrangement with neighbours in relation to interference management in such cases.
Interference that the technical framework does not prevent
No matter how rigorous the engineering analysis of a device, there is always a possibility of actual interference when devices are deployed in the field. This is because the technical framework is designed according to certain levels of acceptable interference probability. Under the framework described in this Chapter, it is anticipated that interference between spectrum licensed devices will occur at about the same rate as between apparatus licensed devices, that is, interference will arise in fewer than one percent of cases. Such interference may be caused by emissions at frequencies either inside or outside licensees’ spectrum space.
Licensees are strongly advised before making an interference complaint to attempt to locate the source of any interference by checking the Register of Radiocommunications licences. This investigation may reveal the cause of the interference and it may be possible to settle the problem without the ACMA’s intervention. If the ACMA becomes involved, licensees may be charged for any work undertaken.
Registering groups of transmitters
Unless exempted, transmitters must always be registered as either an individual transmitter or as part of a group of transmitters. If two or more transmitters are operated for the purpose of communicating with the same receiver or same group of receivers and they have identical emission characteristics, then those transmitters may be treated as a group in order to simplify the registration process. A transmitter may belong to more than one group.
Groups are defined to help minimise the work associated with the registration process of similar transmitters, for example, subscriber transmitters and multiple transmitters at a hub. Subscriber transmitters may be registered as a group. A group of devices may have location details consisting of a centre and an associated effective radius that can take into account the distribution of subscriber transmitters. Mobile and indoor transmitters are exempted from device registration requirements. Licensees may decide whether to register receivers based on a risk assessment of the benefits achieved through coordination to manage out-of-band interference.
The ITU Radio Regulations have international treaty status and are binding on Australia. Transmitters operated under a spectrum licence, other than in accordance with ITU Radio Regulations, must not cause interference to any services of any other country (for example, Papua New Guinea or Indonesia) which are operating in accordance with ITU Radio Regulations. If operation of a transmitter does cause harmful interference to overseas services operating in accordance with ITU Radio Regulations, the transmission must cease. Spectrum licensees must also accept interference from any overseas service operating in accordance with ITU regulations.
Spectrum licensees should note that the ACMA will impose such additional licence conditions on spectrum licences as may be necessary from time to time to meet Australia’s international obligations. Health and safety Every spectrum licensee will need to take into account occupational health and safety requirements for radiofrequency devices. Occupational health and safety requirements that concern use of radiofrequency devices are currently the responsibility of State and Territory Governments.
In addition, licensees will be required to comply with any health exposure standards that may be made by the ACMA for the health and safety of persons who operate, work on or use radiocommunications transmitters and receivers.
Environmental and other considerations
Antenna siting, height and construction may be regulated by State, Territory or local government legislation. Licensees should investigate the local rules pertaining to the erection of towers and antennas before planning for a device to operate in a certain location. Obtaining a permit to operate non-standard devices. A licensee who wishes to operate standard devices under a spectrum licence (that is, equipment that conforms to mandatory the ACMA standards) does not need to apply to the ACMA for permission to do so. However, a permit will be required to supply or operate any nonstandard devices. These permits may be issued by the ACMA under s.167 of the Radiocommunications Act 1992, and will only be issued during the term of the licence. Permits to supply non-standard devices for operation under a spectrum licence may also be issued by the ACMA under s.174 of the Act.