Radiocommunications (Unacceptable Levels of Interference - 2.5 GHz Mid Band Gap) Determination 2023

This Determination organises its test around a small number of tightly specified technical concepts. Understanding those concepts is necessary to apply the instrument and to forecast the operational choices a licensee will make.

Key definitions and pivots

• 2.5 GHz mid band gap: the frequency range 2570-2620 MHz (s 5). The instrument applies only to transmitters operating under a spectrum licence that authorises operation in that band.
• Device boundary: a locus of end points computed for each degree radial from the antenna location, where a device-boundary criterion RP − MP first becomes ≤ 0, or where the radial reaches 500 increments (m = 500), each increment being 100 metres (Schedule 2 item 1). The device boundary is therefore a polar-derived contour around a transmitter out to 50 km.
• RP (radiated power): horizontally radiated power, measured in dBm EIRP per 30 kHz, for each bearing σn (Schedule 2 item 2, definition of RP). For a group of transmitters, RP is taken to be equal for each bearing and equal to the maximum horizontally radiated power of any transmitter in the group (Schedule 2 item 1(2)).
• MP (minimum protected level expression): MP = PL(lmn, Lmn) + LOP − Gr, where PL is propagation loss at the sampled point, LOP is the level of protection (fixed at −80.4 dBm/30 kHz) and Gr is the nominal receiver antenna gain including feeder loss, fixed at 18 dBi (Schedule 2 item 2 table).
• Device boundary criterion RP − MP: the test value evaluated at each sampled increment; the device boundary end point is the first point where RP − MP ≤ 0 (Schedule 2 item 1).
• Propagation loss calculations: use specific ITU-R models and parameters. If the transmitter antenna is more than 6 m above ground level, the instrument mandates use of P.525-4 (free-space attenuation) and P.526-15 (diffraction) sections specified (Schedule 2 item 3(1)(a)). If the antenna is 6 m or lower, P.525-4 and ITU-R P.2108-0 (prediction of clutter loss) are used with specified parameter constraints including a 0.08% percentage of locations and caps on loss correction (Schedule 2 item 3(1)(b), 3(4)). Path profiles must be generated by sampling DEM-3S at 100 m increments (Schedule 2 item 3(3)(a)-(b)).
• Effective antenna height and average ground height: Schedule 3 prescribes how to compute effective antenna height using DEM-3S cell heights and the antenna phase-centre elevation, with special rules to ensure a lower bound equal to the physical antenna height (Schedule 3 item 1). Average ground height at a sampled point is the mean of a 3×3 matrix of DEM-3S cells (Schedule 3 item 2).
• Measurement and statistical confidence: parameters in Schedules 2 and 3 must be estimated with at least 95% confidence that the true value will remain below the instrument’s specified requirement (s 11).

Operational implications of the concepts

• The device boundary is a function of horizontally radiated power, antenna height, terrain profile from DEM-3S and ITU-R propagation assumptions. Small changes in any of those inputs can change which radial end points fall inside or outside a licence geographic area.
• The instrument treats groups of fixed transmitters and fixed receivers as a unit for device-boundary calculations when strict sameness conditions are met (same centre frequency, emission designator, antenna type/model/manufacturer, co-located within 20 metres and same ACMA antenna identifier (s 8-9)).
• A device boundary that extends beyond the licence geographic area is, subject to narrow exceptions, an “unacceptable” level of interference (s 10(1)(b)-(2)). This places a geometric constraint on deployment: a licence authorises operation within a geographic area, and the device boundary contour must generally be contained within that area.
• The instrument establishes an explicit vertical-plane emission limit: emissions above the horizontal plane greater than 45 dBm/30 kHz EIRP are unacceptable (s 10(3)). This caps maximum vertically radiated energy regardless of horizontal compliance.

Dataset and algorithm certainty

• The instrument prescribes use of DEM-3S with a persistent identifier and requires sampling at fixed resolution (Schedule 2 item 3(3)(a)-(b), s 5 definitions of DEM-3S). The calculation rules (Vincenty’s Direct Formulae in Schedule 3 item 3) are fixed to GDA94/GRS80 parameters, removing ambiguity about geodesic calculations.

In short, the Determination turns a regulatory question , whether operation would cause unacceptable interference , into a deterministic, reproducible engineering procedure using specified dataset(s) and propagation models, a 100-m sampling resolution on 360 radials, and numerical cut-offs for power, antenna gain, and protection level.

This Determination affects a narrow set of actors and indirectly affects adjacent stakeholders who interact with spectrum-licensed deployments in the 2.5 GHz mid band gap.

Primary affected parties

• Spectrum licensees holding, or seeking to operate under, 2.5 GHz mid band gap spectrum licences (2570-2620 MHz) (s 5). The instrument governs the test the ACMA will apply when deciding whether to include details of a radiocommunications transmitter in the Register under subsection 145(4) of the Act (s 3).
• Operators and vendors who supply, install, model or certify fixed radiocommunications transmitters in that band. The Determination prescribes precise modelling steps and datasets (Schedules 2 and 3), so engineering, planning and vendor teams will need to implement those calculations to design sites that comply with the device boundary requirements.

Secondary and indirect stakeholders

• Adjacent spectrum licensees and users. The “level of protection” (LOP) is specified at −80.4 dBm/30 kHz (Schedule 2 item 2). That fixed protection threshold is what the device-boundary test seeks to protect; operators of other receivers can expect that the ACMA will treat the LOP as the baseline when adjudicating interference claims arising from 2.5 GHz mid band gap transmitters.
• ACMA. The instrument binds the ACMA to a particular engineering test when exercising its power under s 145(4) of the Act (s 3). ACMA staff responsible for Register inclusion decisions, interference assessment and site-record management will need to apply the schedule computations and check accuracy/confidence requirements (s 11, Schedule 1).
• Surveyors, geospatial data providers and modelling consultants. The instrument requires use of DEM-3S and geodetic calculations reference GDA94; those providing accurate location, elevation and propagation modelling services will be directly engaged. The instrument also imposes numerical tolerances (location measurement error <10 m, Schedule 1 item 3; 95% confidence requirement, s 11) that will require quality-assured workflows.
• Holders of existing registered transmitters. Section 12 provides transitional rules for transmitters already included in the Register before commencement; those transmitters are treated as subject to the previous (2012) Determination unless a registered change expands device-boundary distances on any sampled radial. Therefore existing registrants have a protected status until they make certain changes that increase device-boundary radius.

Who decides and who pays

• The ACMA decides whether an operation causes unacceptable interference under the prescribed test, and can refuse to include transmitter details on the Register under subsection 145(4) of the Act (see s 10 note referring to s 145(1) of the Act). The licence holder (or authorised third party) must provide the data and modelling to support registration; therefore the licence holder pays for the geospatial surveys, modelling and any mitigation measures (site modification, power reduction, antenna pattern change) necessary to bring device boundaries within licence areas.
• Where a transmitter is capable of belonging to more than one group of transmitters or receivers, the spectrum licensee or authorised third party may nominate one group for the transmitter/receiver (s 8(2), s 9(2)). This gives the licensee a degree of control over grouping choices that affect RP calculations for groups.

Operational behaviours the instrument makes more or less likely

• Site planning to confine device boundaries within licence geographic areas (s 10). Licensees will favour lower ERP or directional antennas or relocate sites to ensure the device boundary contour remains inside their licensed footprint.
• Consolidation of co‑located transmitters into a single “group” for calculation when they meet the sameness criteria (s 8). That grouping rule treats group RP as the maximum horizontally radiated power of any transmitter in the group, which may encourage co‑ordination of equipment on a tower to avoid having one site’s RP determine a larger device boundary.
• Use of the specified DEM-3S dataset and the ITU-R models in site design and regulatory submissions, because the ACMA must apply those tools for the unacceptable-interference test (Schedule 2 item 3).

Who is not directly affected

• Mobile or airborne transmitters designed for use while in motion are excluded from the “fixed transmitter” and “fixed receiver” definitions and therefore not subject to the device boundary computation steps that reference fixed devices (s 5 definitions of fixed transmitter and fixed receiver).
• The Determination does not create separate criminal penalties or administrative fines; it prescribes the engineering test the ACMA applies when deciding whether to register a transmitter, so parties expecting fines from the Determination itself will not find them in this instrument. Enforcement actions available to ACMA arise from the Act; this Determination affects how ACMA exercises its registration/refusal discretion.

In summary, the instrument affects licensees and technical advisers who must model, certify and, where necessary, modify fixed site deployments in 2570-2620 MHz to comply with the device-boundary and vertical-emission tests. It also affects ACMA operations because the agency is bound to apply the specified datasets and models in determining unacceptable interference.

The Determination sets technical obligations, prescribes the ACMA’s decision rule for registration, and confers limited procedural rights through transitional protections. These duties and rights are expressed as engineering tests and data‑handling requirements, rather than explicit behavioural prescriptions.

Duties on spectrum licensees or authorised third parties

• Ensure transmitter location and related data are recorded to the standard required for Register inclusion. The location must be given by latitude and longitude referencing GDA94 and the measurement error must be less than 10 metres (Schedule 1 items 1-3).
• Provide sufficient data and modelling to enable the ACMA to calculate a device boundary for each fixed transmitter or group of transmitters according to Schedule 2, including:
  • the horizontally radiated power (RP) in dBm EIRP per 30 kHz for each bearing σn (Schedule 2 item 2);
  • antenna height and phase-centre information necessary to compute effective antenna height per Schedule 3 item 1;
  • emission designator information determined according to Radio Regulations methods (s 7).
• Meet the instrument’s accuracy/confidence requirement: Unless otherwise specified, values in Schedules 2 and 3 must be estimated with a level of confidence of at least 95% that the true value will remain below the instrument’s requirement (s 11). That obligation implies modelling with probabilistic error bounds or measurement protocols sufficient to support a 95% confidence statement.
• For groups of transmitters and receivers, satisfy the sameness and co‑location conditions if electing to treat multiple transmitters/receivers as a group (s 8(1)(a)-(e), s 9(1)(a)-(d)). A transmitter must not belong to more than one group (s 8(2), s 9(2)); where capable, the licensee or authorised third party may nominate the group.
• Ensure emissions above the horizontal plane do not exceed 45 dBm/30 kHz EIRP (s 10(3)).

ACMA duties/decision rule (as constrained by the instrument)

• Apply the instrument’s technical test when deciding whether operation of a transmitter under a 2.5 GHz mid band gap spectrum licence would cause unacceptable interference for the purposes of subsection 145(4) of the Act (s 3, s 10). The instrument binds the ACMA to use the specified dataset, sampling resolution and ITU-R models in calculating propagation loss and device boundaries (Schedule 2 item 3, Schedule 3).
• Refuse to include in the Register details of a transmitter if the ACMA is satisfied that operation could cause an unacceptable level of interference, as defined in s 10; the instrument informs that decision-making process (note to s 10 referencing subsection 145(1) of the Act).

Rights and transitional protections

• Existing transmitters included in the Register before commencement are protected under s 12(2): for those transmitters, a level of interference is unacceptable only if it would have been unacceptable under the 2012 Determination as in force at the time the transmitter was included in the Register (s 12(2)). That preserves the status quo for registered transmitters, subject to changes recorded in the Register that expand device-boundary distances on any radial (s 12(3)).
• If a registered transmitter’s details are changed and the new device boundary on each radial is equal to or less than the old device boundary on that radial, then even if the post-change situation would otherwise be unacceptable, subsection 12(3) deems the level of interference immediately after the change not unacceptable because of the relevant change (s 12(3)). This affords a limited procedural right when changes reduce device-boundary extent.

Constraints rather than direct commands

• The Determination does not itself impose licence conditions such as mandatory power-reduction steps or site alterations; instead, it defines when ACMA may refuse registration because a proposed or existing operation would cause unacceptable interference (s 10 read with the Act reference in s 3 note). The practical duty placed on licensees is therefore to provide compliant modelling and to modify deployment as necessary to gain Register inclusion.

Data and modelling obligations

• Use DEM-3S (cited with persistent identifier in s 5) and apply Vincenty’s Direct Formulae with GRS80 parameters for geodesic calculations (Schedule 3 item 3). The instrument thus creates an obligation to use specific datasets and algorithms; failure to adopt the specified models would risk the ACMA treating an application as non‑compliant or computing a device boundary unfavourably.
• Apply ITU-R propagation recommendations as directed: P.525-4 and P.526-15 for antennas >6 m, and P.525-4 and P.2108-0 for antennas ≤6 m, with stated parameter constraints (Schedule 2 item 3).

In sum, the Determination creates a regime of technical duties on licensees to generate and provide particularised, confidence-bounded modelling outputs; it binds ACMA to apply the same technical rules when exercising registration/refusal powers; and it grants limited transitional protections to existing register entries.

The Determination itself is an instrument made under subsection 145(4) of the Radiocommunications Act 1992 and primarily defines a technical test. It does not, on its face, create new criminal offences or prescribe monetary penalties. Instead, its enforcement effect operates through the Act’s existing administrative powers and the Register inclusion process.

How enforcement works under the Determination

• Registration refusal: The main enforcement mechanism triggered by this Determination is the ACMA’s ability to refuse to include details of a radiocommunications transmitter in the Register if the ACMA is satisfied that operation could cause an unacceptable level of interference (s 10 and the note referencing subsection 145(1) of the Act). The instrument defines “unacceptable” for that purpose and therefore prescribes the test ACMA must apply when considering Register inclusion or rejection (s 3, s 10).
• De facto control via Register: Inclusion in the Register is often a prerequisite for lawful operation under a spectrum licence (the Act contains provisions about registration; see the note in s 8 and s 9 referring to section 144 of the Act for Register entries). If ACMA refuses to include a transmitter’s details because it would cause unacceptable interference under the instrument’s test, the licensee cannot lawfully operate the transmitter, or at least cannot rely on Register inclusion. The Determination thus functions as a gatekeeper through the registration process rather than by prescribing a new penalty.

Indirect enforcement via the Act

• The Determination references s 145 of the Act as its authority (s 3). Enforcement mechanisms such as directions, notices, fines or offences would arise under the Act and associated regulations; this Determination does not itself enumerate those downstream enforcement options. Practitioners should therefore consult the Act for the full suite of enforcement powers ACMA may employ beyond the registration decision the Determination governs.

Practical enforcement implications for operators

• Risk of non‑registration: The real, immediate regulatory cost of non‑compliance with the Determination’s modelling rules is refusal of Register inclusion. Register refusal will prevent lawful operation where registration is required under the Act, and may trigger consequential compliance actions under the Act if the party operates without registration.
• Data and modelling scrutiny: Because the instrument prescribes a specific dataset (DEM-3S) and defined ITU-R methods, ACMA can insist on reproducible modelling steps. A submission that relies on alternative datasets or omitted the required sampling/resolution risks being rejected on technical grounds. The 95% confidence requirement (s 11) creates a standard ACMA can use to challenge modelling that lacks probabilistic justification, which in practice may lead to requests for resubmission or refusal.
• Transitional status and change reporting: For transmitters included in the Register before commencement, s 12 protects existing configurations in many cases. However, if a registered change is recorded that would increase device-boundary distances on any radial, the transmitter may lose the transitional protection and be subject to the new instrument’s standards immediately after the change is recorded (s 12(3)). The act of changing registered details therefore carries enforcement risk insofar as it triggers reassessment under the 2023 Determination.

No express infringement notices or pecuniary penalties in the instrument

• The Determination does not itself prescribe infringement fines, civil pecuniary penalties, or criminal penalties. Any such enforcement would derive from the Act’s general enforcement framework and the ACMA’s existing powers. This instrument supplies the substantive technical standard ACMA will apply within that statutory enforcement architecture.

In summary, enforcement operates through ACMA’s registration discretion and the Act’s broader enforcement mechanisms. The Determination defines technical thresholds and computational procedures that the ACMA will apply when deciding whether to refuse registration or otherwise act under the Act, but it does not itself specify separate statutory penalties.

This Determination is made under subsection 145(4) of the Radiocommunications Act 1992 and therefore functions as a legislative instrument that plugs into the Act’s registration and interference framework. Its interaction with other laws is principally through reference, incorporation, and operational dependency.

Primary legal relationships

• Radiocommunications Act 1992: The instrument’s authority is subsection 145(4) of the Act (s 3). The instrument operationalises the Act’s registration provisions by defining unacceptable interference for the 2.5 GHz mid band gap. The notes in the Determination explicitly refer to the Act’s section 145(1) (s 10 note) and section 144 (s 8 and s 9 notes) as relevant: the Act specifies what must be included in the Register and the conditions on refusing registration. Therefore any enforcement or refusal under this Determination will proceed under the Act’s powers and processes.
• Radio Regulations and ITU-R Recommendations: The Determination incorporates international technical methods by reference. Section 7 requires emission designators to be determined using the Radio Regulations, and multiple items of the Schedules require use of ITU-R Recommendations P.525-4, P.526-15 and P.2108-0 for propagation and clutter-loss modelling (s 7, Schedule 2 item 3). The instrument thus integrates international radiocommunications technical rules into the domestic legal test. The Radio Regulations and ITU-R Recommendations are not themselves regulations under the Act; they are technical sources the instrument instructs ACMA and licensees to use (s 5 notes and s 7).
• Geodetic and dataset references (GDA94, DEM-3S): The Determination fixes the geodetic datum (GDA94) for location references (s 5 definitions, Schedule 3 item 3 note) and mandates the DEM-3S dataset with a persistent identifier (s 5 definitions). This creates an interaction with laws and instruments that govern geodetic data, surveying standards, and datasets; operators must ensure their survey and modelling practices conform to those references.
• Acts Interpretation Act 1901 and Legislation Act 2003: Section 6 clarifies that references to other legislative instruments are references to those instruments as in force from time to time, and notes the application of the Acts Interpretation Act 1901 and Legislation Act 2003 (s 6 and its notes). This confirms ordinary statutory interpretation rules apply: references are dynamic unless the Determination specifies otherwise.

Specific interplays to note

• Register content under the Act: The Determination refers to section 144 of the Act for information ACMA must include in the Register about spectrum licences and devices (notes to s 8 and s 9). That means the technical calculations required here will feed into the statutory Register content mandated by the Act. If the Register requires particular fields (e.g. site identifiers, antenna IDs), the Determination’s requirement that a transmitter be in a group only if the antenna ACMA identification is the same (s 8(1)(e), s 9(1)(d)) ties the grouping possibility to statutory Register data.
• Transitional relationship with the 2012 Determination: Section 4 repeals the 2012 Determination; section 12 implements a transitional rule preserving the previous test for transmitters included in the Register before the 2023 Determination’s commencement, unless and until a registered change expands device-boundary distances. That creates a time‑sequenced legal interaction: older entries continue to be governed by the 2012 rule in many cases, but later changes can cause the 2023 standard to apply.
• Maritime jurisdiction and HCIS exclusions: Section 10(2)(b)(ii)-(iii) excludes certain radials from being treated as unacceptable where the radial “does not cross over land outside the geographic area of the licence that is permanently above the Australian territorial sea baseline” and does not enter certain HCIS identifiers (IW3E, IW3I, IW3M, IW6A, IW6E, KX9, LX7, LX8, LX9). Those provisions interact with maritime boundary law (the Seas and Submerged Lands Act 1973 baseline definition is incorporated by reference in the s 5 definition of “Australian territorial sea baseline”) and with the Australian Spectrum Map Grid/HCIS spatial framework. Practitioners must therefore combine geodesic and maritime baseline constraints with ACMA’s HCIS mapping when assessing edge-of-licence device-boundary compliance.

Limits of this instrument in the legal web

• It does not replace the Act’s enforcement powers. Any direction, notice, penalty or criminal sanction available for interference under the Act remains governed by the Act and regulations. This Determination supplies a technical standard for one statutory decision (refusal to include in the Register under s 145(4)), but does not alone expand or limit the statutory enforcement powers in other parts of the Act.
• It does not create rights against third parties beyond the Act. The Determination sets the ACMA’s test; it does not itself create private causes of action or change contractual rights between licensees. Affected parties may rely on the ACMA’s application or non-application of the test in regulatory or administrative appeals under the Act, but those avenues are governed by the Act and administrative law principles, not by this instrument’s text.

Overall, the Determination is tightly integrated with the Act’s Register and interference regime, imports specific international technical methods, and references geodetic/dataset standards and maritime baseline concepts. Its practical legal effects will therefore be felt through ACMA’s application of the Act and the Register regime.

The Determination itself records one immediate amendment event and establishes how changes to relevant instruments and references are to be treated going forward.

Primary amendment event

• Repeal of the 2012 Determination: Item 4 of the instrument expressly repeals the Radiocommunications (Unacceptable Levels of Interference - 2.5 GHz Mid-band Gap) Determination 2012 [F2012L02553] (s 4). The 2012 Determination therefore ceases to operate on and after the commencement of this instrument. The 2023 Determination replaces it as the operative technical standard for ACMA decisions about unacceptable interference in the 2.5 GHz mid band gap.

Commencement and transitional rule

• Commencement: The instrument commences at the start of the day after it is registered on the Federal Register of Legislation (s 2). Immediately on commencement, the 2012 Determination is repealed and the 2023 Determination takes effect, subject to the transitional arrangements in s 12.
• Transitional protection for pre‑commencement register entries: Section 12 sets a targeted transitional rule. A radiocommunications transmitter included in the Register for a 2.5 GHz mid band gap licence before this instrument commenced remains subject to the prior (2012) test for unacceptable interference (s 12(2)). However, s 12(3) creates an exception where a registered change occurs after commencement: if a registered change is recorded and the new device boundary distances on each radial are equal to or less than the old device boundary on each radial, then a level of interference that would otherwise be unacceptable immediately after the change is not unacceptable because of that registered change (s 12(3)). Thus registered entries are protected against immediate reclassification under the new test unless a change is registered that increases device-boundary extent.

References and updates

• Rolling references to other instruments: Section 6 provides that references to other legislative instruments are to those instruments as in force from time to time (s 6(a)). It also provides that references to other instruments or writings are references to those as in force or existence from time to time (s 6(b)). This means incorporated technical sources like ITU-R Recommendations or the Radio Regulations, if amended and if the Determination has not been specifically updated, will be read as dynamic references unless a contrary intention appears. The notes to s 5 and s 7 identify where those external materials can be found, but do not freeze their versions unless the Determination specifies a version (some items do specify versions, e.g. P.526-15, P.525-4, P.2108-0).

Practical consequences of the amendment history

• Immediate legal substitution of standards: After commencement, ACMA must apply the 2023 Determination’s tests for new Register inclusion decisions and for changes that remove transitional protection (s 12). Practitioners should therefore use the 2023 computational methods for new site designs and for any proposed registered changes that might affect device-boundary distances.
• Need to track external recommendation versions: The Determination cites specific versions of ITU-R Recommendations (e.g. Recommendation ITU-R P.526-15, P.525-4, P.2108-0) in the schedules (Schedule 2 item 3). Because s 6 allows references to instruments as in force from time to time, any later international amendments could change the modelling methods ACMA is authorised to use unless the Determination is amended to fix a version. Practitioners should monitor ACMA guidance and the Federal Register entries.

No internal amendment history provided beyond repeal

• The instrument does not contain a history of prior amendments to the 2012 Determination; it simply repeals the 2012 Determination and establishes the 2023 text. To see prior amendment history, one must consult the 2012 Determination and any subsequent amending instruments recorded on the Federal Register of Legislation.

In short, the 2023 Determination replaces the 2012 Determination, commences upon registration, and provides a limited transitional protection for existing registered transmitters that is conditional on whether later registered changes expand device-boundary distances.

The text of the Determination does not record any litigation history. It is a legislative instrument that prescribes a technical test for the ACMA’s exercise of statutory powers under the Radiocommunications Act 1992. No cases, judicial decisions, appeals to tribunals or precedent materials are cited or incorporated in the instrument itself.

What to expect given the instrument’s role

• Potential administrative law review: Because the Determination governs ACMA’s application of subsection 145(4) of the Act (s 3) and therefore affects registration decisions, administrative law challenges could arise from applicants or licensees dissatisfied with ACMA’s application of the prescribed test. Any judicial review or merits review proceedings would proceed under the Act and judicial review principles; the Determination’s detailed procedural and modelling rules would be central to any such dispute because they fix the standard ACMA must apply.
• Technical disputes over modelling and data: If an operator’s modelling (using DEM-3S, ITU-R methods, etc.) is rejected by ACMA as insufficiently accurate or not meeting the 95% confidence requirement (s 11), disputes are likely to focus on modelling assumptions, measurement error, dataset handling (e.g. 3×3 DEM cell averaging, special modulus rules for cell selection in Schedule 3 item 2), and the application of ITU-R methods. Litigation or administrative appeals, if they occur, will be technical questions of fact and method constrained by the instrument’s prescriptions.
• Transitional disputes: Section 12’s transitional rule could generate disputes where ACMA determines a registered change expands device-boundary distances on one or more radials and therefore withdraws transitional protection. Such disagreements would hinge on the precise device-boundary computations under Schedule 2 and the timing/recording of the registered change.

Absence of reported cases in the instrument

• Practitioners should not infer from the absence of litigation references that the Determination is immune to challenge; rather, any litigation or review will be external to the instrument and would be found in court or tribunal records and legal databases, not in the instrument text itself. The instrument establishes the technical yardstick that would be central to any factual disputes in litigation.

In sum, no litigation history is recorded in the instrument. If disputes arise, they will be administered under the Act and decided with reference to the deterministic methods and datasets the Determination prescribes.

This Determination contains multiple technical details and discrete numerical rules that create traps for the unwary. The following points are concrete operational and legal “gotchas” drawn directly from the instrument text.

1. Device boundary is sampled on every degree out to 50 km at 100 m resolution

• Schedule 2 item 1 requires calculating the device boundary criterion at each m×100 metre increment for m = 1..500 and for each integer degree n = 0..359, and the device boundary is the first increment with RP − MP ≤ 0 or m = 500. That means the device boundary is discretised at 100 m resolution and can change abruptly when RP, antenna height or terrain inputs change; it is not a continuous radiometric contour. Practitioners must ensure their models implement exactly this sampling and stopping rule.

2. The LOP and receiver gain are fixed, not negotiable

• The LOP is fixed at −80.4 dBm per 30 kHz and Gr (nominal receiver antenna gain including feeder loss) is set at 18 dBi (Schedule 2 item 2). Applicants cannot propose alternative protection levels or receiver gains to shrink the device boundary for regulatory purposes; the ACMA will apply these fixed parameters.

3. Emissions above the horizontal plane cap is strict

• Section 10(3) makes any emission above the horizontal plane greater than 45 dBm/30 kHz EIRP “unacceptable”. This is an absolute numerical cap applicable regardless of whether horizontal device boundaries would otherwise comply. Vertical radiation control must therefore be modelled and, if necessary, physically constrained.

4. Odd rules in the P.2108-0 application may surprise modelers

• Schedule 2 item 3(4) directs that when using P.2108-0: (a) the percentage of locations is 0.08% with correction applied at only one end; (b) if loss calculated is less than 0 dB, take it as 0 dB; and (c) if loss calculated is greater than 8 dB, take it as 0 dB. The capping of both negative and large positive loss values to 0 dB is a highly specific rule that departs from naive expectations that higher clutter loss reduces received power. Model outputs must follow these caps where P.2108-0 applies.

5. DEM-3S 3×3 averaging and modulus rules alter local terrain

• Schedule 3 item 2 sets the average ground height at a sampled increment as the average of the 3×3 matrix of DEM-3S cells. But there is a special exception: if the seconds component of the sample coordinate plus 1.5 has modulus zero when divided by 3, then use the adjacent DEM-3S cell with the minimum height instead (Schedule 3 item 2(2)). Those discrete, arithmetic-selection rules can cause a single increment to use an adjacent cell’s minimum height rather than the central average; implement this rule exactly to avoid inconsistencies.

6. Location measurement error capped at <10 m

• Schedule 1 item 3 requires location measurement error to be less than 10 metres. If an operator’s surveyed antenna location does not meet that tolerance, the device-boundary computation may be invalid or not compliant with the Determination’s preconditions.

7. 95% confidence requirement is not optional

• Section 11 requires that values in Schedules 2 and 3 be estimated with at least 95% confidence that the true value remains below the instrument’s requirement. This is a probabilistic statement, not just a point-estimate requirement. Model submissions should include uncertainty quantification, confidence intervals or measurement error analysis to demonstrate the 95% confidence level.

8. Grouping rules can magnify device boundary

• If multiple fixed transmitters meet the strict grouping criteria in s 8 (same centre frequency, emission designator, antenna model, co‑located within 20 metres, same ACMA antenna ID), the group’s RP is the maximum horizontally radiated power of any transmitter in the group (Schedule 2 item 1(2)). That means a high‑power transmitter on a shared structure can determine the group device boundary and thereby enlarge the contour used to assess unacceptable interference.

9. Transitional protection can disappear upon recorded changes

• Section 12 protects pre‑commencement registered transmitters under the 2012 test, but if a registered change results in a new device boundary that is greater on any radial, transitional protection may be lost. Changes recorded in the Register therefore carry the risk of subjecting the transmitter immediately to the new Determination.

10. Failure to calculate a device boundary makes the interference “unacceptable”

• Section 10(1)(c) makes it an explicit ground for unacceptable interference if the device boundary “cannot be calculated in accordance with item 1 of Schedule 2.” Practical causes of inability to calculate could include missing DEM-3S data, location measurement errors exceeding tolerances, or incomplete transmitter specification (e.g. unknown emission designator). Ensuring complete, accurate inputs is therefore a compliance imperative.

11. HCIS and maritime baseline exceptions are narrow and location-specific

• The exception in s 10(2) that allows parts of the device boundary to lie outside a licence’s geographic area applies only when the outside part is connected to a radial mentioned in item 1 of Schedule 2 and that radial does not cross land outside the geographic area that is permanently above the Australian territorial sea baseline, and does not cross the listed HCIS identifiers (IW3E, IW3I, IW3M, IW6A, IW6E, KX9, LX7, LX8, LX9). Those HCIS exclusions are explicitly localised (note: IW codes near Adelaide; KX and LX describe Bass Strait). Practitioners cannot assume a general permissive rule at coasts; they must test each radial for these exact criteria.

12. Fixed receiver antenna gain is nominal and not modelled per site

• The Determination uses a nominal receiver antenna gain (including feeder loss) of 18 dBi (Schedule 2 item 2). This reduces the ability for a licensee to argue for a higher or lower target receiver gain based on local receiver installations.

These “gotchas” are not legal ivory-tower points; each one translates into a specific modelling, survey, or operational task that can determine whether an ACMA registration application is accepted or refused.

Compliance with this Determination requires implementing the instrument’s algorithmic steps precisely, documenting inputs and uncertainty, and aligning site design choices with the device-boundary and vertical-emission limits. Below are concrete, sequenced steps that follow directly from the Determination’s text and schedules.

Step A , Confirm applicability and gather baseline documents

• Confirm the transmitter will operate under a 2.5 GHz mid band gap spectrum licence (2570-2620 MHz as defined in s 5). If so, the Determination applies.
• Obtain the 2023 Determination text, the referenced version(s) of ITU-R Recommendations (P.525-4, P.526-15, P.2108-0) as cited in Schedule 2 item 3, and the DEM-3S dataset via the provided persistent identifier (s 5 definitions). Use the specified versions named in the instrument.

Step B , Site survey and location measurement

• Determine the phase-centre coordinates (latitude and longitude referenced to GDA94) of the antenna. The location for a single transmitter is the phase centre; for a group it is the centre point between phase centres (Schedule 1 items 1-2).
• Ensure survey measurement error is less than 10 metres (Schedule 1 item 3). Record survey method and uncertainty metrics to demonstrate compliance.

Step C , Determine emission designator and antenna identifiers

• Determine the emission designator using the Radio Regulations’ methods as required by s 7. Treat “necessary bandwidth” references in the Radio Regulations as “occupied bandwidth”.
• Record ACMA antenna identification numbers; groups require the same ACMA antenna ID to be treated as a group (s 8(1)(e), s 9(1)(d)).

Step D , Compute effective antenna height and average ground heights using DEM-3S

• For each bearing σn (0-359 degrees) and for each increment m = 1..500:
  • Compute the latitude and longitude of the increment point using Vincenty’s Direct Formulae with GRS80 parameters (Schedule 3 item 3). Implement the iterative solution until the change in φ is less than 10^-12 as specified.
  • Identify the DEM-3S cell for that coordinate and derive the average ground height by taking the 3×3 DEM-3S cell matrix average (Schedule 3 item 2). Apply the special modulus rule: if seconds component of the coordinate plus 1.5 has modulus zero when divided by 3, use the adjacent DEM cell with minimum height instead (Schedule 3 item 2(2)).
  • Compute hs as DEM-3S cell height of the transmitter location plus hgt (physical antenna phase centre height) per Schedule 3 item 1(b). If the special seconds-component condition at the transmitter location applies, hs uses the maximum height of adjacent DEM-3S cells as specified (Schedule 3 item 1(3)). Compute the effective antenna height h_em as hs minus the average ground height at each increment, but apply the lower bound equal to hgt where h_em would otherwise be less than hgt (Schedule 3 item 1(d)-(e)).

Step E , Choose propagation model per antenna height and sample path profiles

• If the antenna is more than 6 m above ground level, use the method and parameters in section 2.2 of ITU-R P.525-4 and section 4.5.2 of ITU-R P.526-15 (Schedule 2 item 3(1)(a)).
• If the antenna is 6 m or lower, use section 2.2 of P.525-4 and section 3 of P.2108-0 with the specified adjustments: percentage of locations 0.08% and correction applied at only one end, and apply the capping rules (Schedule 2 item 3(1)(b) and 3(4)).
• Build the path profile by sampling DEM-3S at 100 m increments (Schedule 2 item 3(3)(a)-(b)). Use the transmitter effective height and the receiver nominal height of 5 m above ground level for P.526-15 as required (Schedule 2 item 3(2)(a)-(c)).

Step F , Calculate propagation loss PL(lmn, Lmn)

• For each sampled increment, apply the prescribed ITU-R methods and parameters to compute PL(lmn, Lmn) following Schedule 2 item 3. Document all model assumptions and parameters used.

Step G , Compute MP and RP and evaluate device-boundary criterion

• At each increment compute MP = PL(lmn, Lmn) + LOP − Gr, where LOP is −80.4 dBm/30 kHz and Gr is 18 dBi (Schedule 2 item 2).
• Determine RP for each bearing as the horizontally radiated power in dBm EIRP per 30 kHz for that bearing (Schedule 2 item 2). For groups, use the maximum horizontally radiated power among group members for all bearings (Schedule 2 item 1(2)).
• Evaluate RP − MP at each increment along each radial. The first increment where RP − MP ≤ 0 is the radial end point and thereby the device boundary for that radial (Schedule 2 item 1). If no increment satisfies RP − MP ≤ 0 up to m = 500, the end point is at m = 500 (50 km).

Step H , Check geographic-area containment and vertical emissions

• Map the device boundary against the spectrum licence’s geographic area. If any part of the device boundary lies outside the geographic area, the operation is unacceptable except where the narrow exceptions of s 10(2) apply (the outside part must be connected to a radial mentioned in Schedule 2 item 1 and the radial must not cross land outside the geographic area permanently above the Australian territorial sea baseline and must not cross the listed HCIS identifiers IW3E, IW3I, IW3M, IW6A, IW6E, KX9, LX7, LX8, LX9) (s 10(1)(b), s 10(2)). Carefully test each outside-of-area radial against these criteria.
• Check that emissions above the horizontal plane do not exceed 45 dBm/30 kHz EIRP (s 10(3)). If they do, the transmitter is unacceptable regardless of device boundary containment.

Step I , Demonstrate accuracy and 95% confidence

• Prepare documentation showing how the parameters in Schedules 2 and 3 were estimated with at least 95% confidence that the true value will remain below the instrument’s requirement (s 11). This may include uncertainty quantification for measurement error, Monte Carlo modelling of propagation parameters, or statistical error bounds on DEM-3S cell heights and antenna phase-centre elevation.
• Provide complete modelling traceability: DEM-3S cell IDs for every sampled increment, propagation model input files, Vincenty iteration logs, and assumptions regarding antenna pattern and horizontally radiated power per bearing.

Step J , Register and manage changes carefully

• For a new transmitter, submit Register inclusion material with the above computations. For existing registered transmitters, be aware that s 12 preserves the pre-commencement test for the current registered configuration; however, any registered change that increases device-boundary distances on any radial can subject the transmitter to the new Determination immediately upon registration of the change (s 12(3)). If a change reduces device-boundary extents on all radials, s 12(3) provides a deemed protection for the immediate post-change state.
• If a transmitter can belong to more than one group, the licence holder or authorised third party may nominate one group for that transmitter (s 8(2), s 9(2)). Choose nominations strategically because group RP may be determined by the highest-power co-located transmitter.

Practical mitigations if your computation produces an unacceptable outcome

• Reduce horizontally radiated power (RP) per bearing through power reduction or tighter antenna patterns.
• Change antenna height or relocate the antenna so that effective antenna height and terrain profile alter propagation loss favourably.
• Re-engineer antenna pattern to limit emissions in bearings that project device boundaries beyond the licence area.
• Re-assess grouping: if multiple transmitters are grouped because of co-location and sameness criteria, consider whether reconfiguration avoids group treatment that enlarges the device boundary.
• If emissions above the horizontal plane exceed 45 dBm/30 kHz EIRP, adjust antenna downtilt or physically limit vertical radiation.

Record-keeping and audit trail

• Maintain the DEM-3S dataset snapshot used, model inputs and outputs, survey certificates demonstrating location measurement error <10 m, emission designator calculations per Radio Regulations, and a clear statement that the prescribed ITU-R methods and parameters were followed. The Determination’s prescriptive nature means ACMA will expect reproducible, auditable submissions.

By implementing the deterministic steps specified in Schedules 1-3, using DEM-3S and the stated ITU-R methods, demonstrating 95% confidence in critical parameters, and ensuring device boundary containment and vertical emission limits, an operator can prepare a register submission consistent with the Determination’s requirements.