- 1 -
frequency assignment requirements
for the
point to multipoint service
in the
400 MHz AND 900 MHz BANDS
1
RADIOCOMMUNICATIONS ASSIGNMENT AND LICENSING INSTRUCTIONS
DISCLAIMER
The Australian Communications and Media Authority (ACMA) advise that these instructions reflect the current policies of the ACMA.
Prospective applicants for licences should take all necessary steps to ensure that they have access to appropriate technical and other specialist advice independently of ACMA concerning their applications, the operation of radiocommunications equipment and services, and any other matters relevant to the operation of transmitters and services under the licences in question.
The policies of ACMA and the laws of the Commonwealth may change from time to time, and prospective licensees should ensure that they have informed themselves of the current policies of ACMA and of any relevant legislation (including subordinate instruments). Prospective applicants for licences should not rely on statements made in these instructions about the policies that may be followed by other government authorities or entities, nor about the effect of legislation. These instructions are not a substitute for independent advice (legal or otherwise) tailored to the circumstances of individual applicants.
Radiocommunications Assignment and Licensing Instructions are subject to periodic review and are amended as ACMA considers necessary. To keep abreast of developments, it is important that users ensure that they are in possession of the latest edition.
No liability is or will be accepted by the Minister or the Department of Communications, ACMA, the Commonwealth of Australia, or its officers, servants or agents for any loss suffered, whether arising directly or indirectly, due to reliance on the accuracy or contents of these instructions.
Suggestions for improvements to Radiocommunications Assignment and Licensing Instructions may be addressed to The Manager, Spectrum Engineering, ACMA at PO Box 78, Belconnen, ACT, 2616, or by e-mail to . It would be appreciated if notification to ACMA of any inaccuracy or ambiguity found be made without delay in order that the matter may be investigated and appropriate action taken.
Amendment History
Date / CommentsNovember 1999 / Initial release
October 2003 / Tables B1 and B2 amended to add missing channels
September 2012 / Amendments to align with 400 MHz changes
January 2015 / Updated to include additional spectrum for PMP two-frequency services, as per the update to MS22.
FX 161January 2015
1
Table of Contents
Frequency Assignment Requirements for the Point to Multipoint Service in the 400 MHz and 900 MHz Bands....
1.0Purpose......
2.0Service Description......
3.0Service Model......
4.0Frequency Assignment Policy......
4.1Spectrum and Channelling Arrangements......
4.2Assignment Strategy......
4.3Supplementary Transmitters......
5.0Recommended Frequency Coordination Procedure......
5.1Site Selection......
5.2Frequency Selection......
5.3 Intermodulation Checks......
5.3.1 Introduction......
5.3.3 Performance of Intermodulation Checks......
5.4Use of Land Mobile Frequencies for PMP Services......
5.5Local Environment......
RALI Authorisation......
Bibliography......
Annex A - Unwanted Emission Limits......
A1. 12.5 kHz PMP Systems......
A2. 25 kHz PMP Systems......
Annex B - Channelling Arrangements for the Point to Multipoint Service in the 400 MHz and 900 MHz Bands....
B1. 400 MHz Band......
B2. 900 MHz Band......
B3. 25 kHz Channels......
Annex C - Intermodulation Checks......
C1. Cull Limits Applicable to Intermodulation Checks......
C2. Frequency Offset from Victim Receiver Within Which an Intermodulation ‘Hit’ is Deemed to Occur......
C3. Expressions for Evaluating Intermodulation Interference......
C4. Parameter Values Applicable to Intermodulation Checks......
FX 161January 2015
1
Frequency Assignment Requirements for the Point to Multipoint Service in the 400 MHz and 900 MHz Bands
1.0Purpose
The purpose of this Radiocommunications Assignment and Licensing Instruction (RALI) is to provide instruction on frequency assignment policy and coordination procedures for radiocommunication systems operating in the two frequency Fixed Point to Multipoint (PMP) service in the 400 MHz and 900MHz bands.
The information in this document reflects the current policy of the Australian Communications and Media Authority (ACMA) in relation to frequency assignment requirements for the PMP service in the 400 MHz and 900 MHz bands. In making decisions, ACMA frequency assigners and Accredited Persons should take all relevant factors into account and decide each case on its merits. For clarification of any matter falling within the scope of this RALI, or if an issue related to this document appears to fall outside the enunciated policy, consult the Manager, Spectrum EngineeringSection[1].
2.0Service Description
The two frequency PMP service is typically a digital or analogue radiocommunication system in which a single central master station communicates with a number of outlying remote fixed stations. The use of this service is for data transmission; typical applications include telemetry, supervisory control and data acquisition (SCADA) systems, computer networking and alarm systems.
The master station may also be wired as a repeater, with outlying remote control stations (RCSs) operating in the remote frequency configuration and communicating with remote stations via the master station. In this configuration, full duplex operation requires a separately assigned link (operating in the fixed (point to point) service) between the RCSs and the master station.
If necessary, supplementary stations working in either real time (simulcast) or sequential (store and forward) modes may be used to improve coverage within the service area. In the simulcast case, the master station may be linked to a supplementary station via a remote station configured as a repeater. In the store and forward configuration, the supplementary station receives a data packet direct from the master station, checks it for validity, and re-transmits it later on the same frequency.
From an interference management perspective, a two frequency PMP system is characterised by:
- a central master station at a high site;
- a number of remote stations - distributed randomly throughout the service area;
- one or more RCSs that control the master station;
- no direct communication between remote stations;
- full or half duplex operation; and
- data throughput in the range 1.2 to 9.6 kbps or greater.
3.0Service Model
The purpose of the service model is to define a set of characteristics for the PMP service which will result in a specified (“target”) grade of service for PMP systems. The target grade of service (TGS) is defined as a 10 dB signal to noise ratio (SNR) at the receiver input for an output bit error rate (BER) of 10-3. The service model is designed to achieve the TGS for receivers at 90% of locations within the service area.
Figure 1 - PMP Service Model
Key features of the service model are -
- Transmitter power requirements:
- the maximum station EIRP(considering transmitter power, cable loss, antenna gain) for remote and supplementary stations shall be 20 W;
- the maximum station EIRP (considering transmitter power, cable loss, antenna gain) for masterstations shall be 40 W.
- Minimumantenna performance characteristicsfor an RCS:
- in the 400 MHz band: directional antenna with a mid-band gain of 13 dBi, minimum front-to-back ratio of 16 dB and a maximum beam width (in E-plane) of 36 (e.g. a 9 element Yagi);
- in the 900 MHz band: directional antenna with a mid-band gain of 16dBi, minimum front-to-back ratio of 17 dB and a maximum beam width (in E-plane) of 30 (e.g. a 15 element Yagi).
- For a master station the antenna shall be a vertically polarised antenna with a maximum gain of 8.2 dBi. Use of a directional antenna is permitted (maximum gain 8.2 dBi).
- For a remote station use of directional antennas is encouraged but not mandatory, e.g. typical antennas used :
- in the 400 MHz band directional antenna with a mid-band gain of 13dBi, minimum front-to-back ratio of 16 dB and a maximum beam width (in E-plane) of 36 (e.g. a 9 element Yagi);
- in the 900 MHz band: directional antenna with a mid-band gain of 16dBi, minimum front-to-back ratio of 17 dB and a maximum beam width (in E-plane) of 30 (e.g. a 15 element Yagi).
- In both bands radiated power 180 degrees from the direction of the remote station to the base shall not exceed 5 Watts, i.e. if an omnidirectional antenna is used on a remote, the EIRP shall not exceed 5 Watts.
- The transmit power of remote stations in the frequency ranges 451.5 – 452.5 MHz and 853.5 – 854 MHz is limited to 5 W and in all other parts of the bands to 1 W, by the Radiocommunications Licence Conditions (Fixed Licence) Determination 1997[2].
- Typical master station antenna height of 200m above surrounding terrain.
- Typical remote station antenna height of 5 m above surrounding terrain.
- Specific requirements for RCSs to minimise their potential for causing intermodulation interference in areas having a relatively high concentration of transmitters and receivers. The model presumes the following requirements for RCSs located in central business districts:
- a 20 dB in line attenuator[3] fitted between the transmitter output and the antenna;
- antenna height limited to 30 m.
- Unwanted emission limits for transmitters are mandated in Annex A.
- Frequency coordination is performed for the master station only (interference protection for remote stations, supplementary stations and RCSs is intrinsic to the service model).
- A service area radius of 30 km. All stations must be contained within the service area.
- A co-channel minimum re-use distance of 100 km between master stations.
- Supplementary stations have no re-use distance requirements, they are included to improve the service reliability within, but not outside, the service area.
- A maximum necessary bandwidth of 12.5 kHz (or 25 kHz if two contiguous channels are assigned).
4.0Frequency Assignment Policy
Successful management of interference in the PMP service requires that all stations operating in the service (master, remote, RCS) comply with the technical constraints in this RALI.
Frequency assignment must take into consideration both inter-service and intra-service requirements consistent with the assignment philosophy promulgated in RALI MS 22.
Inter-service coordination of the PMP service with other radiocommunications services is not addressed in this document. This may be addressed, in some cases, by ITU-R Recommendations. However, because of the diversity and complexity of sharing situations which may arise, it is not possible to provide rigorous and explicit procedures covering all inter-service coordination requirements. In these cases, coordination should be performed in accordance with good engineering practice based on fundamental interference mitigation principles.
Intra-service requirements form an essential element of the service model upon which frequency assignment requirements are based, and are detailed in the following paragraphs. The intraservice frequency coordination procedure is also part of this policy framework and is outlined in section 5 of this RALI.
4.1Spectrum and Channelling Arrangements
There are two UHF bands available for two frequency PMP data services; both are based on 12.5kHz channelling arrangements.
Use of 25 kHz channelling, by assignment of two contiguous 12.5 kHz channels, is permitted provided that a data rate of at least 4.8 kbps is used. When contiguous channels are combined the lowest channel shall be an odd numbered channel (e.g. 39-40). In locations where the service area is contained entirely within Low Density and Remote Density geographic areas[4]the data rate requirement does not need to be applied.
The bands of operation, as specified in the relevant ACMA band plans[5], are:
Master Transmit / Master Receive1. / 461.0125 - 462.0 MHz / 451.5125 - 452.5 MHz
2. / 929.5 - 930.0 MHz / 853.5 - 854.0 MHz
Table 1: PMP Bands of Operation
Detailed channelling arrangements are given at Annex B.
4.2Assignment Strategy
The assignment strategyfor dedicated PMP segments shall be as follows:
- Assign the highest available channel.
- This channel is assigned until it is fully loaded.
- Once a channel is fully loaded, the next highest available channel is assigned.
This strategy optimises the protection of services in the lower adjacent spectrum.
When PMP systems are assigned in 400 MHz land mobile segments, the assignment process shall be as prescribed in RALI LM8.
4.3Supplementary Transmitters
A supplementary station is a transmitter intended to improve the service reliability within a 30km radius of the master station. It operates on the same frequency as the master station and does not require frequency coordination. However, it must not cause interference to other radiocommunication services, and no additional level of protection from interference to a related receiver (above that offered intrinsically to a remote station) is provided.
Note that a transmitter that extends coverage beyond a 30 km radius of the master station is not a supplementary transmitter; it is another master station and must be separately licensed and coordinated in the same manner as any other master station.
Power and height constraints applying to supplementary stations are as follows:
Distance from Master: / Max. EIRP / Effective Antenna Height< 10 km / 20 W / 100m
< 20 km / 10 W / 25m
< 30 km / 5 W / 5m
5.0Recommended Frequency Coordination Procedure
Frequency coordination is performed only for master stations; interference protection for remote stations, supplementary stations and RCSs is intrinsic to the service model described in section3 of this RALI.
The following section details the coordination procedure that may be applied for frequency assignment of PMP master stations.
Alternative frequency coordination procedures may be used provided they produce equivalent results, that is, the target grade of service is achieved at 90% of locations within the service area (refer to section 3 of this RALI).
5.1Site Selection
Initial site selection is likely to be based on the client’s needs, but may need to be altered dependent on the outcome of the frequency selection process outlined below.
5.2Frequency Selection
Perform a cull (i.e. produce a list) of existing systems which due to their frequency and distance separation from the proposed system have the potential to cause or receive interference through co-channel emissions and unwanted emissions (including transmitter broadband noise). The minimum radii and frequency ranges for this cull are:
Band of Operation / Cull Radius / Tx / Rx400 MHz Band / 120 km / 100 kHz / 100 kHz
800 MHz Band / 100 km / 25 kHz / 25 kHz
Table 2: Cull Parameters
The appropriate table in Annex C of RALI LM8 shall be used to establish frequency-distance relationships for PMP master stations in the 400 MHz band. For the purposes of selecting the appropriate table a high power PMP is considered to be equivalent to a LMRS.
For the 900 MHz band, channels aredeemed not available if another master station of a PMP system has been assigned with any part of its channel within the proposed channel and is located within 100 km (the reuse distance) of the proposed site. For example, if operation of a 25 kHz system is sought on channels 1 and 2, and there is an existing 12.5 kHz assignment on channel 1 then the re-use distance is 100 km.
Of the remaining channels available, the channel with the highest centre frequency should then be selected, in accordance with the vertical loading principle outlined in section 4.2 of this RALI. Note that this will involve selection of a pair of frequencies (master transmit and master receive).
5.3 Intermodulation Checks
5.3.1 Introduction
Intermodulation checks are performed for two-signal 3rd orderand twosignal 5th order intermodulation, for high power PMP systems only.
Transmitter Intermodulation
The proposed transmitter must be evaluated for the potential for its emissions to mix with emissions from other transmitters at the site, to produce 3rd or 5th order intermodulation products that have the potential to cause interference to the proposed or existing receivers. Mixing of transmitter emissions can occur in passive components (e.g. site hardware such as couplers, isolators or mechanical/structural joints) as well as in non-linear transmitter output stages, and can result in intermodulation products that are co-channel with the proposed or existing receivers. As the characteristics of the components in which the mixing occurs cannot be known under these circumstances, the criterion for harmful interference caused by transmitter intermodulation is simply the occurrence of a ‘hit’ between co-sited systems, unless other evidence can be cited to demonstrate that the intermodulation interference is acceptable or is unlikely to cause interference.
Receiver Intermodulation
The proposed receiver, and existing receivers within specified frequency ranges and distances of the proposed system, must also be evaluated for their potential to receive interference due to intermodulation products caused by the mixing of transmitter emissions in proposed and existing receivers. Intermodulation products can be generated in the rf input stages of receivers if sufficient signal power is applied to drive a stage into a non-linear condition. Because of this input level dependency, the ‘quality’ of a hit can be quantified and either noted as having the potential to cause harmful interference, or discarded because it does not have a sufficient level to cause harmful interference.
5.3.2 Cull for Intermodulation Checks
Perform a cull of existing systems for which the potential for intermodulation interference must be considered. The cull identifies all such systems within defined frequency and distance limits from the proposed system. The radius and frequency range for each required cull is specified in Annex C, Table C1, of this RALI.
5.3.3 Performance of Intermodulation Checks
Perform checks for intermodulation interference between the selected assignment frequency (both transmit and receive, if they are different) and existing systems yielded by the cull, in the manner described below.
Transmitter Intermodulation
If the operating frequencies of any two co-sited transmitters (including the proposed transmitter) are contained in the relevant bandplan (e.g. the entire VHF Mid or High Band), and can be algebraically combined in the form shown in Table 3 to produce a 3rd or 5th order intermodulation product within the ‘hit’ range of a co-sited receiver (as defined in Annex C, TableC2, of this RALI) the proposed frequency should not be assigned, unless other evidence can be cited to demonstrate that the level of intermodulation interference is acceptable.
Frequencies of 3rd Order Products * / Frequencies of 5th Order Products *2f1 - f2 / 3f1 - 2f2
2f2 - f1 / 3f2 - 2f1
*f1 = centre frequency of first co-sited transmitter
f2 = centre frequency of second co-sited transmitter
Table 3 - Algebraic expressions for 3rd and 5th order intermodulation
product frequencies
Receiver Intermodulation
All systems falling within the cull limits specified in Annex C, Table C1, of this RALI are first evaluated for the occurrence of 3rd and 5th order intermodulation product ‘hits’ as per Table 3. A ‘hit’ is deemed to occur when an intermodulation product falls within the frequency ranges from a receiver specified in Annex C, Table C2, of this RALI.
Once the existence of a ‘hit’ has been confirmed, mathematical expressions (1) and (2) shown at Annex C3 of this RALI are evaluated to determine whether unacceptable interference would be caused due to receiver intermodulation by assignment of the proposed frequency.