Antenna performance is a dominant factor in determining the extent of possible frequency re-use or spectrum efficiency within the fixed point-to-point service environment. For a system designer, the choice of a suitable antenna requires consideration of a number of factors and often involves a trade off between capital cost and required system performance. The wider issues of interference management and spectrum efficiency usually fall to the industry regulator. Accordingly, most OECD regulatory authorities specify minimum performance criteria for antennas.
The ACMA specifies antenna compliance requirements for microwave fixed point-to-point services in Appendix 11 of RALI FX3. These compliance arrangements are based on the antenna front-to-back ratio and cross-polar discrimination.
Furthermore, RALI FX3 requires that frequency coordination studies use actual manufacturers' antenna radiation pattern envelope (RPE) data and that these antenna RPEs be supplied to the ACMA (.docx 89 kb) with any proposed frequency assignment. The ACMA now maintains a database of antenna data, including RPEs in NSMA format, for antennas used in previous frequency assignments.
In Australia, from about 1990, a 'notional' minimum performance antenna has been specified for each microwave frequency band. These notional antenna requirements were specified in the form of on-axis gain, half-power beamwidth and radiation pattern envelope (RPE) (See RALI FX3). The methodology used to establish these notional antennas can be found in Spectrum Planning Report SP 5/90, Notional Microwave Antenna Radiation Patterns (PDF 2.1 mb). Proposed antenna models are assessed against the notional antenna criteria for the respective band and are either deemed as compliant or non-compliant.
In 2001, a review (PDF 264 kb) of commercially manufactured (1.5 - 58 GHz) parabolic antennas was undertaken to assist in the development of more efficient and market sensitive spectrum access and regulatory frameworks. The information paper is available at: Microwave Fixed Services: a survey of commercially manufactured (1.5 - 58 GHz) parabolic antennas (PDF 264 kb).
In June 2003 the former ACA completed a review of the regulatory arrangements relating to minimum antenna performance criteria for microwave fixed point-to-point services in the bands from 1.5 GHz to 58 GHz. These change to the regulatory arrangements proposed resulted in part from considerations of the 2001 review.
A discussion paper Proposal for Spectrum Efficient Antenna Performance Regulatory Criteria for use in the Fixed Service Microwave Bands (PDF 107 kb) was released seeking comment on the proposals and recommendations in the paper. After the consultation process a further paper Spectrum Efficient Antenna Performance Regulatory Criteria Proposal - Summary and Discussion of Responses (PDF 41 kb) was developed to address the issues raised, comments received and provide final recommendations.
As a result of those recommendations, RALI FX3 was revised in April 2004 to introduce antenna the current arrangements.
To assist with the introduction of the new arrangements there was a transition period between 31 March 2004 and 31 March 2005. During the transition period the use of either the "notional antenna" arrangements or the new arrangements was allowed. As the transition period has ended the use of the notional antennas for new assignments will not be accepted.