Over the period 14th to 25th November 2022, the preparatory work for WRC-23 agenda item 9.1b continued in ITU‑R Working Party 5A (WP5A). Two deliverables are under discussion:
1) Draft ITU‑R Report M.[AMATEUR_CHARACTERISTICS] – this reports on the specific 23cm band amateur and amateur satellite service technical parameters and operational characteristics used in the studies now published in ITU‑R Report M.2513–0.
2) Draft ITU.R Recommendation M.[AS_GUIDANCE] – this will recommend guidance that national administrations can take to facilitate the protection of the radio navigation satellite service from harmful interference from amateur radio stations.
Since the previous WP5A meeting the IARU global WRC23 9.1b team led by G4SJH has been consulting with the amateur community resulting in a contribution to the draft guidance recommendation. As usual, the IARU participated in the meeting to support the contribution and take part in the ongoing discussion and negotiations. Contributions were also provided by a number of national administrations and a summary report of the meeting can be downloaded.
In general the development of the recommendation is moving in a suitable direction and many of the IARU proposals remain in the draft document that will go forward to the next meeting for further work.
Meanwhile in CEPT the work in project team SE40 continues with their development of an ECC Report on the same coexistence problem and also met during November (3–4th).
The work on this topic will continue throughout next year both in ITU‑R and in the regional telecommunications organisations and the IARU is committed to ensure the studies are properly interpreted and that due account is taken of the realities of amateur operations in this band.
During the period 7–13 September 2022, the IARU once again participated in the preparatory work for WRC-23 agenda item 9.1b in ITU‑R Working Party 4C (WP4C). The IARU summary report on the WP4C meeting can be found here.
Updated studies were provided by France and new studies were contributed by the Russian Federation (GLONASS), China (COMPASS) and Japan.
The IARU provided a contribution providing information agreed in WP5A highlighting the low duration of “busy times” for amateur activities in the 23cm band. This information was adopted into the draft report. Whilst the studies confirm the potential for interference to occur into co-frequency RNSS receivers in almost the entire band, all the studies have assumed only static scenarios without any consideration of the geographic distribution and density of amateur transmitters or the temporal aspects of amateur or RNSS operations. Some studies take account of antenna patterns, but many results and conclusions focus only on worst case main beam consideration. The IARU Region 1 has published a commentary document on these aspects available here.
As a result of these studies and the regulatory status of the amateur service allocation, our ability to operate in certain parts of the band and at the power levels allowed today is likely to be constrained if regulators want to protect the RNSS receivers. This discussion will continue in the development of the Guidance Recommendation in ITU‑R WP5A.
WP4C plenary agreed to elevate the document to Draft New Report status and passed it to Study Group 4 (SG4) for adoption. Therefore drafting work is complete.
Study Group 4 met on September 23rd and adopted the report for publication. IARU is totally engaged in the discussion that will continue in WP5A to ensure that the amateur services can continue to develop in this band and allow all the amateur applications in use today to continue.
As the WRC-23 approaches so the studies regarding AI9.1b (23cm and RNSS) are working towards conclusions. However the IARU is not content that all the operational aspects of the amateur service usage of the 1 240- 1 300 MHz band are being properly considered to develop an acceptable compromise for all concerned parties. You can find some more detail on the areas of concern in this discussion paper posted in the global IARU WRC23 web pages on this topic. See IARU Perspective on the AI9.1b Progress — September 2022.
During the period 4–10 May 2022, the IARU continued to engage in the preparatory work for WRC-23 agenda item 9.1b in ITU‑R Working Party 4C (WP4C).
Work continued to develop the coexistence studies between the amateur services in the 23cm band and the radio-navigation satellite services (RNSS) operating across the band. New studies were submitted by France, China and the Russian Federation.
The scale of the problem for the amateur services is becoming clear. For example, the studies predict that even a 10W 23cm band station could cause interference to RNSS receivers at up to 30km on the antenna main beam heading. Although the level of amateur activity and the density of users is quite low (compared to other more popular bands) the issue remains that from a regulatory perspective the amateur services are required to not cause harmful interference to RNSS services.
The figure below is a sample of one result from one study submitted into ITU‑R and further illustrates the scale of the problem. In this example a station using an 18dBi gain antenna is used for both narrow band and wideband (ATV) transmissions and a range of power levels. The protection criteria for the RNSS receivers differs for narrowband and wideband interfering signals. The figure shows the distances out from the amateur station where the RNSS protection criteria could be exceeded along the antenna main beam heading.
These results have been developed based the ITU‑R defined receiver protection level for the GALILEO RNSS. For the narrow band modes this is ‑134.5dBW and for the wideband modes is ‑140dBW/MHz. In addition, measurement campaigns have shown that an improvement in the compatibility potential can be seen if the amateur signals avoid the centre portion of the GALILEO receiver passband.
Of course the studies cannot take into account every possibility that might mitigate the problem (e.g clutter, terrain blocking etc.) but it is clear that the potential for interference is considerable.
The IARU is working hard to ensure that the amateur service can continue to develop in this band and allow all the amateur applications in use today to continue. However, given the heavy spectrum occupancy of the band by the various RNSS systems it is evident that proposals will come calling to restrict our ability to operate in certain parts of the band and at the power levels possible today. IARU is totally engaged in the discussion of these considerations and these will continue within ITU‑R (and other regional bodies).
The IARU summary report on the WP4C meeting can be found here which in turn includes a link to the full draft stu
As we head into 2022 the ITU‑R and CEPT work considering the 23cm band and coexistence with the RNSS systems (GALILEO, COMPASS, GLONASS, GPS…) will continue so where have we got to and where is it heading?
The IARU has provided extensive information regarding the amateur and amateur satellite service applications in the band 1240–1300MHz as well as operational characteristics and data indicating the density of active transmitting stations and the busiest periods when these are most likely to be operational. Using this data, one CEPT administration has provided an extensive set of propagation model predictions for a number of amateur operating scenario assumptions (including satellite working and EME operation) that predict an “interfered area” over which an amateur transmissions may be received by a RNSS receiver at levels exceeding a defined protection level. Another ITU‑R member administration contributed a smaller set of predictions using the same model. The received RNSS interference level that the RNSS can tolerate (receiver protection level) is based on ITU‑R recommended criteria and depends on whether narrowband or wideband interfering signals are being transmitted.
The propagation model predicts that an interfered area can extend out to several tens of km (depending on the scenario) but at the extremes of the area, the time probability of exceeding the protection level is very low (1%) and for only 50% of locations. The model can only assume a full power continuous transmission.
In addition much attention has been paid to documenting an interference case recorded in Italy between an Italian 23cm band repeater and GALILEO receivers at the nearby European Commission Joint Research Centre in Ispra where work is undertaken to develop and test GALILEO system applications. The impact of traffic through this very local repeater (12.5km distant) on three different GALILEO receivers has been documented. This work suggests that whilst RNSS receiver bandwidth can have a part to play in enabling coexistence, beyond that nothing has been reported that could help develop any coexistence criteria. Nothing is reported about the mode of failure in the receivers beyond degradation on C/N.
This one case is often cited as the “proof” that interference can occur.
At present the conclusions from this work are being developed (in ITU‑R and CEPT) and IARU work continues to ensure these results are put into a real world context to understand what they imply with respect to successful coexistence.
Amateur transmissions virtually anywhere in the band will be co-frequency with the RNSS receivers from one system or another. It is therefore obvious that any RNSS receiver will be open to any co-frequency amateur transmission and amateur operators have no way of knowing where or when a RNSS service user is active. Therefore IARU has expressed a view that for successful coexistence guidance to be developed, some compromises will need be necessary.
As we move through the work in 2022 we need these compromises will become apparent so that the amateur community can know how to respond appropriately in a way that can allow our diverse set of applications to continue to develop whilst minimising any potential disruption to RNSS services. It is anticipated that the international views on the ITU‑R studies will need to stabilise by the middle of this this year in order to meet the timetable for the WRC-23 preparatory work. These views will likely propose technical and operational measures to be applied to the amateur and amateur satellite services that could be formalised in the Radio Regulations.
As the study activities work towards conclusions it is vital that the national societies engage with their national amateur radio regulators to ensure they understand and hear about the importance of this band for the amateur radio community.