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
In response to recent world events, the International Amateur Radio Union has issued the following statement:
“IARU is an apolitical organization focused on promoting and defending amateur radio and the amateur radio services. The amateur radio service is about self-instruction in communications and friendship between people.”
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.
Preparatory activities and studies relating to WRC23 AI9.1b have continued in the ITU‑R working parties 4C and 5A during October and November 2021. Although Region 1 administrations have been most actively engaged, the studies continue to evolve and RNSS operators from all regions have been participating in the discussions.
In ITU‑R WP5A a first draft ITU‑R Recommendation was proposed which may form the basis for recommending guidance for concerned administrations regarding amateur service coexistence with the RNSS. Work on all these elements will continue into 2022.
During the period 5–13 July 2021, the preparatory work for WRC-23 agenda item 9.1b continued in ITU‑R Working Party 4C (WP4C). (See Region 1 Feb 23rd news item for further background). The IARU member representatives from Australia, Brazil, Canada, Germany, Japan, Norway, UK and USA, participated in the meeting and delivered additional information on amateur activities in this key microwave band.
Preliminary studies came from France based on the ongoing CEPT work to provide initial estimates of separation distances required between RNSS GALILEO receivers and a sample of amateur emissions. The European Commission GALILEO team provided a set of observations pertaining to a RNSS interference event in northern Italy.
The work contributed by France, although needing refinement, is going in a good direction, using ITU‑R recommended propagation models and assumptions based on operating scenarios provided by the amateur community. Further work is needed to take account of the large disparity between the RNSS service receiver bandwidths and the frequency band offsets of the amateur applications based on the measurements carried out by Germany.
The RNSS community have updated their RNSS receiver protection criteria with an update to ITU‑R Recommendation M.1902 that now includes parameters relevant to the GALILEO E6 signal block. However these criteria only distinguish between a narrow band and wide band interferer level at the receiver and take no account of offset frequency in the receiver bandwidth or any time variance.
The IARU is working to ensure the amateur services are realistically represented in the studies as they move forward. It remains vital that national amateur communities present their views on the importance of this band to their national regulators in a consolidated and consistent manner. The work will continue throughout the year and beyond both in ITU‑R and in the regional telecommunications organisations and the IARU is committed to ensure every group hears the amateur position on this important microwave band.