WRC23 – agen­da item 9.1b

The IARU main­tains the view that the like­li­hood of wide­spread and per­sis­tent inter­fer­ence from ama­teur radio activ­i­ties to RNSS (e.g. Galileo) receivers in the 23cm band is min­i­mal. The WRC-23 prepara­to­ry stud­ies car­ried out in the ITU‑R study groups have only con­sid­ered sta­t­ic one-to-one esti­ma­tions using a min­i­mum cou­pling loss approach. These stud­ies do not con­sid­er the effect of an ama­teur trans­mit­ter on a pop­u­la­tion of RNSS receivers deployed around an ama­teur trans­mit­ting station.

There­fore IARU vol­un­teers have car­ried out a “Monte Car­lo” style study sim­u­lat­ing sce­nar­ios assum­ing a fixed and mobile pop­u­la­tion of RNSS receivers deployed around an ama­teur sta­tion. A 100W ama­teur ‘home sta­tion’ and a 25W eirp ‘repeater sta­tion’ have been assumed.

The sim­u­la­tion results sug­gest that at most only around 1% of a pop­u­la­tion of fixed and mobile RNSS receivers ran­dom­ly sit­u­at­ed around a trans­mit­ting ama­teur sta­tion loca­tion would have a small chance of receiv­ing a sig­nal lev­el above the RNSS pro­tec­tion thresh­old iden­ti­fied in the rel­e­vant ITU‑R Rec­om­men­da­tions. In most sce­nar­ios, the per­cent­age of RNSS receivers impact­ed by inter­fer­ence above the thresh­old with­in the “sim­u­la­tion area” is far less than 1%. Even in the dens­est areas of ama­teur sta­tion activ­i­ty and with the low­est clut­ter mod­el the per­cent­ages remain less than 5%.

See video rep­re­sen­ta­tions of the sim­u­la­tion sce­nario here.

The study assumed that an ama­teur sta­tion is trans­mit­ting through­out the whole “Monte Car­lo” tri­al peri­od. How­ev­er event data col­lect­ed by the IARU shows that even in the busiest ama­teur com­mu­ni­ties the amount of time dur­ing which these spo­radic trans­mis­sions are most like­ly to occur amounts to less than 2% of time over a one year period.

There­fore the IARU main­tains its posi­tion that the poten­tial for wide­spread and per­sis­tent inter­fer­ence between ama­teur radio trans­mis­sions and RNSS receivers is minimal.

The IARU paper is avail­able for shar­ing and can be found here.