The following shows Ionospheric activity from GMT 13:00 ~ 22:00, or Ecuador time 8:00AM ~ 5:00PM for 22th day of July ~ December, using data from http://www.ss.ncu.edu.tw/~istep/tgim.html
July 22 --- August 22 --- September 22
October 22 --- November 22 --- December 22
One can see that the daytime ionospheric activity in recent month is getting very high, unfriendly for RTK operation.
S100 being GPS/GLONASS/Galileo/BDS 4 constellation RTK receiver, works optimally when used with GPS/GLONASS/Galileo/BDS 4 constellation RTK base.
REGME-IP being GPS/GLONASS RTK base, will render S100 to be no different from a GPS/GLONASS 2 constellation RTK receiver. In such case, under high ionospheric activity, using S100 with REGME-IP will be more difficult than using S100 in base/rover pair under 4 constellation mode. One can consider using S100 with REGME-IP at time of day with lower ionospheric activity. Alternatively, one can use a pair of S100 in best RTK performance 4 constellation mode by (1) setting up a local S100 RTK base, (2) connecting to REGME-IP at time of low ionospheric activity to establish base coordinate, (3) use S100 base/rover pair during daytime.
Below figure A gives effective satellite number estimate when using S100 with REGME-IP, 15 degree elevation mask angle assumed. Figure B gives effective satellite number estimate when using 2021.11.22 firmware for S100 base/rover pair. Figure C gives effective satellite number estimate when using 2021.12.23 firmware for S100 base/rover pair. The latter B and C, with much more usable satellites, will work better than A at same baseline distance under higher ionosperic activity situation.