Speed up 1PPS / provide a fix with fewer satellites

Hi Nordic team!

In our system, we’re using the GNSS functionality of the NRF91 to obtain the current time, which is crucial for synchronization across multiple stationary devices. We require timing synchronization within approximately 50 microseconds between the devices.

We're only doing the synchronization when an event happens, which can be once in a week for example. When it happens we need the synchronization to happen as soon as possible (within ~60s). We'd like to avoid depending on using A-GPS or P-GPS as the network connection could be unreliable in some cases.

We're already using the low accuracy mode so that 3 satellites are enough to produce a fix (we set the device altitude and position using nrf_modem_gnss_agnss_write) and set the system in stationary dynamics mode.

1. Do you have any other suggestions for the configuration that we could use to speed up getting the valid 1PPS pulse and make it more robust in the weaker signal strength situations (indoor near a window / on the balcony)?

2. Would it be feasible to add a "fully fixed position" mode support where the position of the device is known so that fewer satellite locks could provide the 1PPS pulse (lower accuracy would be acceptable)?

Any insights or suggestions you can provide would be greatly appreciated. Thank you!

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