How to use GPS directly after LTE?

[Jan Erik]

Hi,

We're connecting to our server over LTE and then immediately starting GPS search.
The modem is in LTE+GPS mode.

As we understand it, the GPS will do nothing for about 60 seconds while the modem is in RRC idle.
After about a minute the modem enters PSM mode, at which point the GPS driver will start searching for a fix.
Is there any way we can reduce this time?

We have tried to change the PSM active time to 2 seconds, and the modem confirms we were allowed to use that.
We're a bit concerned that the operators might override us and set a much higher active time at any point in the future though.
Talking to the operators directly is definitely the best solution here, but do you have some information regarding this?
Are there any drawbacks to a very short PSM active time?

One alternative solution we have brainstormed is to set the modem to only GPS mode, and then changing it back to LTE+GPS after fix.
However we are concerned about the power consumption cost of reattaching (reconnecting?) to the network in that case.

Another potential solution is to use eDRX mode.
How quickly can the modem enter eDRX mode after sending data over LTE?
And the GPS would be able to start searching immediately after entering?

What is the standard way of doing GPS search immediately after sending data over LTE?

[Hakon]

Hello,

 

Is there any way we can reduce this time?

Other than reducing the active time, I don't think there is.

Are there any drawbacks to a very short PSM active time?

Aside from being reachable for a smaller amount of time by mobile terminating services, I am not aware of any drawbacks. You could in theory have a PSM active time of 0 if the network allows it.

One alternative solution we have brainstormed is to set the modem to only GPS mode, and then changing it back to LTE+GPS after fix.

If you want to instantly go from using LTE to using GPS, this is probably the way to do it. One thing to keep in mind is that reconnecting can be quite time consuming, so it is not ideal if you are sending data often. You should consider using the XBANDLOCK command if you're going with this option, to reduce the amount of time it takes to reconnect.

And the GPS would be able to start searching immediately after entering?

 With eDRX there is a similar issue, which is the paging time window. This is also a parameter that can be set by the application, but it might also be restricted by the network.

What is the standard way of doing GPS search immediately after sending data over LTE?

 I'm not sure there is a standard way, you will need to go with whatever way suits your application.

[anicare-tero]

Is there any notification when the device is released from RRC idle that could be used as a trigger to start GPS?

[Hakon]

Yes, I believe you can use the +CSCON command.