Information Unlimited switching between LTE and GPS on nrf91 SoC

[smauelGIS]

Hello,

I received information that i could turn the modem on and off not more than 60 times within an hour.

We are however working on a real time system, which may require more than this limited number, so;

1. Is there a hardware solution from nordic that can give us unlimited number of switching, to collect GPS data and send using LTE?

2. Is there a firmware solution, if so how long should we wait for this firmware solution.

Thanks and Regards

Samuel

[Didrik Rokhaug]

Hi.

The limit of 30 connections per half-hour comes from the network, so there is no way around that unfortunately.

 

2. Is there a firmware solution, if so how long should we wait for this firmware solution.

 We already support GPS while in PSM and eDRX. We are also working on otherwise improving the GPS + LTE experience, allowing for even shorter timeslots for the GPS stack. However, the shorter you run the GPS stack, the less time it gets to search for satelites, and the longer it will take to get a fix.

 

1. Is there a hardware solution from nordic that can give us unlimited number of switching, to collect GPS data and send using LTE?

 The limitiation is in the network, and the nRF9160 is not able to run the GPS and LTE stack at the same time, so you can not solve this problem with the nRF9160 alone (except the above suggestion of not disconnecting LTE). However, you might be able to use an external GPS. That way, you can run the GPS and LTE at the same time as you are no longer bound by the limitations of the nRF9160.

Best regards,

Didrik

[Martin]

> Is there a hardware solution from nordic that can give us unlimited number of switching, to collect GPS data and send using LTE?
I am experimenting with the same.

It depends a little on your hardware and network.

I have a custom board modeled with the GPS using a small antenna, LNA, SAW with enable (GPS modeled after the newest DK hardware files available). This board has good GPS reception and I can easily get GPS location and send data to the server without switching off GPS or LTE.

This even works with the local network provider here in Brazil with LTE-M and no power saving (PSM/eDRX) modes available at all.
You just have to give the network time to detect no activity. With some networks (VIVO/Brazil, Swissom/Switzerland) this takes around 60-70 seconds and with other networks (Claro/Brazil) this is optimized and is down to 15 seconds.
Best way to detect that is to subscribe to the events with AT+CSCON=3 and you will get a message if the networks changes to idle mode. From this moment on the GPS gets more access to the RF.

With the network that idles in 15 seconds I am able to have a cycle of 30 seconds (sending data, wait for reply, wait for idle, get some GPS locations).
With the network that idles in over 60 seconds I am normally able to maintain a cycle of 90 seconds. But it seems that the actual GPS code has more problems to sync to the GPS and sometimes I have to increase the cycle or switch the LTE modem of to recover the GPS signal.

With the actual software ncs 1.2 and Fiwmare 1.1.1 on a NB-IOT network with  PSM and support for AT%RAI. I was able to have a cycle of 15 seconds (send data, receive data, idle network and use the rest of the time for GPS). 

With better software and a good network support you probably could get that down in the future to 5 to 10 seconds.
But if you need more real-time you probably will need an external GPS. 
This adds cost but might be also use quite less power that the Nordic integrated solution.

But at the moment with the Thingy.9 I have at the moment problems and can not get GPS data at all ...