nRF9160 battery life

[eyss5]

Hi, I'm looking to develop a GPS tracker over LTE-M/NB-IOT using nRF9160. The user needs to be able to reach the device to check its location on demand (20s delay is OK). Product size should be small, likely 100mAh LiPo battery. I'm hoping for battery life of months - 1 year.

Do I understand correctly that since the device needs to be reachable at all times, PSM is out of the question? 

I tried using the online power profiler with DRX modes (20s iDRX interval). The other variables don't seem to make a big difference. Comes out to 0.15mA. On a 110mAh battery, that gives me about 30 days. Would you expect a on-demand GPS tracker on a small battery to last 30 days? Or is something misconfigured/misunderstood?

[Stian Røed Hafskjold]

The UE uses the paging occasion (eDRX interval) to listen for incoming data. It doesn't actually receive anything unless the network has data to transmit. The network will store the data and wait to transmit the data until the scheduled UE paging occasion happens.

So while the UE stays in RRC idle mode, it wakes up periodically (eDRX interval), turns on the radio receiver, listens to the PDCCH channel, and if no information is received (no paging), it assumes that the network has nothing to transmit and will go back to sleep. If the UE receives a paging event and there is data to be received, it will go from RRC idle to RRC connected mode, receive the data, respond to the message (send data), and go back to RRC idle again.

If you want to simulate this in the online power profiler, turn off PSM, set the required iDRX interval (this will be the latency) and then adjust the data transfer interval to how often the tracker is being used, e.g. a day, or week. You will see that the added average current by waking up is starting to get negligible when you get to a wakeup interval of a day or more.

[eyss5]

Perfect, thanks!