RE: Regarding Nb-IoT and LTE cat M1 technology

Martin Lesund — Fri, 24 Apr 2020 09:49:51 GMT

Hi Reena,
The modem can be in either of these three modes:

RRC Connected mode
RRC Idle mode
PSM mode

When we discuss eDRX intervals, we usually mean the ones in RRC Idle mode since this has the greatest effect on the power consumption compared to the possible eDRX intervals in RRC Connected mode. So we usually differentiate the possible eDRX intervals in Connected mode and Idle mode as cDRX and iDRX.

"eDRX is a mechanism that can extend the cycle (sleeping duration) of these two DRX (Idle mode DRX and C-DRX)."

If you request the eDRX interval of 10,24seconds (and the network grants this request) you will go into a paging time window where the UE (nRF9160) listens on the network to see if there are any data that should be handled. If the network pings the device in this time window the modem goes into RRC Connected mode and handles the data. (e.g. send the updated sensor data request)

If the network supports "Store and forward polices" the network should handle this unless there are any restrictions in how much data or how long it needs to store it gets override.

You could also buffer it on the cloud side, if the network doesn't support this kind of feature so when the network wakes up the device it will pass along the data from your cloud.

From what I could find: https://www.business.att.com/content/dam/attbusiness/reports/what_need_know_iot_networks.pdf it looks like they support this feature, but I would recommend you to get a confirmation on their side as well if it's supported all over the USA. (Network/carrier-specific information should be addressed to them for the latest information and updates)

In the end, it is the network that decides if it will grant the requested (e)DRX (which is just extended DRX intervals) intervals from the UE, so it will tell you if the UE is granted the request, or if it is not then also give you information on which interval it hands you. Historically we see that it's "easier" to request longer intervals than short.

Best regards,
Martin L.