Different networks, different eDRX-settings. Best practices?

[BrianO]

Dear community,

I am using the nRF9160 chip, and I have the issue of occasionally unreliable positioning. Depending on the network, positioning happens quickly and is accurate. On another network, I have inaccurate positioning.

I suspect the interplay of eDRX and LTE connection seems to be at fault. Each carrier seems to have its quirks. 

I was considering storing a set of favorable eDRX settings and querying the network with "+CEDRXS?". Based on the response, I would take the most preferred eDRX setting or notify that LTE and GPS are not compatible on this network. Does this make sense?

Does someone have some advice for handling the LTE settings of different, mainly European (Swiss and German to be specific), network operators?

Thank you in advance for any tips!

Kind regards,

Brian

[dejans]

Hi,

I have the issue of occasionally unreliable positioning. Depending on the network, positioning happens quickly and is accurate. On another network, I have inaccurate positioning.

Could you please provide more information about your application/use case? In addition, could you specify on which networks you have seen accurate and in which inaccurate positioning? How accurate or inaccurate are obtained positions?

+CEDRXS command is used to set requested eDRX parameters. The values that are set can differ from actual values provided by the network. The value of network provided eDRX parameter does not necessarily indicate that eDRX is in use by the current cell to which the UE is registered. The use of eDRX can be dynamically monitored with the unsolicited notification +CEDRXP and its <ActT-type> parameter. For dynamic reading of eDRX parameters, command +CEDRXRDP can be used. Here are some relevant links from the documentation which might be useful: AT commands, AT command exercise, +CEDRXS and +CEDRXRDP.

Best regards,
Dejan

[BrianO]

Hi Dejan,

Thank you for the speedy response. Our use case is a battery-powered hip-belt wearable. The LTE connection is necessary for messaging and retrieval of AGPS data. These devices are distributed across many, mainly European, networks with roaming enabled.

Unfortunately, I report customer issues, and I suffer from an inability to reproduce their problems. They report a high positional accuracy (< 20m) but their actual position will be hundreds of meters from the reported one. Because I have been unable to reproduce the issue, I thus can't answer most of your questions. Therefore I ask about best practices. 

Thank you for the tip about +CEDRXRDP. That is what I actually need. Also, the Nordic tutorials are much nicer than reading the 3GPP specs!

Kind regards,

Brian

[dejans]

Hi Brian,

We need more information to be able to answer your question. The accuracy issue which they observe is likely not related to the interplay of LTE and eDRX. Can you ask the customer to provide some additional details on the issue that they report? It could also be very useful if you could replicate the issue which they report. If details provided by the customer are private and information sensitive, I can make this ticket private so that shared information is not publicly visible.

EDIT:
Which modem firmware version does the customer use? They could try to upgrade modem firmware to version 1.3.6 which has many GNSS improvements. 

Best regards,
Dejan