NB-IoT packet loss

[allard.p]

I'm testing a simple application based on the UDP/CoAP example.  It samples some peripherals and ADC channels, these values are then packed into a CoAP message. This CoAP message is sent trough the socket api (UDP), and the application waits for a response. I've run some tests using different power saving settings. The current version uses PSM in between samples and uses RAI to prevent long time spent in the 'active timer'.

A observation we made after analyzing the logs is the high rate of timeouts/packet loss. We declare a packet lost if the uplink CoAP packet, or the downlink CoAP ACK message is lost. We got a packet loss of around 3% over around 1000 messages (multiple devices, connected to the same cell). Questions:

• I known UDP is a unreliable protocol by design, but I'm wondering what packet loss numbers I should expect? What numbers are other users experiencing?
• Is there some way to identify the cause of these lost packets, using the PCAP/modem log files for example?

The devices all have a Taoglas MFX3 antenna connected, the RSSI is around -85dBm (%CESQ: 54,2,21,3).

[Achim Kraus]

> I will also setup a test in another area, maybe this cell is just busy, I think the number of NB-IoT devices here in the Netherlands is already quite high.

Any update? Does it work better in the other area? Did you try to start your communication timers with RRC connected?

[allard.p]

Yes, I think it was some temporarily network conditions. The same device is now seeing loss of around 1-1.5%, with over 10000 messages sent, I think this is acceptable.

[Achim Kraus]

That sounds now great. It matches also my experience.