NB-IoT transmission repetition

[junenergy]

Hi,

I would like to find out the settings of nRF9160 in terms of transmission repetition to ensure successful transmission/data receive by the base station.

My understanding is that, the maximum repetition when the NB-IoT node is in:

• 8 times in EC0
• 64 times in EC1
• 512 times in EC2

Does the nRF9160 module gradually repeat the transmission in the step of 2 or it simply go for the maximum repetition in each EC?

Many thanks,

jun

[Øyvind]

Hello Jun, 

The nRF9160 LTE modem support 3GPP release 13 coverage enhancement. Have a look at the Coverage enhancement mode notification +CEINFO and Evaluating connection parameters %CONEVAL AT commands for more information. Coverage Enhancement (CE) levels 0–2 are supported in NB-IoT. 

<ce_level>
0 – CE Level 0. No repetitions or small number of repetitions.
1 – CE Level 1. Medium number of repetitions.
2 – CE Level 2. Large number of repetitions.
3 – CE Level 3. Very large number of repetitions (not supported).
255 – Invalid or not known.
If <rrc_state> is 0, the CE level is estimated based on RSRP and network configuration.
If <rrc_state> is 1, the CE level corresponds to the currently used CE level.

From the GSMA Mobile IOT Deployment Guide October 2022:
Each CE Level of NB-IoT determines the number of times downlink and uplink messages can be repeated to reach devices in poor coverage and the number of repetitions in each CE-Level is predefined by the network.

Kind regards,
Øyvind

[junenergy]

Dear Øyvind,

Thanks for the prompt reply.

I haven't got any modules from any manufacturers to do the test yet because I want to understand the configuration first before going to purchase something that might not meet my needs.

I had a conversation with some network providers before and I have been told that some modules will simply do the maximum repetition in any CE levels while some will gradually increase the repetition in the step of 2 and stop when the transmission is successful.

So, I would like to find out what is the configuration of nF9160? Does it simply do the maximum number of repetitions in any CE levels or gradually increase the repetitions and stop when the transmission is successful?

Many thanks,

jun

[Øyvind]

junenergy said:

So, I would like to find out what is the configuration of nF9160? Does it simply do the maximum number of repetitions in any CE levels or gradually increase the repetitions and stop when the transmission is successful?

Talking to our experts on the matter of coverage enhancements, they provide the following explanation:

In general (on field conditions) network (eNB) works so that when there are problems in it's reception, it first increases device Tx power as far as possible and when that is not enough it starts to add repetitions to the device transmissions, i.e. the device does not decide how many times it will repeat everything that it sends, nor the Tx power that is used.

Network adjusts device Tx power based on Power Headroom Reports that device adds to what it sends. Basically device tells how much power headroom it still have until it hits max Tx power in these PHRs.

junenergy said:

So, I would like to find out what is the configuration of nF9160? Does it simply do the maximum number of repetitions in any CE levels or gradually increase the repetitions and stop when the transmission is successful?

This means that we are not able to answer this question. It will just obey the network.

Kind regards,
Øyvind