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Take this information with a grain of salt until we can get an expert on NB IoT technology to answer this question, but the CE level should be set by the modem based on the measured downlink received signal power and increased automatically when the random access preamble retransmission limit set for the current CE level by the network has been reached.
How long it takes to reach this limit depends on the limit and the period between retries (waiting for the network’s random access response).

Hello again toustousio,

the reason why devices have to send an uplink message first to receive downlink messages lies in the nature of low-power wide-area devices, which are designed to use as little energy as possible to maximize battery life. This is achieved by putting devices to sleep. Keeping an open channel that can constantly receive data would go against any power-saving measures. Therefore, a device has to initiate the communication and basically send a “heartbeat” message to show that it is awake and available to receive information. Just like LoRaWAN class A devices, which do not maintain a constant network connection to reduce power consumption.

Using NB-IoT and eDRX, it is possible to move the buffering function of messages into the network to send the messages directly to your devices, without sending an uplink message to our platform every time before receiving downlink messages.
This is possible via our API and works just like sending a downlink message as described here with a few changes that I have detailed below.

URL: https://api.scs.iot.telekom.com:443/m2m/endpoints/<SERIAL-NUMBER>/downlinkMsgBase64Drx/0/data

HEADER:
Content-Type: application/json
Accept: application/json
Authorization: Basic <based64(<API-USERNAME>:<API-PASSWORD>)>

BODY:
{
“resourceValue”:<YOUR base64 encoded VALUE>
}

KEEP IN MIND:

• This function requires that <YOUR VALUE> is a base64 encoded. Before it is sent to the device <YOUR VALUE> is decoded, to be able to send binary data without double the data volume caused by the hex format.
• eDRX messages are sent to the mobile network and buffered/queued by the network provider while the device is sleeping.
• Because eDRX messages need to be sent to an IP address our server stores the last IP address from the last uplink message and if you haven’t send any uplink messages or if your device has renewed its IP address, the eDRX message cannot reach your device.
• Deutsche Telekom’s network is configured to store a max of 10 messages with 500 bytes per IMSI. This is also limited to a certain percentage of the specified number of devices (overall capacity). This behavior can deviate for roaming scenarios, since not all networks are configured the same way.

I hope this answers your question.
Do not hesitate to reach out, if you have any addtional questions or problems.

Hello Mario,
sorry for the late reply, I am definitely not more knowledgable, but I hope that fm’s hints have helped you to find a way to change your DNS servers via the +UPSD command.
If not, I have checked the documentation for your module and the Syntax looks as follows:

AT+UPSD=<profile_id>,<param_
tag>,<param_val>

The values should be:
<profile_id>: 1
<param_tag>: 4 for primary DNS; 5 for secondary DNS
<param_val>: “xxx.yyy.zzz.www” [your desired DNS’s IP]

While looking for the information, I also noticed a topic where another modem did not receive DNS servers from the provider due to a firmware issue, so maybe an update will alleviate the problem as well.

I will also check whether DNS info should normally be provided at that APN for LTE-M SIMs or not.

let us know how it went
olli

Hello @Mikael-Guenais,
NB-IoT roaming is available in France via SFR. You can also always find up-to-date information on our roaming partners in our documentation library here.

I will contact you about the SIM card directly from our support email.

Best regards
Oliver