BC95-G - downlink only possible after uplink


I am currently working with a BC95-G module. I can communicate in UDP or TCP to send and receive messages.

My current problem is that I can’t receive a message in downlink if I haven’t previously sent a message in uplink. If I wait for example 2 minutes and I send a message in downlink, I don’t receive it on my NB-IoT module.

Is this a limitation of NB-IoT ? Or is it an error on my part?

Can you help me? Thank you in advance.

I was able to solve the problem by disabling PSM and eDRX :


=> AT+CEDRXS=0,0

I now always receive the data, but sometimes it takes several tens of seconds (up to 1min). This happens when I wait a long time between 2 transmissions.

How can I change this?

Hi Maximuschar
You can send a packet of uplink data every minute as a heartbeat packet to maintain the downlink.

You can also find a local operator to activate the real-time downlink function through the APN of the SIM card.