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SIMCOM7080G (NB-IoT/CAT-M) AT commands for low power use


Mar 16, 2024
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Hi all,

I am working on small device with a few sensors. I'm using a SIMCOM7080G for NB-IoT comms (The 7080G is also CAT-M compatible and I will be trying that too). I have it working with a bunch of AT commands (to set it to NB-IoT, set the bands to use, set the APN, check for network registration and then finally send a small payload to a cloud server using the in-built CoAP client).

I'm not doing any type of power management other than powering up the modem, doing all the AT comms and then powering down the modem (using it's PWR line which I toggle high and low as per SIMCOMs instructions).

I'm finding it's taking up to 90 seconds to the the payload sent and most of the time is spent waiting for the modem to register to the network (when "AT+CGATT?" returns a "1" in the response).

I'm not sure if I'm meant to be doing anything differently for NB-IoT to reduce the amount of time it takes the modem to register to the network (but in a way that I can still shut down the modem to conserve power because I want to send a payload nightly and run this on a non-rechargable Li-Ion battery).

Does anyone know about this type of usage (NB-IoT) and optimising/reducing the time to get a payload sent ? Or what the best practise should be or any links to example sets of AT commands?

So far I've just been working off the SIMCOM AT command reference document - to the point where I can successfully get messages sent but it's leaving me concerned about the long registration times and the fact I I'm not sure how, or if, things should be done differently with LPWAN / NB-IoT (compared to old 2.5G modems).

thanks for any information/help at all!

Hi Derek,

It sounds like you are already on the right track with using the SIMCOM7080G for NB-IoT communications. Here are a few suggestions to potentially optimize the registration time and improve the efficiency of your setup:

1. **Network Selection**: Ensure that you are selecting the appropriate network bands for NB-IoT in your area. This can help the modem connect to the network faster.

2. **Paging Time Window**: Check if your modem supports setting the Paging Time Window (PTW) parameter. Adjusting this parameter can help reduce the time it takes for the modem to receive paging messages from the network.

3. **Keep-Alive Mechanism**: Implement a keep-alive mechanism to maintain the network registration status without having to re-register every time you want to send data. This can help reduce the registration time when you need to send payloads.

4. **Power Saving Modes**: Explore if the modem supports power-saving modes specific to NB-IoT that can help conserve power while still maintaining network registration.

5. **Firmware Updates**: Ensure that you are using the latest firmware version for your modem as it may include optimizations and improvements that can help with network registration times.

6. **Consult Manufacturer Documentation**: Reach out to SIMCOM or refer to their technical support resources for specific guidance on optimizing network registration times for NB-IoT.

By implementing some of these suggestions and potentially tweaking your AT commands based on the modem's capabilities, you may be able to reduce the time it takes to register to the network and send payloads efficiently.

If you have any specific questions or need further assistance, feel free to ask!

Best regards

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