nRF9151 UART packet size limitation and throughput issue

We are using an MCU that pushes data packets to the nRF9151 communication module via UART. According to our module service provider, each data packet can only be up to 2 KB. They said if the packet size is larger, the module would run into buffer limitations. However, we have not tried this ourselves yet.

At the moment, we are transmitting 1 KB per packet. Each 1 KB packet takes around 3 seconds to complete the sending flow, which means the effective throughput is only 1 KB every 3 seconds. This is too low for our application.

We would like to increase the packet size (ideally 6–10 KB per packet) to improve throughput, but our module provider told us it is not possible.

My questions are:

  1. Is there a strict limitation in the nRF9151 firmware or hardware that prevents sending packets larger than 2 KB?

  2. Is it possible to configure the system to support larger packet sizes (6–10 KB), or is it indeed impossible?

  3. If larger packets are not supported, what is the recommended method to improve throughput in our case?

We need to transfer larger amounts of data (hundreds of KB). With the current 1 KB/3s limitation, the process takes more than 10 minutes, which is unacceptable.

Any guidance on how to optimize this would be greatly appreciated.

Thanks!

  • Hi,

     

    Is there a strict limitation in the nRF9151 firmware or hardware that prevents sending packets larger than 2 KB?

    Yes, for secure sockets, the limit is 2k:

     RE: Max RX Receive Buffer 

    Is it possible to configure the system to support larger packet sizes (6–10 KB), or is it indeed impossible?

    No, you need to manually send it in chunks in this case.

    If larger packets are not supported, what is the recommended method to improve throughput in our case?

    Send the packets in chunks.

     

    We need to transfer larger amounts of data (hundreds of KB). With the current 1 KB/3s limitation, the process takes more than 10 minutes, which is unacceptable.

    1/3 kB/s sounds a bit low. Is this LTE-M or NB-IoT?

    Where is the bottleneck in this setup? 

    Have you tried to run samples/net/download to see what speeds you observe there?

     

    Kind regards,

    Håkon

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