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Bluetooth Low Energy Total Network Throughput

Matt Kenyon2
Prodigy 80 points

I understand that the stack is currently limited to 3 slaves connected to a master at a given time. I also understand the current throughput for a given connection to be limited to roughly 5.9kbytes/sec. When I have all three slave connected can I expect each slave to be able to achieve roughly 5.9kbytes/sec resulting in a total network throughput of roughly 17.7kbytes/sec? Or is the total network throughput limited to 5.9kbytes/sec which means each slave is only achieving roughly 2kbytes/sec?

  • 0
    Guru 22270 points

    Hello Matt,

    Now that is a very interesting hypothesis.  The logic of your theory seems valid.  Only the designers at LPRF will truly be able to answer this one.

    In the meantime, I can just speculate...

    The 3 connection limit is based on resource constraints of the 8051 MCU. From my understanding, the maximum payload size restriction is based on the timing requirements of BLE.  Each connection has to conform to this timing limitation and payload size.  The 3 connections are transmitting on 3 different channels and each channel is read sequentially and there are 37 channels.  

    Taking into consideration the frequency hopping and other BLE overhead that is going on, I would have to conclude that the maximum data rate would have to be less than 1/3 or roughly less than 2kbytes/sec as you mentioned.

    Lets hear what the team at LPRF have to say.

    Thanks,

  • 0 in reply to Greenja
    TI__Mastermind 23440 points

    Hi,

    Theoretically it should be 3 frames @ 20 bytes per connection event (should be 4, but since the 4th frame in the radio buffer isn't acked Peri->Central, it takes up space until the next event). However, connection events can occur a minimum of 25ms apart when using multiple slaves with our Central. So that means ~2.4kb/s per slave on a good day.

    Best regards,
    Aslak