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CCS/CC1310: Choosing correct LBT RSSI treshold

Slev1n
Genius 5680 points
Part Number: CC1310

Tool/software: Code Composer Studio

Hey guys,

we use SDK 3.2 for CC1310 and SDK 3.3 for CC1352R1. We use the sensor collector/example. I found in mac_settings.c the structures fc_CMD_PROP_CS_t RF_cmdPropCsSlotted AND RF_cmdPropCs 

with .rssiThr = -83

For the ETSI certification EN300220v3 it is stated that the threshold should be "15dB above RX sensitivity". The datasheet of the CC1310 states for the LRM with 5kpbs an RX sensitivity of -119dB and -120dB for CC1310 and CC1352R1, respectively.

1. Can I use ApiMac_attribute_rssiThreshold for CC1310 and CC1352R1 to alter the threshold at startup or always?

2. Do I correctly interpret the certification "rule" so that we could set the threshold to -100dB? This could be useful, since our tests showed an message RSSI of -50 to -100dBm.

Any comments welcome

Slev1n

  • 0
    TI__Mastermind 23536 points

    Hello, Slev1n,

    The radio settings in the mac_Settings.c are overwritten once you configure the network with your preferred parameters, no need to worry about this, most of those are for initializing the structs.

    1. Can I use ApiMac_attribute_rssiThreshold for CC1310 and CC1352R1 to alter the threshold at startup or always?

    this attribute should Ideally be chanegd at startup, but I do not see a problem with modifying it after starting up the network.

    2. Do I correctly interpret the certification "rule" so that we could set the threshold to -100dB? This could be useful, since our tests showed an message RSSI of -50 to -100dBm.

    I am not an expert in certification, if you want a better interpretation I recommend you post a a thread with this question alone, and no 15.4stack dependencies on the title or body, this will ensure that one of our experts in certification helps you.

    That being said, I believe that when it says "RX sensitivity" It refers to the sensitivity of the device/radio. If you look at our datasheet you will see the rated sensitivity for specific PHY  settings. This means that you would set it for -104dB and -105dB respectively. 

    I think this is already taken care of by the stack.

     

     

  • 0 in reply to AB
    Genius 5680 points

    Thank you for your answers.

    AB said:
    I am not an expert in certification, if you want a better interpretation I recommend you post a a thread with this question alone, and no 15.4stack dependencies on the title or body, this will ensure that one of our experts in certification helps you.

    Should I still post in SubGHz or another forum?

    AB said:
    I think this is already taken care of by the stack.

    Would you mind verifying that somehow? Then, I could drop the topic.

    best wishes

    Slev1n

  • 0 in reply to Slev1n
    TI__Mastermind 23536 points

    Hey Slev1n,

    If we were not in Quarantine, I would have walked over to the cert people and asked before replying. But due to this, I think it is best if you post in the sub 1 forum as the answer will be faster and by the most relevant expert.

    Sorry,

    AB

  • 0 in reply to AB
    TI__Guru**** 317180 points

    Looking at 

    Section 5.21.2.2 sets the CCA limits. Note that the limit has to be adjusted accordingly to the antenna gain. Also note that the sensitivity level is given by table 32 and not the datasheet. 

    From this it should be possible to calculate the CCA threshold based on the settings/ board you are using. 

  • 0 in reply to TER
    Genius 5680 points

    Thank you both for your help. With an antenna gain of 4dB and a receiver bandwith of 34kHz (SLR mode and 5kpbs for CC1352R1). We have an external antenna with gain of 4dB.

    Sp = (10 * log BW - 117dBm) + 15dB + AntennaGain = -101.67dBm + 15 dB + 4dB = - 82.7dBm (not sure if it can be calculated that simply due to different units?!)

    The CCA threshold is -83dBm, I am having trouble to interpret the word "exceeding" correctly in this case. I would say, that - 80dBm as a threshold would exceed (mathematically being closer to 0) the limit and -90dBm would be below (farther away from 0) the limit and thus be allowed. In terms of being a "polite" device I think my argumentation is correct, because a device stopping to transmit if the channel is occupied with a -90dBm strong signal is "politer" than a device only stopping if the channel occupation strength is above -80dBm.

    Is my interpretation of the formula and the term "exceeding" correct? Than we could keep the threshold.

    best wishes

    Slev1n

  • 0 in reply to Slev1n
    TI__Mastermind 23536 points

    Hey Slev1n,

    I am sorry this has taken so long. I think TER would be best to answer this question.

    Do you still need this to be answered?

  • 0 in reply to AB
    Genius 5680 points

    Hey AB,

    yes, I would really like to understand this topic.

    best wishes

    Slev1n

  • 0 in reply to Slev1n
    TI__Mastermind 23536 points

    Hello Slev1n,

    I would like to help you here, I reached out to multiple HW/RF experts internally and the general consensus is to "He should take this with the lab doing the certification."

    Regards,

    AB

  • 0 in reply to AB
    Genius 5680 points

    Thank you AB.

    We will start our tests in few weeks and will get in touch with the lab. I am pretty sure they will help us to get through certification.

    best wishes

    Slev1n