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CC2642R-Q1: Mechanism to handle the RSSI in PEPS system

Albin Zhang
Expert 6060 points
Part Number: CC2642R-Q1


Hi, 

The question is about the PEPS system. 

Customer found an issue. the RSSI (central and satellite nodes) will increase/decrease the RSSI suddenly during the phone moves. It impacts the ranging output. 

Evidence  prove the Phone increase/decrease the BLE TX power under control. looks it is a TX power tuning based on the signal strength received by the phone. 

 

Is there any suggestion for this ranging issue? 

Can any signaling over the air have this indicator to info car BLE to know the TX power steps?

BR. Albin

  • 0
    TI__Mastermind 40430 points

    Hi Albin,

    I'm having a tough time reconciling the ask here. Are you saying that the suspicion is that the phone is dynamically changing it's TX power? What phone model? 

    Is the phone moving when this occurs or not moving when this occurs?

    If the phone is doing this, it is not something we can influence. In Bluetooth 5.3, LE Power Control was released which does allow for dynamic TX power adjustment based on RSSI, but for car access, this will not be useable because the RSSI will always be within a defined range if that were to be enabled. 

    How sure are you that it's the phone changing the TX power and that there are not changing multipath reflections or something? Is this seen in a controlled RF environment? 

    At the end of the day, this doesn't seem like a TI issue, so I am limited into what more I can provide to you today. 

  • 0 in reply to Evan W
    TI__Expert 6060 points

    Hi Evan, 

    Customers (two of our key customers reported it in two weeks, maybe cause by a SW update, e.g. LE power control) mentioned it is Huawei phone, looks it gives bigger step of TX power change, so it was found by customer. other phones might have similar mechanism, maybe the steps is small, so didn't reported before. 

    the 6 nodes (Central + 5 satellite nodes) change the RSSI in the same time in one frame (about 5dB). I also asked customer to replace the phone with a Central role Keyfob （TI's CC2642 inside), it can't be reproduced after change. So, it shouldn't be a Multipath/Fading issue caused by environment. 

    I know it is not TI's issue, but just consults if we have some suggestion or if there is signaling indicator over the air if it is SIG standard. 

    BR. Albin

  • +1 in reply to Albin Zhang
    TI__Mastermind 40430 points

    Albin,

    All i can say is that if a phone is dynamically changing their TX power in accordance to LE Power Control - they should not be dynamically changing the TX power because we will explicitly say during the LLCP Features Exchange that power control is not supported by our device as this would be against the specification.

    If the phone is changing the TX power on their own prerogative, outside of the the Bluetooth spec, then this needs to be addressed directly with the manufacture of the phone and how it impacts their application. We don't have any other reports on other phone models showing such behavior.