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IOT advertisements without an RSSI

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  • 1.  IOT advertisements without an RSSI

    Posted Dec 28, 2021 06:06 PM
    Two questions, really:

    I'm decoding IOT advertisements and I see a bunch of updates that don't have any RSSI with them.  Why is that?  It seems like they should always have an RSSI, as the RSSI would be from the point of view of the receiver (the AP) rather than the content of the advertisement.

    seen,mac=d510fe5ca275,reporter=fc7ff1c0fd38 event="update" 1640732668000000000
    seen,mac=e4856ed57e79,reporter=fc7ff1c0fd38 event="update" 1640732642000000000
    seen,mac=ffa40fe23ea3,reporter=fc7ff1c0fd38 event="update" 1640732669000000000
    seen,mac=f079592ebac3,reporter=fc7ff1c0fd38 event="update",rssi=-82i,rssiMethod="smooth" 1640732700000000000
    seen,mac=dc8ffb68a2dc,reporter=fc7ff1c0fd38 event="update",rssi=-67i,rssiMethod="smooth" 1640732700000000000
    seen,mac=c1fa9be1e8e0,reporter=fc7ff1c0fd38 event="update" 1640732667000000000

    2) I get occasional telemetry messages with a Reporter but no Reported.  What does this mean?  If there's nothing to report, why does it send anything at all?  This one I figured out.  It happens when there is no 'known' report type (like iBeacon) and the raw advertisement appears in the bleData field.  The GAP specification tells you how to decode this advertisement yourself.

    Christopher Piggott

  • 2.  RE: IOT advertisements without an RSSI

    Posted Dec 29, 2021 09:58 AM
    I figured a few things out.

    First, if there is only BleData, then the RSSI is in there.  That makes sense.

    Second, I get a lot of 'updates' (Bevent.Event == "update") that have basically a MAC address and a timestamp, and nothing else.  I'm still not 100% sure what these are.  Is the AP just saying "I still see aa:bb:cc:dd:ee:ff and its data/rssi are exactly the same as the last time I reported them" ?

    Christopher Piggott

  • 3.  RE: IOT advertisements without an RSSI

    Posted Jan 04, 2022 03:36 AM
    Hi Christopher,

    Please check the following documentation for some more explanations I have created for my Andorid demo app simulating an IoT server.

    In case of BLE data reports are forwarded in real-time. Every time an advertisement or scan-repsonse is received by the AP it will be forwarded to the server inluding RSSI. 

    BLE telemetry works differently. Here the AP reports all BLE devices it has its BLE table. If the AP hasn't seen an advertisement in the last update report interval, there might be not RSSI value. 
    Check the APs BLE table to see if "last seen" timer increases or is reset for your BLE devices.

    In order to remove BLE devices that are no longer seen by an AP form its reports, you have to enable the "age filter". Please take a look here for details: BLE data filter



    Jens Fluegel