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Heavy scanning activity from Android (and iOS) devices might prevent connecting to BLE GAP Peripheral

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Dear Nordic team and community,

Have you encountered the problem where standard BT4.0/4.1 GAP Peripheral device would be "blocked" from connection (kind of "denial of service" situation) by too many actively scanning GAP Scanners/Centrals? We are seeing this with certain mobile phones (especially Android) in "observing" role and this is pretty independent on adv. interval we use (typically 20-200ms). All adv. events are "loaded" with SCAN_REQ packets when there are 5 or more "scanning" phones and beside SCAN_REQ collisions (which are typically not critical for BLE solutions) basically all CONNECT_REQ collide with some SCAN_REQ packet and thus Peripheral never follows the connection.

Any suggestions (beside trying to lower scanning activity on phones' side which obviously isn't always possible)?

Thanks Jan

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  • 0

    Few more things on the issue:

    • It really looks like having any mobile app on mobile which causes heavy active (SCAN_REQ) scanning in GAP Scanner/Central role can take 15-30% of available "slots" (aka RX windows following ADV_IND packets from GAP Peripheral) so at 3-4 devices in the range you wills tart to observe occasional collisions and with 5-6 you will already have big troubles to find any available RX window to start connection.
    • Note that this can be hardly prevented as users can have BT enabled and any application running and you can do very little about it.
    • This would mean that any "dense" areas such as airports, office spaces, rush streets etc. should be full of such "DOS" zones. However there seems to be no such complains so I'm wondering if this "heavy scanning" behavior is limited only to few devices (I've tested Samsung Galaxy S6/7/8) or it happens only...
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  • 0

    Few more things on the issue:

    • It really looks like having any mobile app on mobile which causes heavy active (SCAN_REQ) scanning in GAP Scanner/Central role can take 15-30% of available "slots" (aka RX windows following ADV_IND packets from GAP Peripheral) so at 3-4 devices in the range you wills tart to observe occasional collisions and with 5-6 you will already have big troubles to find any available RX window to start connection.
    • Note that this can be hardly prevented as users can have BT enabled and any application running and you can do very little about it.
    • This would mean that any "dense" areas such as airports, office spaces, rush streets etc. should be full of such "DOS" zones. However there seems to be no such complains so I'm wondering if this "heavy scanning" behavior is limited only to few devices (I've tested Samsung Galaxy S6/7/8) or it happens only...
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