nRF52832 Extended Advertising Channels

[Sean]

I have a product deployed in production that uses RSSI on BLE advertising channels (37/38/39) to determine rough proximity of beacons to various anchors (scanners). An issue with this system is that there are only three advertising channels and there can be several hundred or more beacons advertising in proximity of a single anchor. This causes bottlenecking and typically the 'louder' beacons seem to stomp on the further away 'quiet' beacons so it could take several minutes before a quieter beacon is ever detected to be in proximity.

I was hoping that with extended advertising I would be able to have the anchor scan all 40 channels for advertisements while the beacons advertised across all 40 channels. It seems that I was mistaken though and the advertising still only happens on 37/38/39 but those can now contain pointers to the remaining channels for the extended data, correct?

I saw the following post in devzone that furthers my suspicion:

https://devzone.nordicsemi.com/f/nordic-q-a/32785/extended-advertising-example

[Susheel Nuguru]

Hi Sean,

You are partly correct.

The ADV_EXT_IND type packets needs to be transmitted only in the primary channels (37,38 and 39) but AUX_ADV_IND (Auxillary type) can be transmitted in the secondary. If your aim is to reduce the congestion, then you should transmit a minimal possible in the primary channels and try to stay more on the secondary channels. 

In short, you are right the the start of the advertising event starts on primary channels, but that does not mean that you need to stay on them all the time.

[Sean]

If my goal was to goal is to utilize more bandwidth for advertisements but the advertising message is only initiated in 37/38/39, then extended advertisements don't do it for me. Especially since the standard advertising data packet is plenty for my application. Thanks for your confirmation.