Scan response packet sent by beacon without any scan request

RE: Scan response packet sent by beacon without any scan request

Stian Røed Hafskjold — Thu, 01 Dec 2016 11:42:06 GMT

Okay, I guess that explains it! Thanks.

RE: Scan response packet sent by beacon without any scan request

Jusang Kim — Thu, 01 Dec 2016 02:51:02 GMT

Hello Stian

Finally i got the answer from ellisys about the above problem as follows;

"an hypothesis is that the scan request is not seen by the sniffer because of an interference, or because the packet is out of the sniffer sensitivity range. A typical BLE radio with single channel of 1-2MHz has a larger sensitivity than the sniffer, as the sniffer has a wideband radio with 80MHz of bandwidth. "

Thank you.

RE: Scan response packet sent by beacon without any scan request

Stian Røed Hafskjold — Fri, 11 Nov 2016 10:07:17 GMT

We have an Ellisys in our office too, and we are very satisfied with it. I can't recall to have seen this error before. But as you say, if the receiver sensitivity on the Ellisys is lower than that of the advertising device, the advertiser might receive scan requests that the Ellisys misses.

Nice, please let me know when you get the answer from Ellisys, thanks.

RE: Scan response packet sent by beacon without any scan request

Jusang Kim — Fri, 11 Nov 2016 06:26:06 GMT

One more.... I asked Ellisys how to display the scanner's device address in the scan response when Ellisys does not receive the corresponding scan request. As soon as i get the answer from the Ellisys, I'll let you know.

RE: Scan response packet sent by beacon without any scan request

Jusang Kim — Fri, 11 Nov 2016 04:52:19 GMT

Thank you for your replay again. It makes me energetic to figure the problem out now.

Anyway, i still meet the error in wireless office environment. It is easy to reproduce the error in wireless office environment. It seems like the Ellisys display the previous scanner's address when it does not receive the scan request. And i believe that the receiver sensitivity performance of the Ellisys is poor. Those two things makes this kind of error on Ellisys. It is my guess. If we use the wired test environment then we can solve what the problem is correctly. What's your opinion on this ?

RE: Scan response packet sent by beacon without any scan request

Stian Røed Hafskjold — Thu, 10 Nov 2016 12:24:59 GMT

hmm.. that's a mystery. If the Ellisys does not receive the scan request, it can't possibly know which one is the receiver. Even if there was a bug in the Softdevice that caused the nRF to transmit a scan response without getting a request first, this packet would not contain any recipient information, so the Ellisys would not know which one is the receiver.

I think the only solution to this is that the Ellisys caches the scanner address and uses this as the address when it reports the recipient of the scan response, and that the cached address is not changed until it gets a scan request from another scanner. So I still believe that this is a scan response meant for another scanner that is filtered out.

Are you consistently getting this error? Do you still see this if you turn of the address filtering?

RE: Scan response packet sent by beacon without any scan request

Jusang Kim — Wed, 09 Nov 2016 10:27:27 GMT

Thank you for reply. Yes I do filtered only two interesting devices such as D84E4EE1CDF9 and 4AF1E34BA0C2 . But Please take a look the attached picture. And find out the blue colored area which captured the scan response packet. The scan response is for scanner 4AF1E34BA0C2 as you can see. This is waht i am curious about. Ellisys bluetooth analyzer did not capture the scan request from the scanner 4AF1E34BA0C2 on the attached picture. but how does the Ellisys bluetooth analyzer know that the scan response is for the scanner 4AF1E34BA0C2 ?

RE: Scan response packet sent by beacon without any scan request

Stian Røed Hafskjold — Wed, 09 Nov 2016 10:14:55 GMT

Since you are filtering on the two devices D84E4EE1CDF9 and 4AF1E34BA0C2, maybe the scan request is not shown in the list if the scan request comes from another scanner that is filtered out?