Connection fail in a noisy environment

[Cake Huang]

Hi Team,

I am using nRF52832 to implement smart watch product and it is now close to PP stage.

Currently our product testing engineer found that in a relative noisy environment, say there are several tens of wear product which is typical place for our testing,there is a much higher possibility that the phone could not connect to the target watch.

My question is that is this a drawback of BLE?

From my understanding regarding the connection set up process in the BT spec, the scanner which is the phone, would send the connection indication packet immediately after it sees the advertisement packet coming from the exact advertiser that the phone wants to connect. Once this is done, the phone would try to send first data packet within some time(like transmit window size plus window offset) to set the archor point. If the wear device responds with data PDU then the connection is set up correctly.

From above process, what I saw is that there is only one  connection indication packet sent once. No resend or retry....What if this  connection indication packet was broken due to the noisy environment? 

Hope to get more clarification on this.

Thanks.

[run_ar]

From above process, what I saw is that there is only one  connection indication packet sent once. No resend or retry....What if this  connection indication packet was broken due to the noisy environment? 

This is a weakness with the ble protocol. If this happens the phone will try to send 6 packets after the connection request before it times out and will have to try to connect again.

How many advertisers are we talking about here? do you have multiple scanners as well? Usually having multiple active scanners in an area would be much worse than having a lot of advertisers. The scanners would pick up the same advertisement packet and sends scan requests to the peripheral at the same time as the connection request is sent to establish a connection (There is some backup routine, but not sure if it's good enough). Passive scanners would be fine.