BLE Reliability?

RE: BLE Reliability?

haakonsh — Thu, 18 Nov 2021 12:06:11 GMT

As hugh has commented already the dongle's antenna is not that great, it's optimized for size constraints. Anyhow, the sniffer will not track a single device unless it's in a connection, other than that it will listen to the 3 adv channels as best it can, but it can't listen to all 3 at once.

RE: BLE Reliability?

hmolesworth — Thu, 18 Nov 2021 02:15:37 GMT

You might have a simple range or antenna issue; depending on which side of the laptop the dongles are affects performance; stand in front of one of the dongles and pretty much all transmissions are lost. The reason is a simple printed antenna/ariel on the nRF52840 dongle; using a dongle or (say) Feather with a chip antenna will give hugely improved performance. As a work-around for the dongle, boost transmission power to the max.

See sd_ble_gap_tx_power_set()

RE: BLE Reliability?

jryu — Wed, 17 Nov 2021 14:36:08 GMT

Thank you for your response.

Regarding the 40 channels: But if I am only sending SCAN_REQs they should be only sent through 3 channels right? Shouldn't it still be capable of sniffing them more regularly when it is only three channels?

Anyways, I am very happy with the dongle. As you said it is very cost effective tool.

RE: BLE Reliability?

haakonsh — Tue, 16 Nov 2021 13:08:53 GMT

If the sniffer is not running when a connection is established it can not track the suedo-random hopping algorithm. As it can only recieve on one out of 40 channels at a time it will miss a lot of packets. There is also limit to what the sniffer can pick up even if it is tracking a connection as it cannot make use of the protocols automatic retransmissions when it receives a malformed packet. The nRF Sniffer is an very cost effective tool, but it is not perfect. A proper wide-band BLE sniffer costs 100-400x the price of the nRF52 dongle. The nRF Sniffer can give you a good indication on what's going on on-air, but it can't replace industrial RF analysis equipment.

The BLE protocol itself is incredibly reliable, and able to operate in environments drowned in RF interference. If you want to test the reliability/range of BLE i suggest you run the BLE throughput examples as they will give you real-world numbers on the performance of your link, instead of using the sniffer to count received packets.