Acknowledged message re-transmit time

[richardjallen]

Hi,

I'm currently investigating the Bluetooth mesh using the SDK for mesh alpha 0.10.0, I was wondering about the limitations on the re-transmission of messages. The current equation for calculating the re-transmit of messages is as follows,

uint32_t interval = (ttl * ACCESS_RELIABLE_HOP_PENALTY) + ACCESS_RELIABLE_INTERVAL_DEFAULT;

this is doubled every time a packet is acknowledged until the timeout period (set at 30s by the Bluetooth spec) using:

m_reliable.pool[i].interval *= ACCESS_RELIABLE_BACK_OFF_FACTOR;

where ACCESS_RELIABLE_BACK_OFF_FACTOR is set to 2.

Does the Bluetooth spec limit the back off factor at 2 or can it be reduced to increase the rate of re-transmission?

Alternatively, could the ACCESS_RELIABLE_HOP_PENALTY or ACCESS_RELIABLE_INTERVAL_DEFAULT be reduced or again does the Bluetooth spec require this to be set the same as the BEARER_ADV_INT_DEFAULT_MS?

Will this also be affected by the Radio Equipment Directive (RED) 2014/53/EU requiring efficient use of the radio spectrum?

Thanks,

Richard

[ketil]

Hi,

The Bluetooth Mesh specification does not put a limit on the re-transmission of messages and you are free to change all of the values to suit your application*. The default values in the SDK are likely to work well in most scenarios.

*Mesh Profile Specification 1.0 Section 3.7.5.2 Acknowledged message

I recommend you ask Bluetooth SIG regarding the EU directive.

Ketil

[richardjallen]

Thanks for the answer,

Richard