Radio occupation timings

[Simsim]

Hi NordicTeam

i am working with the Mesh Dimming server example out of the SDK MESH 5.0.0.

While investigation the Packet loss in my prevous ticket i was wondering if you have a diargam or explaination for the Magic Numbers you set in the different parameters.

Especialy:

nrf_mesh_config_core.h

MESH_GATT_PROXY_NETWORK_ID_ADV_INT_MS 2000

MESH_GATT_PROXY_NODE_IDENTITY_ADV_INT_MS 200

MESH_GATT_PROXY_NODE_IDENTITY_DURATION_MS 60000

nrf_mesh_config_bearer.h

BEARER_ADV_INT_DEFAULT_MS 20

BEARER_SCAN_INT_DEFAULT_MS 2000

BEARER_SCAN_WINDOW_DEFAULT_MS 2000

As far i could find out what is happening:

MESH_GATT_PROXY_NETWORK_ID_ADV_INT_MS 2000 -> Advertises all 2s the Gatt service for mobile device

BEARER_SCAN_INT_DEFAULT_MS 2000 -> interval of 2s with window lenght of 2s? so far i woud assume there is no time left for other advertisements

BEARER_SCAN_WINDOW_DEFAULT_MS 2000

Are there further parameter who should match the configuration as it seems quite critical in this coexistence case?

Do you have a ocupation graphic or similar to determine the right paramters?

Regards

Sim

[Amanda Hsieh]

Hi, 

Please be aware that the nRF5 SDK for Mesh is in maintained mode. We encourage users to transition to nRF Connect SDK.

 

MESH_GATT_PROXY_NETWORK_ID_ADV_INT_MS 2000

 Arbitrary choosen value as a compromise between power consumption and usability (being able to connect to the device). This value can be big as Network ID advertisements are not limited in time unlike Node ID advertisements (see below).

 

MESH_GATT_PROXY_NODE_IDENTITY_ADV_INT_MS 200

 This adv interval is short on purpose as the duration of the Node ID advertisements are limited (see the next option).

 

MESH_GATT_PROXY_NODE_IDENTITY_DURATION_MS 60000

 Duration of Node ID advertisements. This is maximum and default value defined by spec (see section 7.2.2.2.3 of MshPRTv1.1).

 

BEARER_ADV_INT_DEFAULT_MS 20

 Lowest possible adv interval defined in  the Bluetooth Core Specification Version 5+, Volume 6, Part B, in Section 4.4.2.

 

BEARER_SCAN_INT_DEFAULT_MS 2000
BEARER_SCAN_WINDOW_DEFAULT_MS 2000

 These parameters basically define how long (BEARER_SCAN_WINDOW_DEFAULT_MS) the scanner will stay on a particular channel and how often (BEARER_SCAN_INT_DEFAULT_MS) the scanner will jump from one to another channel. They must be equal to reach 100% scanning duty cycle. There are many reasons why these values should be small. In short, this guarantees a higher probability of capturing messages. Higher values can cause poor performance due to high risk of collision of advertisemts. With shorter values a device can quicker switch to a next channel and catch retransmission of a packet.

 

Advertises all 2s the Gatt service for mobile device

 Yes

 

interval of 2s with window length of 2s? so far they would assume there is no time left for other advertisements

 There will always be a chance for advertisements (for both kind of advs: for mesh advs and for GATT advs). The rest available radio time will be occupied by the scanner.

Regards,
Amanda H.