Mesh Long Range mode relaying

RE: Mesh Long Range mode relaying

Chris_Dev — Fri, 06 Sep 2019 08:54:30 GMT

Ah okay, thanks Edvin, that clears it up:)

RE: Mesh Long Range mode relaying

Edvin — Fri, 06 Sep 2019 08:46:51 GMT

Well, I can't tell what your application is doing, but if they are transmitting on Long Range (LR), and you receive the message, it means that the radio is listening in LR as well. Since there is only one radio, and you are able to pick up the message even if it is relayed, it means that it is also picked up and relayed on LR. The reasoning behind this is that Bluetooth Mesh uses the radio ~100% of the time, so it is not possible to switch between LR and 1MBPS, like you can in BLE, where you only use the radio in short bursts.

So:

1: Yes.

2: You can e.g. check the TTL (time to live) on the received message. This is a counter that is decremented by one in each relay. If you set the default TTL in main.c by using access_default_ttl_set(5); (not necessarily 5, but whatever value you want, just so you know what it is). Then, on the receiving node, you can add this line in mesh_msg_handle() in access.c:

__LOG(LOG_SRC_ACCESS, LOG_LEVEL_INFO, "TTL: %d\n", p_evt->ttl);

remember to add the LOG_SRC_ACCESS in __LOG_INIT() in main.c:

__LOG_INIT(LOG_SRC_APP | LOG_SRC_ACCESS | LOG_SRC_FRIEND, LOG_LEVEL_DBG1, LOG_CALLBACK_DEFAULT);

And you should be able to see the TTL in the log for the receiver. If it is 5 (the same as you set on the transmitter), it means that the message is received directly, but if it is 4, it means that it is relayed once, and not a direct message from the source.

3: You can change the default number of repeated relays and the number of original message repeats in nrf_mesh_config_core.h. Search for

CORE_TX_REPEAT_ORIGINATOR_DEFAULT

and

CORE_TX_REPEAT_RELAY_DEFAULT.

Best regards,

Edvin

RE: Mesh Long Range mode relaying

Chris_Dev — Thu, 05 Sep 2019 16:28:01 GMT

I did a test now with changing the transmit power of the client to - 30dbm, made sure the node cannot interact with both servers at the same time. I can see that the relaying is working... But not reliably. So both server nodes are transmitting at 8dbm,with a 3 meter distance in between. I guess the only way to make it more reliable is to ramp up the retransmit counts, or/and reducing message caching? That could cause a lot of traffic though in a large network though.

Is there perhaps any documentation I can read which explains how the mesh stack performs relaying?

RE: Mesh Long Range mode relaying

Chris_Dev — Thu, 05 Sep 2019 15:04:55 GMT

From this post:

https://devzone.nordicsemi.com/f/nordic-q-a/29813/change-phy-in-mesh/118379#118379

Answer given by Hung Bui

RE: Mesh Long Range mode relaying

awneil — Thu, 05 Sep 2019 15:02:43 GMT

[quote userid="79444" url="~/f/nordic-q-a/51804/mesh-long-range-mode-relaying"]got this from another post[/quote]

What post? Give a link.