Example for setting up BLE long range mesh network between several nodes

RE: Example for setting up BLE long range mesh network between several nodes

Bjørn Kvaale — Tue, 16 Oct 2018 12:42:29 GMT

[quote user="Rostokus"]NRF_SDH_BLE_GAP_EVENT_LENGTH on central is 2 (2.5ms). Thus Central is able to process requests from all three peripherals within one connection interval. Right?[/quote]

Yes, this is correct. See the softdevice specifications for the S140 v6.1 softdevice here (pg 71):

[quote user="Rostokus"]Is it possible to de-solder SWF and solder UFL instead?[/quote]

Yes, but beware that the UFL antenna is not a switch connector (i.e. if the ANT060 is not connected, then the nRF chip will not be connected to the PCB antenna anymore. Basically, if you do not want to use the PCB antenna at all, you can use the ANT060.

RE: Example for setting up BLE long range mesh network between several nodes

Rostokus — Fri, 12 Oct 2018 06:43:25 GMT

I have one central and 3 peripherals. SDK v15.2.
Connection intervals are 7.5ms on central and peripherals.

NRF_SDH_BLE_GAP_EVENT_LENGTH on central is 2 (2.5ms). Thus Central is able to process requests from all three peripherals within one connection interval. Right?

I am testing at home where only WiFi can interference.

I have bought ANT060, but it appeared that NRF52840 DVK has SWF connector instead of UFL on antenna. Is it possible to de-solder SWF and solder UFL instead?

RE: Example for setting up BLE long range mesh network between several nodes

Bjørn Kvaale — Tue, 09 Oct 2018 06:23:41 GMT

What min & max connection intervals are you using on the central side? If you use a low connection interval, you can most likely expect a latency between 0-100 ms when the dev kits are placed next to each other.

If you are following the infocenter documentation & testing with the ble_app_blinky on the peripheral side, you may need to lower the min connection interval to decrease the latency:

#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(100, UNIT_1_25_MS)        /**< Minimum acceptable connection interval (0.5 seconds). */
#define MAX_CONN_INTERVAL               MSEC_TO_UNITS(200, UNIT_1_25_MS)        /**< Maximum acceptable connection interval (1 second). */

Are you using sdk v15.2.0?

This will be independent of the phy you use (e.g. coded, 1 Mbps, 2 Mbps). Are you testing in an environment with a lot of wireless interference by chance? This could lead to increased packet loss, which will impact latency.

An external antenna could decrease latency, but I would try the fix above instead. I am not sure an external antenna would make a huge difference if the dev kits are right next to each other.

RE: Example for setting up BLE long range mesh network between several nodes

Rostokus — Mon, 08 Oct 2018 13:03:25 GMT

I have successfully setup communication between several nodes using the start topology and BLE 5 PHY (1 or 2 Mbps).

The latency is nearly 50-100ms if NRF52840 DVKs lay on the table one near another.

If I try to increase the distance, latency increases. For example, if the distance is 2-3m, latency increases to 250-300ms.

Why is it so? I suspect this is caused by retransmission's due to low single and obstacles.

If I use external antennas (like this), will it help to keep the latency constant?

RE: Example for setting up BLE long range mesh network between several nodes

Rostokus — Fri, 21 Sep 2018 12:21:32 GMT

thanks, Bjorn and David.

I will try to use multilink approach and see the result before switching PHY

RE: Example for setting up BLE long range mesh network between several nodes

Bjørn Kvaale — Wed, 19 Sep 2018 13:27:04 GMT

As David said, you can update to coded phy in mesh, but it would most likely not be qualified if you want to use it in an end product. Regarding communication latency, this should be possible.

RE: Example for setting up BLE long range mesh network between several nodes

David Edwin — Wed, 19 Sep 2018 09:15:13 GMT

You can switch the RF PHY being used in the nRF Mesh SDK from 1Mbit PHY to the coded PHY used in long range.
This will give you the range some usecases seem to prefer.

You can look at this older case to enable the Mesh with coded PHY for longer range.

RE: Example for setting up BLE long range mesh network between several nodes

Rostokus — Tue, 18 Sep 2018 18:40:32 GMT

[quote userid="25682" url="~/f/nordic-q-a/38630/example-for-setting-up-ble-long-range-mesh-network-between-several-nodes/149207"]Bluetooth Mesh is not based on the Bluetooth 5 stack unfortunately[/quote]

Please elaborate on this. Can we use Bluetooth mesh with conjunction with Bluetooth 5?

www.nordicsemi.com/.../nRF5-SDK-for-Mesh

RE: Example for setting up BLE long range mesh network between several nodes

Rostokus — Tue, 18 Sep 2018 11:45:41 GMT

[quote userid="25682" url="~/f/nordic-q-a/38630/example-for-setting-up-ble-long-range-mesh-network-between-several-nodes/149207"] You could then send messages from the peripheral nodes to the central node & let the central node relay those messages to all of the sibling nodes for example.[/quote]

that's a good point, but it will most likely increase the communication latency between peripherals. In my case I would like to achieve up to 100-200ms latency between any nodes. Is it possible with BLE?

RE: Example for setting up BLE long range mesh network between several nodes

Bjørn Kvaale — Tue, 18 Sep 2018 11:40:37 GMT

Bluetooth Mesh is not based on the Bluetooth 5 stack unfortunately. You could take a look at the multilink example, where a central node can connect to 8 other peripheral nodes. You could have a long range connection between the central node & each peripheral node. You could then send messages from the peripheral nodes to the central node & let the central node relay those messages to all of the sibling nodes for example.