Channel sounding and more antenna paths

RE: Channel sounding and more antenna paths

witc — Sat, 04 Oct 2025 21:57:43 GMT

Hi,

I applied the commit and I have to confirm that this bugfix is very important – now the CS works completely fine. Without it, it was really unusable.

RE: Channel sounding and more antenna paths

Edvin — Wed, 01 Oct 2025 06:17:01 GMT

I am not sure. I usually don't work on the main branch. What build error do you see? Please include the full build log.

I would recommend to use a stable release, such as v3.1.1. The reason is that when you use main, some samples may or may not build, depending on when you fetched the main branch.

So please try to use v3.1.1 (release closest to main that is stable), and then include the the changes in the pull request, or the pull request itself.

Best regards,

Edvin

RE: Channel sounding and more antenna paths

witc — Tue, 30 Sep 2025 14:29:42 GMT

Hi,

Please, can I manually switch to the main branch in the ncs repository? The mentioned commit is already merged in the main. However, when I do that, I can't compile it with the 3.1.1 toolchain - am I doing something wrong?

I switched to commit 560d4f7b09e2b58630a4e8c867f5be068173072e

Then I created new project from sample - RAS initiator.. but build can not be done without errors.. Missed I anything?

The build fails with multiple Kconfig symbol definition errors in the Nordic SDK's Bluetooth controller configuration:

BT_CTLR_EXTENDED_FEAT_SET (Kconfig:538) - Symbol defined without specifying data type
BT_CTLR_SDC_EXTENDED_FEAT_MAX_REMOTE_PAGE
....

RE: Channel sounding and more antenna paths

Edvin — Tue, 30 Sep 2025 10:30:39 GMT

Update:

It may be that the issue you are seeing is related to an issue that is patched in this pull request.

It will likely be merged soon, but you can try to build with NCS v3.1.1, and either cherry pick this pull request, or copy the changes in the commit over to your SDK, and see if that helps:

https://github.com/nrfconnect/sdk-nrf/pull/24778

All users who are attempting to use multiple antenna paths should include this PR.

Best regards,

Edvin

RE: Channel sounding and more antenna paths

Edvin — Mon, 29 Sep 2025 12:10:56 GMT

Hello,

One of the R&D engineers working on channel sounding said that he recently tested this, and seemingly got it working:

https://github.com/nrfconnect/sdk-nrf/commit/f809ae1d0f033eb0603a46330c9ae0b761d0e598

He said that he was testing on main, rather than on NCS v3.1.0 or 3.1.1. I would have tested on v3.1.1, as that is closest to main, but you can also try main if that doesn't work.

The main changes, apart from actually enabling multiple antenna are:

- Increased connection interval

- Increast subevent len to fit all the steps of one procedure in a single subevent (measurements for each channel take more time when they have to be done on multiple antennas).

Best regards,

Edvin

RE: Channel sounding and more antenna paths

Edvin — Fri, 26 Sep 2025 10:20:42 GMT

Hello,

Just wanted to let you know that I have not forgotten your ticket. I forwarded your questions to our R&D, but I didn't hear back from them. I will ping them, and hopefully get back to you soon!

Best regards,

Edvin

RE: Channel sounding and more antenna paths

witc — Fri, 19 Sep 2025 04:58:20 GMT

Hello,

Thank you. I tried your recomendation, but I can not say I see any improvements, I would really like to know where is main problem, also I use internal RC (32kHz) instead of the external one.
There is my settings for 4 AP:

struct bt_le_cs_create_config_params config_params = {
		.id = CS_CONFIG_ID,
		.main_mode_type = BT_CONN_LE_CS_MAIN_MODE_2,
		.sub_mode_type = BT_CONN_LE_CS_SUB_MODE_UNUSED,
		.min_main_mode_steps = 2,
		.max_main_mode_steps = 5,
		.main_mode_repetition = 0,
		.mode_0_steps = NUM_MODE_0_STEPS,
		.role = BT_CONN_LE_CS_ROLE_INITIATOR,
		.rtt_type = BT_CONN_LE_CS_RTT_TYPE_AA_ONLY,
		.cs_sync_phy = BT_CONN_LE_CS_SYNC_1M_PHY,
		.channel_map_repetition = 3,
		.channel_selection_type = BT_CONN_LE_CS_CHSEL_TYPE_3B,
		.ch3c_shape = BT_CONN_LE_CS_CH3C_SHAPE_HAT,
		.ch3c_jump = 2,
	};

const struct bt_le_cs_set_procedure_parameters_param procedure_params = {
		.config_id = CS_CONFIG_ID,
		.max_procedure_len = 2000,
		.min_procedure_interval = realtime_rd ? 5 : 10,
		.max_procedure_interval = realtime_rd ? 5 : 10,
		.max_procedure_count = 0,
		.min_subevent_len = 60000,
		.max_subevent_len = 60000,
		.tone_antenna_config_selection = BT_LE_CS_TONE_ANTENNA_CONFIGURATION_A2_B2,
		.phy = BT_LE_CS_PROCEDURE_PHY_1M,
		.tx_power_delta = 0x80,
		.preferred_peer_antenna = BT_LE_CS_PROCEDURE_PREFERRED_PEER_ANTENNA_1 | BT_LE_CS_PROCEDURE_PREFERRED_PEER_ANTENNA_2,
		.snr_control_initiator = BT_LE_CS_SNR_CONTROL_NOT_USED,
		.snr_control_reflector = BT_LE_CS_SNR_CONTROL_NOT_USED,
	};

and Kconfig:

CONFIG_NCS_SAMPLES_DEFAULTS=y
CONFIG_DK_LIBRARY=y

CONFIG_BT=y
CONFIG_BT_SMP=y
CONFIG_BT_CENTRAL=y
CONFIG_BT_MAX_CONN=1
CONFIG_BT_BONDABLE=n
CONFIG_BT_CTLR_CONN_RSSI=y

CONFIG_BT_GATT_CLIENT=y
CONFIG_BT_GATT_DYNAMIC_DB=y

CONFIG_BT_CHANNEL_SOUNDING=y
CONFIG_BT_RAS=y
CONFIG_BT_RAS_RREQ=y

CONFIG_BT_SCAN=y
CONFIG_BT_SCAN_FILTER_ENABLE=y
CONFIG_BT_SCAN_UUID_CNT=1

# The Ranging Profile recommends a MTU of at least 247 octets.
CONFIG_BT_L2CAP_TX_MTU=498
CONFIG_BT_BUF_ACL_TX_SIZE=502
CONFIG_BT_BUF_ACL_RX_SIZE=502
CONFIG_BT_ATT_PREPARE_COUNT=3
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251

# This reduces RAM usage. Additional RAM is needed to support optional
# features such as mode 3 or multiantenna. Change or remove these if
# using those features
CONFIG_BT_RAS_MODE_3_SUPPORTED=n
CONFIG_BT_RAS_MAX_ANTENNA_PATHS=4
CONFIG_BT_CTLR_SDC_CS_MAX_ANTENNA_PATHS=4
CONFIG_BT_CTLR_SDC_CS_NUM_ANTENNAS=2
CONFIG_BT_CTLR_SDC_CS_STEP_MODE3=n
CONFIG_BT_CTLR_SDC_CS_ROLE_INITIATOR_ONLY=y
CONFIG_BT_RAS_RRSP=y
#CONFIG_BT_RAS_RRSP_AUTO_ALLOC_INSTANCE=y
CONFIG_BT_RAS_RRSP_RD_BUFFERS_PER_CONN=10

# Disabling the CS Test command reduces flash usage
CONFIG_BT_CTLR_CHANNEL_SOUNDING_TEST=n

# This allows CS and ACL to use different PHYs
CONFIG_BT_TRANSMIT_POWER_CONTROL=y

# This improves the performance of floating-point operations
CONFIG_FPU=y
CONFIG_FPU_SHARING=y

CONFIG_CBPRINTF_FP_SUPPORT=y

CONFIG_BT_CS_DE=y
CONFIG_BT_CS_DE_512_NFFT=y

CONFIG_BT_CTLR_TX_PWR_PLUS_8=y

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n
# Enable calibration for internal RC oscillator to improve accuracy
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC_CALIBRATION=y
# Maximum number of skipped calibrations in a row (energy saving)
CONFIG_CLOCK_CONTROL_NRF_CALIBRATION_MAX_SKIP=2

I have RF switch with switching time under 100 nsec: AS179-92LF.

Thank you very much for any advice, Also what about reflector? Anything to check there?

Thanky youvery much. Jan.

RE: Channel sounding and more antenna paths

Edvin — Thu, 11 Sep 2025 10:28:15 GMT

Hello,

From our R&D:

Can you share the rest of your parameters? Adding multiple antenna patsh to the channel sounding means the controller produces more data, which in turn means the devices need to exchange more data over GATT to produce distance estimates. If there isn't enough time to transfer the data before more data is produced, the new data will overwrite the old.

Here are two things to try;

1: Inscrease the procedure interval

2: Increasing CONFIG_BT_RAS_RRSP_RD_BUFFERS_PER_CONN

Also, what antenna switch are you using? Can you verify whether it satisfies the switching time requirement of 6µs?

https://docs.nordicsemi.com/bundle/ncs-latest/page/nrfxlib/softdevice_controller/doc/channel_sounding.html#adding_a_custom_antenna_switch_ic

Best regards,

Edvin

RE: Channel sounding and more antenna paths

witc — Thu, 11 Sep 2025 08:32:59 GMT

Hi Edvin,

How does it look? Would it help if I made a new private ticket on this topic?

Thank you.

RE: Channel sounding and more antenna paths

witc — Mon, 08 Sep 2025 12:07:59 GMT

Great, I hope they will also see the graphs I added a bit later - that could be more intuitive.

RE: Channel sounding and more antenna paths

Edvin — Mon, 08 Sep 2025 11:33:57 GMT

Hello,

I am sorry for the late reply. I have looked at your questions, but I have not tested with multiple antennas before (as we don't have it on our DKs). I have forwarded your question to our SoftDevice Controller team, but have not heard back yet. I will ping them now. I will get back to you as soon as I know more.

Best regards,

Edvin

RE: Channel sounding and more antenna paths

witc — Tue, 02 Sep 2025 20:52:26 GMT

I am adding 2 graphs just for interest. I plot the distance from IFFT for all 4 APs (green if at least one of AP in procedure had CS_DE_TONE_QUALITY_OK / red if == all were BAD - the distance is not updated, it keeps the last valid value). Also, the extracted RSSI is shown in purple.

There are another 2 graphs. One is for 1 AP, another for 4 AP. Yellow line is "real" distance. We can see the 4AP has a lot of red points.
1AP:

4AP: