What are the factors that influence the duration for which distance measurement will occur (Using nrf_dm sample).

[Madan C]

Hello, guys,

I am working on distance measurement project using two nRF5340DK (nrf_dm sample application). I found duration for which the distance measurement between two DKs happens is random, so can I please know the factors effect this duration and also can we control this duration in code.

Also, can we control interval time between two distance measurements in code.

Regards,
Madan

[Simonr]

Hi

Can you upload a log file of this occurring so we can take a closer look at what's going on here. Also, how long is the duration of distance measurements approximately at closer distances compared to the other ones? 

As per the ReadMe of the Distance measurement sample, the best way to adjust the number of measurements performed in a given time depends on the following factors:

• Advertiser settings
• Scanner settings
• Extended size of measurement window "extra_window_time_us"

"The shorter the advertising interval, the higher the frequency at which the broadcaster sends out advertising packages.

This leads to a higher probability of synchronization and to a higher number of measurements taken at a given time.

It also decreases the latency for the first measurement when the device is turned on or comes in reach.

However, the higher number of packets transmitted also results in higher power consumption.

The scan interval and scan window parameters determine how often and how long the scanning device will listen for packets.

Like the short advertising interval, these values also have an impact on power consumption and the ranging frequency of devices.

After the first measurement, the :kconfig:option:`CONFIG_DM_MIN_TIME_BETWEEN_TIMESLOTS_US` and the :kconfig:option:`CONFIG_DM_TIMESLOT_QUEUE_COUNT_SAME_PEER` Kconfig options define how often the same device is measured again.

The Kconfig options :kconfig:option:`CONFIG_DM_TIMESLOT_QUEUE_COUNT_SAME_PEER` and :kconfig:option:`CONFIG_DM_TIMESLOT_QUEUE_LENGTH` define how many measurements are scheduled.

The more measurements are scheduled, the more of them take place, which increases power consumption but gives more frequent rangings.

If the :kconfig:option:`CONFIG_DM_TIMESLOT_RESCHEDULE` Kconfig option is disabled, the next timeslot for measurement execution will be allocated after the measurement request is added using the :c:func:`dm_request_add` function.

Extending the measurement window increases the probability of measurement success for coarse synchronization.

However, it affects the turn-on time of the radio and thus, power consumption.

At the application runtime, the additional delay of measurement execution is configured using the ``start_delay_us`` parameter of the :c:struct:`dm_request` structure.

This option helps in adjusting the synchronization.

The :kconfig:option:`CONFIG_DM_INITIATOR_DELAY_US` Kconfig option defines the initiator delay.

Increasing the values of these parameters increases the latency and power consumption."

Best regards,

Simon

[Madan C]

CASE 1: Actual distance is 1 meters.

*** Booting nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
Starting Distance Measurement example
I: HW Platform: Nordic Semiconductor (0x0002)
I: HW Variant: nRF53x (0x0003)
I: Firmware: Standard Bluetooth controller (0x00) Version 45.41337 Build 3074452168
I: Identity: C7:A4:6E:3F:86:75 (random)
I: HCI: version 6.0 (0x0e) revision 0x206b, manufacturer 0x0059
I: LMP: version 6.0 (0x0e) subver 0x206b
DM Bluetooth LE Synchronization initialization

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.22 ifft=1.34 phase_slope=1.58 rssi_openspace=1.78 best=1.34

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.27 phase_slope=1.63 rssi_openspace=1.78 best=1.27

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.24 ifft=1.17 phase_slope=1.50 rssi_openspace=1.78 best=1.17

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.43 phase_slope=1.51 rssi_openspace=1.78 best=1.43

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.37 ifft=1.44 phase_slope=1.51 rssi_openspace=2.00 best=1.44

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.44 phase_slope=1.41 rssi_openspace=2.00 best=1.44

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.38 ifft=1.42 phase_slope=1.44 rssi_openspace=2.00 best=1.42

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.33 ifft=1.39 phase_slope=1.51 rssi_openspace=2.00 best=1.39

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.36 phase_slope=1.47 rssi_openspace=2.51 best=1.36

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.38 phase_slope=1.50 rssi_openspace=1.78 best=1.38

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.41 phase_slope=1.47 rssi_openspace=2.00 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.41 phase_slope=1.52 rssi_openspace=2.82 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.35 ifft=1.42 phase_slope=1.50 rssi_openspace=2.00 best=1.42

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.43 phase_slope=1.49 rssi_openspace=2.00 best=1.43

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.37 ifft=1.42 phase_slope=1.48 rssi_openspace=2.00 best=1.42

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.33 ifft=1.40 phase_slope=1.44 rssi_openspace=2.00 best=1.40

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.41 phase_slope=1.54 rssi_openspace=2.00 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.33 ifft=1.46 phase_slope=1.55 rssi_openspace=2.00 best=1.46

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.45 phase_slope=1.54 rssi_openspace=2.00 best=1.45

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.33 ifft=1.42 phase_slope=1.46 rssi_openspace=2.00 best=1.42

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.41 phase_slope=1.51 rssi_openspace=2.24 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.39 phase_slope=1.54 rssi_openspace=1.78 best=1.39

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.38 phase_slope=1.47 rssi_openspace=2.24 best=1.38

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.35 ifft=1.41 phase_slope=1.52 rssi_openspace=2.00 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.34 ifft=1.42 phase_slope=1.51 rssi_openspace=2.24 best=1.42

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=1.38 phase_slope=1.49 rssi_openspace=2.00 best=1.38

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.45 ifft=1.41 phase_slope=1.47 rssi_openspace=2.00 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: crc fail
        Distance estimates: mcpd: high_precision=nan ifft=1.40 phase_slope=1.59 rssi_openspace=2.00 best=1.40

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=0.00 ifft=1.38 phase_slope=1.53 rssi_openspace=2.24 best=1.38

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.34 ifft=1.41 phase_slope=1.49 rssi_openspace=2.00 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.31 ifft=1.40 phase_slope=1.51 rssi_openspace=1.78 best=1.40

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.34 ifft=1.41 phase_slope=1.50 rssi_openspace=2.24 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.35 ifft=1.43 phase_slope=1.52 rssi_openspace=2.00 best=1.43

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.33 ifft=1.41 phase_slope=1.51 rssi_openspace=2.24 best=1.41

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=1.35 ifft=1.42 phase_slope=1.51 rssi_openspace=2.24 best=1.42

CASE 2: Actual distance is 5 meters.

*** Booting nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
Starting Distance Measurement example
I: HW Platform: Nordic Semiconductor (0x0002)
I: HW Variant: nRF53x (0x0003)
I: Firmware: Standard Bluetooth controller (0x00) Version 45.41337 Build 3074452168
I: Identity: C7:A4:6E:3F:86:75 (random)
I: HCI: version 6.0 (0x0e) revision 0x206b, manufacturer 0x0059
I: LMP: version 6.0 (0x0e) subver 0x206b
DM Bluetooth LE Synchronization initialization

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=6.55 phase_slope=7.85 rssi_openspace=10.00 best=6.55

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=6.82 phase_slope=8.82 rssi_openspace=12.59 best=6.82

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=5.57 phase_slope=7.64 rssi_openspace=11.22 best=5.57

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=5.27 phase_slope=7.36 rssi_openspace=7.08 best=5.27

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=6.15 phase_slope=7.98 rssi_openspace=10.00 best=6.15

CASE 3: Actual distance is 8 meters:

*** Booting nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
Starting Distance Measurement example
I: HW Platform: Nordic Semiconductor (0x0002)
I: HW Variant: nRF53x (0x0003)
I: Firmware: Standard Bluetooth controller (0x00) Version 45.41337 Build 3074452168
I: Identity: C7:A4:6E:3F:86:75 (random)
I: HCI: version 6.0 (0x0e) revision 0x206b, manufacturer 0x0059
I: LMP: version 6.0 (0x0e) subver 0x206b
DM Bluetooth LE Synchronization initialization

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=8.20 phase_slope=10.49 rssi_openspace=12.59 best=8.20

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=9.67 phase_slope=10.71 rssi_openspace=14.13 best=9.67

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=4.98 phase_slope=9.35 rssi_openspace=39.81 best=4.98

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=8.79 phase_slope=10.75 rssi_openspace=14.13 best=8.79

Measurement result:
        Addr: D5:3D:F8:47:36:BB (random)
        Quality: ok
        Distance estimates: mcpd: high_precision=nan ifft=8.20 phase_slope=11.28 rssi_openspace=12.59 best=8.20

I have attached the log information above. In above log I have considered three cases (1m, 5m, 8m) and below pasted the respective number of distance values estimated.

Note: I have done the distance measurement in office environment.

1.Could you please explain the reason for the varying number of distance values depending on the distance? Additionally, is it possible to make this number uniform, or is it left to the developer’s decision to determine the number of values?

Thanks,

Regards,
Madan