Channel Sounding Performance Metrics#
Accuracy#
Note: The accuracy performance metrics provided on this page are using SiSDK 2024.6.2. They will be updated with results from SiSDK 2024.12.0 GA soon.
Silicon Labs has performed real environment testing in an indoor office setting to best represent the performance of the Channel Sounding distance estimation solution. The images below show the floor map of the office with 6 static devices and one mobile device. The mobile device (H) and one of the static devices (1) are mounted on a ceiling rail robot. All devices used in the tests are the BRD4198A boards.
The table below provides the performance metrics of PBR and RTT distance estimation based on measurements taken at multiple distances between 0.5 m and 34 meters, and in different measurement configurations:
Conducted, line-of-sight (LOS), and non-line-of-sight (NLOS) environments
SL_RTL_CS_ALGO_MODE_REAL_TIME_BASIC and SL_RTL_CS_ALGO_MODE_STATIC_HIGH_ACCURACY algorithm modes referenced by Real-time and Static respectively
Measurement configuration | 90th percentile of abs error (m) | 95th percentile of abs error (m) | Std of the signed error (m) | Mean Signed Error (m) | ||
|---|---|---|---|---|---|---|
Conducted | PBR | Static | 0.06 | 0.06 | 0.01 | -0.05 |
Real-time | 0.06 | 0.06 | 0.01 | -0.05 | ||
RTT | Real-time | 1.13 | 1.16 | 0.64 | 0.2 | |
LOS | PBR | Static | 0.22 | 0.61 | 0.26 | 0.01 |
Real-time | 0.28 | 0.32 | 0.13 | 0.14 | ||
RTT | Real-time | 3.95 | 4.92 | 0.88 | 2.81 | |
NLOS | PBR | Static | 3.59 | 5.01 | 2.2 | -0.7 |
Real-time | 4.25 | 5.09 | 2.02 | 1.81 | ||
RTT | Real-time | 14.76 | 15.5 | 4.04 | 6.4 | |
The following Cumulative Distributive function (CDF) plots show the probability of the absolute distance errors in each measurement configuration.
CDF in Conducted Environment
In the conducted test setup, the antenna paths of 2 BRD4198A boards are connected via a RF coaxial cable with attenuation added to the signal path.
CDF in LOS Environment
CDF in NLOS Environment
Note that Channel Sounding is still in the development phase and software improvements are made in each software release to improve the performance of both PBR and RTT modes. See Known Issues and Limitation section for more information.
Update Rate#
The measurement update rate of channel sounding is affected by the chosen channel sounding procedure interval, number of connections, connection interval, number of antenna paths, PHY, and the number of channels used for channel sounding.
The table below provides the performance metrics of PBR update rate using the out of the box configurations of the SoC Initiator and SoC Reflector examples, for a single connection.
Reference board | Number of Antenna Paths (NAP) | Number of channels | Update rate (Hz) | Calculation time (ms) |
|---|---|---|---|---|
BRD4198A | 1 | 72 | ~6 | ~46 |
37 | ~8.9 | ~10.5 | ||
20 | ~10.2 | ~3.8 |
Note that, by default, the examples use 2M PHY for connection, a 7.5 ms connection interval and the initiator is run at 80 Mhz. Additionally, the maximum CS procedure count is set to 1, meaning that only one CS procedure is scheduled by the controller at a time, and the application restarts a new procedure sequentially. While this approach provides better flow control and stability, it is not optimal for measurement update frequency. By setting the max CS procedure count to 0, CS procedure interval to 12, it is possible to achieve measurement frequency upto 10 Hz using single antenna path and 72 channels.
Optimizing Performance#
The antenna of a device plays a significant role in achieving accurate distance estimations based on its characteristics such as group delay, radiation pattern, and others. To learn more about the antenna design guidelines and considerations to improve the accuracy of distance measurement using Channel Sounding, see AN1493.