How to increase location update rate?

Quick hints

  1. Set the Location update rate to 16+Hz in the Dashboard. The system will reach the update rate ceiling based on other limitations
  2. Disable Realtime Player to reduce additional latency due to it to zero
  3. Set the Window of averaging = 0 and Distance filter = 0. It won’t increase the update rate, but will reduce the latency
  4. Define service zones. If you don’t, the system uses the default service zones of 30m, and the update rate may not be optimal. For example, reducing from 30m to 10m can increase your update rate by up to 3x if it was limited by the submap size, which is often the case. Typically, this is the biggest contributor to the update rate improvement
  5. Change from the default 100/200 kbps radio profile to 500 kbps. You might see an increase if the location update rate is radio-limited. Usually, the increase is smaller than with service zones, or zero if the system isn’t radio-limited. But the radio profile becomes very important in swarm robotics and IA. More about radio connectivity
  6. See the achievable update rates: Marvelmind Indoor Positioning System location update rate and user data transfer rate table. Note that the tables are prepared for 2D submaps – not 3D submaps. More radio traffic and more time slots for 3D data in general typically will lead to a lower update rate in 3D than in 2D. We usually recommend 4 beacons for 3D tracking to have 3+1 redundancy. But if you are more focused on a higher update rate, then 3 stationary beacons in a submap instead of 4 may increase the update rate. The improvement depends on where you are limited. So, do the first steps first
  7. Reduce the number of mobile beacons in NIA, if feasible. The update rate will increase proportionally
  8. Reduce the number of mobile beacons in MF NIA to less than 8, less than 16, etc. The update rate will improve proportionally to int(N/8)
  9. Choose the location update rate for the modem vs. the location update rate for the mobile beacon. If you update the location of every mobile beacon on the modem every time, the location update per mobile beacon will be lower due to higher radio traffic
  10. Consider one or a combination of licenses depending on where you are limited:

Intro

There are several key parameters in any real-time locating system (RTLS) or indoor positioning system (IPS). Among them:

  • Cost (hardware + software + deployment + running, etc.)
  • Accuracy/precision of positioning
  • Location update rate and latency
  • The number of mobile objects tracked

There are many more, and you can learn about them in detail. Let’s discuss deeper the two of them more:

Accurate RTLS for swarm robotics

Notice that location update rate and latency are usually linked but are not the same. For example, simultaneously, you may have a high update rate and high latency.

Also, remember that the accuracy of position measurements doesn’t directly depend on the location update rate. At the same time, if your system can tolerate more latency in the position measurements, it is possible to achieve higher accuracy of measurements. See more: Does accuracy depend on the location update rate?

Location update rate

Location update rate – how many times per second the location has been measured.
For some customers, “fast” means once per minute, for example, for static assets tracking – palettes, etc. Even a 100Hz update rate is barely fast enough for some other tasks – VR/AR and similar.

Typical update rate with default settings with average-sized submap of 10-15m – 8Hz. We support up to 30-40 Hz for very small submaps of 2-3m. For larger maps of 30m and default settings – 6Hz or so.

If you don’t specify the service zone, the submap assumes the largest submap, and you get 6Hz or so.
Notice that we have both location and direction for the Paired Beacons configurations. While the location is measured with a typical update rate of the ultrasound system – 8Hz or so – the direction is calculated based on sensor fusion with IMU. The sensor fusion gives 100Hz update rate for direction and ~10ms latency for it.

Latency

Latency – a delay between the moment the location has been measured and the moment we know the calculated coordinates.
 
Reducing latency is usually a more complex task than increasing the update rate. For example, the Realtime Player is a relatively simple method that improves the update rate x10..x100 times. An architecture or underlying positioning technology could have to be changed to do the same with latency.
 

There is a clear trade-off between latency and accuracy of tracking. By applying more filtering or averaging, it is possible to achieve better tracking quality, but latency will suffer. Thus, each case must choose between accuracy/quality and latency.

More on the adjacent subjects:

IMU+Ultrasound Sensor Fusion Post-Processing

To have real 100Hz tracking, use IMU + Ultrasound Sensor fusion.
 
 

It is particularly suitable for sports (carting, jumping, etc.) and fast machinery.

Further steps

If the typical 8-16Hz location update rate and 100Hz for direction are not enough, what are the other options?
 
  • Please send us a request to info@marvelmind.com. You may not need the high update rate or low latency you think you do. Perhaps there is another solution
  • For swarm drones, MF NIA is the classic option now
  • But for more than 10-16, the update rate that MF NIA provides may already not be good enough. You may need to change to IA instead of MF NIA. Consider: Indoor positioning system for drone shows and swarms
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