• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 53 subscribers
  • Views 2234 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Problem with RSSI behavior end it's stability

valerio sblano
Prodigy 210 points
Other Parts Discussed in Thread: CC2541

Hi guys, i'm working on my thesis for a project of indoor positioning.

I've beacons equipped with an cc2541, and i've developed some algorithms for smoothing the rssi value, but i've detected that for examples the mean value of the rssi at 3 meter is lowest of the rssi mean value at 4 or 5 meters.

This behavior makes that i've an error of positioning in the ranging algorithm.

I don't know at this point if the problem is my algorithm or the beacons with that i'm working.

i post some screen of my matlab simulation.

the red line and the circle indicate the rssi value(i have detected 40 rssi for each distance).

the blue line indicate the mean value for each distance.

x-axes is the number of detections and the y-axes represents the rssi value.

the last image is the mean value of each detections.(1 to 15 meter).

So i would know if this behavior is typical of the cc2541 or my beacons don't work well.

  • 0
    TI__Expert 6995 points
    Hi Valerio,
    What you are seeing are probably multipath effects. Please try to change the distance to reflecting surfaces without changing the distance between receiver and transmitter. You can also do that automatically by switching between two different antennas for example.

    Peder
  • 0 in reply to Peder
    Prodigy 210 points
    thanks a lot for your reply.
    i've just tried to change the position without changing the distance between rx and tx, but i've obtained the similar results.
    In some cases i've rssi stable but i'm studing a dynamic environment so its variability is not good.
    so i ask myself if the analysis of rssi value is the right way to definition the position of mobile station in an complex environment.
    I've used two algorithm for smoothing, in the first i've used an median smoothing in the second i've used a smoothing based on gauss model, but in both case i've some problem.
    there is a technic for stabilize the rssi value?
  • 0 in reply to valerio sblano
    TI__Guru 57865 points

    Hey,

    I would device the "distance" into Far, Near and Immediate as I discuss in this Asset Tracking article. RSSI is tough to play around with and if you really want accuracy, you would need antenna diversity (at least one or three extra antennas).

    Best Regards

    Joakim

  • 0 in reply to J Lindh
    Prodigy 210 points

    I appreciate your advice, but I find online beacons with integrated antenna, similar to an043.

    you may possibly recommend a manufacturer of beacons that uses diversity.

    you could show me the summaries rssi obtained with diversity antennas.

    thanks again.