I developed an iBeacon related app and I want to calculate the exact distance from iBeacon to an Android device. Is there any approach to get the exact distance in meters for Samsung Galaxy J7?
You can't get the exact distance. iBeacon is not designed for.
An approximation of the distance is the more that you can get.
For a beacon that is 5 meters away, distance estimates might fluctuate between 2 meters and 10 meters.
The reasons for these distance estimate variations and the steps that can be taken to reduce them are some of the most frequent questions we get about beacons. Factors that influence the error in the estimate include reflections of the radio signal, obstructions that attenuate the radio signal, and orientation of both the phone and the beacon.
source
Yes. The beacon provider /manufacturer would have their sdk. Use it in your eclipse project and directly you can get the distance in metres. I can send you my code if you want.
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I am developing an android application to find the distance from Eddystone beacon to the mobile device. I am using Android Beacon Library and following this example. when I locate my beacon nearly 1 meter away from my device, it shows like below. it shows small values and changes continuously. How to solve this and get at least nearly accurate value.
The "underestimate" shown in the question suggests one or more of the following may be true:
The Beacon has not been calibrated.
The receiving phone device model may have an unusually high measurement of signal strength requiring a device-specific adjustment of its distance calculation.
See here for more information on how to address these issues.
Even once you address the above, set your expectations properly. Bluetooth LE distance estimates are rough. They are useful for telling you if another device is within a couple of meters or many meters away. But they cannot tell you the precise distance to a bluetooth transmitter.
I'm working on beacon mapping app when a beacon enters in 2 meters range i have to call web service but by using this library it's showing wrong distance if beacon is in 5m range then also it's showing 1.5 something
if (oneBeacon.getDistance() <= 2) {
final String distanceString = String.valueOf(major.toString() +
middle.toString() + minorString.toString());
beaconList.add(distanceString);
}
A few tips:
Understand that beacon distance estimates are very rough and will never be exact. You must set your expectations appropriately. At 1 meter actual distance, estimates of 0.5-2 meters are typical. Obstructions and reflections affect this.
You must calibrate your beacon so that the 1m expected signal level is transmitted inside the packet. This involves measuring the signal level at 1m then spring this "measured power" inside your beacon. Your beacon supplier should provide you with instructions on how to set this.
On Android, a very fragmented hardware base means big variations in Bluetooth chips, antennas and phone cases all of which affect the distance estimate on a device to device basis. If you know your target devices, you can refine the distance formula for these devices. This is a more complex procedure, so only worth doing if (2) does not give you the results described in (1).
How to calculate distance using BLE beacons if the user is moving in a vehicle with 2-15kmph speed?Also,if the distance won't give me accurate results is there any other mechanism with the help of which I can calculate the nearest beacon.The default implementation does not give me proper results as there is a 20sec lag in distance estimates.
Secondly,in which cases should ARMA filter be used.
Beacon distance estimates are only estimates, so you must set accuracy expectations accordingly. In order to reduce noise on radio signal levels, many samples are averaged over a period of time.
Figuring out the appropriate averaging time depends on the use case. As you have noted, the Android Beacon Library uses a 20 second running average by default. This gives a distance estimate based on where the vehicle was on average over the past 20 seconds.
For a vehicle going up to 15km/hour (~5 meters / sec) with a beacon transmission radius of 50 meters, it will be in range of the beacon for a maximum of 10 seconds. How many distance measurements do you need to get? If one is enough, average over 10 seconds. If you need more, set the period even shorter.
Understand that reducing the sample interval will add more noise error to the distance estimates, because you will have fewer statistical samples to work with. A few things you can do to make the most of the samples you do get:
Set the beacon to advertise as frequently as possible. Some beacons advertise at 1Hz or less to save battery. This leads to poor distance estimates. Increase it to 10Hz or more if possible.
Turn off bluetooth configurability/connectability on your beacon. Some Android devices will only allow one signal level sample per BLE scan (1.1 secs by default in the library) in connectable mode. This can lose you 90% of your samples at 10 Hz.
Configure the beacon transmitter to be on its highest power setting and calibrate it properly. Stronger signals have a higher signal to noise ratio, giving better distance estimates.
The ARMA filter uses a nondeterministic sample interval based on % change in each sample. It is more appropriate for use cases with slow moving beacon receivers.
For my project I need to estimate the distance between a Smartphone and a bluetooth module. The Estimation doesn't have to be very precise. I only need to determine the distance with a margin of error of about 50cm.
I did test the RSSI of two bluetooth modules at distance-steps of 10 cm. I measured the RSSI 5 times for each step and got the average of the 5 measurements. The averages are shown in the graph below:
The red and blue lines resemble the two Bluetooth modules. You can see that the results are not very linear. One of the reasons for this is interference, so i searched for ways to tackle the interference issue. Two ways i found are:
Signal Noise Ratio(SNR): Understanding ibeacon distancing
ratio of the iBeacon signal strength (rssi) over the calibrated transmitter power (txPower). The txPower is the known measured signal strength in rssi at 1 meter away: http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Signal-to-noise_ratio.html
However i don't really understand how the above techniques would be used to get more accuracy. For SNR i need the Noise value, how do i even get the Noise value?
For ratio rssi/txPower, I can get the txPower by simply measuring the rssi at 1 meter from the module. So I know all the needed values. But I don't know what to do from here on out. How do i use these values to get a more accurate distance estimations?
Are there any other techniques i can use to improve accuracy?
You are running into the practical limitations on this technology. Getting estimation accuracy of +/- 50 cm may be possible under ideal conditions at short distances (under 2 meters) not at long distances of over 10 meters.
I wrote a longer blog post about the limits here: http://developer.radiusnetworks.com/2014/12/04/fundamentals-of-beacon-ranging.html
To answer your specific questions:
No, there is no practical way to know what part of a single RSSI measurement comes from signal and what part comes from noise. You can take an average over many samples, which partially removes noise if the transmitter and receiver are stationary over the sample interval.
The techniques you ask about do work to give you distance estimate, but they have the limitations of the technology described above.
I have couple of questions regarding the Radius networks Beacon.
How can we get the accurate distance between android devices and
beacon? So far the distance we're getting through
"android-beacon-library" is fluctuating.
How can we limit the beacon's transmission radius, say allowing
beacon to transmit only for 5 meters or to 20 cms ?
Please find the image with beacon distance reading for various devices (Moto g , Nexus 5 , Nexus 4 and iPhone 5s)
You will always see fluctuation on beacon distance estimates, so you have to set your expectations appropriately. Beacon distance estimating works by starting with a measurement of the radio signal strength using the bluetooth radio on the mobile device. A stronger signal means that the beacon is closer, where a weaker signal means the beacon is further away. The beacon transmits a reference value of its expected signal strength at 1 meter, saying in effect "If you are one meter away, you should see my signal level as -56 dBm". A formula inside the mobile phone then tries to make a guess of how far it is away based on the signal level at any given time. If the signal is a little bit weaker than -56dBm, such as -65dBm, the formula might estimate that the distance is 2.5 meters.
This technique is imperfect, and there are several reasons for fluctuation:
There is always background radio noise (like the static on an old AM radio) which causes individual signal strength measurements to vary.
There is error on the analog to digital converter inside the bluetooth radio, which also causes individual signal strength measurements to vary.
The bluetooth radio waves reflect off of some objects and are absorbed by others, making the actual signal strength change at different positions the same distance away, and when other objects in the vicinity move around.
The antenna pattern on both the transmitter and the receiver are not perfectly spherical. This means that when you rotate your phone or the beacon, you will see a slightly different signal level.
There are a few things you can do to minimize the error:
Use a beacon that transmits as frequently as possible, preferably at 10Hz or more. More transmissions mean more statistical samples of the signal level, which when averaged together help mitigate errors from sources 1 and 2 above.
Use as high of a transmitter power setting on your beacon as possible. The stronger the signal, the lower the noise level will be (relatively speaking) from source 1 above.
When possible, place your beacons where there is a clear line of sight to the receiving devices. Overhead often works best.
However, the best you can hope to do is reduce the variation as much as possible. You cannot eliminate it. For this reason, you must design your app so such variation is acceptable. If it helps your use case, you can also lower the beacon transmitter power so that devices only detect the beacon when they are relatively close.
Using Radius Networks' RadBeacon USB and RadBeacon Tag models, you can adjust the transmitter power using the free RadBeacon configuration app for iOS and OSX. The apps have a slider control to increase and decrease the transmitter power.
You should note, however, that by lowering the transmitter power, you will also increase the amount of variation on your distance estimates. This is because the signal to noise ratio will be lower.
Full disclosure: I am Chief Engineer for Radius Networks.
you can't really tell the distance to one beacon. That's why indoor localization is so hard.
you can't say exactly how far a beacon should transmit its signals, but on most beacons (I don't know about Radius networks) you can change the txPower / transmit power. This varies from beacon to beacon (and also depends on the environment around the beacon), so you'll have to do your own experiments to find the sweet spot.