I am using the altbeacon library with 2 iBeacons.
I downloaded the sample app for android studio from http://altbeacon.github.io/android-beacon-library/ and added the iBeacon Layout ("m:2-3=0215,i:4-19,i:20-21,i:22-23,p:24-24").
When I start the ranging activity the beacons are detected - but very sporadic.
See:
https://dl.dropboxusercontent.com/u/63333482/Screenshot_20160322-191422.png
I also installed the Locater App - and it seems to be quite the same here.
I'm testing with HTC m8.
Has anyone an idea what could be the problems (Beacons, Mobilephone, etc.?)
Thanks
Remember that beacons send at a rather low frequency. Usually once a second if you haven't configured them. That means you will see loss of "pings". You need to use a timer per beacon or compare timestamp with current time to keep tab on real loss of communication.
What frequency (or rather interval) are they set for?
Do they have different IDs?
How far away are the beacons?
I'm not saying you can rule out phone problems though, as the series of zeros seems odd.
Cheers,
Anders
Related
first of all i would like to say that beacons seems to be something great and usable, i am very enthusiastic still i saw it for the first time.
Now, i would like to try them and to make an Android app, but i'm confused about some things that i didn't found it clearly on internet:
Are beacons available already?
How much does a beacon cost?
Does it need to be charged ?
How much time can a beacon work without charging?
Do i need to setup every device for interaction with it?
Can i implement beacon in Unity App ?
Is there any tutorials about using it?
I know, post is a little big, but i would be very glad if i will found here answers. Have a nice day! ;)
Are beacons available already?
yes, check out the internet.. radius networks, kontakt.io, estimote etc., you could also hit Alibaba, or buy a raspberry pi and a bluetooth dongle
How much does a beacon cost?
cheap. Small beacons could be as little $1 each, but these have drawbacks like non-replaceable batteries and short range, Bluetooth 5 beacon could be more expensive, but these can cover a 1km radius (personally I think that's pointless). Typically expect around $30 for a "good" or top-tier beacon company's primary beacon choice. If you buy bulk you get cheaper, but you might want to experiment with a few different kinds before you do that. Our company bought like 300 at one stage and we might need to replace them with a different manufacturer now
Does it need to be charged ?
some have replaceable batteries, some are only available to be plugged in, some are just disposable - you need to track that yourself
How much time can a beacon work without charging?
it can't - you may be thinking of NFC here - a Bluetooth radio/antenna requires more power than you might think (but probably less than both of us think to be honest), however it needs a dedicated power source both to transmit and receive data
Do i need to setup every device for interaction with it?
no, you make an app that listens for it. Well.. there are actually lot of options, however, not with straightforward detection/processing. Eddystone promotes a notion of "the Physical Web", which is like using URLs sent by Eddystone beacons to show you the right content, or iPhones actually have more built in support for some (mainly) retail use cases. Android is great because you can do so much in the background, and foreground services give you a lot more say about how and when you are stopped. You should also be aware that 4/5/6/7 all have different caveats around scanning/receiving, but most of the differences will/should be absorbed by any SDK you might use
Can i implement beacon in Unity App ?
certainly, just find a use case (AR/VR and a drone with a beacon for a Dragon? :O)
Is there any tutorials about using it?
so many, google about, but I would recommend starting with Radius Network's Android Beacon Library.(This uses Altbeacon, but is VERY easily changed to work with iBeacon and even Eddystone, also it's free and these guys know their stuff). Also, there are many beacon apps you should download as the consistency is not guaranteed across devices, and a few apps have a few different features that you might want for debugging. Try Locate Beacon (by Radius) NRF Toolbox and basically any other BLE app with a decent score - it can be really good to cross reference the hits when funny stuff starts happening.
A lot of people talk about Beacons and managing them as if it's more complex than it is, you have an object that just screams an ID every X milliseconds, you hear that, you do something with it, once, every X seconds, or whatever you want
I would say you should get very familiar with the difference between BLE/ Bluetooth Smart and regular Bluetooth that interacts via a GATT server. With beacons you're essentially just listening to a peripheral device that advertises in a set format. As the developer, it is up to you to take this and make it meaningful for your user
I am testing out a positioning system using iBeacon and Altbeacon. I have found that my triangulation results are actually pretty accurate, but sometimes it takes upwards of 5 seconds to see the proper results.
For example, say I am currently standing at Point A. Altbeacon + my triangulation has me properly placed very close to Point A. However, when I move 5 meters away to Point B, I remain around Point A for around 6 seconds and all of the sudden I snap into place right near Point B. Is this an issue with Altbeacon, or possibly the communication between my iBeacons and my Android tablet?
Note: I am using a Kindle Fire 10, running FireOS 5.1.1 on top of Android. The Bluetooth iBeacon technology is BLE, and broadcasts at around 1Hz.
The issue of time lag that you describe may be caused by averaging intervals on the signal measurement. You do not say what scanning framework you are using, or if you are using raw RSSI or a distance estimate as input to your algorithm. The Android Beacon Library by default uses a 20 second averaging interval (configurable) for its distance estimates. Other framework's use similar averaging.
Reducing the averaging interval will lessen the lag, but increase the noise as an input to your algorithm.
EDIT: To reduce the distance estimate sampling interval to 3 seconds from the default 20 seconds, call:
RunningAverageRssiFilter.setSampleExpirationMilliseconds(3000l);
I have tried previously what you were trying to do. There was a lot of issues making it impossible to get correct triangulation results.
Theoretically it should work, but
Practically you will have a lot of challenges, like the fact the Bluetooth Beacon uses the 2.4GHz frequency, almost all Bluetooth Beacon has non-directional antenna, which means that you might risk not measuring the signal source but the reflection of the signal surrounded by the beacon.
The other fact is the noise from other sources or Bluetooth Beacon in your environment.
Depending on the Android phone model, the receiver antenna of Bluetooth is not necessarily mount same place in the phone, that means how you hold the phone will change the RSSI reading
Holding the phone in hand or near human body might also give different readings or no reading at all, since the human body contains water that is a signal reducer/killer for Bluetooth signal.
So even thus you improve your latency time of Bluetooth Beacon by software, you will still have these challenge make it almost impossible to get the right results.
I have seen a new directional Bluetooth Beacon I have not testing it yet, but it sounds like it solving some the mentioned issues.
It is correct what #davidgyoung wrote, but that won’t change the fact of real world scenario.
Btw, I have worked with Altbeacon a very nice and respected tool, and I used both RSSI and distance estimate with different type of Bluetooth Beacon and different phones and it did not help much, it is not Altbeacon the problem.
And regarding the university project I mentioned in my comments, we ended up using Bluetooth Beacon in different way to help us finding directions to target for visually impaired people, and we have developed scientific paper on it.
Finally for inspiration of what you are doing and what I mentioned in my answer, see this video it shows triangulation experiment, the provider of this video is btw also a user at Stackoverflow.
Note: my answer here is focusing on the context of triangulation and the challenges here make it as not a sweet solution.
I noticed that the signal strength of Bluetooth Low Energy received on Androids is varying in cycles.
The graph below represents the RSSI values of one BLE beacon over two minutes. The receiving Android and the beacon were both static with a distance of 1 meter. I made sure that there is as low interference as possible. The Android was a Nexus 5, but I had the same phenomenon with other Android devices, all running on API 21. I could not test it on iOS yet.
RSSI Graph
You can see that there are 3 major levels for the RSSI repeating every 15 seconds, like low -> middle -> high -> low -> middle -> high etc.
My guess is that the reason lies on the android side, not sure whether it is because of hardware or software reasons.
Why is the RSSI cyclic over time? Can someone explain?
After reading a lot into the topic now, I might have come to an answer.
Bluetooth Low Energy beacons use three different channels for advertising, which is their adaption of frequency hopping to avoid interference with other 2.4GHz signals. This happens much slower than for normal Bluetooth (1600/s) - according to my measurements around every 5 seconds.
More here:
http://www.argenox.com/bluetooth-low-energy-ble-v4-0-development/library/a-ble-advertising-primer/
The received signal strength depends obviously on the frequency, so if the frequency changes to another channel, the RSSI is different. How to deal with that is now a different question.
UPDATE:
After following up on this issue, I have to update my remarks:
It is very likely that the three levels with each one around 5s are not directly due to the beacons slow frequency hopping, but to the android devices scanning seperately on the channels and switching to the next after such a time interval.
A way to overcome this behavior is starting and stopping the scan process in a loop, so that a scan lasts clearly less than 5s. When starting the scan, the device seems to begin scanning always on the same channel and the scan is restarted before it can switch to a different channel. With the restarts, the pattern is not detectable anymore - to the disadvantage that the channel is "fixed" and may suffer interference on this frequency.
Thanks to Airsource Ltd for bringing me back to this question.
As per Android AOSP - Definition of scan interval and scan window in android source code the scan interval in any scanning mode is 5000ms.
I would assume that your graph was generated via an application that used continuous scanning - i.e. scan window of 5000ms, which is basically continuous.
The scanner will rotate between channels 37,38,39 after every scan interval, which accounts for the differences you observe. Channels 37,38,39 are not contiguous in the BLE spectrum - 37 is at 2402Mz whereas 39 is at 2480Mz. The difference in wave length means that the multi path (interference from reflections) fade will be different for each channel http://www.cl.cam.ac.uk/~rmf25/papers/BLE.pdf - you say that the devices were static, so provided that nothing else was moving, the interference will also be static.
On iOS, the scan interval (foreground) is reportedly 40ms which means that you should not experience this precise effect.
I'm fairly new to iBeacon but I have spent the day trying to get informations and a working Android application with iBeacon.
I have stumbled upon Android iBeacon Library samples and gave it a try. I used the latest aar file (0.7.3) and basically copy/paste their examples in a new project.
I have created a beacon using an iPad with AirLocate (compiled from Apple's code from the Dev Center) and launch the code.
My problem is the range fluctuating all the time with no logic.
For example, the phone (in this case a Nexus 5, original rom, no modification) placed half a meter away from the iPad gives me the following measures :
0.01m
0.03m
0.07m
0.48m
0.01m
0.02m
etc.
When I use another iPad with AirLocate on it, it gives a more stable and realistic measure. Excluding the beacon as the source of the problem.
I have made the test with a Nexus 7 2013 (Original rom, not modified) and I got the same issue. I have read the wifi can cause problem so I disabled it but it is still the same.
I also have the same issue with Radius Networks application on the Play Store: iBeacon Locate
I was wondering if the anyone else have the problem with this library ?
Is there something I can do to help fix this problem ?
Do you know another library I can use which won't cause that kind of problem ?
Any help is appreciate. Thank you in advance.
A big part of the variation you see is Android is caused by a limitation in the way Android allows access signal strength measurements from Bluetooth LE. Unfortunately, there isn't much that can be done about this without changes to Android.
In both iOS CoreLocation and the Android iBeacon Library, the distance estimate is only an estimate, and fluctuations with noise on signal strength measurements cause the estimates to bounce around.
The algorithm in the Android iBeacon Library is not the same as in iOS CoreLocation, because the iOS CoreLocation implementation is closed source. The intention is that they behave in a similar way. The Android iBeacon Library is based on a 10 second running average of 80th percentile measurements (e.g. the top and bottom 10th percentile measurements are thrown away for the average.) You can see the details of the calculation here:
protected static double calculateAccuracy(int txPower, double rssi) {
if (rssi == 0) {
return -1.0; // if we cannot determine accuracy, return -1.
}
double ratio = rssi*1.0/txPower;
if (ratio < 1.0) {
return Math.pow(ratio,10);
}
else {
double accuracy = (0.89976)*Math.pow(ratio,7.7095) + 0.111;
return accuracy;
}
}
On Android, the Bluetooth LE Scan API only allows a single signal strength measurement per scan. On iOS, it is possible to get a different measurement for each advertisement broadcasted. By default, the Android iBeacon Library does one bluetooth scan every 1.1 seconds when it is in the foreground, therefore allowing one measurement every 1.1 seconds. So if you have an iBeacon that is transmitting 30 times per second (as iOS devices acting as iBeacons do), iOS will be able to get 300 samples in a 10 second period, and Android only 9. This explains why the estimate has higher noise on Android. And again, there is very little that can be done about it without operating system changes.
Depending on your use case, you may be able to reduce the noise in the distance estimate on Android by implementing a custom calculation that includes more samples over a longer period of time. This would only be appropriate if your use case does not need rapid updates in the estimate. If you are interested in this, you might open a feature request in the open source library.
I want to calculate distance Bluetooth Paired device from android mobile. I am new in Android Bluetooth Concept can any one suggest me it's possible or not possible in android sdk.if it's possible post any code or tutorial link!
The Bluetooth signal strength distance relation depends on the devices (built-in Bluetooth device, antenna, actual orientation of device), current way the persons hold their devices, objects in-between... You could measure this for a pair of devices for a given situation and use these information.
A larger and more general solution would incorporate an external Bluetooth network. Bluetooth triangulation is the basic concept, that will help. The link will give an insight on certainties that are achievable with such a setup. Take is as an upper limit, a device to device approach will be worse.
The EE Stack Exchange site has a more complete answer which includes a mention of Apple using 802.11v for determining if Apple Watch is close to a MacBook.
Bluetooth uses radio, and radio travels at the speed of light. A 1cm round trip will take less than 100ps. Timing something that short will be tricky, probably you'll want a 10GHz clock, though there are other options. But even then, Bluetooth isn't designed to instantly echo the radio message. If you receive, process and re-transmit the message, then the processing delay will be much longer than the time of flight, and will vary randomly by at least the period of the clock used with the Bluetooth chip.
You can't. Maybe, you can get approximate value from signal indicator but it's too much subject because of envirounment - is there something between connected devices, some reflection surfaces, etc.
There is a way you can research, is coding a response time. just calculate the bluethooth response time in nano secs, physically measure the distance between the devices and make a tree rule... is the same concept of GPS. This is a Laboratory work. I have a project that i have to develop it, in schedule i will taking it in a month.
OFC, its possible. It just requires ultra precise app, build to calculate "pings" between the two objects - kinda like ekko-location or laser distance measurement - its about how much time a specific signal travels back and forth.