I did not get a convincing answer to why startUpdatingLocation should be used to range beacons. Is is required to monitor/range beacons in background or to get notifications when user is already in region and starts monitoring beacons? Came across posts which say this can actually increase the battery consumption. Would like to not call this method it it is not necessary.
It is not necessary. I have built dozens of beacon apps and they all range and monitor beacons just fine without this enabled.
You only need to call that method if you also need GPS (or other geo sensor) location updates.
Try it and see!
Related
My goal is to find all iBeacons nearby an I plan to send local notification when new ibeacon is found. I am assuming all of them will have the same proximity UUID. And I will use combo of major and minor ids to identify them (each user will have unique combination of major & minor id).
I am assuming I need to monitor for this specific UUID and that locationManager(_ manager: CLLocationManager, didEnterRegion region: CLRegion) will be triggered only for the first UUID right? So when it happens I need to startRanging to find every beacon nearby except the one Ive found. What will be achieved by callback from locationManager(_ manager: CLLocationManager, didRangeBeacons beacons: [CLBeacon], in region: CLBeaconRegion). But the question is what will happen if new beacons will appear nearby? I need to fire startRangin also on didExitRegion? I am only afraid that if the one already found beacon will stay in range for like 1 hour, I won't be able to detect any other beacons which will appear in this region/range.
Any advice for most efficent search?
Using a backgrounded iOS app to track multiple BLE beacons with the same UUID and differing major and minor values is challenging. (Ranging normally times out after 10 seconds in the background.) Two basic approaches:
Solution #1: Constant Ranging While in Region
For this approach, you need to set up your app to unlock unlimited ranging in the background while you are inside the beacon region. This is a bit tricky, and will use significant battery if you are around beacons for long periods of time. But is legal to do for App Store distribution provided that your app makes it clear that it uses location in the background for an approved purpose.
I documented this in a blog post here: http://www.davidgyoungtech.com/2023/02/10/forever-ranging
The basic steps are:
Setup:
Put the following declaration in your Info.plist
<key>UIBackgroundModes</key>
<array>
<string>location</string>
</array>
Obtain NSLocationAlways permission from the user.
Start monitoring for a CLBeaconRegion with the ProximityUUID and a nil major and nil minor.
Start ranging for the same region. There is no real reason to turn ranging off as logic below will handle throttling whether the OS allows it to do work in the background.
In your didRange callback, add logic to process all the detected beacons.
On Region Entry:
Start location updates at the lowest power setting (basically just using cell radio) with:
locationManager.pausesLocationUpdatesAutomatically = false
locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers
locationManager.distanceFilter = 3000.0
if #available(iOS 9.0, *) {
locationManager.allowsBackgroundLocationUpdates = true
} else {
// not needed on earlier versions
}
// start updating location at beginning just to give us unlimited background running time
self.locationManager.startUpdatingLocation()
Start a background task as described in my blog post here: https://developer.radiusnetworks.com/2014/11/13/extending-background-ranging-on-ios
On Region Exit:
Stop the background task from the previous step
Stop the location updates with self.locationManager.stopUpdatingLocation(
The two changes above will effectively make it so you no longer get ranging updates in the background when no beacons are visible, which will save battery.
Solution #2: Use One Extra Region Per Beacon
This solution is not foolproof, but has the advantage of not requiring a constant background task and background updates. Depending on the placement of your beacons and how users move between them, you will not guarantee detecting each one. But it works for many cases where beacons are not typically placed close together.
Obtain NSLocationAlways permission from the user.
Start monitoring for a CLBeaconRegion with the ProximityUUID and a nil major and nil minor.
Start ranging for the same region. There is no real reason to turn ranging off as logic below will handle throttling whether the OS allows it to do work in the background.
In your didRange callback, add logic to process all the detected beacons.
Each time you detect a new beacon (with a different major and minor) do the following:
Start monitoring a new CLBeaconRegion with the UUID, major and minor of the known beacon. This will allow you to get a didExit callback when it disappears. Because iOS only allows you to monitor 20 regions, you can only do this for 19 additional regions at the same time.
On Region Exit for a CLBeaconRegion for a specific major and minor:
Stop monitoring that region.
The advantage of this approach is that if you have a large number of beacons in overlapping transmitter range, you will get an additional didExit callback as you go out of range of each one. Each time there is a region transition (entry or exit) you get another 10 seconds of background ranging time. This allows you an opportunity to look for new beacons in the area periodically.
This second solution is not perfect. If you encounter beacon A, then it stays in range for 20 seconds before you encounter beacon B, you won't get a ranging callback for beacon B because ranging times out after 10 seconds. In this scenario, you might detect beacon B later on if beacon A goes out of range before beacon B does (the region exit from beacon A gives you more ranging time), but if beacon A does not go out of range before beacon B, then you will never detect beacon B.
Which Solution Should You Use?
Use solution #1 if you must have perfect detections, you app obviously provides a location-specific benefit to the user, and you are OK with the battery drain of constant ranging while beacons are around.
Use solution #2 if you don't need perfect detections, if beacon placement is tolerant of the technique's shortcomings, or if you can't live with the battery drain or constant background ranging for other reasons.
You will initially be monitoring for a CLBeaconRegion that specifies only the beacon uuid you are interested in.
When any beacon advertising this uuid is detected you will get a call to didEnterRegion.
At this point you should call startRangingBeacons(satisfying constraint:) where your CLBeaconIdentityConstraint specifies only the uuid.
You will then get calls to the locationManager(_:didRange:satisfying:) delegate method.
You can examine the minor and major values of the CLBeacon objects passed to the delegate function to determine the beacons that are in range and their range. As beacons satisfying the constraint come into range they will be delivered to the delegate, even if they weren't originally in range when the region was entered.
At some point there will be no beacons with the specified uuid and you will get a call to didExitRegion. At this point you should stop beacon ranging.
I'm working on a use case that needs continuous callbacks while scanning the beacons.
I've thought of 2 approaches but they both have issues.
Monitoring: Monitoring only gives entry and exit callbacks. There's a limitation of listening to only 20 beacons. Also is there a range that i can define to get entry and exit callbacks? Like say if a an advertising beacon comes in range of 2 meters i get an entry callback and if the device moves out of that range i get an exit callback.
Ranging: Ranging gives continuous callbacks along with a set of other parameters like rssi to calculate distance. The big issue when it comes to ranging though is that it consumes insane amount of battery compared to monitoring. What should be an approach for getting continuous callbacks while optimising battery consumption?
I've tried both the approaches and reached to a dead-end. Hence it may seem like a theoretical question yet any insights to solve the use-case in some manner.
It is not possible to set any kind of rssi or distance filter when using iOS CoreLocation beacon monitoring APIs. Ranging is the only alternative when working with iBeacon.
While battery drain of constant BLE scanning is an issue, you an mitigate this by scanning on a lower duty cycle as needed to meet your requirements. For example, you can scan on a 20% duty cycle (and use 20% as much battery as constant ranging) by ranging for 12 seconds every minute. You can adjust this duty cycle as needed to balance your goals between battery savings and responsiveness. I have worked on projects where I change this duty cycle depending on app state, so the app can be more responsive to beacons when it is important and save battery when responsiveness is less important.
In order to be able to do this at all, you must unlock the ability to have iOS let your app run in the background for an unlimited time period as described in my blog post here:
Add the location background mode to Info.plist
Obtain "always" location permission from the user. It is not sufficient to get "when in use" permission.
Start a background task as described here: http://www.davidgyoungtech.com/2014/11/13/extending-background-ranging-on-ios
Request 3km location updates from CoreLocation. This will keep the app running in the background without extra battery drain from GPS, as 3km accuracy only uses the cell radio You don't need to do anything with these results. You just need to request them to keep the app alive.
Once you do the above, you can call locationManager.startRangingBeacons(...) and locationManager.stopRangingBeacons(...) on a timer to implement whatever duty cycle you want.
What should be the correct approach to identify time spend around a beacon[not within a region] in background. I am able to do this when app is in foreground using didRangeBeacons and some business logic.I read on few forums that ranging does work when app has registered for location updates in background, but i am having no success. I have added the location updates key for UIBackgroundModes in plist.
I am using estimote beacons and their sdk.
I see two possible solutions here:
Listen for enter and exit region events, store the timestamps and then use them to calculate the time span on exit. If you define your region so that it encompasses only one beacon, monitoring the region will be equivalent to monitoring the beacon. The only thing to keep in mind is that iOS imposes a limit of 20 regions to be monitored at the same time - so this solution doesn't scale above 20 beacons.
Use ranging in the background. Apart from the UIBackgroundModes, you also need to start regular location services, i.e. startUpdatingLocation.
Beacon ranging delivers events normally while an app is running in the foreground. When your app is in the background, this service delivers events only when the location-updates background mode is enabled for the app and the standard location service is running.
(this is from CLLocationManager class reference, section "Using Location Services in the Background")
Note that ranging in the background will be draining the battery life more than usual, and Apple also requires justification for using the background modes. Unless there's some value for the user of your app coming from the background modes, they might choose to reject it. All in all, use the background ranging wisely! (:
For a specific business case, I would like to trigger proximity-based notification (push or UILocalNotification) by leveraging the iBeacon technology.
This is aimed to work while the app is in background/lockscreen.
I have some specific constraints :
The product has to scale at a certain level so it's not possible to range 20 regions. We will range on one UUID only (maybe 2 or 3 if we develop new set of features, but we will not register a region per physical beacon)
We will use the major and minor to call webservices
Regarding this, I know I will have to use the following approach : first didEnterRegion: with no prior information on the major/minor/distance, and then didRangeBeacon: to perform more advanced actions.
I already use local storage mechanisms to timeout a beacon after he has been used considering the fast beaming rate of beacons.
* The major constraints : we have to region events regarding to the distance of the beacon (exemple, only trigger the notification if CLProximityImmediate)
Now I see a major limitation. As my app will only range in background for a few seconds after it entered in a region, if I had constraints based on the distance/proximity, it is very possible that the app will:
return to background state before the user get close enough from the physical beacon for the event to be triggered
never be triggered again because it has to enter the region to range again, which will probably not happen
Do you have any ideas / work around for such a case ?
You are absolutely correct on the limitations CoreLocation applies in this use case. If you set it up as you describe, the typical behavior will be that the app will detect the beacon in the background at an unknown distance (often the max range of around 50 meters), range in the background for about 5 secs, then the app will be suspended by iOS. That five seconds of ranging time will typically not be enough for the user to get near enough to the beacon to trigger your use case.
Unfortunately, there are no easy workarounds with standard beacons and CoreLocation. CLBeaconRegion objects do not have a distance field like CLCircularRegion does for geofences.
Two more extreme approaches you might try:
Turn off monitoring of your one region as soon as you detect the device is too far away, then re-enable it right as your app suspends itself in the applicationWillResignActive: callback. You might get a new entry event and more background ranging time.
Use nonstandard beacons that periodically stop their transmissions to trigger forced exit/entry events.
I have been working on a prototype iOS app utilizing iBeacons to provide location-relevant information to office employees depending on where in the office they are. The ideal use case is that whenever an employee enters or exits their office, a callback is fired which provides them some information in the form of a notification (it might make a server query to get information first, etc - that sort of thing). We also want to be able to do this when the app is backgrounded or terminated; fortunately, we already know that beacon region boundary crossings trigger the appropriate CoreLocation callbacks even if the app is backgrounded or suspended.
From looking around, I understand that broadly, I have two options for how to approach the beacon region monitoring:
Give each iBeacon its own CLBeaconRegion, and monitor for each of these regions independently.
Monitor for CLBeaconRegions that correspond to multiple iBeacons - for example, each iBeacon has the same UUID and only monitor for a CLBeaconRegion corresponding to that UUID - then try to determine which beacon triggered the boundary crossing using ranging.
Thus far, I had chosen option #1. The advantage of this approach is that I get didEnterRegion: and didExitRegion: calls for each individual beacon and immediately know which beacon I have entered/exited. Also, I only get one enter call and one exit call, which is exactly what I want. Unfortunately, I just realized that this approach also limits me to 20 beacons (since each beacon gets its own region).
I'm not as familiar with the exact implementation details of #2, so correct me if I'm wrong. But it seems that this approach has more drawbacks:
Apple discourages ranging when the app is in the background because the results may not be as accurate.
The ranging calls fire once every second, while I only want to have "enter/exit" callbacks.
If the beacons have region overlap, the ranging calls might continually flip which one is "closest", which would further complicate things.
Basically, I'm wondering if there is a way to utilize option #2, but still have the benefits of option #1 - a quick and easy way to immediately determine which beacon triggered the region change with only one enter or exit callback?
I hope this question is clear enough. It's not all entirely clear in my own head, especially how ranging works.
Option #2 is absolutely more complicated, but you must accept these complications in order to get around the 20 region monitoring limit.
A few points:
In the background, you only have around 5 seconds of ranging time, which does not give you as much time to average RSSI (signal strength) from each beacon to get a good distance estimate. So, yes, the estimates will be less accurate. If you understand this limitation and can live with it for your use case, there is nothing wrong with ranging in the background.
Yes, you will get multiple ranging calls per beacon after region entry, and you won't get any callbacks on region exit. You have to write extra code to take care of this. I have done this by maintaining a NSMutableArray of all the unique beacons (same uuid/major/minor) seen and update it in the ranging callback. You can then access this array in the region exit callback, so you know which beacons disappeared. Of course, it is possible that additional beacons were seen after the 5 seconds of background ranging time expires, but your app will never know about them. With this option, you must accept this limitation.
While it is true that errors on the distance estimate in ranging may incorrectly tell you which beacon is closest, you have an even worse problem when doing monitoring, because you don't get a distance estimate at all. If multiple beacons come into monitoring range around the same time, there is no guarantee that the first entered region callback you get will be for the closest beacon. So if your use case requires taking action based on the closest beacon, then you must do ranging (knowing that there may be error on the distance estimate.)
The drawback of the second approach is detecting the entry of a particular beacon will be purely based on ranging, that will not work if the application is killed. The reason is we will get didEnterRegion only once, because we are monitoring only one region with a particular UID. The next beacon with same UID will not be detected again if the application is terminated or if the background ranging stopped.
I recommend a combination of the mentioned approaches ,
Use same UID for all the beacons.
A beacon is uniquely identified using major/minor value that is collected when ranging.
As mentioned in apple doc, always keep number of monitoring regions below 20 by removing and adding beacons when the user moves from beacon to beacon (better to keep a beacon neighbour relationship graph in the server.)
Start ranging when entering the region ... and identify major/minor and calculate proximity.
Stop ranging when exiting the region.
Find the closest beacon from ranging method (need to skip unknown range beacons).
Monitor only the neighbours of the closest beacon in a given time.
When implementing both options, We should consider one fact, An iBeacon will be detected in 200feet distance. There may be multiple beacons in 200feet range.
If you use the same UUID for every beacon, you can just set the major/minor numbers to differentiate between the different beacons. This way, you are only monitoring for 1 beacon instead of > 20. Then just sort out which one is which from the other identifiers. This is how it works currently with Starbucks and other retailer apps. 1 beacon no matter where you are in the world, and different identifiers to sort things out on the back end.