I'm developing an application that will use iBeacons for indoor navigation, and I found that the rate the function locationManager:rangingBeaconsDidFailForRegion:withError: is being called is not high enough, so I'm going to add the RSSI data from CoreBluetooth's centralManager:didDiscoverPeripheral:advertisementData:RSSI:.
And I found a curious fact: when I listen to the iBeacon with CoreLocation and log the peripheral id:
- (void)centralManager:(CBCentralManager *)central
didDiscoverPeripheral:(CBPeripheral *)peripheral
advertisementData:(NSDictionary *)advertisementData
RSSI:(NSNumber *)RSSI
{
NSLog(@"%@, RSSI: %@", peripheral, RSSI);
each beacon is reported with different UUID on different devices:
A25804BD-D77A-5004-4C2C-301D996C7367 - my iPhone 5
843F4237-6059-9A5E-AA34-0BD92304BE1F - colleague's iPhone 5
77685805-C253-52BD-B787-8B95308834FB - other colleague's iPad mini
The idea was to bind UUID of each beacon to its location, so this behavior is quite functionality-breaking.
Why the UUID of physically the same beacon (not powered off/on) is different on different devices? Is it an expected behavior? If it is, how could I opt out of it?
You cannot read the identifiers of standard iBeacons using CoreBluetooth. As Chris Stratton said in his comment, the UUID that CoreBluetooth gives you is a device UUID, which is randomly generated on a per-session basis by iOS. It has nothing to do with the iBeacon ProximityUUID.
More details on why you can't read iBeacon identifiers with CoreBluetooth are here: http://developer.radiusnetworks.com/2013/10/21/corebluetooth-doesnt-let-you-see-ibeacons.html
It is true that you only get on RSSI measurement per locationManager:didRangeBeacons:inRegion: callback. This is a real obstacle to doing a custom distance estimate. Behind the scenes, iOS can gather 10x as many measurements for iBeacons transmitting at 10Hz. You are correct that you can get more measurements using CoreBluetooth, but the problem is that there is no reliable way of lining up which bluetooth devices you see with CoreBluetooth correspond to the iBeacons you can see with CoreLocation.