CODEWITHSUNDEEP
androidiosbluetooth-lowenergyibeaconrssi
Golnaz Nikmehr
Golnaz Nikmehr

Reputation: 21

Difference in ble scan rate in Android vs iOS

My issue is that iOS and various android phones receive number of BLE advertise packet from specific ibeacon, for example In 5 minutes from a specific beacon iOS receives about 904 advertise packets and android phones receive about between 230 to 480 depending on the phone.

Does anyone know if there is a setting that can set scanning rate of the BLE module? If not what else might cause this issue?

I use "CBCentralManager" to utilize BLE module in iOS and "blutoothLeScanner" in Android.

//Creating an instance of CBCentralManager
private let bluetoothManager = CBCentralManager(delegate: nil, queue: nil)

//Start Scanning
bluetoothManager.scanForPeripherals(withServices: nil, options: [CBCentralManagerScanOptionAllowDuplicatesKey:NSNumber(value: true)])

Upvotes: 2

Views: 1852

Answers (3)

maze
maze

Reputation: 884

I know the same behaviour from some phones.

Note that your peripheral probably does advertising on 3 BLE channels. (?) It might be possible that your Android device only listens on one channel.

Moreover and on some cases even worse, it is possible that your phones listens on one channel at a time and another channel some time later, thus, also does channel hopping for scanning. It is possible that you get aliasing effects and see the advertising only a few times. This is why the Apple Accessory Guide recommends certain advertising intervals of the peripheral. (chap. 23.5)

Upvotes: 0

davidgyoung
davidgyoung

Reputation: 64941

There is a large amount of variation between Android device models (often called fragmentation) and this applies to the Bluetooth LE behavior as much as anything. Differences between Android phones is a more likely explanation for the discrepancies you see than the scan rate, which defaults to a 100% duty cycle (LOW LATENCY) on all Android devices I have seen, and is similar to iOS.

Given the same conditions, some Android devices scan a similar number of BLE advertisements in iPhones (e.g. Pixel and later Nexus 5+ devices.) But not all Android devices provide as good of results.

You don't say specifically which Android models that you tested which saw fewer advertisement detections, but there are a number of things that might cause this:

  1. Some older Android devices like the Nexus 4, Nexus 7 and Moto G (1st generation) would only detect on advertisement per scan per unique bluetooth device. Restarting the scan was needed to detect a second packet from that device. You might try restarting your BLE scan every second or so to see if this helps.

  2. Some Android devices like the Huawei P9 have very poorly performing BLE antennas, so they are rarely able to detect BLE devices at more than 10 meters, whereas iPhones typically detect at 40-50 meters or more. You can see if this is the cause of your issue by looking at the signal level (RSSI value) for packets received. Are the RSSI values consistently weaker (more negative) on the Android device vs. iOS? If so, then this explains the discrepancy.

Upvotes: 0

Emil
Emil

Reputation: 18452

The scan parameters are hardcoded in both OSs, but on Android you can choose between the following three modes:

  1. https://developer.android.com/reference/android/bluetooth/le/ScanSettings.html#SCAN_MODE_BALANCED
  2. https://developer.android.com/reference/android/bluetooth/le/ScanSettings.html#SCAN_MODE_LOW_LATENCY
  3. https://developer.android.com/reference/android/bluetooth/le/ScanSettings.html#SCAN_MODE_LOW_POWER

Note that if you scan in the background, SCAN_MODE_LOW_POWER will be used regardless of what you select.

Upvotes: 1

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