I'm developing an Android app that continuously scans for BLE advertisements in the background.

I use a foreground service to perform BLE scanning, and I restart the scanner every 3 minutes.

The sensor periodically broadcasts BLE advertisements, and I want the app to receive these advertisements reliably without missing them.

When the app is in the foreground, the scan duty cycle is effectively 100%. However, as soon as the app goes into the background or the screen is turned off, it drops to around 5%.

I confirmed this behavior by analyzing the HCI snoop log, and captured the actual LE_Set_Extended_Scan_Parameters values:

• Foreground: interval = 100 ms, window = 100 ms (duty ≈ 100%)

• Background / Screen off: interval = 10240 ms, window ≈ 511.9 ms (duty ≈ 5%)

This behavior was observed on a Pixel 10a running Android 17.

Relevant implementation details:

• Scanning is performed via BluetoothLeScanner from a foreground service (FOREGROUND_SERVICE_TYPE_CONNECTED_DEVICE).

• ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY).

• ScanFilter.Builder().setManufacturerData(MANUFACTURER_ID, byteArrayOf(), byteArrayOf())

  • Filtering by Manufacturer ID only, no byte pattern/mask.

• BluetoothAdapter.isOffloadedFilteringSupported() is true on this device (filtering_support: 1, extended_scan_support: 1 per dumpsys bluetooth_manager).

Is there any way to prevent the BLE scan duty cycle from degrading when the app is in the background or the screen is turned off?

In particular, I'm looking for a way to maintain a high scan duty cycle and reliably receive the sensor's periodic BLE advertisements while the app is running in the background or the screen is off.