Bluetooth Low Energy Advertising

Bluetooth Low Energy (BLE) conserves power by remaining in sleep mode most of the time. It wakes up only to make advertisements and short connections, so advertisements affect both power consumption and data transfer bandwidth.

Bluetooth 5 advertising extension

Android 8.0 supports Bluetooth 5, which provides broadcasting improvements and flexible data advertisement for BLE. Bluetooth 5 supports BLE Physical Layers (PHYs) that retain the reduced power consumption of Bluetooth 4.2 and let users choose increased bandwidth or range. More information can be found in the Bluetooth 5 Core Specifications.

Implementation

New Bluetooth 5 features are automatically available for devices running Android 8.0 with compatible Bluetooth controllers. Use these BluetoothAdapter methods to check if a device supports Bluetooth 5 features:

  • isLe2MPhySupported()
  • isLeCodedPhySupported()
  • isLeExtendedAdvertisingSupported()
  • isLePeriodicAdvertisingSupported()

To disable the advertising features, work with the Bluetooth chip vendor to disable chip-set support.

The Bluetooth PHYs are exclusive of one another, and the behavior of each PHY is predefined by the Bluetooth SIG. By default, Android 8.0 uses Bluetooth LE 1M PHY, from Bluetooth 4.2. The android.bluetooth.le package exposes the Bluetooth 5 advertising features through these APIs:

  • AdvertisingSet
  • AdvertisingSetCallback
  • AdvertisingSetParameters
  • PeriodicAdvertisingParameters

Create an AdvertisingSet to modify Bluetooth advertisement settings by using the startAdvertisingSet() method in android.bluetooth.le.BluetoothLeAdvertiser. Even if support for Bluetooth 5 or its advertising features is disabled, the API features can also apply to LE 1M PHY.

Examples

This example app uses Bluetooth LE 1M PHY for advertising:

  // Start legacy advertising. Works for devices with 5.x controllers,
  and devices that support multi-advertising.

  void example1() {
   BluetoothLeAdvertiser advertiser =
      BluetoothAdapter.getDefaultAdapter().getBluetoothLeAdvertiser();

   AdvertisingSetParameters parameters = (new AdvertisingSetParameters.Builder())
           .setLegacyMode(true) // True by default, but set here as a reminder.
           .setConnectable(true)
           .setInterval(AdvertisingSetParameters.INTERVAL_HIGH)
           .setTxPowerLevel(AdvertisingSetParameters.TX_POWER_MEDIUM)
           .build();

   AdvertiseData data = (new AdvertiseData.Builder()).setIncludeDeviceName(true).build();

   AdvertisingSetCallback callback = new AdvertisingSetCallback() {
       @Override
       public void onAdvertisingSetStarted(AdvertisingSet advertisingSet, int txPower, int status) {
           Log.i(LOG_TAG, "onAdvertisingSetStarted(): txPower:" + txPower + " , status: "
             + status);
           currentAdvertisingSet = advertisingSet;
       }

       @Override
       public void onAdvertisingDataSet(AdvertisingSet advertisingSet, int status) {
           Log.i(LOG_TAG, "onAdvertisingDataSet() :status:" + status);
       }

       @Override
       public void onScanResponseDataSet(AdvertisingSet advertisingSet, int status) {
           Log.i(LOG_TAG, "onScanResponseDataSet(): status:" + status);
       }

       @Override
       public void onAdvertisingSetStopped(AdvertisingSet advertisingSet) {
           Log.i(LOG_TAG, "onAdvertisingSetStopped():");
       }
   };

   advertiser.startAdvertisingSet(parameters, data, null, null, null, callback);

   // After onAdvertisingSetStarted callback is called, you can modify the
   // advertising data and scan response data:
   currentAdvertisingSet.setAdvertisingData(new AdvertiseData.Builder().
     setIncludeDeviceName(true).setIncludeTxPowerLevel(true).build());
   // Wait for onAdvertisingDataSet callback...
   currentAdvertisingSet.setScanResponseData(new
     AdvertiseData.Builder().addServiceUuid(new ParcelUuid(UUID.randomUUID())).build());
   // Wait for onScanResponseDataSet callback...

   // When done with the advertising:
   advertiser.stopAdvertisingSet(callback);
}

This example app uses the BLE 2M PHY for advertising. The app first checks that the device supports the features being used. If the advertising features are supported, then the app configures BLE 2M PHY as the primary PHY. While 2M PHY is active, advertisement does not support Bluetooth 4.x controllers, so setLegacyMode is set to false. This example modifies parameters while advertising and also pauses the advertisement.

void example2() {
   BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
   BluetoothLeAdvertiser advertiser =
     BluetoothAdapter.getDefaultAdapter().getBluetoothLeAdvertiser();

   // Check if all features are supported
   if (!adapter.isLe2MPhySupported()) {
       Log.e(LOG_TAG, "2M PHY not supported!");
       return;
   }
   if (!adapter.isLeExtendedAdvertisingSupported()) {
       Log.e(LOG_TAG, "LE Extended Advertising not supported!");
       return;
   }

   int maxDataLength = adapter.getLeMaximumAdvertisingDataLength();

   AdvertisingSetParameters.Builder parameters = (new AdvertisingSetParameters.Builder())
           .setLegacyMode(false)
           .setInterval(AdvertisingSetParameters.INTERVAL_HIGH)
           .setTxPowerLevel(AdvertisingSetParameters.TX_POWER_MEDIUM)
           .setPrimaryPhy(BluetoothDevice.PHY_LE_2M)
           .setSecondaryPhy(BluetoothDevice.PHY_LE_2M);

   AdvertiseData data = (new AdvertiseData.Builder()).addServiceData(new
     ParcelUuid(UUID.randomUUID()),
           "You should be able to fit large amounts of data up to maxDataLength. This goes
           up to 1650 bytes. For legacy advertising this would not
           work".getBytes()).build();

   AdvertisingSetCallback callback = new AdvertisingSetCallback() {
       @Override
       public void onAdvertisingSetStarted(AdvertisingSet advertisingSet, int txPower, int status) {
           Log.i(LOG_TAG, "onAdvertisingSetStarted(): txPower:" + txPower + " , status: "
            + status);
           currentAdvertisingSet = advertisingSet;
       }

       @Override
       public void onAdvertisingSetStopped(AdvertisingSet advertisingSet) {
           Log.i(LOG_TAG, "onAdvertisingSetStopped():");
       }
   };

   advertiser.startAdvertisingSet(parameters.build(), data, null, null, null, callback);

   // After the set starts, you can modify the data and parameters of currentAdvertisingSet.
   currentAdvertisingSet.setAdvertisingData((new
     AdvertiseData.Builder()).addServiceData(new ParcelUuid(UUID.randomUUID()),
           "Without disabling the advertiser first, you can set the data, if new data is
            less than 251 bytes long.".getBytes()).build());

   // Wait for onAdvertisingDataSet callback...

   // Can also stop and restart the advertising
   currentAdvertisingSet.enableAdvertising(false, 0, 0);
   // Wait for onAdvertisingEnabled callback...
   currentAdvertisingSet.enableAdvertising(true, 0, 0);
   // Wait for onAdvertisingEnabled callback...

   // Or modify the parameters - i.e. lower the tx power
   currentAdvertisingSet.enableAdvertising(false, 0, 0);
   // Wait for onAdvertisingEnabled callback...
   currentAdvertisingSet.setAdvertisingParameters(parameters.setTxPowerLevel
     (AdvertisingSetParameters.TX_POWER_LOW).build());
   // Wait for onAdvertisingParametersUpdated callback...
   currentAdvertisingSet.enableAdvertising(true, 0, 0);
   // Wait for onAdvertisingEnabled callback...

   // When done with the advertising:
   advertiser.stopAdvertisingSet(callback);
}

Verification

Run applicable Bluetooth product tests to verify device compatibility with Bluetooth 5.

AOSP contains the Android Comms Test Suite (ACTS), which includes tests for Bluetooth 5. The ACTS tests for Bluetooth 5 can be found in tools/test/connectivity/acts/tests/google/ble/bt5.