Skip to main content

BLE scan

This section focuses on the BLE scan geolocation technology.

Configuration​

Standard scan parameters and filtering​

The BLE scan configuration is done via the configuration group 4.

The ble_scan_duration, ble_scan_window and ble_scan_interval define the configuration of the scan.

The parameter ble_scan_type configures the type of beacon we expect.

The ble_scan_min_rssi configures the minimum received power level of a beacon for processing. Beacons received below this threshold will be ignored.

This service offers an enhanced filtering scheme based on two filters. Each filter contains an offset (ble_scan_filterX_offset) locating the first byte of the advertisement data part. The beginning of the advertisement part is related to the type of expected beacons:

  • Eddystone UUID beacons: the offset 0 locates the first byte of the name-space.
  • Eddystone URL beacons: The offset 0 locates the URL schema prefix.
  • Eddystone TLM beacons: The offset 0 locates the first byte of the battery voltage.
  • iBeacons: The offset 0 locates the first byte of the company UUID.
  • altBeacons: The offset 0 locates the first byte of the beacon D.
  • custom: The offset 0 locates the beginning of the advertisement frame.

The filter mask (ble_scan_filterX_mask) with its offset (ble_scan_filterX_offset) and the filter value (ble_scan_filterX_value) define the application of the filter: For each byte of the advertisement data, the process performs a logical AND between the data and the mask from the offset until the actual length of the mask and the result is finally compared to the filter value. If there is no match, then the advertisement is ignored.

Note that the length of the filter is given by the size of the filter (10) minus the number of null bytes starting from the end. Examples:

  • A filter mask equals to {FF,FF,FF,FF,00,00,00,00,00,00} has an actual size of 4.
  • A filter mask equals to {FF,FF,FF,FF,00,FF,00,00,00,00} has an actual size of 6.
  • A filter mask equals to {00,00,00,00,00,FF,00,00,00,00} has an actual size of 6.

The filter match is done on the actual size of the filter. So, If the data part length is less than the actual filter size, the process filters out the beacon.

When configuring the two filters, the beacon will be valid only if the two filters match.

Notes

  • The filtering is not applicable if the parameter ble_scan_type is all-beacon or exposure.
  • If the ble_scan_type is set to custom, it is advised to setup filters unless you expect to receive all type of beacons.

Reporting​

The BLE scan reporting is the result of the scan operation. The configuration defines what should be reported via the Network (LoRaWAN or LTE).

The following parameters configure the reporting:

  • ble_scan_nb_beacons: Configure the number of beacons that should be reported.
  • ble_scan_report_id_ofs: Configure the type of information the report should contain:
    • MAC address: Beacon MAC address.
    • Short beacon ID: Identifier on 2 bytes extracted from the advertisement data.
    • Long beacon ID: Identifier on 16 bytes extracted from the advertisement data.
  • ble_scan_report_id_ofs: Locate the first byte that should be extracted from the advertisement data to form the short or long beacon ID.

Notes

  • The ble_scan_report_id_ofs parameter is applicable only if the ble_scan_report_id_ofs is either short or long beacon ID.
  • As for the filtering, the beginning of the advertisement part is related to the type of expected beacons. Refer to the filtering section to locate properly the first byte to form the beacon ID.
  • The short beacon ID cannot be used is the ble_scan_type is all-beacon or exposure.
Last updated on