Passive vs. Active Bluetooth LE Scanning

T_X · July 4, 2016, 7:51pm

Hi!

Are there any implications on battery life for Estimote stickers regarding these two scanning modes? For instance, might active scans prevent the stickers to go into some sleep or something similar?

Could a continuous “hcitool lescan” reduce the battery life of an estimote sticker? I think noble / node-bleacon uses some active scans, too. And I’m wondering wether that could create the very short life time of stickers we are experiencing here.

PS: Here are two places where noble sets some (scanning) intervals:

github.com

noble/noble/blob/master/lib/hci-socket/hci.js

var debug = require('debug')('hci');

var events = require('events');
var util = require('util');

var BluetoothHciSocket = require('bluetooth-hci-socket');

var HCI_COMMAND_PKT = 0x01;
var HCI_ACLDATA_PKT = 0x02;
var HCI_EVENT_PKT = 0x04;

var ACL_START_NO_FLUSH = 0x00;
var ACL_CONT  = 0x01;
var ACL_START = 0x02;

var EVT_DISCONN_COMPLETE = 0x05;
var EVT_ENCRYPT_CHANGE = 0x08;
var EVT_CMD_COMPLETE = 0x0e;
var EVT_CMD_STATUS = 0x0f;
var EVT_LE_META_EVENT = 0x3e;

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github.com

noble/noble/blob/master/lib/hci-socket/hci.js

var debug = require('debug')('hci');

var events = require('events');
var util = require('util');

var BluetoothHciSocket = require('bluetooth-hci-socket');

var HCI_COMMAND_PKT = 0x01;
var HCI_ACLDATA_PKT = 0x02;
var HCI_EVENT_PKT = 0x04;

var ACL_START_NO_FLUSH = 0x00;
var ACL_CONT  = 0x01;
var ACL_START = 0x02;

var EVT_DISCONN_COMPLETE = 0x05;
var EVT_ENCRYPT_CHANGE = 0x08;
var EVT_CMD_COMPLETE = 0x0e;
var EVT_CMD_STATUS = 0x0f;
var EVT_LE_META_EVENT = 0x3e;

This file has been truncated. show original

Does anyone know whether this is similar or different to what the official Android/IOS SDK does?

heypiotr · July 5, 2016, 8:52am

Stickers broadcast non-connectable packets majority of their time, so passive/active scanning doesn’t make a big difference. iOS/Android are mostly doing active scanning as well. (I only found iOS doing passive scanning when monitoring for an iBeacon packet and the app is not running.)

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Passive vs. Active Bluetooth LE Scanning

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