Meaning
Radio frequency operations in low energy protocols require structured intervals for device discovery. The ble advertising window defines the time a peripheral spends transmitting its presence on the three primary advertising channels. Scanners must time their own reception to overlap with this window to establish a wireless connection.
Timing Period
Frequency of transmission is controlled by the advertising interval setting in the firmware. Within the ble advertising window, the radio sends packets at specific microsecond offsets to avoid persistent collisions with other devices. Shorter windows reduce the time the radio is active but also decrease the chance of being detected by a mobile phone.
Power Balance
Electrical load in a small sensor is dominated by the activity of the wireless transmitter. Every ble advertising window draws a measurable amount of energy from the coin cell battery. Reducing the length of this window or increasing the time between them preserves the life of the power source.
This trade off is the primary concern for designers of wearable technology.
Discovery Chance
Successful pairing requires the scanning device to be listening at the exact moment the peripheral is active. A longer ble advertising window makes it easier for a smartphone to find the device quickly. In crowded environments with many interfering signals, a wider window provides the necessary margin for a reliable link.
Fast discovery is essential for a good user experience when first setting up a smart home accessory.
