Advertising Interval

Advertising Interval

The advertising-interval/" class="glossary-term-link" data-term="advertising interval" data-definition="Time between BLE advertising events." data-category="GAP & Advertising">advertising interval defines the time between consecutive advertising events on a BLE peripheral. It directly controls the trade-off between device discoverability, connection speed, and power consumption, making it one of the most important parameters for battery-powered BLE products.

Value Range

The advertising interval is specified in units of 0.625 ms, with an allowed range from 20 ms (32 units) to 10,485 ms (16,768 units -- approximately 10.24 seconds). The Bluetooth specification adds a pseudo-random delay of 0--10 ms (advDelay) to each interval to reduce the probability of repeated collisions between multiple devices advertising simultaneously on the same channel.

Power Consumption Impact

During each advertising event, the BLE radio transmits on channels 37, 38, and 39 in succession, drawing 5--15 mA for approximately 1--3 ms per event. At an advertising interval of 100 ms, this yields roughly 10 advertising events per second and an average current of 50--150 uA. At 1000 ms, only 1 event per second occurs, reducing average current to 5--15 uA.

For beacon applications running on a CR2032 coin cell (225 mAh), a 1-second advertising interval provides approximately 6--18 months of battery life, while a 100 ms interval reduces this to weeks. Adjusting the advertising interval is often the single most impactful optimization for beacon battery life.

Discoverability and Connection Latency

Shorter advertising intervals improve discoverability. A central device scanning with a scan window of 30 ms will detect a 100 ms advertiser within 1--3 scan cycles but may take 2--5 seconds to detect a 2000 ms advertiser. Connection latency follows a similar pattern -- the central can only send a connection request after receiving an advertising packet, so longer intervals mean slower pairing.

For user-facing products like smart locks or medical devices, Apple and Google recommend advertising intervals of 20--152.5 ms for fast discovery. For background beacons and asset trackers, 1000--10,000 ms intervals are common.

Dynamic Advertising Interval

Many BLE stacks support dynamic advertising intervals. A device might use a fast interval (30 ms) for the first 30 seconds after power-on or button press to enable quick pairing, then automatically switch to a slow interval (1000 ms) to conserve battery. This fast-then-slow pattern is widely adopted in Bluetooth SIG design guidelines and platform-specific best practices.