Bluetooth LE#
Bluetooth Low Energy (BLE, also Bluetooth Smart) is the protocol used to bridge ANT+ sensor data from the Watchlink to the Apple Watch Ultra 1, and to keep the Watch connected to the iPhone 16 Pro Max.
In the Network#
| Link | Role |
|---|---|
| Watchlink → Apple Watch Ultra 1 | Relays Garmin Edge aggregated ride data to the Watch |
| Apple Watch Ultra 1 ↔ iPhone 16 Pro Max | Watch sync, notifications, Siri handoff, cellular sharing |
Key Specifications#
| Attribute | Spec |
|---|---|
| Frequency band | 2.4 GHz ISM (2402–2480 MHz) |
| Channels | 40 channels × 2 MHz |
| Data rate | 1 Mbps (LE 1M PHY); 2 Mbps (LE 2M PHY, optional) |
| Typical range | 10 m (Class 2 devices) |
| Topology | Connection-based (point-to-point) |
| Max simultaneous connections | Device-dependent; Apple Watch supports several |
| Power consumption | Low — designed for coin-cell operation |
How It Is Used Here#
Watchlink → Apple Watch#
The Watchlink receives the Garmin Edge MTB’s ANT+ broadcast (which aggregates power, cadence, speed, gear, and radar data), then re-transmits that data to the Apple Watch Ultra 1 over BLE using standard GATT fitness service profiles. The Watch receives it as if it were a native BLE sensor.
This is the only path by which live ride data from ANT+ sensors reaches the Watch — the Watch has no ANT+ radio.
Apple Watch ↔ iPhone#
The Watch maintains a persistent BLE connection to the iPhone 16 Pro Max during the ride for:
- Notification forwarding
- Siri requests
- Cellular data sharing (Watch uses iPhone’s cellular when on the same connection)
- Activity syncing post-ride
BLE vs ANT+ for This Role#
| Aspect | ANT+ | Bluetooth LE |
|---|---|---|
| Topology | Broadcast (1:many) | Connection-based (1:few) |
| Sensor interoperability | Standardised profiles across brands | GATT profiles, less universal for cycling |
| Apple Watch support | None (no ANT+ radio) | Native |
| Why used here | Sensor → head unit | Head unit bridge → consumer wearable |
BLE is used at the wrist end of the data chain precisely because the Apple Watch supports it natively. ANT+ handles the sensor end because it is the universal language of cycling hardware.