Bluetooth Low Energy
Bluetooth · 7 specs
Direct Answer
Bluetooth Low Energy (BLE / Bluetooth Smart) was introduced in Bluetooth Core Specification v4.0 (2010) and enhanced through v4.2 (2014). Operating across 40 channels in the 2.4 GHz band, it replaced continuous connection streams with an event-driven Generic Attribute Profile (GATT) architecture, enabling devices to operate for years on a single coin cell battery.
Source: Bluetooth SIG Core Specification v4.0 / v4.1 / v4.2 · Last reviewed Aug 28, 2026
Specs
| Bluetooth Versions | v4.0 (2010), v4.1 (2013), v4.2 (2014) |
| Frequency Bands | 2.402 GHz to 2.480 GHz (40 RF channels @ 2 MHz spacing) |
| Channel Allocation | 3 Advertising channels (37, 38, 39) + 37 Data channels |
| Raw PHY Rate | 1 Mbps (1M PHY) |
| Application Layer Architecture | GATT (Generic Attribute Profile) / ATT (Attribute Protocol) |
| Max Packet Payload (v4.2 DLE) | 251 bytes (increased from 27 bytes) |
| Typical Battery Life | 1 to 5 years (on CR2032 coin cell) |
GATT Client-Server Model
BLE replaced the complex profile stack of Classic Bluetooth with a lightweight, hierarchical data model based on GATT. Devices act as GATT Servers or GATT Clients exposing structured Services, which contain Characteristics (data values) and Descriptors, enabling standardized interoperability for heart rate monitors, beacons, and smart sensors.
v4.2 Enhancements: Data Length Extension and LE Privacy
Bluetooth 4.2 (2014) introduced Data Length Extension (DLE), expanding maximum packet payload from 27 bytes to 251 bytes, resulting in a 2.5x increase in real-world application throughput (up to ~800 kbps). It also introduced LE Privacy 1.2, which rotates device MAC addresses at the hardware controller level to prevent tracking.