How does BLE achieve low power?

BLE uses aggressive duty cycling: the radio is on for microseconds to milliseconds and sleeps for tens to hundreds of milliseconds between events. A sensor reporting temperature every second is active for approximately 3 ms and sleeping for 997 ms, achieving single-digit microamp average current. Advertising-only devices (beacons) can run for years on a coin cell battery.

Physical Layer: 2.4 GHz, 40 channels, 1M/2M/Coded PHY. Link Layer: advertising, scanning, connection management, AFH. L2CAP: logical channels and fragmentation. ATT: Attribute Protocol for data access. GATT: Generic Attribute Profile defining services and characteristics. GAP: Generic Access Profile for roles and procedures. Application profiles built on GATT.

BLE vs Zigbee vs Thread?

BLE: phone-native (iOS/Android), point-to-point/star, best for wearables and consumer IoT. Zigbee: mesh networking, 250 kbps, requires gateway, best for home automation. Thread: mesh networking, IPv6-native, requires border router, backed by Matter. BLE has the largest ecosystem due to smartphone ubiquity.

Wireless Protocols

Bluetooth Low Energy

Bluetooth Low Energy (BLE) is a wireless protocol introduced in Bluetooth 4.0 (2010), optimized for ultra-low power IoT applications. BLE uses 40 channels at 2 MHz spacing in the 2.4 GHz ISM band with aggressive duty cycling (microsecond active periods, millisecond sleep). The GATT (Generic Attribute Profile) architecture defines services and characteristics for standardized data exchange. BLE is natively supported on all modern smartphones, making it the most accessible IoT protocol with billions of devices shipped annually.

Category: Wireless Protocols

Band: 2.4 GHz ISM

Channels: 40 × 2 MHz

Understanding BLE

BLE operates in two primary modes: advertising (broadcast, connectionless) and connected (bidirectional, acknowledged). Advertising uses channels 37, 38, 39 for discovery and data broadcast. Connections use channels 0-36 with adaptive frequency hopping (AFH) to avoid interference. The connection interval (7.5 ms to 4 s) determines how often the radio wakes for data exchange.

GATT organizes data into services containing characteristics. Each characteristic has properties (read, write, notify) and a UUID. Standard profiles (Heart Rate, Blood Pressure, HID) ensure interoperability. Custom services use 128-bit UUIDs.

BLE Power Budget

Avg current = (I_active×T_active + I_sleep×T_sleep) / T_total

Example (1 s CI, 3 ms event):
(10 mA × 3 ms + 2 μA × 997 ms) / 1000 ms
= 32 μA average
CR2032 (230 mAh): ~7,200 hrs = 300 days

BLE vs Competing IoT Protocols

Protocol	Range	Data Rate	Topology	Phone Native
BLE	10-400 m	1-2 Mbps	Star/Mesh	Yes
Zigbee	10-100 m	250 kbps	Mesh	No
Thread	10-30 m	250 kbps	Mesh (IPv6)	No
Wi-Fi HaLow	1 km	150 kbps-78 Mbps	Star	No

Common Questions

Frequently Asked Questions

How low power?

Duty cycling: 3 ms active, 997 ms sleep = 32 μA avg. Beacons: years on coin cell. Aggressive sleep is the key.

Protocol stack?

PHY→Link Layer→L2CAP→ATT→GATT→Application. Services/characteristics define data. GAP defines roles.

BLE vs Zigbee?

BLE: phone-native, star/mesh, higher data rate. Zigbee: mesh, 250 kbps, needs gateway. BLE has the biggest ecosystem.

Related Terms

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