BITS PilaniPilani | Dubai| Goa | Hyderabad

Bluetooth 4.0 :Low Energy

BITS PilaniPilani | Dubai | Goa | Hyderabad

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• New, open, short-range radio technology

• Optimized for ultra-low power

• Enable coin cell/ solar cell use cases

< 15mA peak current

< 5uA average current

• Different from Bluetooth Classic

• Marketed as Bluetooth Smart

What is Bluetooth Low Energy?

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Voice Audio Video Files State

Bluetooth ACL/HS

X Yes X Yes X

Bluetooth SCO/eSCO

Yes X X X X

Bluetooth Low Energy

X X X X Yes

WiFi Yes (VoIP) Yes Yes Yes X

WiFi Direct Yes Yes X Yes X

Short-range wireless application areas

• State: low bandwidth, low latency data

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Connection-oriented: Link maintained on

connection, even when there’s no data transfer

• Peak transmission current is typically 25 mA to

30 mA

• Cannot be powered by coin cells, solar cells or

energy harvesting ICs

• Consumes lower power than other radio

standards (except BLE)

Bluetooth Classic: Energy Usage

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Optimization for lowest possible power

consumption

• Short data packets

• Reduced TX peak current

• Reduced RX time

• Less RF channels to improve discovery and

connection time

Basic concepts of BLE

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Specifications Value

Range ~ 450 metres (open field)

Output power ~ 10mW

Maximum current ~ 15mA

Latency < 3ms

Topology Star

Connections > 2 billion

Modulation GFSK, 2.4 GHz

Robustness Adaptive frequency hopping, 24-bit CRC

Security 128-bit AES CCM

Sleep mode current ~ 1uA

BLE specifications

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Does not support streaming and file transfer

• Data Throughput isn’t meaningful

• Offers a data rate of 1Mbps

• Designed for sending small, discrete chunks of

data, called state

• Data can be triggered by local events and can

be read by clients anytime

• Commonly used for collecting data about speed,

power, location and environmental condition

Concepts of State and Data Throughput in BLE

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

BLE Architecture

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Mono Mode

• Implements only Smart

• Available in customized devices like watches

• Dual Mode

• Combines Classic and Smart

• Available on devices like phones and tablets

Bluetooth modes

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Dual Mode

Classic Dual Mode Mono Mode

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Energy per transaction

• Upper time bound of 3ms per transaction

• Estimated transmission power of 15mW

• Consumption is 45uJ

• Easily powered by 1.5V battery supplying 10mA

• Transactions per battery of 1.55V, 180mAh

• Runs for 18 hours (64,800s) at 10mA

• Corresponds to completing 21.6 million transactions

• Considering 12 transactions every minute, it’s 17280 each day

• Corresponds to 1250 days, or 41 months of continuous usage

• Fit it and forget it

Scaled Down Energy Consumption

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Parameter Bluetooth Smart (Bluetooth Classic)

Maximum Range (from Transmitting to Receiving node)

450m (100m)

Maximum Data Rate 1Mbps (3Mbps)

Number of Active Slaves Unlimited (7)

Transaction Duration 3ms (100ms)

Network Topology Star-bus (Scatternet)

Power Consumption (Relative to Classic) 0.01 to 0.5 (1)

Peak Current Consumption 15mA (25 to 30mA)

Practical significance

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Does not support file transfer

• Uncommon in the market, consequently expensive

• Few supported devices (phones and tablets)

• Typically the most high-end products of all manufacturers

Downsides of BLE

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

Temperature sensor Humidity sensor

Pulse oximeter Body thermometer

Blood glucose monitor Heart rate monitor

Physical activity monitor Emergency alarm

Simple remote control Battery status monitor

Network availability Proximity sensor (automobile)

HVAC Generic I/O

Niche of BLE

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Indicate and monitor activity

• 20 minutes yoga

• 1 hour walk, average 6 km/h

• 8 hours sleep

• Enables alerts and healthcare

• Vibrate when faster than 20 km/h

• Switch off when idle for 10 minutes

• Alert when ankles swell

Example application:Physical Activity Monitor

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

• Adapted from• NCTU, Taiwan: Yu-Chee Tseng

• Gymneus GmBH, Vienna, Austria –TIC Projects: Prototypes on

Gymnastic Health Monitoring Electronics using Bluetooth Smart