Bluetooth Low Energy (BLE) is the main feature of the Bluetooth specification v4.0 released in December 2009. BLE is a new protocol that allows for long-term operation of Bluetooth devices that transmit low volumes of data. BLE enables smaller form factors, better power optimization, and the ability to operate on a small power cell for several years.
Differences Between Classic Bluetooth and BLE
The classic Bluetooth specification defines a uniform structure for a wide range of devices that connect to each other. Bluetooth operates primarily using ad hoc piconets. A master device controls up to seven slaves per piconet; the slaves communicate with the master device but they do not communicate with each other. However, a slave device may participate in one or more piconets, essentially a collection of devices connected via Bluetooth. A summary of classic Bluetooth topology with multiple piconets, called scatternet, can be found below.
In a BLE topology, the slaves each communicate on a separate physical channel with the master. Unlike a classic Bluetooth piconet, where all slaves listen for incoming connections and therefore need to be on constant standby, a BLE slave invites connections and so is in total control of when to consume power. A BLE master, which is assumed to have less power constraints, will listen for advertisements and make connections on the back of an advertisement packet. A diagram of this can be found below.
While BLE inherits the operating spectrum and the basic structure of the communication protocol from the classic Bluetooth protocol, BLE implements a new lightweight Link Layer that provides ultra-low power idle mode operation, fast device discovery, and reliable and secure point-to-multipoint data transfers. As a result, BLE offers substantially lower peak, average, and idle-mode power consumption than classic Bluetooth. Averaged over time, BLE consumes only 10% of the power consumed by classic Bluetooth. This is a key characteristic that will greatly impact the adoption of this technology.
The table below compares classic Bluetooth and BLE.
Bluetooth Low Energy
|Distance/Range||100 m (330 ft)||50 m (160 ft)|
|Over the Air Data Rate||1 – 3 Mbit/s||1 Mbit/s|
|Application Throughput||0.7 – 2.1 Mbit/s||0.27 Mbit/s|
|Active Slaves||7||Not defined; implementation dependent|
|Security||56 / 128-bit and application layer user defined||128-bit AES with Counter Mode CBC-MAC and application layer user defined|
|Robustness||Adaptive fast frequency hopping, FEC, fast ACK||Adaptive frequency hopping, Lazy Acknowledgement, 24-bit CRC, 32-bit Message Integrity Check|
|Latency (from a non connected state)||Typically 100 ms||6 ms|
|Total time to send data (depending battery life)||100 ms||3 ms, less than 3 ms|
|Network topology||Scatternet (See figures above)||Star-bus (See figures above)|
|Power consumption||1 as the reference||0.01 to 0.5 (depending on the use case)|
|Peak current consumption||Less than 30 mA||Less than 20 mA|
In addition to its ultra-low power consumption, BLE has several unique features that set it apart from other available wireless technologies, including:
- Interoperability: Like classic Bluetooth devices, BLE devices follow standards set by the Bluetooth Special Interest Group (SIG), and BLE devices from different manufacturers interoperate.
- Robustness: BLE uses fast frequency hopping to secure a robust transmission even in the presence of other wireless technologies.
- Ease of Use: BLE has been developed so that it is straightforward for designers to implement it in a variety of different applications. Laird makes this even easier with the smartBASIC embedded programming language.
- Latency: The total time to send small chunks of data is generally fewer than 6 ms, and as low as 3 ms (compared to 100 ms with classic Bluetooth).
- Range: Thanks to an increased modulation index, BLE technology offers greater range (up to 200 feet and beyond, in ideal environments) than to classic Bluetooth offers.
Industries and Markets
BLE’s advantages over classic Bluetooth open up new potential industries and market to BLE. The Bluetooth SIG is promoting the use of BLE for wireless personal area networks (PANs) serving healthcare, smart energy, home systems, and other industries that want devices to operate for extended periods on a AAA or tiny coin cell battery. BLE applications include:
- Fitness: BLE allows users to effortlessly track various biometrics via smart-watches and wireless sensors and communicate that information with a mobile device such as a smartphone.
- Healthcare: BLE technology is suitable for medical applications that transmit small amounts of data periodically.
- Industrial and Home Automation: BLE provides a simple interface for control or light bulbs, garage door openers, general instrumentation and meter reading using smartphones or gateway devices.
- Security: Asset tags or proximity tags that ensure you can locate, track and trace items or provide a concept of a ‘virtual leash’ for location based monitoring of devices, people, etc.
- Smart Energy/Smart Grids: BLE offers low-power device and appliance connections to a smart grid.
*Source of Figures: Georgakakis, Emmanouil et. al. An Analysis of Bluetooth, Zigbee and Bluetooth Low Energy and Their Use in WBANs. Found, here.
 Wireless Communication and Healthcare, James C. Lin, University of Chicago
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