BLE : BLUETOOTH LOW ENERGY

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What is BLE (Bluetooth Low Energy) and how does it work?

In a hyper-connected world, Bluetooth Low Energy, also known as BLE, provides a better connectivity solution for connected objects.

This technology was introduced in 2010 with the release of Bluetooth Core Specification version 4.0. Thanks to its low power consumption, BLE is an alternative to conventional Bluetooth in the IOT world, with the same range.

Compared with conventional Bluetooth, BLE offers a data rate of the same order of magnitude (up to 2Mb/s), while consuming 10 times less energy. This makes it possible to integrate this technology into new types of equipment, such as watches, medical monitoring devices and sports sensors.

The main reason for the incredible success of this technology is the enormous flexibility it offers developers. The technology offers a complete set of solutions tailored to meet the growing need for wireless connectivity.

BLE is designed for extremely low-power operation. Transmitting data over 40 channels in the license-free 2.4 GHz ISM frequency band. It supports several communication topologies, ranging from point-to-point to broadcast and, more recently, mesh, enabling the creation of large-scale, reliable device networks. Although initially known for its device communication capabilities, BLE is now widely used as a device positioning technology to meet the growing demand for high-precision indoor location services. It now includes features that enable one device to determine the presence, distance and direction of another.

How does BLE consume less energy?

BLE uses the same radio wavebands as Bluetooth, enabling two devices to exchange data in the same way.

The difference is that BLE devices remain asleep between connections. They are also designed to communicate for just a few seconds when they connect.

This contrasts with "classic Bluetooth", which is always on and designed for continuous communication that often lasts for hours.

Stopping between transmissions allows BLE devices to communicate efficiently at a fraction of the power. It's not uncommon for a BLE device to last a year on a single battery.

Protocols :

The BLE protocol is based on a number of layers:

Building on the original Bluetooth specification, the Bluetooth SIG defines several profiles (specifications for how a device operates in a particular application) for low-energy devices. Manufacturers are expected to implement the appropriate specifications for their device to ensure compatibility. A device may contain implementations of several profiles. The majority of current low-energy application profiles are based on the Generic Attribute Profile (GATT), a general specification for sending and receiving short data called attributes over a low-energy link.

The Generic Access Profile (GAP), Generic Attribute Protocol (GATT ) and Attribute Protocol (ATT) layers are essential for data exchange:

GAP (Generic Access Profile): this layer is responsible for establishing the link and connection control between two devices. The GAP is what makes a device visible to the outside world, and determines how two devices can (or cannot) interact. The GAP defines different roles for devices, including central devices and peripheral devices.

GATT (Generic Attribute Profile): this is a set of rules describing how to structure, present and transfer data. The structure defines the basic elements, such as services and features, used in a profile.

ATT (Attribute Protocol): ATT is based on a client/server relationship. The server holds the information (such as sensor values). The client is the person who wants to access this information. ATT enables a server to expose a set of attributes to a client. An attribute is a value associated with the following three properties: an attribute type defined by a UUID, an attribute descriptor and a set of authorizations.

Note: The LL (Link Layer) introduces two modes: master and slave.

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Bluetooth evolution :

Technology is constantly evolving, and Bluetooth is one of the main technologies that has redefined itself over the years. Bluetooth has been one of the de facto standards for wireless communication between low-power devices.

Bluetooth Low Energy is distinct from the previous (often referred to as "classic") Bluetooth Basic Rate/Enhanced Data Rate (BR/EDR) protocol, but both protocols can be supported by a single device: the Bluetooth 4.0 specification allows devices to implement either one or both LE and BR/EDR systems.

Bluetooth Low Energy uses the same 2.4 GHz radio frequencies as conventional Bluetooth, enabling dual-mode devices to share a single radio antenna, but uses a simpler modulation system.

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Bluetooth Version 5.0

• Year of release - 2016
• Data transfer rate - 2 Mbps
• Range - 200 metres outdoors, 40 metres indoors

The improved Bluetooth 5.0 specification was released two years after Bluetooth 4.2. However, it contains a wide range of exciting new features. The changes made to this version made it an even more exciting option for those using a lot of wireless devices for a wide range of application areas.

High data transfer rates

The first and main improvements introduced on Bluetooth version 5.0 include increased data transfer speeds. The optimum conditions of 2 Mbps may prove to be an excellent option that you'll find impressive and efficient. Another improvement brought about by Bluetooth 5.0 would include the resolution of latency problems.

Enhanced audio quality

Bluetooth 5.0 has also improved audio quality on connected devices. Once again, faster transmissions are essential to access better audio quality. Ideally, there would be fewer lags and delays in audio transmissions. 

Longer range

For each Bluetooth version, it is possible to face a significant problem in terms of coverage. In addition, the range with which Bluetooth devices operate can further affect the quality of data transfer. However, Bluetooth version 5.0 brings a wide range of improvements.

This is only because Bluetooth 5.0 has improved the connectivity range up to 200 meters. Indoors, the range is around 40 meters. In most ideal conditions, there's no need to worry about walls hindering transmission between the two wireless devices.

Bluetooth 5.1 - What are the new features?

• Release year - 2019
• Data transfer rate - 2 Mbps
• Range - 200 metres outdoors, 40 metres indoors

Bluetooth 5.1 is the Bluetooth technology of 2019. This version has added a host of new features and has done much to improve the user experience.

There's not a huge difference between Bluetooth 5.0 and 5.1 in terms of features such as range, data transfer speeds and other functionality, but there are some changes under the hood that are pretty impressive and rewarding at their core.

Better direction detection :

Bluetooth has never before been used as a means of detecting the direction or location of devices. Bluetooth 5.1 improves the direction detection capability of Bluetooth devices. By correctly detecting the strength of the received signal, it is possible to estimate the radius of a device.

Determining direction using angle of arrival (AoA)

In the angle-of-arrival (AoA) method, the device to which the direction is determined transmits a special direction-finding signal using a single antenna. The receiving device, on the other hand, has several antennae arranged in an array. As the transmitted signal passes through the array, the receiving device sees a phase difference in the signal due to the difference in distance between each of the antennas in its array and the transmitting antenna. The receiving device takes IQ samples of the signal while switching between the active antennas in the array. Based on the IQ sample data, the receiving device can calculate the relative direction of the signal. The AoA direction-finding method is intended for use with the RTLS system, as well as with proximity solutions such as item search and point-of-interest (PoI) information services.

Determining direction using departure angle(AoD)

In the angle-of-departure (AoD) method, the device to which the direction is determined transmits a special signal using several antennae arranged in an array. The receiving device has a single antenna.

When the multiple signals from the transmitting device pass through the antenna of the receiving device, the latter takes IQ samples. Based on the IQ sample data, the receiving device can calculate the relative direction of the signal. The AoD method of direction finding is intended for use in IPS solutions, such as those used for orientation.

Reduced energy consumption

Bluetooth 5.0 itself was designed to consume less energy. The feature has now been enhanced on the new Bluetooth 5.1 version. 

This is made possible by improved caching of the generic attribute profile. This will enable service discovery when devices connect. It will also give access to faster connection capacity.

Improved Connexion advertising capacity

This is one of the main options introduced with Bluetooth 5.1, and translates into a powerful random indexing of advertising channels. Previous versions of Bluetooth ran cycles 37, 38 and 39 in chronological order. With Bluetooth 5.1, any channel can be randomly selected.

This will allow multiple Bluetooth devices to be connected without worrying about interference of any kind. 

Bluetooth 5.2 - What's new?

The Bluetooth SIG has released version 5.2 of the Bluetooth Core specification on December 31, 2019. The new specification enables more data to be transmitted over similar or lower bandwidth devices such as fitness bands. The new LC3 codec introduces better compression and decompression (Input & Output). The LC3 codec should also help transmit lossless audio using lower bandwidth.

Version 5.2's Enhanced Attribute protocol facilitates parallel transmission between several Bluetooth-enabled devices simultaneously. 

The inclusion of isochronous channels introduces a " dual audio function " that should enable multiple paired devices to operate from a single source. 

In connections, each stream is called a connected isochronous stream (CIS). When CIS are to be synchronized, such as those sent to the left and right headphones, they are configured to form part of a single group called a connected isochronous group (CIG).

Streams that are part of the same CIG share the synchronization reference data required for synchronized rendering of streams on multiple receivers. CIGs enable bidirectional data transfer, for example in headphones containing microphones, and the sending of control data to the source device.

For connectionless communication (broadcasts), a group of synchronized streams can broadcast data from a single source to several receivers. Each stream is called a broadcast isochronous stream (BIS). 

This new specification adds the following new features:

• Enhanced Attribute Protocol (EATT), an improved version of ATT (Attribute Protocol)
• LE power supply control
• LE isochronous channels
• LE Audio is designed with the latest 5.2 features in mind.

The Bluetooth SIG announced BT LE Audio in January 2020. Compared to standard Bluetooth audio, Bluetooth Low Energy Audio reduces battery consumption and implements a standardized audio transmission system over BT LE. What's more, Bluetooth LE Audio also enables one-to-many and many-to-one broadcasts. It allows multiple receivers from a single source, or a single receiver for multiple sources. The latest LC3 codec is used. BLE Audio would also add support for hearing aids.

1. Enhanced Attribute Protocol (EATT) :

Bluetooth version 5.2 is equipped with an advanced version of the original ATT (Attribute Protocol) known as enhanced Attribute Protocol (EATT). Basically, ATT works sequentially, meaning that transactions are carried out one at a time. However, EATT can perform simultaneous or parallel transactions between a Bluetooth LE client and a server.

EATT streamlines the decomposition of L2CAP packages from various applications and their merging into smaller, more manageable pieces. As a result, transactions from two or more applications can be carried out simultaneously.

EATT enhances the user experience when multiple applications are running on the same Bluetooth LE stack. It also reduces overall latency. It's important to note that EATT is optional according to the specification. It requires an encrypted connection between the two Bluetooth LE devices, making it more secure than ATT.

2. LE power supply control function (LEPC) :

LE power control manages power transmission between two connected devices supporting Bluetooth version 5.2. Typically, wireless receivers are supplied with an optimum received signal power range that offers superior signal quality. Receivers whose signal strength is below or above this optimum range may experience problems when decoding signals.

With LEPC, a receiving device can monitor the RSSI signal from its partner device and request a change in the transmit power level in both directions. Instead, a transmitter can adjust the transfer power and transmit this information to the receiver.

As a result, it promises to keep both devices within their optimum signal ranges. What's more, it reduces errors at the receiving end and cuts power consumption thanks to dynamic power management.

Power management via LEPC also improves coexistence with other signals in the 2.4 GHz band, including Zigbee and WiFi signals.

3. Isochronous channels (ISOC) :

One important feature upgrade is support for isochronous channels. These channels can be used on any LE physical layer variant. They can be used on 1M, 2M and LE S=2 and S=8 coded configurations.

The latest Bluetooth 5.2 isochronous channels support data retransmission for GCI and CIG, but in different ways. For CIGs, the master transmits a packet to the slave, then the slave returns with a packet for each sub-event. For GBI, only the master sends a packet for each sub-event. ISO intervals can vary from 5 milliseconds to 4 seconds.

Isochronous channels support connection-oriented and connectionless communication:

I. Connection-oriented communication :

When this mode is activated, each data stream is called a connected isochronous stream (CIS). When CISs need to be synchronized, they are linked in a connected isochronous group (CIG). These CIS are part of the identical CIG, sharing reference data to broadcast synchronously to multiple receivers.

Devices supporting Bluetooth 5.2 can also configure multiple RICs. In addition, RICs facilitate bi-directional data transfer, making it easier for devices to transmit control data to the source device.

II. Connectionless communication :

When this mode is activated, a single source, such as a smart TV, can broadcast its data to several synchronized streams. Each stream is known as a broadcast isochronous stream (BIS), while each group of BISes is known as a broadcast isochronous group (BIG). Similar to BIGs, Bluetooth 5.2 devices can configure multiple BIGs.

‍4. LE Audio :

LE Audio is a significant improvement on Bluetooth LE and Bluetooth Classic. It uses reduced power and bandwidth to deliver superior audio transmissions. As a result, it improves quality and extends device battery life.

LC3 optimizes the existing Bluetooth LE codec by compressing audio transmissions and reducing them to very extreme bit rates without adversely affecting audio quality.Since LC3 is implemented with multi-stream capabilities and support for multiple synchronous connections (by default), True Wireless users can benefit from improved battery life and faster pairing. Improved battery life means greater efficiency and extended autonomy. This makes the Bluetooth standard useful for a pair of wireless headphones and a voice-activated smart speaker.

Support for Piconet Link Manager mode is added. This allows devices to connect without relaying to avoid interference.

Bluetooth 5.3 :

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On July 13, 2021, the Bluetooth SIG released version 5.3 of the Bluetooth Core specification. This Bluetooth version offers lower latency, lower interference, improved battery life and enhanced security.

It comes with the following feature enhancements:

• Connection undervaluation
• Improved channel classification
• Periodic publication interval
• Improvements to encryption key size control

Alternative MAC and PHY (AMP) extensions are removed in Bluetooth 5.3.

1. Connection underestimation :

Specific devices spend much of their time in a low duty cycle connection to save energy. However, when a higher bandwidth is required to support a particular application use case, connection settings should be changed as quickly as possible.

Connection undervaluation speeds up connection parameter updates with minimal delay. It offers a better user experience and simultaneously retains the energy-saving features of low duty cycle connections. Specifically, this can be useful in innovative medical devices such as a smart glucose meter.

2. Improved channel classification :

Bluetooth LE devices can now offer a connected central device with radio channel classification data. This data can be used by the central device when selecting channels for adaptive frequency hopping.

Improved channel classification improves reliability and throughput by reducing the risk of interference occurring at the peripheral. Using this feature, an example of use could be a vibration sensor connected to the smartphone and an industrial rotating machine. The vibration sensor functions as a peripheral, while the smartphone functions as a central device. Condition monitoring personnel experience interference of different magnitudes and from a variety of sources.

3. Periodic improvement of advertising :

The AdvDataInfo (ADI) field of the standard extended advertising payload format can now be implemented in AUX_SYNC_IND protocol data units (PDUs). These units are broadcast when a device performs periodic advertising.

Bluetooth Low Energy (LE) controllers can now use ADI field information to identify packets that include retransmitted copies of identical or semantically matching data. In addition, it suppresses these packets to avoid redundant processing on the nodes. In this way, overall throughput is not affected by retransmitted packets.

4. Improved control of encryption key size :

Encryption key sizes are managed by the controllers of devices connected via Bluetooth BR/EDR. This modification enables a host to inform its Bluetooth BR/EDR controller of the minimum acceptable key size via the Host Controller Interface (HCI).

This enhancement enables Bluetooth BR/EDR controllers to more effectively inform the host of the result of key-length negotiations. This new Bluetooth 5.3 feature will be most beneficial for IoT applications such as access control, wearable medical devices, door locks and commercial lighting.

5 Removing the MAC and PHY (AMP) alternative extension :

The AMP extension (Alternate Media Access Control and Physical Layer Extension) enables a Bluetooth system to incorporate one or more secondary controllers and a main Bluetooth BR/EDR controller. But in high-quality Bluetooth products, this extension is rarely found. Consequently, the Bluetooth SIG has removed this feature from the Bluetooth 5.3 specification. But this new version can qualify products that use AMP over an earlier version of Bluetooth Core Specification.

Solutions to meet market needs :

Bluetooth Low Energy provides complete, customized solutions to meet the growing needs of wireless connectivity. After audio streaming, Bluetooth technology has extended to low-power data transfer. Today, this technology meets market demand for indoor location services and large-scale, reliable device networks.

Streaming Audio

By removing the hassle of wires on headphones, headphones, speakers, etc., Bluetooth has revolutionized audio and changed the way we use media forever.

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Key use cases :

WIRELESS HEADSETS

The original wireless audio device, from padded earphones to true wireless headphones, Bluetooth headsets are now an indispensable accessory for cell phones.

WIRELESS SPEAKERS

Whether it's a high-fidelity home entertainment system or a portable option for the beach or park, there's a speaker for every occasion, in every conceivable shape and size.

ON-BOARD SYSTEMS

Bluetooth in-car infotainment systems link up with drivers' smartphones to enable audio streaming and hands-free calling, allowing drivers to concentrate on what matters most.

Data transfer :

From household appliances and fitness trackers to health sensors and medical innovations, Bluetooth® technology connects billions of everyday devices and enables the invention of countless others.

From fitness trackers and health and wellness monitors to toys and tools, millions of new Bluetooth devices with low power consumption and data transfer are freeing consumers from wires every year.

SPORT & FITNESS

Bluetooth technology powers wearable devices such as fitness trackers and smartwatches that pop up all over wrists to monitor steps, exercise, activity and sleep.

PC PERIPHERALS AND ACCESSORIES

One of the driving forces behind Bluetooth technology is the absence of wires. Whether it's a keyboard, touchpad or mouse, computers no longer need wires to stay connected.

HEALTH

From blood pressure monitors to portable ultrasound scanners and X-ray imaging systems, Bluetooth technology helps people monitor and improve their overall well-being, while making it easier for healthcare professionals to deliver quality care.

Connect devices :

Control, Monitor, Automate, Innovate

The Bluetooth mesh network enables many-to-many (m:m) device communications, and is ideally suited to the creation of control, monitoring and automation systems where dozens, hundreds or thousands of devices need to communicate with each other reliably and securely.

The Bluetooth mesh network is optimized to create large-scale device networks that make whole-building automation a reality.

CONTROL SYSTEMS

The Bluetooth mesh network is rapidly being adopted as the wireless communication platform of choice in a number of control systems, including advanced lighting solutions for the smart building and smart industry markets.

MONITORING SYSTEMS

Bluetooth Wireless Sensor Networks (WSNs) monitor light, temperature, humidity and occupancy to improve employee productivity, reduce building operating costs or better meet the condition and maintenance requirements of production equipment to reduce unplanned downtime.

AUTOMATION SYSTEMS

Bluetooth technology enables the automation of essential building systems, including HVAC (heating, ventilation and air conditioning), lighting and security, to exploit energy savings, reduce operating costs and improve the lifespan of a building's core systems.

Localization service :

Towards precise positioning :

Initially known for its device communication capabilities, Bluetooth® technology is now widely used as a device positioning technology to meet the growing demand for high-precision indoor location services. By enabling one device to determine the presence, distance and direction of another, Bluetooth technology offers flexibility unlike any other positioning radio, allowing building managers and owners to adapt indoor positioning solutions to variable and changing building needs.

Developers and implementers worldwide are turning to the flexibility of Bluetooth® technology to enable powerful, low-cost proximity solutions and positioning systems.

Tracking :

Bluetooth technology is fuelling the rapid growth of real-time location system (RTLS) solutions used to track assets and people, whether locating tools and workers in a warehouse, or medical devices and patients in a hospital.

Recent improvements :

Reinventing wireless communication

Here are some of the latest enhancements to Bluetooth technology.

Bluetooth® LE Audio

LE Audio will improve Bluetooth audio performance, add support for hearing aids and introduce Bluetooth® audio sharing, an innovative new Bluetooth use case with the potential to once again change the way we experience audio and connect with the world around us.

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Bluetooth® Direction Finding

Introduced in January 2019, direction finding enables devices to determine the direction of a Bluetooth Low Energy (LE) signal. Supporting both angle-of-arrival (AoA) and angle-of-departure (AoD) methods of estimating signal direction, this feature allows Bluetooth proximity solutions to add directional capabilities that enhance the user experience and Bluetooth positioning systems to achieve centimeter accuracy, enabling Bluetooth technology to address the full range of positioning use cases, from common low-resolution systems to the most precise systems.

Bluetooth® Mesh Networking

Introduced in July 2017, mesh networking enables the creation of large-scale device networks. It is ideally suited to control, monitoring and automation systems where hundreds or thousands of devices need to communicate with each other. 

Bluetooth® Long Range

Introduced in December 2016, the LE 2M PHY doubles the data rate that can be achieved between Bluetooth Low Energy (LE) devices from the original LE 1M PHY. The LE 2M PHY improves data transfer performance and offers greater spectral efficiency for the growing number of IoT devices that consumers are connecting to their smartphones, including wearable sports and fitness devices as well as Bluetooth medical devices that need to transmit critical information or administer medication more frequently and with greater precision. In exchange for a doubling of data rate, the LE 2M PHY can achieve a range of around eighty percent of the original LE 1M PHY.

Bluetooth® Extended Advertising

Introduced in December 2016, Extended Advertising added a new approach to Bluetooth LE advertising designed to dramatically improve efficiency and reliability when broadcasting large amounts of data. With this introduction, LE Advertising now supports two modes of operation; Legacy Advertising (the original mode) and Extended Advertising. The main highlights of extended advertising include the increase in the maximum size of advertising data from 31 bytes to 254 bytes, the offloading of advertising data transmission to all 37 data channels, and the synchronization of advertising data transmission between sending and receiving devices.

What is a Bluetooth beacon?

Bluetooth beacons are hardware transmitters - a class of Bluetooth Low Energy (LE) devices that broadcast their identifier to nearby portable electronic devices. The technology enables smartphones, tablets and other devices to perform actions when in proximity to a beacon.

Bluetooth beacons use low-energy Bluetooth proximity detection to transmit a unique universal identifier captured by a compatible application or operating system. The identifier and several bytes sent with it can be used to determine the physical location of the device, track customers or trigger a location-based action on the device, such as a social network check-in or push notification.

Beacon protocols :

iBeacon: this is a protocol developed by Apple and presented at the Apple Worldwide Developers Conference in 2013.

AltBeacon: AltBeacon is an open source alternative to iBeacon created by Radius Networks

URIBeacon: URIBeacons are different from iBeacons and AltBeacons in that, rather than broadcasting an identifier, they send a URL that can be understood immediately.

Eddystone: Google's standard for Bluetooth beacon.

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