BLE – Bluetooth LE

Bluetooth Low Energy is a wireless system that was first introduced as an open standard in Tokyo in 2009. The main players in its development were Nokia and the Bluetooth Special Interest Group (SIG).

Although the two wireless technologies Bluetooth and Bluetooth Low Energy have the same name and are based on the same basic technology, there are important differences. The main difference between Bluetooth and Bluetooth LE lies in the energy consumption and the communication protocol. While “normal” Bluetooth establishes a permanent secure streaming connection for data transmission (e.g. for audio transmission between headphones and a phone), Bluetooth LE was specially developed for applications with low power consumption and the transmission of small data packets. Bluetooth LE is therefore suitable for battery-powered devices and long operating times, and can be integrated into wearables, medical equipment, and IoT devices, for example.

When Bluetooth was developed in the 1990s, the focus was not on energy efficiency. Bluetooth was intended to transmit large data packets at high speeds over short distances. While Bluetooth typically supports data rates of several megabits per second, the data rate of Bluetooth LE is in the range of a few kilobits to a maximum of 1 Mbit per second.

While Bluetooth can achieve a range of up to 100 meters, the range of Bluetooth LE is typically around 10 to 50 meters. Due to these technological differences, the areas of application also vary, as explained further in the article.

Bluetooth LE uses the license-free 2.4 GHz band (ISM band) with 80 different 1 MHz channels between 2400 and 2483.5 MHz. ISM stands for Industrial, Scientific, and Medical band. WLAN uses the same frequency, which can lead to problems with coexistence, as will be explained later.

The specifications, as well as further, and new developments in wireless technology, are driven by SIG. The companies Apple, Microsoft, and Intel are also members of this association.

Bluetooth 5 was officially introduced by the SIG in 2016 as the fifth version of the Bluetooth standard. Version 5 increased the maximum data rate in Bluetooth LE applications to two megabits per second. The free-field range of 50 to around 200 meters, and the transmission power of 10 to 100 milliwatts, have been significantly increased with version 5. The doubling of the data rate makes Bluetooth LE faster, however, the higher range also results in lower data rates of 500 kilobits per second or just 125 kilobits per second, depending on the set transmission mode.

Bluetooth 5.4 was released in February 2023. Bluetooth 6 is expected to be the next development step. It is expected that Bluetooth 6 will use the 6 GHz frequency band. Similar to ultra-wideband (UWB), this could enable more precise localization. In addition, coexistence with Wi-Fi 6E is to be further improved.

The net data rate of Bluetooth LE is 0.27 megabits per second. Bluetooth-enabled devices can establish a connection within three milliseconds and complete a data transfer in six milliseconds without any delays. The short signal pulses during data transmission contribute to the low power consumption of Bluetooth LE devices with a maximum of 10 milliwatts. Data security is guaranteed by the 128-bit Advanced Encryption Standard (AES).

Bluetooth LE is suitable for transmitting small data packets in quick succession due to the modulation method used. Bluetooth Low Energy is modulated using Gaussian Frequency Shift Keying (GFSK) and frequency hopping (FHSS). GFSK is a modulation method with modified frequency shift keying (FSK) in which a Gaussian filter is used. During frequency shift keying, the transmitted carrier signal is filtered so that the high-frequency components of the carrier signal are suppressed, and less bandwidth is required to transmit the signal.

FHSS ensures interference-free transmission and prevents collisions with other signal transmissions by transmitting at 1,600 frequency steps per second between predefined frequency channels. For this purpose, the frequency band is divided into 40 channels with a width of two megahertz. Three of the 40 channels are reserved for communication between Bluetooth LE devices. One frequency band at both the lower and upper end of the frequency range serves as a safety band to neighboring frequency ranges.

With version 5.1, the Bluetooth specification has been expanded to include two functions for direction and position detection. Depending on the design of a Bluetooth LE application, it is possible to locate objects indoors with centimeter precision. Bluetooth Direction Finding was the main feature of the Bluetooth Core Specification 5.1 in 2019. This function supports localization services that previously only used a technology based on signal strength with Received Signal Strength Indication (RSSI). Bluetooth LE-based real-time localization or positioning enables the tracking of objects in a variety of new and optimized applications for real-time location systems (RTLS).

Depending on the implementation, Bluetooth LE localization can be used for 2D or 3D localization. Bluetooth Direction Finding is based on the two key concepts of Angle of Arrival (AoA) and Angle of Departure (AoD). This utilizes the angular phase shifts that occur between the antennas when receiving (AoA) or transmitting (AoD) RF signals. By using antenna arrays on both sides of the communication link, the phase shift data can be determined and used to calculate the position.

Various methods are used for positioning with Bluetooth LE. Triangulation and signal strength measurement are two such examples.

With triangulation, also known as Bluetooth LE AoA (Angle of Arrival), several Bluetooth LE receivers are distributed in the vicinity. Each receiver receives the signals from a Bluetooth LE device and determines the distance between it and the device. By using multiple receivers and their relative positions, the locations of Bluetooth LE devices can be triangulated.

The second method is based on measuring the signal strength (Received Signal Strength Indicator – RSSI) of the Bluetooth LE signal at different locations. As the signal strength decreases with increasing distance, the distance between a Bluetooth LE device and a receiver can be estimated by the Positioning Engine based on the measured signal strength. By combining the measurements of several receivers and the signal strength, the location of the Bluetooth LE device can be calculated.

The decision between Bluetooth LE and Ultra Wideband (UWB) depends heavily on the individual requirements and application scenarios, as both technologies have different properties and applications. Overall, there is no fundamentally better technology, as it depends on the specific requirements and priorities of the application. Bluetooth LE is well suited for applications with low power consumption and limited space, while UWB is suitable for applications with high accuracy and fast data transmission.

These are the most important distinctions:

• Bluetooth LE is known for its low power consumption, which makes it ideal for battery-powered devices such as wearables, IoT devices, and beacons. It is well suited for applications in limited areas such as indoor navigation or point-of-sale systems, as the range is typically limited. The widespread use and support of Bluetooth LE by most mobile devices facilitates integration and interoperability. In addition, Bluetooth LE is typically less expensive than UWB and therefore suitable for applications where cost is a factor. Bluetooth LE 6 is likely to increase competition with UWB as the real-time localization capability is expected to be further developed.
• UWB offers extremely high spatial accuracy in the centimeter range. This makes UWB ideal for precise indoor navigation, the real-time positioning of objects, and precise tracking. UWB has a better penetration of walls and obstacles. It offers a higher data rate than Bluetooth LE and is therefore suitable for applications where large volumes of data need to be transmitted quickly, like audio or video transmissions, for example. However, UWB technology is generally more expensive than a Bluetooth LE-based system due to the complex technology and higher hardware and development costs.

The possible uses of Bluetooth LE range from applications in the consumer electronics sector to proximity marketing and tracking solutions in healthcare, sports, logistics, and industry. In buildings or private homes, users also utilize the energy-saving communication technology for tracking purposes. As the following list shows, the possible applications are wide-ranging, and range from networked fitness equipment to asset tracking solutions in logistics and industrial production.

• Bluetooth LE is commonly used in wearables such as fitness trackers, smart watches, and smart clothing, to transmit data such as heart rate, step count, and sleep patterns to mobile applications.
• Bluetooth LE can be used in smart home devices such as smart light bulbs, thermostats, door locks, and security systems to establish a wireless connection to smartphones or other control devices.
• Bluetooth LE beacons are small, battery-powered devices that continuously emit signals to detect smartphones in their vicinity. This technology is used in retail stores, museums, event venues, and other locations for location-based services, advertising, and notifications.
• In healthcare, Bluetooth LE is used for applications such as wireless patient monitoring, medication tracking, and the remote monitoring of medical devices.
• In industrial automation, Bluetooth LE is used to network and control wireless sensors, actuators, and devices in factories and other industrial environments.
• Bluetooth LE is used to track and locate objects in indoor environments such as warehouses, hospitals, and airports.
• In logistics, Bluetooth LE can safeguard the cold chain and monitor the temperature of the goods being transported in real time.
• Bluetooth LE enables authentication at charging stations and thus supports electromobility and convenience for users.
• In the automotive industry, Bluetooth LE is used for applications such as keyless entry systems, vehicle diagnostics, and wireless connections to mobile devices.
• Headphones, speakers, and remote controls often use Bluetooth LE for wireless communication with other devices.

According to SIG, the volume of devices with a Bluetooth LE chip that is shipped annually will reach 6.2 billion in 2024. By 2025, there will be 6.4 billion Bluetooth LE devices, and more than 7 billion by 2026. The reason for this widespread use and strong growth is easy to explain. Every smartphone, tablet, or notebook is now equipped with a Bluetooth chip.

The outbreak of the global COVID-19 pandemic led to a decline in demand for Bluetooth LE ICs in all geographical regions, compared to pre-pandemic demand. Meanwhile, the Bluetooth LE market is back to the levels from 2019. Key industries leading the adoption of BLE technology include healthcare, consumer electronics, and automotive. The US, China, and Japan are strongly driving demand for Bluetooth LE technologies, mainly because they are increasingly focusing on energy-efficient solutions.

The American consulting and market research company ‘Allied Market Research’ forecasts that sales of Bluetooth LE beacons will increase by almost 37 percent by 2030. Other market observers are even predicting growth of 50 percent.

By the end of 2024, all devices should be 100 percent dual-mode capable, i.e. support Bluetooth Classic and Bluetooth LE. The two technologies – Classic and LE – differ in terms of the number and bandwidth of the channels used, and the network topologies supported.

Bluetooth LE offers a number of benefits that make it a popular choice for a variety of applications. One of the main benefits of Bluetooth LE is its low power consumption, designed specifically for battery-powered devices such as wearables, IoT devices, and sensors. This allows these devices to operate for long periods of time without changing batteries or recharging. In addition, Bluetooth LE chips are small, inexpensive, and easy to integrate into devices, making them an attractive option for manufacturers looking to integrate wireless connectivity into their products.

Furthermore, Bluetooth LE is widely used and interoperable, as it is supported by most mobile devices and computers, facilitating interoperability and the development of applications. In addition, Bluetooth LE offers a variety of profiles and services that make it suitable for a wide range of applications. The connection between Bluetooth LE devices is fast, enabling a smooth and seamless user experience.

Bluetooth LE offers various security features, including encryption and authentication, to protect communication between devices and ensure user privacy. Overall, Bluetooth LE is a reliable, energy-efficient, and cost-effective wireless connectivity solution suitable for a wide range of applications in IoT, wearables, healthcare, retail, entertainment, and more.

Bluetooth Mesh is a standard for mesh computer networks. The Mesh BLE specification is based on Bluetooth Low Energy and was published in 2017. The standard enables many-to-many communication via Bluetooth radio. Bluetooth Mesh networks ensure many-to-many (m2m) device communication. They are ideal for complex device networks.

The advantages: Scalability, reliability, and security. This makes Bluetooth mesh suitable for industrial requirements and intelligent building infrastructures in which dozens, hundreds, or thousands of Internet of Things (IoT) devices need to communicate with each other, with great precision. The areas of application range from digitalization in industry to digitalization in healthcare, airports, digitalization in retail, and digitalization in logistics.

The advantage of mesh communication is that not every beacon has to be within range of a gateway that transmits its data to the cloud application. This means that fewer gateways are required to monitor an industrial plant, for example.

The disadvantage is that mesh data transmission from beacon to beacon increases their energy consumption, and therefore, the batteries need to be replaced or recharged more frequently. Since 2017, Bluetooth Mesh has played a crucial role in the development of emerging markets such as smart buildings, Industry 4.0, and smart cities.

Bluetooth LE beacons can be used not only for position determination in real-time localization (RTLS), for wayfinding, or for location-based information and advertising, but also as mobile sensors with contactless data transmission for Internet of Things (IoT) applications. Thanks to their independent power supply via battery or rechargeable battery, beacons have enough energy to operate active sensors.

Common applications include vibration sensors for monitoring electric motors in industry, or temperature sensors for monitoring the ideal ambient or cooling temperature. The beacon signals are transmitted via Bluetooth LE and gateways, which communicate via WiFi or LAN with a cloud application that interprets the signals and initiates reactive or preventive measures if necessary.