Bluetooth Low Energy (BLE) is a wireless communication technology specifically designed for applications with low energy consumption. Originally introduced in 2009 as an extension of Bluetooth 4.0 and now available in version 5.4, BLE has gained significant importance in various fields, particularly in the Internet of Things (IoT). In this article, our Xperts explore the technical details of BLE, the various profiles, and how BLE is utilised in IoT.

Key Characteristics of BLE

BLE differs from traditional Bluetooth through a variety of technical specifications, making it particularly suitable for energy-efficient applications:

• Maximum data rate: 2 Mbps (theoretical)
• Practical data rate: 0.27 Mbps
• Energy consumption: Typically in the range of µA to mA
• Frequency band: 2.4 GHz ISM band, operating on 40 channels like Wi-Fi
• Maximum transmission distance: Up to 100 metres under optimal conditions
• Frequency hopping scheme: Adaptive frequency hopping
• Modulation: GFSK (Gaussian Frequency Shift Keying)
• Transmit power: Up to 10 mW
• Maximum packet size: 31 bytes in version 4.0/4.1, up to 251 bytes since version 4.2
• Range: 5 to 100 metres, depending on power level and advertising interval

BLE Profiles

BLE defines various profiles that determine the mode of operation. The most important profiles include:

• Heart Rate Profile (HRP): Real-time monitoring of heart rate.
• Blood Pressure Profile (BPP): Measurement and transmission of blood pressure data.
• Glucose Profile (GP): Monitoring of blood glucose levels.
• Proximity Profile (PXP): Utilisation of proximity information for key finders.
• Find Me Profile (FMP): Location of lost devices.

Additional profiles can be found in healthcare as well as in the sports and fitness sector (e.g., Cycling Speed, Running Speed, Weight Scale Profile). The Mesh Profile enables communication in mesh networks.

Alongside these specific profiles, two fundamental protocols are crucial for BLE communication: the Generic Access Profile (GAP) and the Generic Attribute Profile (GATT).

Generic Access Profile (GAP)

GAP deals with the processes before the actual data transmission, such as sending and receiving advertising packets, scanning for devices, and initiating and maintaining connections. GAP defines four main roles:

• Broadcaster: Sends advertising packets without the need for a connection.
• Observer: Receives advertising packets without the need for a connection.
• Peripheral: Sends advertising packets and accepts connections.
• Central: Initiates and manages connections to peripheral devices.

Additionally, GAP also describes the processes for establishing and maintaining connections:

• Advertising: Peripheral devices send advertising packets to signal their presence.
• Scanning: Central devices search for advertising packets.
• Initiating: Central devices establish connections with peripheral devices.
• Connecting: Two devices maintain an active BLE connection.

Advertisement & Advertisement Payload

Advertising packets are short messages sent by BLE devices to announce their presence. The advertisement payload can contain up to 31 bytes of data and includes information such as device name, service UUIDs, and other relevant data.

The structure of an advertising packet includes:

• Preamble: 1 byte for synchronisation.
• Access Address: 4 bytes, fixed at 0x8E89BED6 for advertising channels.
• PDU (Protocol Data Unit): Up to 37 bytes, containing the actual payload.
• CRC (Cyclic Redundancy Check): 3 bytes for error detection.

The key contents of the advertisement payload are:

• Local Name
• Manufacturer Data
• Service UUIDs
• Service Data
• Power Level
• Connection Interval Range
• Appearance (e.g., Icon)

Generic Attribute Profile (GATT)

GATT comes into play after the connection has been established and deals with structured data exchange. It defines how data is organised into services and characteristics and how they are exchanged.

• Service: A container for a group of characteristics, e.g., a heart rate monitoring service.
• Characteristic: A data value described by attributes such as properties (Read, Write, Notify) and descriptors.

A GATT server (e.g., a sensor) hosts the data, while a GATT client (e.g., a smartphone) retrieves and controls it. Communication occurs through standardised operations such as Read, Write, Notify, and Indicate.

Application Areas:

• Smart Homes: Control of household devices such as lighting systems and thermostats.
• Wearables: Fitness trackers and health monitors that continuously collect and transmit data.
• Industry 4.0: Real-time monitoring and maintenance of machinery to increase efficiency and reduce downtime.

BLE in IoT

The introduction of cost-effective and powerful System-on-Chip (SoC) solutions with integrated Wi-Fi and Bluetooth has revolutionised the IoT. Thanks to numerous development frameworks and miniaturised sensors, sophisticated applications in the industrial sector are now possible, ranging from environmental monitoring to image analysis.

However, certain technical requirements must be met in order to successfully deploy IoT devices in industrial environments. Robust enclosures and reliable cable connections protect the devices from extreme temperatures, high humidity, and vibrations. Modularity and integrated diagnostic tools also facilitate maintenance and repair.

A critical factor in this context is power supply. While modern sensors operate very energy-efficiently, data communication can still cause significant energy consumption. Depending on the location and specific requirements, batteries, solar cells, or power supplies can be used. The low energy consumption of BLE is particularly advantageous in scenarios with battery-powered devices. Efficient energy usage allows devices to operate longer without the need for frequent battery replacements.

In IoT environments, despite modern Wi-Fi technologies, maintaining stable data transmission remains one of the biggest challenges. Here, BLE can offer significant advantages. While Wi-Fi supports higher data transfer rates, most IoT applications do not require high data rates. BLE provides sufficient bandwidth for most sensor and control applications. Additionally, BLE uses adaptive frequency hopping techniques to minimise interference with other wireless technologies. This is particularly useful in environments with many devices and potential sources of interference, as BLE can often ensure more stable communication in such scenarios.

The technology not only offers an energy-efficient and reliable communication option but also provides solutions to many typical challenges in such environments. By integrating BLE into IoT systems, companies can increase their efficiency and develop cost-effective solutions.

Conclusion

The different BLE profiles enable a wide range of use cases, from health monitoring to smart homes and industrial automation solutions. By combining GAP and GATT, BLE can meet both simple and complex communication requirements.

In industrial scenarios where environmental conditions are harsh and the requirements are high, BLE demonstrates its strength. It reduces interference, enables stable communication, and contributes to energy efficiency. Additionally, BLE offers reliable data transmission and easy integration into existing systems.

While BLE is not the only technology in the IoT space, it offers specific advantages that make it particularly suitable for certain applications. Companies that integrate BLE into their IoT strategies can benefit from these advantages, such as low energy consumption and easy implementation. However, the specific requirements and conditions of each application should be carefully considered to make the best technology choice.