For the last decade, Classic Bluetooth technology has successfully reduced the usage of wires in headsets, computer mice, keyboards as well as industrial and medical Serial and Ethernet cables. Now on its way to the marketplace is a new and smaller footprint Bluetooth technology which is aimed for smart phone accessories, internet connected devices and small devices used in the industrial and medical industries. This new technology goes by the name of Bluetooth low energy technology.
Will Bluetooth low energy technology be just another wireless technology? In many aspects, the answer is “yes.” However, the unique combination of ultra-low power, several new features and the fact that Bluetooth low energy technology will be integrated in most handheld devices, makes the technology especially well-suited for a number of new and powerful applications. Both Microsoft and Apple have announced that Bluetooth low energy technology will be integrated in the next versions of their operating systems.
The Bluetooth SIG forecasts that Bluetooth low energy technology will be implemented in billions of products within just a few years:
- Phone Accessories > 10 billions
- Smart Energy (counters and displays) ~ 1 billions
- Home Automation > 5 billions
- Health, Wellness, Sports & Fitness > 10 billions
- Assisted Living > 5 billions
- Animal Tagging ~ billions
- P2P Intelligent Transport Systems > 1 billion
- Industrial Automation/M2M > 10 billions
The high volumes and the integration in smart phones, PADs and laptops secure attractive pricing and a long-term availability of chipsets. Bluetooth Low Energy Technology Features
Bluetooth low energy technology is the hallmark feature of the Bluetooth Core Specification 4.0 (Bluetooth v4.0) and has inherited several technical features from Classic Bluetooth technology. Examples of inherited features include the Bluetooth radio with Adaptive Frequency Hopping (AFH) as well as the Logical Link Control and Adaptation Protocol (L2CAP) interface. This inheritance makes the technology very easy to set up, robust and reliable in tough environments.
However, in other areas, it is a totally new technology. For instance, the technology features very efficient discovery and connection set-up, short packages and asymmetric design for small devices. The Lowest Possible Power Consumption
Everything from physical design to user scenarios is designed to keep the power consumption at a minimum. In order to bring the power consumption to a minimum, a Bluetooth low energy device is kept in sleep mode the majority of the time. When an event occurs, the device wakes up and a short message is transferred to a gateway, PC or a smart phone. Maximum/peak power consumption is less than 15 mA and the average power consumption is about 1 μA. In other words, the power consumption is reduced to a tenth of the energy consumption of Classic Bluetooth. Therefore, a button cell battery CR2032 could last for 5 – 10 years of operation. Cost Efficient and Backwards Compatible
In order to offer backwards compatibility to Classic Bluetooth and, at the same time, offer cost efficiency for small battery-operated devices, there are the following two chipset types:
- Dual-mode technology including both Bluetooth low energy and Classic Bluetooth functionality.
- Stand-alone Bluetooth low energy technology optimized for small battery-operated devices with low cost and low power consumption in focus.
Figure 1: Bluetooth low energy chipsets are available in two versions. Robustness, Security and Reliability
Bluetooth low energy technology uses AFH technology, as does Classic Bluetooth technology, in order to achieve a robust transmission in tough environments, which is the case in industrial and medical applications. In order to minimize the cost and energy consumption, Bluetooth low energy technology has reduced the number of channels to 40 2 MHz-wide channels instead of the 79 1 MHz-wide channels in Classic Bluetooth technology.
Figure 2: Bluetooth low energy technology uses 40 channels instead of the Classic Bluetooth technology’s 79 channels. Wireless Co-existence
Several wireless technologies – Bluetooth technology, Wireless LAN, IEEE 802.15.4/ZigBee and various proprietary radios – use the license-free 2.4 GHz Industrial Scientific Medical (ISM) band. With so many technologies in the same radio space, it easily leads to an overcrowded radio environment decreasing the wireless performance due to the need for retransmissions. In demanding applications, disturbances are reduced through frequency planning and special antenna solutions. AFH not only makes the Bluetooth transmission robust and reliable, but it also considers the other wireless technologies’ transmissions.
Figure 3: Three advertising channels as well as nine data channels out of the 37 data channels are located in between the channels that are used by Wireless LAN. Connection Range
Bluetooth low energy technology has a slightly different modulation than Classic Bluetooth technology. This modulation differentiation offers a range of up to 300 meters with a 10 dBm radio chipset. Ease of Use and Integration
A Bluetooth low energy solution is typically based on a master connected to a number of slaves. A device is either a master or a slave, but never both. The master controls how often the slaves are allowed to communicate and the slave only communicates by request from the master.
A new Bluetooth low energy feature compared to Classic Bluetooth technology is the “advertising” functionality. A device (acting as a slave) can in this way announce that it has something to transmit to the master. An advertisement message can also include an event or a measurement value.
Figure 4: An advertiser periodically sends messages and will always be a slave once the connection is established. A scanner is ready to receive an advertisement message and a connection request and will always be a master once the connection is established. Software Structure
All parameters in Bluetooth low energy technology have a state that is accessed using the Attribute Protocol. All attributes are represented as characteristics that describe signal value, presentation format, client configuration, etc. A battery, for example, could have the following characteristics:
- Level: 0-100%
- State: NOT_USED, CHARGING, RECHARGE_COMPLETE, DISCHARGING, CRITICAL_REPLACE_NOW, RECHARGE_NOW
In the Generic Attribute Profile (GATT) service groups, features and declarations are brought together. In the Generic Access Profile (GAP) connections, discoverable, connectable and bonding, etc. are described. Through these attributes, it is possible to build numerous basic services and profiles. Some examples of basic services and profiles include:
- Find Me
- Automation I/O
- Building Automation (Temperatures, Thermostat, Humidity)
- Lighting (On/Off Switch, Dimmer)
- Remote Controllers
- Fitness (Step Counter, Heart Beat Monitor)
- Medical Devices (Glucose Meters, Scale Instruments, etc.)
Based on the above described Bluetooth low energy features, the technology is well-suited for applications where transferring of signal status is instrumental.
Example 1: Remote controller based on a commercially available device at pump station in Norway operated with ABB products.
A portable HMI-unit based on an iPhone or Android smart phone is able to read/write variables from a device (PLC, lighting, heaters, etc.) and can replace the currently-used application’s unique remote control units for a variety of user applications. The newer smart phones offer additional opportunities that have previously not been possible; for example, Internet connection to spare part lists, user instructions, presentation and alarm lists, trend curves, etc.
Example 2: Remote controller based on an IO-unit.
Simple data exchange (IO-transfer) between two devices like a PLC and an IO-device/simple HMI-panel without artificial intelligence. The digital and analog signals are mirrored from one side to the other.
Example 3: Data acquisition
The Bluetooth low energy gateway reads the sensor values during a specific time interval or the slave devices transmit the sensors values upon events (such as specific temperatures and time intervals). The Bluetooth low energy node could include software for calculations and logic as well as store historical values.
Example 4: Device access.
A use case where a fast and secure connection is needed is where a mobile device (such as an iPhone, Android or Windows Mobile device) is used as a key to get access to a specific PC or machine. This functionality could also be used in combination with the proximity feature and is based on the Radio Signal Strength Indication (RSSI) value that monitors if the user is within close proximity of the actual machine or door. Since the RSSI value/distance to the device is configurable, access can be switched on depending on the distance to the device.
Example 5: Follow me.
Follow me is a reversed functionality of the proximity feature and could be used to alert people or machines when a device is moving too far away from the other device.
Example 6: Asset management.
Since device maintenance needs are increasing, the interest for device information is also growing. In a Bluetooth low energy node, it is possible to store information concerning device type, run-time, last inspection, and potential overload. This information can be accessed when an operator gets in close proximity of the device.
Bluetooth low energy technology is a powerful “app” enabler that will change the way we experience wireless applications. As the technology is being implemented in almost all smaller mobile devices, there is no longer a need to develop specific handheld operator devices and the additional data/knowledge exchange possibilities are unlimited.
Short facts about Bluetooth low energy technology:
- Cost efficient stand-alone solutions
- Multiple suppliers guarantee attractive pricing and long-term availability
- Robust and reliable technology also in tough environments and demanding applications
- Long range possibility
- Co-exists with other wireless technologies
- High local density
- Fast connections
- Low latency
- Simple star typology
- Ultra-low power consumption