In the world of lighting, Bluetooth 5 represents a technology that defines an application standard for IoT Lighting, allowing interoperability between luminaires, sensors and control devices. In fact, this application standard is the only one available on the wireless lighting market with the Zigbee standard.
Bluetooth technology is a standard for the exchange of wireless data on short distance using the UHF shortwave radio band. Designed to replace RS-232 data cables, Bluetooth saw the light (although not with this name) as early as 1994, when the Swedish Ericsson introduced a technological standard similar to the current Bluetooth on the market. A few years later Ericsson, Nokia, Intel and Toshiba (among others) give life to the Bluetooth Special Interest Group (SIG – https://www.bluetooth.com/), which aims to keep the standard updated and develop new specifications and features. Today the SIG has over 30,000 members with companies operating in the telecommunications, consumer electronics, information technology and network infrastructure sectors. Bluetooth uses radio waves with frequency from 2.4 GHz to 2.485 GHz and requires an overall low consumption of electricity. Each device equipped with a Bluetooth chip is able to create a network of limited size (depending on the version used, the range can vary from a minimum of 10 meters to a maximum of 30 meters), called Personal Area Network (PAN) and extremely secure. Usually, the connection and data exchange inside a single PAN takes place between two devices, but the standard provides that each Bluetooth device can connect with up to 7 other devices. The Bluetooth network (or piconet) uses packet-switched protocols and is characterized by a master/slave architecture (similar to the server/client one on which the Internet is based). The data exchange takes place at predetermined time intervals and timed by the master (ie by the device that creates the Bluetooth network): each interval lasts 312.5 microseconds, during which the devices can send their data packets. The master sends data in odd intervals and receives data in even intervals; slaves receive in odd intervals and send in even intervals. Like all new standards, the first Bluetooth was version 1.0, soon followed by 1.0B. Both did not excel in safety: it was impossible to connect two devices while maintaining anonymity. Even the interoperability and universality of the connection (which in theory were the reason itself for the birth of Bluetooth) were not always guaranteed. Most of these problems have been solved with Bluetooth 1.1 and, above all, with Bluetooth 1.2. This latest version also introduces new funtionalities such as Adaptive Frequency Hopping (AFH), to reduce electromagnetic interference and extended Synchronous Connections (eSCO), which allows the transmission of high quality audio.
With Bluetooth 2.0 the performances of the connection also begin to rise, thanks to the Enhanced Data Rate (EDR) technology that brings the maximum speed to 3 Mbit per second. Service quality control is also introduced and energy consumption is considerably optimized. Energy saving improves again with Bluetooth 2.1, which also facilitates the pairing procedures of devices and makes them safer.
Bluetooth 3.0 is the version of the standard that inaugurates the era of high-performance Bluetooth connections: thanks to the use of IEEE 802.11 Wi-Fi frequencies, the maximum speed rises to 24 Mbit/s and this standard begins to become more interesting for a wider range of uses. Also because it becomes even safer, thanks to Aomic Encryption Change: the password of encrypted connections is being continuously changed, to limit the risk of intrusion.
With Bluetooth 4.0, the Low Energy (LE) standard is introduced, i.e. a Bluetooth version specifically dedicated to devices such as sensors that require little data bandwidth but must consume as little as possible. The speed of the BLE in fact drops to just 1 Mbit / s, but consumption is significantly lower.
Starting from Bluetooth 4.0, then, the range of radio bands that can be used to transmit data at high speed is further expanded, but this creates some interference problems with some networks. Problems then solved with Bluetooth 4.1 and 4.2.
The latest Bluetooth generation is the fifth, which offers significant improvements compared to the past: the transmission area is four times larger, the speed in LE mode doubles, that in standard consumption mode even multiplies by eight. Bluetooth 5.1 and 5.2 are nowadays the fastest, most stable and secure versions of this connection standard among electronic devices.
If today with Bluetooth it is possible to connect to each other the most disparate devices at a very low price, it is because, with the standard progress, numerous “profiles” have been introduced. This term means sets of instructions, which refer to the main standard but are specific for a certain type of use. A Bluetooth speaker, for example, needs that part of Bluetooth protocol that concerns audio transmission, but doesn’t need that which is used to manage a video stream. A Bluetooth mouse, on the other hand, needs neither the first set of instructions nor the second, but requires a third set, that is, another Bluetooth profile.
Today there are 27 officially approved Bluetooth profiles, but only six are mostly used: Advanced Audio Distribution Profile (used to transfer audio in high quality), Audio/ Video Remote Control Profile (AVRCP, used to transfer audio/video streams), Handsfree Profile (HFP, used in car infotainment systems), Headset Profile (used on headsets to receive and make phone calls), File Transfer Protocol (FTP, used to transfer files between multiple devices), Human Interface Device Protocol (used for mouse, keyboards and other input devices).
Bluetooth Mesh
In early 2019 Bluetooth SIG released specifications for Bluetooth Mesh (https://www.bluetooth.com/specifications/mesh-specifications/), a network structure for LE Bluetooth devices considered a more reliable and scalable solution for IoT applications and home automation devices that require a low power network technology to interact and exchange information with each other. This technology will be a crucial ingredient for IoT applications, such as beaconing, industrial automation and smart home devices.
Following concepts have been defined:
- Mesh Profile: defines the basic requirements to enable an interoperable mesh network solution for Bluetooth LE wireless technology.
- Mesh Model: presents models, used to define the basic nodes functionality on a mesh network.
- Mesh Device Properties: defines the device properties required for specifying the mesh model.
As anticipated at the beginning of the article, for the world of lighting this technology represents a turning point because it defines an application standard for the IoT Lighting field, allowing interoperability between lighting fixtures, sensors and command devices. In fact, this application standard is, together with Zigbee, the only one available on the wireless lighting market.