Since the topics of building automation and telemedicine are constantly gaining in importance, various standardization committees have optimized their communication concepts for the transmission of control data, switching commands, sensor values and meter readings and have developed corresponding radio specifications. Examples of this include the wireless variants of the Konnex bus, meter bus, ZigBee and Bluetooth.
The Bluetooth Special Interest Group( BSIG) has standardized an energy-efficient concept, Bluetooth Low Energy (BLE), for the transmission of sensor values and control data. Sensor values can include patient monitoring in telemedicine, such as ECG values sampled with a smart patch, as well as data from smart wearables or sensor data in production technology.
Bluetooth Low Energy is part of Bluetooth 4.0, which is also known as Bluetooth Smart and Bluetooth Smart Ready. Bluetooth 4.0 operates in the 2.4 GHz band with 40 channels between 2.402 GHz and 2.483 GHz, of which three channels 0, 12 and 39 are reserved as signaling channels. The channel width is 1 MHz. In this Bluetooth standard, the BSIG has specified the Bluetooth mesh, a mesh network with which the expansion range is extended.
As a modulation method, BLE uses Gaussian Frequency Shift Keying( GFSK) and Adaptive Frequency Hopping( AFH), which transmits at 1,600 frequency hops per second between predetermined frequency channels. The method is latency-free, so it has no latency. The effectively used bandwidth is 1 MHz, and the data rate is 1 Mbit/s. The bridgeable distance is about 10 m. During transmission mode, the transmitter requires a maximum of 10 mA. The duty cycle between transmission mode and idle mode is 0.25%. This means that the averaged current consumption is in the micro- ampere range. Data security is ensured by 128-bit Advanced Encryption Standard( AES) encryption and Diffie-Hellman key generation.