Bluetooth® low energy represents a new communication standard aimed at achieving low power consumption, specifically for sensor data communication, actuator control, and other uses requiring relatively low data rates. As in the case of traditional Bluetooth®, Bluetooth® low energy specifications have been under development by member companies of the Bluetooth SIG. The core specifications were officially published in June 2010. At present, profiles are being formulated for individual applications.
Three major reasons explain the low power consumption in Bluetooth® low energy technology.
First, the wireless circuit itself requires low power consumption. Like classic Bluetooth® technology, Bluetooth® low energy employs GFSK for primary modulation and frequency hopping (rapidly switching between multiple channels) for secondary modulation. However, a more relaxed modulation index, greater channel width, and a simpler hopping pattern make the low energy version more suitable for low-power applications.
Second, Bluetooth® low energy technology employs intermittent communication. For the majority of communication time, power to the wireless circuit is switched off to save power. This sleep mode significantly reduces mean power consumed for communication.
Third, the connection/disconnection process is implemented rapidly. This is because an extremely simple protocol is used and because a special search channel is dedicated to performing this process. In most devices based on traditional Bluetooth® technology, it takes a few 100ms to complete disconnection. By contrast, Bluetooth® low energy technology can carry out the process of connection, data transfer, and disconnection as rapidly as 3ms. Most applications that transfer sensor data, such as temperature and humidity measurements, simply establish a wireless connection, transfer data, and then quickly cut the connection. The rapid connection/disconnection is therefore a great advantage here.
Combining these three benefits, Bluetooth® low energy technology reduces the power consumption of classic Bluetooth® technology to 1/10 or even 1/20.