Bluetooth Low Energy or Bluetooth Smart is a comparatively new wireless communication technology that was introduced by the Bluetooth Special Interest Group in 2010. Although the technology itself was being developed way earlier by Nokia around 2001 to 2006 under the name Wibree, it was not until 2007 that an agreement was reached with the various members of Bluetooth SIG that Wibree should now be included in the Core Bluetooth Specification, a task which was completed in 2010, when Wibree became a part of Bluetooth Core Specification version 4.0 as Bluetooth Smart, commonly known as Bluetooth Low Energy (its original name). The first mobile device to incorporate the 4.0 specification was iPhone 4S. However, as it is almost always with early adopters, the then iPhone 4S operating system did have some bugs regarding Bluetooth connectivity and range sometimes being poor. Bluetooth Smart technology has matured rapidly since then and come a long way. In fact, the dawn of the current IoT revolution is relying significantly on Bluetooth Low Energy for its success. According to an analysis done by IndustryArc.

Bluetooth Low Energy device shipments are forecast to increase to 8.4 billion units by 2020 at a mean annual growth rate of 29% which eventually will also lead to a surge in the number of IoT devices (things, if spoken semantically). We are seeing the early stages of this revolution all around us as a result of which, almost every handheld device and wearable nowadays has BLE capabilities.

So, what is it that makes Bluetooth Low Energy so special? How is Bluetooth Low Energy different from the good old regular Bluetooth? Why is every other wearable device (for example, Fitbit, Nike Fuelband, Apple watch and maybe your own smartphone) on the market using Bluetooth Low Energy (Couldn't they just do away with regular bluetooth and be happy about it)? We will explore the answer to all these questions and many others in this chapter. Furthermore, we will also discuss the architecture and what lies under the hood that makes Bluetooth Low Energy live up to its name.