Bluetooth version 4.0 introduced Bluetooth with low energy functionality, sometimes referred to as Bluetooth Smart, which gave developers the ability to create sensors that can run on coin- cell batteries for months and even years at a time. Some of these sensors are so efficient that the kinetic energy from just flipping a switch can provide operating power. 

Bluetooth low energy technology is inherently different from BR/EDR. BR/EDR establishes a relatively short-range, continuous wireless connection, which makes it ideal for uses such as streaming audio from a smartphone to a headset.Bluetooth low energy technology allows for short bursts of long range radio connections, making it ideal for IoT applications that depend on long battery life. 

In this paper:

• We explore the fundamentals of the Bluetooth 4.0 specification.
• Discuss the 4.0 architecture, including link layers and security.
• Explain how device discovery and connections work.