Bluetooth communication takes place a short range ad hoc network known as Piconet. A Piconet starts with two connected devices and can grow up to eight connected devices. In general, the Bluetooth communication sets one of the Bluetooth devices as a controlling unit (master unit) and other device as a slave unit to follow the master. Each device added to the Piconet will be assigned with a specific time period to transmit the data without colliding or overlapping with the other units. Bluetooth core specification supports connection of two or more Piconets to form a scatternet by which a device of one Piconet either operating as a master or slave can simultaneously play a slave role in the other. Hence communication between more than 8 devices is made possible.

Bluetooth Classification
Number of Bluetooth versions is developed to meet the specific requirements of the time with the update of fixing the previous version errors. All the updated versions of Bluetooth support backward compatibility.

Bluetooth Classic has faced critical challenges such as fast battery draining and frequent loss of connection which requires frequent pairing. BLE has ability to overcome these challenges and this is the reason why it has become popular in this decade. BLE is more intelligent in managing connections while preserving the battery power. BLE rather maintaining constant bit streams of information sends small chunks of data when required and goes to sleep during the idle periods. Bluetooth/BLE Low Energy comes under the Personal Area Network (PAN) type of connectivity.

Bluetooth classic and Bluetooth Low Energy devices. Since smart phones have become the norm, most of the IoT device developments especially in healthcare, home automation segments take place centered around BLE connectivity. IoT devices that supports BLE connectivity tends to be a Bluetooth Smart device that can connect only with the Smart ready devices. Bluetooth smart devices such as smart watches, car key fobs, heart rate monitor are stand-alone, small batter operated that mainly focus on the power consumption as low as possible. With the understanding of the Bluetooth technology and its classifications, we will discuss in detail about the design considerations for developing IoT devices with Bluetooth Low Energy connectivity.