Low-Power BLE Relay Node Operation in Mesh-Like Architectures for Precision Agriculture

In this article, we propose a Bluetooth Low Energy (BLE)-based precision agriculture framework, which replaces cluster heads with battery-operated relay nodes that relieve the sensor nodes of any extra workload apart from the transmission of their own data and also help in range extension. The framework imitates BLE mesh and uses BLE advertisements. Since BLE advertisements provide no inherent synchronization between transmitter and receiver, we propose a novel low-power operation for the BLE-based relay node in which it learns the schedule of the incoming data packets and wakes up to scan at certain instants of time when packet reception is expected. This helps the relay node to keep scanning disabled and stay in sleep mode for most of its lifetime. Consequently, the battery lifetime gets prolonged since the average current consumption of the scanning operation is just 6 mA, and the sleep current is very small, close to $7.3~\mu $ A. We provide a power consumption analysis to show the effectiveness of the proposed mechanism in extending the lifetime of the relay node. Furthermore, we found through real-time experimentation carried out continuously for seven days that with the proposed operation, the relay node is able to achieve an average of 96% and a maximum of 100% successful reception.