Optimized cooperative data transmission in two-tier NB-IoT networks

Narrowband Internet of Things (NB-IoT) networks are growing rapidly due to their low energy consumption and strong signal penetration. However, the technology faces key challenges, including high latency and low data rates. This article presents a cooperative solution aimed at boosting network throughput through a two-tier network architecture. These networks typically integrate cellular communication with Device-to-Device (D2D) interactions, using NB-IoT for cellular communication and Bluetooth Low Energy (BLE) for D2D connectivity. Idle nodes support the target node by assisting in data downloads or uploads. The group formation process is designed to achieve three main objectives: maximizing throughput, minimizing energy consumption, and preserving the total battery life of the group nodes connected to the base station. To optimize these multi-objective goals, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is applied. The algorithm produces candidate groups, and one is selected by adjusting node participation rates. Simulations show a 7.7-fold increase in throughput with only an 8% rise in energy consumption for downloads, and a 7.6-fold improvement with just a 2% energy increase for uploads, compared to the base case.