Grouping-Based Discontinuous Reception for Massive Narrowband Internet of Things Systems

Narrowband Internet of Things (NB-IoT) is a novel narrowband radio technology particularly designed for low power, low data rate, enhanced coverage, and long battery life. To save power, the discontinuous reception (DRX) mechanism is standardized by third generation partnership project and also is adopted in the NB-IoT specifications as important methods to obtain long battery life. However, current DRX schemes used in the Long Term Evolution (LTE) are inadequate to the large-scale NB-IoT system. In this paper, aim to obtain better power saving and balance weak-up latency performance as well as avoid the possible signaling storm in an NB-IoT system with massive devices, a grouping-based energy efficient DRX strategy is proposed. Moreover, different DRX schemes are devised for the group leader and group members to further reduce power consumption. A discrete time semi-Markov process is applied to numerically analyze the system performance and to obtain the power saving factor and weak-up latency. Simulations show the fact that how the various DRX parameters impact the system performance. Specifically, simulation results demonstrate our proposed DRX mechanism outperforms the LTE DRX scheme in terms of power-saving performance although at the slight and sustainable cost of latency.