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Wireless Communications and Mobile Computing
Volume 2018, Article ID 4079017, 17 pages
Research Article

Energy-Efficient Uplink Resource Units Scheduling for Ultra-Reliable Communications in NB-IoT Networks

1Department of Computer Science and Information Engineering, Chang Gung University, Kweishan, Taoyuan 33378, Taiwan
2Department of General Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan
3Department of Computer Science, National Chiao Tung University, HsinChu 30010, Taiwan
4Department of Electrical Engineering, National University of Tainan, Tainan, Taiwan
5Research Center for Information Technology Innovation, Academia Sinica, Taipei 11574, Taiwan

Correspondence should be addressed to Jen-Jee Chen; wt.ude.ntun.liam@nehcjj

Received 1 March 2018; Revised 2 May 2018; Accepted 6 May 2018; Published 2 July 2018

Academic Editor: Shao-Yu Lien

Copyright © 2018 Jia-Ming Liang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


For 5G wireless communications, the 3GPP Narrowband Internet of Things (NB-IoT) is one of the most promising technologies, which provides multiple types of resource unit (RU) with a special repetition mechanism to improve the scheduling flexibility and enhance the coverage and transmission reliability. Besides, NB-IoT supports different operation modes to reuse the spectrum of LTE and GSM, which can make use of bandwidth more efficiently. The IoT application grows rapidly; however, those massive IoT devices need to operate for a very long time. Thus, the energy consumption becomes a critical issue. Therefore, NB-IoT provides discontinuous reception operation to save devices’ energy. But, how to further reduce the transmission energy while ensuring the required ultra-reliability is still an open issue. In this paper, we study how to guarantee the reliable communication and satisfy the quality of service (QoS) while minimizing the energy consumption for IoT devices. We first model the problem as an optimization problem and prove it to be NP-complete. Then, we propose an energy-efficient, ultra-reliable, and low-complexity scheme, which consists of two phases. The first phase tries to optimize the default transmit configurations of devices which incur the lowest energy consumption and satisfy the QoS requirement. The second phase leverages a weighting strategy to balance the emergency and inflexibility for determining the scheduling order to ensure the delay constraint while maintaining energy efficiency. Extensive simulation results show that our scheme can serve more devices with guaranteed QoS while saving their energy effectively.