# Prediction-Based Energy Saving Mechanism in 3 GPP NB-IoT Networks
## 1 Introduction  
Internet of things (IoT) is being applied in various fields, from small sensors to industrial control systems, by supporting the interconnection between devices, and it aims to improve the quality of life [1]. Recently, new challenges are emerging for machine-type communication (MTC), such as public safety and problems in the field of smart grids. In addition, it is predicted that the IoT market will rapidly grow above ten times that of cellular communications [2]. Furthermore, 5G technology, expected to be commercially available by 2020, includes the development of two IoT-specific features, namely, massive IoT, suitable for high-density networks, and mission-critical IoT, aimed to delay-sensitive services [3]. To support various services, IoT networks will coexist with different technologies according to the type of service, rather than being unified by a single solution. The connectivity technology for IoT services is classified into two categories according to the coverage distance: short-range technology, for applications including smart home and smart health, and long-range technology, for applications including tracking and monitoring for connected cars and smart watches. Short-range connectivity relies on technologies such as wireless local area network (WLAN), Bluetooth, and ZigBee, and the resulting network connects devices based on multiple technologies and forms an infrastructure with a gateway to connect to external networks. In this architecture, however, network maintenance, operation cost, and network complexity rise exponentially as the number of devices grows. In contrast, long-range connectivity relies on cellular network technologies such as global system for mobile communications (GSM), widebandcode-division multiple access (WCDMA), long-term evolution (LTE), and LTE-MTC that cover several kilometers and support both device mobility without connection loss and high-speed transmission. However, these technologies present drawbacks including protocol overhead, reduced battery life, and high cost. Some connectivity solutions currently require low-frequency operation and tolerate some amount of delay, but also demand to continuously operate for several years in a wide area [4; 5]. However, the conventional connectivity technology cannot suitably satisfy these requirements. Given that the cellular network is optimized for voice, multimedia, and high-speed services, it is difficult to achieve low cost and low energy consumption for IoT modules. Likewise, the requirement of a gateway to provide connection with external networks in short-range connectivity technologies causes similar problems to those when using a wired or cellular network. To solve these problems, the low-power wide area network (LPWAN) technology was introduced. This technology extends the coverage area to several kilometers and improves the device cost and energy consumption by reducing the modern complexity. Figure 1 illustrates the LPWAN technology and IoT services according to coverage and throughput. A LPWAN is designed with the following requirements: communication distance up to 40 km, thousands of devices supported by one base station, availability for over 10 years without battery replacement, and module price below US$5. Examples of LPWAN technologies that use the unlicensed industrial, scientific, and medical bands include SIGFOX and long range (LoRa), whereas the narrowband IoT (NB-IoT), recently introduced by the 3 rd Generation Partnership Project (3 GPP), uses the licensed bands [6]. The NB-IoT introduced the evolved packet system (EPS) optimization that reduces the protocol overhead of state transition to achieve low energy consumption in addition to reduce the modern complexity. In existing LTE networks, the control signals and application data are transmitted separately via the control and user planes, respectively, and a radio bearer setup is necessary to send application data.