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The rapid proliferation of Internet of Things (IoT) devices and applications has resulted in an increasing demand for Low Power and Wide Area Network (LPWAN) solutions. The adoption of IoT networks still faces several challenges, despite the rapid advancement of low-power communication technology. Homogenizing this sector requires allowing interoperability between many technologies, which is now one of the largest obstacles. In this article, we present the design and implementation of the hybrid LPWAN architecture that can accomplish wide-area communication coverage and low-power consumption for IoT applications by leveraging two LPWAN technologies, Wireless Smart Ubiquitous Network (Wi-SUN) and Long Range (LoRa). In particular, LoRa is used for long-range communication, and Wi-SUN for a low-latency mesh network. Additionally, we implemented smart street light controlling system as a real-world deployment at the university campus to showcase the efficiency of the hybrid network. Our results demonstrate that the hybrid LPWAN architecture provides a better coverage and capacity while consuming less power than that of the LoRa or Wi-SUN network. The results of this study demonstrate the effectiveness of the proposed hybrid LPWAN architecture as a viable solution for next-generation IoT applications. [ABSTRACT FROM AUTHOR]

Next-generation Internet of Things (IoT) systems require faster data transmission, support for moving objects, and long-distance transmission when compared to the currently available IoT systems. The IEEE 802.15.4 smart utility network (SUN) orthogonal frequency-division multiplexing (OFDM) can satisfy these requirements. Mobile-communication-oriented receiver systems are typically used in urban environments for SUN OFDM. However, the evaluation depends on computer simulations and requires an experimental evaluation platform based on software-defined radio (SDR) that can modify transmitter-receiver functions. We present a platform for SUN OFDM that enables high-speed mobile communication. The proposed platform comprises a signal generator-based transmitter and an SDR-based receiver; the receiver baseband signal processing is performed by MATLAB. We also proposed signal processing functions that can receive the SUN OFDM packets even at speeds of tens of km/h. We applied a simplified universal time-domain windowed (UTW)-OFDM scheme to this platform to operate even at sub-1 GHz, where the spectrum mask is more limited. In the experimental evaluation, the required packet error rate for SUN OFDM was achieved in an 80 km/h multipath fading environment, and out-of-band emission can be suppressed by over 43 dB from the peak power while achieving performance equivalent to that without applying the simplified UTW.

IEEE 802.15.4 smart utility network (SUN) frequency-shift keying (FSK) has attracted considerable attention as a wireless communication standard designed for use in essential applications required by Internet of Things (IoT) systems. However, longer transmission distances in highly mobile environments are required to support various applications in next-generation IoT systems, such as vehicle-to-everything, automated driving, and drone control systems. Although research on wide-area, highly mobile communications has been conducted via computer simulations, an experimental evaluation platform for further research has not been developed. In this study, we developed an experimental evaluation platform for SUN FSK in very high frequency bands. The developed platform comprises a signal generator-based transmitter and a software-defined radio-based receiver. It was proven to be capable of transmitting a power of ≥5 W through a power amplifier and was suitable for laboratory and field experiments. In addition, we developed received signal processing methods, including a packet detection method and a channel estimation method, which were designed to achieve wide-area, highly mobile communication. In laboratory experiments, the packet error rate characteristics required by IEEE 802.15.4 were achieved even at a transmission distance of >10 km at vehicular speeds of several tens of km/h.

This study proposes a heterogeneous in-band full-duplex system for the simultaneous transmission of the existing wireless smart ubiquitous network (Wi-SUN) using IEEE 802.15.4g-compliant frequency-shift keying for smart utility network (SUN-FSK) and reception of the next-generation Wi-SUN using IEEE 802.15.4-2020-compliant orthogonal frequency-division multiplexing for SUN (SUN-OFDM). In particular, we propose a digital self-interference (SI) cancellation scheme based on high-precision SI channel estimation using the moving average method, which can be used when the SI signal is a SUN-FSK signal and the desired signal is a SUN-OFDM signal. Furthermore, we propose a highly efficient SUN-OFDM demodulation technique that considers the effect of residual SI. We evaluate the proposed methods through computer simulations. The proposed methods can achieve 67 dB of SI cancellation in the digital domain when the SI signal power and desired signal power ratio in the digital domain is 50 dB. The results of this study enable more efficient coexistence of the existing and next-generation Wi-SUNs, which is expected to improve the throughput and responsiveness of next-generation Wi-SUN systems employing SUN-OFDM.

To actively develop and promote Internet of Things related techniques, we propose a dynamic and non-centric networking approach using virtual gateway platforms, and evaluate it based on low-power wide-area networks that adopt the traditional star and mesh topologies. In our approach, for each local device, we first present a device management method in which two working modes are set to indicate whether the device works as a virtual gateway (VGW) or provides relay services. Then an internal parameter is defined to manage the mode by considering the device's current states, such as battery power remaining, presence or absence of an external power supply, etc. We thereafter propose a mode switching method where two time-varying threshold values are configured and help a local device to switch between the two modes through the use of an internal parameter. Finally, a path determination algorithm is applied to find routes for data transmission with or without devices playing the role of VGWs. Computer simulation results indicate that the proposed networking approach can take advantage of both traditional star and mesh systems, enables dynamic and non-centric changes in network configurations, and finally ensures that in most cases, the transmission performance is equivalent to or better than that of other network setups.

In the era of the 4th industrial revolution, power automation with Smart Grid is becoming increasingly important. The reliability of the power automation system that controls and monitors the power systems has become a major performance indicator. To achieve optimum performance, it is essential to ensure the reliability of the communication network connecting each remote device as well as the main systems. Short range communication methods, such as DWB, using ISM band frequency(5 GHz) have been developed and used for the power automation system in areas without an optical communication network. However, difficulties are encountered during the operation of power automation systems due to lack of reliability. In order to resolve these problems, we developed the advanced wireless bridge(AWB) that implemented frequency diversity with 2.5 GHz(Zigbee) and 900 MHz(Wi-SUN). The AWB improved the communication success rate to 20 % compared to the original DWB method. [ABSTRACT FROM AUTHOR]

Natural disaster is one of the most important research topics worldwide. In this paper, a data driven cyber-physical system is introduced to detect landslides. This system is composed of Wi-Sun acceleration sensors, which can detect the acceleration of the nearby environment in 3D domain, and the sensors are linked with the router (act as 'sink' node) via Wi-Sun transmission (i.e. IEEE802.15.4g). The details of the detection system are explained and the landslide detection mechanism with low computational complexity is proposed. A traffic reduction method is proposed thereafter to help reduce the data needed for transmission by exploring the intra-correlations of the sensor data. This method can save the energy consumption without degrading the detection performance. Field test is conducted and the results show that the landslide can be detected and amount of data to be transmitted can be reduced, which verifies the system's effectiveness. [ABSTRACT FROM AUTHOR]

Smart meters are needed for realizing energy savings and automatic meter reading. As smart meters used for the gas or water supply infrastructure cannot always receive supplied power, a low-power-consumption communication protocol for battery-powered smart meters is required. The U-Bus Air protocol is standardized for gas meters in mid- and high-rise buildings. U-Bus Air has the features of low power consumption using time asynchronous communication and multi-hop communication among nodes. However, the interference power increases as the number of nodes increases. In order to solve the problem, intermittent receiver-driven data transmission media access control (IRDT-MAC) was proposed; it finds the appropriate transmission cycle (intermittent interval); the communication performance is improved using the derivation of the collision probability. On the other hand, IRDT-MAC cannot correspond to a change of link topology. In this paper, we propose a protocol for controlling the receiver beacon transmission interval using the fusion center (FC) for solving the above problem. In this protocol, the link topology of each smart meter is sent to the FC and the FC calculates the suitable transmission cycle for this specific topology. Finally, the suitable transmission cycle is fed back to each node from the FC. Using computer simulations, improvements of the packet delivery ratio (PDR), the throughput, and the power consumption are confirmed in two topologies. Specifically, the improvements are confirmed in the case of two stages or more in the building-wide square topology. [ABSTRACT FROM AUTHOR]

We have tried to develop the guidance system for farmers to cultivate using various phenological indices. As the sensing part of this system, we deployed a newWireless Sensor Network (WSN). This system uses the 920 MHz radio wave based on the Wireless Smart Utility Network that enables long-range wireless communication. In addition, the data acquired by the WSN were standardized for the advanced web service interoperability. By using these standardized data, we can create a web service that offers various kinds of phenological indices as secondary information to the farmers in the field. We have also established the field management system using thermal image, fluorescent and X-ray fluorescent methods, which enable the nondestructive, chemical-free, simple, and rapid measurement of fruits or trees. We can get the information about the transpiration of plants through a thermal image. The fluorescence sensor gives us information, such as nitrate balance index (NBI), that shows the nitrate balance inside the leaf, chlorophyll content, flavonol content and anthocyanin content. These methods allow one to quickly check the health of trees and find ways to improve the tree vigor of weak ones. Furthermore, the fluorescent x-ray sensor has the possibility to quantify the loss of minerals necessary for fruit growth. [ABSTRACT FROM AUTHOR]