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Technical Papers

This page provides a sample of representative technical papers documenting the foundations, testing, and uses of Wi-SUN related standards and technology.

2026

The wireless smart ubiquitous network (Wi-SUN), a wireless communication system based on the IEEE 802.15.4 smart utility network (SUN) standard, has evolved since its standardization as IEEE 802.15.4g in 2012 to enable low-speed, long-range, and low-power packet communication. With communication capabilities embedded in devices such as meters, sensors, and monitors, Wi-SUN has been deployed in tens of millions of devices worldwide as an Internet of things (IoT) communication system for information collection and device control. The physical layers standardized in the IEEE 802.15.4 SUN standard and used in Wi-SUN include frequency shift keying (FSK) and orthogonal frequency division multiplexing (OFDM), which are referred to as SUN-FSK and SUN-OFDM, respectively.

This paper summarizes the technical specifications, usage models, and recent research trends of SUN-FSK and SUN-OFDM and examines their transmission characteristics. In particular, for the transmission characteristic evaluation, we compiled reference data along with the results of outdoor transmission experiments, presenting these from both the computer simulation and hardware evaluation perspectives. Finally, as a future development of the IEEE 802.15.4 SUN standard, we demonstrate the potential for utilizing low-frequency bands, such as the very high-frequency VHF band, based on fundamental transmission characteristics.

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A wireless smart utility network field area network (Wi-SUN FAN) is an international standard for wireless communication systems designed for Internet of Things applications. This standard employs multihop routing, transferring data through other devices, which enables construction of wide-area mesh networks.

In addition, multiple protocols are followed in parallel to maintain high-quality multihop communications against various signal interferences in the frequency and time domains. However, many protocols adopted in a Wi-SUN FAN are independently standardized through different standardization conferences.

Furthermore, discussions regarding interactions between these protocols remain insufficient. Consequently, there is a scope for improving communication quality by adjusting each protocol to account for these interactions. This research focuses on multiple protocols used at the data link layer in a Wi-SUN FAN, identifying interactions that arise when they are combined and the resulting problems.

In addition, we propose a protocol coordination method for addressing these issues and improving communication quality metrics such as the communication success rate and communication delay. Through computer simulation and experimental verification, we confirm that the proposed method improves communication quality, increasing the communication success rate by 20% compared with the conventional method before parameter adjustments. Furthermore, we demonstrate that the average communication delay time is reduced by approximately 85% (from 5.98 to 0.93 s) by adjusting various parameters using the proposed method to enhance communication efficiency.

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The Wireless Smart Utility Network Field Area Network (Wi-SUN FAN) is an IPv6-based multi-hop wireless standard that achieves a high throughput of several hundred kilobits per second, approximately 10–100 times that of typical low-power wide-area technologies, while maintaining low power consumption. However, transmitting video over a Wi-SUN FAN is challenging as high-rate streams of numerous short real-time transport protocol (RTP) packets incur a considerable per-packet overhead, significantly reducing the efficiency.

This study proposes an application-layer multi-layer optimization framework for H.265/RTP transmission over standard Wi-SUN FAN protocols. The framework comprises three components: 1) selective exclusion of redundant network abstraction layer units at the source (access unit delimiters and selected video usability information) under conditions validated to have no perceptual impact; 2) near-maximum transmission unit-sized user datagram protocol (UDP) aggregation, which bundles multiple RTP payloads to reduce channel-access attempts; and 3) reliability-constrained rate planning, which maps the hop count and stream concurrency to a minimum emission interval and sustainable per-stream bit rate to satisfy a target end-to-end packet delivery ratio (PDR).

The framework was evaluated in a ladder network environment using large-scale computer simulations and a hardware testbed, targeting a video surveillance use case. Video quality was assessed using video multi-method assessment fusion (VMAF). Results show that handling multiple camera streams achieves a stable, practical-quality VMAF score of approximately 80 while reducing wireless UDP datagrams by up to 84.5%. A topology-indexed lookup table maps the hop count and stream concurrency to a safe emission rate, enabling 99.9% PDR in practical deployments.

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The wireless smart ubiquitous network (Wi-SUN) field area network (FAN), an emerging wireless multihop communication standard for Internet of Things systems, is used to develop smart cities, metering, and factory infrastructure. The Wi-SUN FAN adopts the Internet Protocol version 6 routing protocol for low-power and lossy networks and employs the exponentially weighted moving average method, which considers historical values of link metrics to configure robust multihop networks.

Because the deployment of mobile nodes is an indispensable aspect of the development of smart cities and smart factory infrastructure, the Wi-SUN FAN should be able to route mobile nodes. To this end, this study employ computer simulations and field experiments to evaluate the packet delivery ratio (PDR) of a mobile Wi-SUN FAN node operating under a conventional routing protocol, thereby revealing the causes of PDR degradation.

To overcome these limitations, we propose a routing protocol that considers the moving direction of the mobile node to ensure reliable mobile communication within the Wi-SUN FAN. Computer simulations show that the PDR improves by up to 87% (PDR points range from 0.125 to 0.995) under the proposed protocol compared to conventional routing protocols when the node moves at 10 m/s. In experiments using actual equipment, the PDR improves by up to 38% (PDR points range from 0.476 to 0.859) when the node moves at 0.26 m/s. The simulation and experimental results confirm that the proposed routing protocol overcomes the limitations of the conventional routing protocol through swift parent handover and selection, regardless of the direction of movement.

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The Wireless Smart Utility Network Field Area Network (Wi-SUN FAN) relies on IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) to construct large-scale multi-hop IP networks. However, local parent selection can concentrate traffic through a few relays, increase path depth, and amplify packet loss.

We propose a centralized route-construction framework that aggregates neighbor reports at the border router and applies zero-suppressed decision diagram (ZDD) to enumerate all Destination-Oriented Directed Acyclic Graph (DODAG)-consistent spanning structures under global constraints such as hop bounds and per-parent child limits.

From this feasible set, routes are chosen according to a network-wide objective and then minimized for total relay count. In a 75-router, 4 km × 4 km simulation with realistic Wi-SUN PHY/MAC and propagation settings, the selected routes improve end-to-end success rate and latency, achieving approximately 90% end-to-end packet delivery ratio (PDR) at low offered load. By optimizing globally before installation, our approach produces shallow DODAGs that reduce hop counts while balancing relay load, resulting in a substantial improvement in communication reliability.

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2025

Wireless Smart Utility Network Field Area Network (Wi-SUN FAN) is a profile of Wi-SUN, a wireless communication standard for Internet of Things (IoT) devices, designed for applications requiring large-scale, outdoor, mesh-based communication networks such as smart metering systems. Wi-SUN FAN adopts the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) as its network-layer routing protocol. RPL is primarily designed for communication among fixed nodes, which poses challenges for constructing optimal communication routes in mobile communication environments.

To address this issue, research has been conducted to improve the routing method for realizing mobile communications based on Wi-SUN FAN. However, the previous study has the disadvantage of requiring adjustments to time constraint parameters related to route construction when nodes move, and is unable to accommodate speeds above a certain level. In this paper, we propose a routing method that solves this problem by optimizing the generation of control frames and eliminating time constraints on route updates for mobile communication system using Wi-SUN FAN that is independent of speed.

We compare and evaluate conventional method (i.e. RPL), modified method in the previous study, and proposed method for route control methods using computer simulations. The results show that the proposed method optimizes control frames and enables the construction of reliable communication routes even under high-speed mobility, and the transmission success rate when the mobile node moves at 19 m/s is improved by a factor of approximately 2.9 compared to the conventional method.

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Wireless Smart Utility Network (Wi-SUN) is a wireless communication standard for the Internet of Things (IoT) to achieve low power consumption and wide-area communication. Wi-SUN has been deployed in large-scale commercial applications, mainly in smart metering. The physical layer of Wi-SUN is currently based on the IEEE 802.15.4 Smart Utility Network (SUN), and international standardization is underway to extend the transmission distance based on the current standardized SUN to meet the growing demand for IoT.

In this scheme, it is necessary not only to achieve the required transmission characteristics in various IoT use case environments but also to be tolerant of the co-channel interference that exists in many of the relevant frequency bands. In this paper, we propose a new IEEE 802.15.4 SUN Orthogonal Frequency Division Multiplexing (OFDM)-based physical layer using Single Carrier OFDM (SC-OFDM), which uses spreading and frequency hopping to achieve long-distance communication and improve communication quality in an interference environment.

We evaluated its basic transmission characteristics and transmission distance under multipath and co-channel interference using computer simulation. Even in urban areas, the proposed scheme achieved a transmission range of over 20 km in the Very High Frequency (VHF) band with a required packet error rate of 10-2, which is three times longer than the transmission distance of conventional SUN OFDM.

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This paper reports on the results of Wi-SUN FAN 1.0 [1] network re-formation timing characteristics. The authors have explored in detail the behaviour of the Wi-SUN FAN network under conditions of power-on-reset of all nodes in the network, given that the nodes were already authenticated onto the network and had retained their relevant security material. Of specific interest was the timing of the reformation in general and how such timing scaled with network size.

We provide details regarding:

  • The time required for network re-formation for a sparse, isotropically distributed networks with 100, 256, 530 and 1024 nodes, and
  • Details of the rates of re-formation and the associated probability density and probabilities of that the network will be re-formed within a specific time frame.

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Wireless Smart Utility Network Field Area Network (Wi-SUN FAN) is a technical specification of Wi-SUN that introduces multi-hop machine-to-machine transmission for advanced smart city infrastructure. Wi-SUN FAN uses the Internet Protocol Version 6 (IPv6) Routing Protocol for Low-Power and Lossy Network (RPL) as the routing protocol and expected transmission count (ETX) as the routing metric to build multi-hop networks. ETX is used to convert number of communications into a link metric, which measures the quality of communication between nodes. This metric measures the relative distance to the root node via adjacent nodes to determine the parent node.

However, this method of determining link metrics may cause nodes to frequently change their parents. If a node selects a parent with poor link quality, the communication reliability deteriorates; therefore, each node must appropriately select a candidate parent node. This article presents the transmission characteristics of Wi-SUN FANs and highlights the problems of conventional link metrics. Based on this, a novel method is proposed for calculating the link metric. The performed computer simulations verified the superiority of the proposed metric when the packet generation rate remained unaffected by the generation of control frames that switched the parent nodes.

Furthermore, the transmission success rate of the media access control (MAC) frame was experimentally measured in an office building using Wi-SUN FAN communication modules based on the proposed method. The evaluation confirmed that the proposed link metric improved the minimum MAC frame transmission success rate by 24.2% and the average success rate by 10.4%.

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2024

The Wi-SUN FAN (Wireless Smart Ubiquitous Network Field Area Network) standard is attracting great interest in various applications such as smart meters, smart cities and Internet of Things (IoT) devices due to the attractive features that the standard offers, such as multihop and mesh topologies, a relatively high data rate, frequency hopping, and interoperability between manufacturers. However, the process of connecting nodes in Wi-SUN FAN networks, which includes discovering, joining, and forming the network, has been shown to be slow, especially in multihop environments, which has motivated research and experimentation to analyze this process. In the existing literature, to measure network formation time, some authors have performed experiments with up to 100 devices, which is a costly and time-consuming methodology. Others have used simulation tools that are difficult to replicate, because little information is available about the methodology used or because they are proprietary. Despite these efforts, there is still a lack of information to adequately assess the formation time of Wi-SUN FAN networks, since the experimental tests reported in the literature are expensive and time-consuming. Therefore, alternatives such as computer simulation have been explored to speed up performance analysis in different scenarios. With this perspective, this paper is focused on the implementation of the Wi-SUN FAN network formation process using the Contiki-NG open source operating system and the Cooja simultor, where a functionality was added that makes it possible to efficiently analyze the network performance, thereby facilitating the implementation of new techniques to reduce network training time. The simulation tool was integrated into Contiki-NG and has been used to estimate the network formation times in various indoor environments. The correspondence between the experimental and numerical results obtained shows that our proposal is efficient to study the formation process of this type of networks.

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This paper reports on the results of multicast latency and round trip time measurements for a particular deployment of nodes forming a Wi-SUN FAN 1.0 [1] network. The authors have explored in detail the behaviour of the Wi-SUN FAN network used by Hee-Jun Lee and Sang-Hwa Chung, the authors of a prior paper [2], in order to provide more detail regarding the latencies and delays cited in that paper. 

We provide details regarding:

  • the timing of the component requests and responses that comprise the Lee and Chung round-trip and latency measurements, and
  • Additional timing and packet delivery ratio results for variations of the MPL [3] retransmission parameters for the Wi-SUN FAN protocol used on the Lee and Chung test network.

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In recent years, extensive research has been conducted on the Internet of Things (IoT). Wireless Smart Ubiquitous Network (Wi-SUN) has gained considerable attention as a wireless communication standard for IoT. Wi-SUN Field Area Network (Wi-SUN FAN) is a technical specification of Wi-SUN that can be implemented in both indoor and outdoor IoT communication infrastructure with multi-hop routing. Although Wi-SUN FAN version 1.0 (Wi-SUN FAN 1.0) has been standardized by IEEE 2857–2021, there have been no studies or reviews conducted on the transmission performance of Wi-SUN FAN 1.0 regarding transmission success rate and delay time using computer simulations and experimental evaluation environments involving actual devices. In this study, the specifications of the Wi-SUN FAN are reviewed, and the fundamental transmission performance, such as average transmission success rate and average delay time, is measured using computer simulation as reference data. An experimental evaluation environment involving actual devices is developed to validate the characteristics evaluated by computer simulation. The characteristics determined by the computer simulation and experimental evaluation environment are in good agreement. Using the validated simulator, we evaluate the transmission performance in the wireless IoT environment with one border router and 100 routers randomly arranged in a flat square field with 4,000 m on a side. The average transmission success rate is approximately 1 at 1.00 × 10−1 s−1 or less. Consequently, Wi-SUN FAN 1.0 can communicate with a higher transmission success rate even when transmitting frequent IoT-data, which is once every ten seconds.

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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.

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2023

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.

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In recent years, the Wireless Smart Utility Network for Field Area Network (Wi-SUN FAN) is widely used as an international standard for wireless communication systems of IoT systems such as smart metering systems and wireless sensor networks. This standard uses the Internet Protocol Version 6 (IPv6) Routing Protocol for Low-power and Lossy Networks (RPL) as a routing protocol to construct communication routes dynamically. However, depending on the terminal arrangement conditions, in some cases the transmission characteristics deteriorate due to traffic concentration at a particular terminal. In this paper, the transmission characteristics of Wi-SUN FAN are first presented. Then, the effect of packet buffer overflow on the transmission characteristics is evaluated. Then, we propose a control method to avoid traffic concentration by selecting communication routes according to the amount of packet buffer. Finally, we evaluate the transmission characteristics of the proposed method by computer simulation and show that this method maintains high transmission characteristics in small-scale dense deployments with almost no discarding owing to buffer overflow.

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Next-generation Internet of Things systems based on IEEE 802.15.4 Smart Utility Network (SUN) require (1) higher data rates, (2) mobility support, and (3) simultaneous connection of many terminals compared to existing commercial systems in smart metering systems. For (1), the use of IEEE 802.15.4-2020 SUN orthogonal frequency division multiplexing (OFDM) is considered. For (2), reception schemes for the SUN OFDM in a mobile environment are proposed. To address (3), it is necessary to secure as large a communication area as possible. However, in the ultra-high frequency (UHF) band represented by 920 MHz, the maximum transmission distance of SUN OFDM with a transmit power of approximately 20 mW is a few kilometers, assuming fixed communication in a typical urban environment. To extend the transmission distance, it is necessary to use a frequency lower than the UHF band or to increase the transmission power. To solve this problem, this paper proposes the use of SUN OFDM in the very high frequency (VHF) band, which has the advantage of longer transmission distance owing to its longer wavelength than the UHF band. However, many delayed signals are received due to multiple reflections. In particular, the maximum delay time of delayed waves can be as long as 20 µs in a rural area. Therefore, it is necessary to receive high-quality signals even in an environment with long delay waves, and to meet the required packet error rate (PER) even when the terminal is moved. In this paper, we first propose an estimation method for the propagation channel of SUN OFDM in the VHF band propagation environment and evaluate the PER characteristics in fixed and mobile environments via computer simulation. Consequently, a transmission distance of more than 10 km could be achieved in the VHF band, even in a rural area with a moving speed of 80 km/h.

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Wireless Internet of things (IoT) systems represented by a smart metering system using the UHF band, i.e., Sub-1GHz, have been examined. Many of these systems adopt IEEE 802.15.4-SUN and standardized Frequency Shift Keying (FSK). Although IEEE 802.15.4-SUN-FSK is a suitable transmission scheme for the transmission of numerical data, static image data, etc., the maximum transmission distance is 2 km in the range from 50 kbps to several 100 kbps, and further transmission distance is required for several 100 kbps. In this paper, we propose a modified IEEE 802.15.4-SUN-FSK scheme to enable wide-area transmission. In particular, we propose an IEEE 802.15.4-SUN-FSK with four modifications: (1) the use of the VHF band, (2) an extension of convolutional codes, (3) a simple method for calculating the soft decision for Viterbi decoding, (4) a method for MRC diversity without decoding the received signal. The transmission characteristics were evaluated by computer simulation. According to the simulation results, despite the presence of long delay waves exceeding 20 μs even at vehicle speeds of 80 km/h, the required packet error rate was achieved, and transmission distances of over 12.0 km in a metropolitan environment and 66.0 km in a rural environment were achieved.

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Currently, orthogonal frequency division multiplexing (OFDM), standardized in IEEE 802.15.4, has attracted attention as a transmission scheme for higher data rates, long-distance transmissions, and mobile communications for the expansion of Internet of Things (IoT) applications as well as for legacy IoT applications, such as smart metering systems and home-area networks. In particular, receiving schemes using IEEE 802.15.4-based OFDM have been actively examined to realize mobile communication. This study proposes a receiving scheme for IEEE 802.15.4 OFDM aimed at high-speed mobile IoT communication systems. In the time axis direction, the proposed scheme obtains channel estimates in the same manner as previous schemes. However, in the frequency axis, the proposed scheme obtains the channel estimates by copying estimates of neighboring subcarriers according to the coherence bandwidth of the multipath fading channel to update the channel estimates frequently. Computer simulation results show that the proposed scheme, including delay spread estimation can achieve mobile communication with a data rate of 100 Kb/s at moving speed of 200 km/h in the urban environment.

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In recent years, extensive research has been conducted on the Internet of Things (IoT). Wireless Smart Ubiquitous Network (Wi-SUN) has gained considerable attention as a wireless communication standard for IoT. Wi-SUN Field Area Network (Wi-SUN FAN) is a technical specification of Wi-SUN that can be implemented in both indoor and outdoor IoT communication infrastructure with multi-hop routing. Although Wi-SUN FAN version 1.0 (Wi-SUN FAN 1.0) has been standardized by IEEE 2857–2021, there have been no studies or reviews conducted on the transmission performance of Wi-SUN FAN 1.0 regarding transmission success rate and delay time using computer simulations and experimental evaluation environments involving actual devices. In this study, the specifications of the Wi-SUN FAN are reviewed, and the fundamental transmission performance, such as average transmission success rate and average delay time, is measured using computer simulation as reference data. An experimental evaluation environment involving actual devices is developed to validate the characteristics evaluated by computer simulation. The characteristics determined by the computer simulation and experimental evaluation environment are in good agreement. Using the validated simulator, we evaluate the transmission performance in the wireless IoT environment with one border router and 100 routers randomly arranged in a flat square field with 4,000 m on a side. The average transmission success rate is approximately 1 at 1.00 × 10 −1 s −1 or less. Consequently, Wi-SUN FAN 1.0 can communicate with a higher transmission success rate even when transmitting frequent IoT-data, which is once every ten seconds.

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2022

Recently, there has been a growing demand for the Internet of Things (IoT), which connects all types of devices to the Internet via wireless communications. Wireless Smart Ubiquitous Network Field Area Network (Wi-SUN FAN), a wireless communication standard for the IoT oriented to outdoor infrastructure, is attracting attention. Internet Protocol Version 6, routing protocol for Low-power and Lossy Networks (RPL) is adopted as a routing protocol in Wi-SUN FAN. In RPL, each node autonomously selects a parent node based on the network status and sends data to a root node (border router) via multi-hop communication. To reduce power consumption without degrading connectivity, it is necessary for nodes to adaptively control the transmission power based on the communication environment. This paper proposes an adaptive transmission power control method using Wi-SUN FAN standardized frames that can be applied to an upward link. The transmission success rate and energy required per received bit are evaluated to show that power control effectively reduces power consumption.

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With the growing power grid needs in recent years, several different Smart Meters (SMs) have evolved to address diverse challenges. However, interoperability for SMs suppliers is challenging due to the diversity of protocols, data models, and interfaces. In this way, the Wireless Smart Ubiquitous Network (Wi-SUN) is the straightforward solution to address such issue.In this work, we present a simple, low-cost, open-source platform to assess the interoperability with Wi-SUN Field Area Network (FAN) devices. This platform allows the testing of devices under different conditions to check their conformance with the Wi-SUN standard.

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Energy utilities increasingly require a communication medium that ensures not only good performance but also interoperability between equipment from different manufacturers. As an open protocol initially developed with energy utilities in mind, Wi-SUN FAN holds great potential to meet this need. This technical report describes the results of field tests conducted on Wi-SUN equipment—developed under ANEEL R&D project PD-00047-0080/2017—using two distinct communication networks; the findings demonstrate that, for applications involving packet reception control, network availability is approximately 99%.

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In this study, we developed a USB-type radio board equipped with a wireless smart ubiquitous network (Wi-SUN) field area network (FAN) wireless module capable of performing multi-hops for hundreds of units and an integrated evaluation board to evaluate the transmission performance of Wi-SUN FAN with hundreds of wireless devices in the laboratory. The USB-type radio board achieves low power consumption by controlling the operation of the Wi-SUN FAN wireless module mounted on the board from the outside. Therefore, this study measured the current consumption characteristics. Furthermore, fundamental evaluations of the transmission performance, such as the network configuration time and packet transmission success rate, were performed by configuring a large-scale wireless evaluation system with tree and star topologies using 100 USB-type radio boards and the integrated evaluation boards. A transmission success rate of 95% or higher was achieved continuously for 12 h when all terminals sent a UDP data with a packet length of 200 bytes to the border router of Wi-SUN FAN with a data rate of 100 kbps at the intervals of 150 s.

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In this study, to evaluate large-scale IoT applications comprising numerous radio devices, we developed a wireless emulator that can evaluate various radio communication systems in cyberspace, without requiring actual radio devices, in addition to verifying transmission performance in an operation similar to actual operations. Because the wireless emulator can separately and independently operate each radio node by porting software that realizes protocols other than the physical layer on the actual radio device to the emulator, the software can be implemented in the actual radio device as it is after completing the emulation. Furthermore, in the emulator, the topology of the network can be altered freely in cyberspace. Moreover, because the simulation of the physical layer is analyzed independently in the emulator, various applications can be evaluated, regardless of mobile and fixed communications. In this study, the Wi-SUN FAN system was adopted as the evaluation example of the wireless communication system using this emulator, star and tree topologies with Wi-SUN FAN nodes were formed in cyberspace, and transmission characteristics, such as average packet transmission success rate and average delay time, were evaluated. The characteristics were compared with the computer simulation results without actual operations and were consistent.

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Since Smart Grids, Smart Cities and IoT are in a very active expansion phase, we investigate some of the possibilities of integration between different network technologies to expand the options for the use of Smart End Devices. This work presents a series of improvements made on the communication of LoRaWAN Gateways and their Network Servers that allow these technologies to be installed over Low-Rate Wireless Networks communication channels, such as Wi-SUN Smart Grid Networks. The proposed improvements were validated on a network proto-type assembled in a Lactec laboratory. Our results, in addition to supporting the viability of the integration, show that the protocol modifications can yield a reduction of up to 99% in the number of control messages sent through the Wi-SUN network.

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The Internet of Things (IoT) has been increasingly realizing communication among diverse devices, in addition to sensors and meters. IoT is equipped with communication functions and entails interconnection via the Internet to collect and use various data. Wireless smart ubiquitous network (Wi-SUN) conforms to the international standard IEEE 802.15.4, and it has therefore been considered a wireless communication standard for IoT. The Wi-SUN uses frequency-shift keying (FSK), standardized in IEEE 802.15.4, and achieves a typical data rate of 100 kbps. However, when Wi-SUN is used in other IoT applications to realize smart cities and smart factories, communications with higher data transmission rates and longer distances are required. Orthogonal frequency division multiplexing (OFDM), standardized in IEEE 802.15.4, has been used as a transmission method to satisfy the associated requirements. In this study, the fundamental transmission characteristics of IEEE 802.15.4 OFDM were first evaluated through computer simulations and laboratory experiments by employing developed evaluation boards. Next, the outdoor transmission performance of IEEE 802.15.4 OFDM was evaluated using the developed evaluation boards. Experimental results indicate that IEEE 802.15.4 OFDM can yield the same transmission distance as that of FSK using a smaller transmit power to achieve the packet error rate (PER) smaller than 10%.

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The Wi-SUN FAN (Wireless Smart Ubiquitous Network Field Area Network) standard is currently attracting interest for adoption across various applications, as it meets the demand for large-scale interconnection among diverse smart devices. However, the standard’s network formation process is slow, posing a challenge for dense networks. This study analyzes network formation time through experiments on a multi-hop network comprising eight devices (seven hops), focusing on the standard’s Join States 1 and 3, which utilize distinct network discovery packets governed by the Trickle timer algorithm. Various configuration settings for these two states are examined and discussed, enabling the identification of the network formation process characteristics inherent to this standard.

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Radio communication systems using the frequency-shift keying (FSK) scheme standardized by the IEEE 802.15.4-SUN standard can realize low-power consumption and highly reliable communications and are mainly adopted for smart metering as part of the Internet of Things (IoT). However, smart metering has recently broadened its application expectations, with broadband and long-distance communications now required. To fulfill these requirements, orthogonal frequency-division multiplexing (OFDM) has been incorporated into the IEEE 802.15.4-SUN and 802.15.4x standards. However, comprehensive transmission performance analysis of OFDM under static and multipath fading environments has not been conducted. In this article, we first evaluated the packet error rate (PER) of OFDM assuming fixed communications using computer simulations. We then evaluated the transmission distance of OFDM and showed that OFDM can communicate at transmission distances up to 3.0 times longer than those specified in IEEE 802.15.4-SUN FSK. Next, the PER in a mobile communication environment was evaluated using computer simulations. When only the long training field (LTF) was used to estimate multipath radio channels, the required PER of 10% was not achieved, even in a mobile communication environment at a speed of several km/h. To solve this problem, we proposed a receiving scheme which included a new channel estimation scheme. This scheme successively utilized not only the LTF but also pilot signals inserted into the transmitter to estimate radio propagation characteristics. Computer simulation results showed that the required PER was achieved even in a mobile communication environment at 30–40 km/h by using the proposed scheme.

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Smart Cities and the Internet of Things (IoT) are here to stay; concepts once showcased at trade fairs and conferences a few years ago have now become rapidly expanding realities. What do these solutions have in common? They require connectivity to enable their systems to acquire data, perform necessary processing, and generate information for users. Without connectivity linking devices, systems, and users, Smart Cities and IoT simply would not exist. This paper presents the results of a research and development project under the ANEEL program titled “Smart City Applications on the Ipiranga Smart Grid Network.”

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The wireless smart ubiquitous network field area network (Wi-SUN FAN) is a wireless communication standard for the Internet of things (IoT) in outdoor large-scale multi-hop networks. Currently, frequency shift keying (FSK) standardized in IEEE 802.15.4 is employed as the physical layer of the Wi-SUN FAN. Improving data rate of the physical layer is essential to realize expected requirements toward the next-generation IoT systems. In this paper, we introduce the orthogonal frequency division multiplexing (OFDM) standardized in IEEE 802.15.4 into the Wi-SUN FAN to improve data rate without increasing the system bandwidth. We evaluated the packet error rate (PER) characteristics under inter-signal interference in the transition period of the physical layer from FSK to OFDM through a computer simulation. Results showed that the new interference caused by the mixture of OFDM degraded the PER characteristics, in comparison with the interference between FSKs. However, the interference between different channels was limited because the required carrier-to-interference power ratio to achieve PER=10% was below –10dB. Furthermore, we evaluated the transmission characteristics of the Wi-SUN FAN in the media access control layer and verified that the introduction of the OFDM is effective for improving the maximum system throughput by 1.9 times when performing frequency hopping.

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2021

This paper proposes a novel routing method considering load balancing to improve transmission characteristics of a large-scale Wi-SUN field area network (Wi-SUN FAN) based on IEEE 802.15.4. Wi-SUN FAN is a wireless communication standard that enables the interconnection of many Internet-of-Things (IoT) devices outdoors. Wi-SUN FAN prevents packet collisions by frequency hopping in the media access control (MAC) layer. Besides, Wi-SUN FAN constructs multi-hop networks autonomously using Internet protocol version 6 routing protocol for low-power and lossy networks (RPL) at the network layer. In RPL, each node determines its parent node based on the quality of communication. Therefore, many nodes are likely to choose the same parent node with good radio reachability, resulting in many packets being sent to the parent node. The heavy load for the specific node makes frequency hopping not work effectively, and transmission characteristics deteriorate. The proposed routing method with a load-balancing algorithm eliminates the load concentration and improves the average transmission success rate by approximately 9.4% on the specific nodes.

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Due to the merits of simple implementation and low-power consumption, frequency shift keying (FSK) is widely used in wireless communication systems for the Internet of things (IoT) such as Wi-SUN field area network (Wi-SUN FAN). To expand IoT capacity or diversify IoT application scenarios, higher data rates are highly expected. In this paper, we propose a novel design of data rate enhancement for IEEE 802.15.4-based 2-FSK transmission scheme which meets the radio requirements defined by ARIB STD-T108 regulation in Japan. Fundamental evaluations and field experiments with developed integrated circuits (ICs) are conducted to evaluate the transmission performance of FSK with enhanced data rate parameters. Results show that with the ICs, the data rate of 600 kbps is achieved with a required input power increase of 7.0 dB compared with the conventional data rate of 100 kbps, and can achieve the packet error rate (PER) smaller than 10% for 250 m on line-of-sight (LoS) routes in urban environments. Moreover, the frequency interference level of the proposed FSK scheme is measured to evaluate the performance in practical radio conditions. Results provide reference for the channel management to operate FSK-based communication systems.

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Radio interference or jamming can cause isolated area in advanced metering infrastructure (AMI) based on Wire-less smart utility network (Wi-SUN), in which conventional recovery techniques cannot cope with. In this paper, we deploy narrowband internet-of-things (NB-IoT) interface to some smart meters to act as emergency gateway, called ResiLite. An optimal ResiLite placement algorithm for enhancing network resilience is proposed. We define an implicit resilience metric based on path diversity and cluster closeness. The defined metric is used to form an integer linear programming (ILP) problem, then we solve the ILP to obtain optimal ResiLite placement. Simulation results show that the optimal ResiLite placement improves Wi-SUN AMI network resilience (defined as the number of surviving nodes with packet delivery ratio (PDR) above 99% under disturbance) by up to 167% compared to an AMI without ResiLite, and up to 29% compared to uniformly random ResiLite placement, respectively.

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In this paper, the world’s first experimental evaluation of the Wi-SUN Japan Utility Telemetering Association (JUTA) profile-compliant feathery receiver-initiated transmission (JUTA F-RIT) protocol is conducted. Firstly, the transmission success rate in an interference environment is evaluated by theoretical analysis and computer simulations. The analysis is derived from the interference model focusing on the carrier sense. The analysis and simulation results agree as regards the transmission success rate of the JUTA F-RIT protocol. Secondly, we develop the dongle-type prototype that hosts the JUTA F-RIT protocol. Measurement results in a cochannel interference environment show that the transmission success rate at the lower MAC layer is around 94% when the number of terminals is 20. When the waiting time for the establishment of the communication link can be extended to exceed 10 s, the JUTA F-RIT protocol can achieve the transmission success rate of over 90% without the re-establishment of the communication link and re-transmission of data frames. Moreover, the experimental results are examined from two viewpoints of the performance of the frame transmissions and the timeout incident, and the feature of the JUTA F-RIT protocol are discussed.

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Smart grids (SG) have been successfully deployed in several countries. In Brazil, the main agency for the wide(r) SG deployment are the electricity companies that operate under federal or state government concession. This paper presents a framework for sharing the SG communication infrastructure with smart city applications. This sharing would accelerate the development and implementation of new applications, especially in less developed countries or in regions with scarce communication resources. We present preliminary performance results for an existing SG. Our results indicate that, with only the energy metering application, the network operates with a duty cycle of less than 2%. Our work will assess the impact on overall performance of smart city applications sharing the SG.

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This paper aims to identify Wi-SUN devices using physical layer fingerprint. We first extract physical layer features based on the received Wi-SUN signals, especially focusing on device-specific clock skew and frequency deviation in FSK modulation. Then, these physical layer fingerprints are used to train a machine learning-based classifier and the resulting classifier finally identifies the authorized Wi-SUN devices. Preliminary experiments on Wi-SUN certified chips show that the authenticator with the proposed physical layer fingerprints can distinguish Wi-SUN devices with 100 % accuracy. Since no additional computational complexity for authentication is involved on the device side, our approach can be applied to any Wi-SUN based IoT devices with security requirements.

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This paper aims to identify Wi-SUN devices using physical layer fingerprint. We first extract physical layer features based on the received Wi-SUN signals, especially focusing on device-specific clock skew and frequency deviation in FSK modulation. Then, these physical layer fingerprints are used to train a machine learning-based classifier and the resulting classifier finally identifies the authorized Wi-SUN devices. Preliminary experiments on Wi-SUN certified chips show that the authenticator with the proposed physical layer fingerprints can distinguish Wi-SUN devices with 100 % accuracy. Since no additional computational complexity for authentication is involved on the device side, our approach can be applied to any Wi-SUN based IoT devices with security requirements.

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In this work, experimental tests of interoperability between devices from different providers were performed using the Wireless Smart Ubiquitous Network Field Area Network (Wi-SUN FAN) profile. This profile is part of the Wi-SUN Alliance, supporting Low Power and Lossy Networks (LLNs). The interoperability experiments were carried out in two different operation modes of the profile. Additionally, security was enabled and disabled, as well as channel hopping functionality, using the 915 MHz-b band allocated to Brazil. The interoperability was verified through the communication between the different devices, using response time and success rate as metrics of the communication analysis.

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2020

In this paper, we propose a heterogeneous wireless management scheme for a home area network (HAN) system. The HAN system integrates multiple wireless systems (e.g., the Wi-Fi operating in the 2.4 GHz-band and the Wi-SUN field area network (Wi-SUN FAN) operating in the sub-GHz-band) for the in-home health care management system. The system assumes a medical care and proactive health management, and a variety of data such as the vital data, the environment data, and the user activity data are collected to a coordinator by using IoT gateways (IoT-GWs). For the transmission scheme between the loT-GWs, we compare two schemes; the conventional FAN scheme and the proposed fast-path scheme. In the FAN scheme, all of the measured data are collected by using the Wi-SUN FAN multi-hop transmission. On the other hand, the proposed fast-path scheme uses both the Wi-Fi and the Wi-SUN FAN, and a part of the data is offloaded to the Wi-Fi from the Wi-SUN FAN. These two schemes are evaluated by computer simulations. In the case that only the vital and environmental data are collected to the coordinator, these data can be collected with the end-to-end (E2E) transmission success rate of 98 % in the proposed fast-path scheme compared with 92 % in the conventional FAN scheme.

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Advanced metering infrastructure (AMI) based on Wireless Smart Utility Network (Wi-SUN) employs carrier sense multiple access (CSMA), hence suffers from poor network performance when the number of nodes increases but without proper design of data collection scheduling. In this paper, we introduce an interference-aware TDMA-like optimal data collection scheduling, in which a link-timeslot assignment problem is formed by considering interference constraint to achieve better spatial timeslot reuse. A constraint for achieving consecutive flow for multi-hop transmission is also introduced to avoid modifications on the original CSMA protocol, and hence the proposed scheduling is standard compliant. Our results show that the proposed scheduling reduces the total data collection time of Wi-SUN AMI network with 100(200) smart meters by 59%(48%), 33%(32%), and 19%(13%), respectively, when compared with conventional Wi-SUN AMI, conventional TDMA scheduling and heuristic scheduling based on 2-rank distance interference model.

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The wireless smart ubiquitous network field area network (Wi-SUN FAN), a wireless communication standard for Internet of Things (IoT) applications, such as smart metering and monitoring, has been attracting attention. Conventionally, the information transmitted by the Wi-SUN FAN is numerical values and/or character strings, such as metering information. It has been thought that the Wi-SUN FAN cannot transmit video images because the data rate is at most in hundreds of kbps. However, owing to improvements in video compression and transmission technologies in recent years, video images can be transmitted at a transmission rate of hundreds of kbps. In this study, the feasibility of video transmission over the Wi-SUN FAN is evaluated using low-rate video compression and transmission technology. First, several network topologies for video transmission by the current Wi-SUN FAN with multi-hop are evaluated by computer simulations. Consequently, adequate numbers of nodes and multi-hops in the Wi-SUN FAN are recommended. Subsequently, using a recommended value, an experimental system is configured and the video transmission performance over the Wi-SUN FAN is evaluated experimentally.

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The wireless smart ubiquitous network (Wi-SUN) field area network (FAN) attracts attention as a wireless communication standard for large-scale Internet of Things (IoT) systems. Currently, frequency shift keying (FSK) defined in IEEE 802.15.4 is adopted in the physical layer of the Wi-SUN FAN. To improve the network performance toward next-generation IoT systems, a data rate enhancement scheme for FSK has been proposed. However, there is no evaluation of data rate improvement effect by adopting the data rate enhanced FSK on the transmission characteristics of the Wi-SUN FAN. Besides, introducing the data rate enhanced FSK causes the bandwidth to increase. For multiple systems to coexist in limited frequency bands, it is necessary to achieve high spectral efficiency even when the Wi-SUN FAN adopts the data rate enhanced FSK. In this paper, we evaluate the transmission characteristics of the Wi-SUN FAN adopting the high-speed FSK of 600 kbps by computer simulations. The simulation results show that the system throughput improves by 2.5 times, but the bandwidth also increases by 2.5 times compared to the existing system. Furthermore, we propose highly-dense frequency hopping based on a novel channel arrangement scheme to improve spectral efficiency and compatibility with the existing system design while the data rate enhanced FSK is adopted. The evaluation results show that the system throughput in the proposed scheme is 2.4 times of the existing system while using less than half of the bandwidth compared to the conventional channel arrangement scheme.

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Wireless smart utility network field area network (Wi-SUN FAN), which configures very large-scale multi-hop networks, has been standardized to promote interoperable open standards for machine-to-machine (M2M) communication. In the media access control (MAC) layer, Wi-SUN FAN adopts a carrier sense multiple access with collision avoidance (CSMA/CA) and a channel hopping (CH) to avoid interferences between devices. A channel schedule controls the operational channel of CH and it is dominant for both unicast and broadcast transmission performances. In this paper, the impact of channel schedule on the network performance is studied to enhance the unicast transmission throughput. The transmission throughput of a Wi-SUN FAN system in four multiple tandem topologies are evaluated by computer simulations in various channel schedule schemes. The simulation results show that by adopting CH and setting the broadcast interval (BI) coefficient to the optimal value that depends on the network topology, higher unicast throughput can be achieved and the transmission interval of broadcast control frames can be preserved at 131 s. In the case of a multiple tandem topology that consists of 33 devices, by adopting CH and setting the BI coefficient to be 30, the unicast throughput increases by up to 12.2% compared to the case of default parameter configuration recommended in Wi-SUN FAN standard.

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Prior to 2020

Wireless Smart Utility Network (Wi-SUN) has been standardized to provide Machine-to-Machine (M2M) communication in Low power and Lossy Networks (LLNs). Wi-SUN Field Area Network (FAN) is the specification that maintains a wireless multi-hop communication on the advanced smart city infrastructure. Wi-SUN FAN has adopted the Internet Protocol version 6 (IPv6) Routing Protocol for LLNs (RPL) which has been successfully optimized in fixed terminals. To establish the embedded smart city, mobile nodes are required to implement the RPL as well. Nevertheless, the RPL fails to choose the appropriate routing node when the terminal moves, resulting in high packet loss. To improve the transmission performance, the system simulator of Wi-SUN FAN with the Expected Transmission Count (ETX) based algorithm is firstly developed to evaluate the end-to-end transmission success rate via multi-hop transmission and the simulation result clarifies that the critical factor causing low transmission performance is the unsmooth handover of the receiver node at first hop. Then, a dynamic routing algorithm based on ETX transition is proposed and the simulation result finally assures the smooth handover, resulting in the improved transmission performance.

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Recently, the sub-gigahertz band (e.g. 920 MHz in Japan) has been extensively used for the wireless Internet of Things (IoT) because of its advantages such as excellent radio wave reachability, less interference, and many developments and implementations of large-scale wireless multi-hop networks by using interference avoidance technologies such as the media access control (MAC) protocol and frequency hopping. There are two types of the wireless communication systems for IoT: Wi-SUN FAN, as an asynchronous wireless system, and MAC protocol with time-slotted channel hopping (TSCH), as a synchronous wireless system. Wi-SUN FAN and TSCH systems have already been commercialized and installed to the several IoT environments and are expected to expand in scale in the future. Since both systems are operated in the same frequency band of the sub-gigahertz band, the intersystem interference is a concern for the coexistence of systems. In this paper, the possibility of the coexistence between the systems is examined. The intrasystem and intersystem interferences are evaluated by computer simulations in the case of operating the two systems by themselves and that of operating the systems simultaneously in the same frequency channel.

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This paper proposes and develops a wide area wireless smart utility network (Wi-SUN) system and measures the transmission performance of the system by field experiments. In the wide area Wi-SUN system, a high performance base station (BS) can expand the direct communication distance to wireless devices with sensors and meters by enriching BS functions, i.e. in the down link (DL), transmission power is enlarged, and in the up link (UL), high gain directional antennas are used. Field experiments of the system are carried out to validate effectiveness and availability of the proposed system. The experimental systems are compliant with the regulation for Japan, namely transmission powers of BS and devices are 250 mW and 20 mW respectively, modulation scheme is Gaussian frequency shift keying (GFSK) and the operational frequency band is 920 MHz. Experimental results show that the proposed system expand the direct communication distance around 4.33 times longer than that of conventional system in the practical urban environment.

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Wireless Smart Ubiquitous Network Field Area Network (Wi-SUN FAN) is a profile developed by the Wi-SUN Alliance—which creates specifications for field area networks—designed to support Low-Power and Lossy Networks (LLNs). The Wi-SUN FAN profile provides IPv6-based transport services and employs the IPv6 Routing Protocol for LLNs (RPL) for network formation and packet routing at the network layer. RPL enables initial network construction prior to data packet transmission within the FAN, utilizing various metrics to determine the cost of the paths connecting the nodes. In this study, RPL was configured using parameters defined by Wi-SUN FAN. Simulations were conducted across three scenarios with varying node placements using the Cooja simulator. Network performance was evaluated by analyzing convergence time, traffic overhead associated with RPL control messages, network latency, and packet delivery rates for each scenario.

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This paper summarizes Wi-SUN communication systems and their physical (PHY) layer and media access control (MAC) specifications. Firstly, the Wi-SUN communication systems are categorized into three. The key PHY and MAC standards, IEEE 802.15.4-SUN and .4e, that configure the systems are explained, and fundamental transmission performances of the systems in the PHY layer and MAC layer are evaluated by computer simulations. Then, the Wi-SUN alliance and the Wi-SUN profiles that include IEEE 802.15.4-SUN and .4e are explained. Finally, to understand the transmission performance of actual IEEE 802.15.4-SUN Wi-SUN radio devices, PER performances under AWGN and multipath fading environments are measured by using IEEE 802.15.4-SUN compliant and Wi-SUN alliance certified radio modules. This paper is an instruction paper for the beginners of the Wi-SUN based communications systems.

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Wi-SUN FAN (wireless smart utility network field area network) is a technical specification of Wi-SUN that introduced multi-hop M2M (machine-to-machine) transmission for advanced smart city infrastructure. To construct a multihop network, the RPL (IPv6 routing protocol for low power and lossy networks) and the ETX (expected transmission count) are adopted as routing protocol and routing metric, respectively, in Wi-SUN FAN. The combination of the RPL and the ETX may cause a node to change its parent frequently. If a node selects a parent with lower link quality, communication reliability becomes lower. To avoid the frequent parent changing problem, parent candidates of each node should be selected appropriately. In this paper, we propose two schemes to select parent candidates for each node (i.e., optimized RSL (received signal level) threshold scheme and MAC (media access control) address filtering scheme) to stabilize the multi-hop routing construction in the Wi-SUN FAN systems. The proposed schemes are experimentally evaluated in a real field in an office building using the IoT-GWs (internet of things gateways) with Wi-SUN FAN module. By using the optimized RSL threshold scheme, the number of parent changes can be reduced by up to 96% compared to the case with unoptimized RSL threshold. Also, the number of parent changes can be reduced by up to 77% with the proposed MAC address filtering scheme compared to without the proposed scheme.

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