Hiroyuki Yomo

Kansai University · Department of Electrical and Electronic Engineering

This paper focuses on top-k query in cluster-based multihop wireless sensor networks (WSNs) employing wake-up receivers. We aim to design wake-up control that enables a sink to collect top-k data set, i.e., k highest readings of sensor nodes within a network, efficiently in terms of energy consumption and delay. Considering a tree-based clustered W...

Over-the-air computation is a promising technique for efficiently aggregating data in sensor networks. This method requires that signals from all nodes arrive at the sink aligned in signal magnitude, which faces the reliability issue, especially in times of channel fading. To solve this problem, in this letter, we propose an amplify-and-forward bas...

When a wireless LAN station (STA) installed on a mobile device, such as drone, communicates with an access point (AP) deployed over the ground, its link condition becomes unstable due to mobility and/or interference from surrounding equipment. In this paper, in order to realize reliable data transmissions in such a severe condition, we introduce a...

Information freshness and high energy-efficiency are key requirements for sensor nodes serving Industrial Internet of Things (IIoT) applications, where a sink node must collect informative data before a deadline to control an external element. Pull-based communication is an interesting approach for optimizing information freshness and saving wastef...

This paper proposes an energy–efficient wake–up control for periodical top– ${k}$ query in wireless sensor networks employing wake–up receivers. The wake–up procedure is designed in such a way that it only activates a subset of nodes that contribute to grasping the information on the top– ${k}$ ranking set with high accuracy, which prevents unnec...

In this paper, we propose rate adaptation mechanisms for robust and low–latency video transmissions exploiting multiple access points (Multi–AP) wireless local area networks (WLANs). The Multi–AP video transmissions employ link–level broadcast and packet–level forward error correction (FEC) in order to realize robust and low–latency video transmiss...

Autonomous mobile devices, such as robots and unmanned aerial vehicles, as alternatives to humans, are expected to be applied to searching for and manipulating a variety of emergent events of which the location and number of occurrences are unknown. When an autonomous mobile device searches for an event, it needs to sense a physical signal emitted...

This article proposes content–based wake–up control for top– ${k}$ query in wireless sensor networks, where the sink attempts to collect information on top– ${k}$ nodes or top– ${k}$ values from sensor nodes employing wake–up receivers. The wake–up procedure is designed with a goal of waking up only the subset of nodes which have the relevant da...

In this paper, we advocate applying the concept of content-based wake-up to distributed estimation in wireless sensor networks employing wake-up receivers. With distributed estimation, where sensing data of multiple nodes are used for estimating a target observation, the energy consumption can be reduced by ensuring that only a subset of nodes in t...

This letter proposes a rate control for robust data transmissions utilizing multiple access points (APs) combined with packet-level forward error correction (FEC). Beacon frames received from multiple APs are used to select an appropriate set of PHY and FEC rates to be employed for uplink transmissions, which is based on a machine-learning techniqu...

When we collect vital data from exercisers by putting wireless sensor nodes to them, the reliability of the wireless data collection is dependent on the position of node on the body of exerciser, therefore, in order to determine the suitable body position, it is essential to evaluate the data collection performances by changing the body positions o...

In the fields of professional and amateur sports, players’ health, physical and physiological conditions during exercise should be properly monitored and managed. The authors of this paper previously proposed a real-time vital-sign monitoring system for players using a wireless multi-hop sensor network that transmits their vital data. However, exis...

The authors are trying to construct a real-time vital sensing system during exercise based on image-assisted routing. In order to estimate locations of target exercisers based on image processing required for multi-hop networking, robust personal identification is indispensable because visual target tracking executed after detection sometimes fails...

This paper focuses on on-demand wireless sensor networks (WSNs) where a wake-up receiver is installed into each node. In on-demand WSNs, each node sends a wake-up signal including a wake-up ID assigned to a specific destination node in order to remotely activate its main radio interface. This wake-up control helps each node to reduce energy consume...

Photoplethysmography (PPG) is simple, non-invasive and unobtrusive, so it has been commonly used for heart rate (HR) sensing during exercise. PPG-based HR sensor can be applied for almost any part of human body where there is an artery close to the sensor, just by stabilizing it on the skin surface with belt. However, in order to make the HR sensor...

The introduction of a drone-based mobile sink into wireless sensor networks (WSNs), which has flexible mobility to move to each sensor node and gather data with a single-hop transmission, makes cumbersome multi-hop transmissions unnecessary, thereby facilitating data gathering from widely-spread sensor nodes. However, each sensor node spends signif...

Although there have been a variety of wearable Information and Communication Technology (ICT) devices around us, which are easily connectable to smart phones, unfortunately, very few people are practicing everyday healthcare using them. There must be some causes in it. This paper examines educational and literate causes in the impracticality of eve...

In this paper, we investigate how to improve the reliability of heart–rate monitoring of a large number of people playing sports over a limited area of sports field. Densely– located nodes attached to exercisers transmit heart–rate data to a data collection node simultaneously, which negatively affects the reliability of data collection due to seve...

Wireless sensor and actuator networks (WSANs) are required to achieve both energy-efficiency and low-latency in order to prolong the network lifetime while being able to quickly respond to actuation commands transmitted based on the real-time sensing data. These two requirements are in general in a relationship of trade-off when each node operates...

Energy harvesting wireless sensor networks (EH-WSNs) are being actively studied in order to solve the problems faced by battery-operated WSNs, namely the cost for battery replacement and the negative impact on the environment. In EH-WSNs, each node harvests ambient energy, such as light, heat, vibration, and uses it for sensing, computations, and w...

In this paper, we focus on oxygen consumption (VO2) estimation using 6-axis motion sensor (3-axis accelerometer and 3-axis gyroscope) for people playing sports with diverse intensities. The VO2 estimated with a small motion sensor can be used to calculate the energy expenditure, however, its accuracy depends on the intensities of various types of a...

This paper focuses on oxygen consumption (VO2) estimation using 6-axis motion data (3-axis acceleration and 3-axis angular velocity) that are obtained from small motion sensors attached to people playing sports with different intensities. In order to achieve high estimation accuracy over a wide range of intensities of exercises, we apply neural net...

This paper considers on-demand WiFi wake-up where a wake-up receiver is installed into each WiFi device. The wake-up receiver detects a wake-up call by finding the predefined length of WiFi frames, which corresponds to a wake-up ID, through envelope detection with limited signal processing. Since each wake-up receiver continuously observes the WiFi...

This paper investigates the impact of hidden nodes (HNs) on on-demand access point (AP) wake-up that is employed to realize energy-efficient wireless LANs (WLANs). The considered wake-up signaling exploits IEEE 802.11 signals transmitted by a WLAN station (STA) to remotely activate a sleeping AP: a STA with communication demands transmits a series...

In the field of education such as elementary and middle schools, teachers want to take care of schoolchildren during physical trainings and after-school club activities. On the other hand, in the field of sports such as professional and national-level sports, physical or technical trainers want to manage the health, physical and physiological condi...

Real-time vital sensing/monitoring for persons during exercises is essential for not only avoiding injuries and diseases but also effective training. For the vital sensing, we have developed a heart rate sensing technique canceling motion artifact induced during exercise and an energy expenditure sensing technique using tri-axial accelerometer. On...

In frame-length based wake-up control, a wake-up receiver smoothens the signal envelope by low-pass-filtering (LPF) before frame length detection. However, the LPF also has a side effect of distorting the rising and falling edges of the envelope. This letter analyzes the effect of LPF on frame length detection, and suggests measuring potential fram...

Energy harvesting wireless sensor network (EHWSNs) are being actively studied in order to solve the problems faced by battery-operated WSNs, namely the cost for battery replacement and impacts on the environment. In EH-WSNs, each node harvests ambient energy, such as light, heat, vibration, and uses it for sensing, computations, and wireless commun...

Sensor networks are playing more and more important roles, e.g., accurately monitoring the generation and consumption of electric power for the purpose of smart grid. In these applications, sensor nodes, working with battery, should be put into sleep in the idle state to prolong network lifetime and be activated on demand to ensure real-time respon...

This paper presents an overview of physical (PHY) and medium access control (MAC) layers for IEEE 802.11a, which is a standard of a broadband high-speed wireless local area network (WLAN). IEEE 802.11a uses 5 GHz frequency band and its PHY is based on orthogonal frequency division multiplexing (OFDM). In this paper, we evaluate the OFDM- based PHY...

Vital signs obtained from people playing various types of sports can be exploited not only for diagnosing their physical conditions but also for learning the best practice to be followed to enhance their sporting abilities and skills. In this paper, focusing on a framework to collect vital data from a human group consisting of a massive number of p...

Radio-On-Demand Networks (ROD) has been proposed in order to improve energy-efficiency of WiFi device, which offers wireless access in an on-demand manner. Each WiFi device in ROD is equipped with a low-power wake-up receiver, which detects the length of wireless LAN frames through envelope detection and on-off-keying (OOK) processing. A STA, upon...

In order to reduce energy wastefully consumed by WiFi device, Radio-On-Demand Networks (ROD) has been proposed, which offers wireless access in an on-demand manner. Each WiFi device in ROD is equipped with a low-power wake-up receiver which is capable of detecting the length of frames observed over WiFi channels through envelope detection and on-of...

Physical layer network coding (PLNC) has been proposed to improve throughput of the two-way relay channel, where two nodes communicate with each other, being assisted by a relay node. Most of the works related to PLNC are focused on a simple three-node model and they do not take into account the impact of interference from other transmissions. Unli...

Wireless local area networks (WLANs) are widely deployed recently. But many basic service sets (BSSs) nearby have to share a common channel due to the limitation in the spectrum resource. To get higher throughput with newly deployed access points (APs), it is necessary to improve spatial reuse of the channels by transmit power control (TPC). The ac...

In this paper, green wireless local area networks (WLANs), where idle access points (APs) are put into sleep and activated upon the request of mobile nodes, are realized by exploiting WLAN signals to convey wake-up messages. Specifically, wake-up messages, sent by nodes, are modulated onto frame lengths (physical transmission time) of successive WL...

Physical layer network coding (PLNC) has the potential to improve throughput of multi-hop networks. However, most of the works are focused on the simple, three-node model with two-way relaying, not taking into account the fact that there can be other neighboring nodes that can cause/receive interference. The way to deal with this problem in distrib...

In order to reduce energy wastefully consumed by access points (APs) in wireless LAN (WLAN), Radio-On-Demand (ROD) WLAN has been proposed, which offers wireless access only when and where it is needed in an on-demand manner. Each AP in ROD is equipped with a wake-up receiver, which transits a state of AP from sleep to active by receiving a wake-up...

This paper investigates the impact of hidden nodes on wake-up signaling employed to realize energy-efficient wireless LAN (WLAN). The considered wake-up mechanism is based on frame length modulation which exploits WLAN frames as a wake-up signal: a station with communications demands transmits a series of WLAN frames with length corresponding to wa...

This paper focuses on Radio-On-Demand (ROD) wireless LANs (WLANs) in which the operating mode of Access Points (APs) changes from an 'active' communication state to 'sleep' state in case where there is no data traffic transferred from/to the AP in order to avoid unnecessary power consumption. We propose an automatic sleep control strategy, which fr...

In this paper, we design a simple, low-cost, and low-power wake-up receiver which can be used for an IEEE 802.11-compliant device to remotely wake up the other devices by utilizing its own wireless LAN (WLAN) signals. The employed wake-up mechanism utilizes the length of 802.11 data frame generated by a WiFi transmitter to differentiate the informa...

This paper investigates wake-up ID and protocol design for radio-on-demand (ROD) wireless LAN (WLAN) where wake-up radio is applied to access point (AP) in order to save energy consumed by WLAN. Each AP in ROD WLAN is transited to a sleep state when there is no associated user. A wake-up receiver installed into each AP is used to detect a wake-up s...

This paper considers a radio-on-demand (ROD) wireless LAN (WLAN) in which access points (APs) are put into a sleep mode during idle periods and woken up by stations (STAs) upon communications demands. The on-demand wake-up is realized by a wake-up receiver which is equipped with each AP and is used to detect a wake-up signal transmitted by STA. In...

Recent investigations show that (i) access points (APs) of wireless local area networks (WLANs) are idle during much of the time, and, (ii) an AP in its idle state without forwarding any packets still consumes a large percentage of power. Therefore, it is necessary to put idle APs into sleep so as to realize green WLANs. The problem, however, is ho...

Optimized resource allocation of the Downlink (DL) in wireless systems utilizing Multi-Carrier (MC) transmission requires Channel State Information (CSI) feedback for each user/subchannel to the Base Station (BS), consuming a high amount of Uplink (UL) radio resources. To alleviate this problem, several works have considered contention-based CSI fe...

Network coding is an effective method to improving relay efficiency, by reducing the number of transmissions required to deliver data from source(s) to destination(s). However, its performance may be greatly degraded by rate mismatch, which is seldom touched in previous works and remains a challenge. In this paper, we reinterpret network coding as...

Access points (APs) of wireless LANs (WLANs), always powered on and ready to serve mobile nodes, consume a large amount of power in total, but are idle during much of the time. Previous protocol-based sleep-wakeup scheduling schemes partially solve this problem, but the large wakeup delay remains a problem. Aiming at realizing Radio-On-Demand WLANs...

This paper considers secondary usage of spectrum resources that are allocated to frequency division duplexing (FDD)-based cellular systems. We propose an interference cancellation technique using the concept of distributed antenna array. We show that the interference from the primary cellular system can be cancelled at a secondary node equipped wit...

In this paper, we introduce Radio-On-Demand (ROD) wireless LAN (WLAN) in which access points (APs) are put into a sleep mode during idle periods and woken up by stations (STAs) upon communications demands. The on-demand wake-up is realized by a wake-up receiver which is equipped with each AP and is used to detect a wake-up signal transmitted by STA...

This paper discusses the possibility of deploying a short-range cognitive radio (secondary communication system) within the service area of a primary system. Although the secondary system interferes with the primary system, there are certain locations in the service area of the primary system where the cognitive radio can reuse the frequency of the...

Although IEEE 802.11e standard is approved for better QoS support, the bandwidth allocation to individual access categories (ACs) can unpredictably vary, preventing efficient QoS provisioning. In this paper, we propose a scheme that jointly maximizes channel capacity and provides network-wide service differentiation to provide fine grained proporti...

Network coding is an effective method to improving relay efficiency by reducing the number of transmissions. However, its performance is limited by several factors such as packet length mismatch and rate mismatch. Although the former may be solved by re-framing, the latter remains a challenge and is likely to greatly degrade the efficiency of netwo...