International Journal of Distributed Sensor Networks, 2005
We propose a method for managing the spontaneous organization of sensor activity in ad hoc wirele... more We propose a method for managing the spontaneous organization of sensor activity in ad hoc wireless sensor systems. The wireless sensors exchange messages to coordinate responses to requests for sensing data, and to control the fraction of sensors which are active. This method can be used to manage a variety of sensor activities. In particular, it can be used for reducing the power consumption by battery operated devices when only low resolution sensing is required, thus increasing their operation lifetimes.
2014 International Symposium on Antennas and Propagation Conference Proceedings, 2014
This paper proposes a method of pathloss fitting by deciding the prediction formula as a function... more This paper proposes a method of pathloss fitting by deciding the prediction formula as a function of azimuth, which is centered at a transmission source of incumbent system. We are studying the framework of white space boundary estimation with a smaller number of sensors. The framework decides the white space boundary by estimating coverage of incumbent radio systems with positions of transmission sources and predicted pathloss. To realize high accuracy estimation of white space boundary, a sophisticated method of pathloss fitting with a smaller number of sensors is required. The proposed method decides the prediction formula continuously for every azimuth with utilizing sensing data efficiently to meet the requirements.
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 2002
We analyze the synchronizability of synchronous distributed oscillators (SDOs) [3], a novel clock... more We analyze the synchronizability of synchronous distributed oscillators (SDOs) [3], a novel clocking scheme for microprocessors. A computer-aided perturbation analysis is developed for such systems, where analytically tractable equations of the clock phases are reduced from experimental data reflecting all circuit details. Using this reduction, a theory is constructed to explain the underlying mechanism of the synchronization in SDOs. It systematically explains the observed phenomena, the existence and stability of the (mutually) synchronized states, and the transition from the in-phase synchronized state to the out-of-phase (but still synchronized) state. Furthermore, the present theory of phase reduction provides a new design principle of coupled oscillators based on "the equation"; a precise delay control (less than the gate delay) circuit can be designed in a simple and general form.
In multihop ad hoc networks that use conventional IEEE 802.11, long transient resynchronisation s... more In multihop ad hoc networks that use conventional IEEE 802.11, long transient resynchronisation states are often generated when multiple IBSSs merge. A simple modification of the conventional timing synchronisation method is proposed to reduce such synchronisation bottlenecks. When the proposed modification is applied, a self-adaptive synchronisation ability is observed in simulations, which makes resynchronisation times much shorter and reduces energy consumption.
Abstract. It is well known that the NIST statistical test suite was used for the evaluation of AE... more Abstract. It is well known that the NIST statistical test suite was used for the evaluation of AES candidate algorithms. We have found that the test setting of Discrete Fourier Transform test and Lempel-Ziv test of this test suite are wrong. We give four corrections of mistakes in the test ...
Wireless sensor and actuator networks (WSANs) are required to achieve both energy-efficiency and ... more 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 with well-known duty-cycling modes: nodes need to make their radio interfaces (IFs) frequently active in order to promptly detect the communication requests from the other nodes. One approach to break this inherent trade-off, which has been actively studied in recent literature of wireless sensor networks (WSNs), is the introduction of wake-up receiver that is installed into each node and used only for detecting the communication requests. The main radio IF in each node is woken up only when needed, i.e., in an on-demand manner, through a wake-up message received by the wake-up receiver. In this paper, we introduce radio-ondemand sensor and actuator networks (ROD-SAN) where the concept of wake-up receiver is applied to realize on-demand WSANs. We first evaluate data collection rate, packet delivery latency, and energy-efficiency of ROD-SAN and duty-cycling modes defined in IEEE 802.15.4e by computer simulations. Then, we present our test-bed implementation of ROD-SAN including all protocols from the lowest layer of wake-up signaling to the application layer offering the functionalities of information monitoring and networked control. Finally, we show experimental results obtained through our field trial in which 20 nodes are deployed in an outdoor area with the scale of 450 m × 200 m. The numerical results obtained by computer simulations and experiments confirm the effectiveness of ROD-SAN to realize energy-efficient and high-response WSANs.
Electronics and Communications in Japan (Part II: Electronics), 2000
In this paper, onoff intermittency observed in a ring of four-coupled PLLs is studied theoretical... more In this paper, onoff intermittency observed in a ring of four-coupled PLLs is studied theoretically and experimentally. There exists a semistable invariant manifold in the phase space of this system. The orbit is irregularly transitioning between the laminar state constraint to the invariant manifold and the burst state jumping outward. In this research, the transversal Lyapunov exponent is first computed. It is then pointed out that onoff intermittency can appear with many parameter values. As an example, it is made clear from the calculations of several statistical characteristic quantities such as the local transversal expansion rate and laminar phase distribution that the intermittency generated with one of these parameters is an onoff intermittency. Further, by studying the bifurcation of the periodic solution on an invariant manifold, the generating mechanism of this onoff intermittency is made clear geometrically.
International Journal of Distributed Sensor Networks, 2005
We propose a method for managing the spontaneous organization of sensor activity in ad hoc wirele... more We propose a method for managing the spontaneous organization of sensor activity in ad hoc wireless sensor systems. The wireless sensors exchange messages to coordinate responses to requests for sensing data, and to control the fraction of sensors which are active. This method can be used to manage a variety of sensor activities. In particular, it can be used for reducing the power consumption by battery operated devices when only low resolution sensing is required, thus increasing their operation lifetimes.
2014 International Symposium on Antennas and Propagation Conference Proceedings, 2014
This paper proposes a method of pathloss fitting by deciding the prediction formula as a function... more This paper proposes a method of pathloss fitting by deciding the prediction formula as a function of azimuth, which is centered at a transmission source of incumbent system. We are studying the framework of white space boundary estimation with a smaller number of sensors. The framework decides the white space boundary by estimating coverage of incumbent radio systems with positions of transmission sources and predicted pathloss. To realize high accuracy estimation of white space boundary, a sophisticated method of pathloss fitting with a smaller number of sensors is required. The proposed method decides the prediction formula continuously for every azimuth with utilizing sensing data efficiently to meet the requirements.
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 2002
We analyze the synchronizability of synchronous distributed oscillators (SDOs) [3], a novel clock... more We analyze the synchronizability of synchronous distributed oscillators (SDOs) [3], a novel clocking scheme for microprocessors. A computer-aided perturbation analysis is developed for such systems, where analytically tractable equations of the clock phases are reduced from experimental data reflecting all circuit details. Using this reduction, a theory is constructed to explain the underlying mechanism of the synchronization in SDOs. It systematically explains the observed phenomena, the existence and stability of the (mutually) synchronized states, and the transition from the in-phase synchronized state to the out-of-phase (but still synchronized) state. Furthermore, the present theory of phase reduction provides a new design principle of coupled oscillators based on "the equation"; a precise delay control (less than the gate delay) circuit can be designed in a simple and general form.
In multihop ad hoc networks that use conventional IEEE 802.11, long transient resynchronisation s... more In multihop ad hoc networks that use conventional IEEE 802.11, long transient resynchronisation states are often generated when multiple IBSSs merge. A simple modification of the conventional timing synchronisation method is proposed to reduce such synchronisation bottlenecks. When the proposed modification is applied, a self-adaptive synchronisation ability is observed in simulations, which makes resynchronisation times much shorter and reduces energy consumption.
Abstract. It is well known that the NIST statistical test suite was used for the evaluation of AE... more Abstract. It is well known that the NIST statistical test suite was used for the evaluation of AES candidate algorithms. We have found that the test setting of Discrete Fourier Transform test and Lempel-Ziv test of this test suite are wrong. We give four corrections of mistakes in the test ...
Wireless sensor and actuator networks (WSANs) are required to achieve both energy-efficiency and ... more 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 with well-known duty-cycling modes: nodes need to make their radio interfaces (IFs) frequently active in order to promptly detect the communication requests from the other nodes. One approach to break this inherent trade-off, which has been actively studied in recent literature of wireless sensor networks (WSNs), is the introduction of wake-up receiver that is installed into each node and used only for detecting the communication requests. The main radio IF in each node is woken up only when needed, i.e., in an on-demand manner, through a wake-up message received by the wake-up receiver. In this paper, we introduce radio-ondemand sensor and actuator networks (ROD-SAN) where the concept of wake-up receiver is applied to realize on-demand WSANs. We first evaluate data collection rate, packet delivery latency, and energy-efficiency of ROD-SAN and duty-cycling modes defined in IEEE 802.15.4e by computer simulations. Then, we present our test-bed implementation of ROD-SAN including all protocols from the lowest layer of wake-up signaling to the application layer offering the functionalities of information monitoring and networked control. Finally, we show experimental results obtained through our field trial in which 20 nodes are deployed in an outdoor area with the scale of 450 m × 200 m. The numerical results obtained by computer simulations and experiments confirm the effectiveness of ROD-SAN to realize energy-efficient and high-response WSANs.
Electronics and Communications in Japan (Part II: Electronics), 2000
In this paper, onoff intermittency observed in a ring of four-coupled PLLs is studied theoretical... more In this paper, onoff intermittency observed in a ring of four-coupled PLLs is studied theoretically and experimentally. There exists a semistable invariant manifold in the phase space of this system. The orbit is irregularly transitioning between the laminar state constraint to the invariant manifold and the burst state jumping outward. In this research, the transversal Lyapunov exponent is first computed. It is then pointed out that onoff intermittency can appear with many parameter values. As an example, it is made clear from the calculations of several statistical characteristic quantities such as the local transversal expansion rate and laminar phase distribution that the intermittency generated with one of these parameters is an onoff intermittency. Further, by studying the bifurcation of the periodic solution on an invariant manifold, the generating mechanism of this onoff intermittency is made clear geometrically.
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Papers by Akio Hasegawa