Haruhisa Ichikawa

Ubiquitous Networks with Radio Space Extension over Broadband Networks

Many devices are expected to be networked with wireless appliances such as radio frequency identification (RFID) tags and wireless sensors, and the number of such appliances will greatly exceed the number of PCs and mobile telephones. This may lead to an essential change in the network architecture. This paper proposes a new network architecture called the appliance defined ubiquitous network (ADUN), in which wireless appliances will be networked without network protocol standards. Radio space information rather than individual appliance signals is carried over the ADUN in the form of a stream with strong privacy/security control. It should be noted that this is different from the architectural principles of the Internet. We discuss a network-appliance interface that is sustainable over a long period, and show that the ADUN overhead will be within the scope of the broadband network in the near future.

Method for estimation of distance between objects and its application for finding lost objects

In this paper, we propose a method to estimate the distance between objects attached with radio-frequency identification (RFID) tags that are used for finding lost objects. Many systems for finding lost objects adopt real-time location systems (RTLSs) using received signal strength indication (RSSI). The fundamental structure of a general method for an RTLS using RSSI involves the creation of a number of reference nodes whose locations are known in advance. Crowded objects often form a group; hence, it is very helpful to find some object members of the group in a certain place so as to find the lost object belonging to the group. However, an RTLS is not required to know the objects located in a certain place or to estimate the distance between these objects. Hence, we propose a method to estimate the distance between objects rather than the individual object locations without using a method to obtain location-dependant information.

Dynamic Spectrum Sensing for Energy Harvesting Wireless Sensor

Energy harvesting wireless sensors are driven by electric power extracted from hidden environmental source of energy, such as imperceptible vibrations of walls and floors. It has been shown that radio transmitter system can be powered by energy harvesters with substituting ring for crystal oscillators, which, however, causes frequency instability in oscillator. In order to receive message from such sensors, a receiver must be able to accurately detect transmitted frequencies that may differ among respective sensors. Fast wideband radio frequency sensing schemes using filter-based energy detectors were proposed. These schemes were designed to detect radio devices operating according to known specifications, this paper proposes a dynamic spectrum sensing scheme using a fast fourier transform (FFT) based energy detector for radio devices without knowing radio frequencies. The experimental and theoretical results of this study demonstrate that dynamic spectrum sensing with an FFT-based energy detector can retrieve signal frequencies faster than traditional schemes. It is also shown that it is possible to calculate a suitable set of parameters for minimizing the total sensing time associated with any given pairing of frequency missing rate and resolution.

Active RFID Attached Object Clustering Method with New Evaluation Criterion for Finding Lost Objects

An active radio frequency identification (RFID) tag that can communicate with smartphones using Bluetooth low energy technology has recently received widespread attention. We have studied a novel approach to finding lost objects using active RFID. We hypothesize that users can deduce the location of a lost object from information about surrounding objects in an environment where RFID tags are attached to all personal belongings. To help find lost objects from the proximity between RFID tags, the system calculates the proximity between pairs of RFID tags from the RSSI series and estimates the groups of objects in the neighborhood. We developed a method for calculating the proximity of the lost object to those around it using a distance function between RSSI series and estimating the group by hierarchical clustering. There is no method to evaluate whether a combination is suitable for application purposes directly. Presently, different combinations of distance functions and clustering algorithms yield different clustering results. Thus, we propose the number of nearest neighbor candidates (NNNC) as the criterion to evaluate the clustering results. The simulation results show that the NNNC is an appropriate evaluation criterion for our system because it is able to exhaustively evaluate the combination of distance functions and clustering algorithms.

Remote implementation of GNU radio-based SDR development environment

Software-defined radio (SDR) is used in several areas, such as the verification and implementation of radio prototypes. The SDR environment is generally configured with an analog-to-digital converter (ADC) and a personal computer (PC). However, since ADCs and PCs are fixed configurations, reconfigurations are needed in order to respond to different data sources and computing environments when the radio protocol or SDR are indefinite. To enable this reconfiguration, we present a cloud platform that has scalable computing resources and data sources deployed in a wide area, using an existing SDR development environment. In order to apply the existing SDR development environment to the cloud platform, UI separation and data management are required. In this manuscript, we implement an SDR environment for many unspecified users through UI separation by selecting the GNU Radio Companion (GRC) as the platform. We focused on compatibility and flexibility with regard to the configuration, in order to allow the user to adjust the resources consumed by the PC. The results show that one particular implementation of the remote SDR execution and development is suitable. In addition, we confirmed the compatibility with GRC in terms of user skills and software assets, and achieved distributed processing to allocate resources between the client and cloud according to the users discretion, by dividing the processing of the SDR on the basis of the function unit.

Active RFID attached object clustering method based on RSSI series for finding lost objects

An active radio frequency identifier (RFID) tag that can communicate with smartphones using Bluetooth Low Energy technology has recently received widespread attention. Indeed, many products have been released that aim to find lost objects using the received signal strength indication (RSSI). However, these products do not provide sufficiently accurate location information to find objects. In this paper, we propose an active RFID attached object clustering method based on RSSI series for finding lost objects. This approach to find lost objects does not execute existing localization methods. We hypothesize that users can deduce the location of a lost object from information about surrounding objects in an environment where RFID tags are attached to all personal belongings. To help find lost objects from the proximity between RFID tags, the system calculates the proximity between a pair of RFID tags from the RSSI series, and estimates the groups of objects in the neighborhood. We present a method for calculating the proximity of the lost object to those around it using a distance function between RSSI series and estimating the group by hierarchical clustering. We confirm the validity of the proposed method, and determine the most appropriate pairs of four distance functions and four clustering algorithms. From the experimental results, it is apparent that our method provides a clear advantage in finding lost objects at low financial and installation cost, and can estimate groups accurately even if the smartphone or RSSI sensor is moving quickly.

Invited Talk: Appliance Defined Ubiquitous Network

Many devices are expected to be networked with wireless appliances such as radio frequency identification (RFID) tags and wireless sensors, and the number of networked wireless appliances will greatly exceed the number of PCs and mobile telephones . This may lead to an essential change in the network architecture. This paper proposes a new network architecture called the appliance defined ubiquitous network (ADUN), in which wireless appliances will be networked without network protocol standards. Wireless space information rather than an individual appliance signal is carried over the ADUN in the form of a stream with strong privacy/security control. It should be noted that this is different from the architectural principles of the Internet. We discuss a network-appliance interface that is sustainable over a long term, and show that the overhead of the ADUN will be within the scope of the broadband network in the near future

SDR processing delay estimation applying correlation detection for structure health monitoring using multi-subcarrier multiple access

Wireless and battery-less structural health monitoring (SHM) that detect structural damage at low cost are required. To achieve this, the use of multi-subcarrier multiple access (MSMA) communication method is being considered. In MSMA, time synchronization of sensing data is shifted owing to software defined radio (SDR) processing. Therefore, when an SHM monitoring method requiring time synchronization of sensing data is used, time synchronization taking SDR processing delay into account is necessary. In this study, we propose a system that estimates SDR processing delay by correlation detection and acquires time synchronization of sensing data. We measured SDR delay estimation with time accuracy by installing this system on an experimental object. Results showed that the error of the allowable processing delay estimation was different, and time synchronization can be achieved by performing sensing once by the SDR processing delay estimation method using correlation detection.

Inter-zone interference avoidance using channel reservation in multiple subcarrier multiple access scheme

Interest in structural health monitoring for which sensors are used to detect structural damage has increased. For low-cost installation, these sensors are required to be batteryless and wireless. The objective of this study is to realize structural health monitoring for large-scale structures using a multiple subcarrier multiple access scheme that functionally enhances sub-carrier methods in radio-frequency identification (RFID) communication. When the target structure is of large scale, it is necessary to divide the structure into several zones because of communication distance restrictions. In this case, some wireless sensor nodes are located in zones where adjacent transceiver ranges overlap, thereby transmitting their sensing signals to both zones; thus, the problem of inter-zone interference due to unintended subcarriers arises. Therefore, we propose a method of inter-zone interference avoidance in which channels are reserved for wireless sensors overlapping adjacent zones. Evaluation via simulation reveals that the average communication capacity reduction can be suppressed compared with the case without channel reservation.

Monopulse switching to cancel phase offset in array antenna comprising multiple COTS SDRs

This paper proposes a phase offset canceler for an array antenna, which comprises multiple low-cost commercial of the shelf (COTS) software defined radio (SDR) devices. The main challenge is the phase synchronization of SDR devices because each SDR devices has its own phase offset when it produces IQ stream. We devise a simple yet effective method to cancel the phase offset of individual SDR device using a double-pole, double-throw (DPDT) switch which is implemented between antenna and SDR device. The DPDT switch is controlled according to the frame timing of each IQ stream to produce two set of measurements, from which we can compute angle of arrival (AoA) with a simple signal processing. We refer this mechanism as “Monopulse Switching”. We evaluated the working principle experimentally to reveal Monopulse switching successfully cancel phase offset to detect AoA without any initial calibration and achieves 2.8 degree measurement accuracy.