Teruhisa Ninomiya

60-GHz transceiver for high-speed wireless LAN system

We have developed a 60-GHz Transceiver unit for high-capacity wireless LAN systems, employing state-of-the-art MMIC technology. This prototype showed sufficiently good performance in an ethernet-compatible 10-Mbps random access CSMA/CD wireless system, and proved its potential usefulness in various commercial products.

Zone division model for capacity analysis in multi-hop data acquisition systems with hidden nodes

Data acquisition systems play an important role in several industries. Because highly scalable ad-hoc networks with multi-hop transmissions can be easily constructed at low cost, such networks are considered suitable for data acquisition systems. However, a lack of centralized control makes it difficult to respond to congestion when system capacity is exceeded. Therefore, the estimation of system capacity is a critical issue for system design. In this paper, we propose a novel zone division model to analyze the capacity of multi-hop data acquisition systems using Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocols. We divide the one-hop area to a gateway (GW) into two zones: (1) an outer zone where an access node (AN) can relay packets from multi-hop ANs; and (2) an inner zone where ANs cannot relay packets. Using this approach, we calculate packet loss for each zone, considering the difference in the communication range of the GW and ANs, as well as the collision with hidden nodes. Simulation results show that our model achieves higher estimation accuracy than conventional methods, indicating that we have successfully modeled phenomena of the real system more accurately.

Polarization diversity antenna with L-shaped slit for wireless sensor network

In this paper, a planar polarization diversity antenna with low correlation coefficient and low mutual coupling is developed for wireless sensor network system at UHF region. A slit, to eliminate mutual coupling between two antennas, inserted on ground plane of conventional diversity antenna is straight; this fact causes a restriction to layout of a PCB board at UHF region. To save a large area for the electric component, we employ an L-shaped slit which has an advantage of compact and same performance as straight slit. The prototype of diversity antenna has been developed and measured. The measured result obtained the very low correlation coefficient of 0.021 and very low mutual coupling about -20 dB at 1 GHz in this work.

RSS-based localization considering topographical feature for pasturing

This paper describes a localization technique to be used for a pasturing management system. Issues to be addressed are low energy consumption for battery operation and radio propagation degradation due to undulating lands in pastures. We decided to use received signal strength- (RSS-) based trilateration for low power, and to consider the topographical effect using particle filters (PF). To evaluate the proposed algorithm, an experimental campaign was conducted in a pasture with an area of 2 km2. The results show that the proposed algorithm improves the localization accuracy by 28% when compared with the least square (LS) algorithm, whereas plain PF increased it by 14%. These results show that our technique meets the requirements for pasture management.

Automatic Standard Classification Method for the 2.4 GHz ISM Band

As IoT (Internet of Things) systems using wireless standards sharing the 2.4 GHz ISM band become widespread, radio interference often disturbs data communication. In order to mitigate interference-related problems, it would be helpful to have a method that determines to which standard a received packet belongs. However, conventional methods do not analyze the actual environment of congestion nor do they classify narrowband signals. In this paper, we propose identification algorithms and an automatic standard classification method that identifies WLAN/IEEE 802.15.4/BT (Bluetooth)/BLE (Bluetooth Low Energy), which are considered typical standards in the 2.4 GHz ISM band. The results show that the identification algorithms improve detection sensitivities compared to conventional ones, and the proposed method of automatic standard classification accurately analyzed the actual situation where radio waves of plural standards overlap one another.

Realizing safe and reliable vital sings monitoring with wireless body area networks

In this paper, we report development and performance verification of a wireless body area network prototype compliant with the MAC protocol of the IEEE802.15.6 BAN. The relaying functionality which utilizes a relay between a hub and a node is confirmed when a direct path between them is not available due to shadowing effects. The delay due to switching to the relay topology is less than one second. Also, ID-based frequency channel hopping mechanism is introduced and verified to be able to quickly avoid frequency channel interference among BANs. In addition to that, transmission power control with body movement detection is employed to reduce sporadic disconnection through giving an extra amount of transmission power when the node detects a large fluctuation in received power. With functionalities mentioned above, the prototype is expected to be used for medical monitoring applications where requirements for data delay and disconnection are rather severe.