Kiyoshi Hamaguchi

Symbol rate and modulation level-controlled adaptive modulation/TDMA/TDD system for high-bit-rate wireless data transmission

This paper proposes a time-division multiple-access/time-division duplex (TDMA/TDD)-based symbol rate and modulation level-controlled adaptive modulation system for high-bit-rate data transmission. The proposed system controls both the symbol rate and modulation level for the next transmission time slot according to the estimated carrier power to noise spectral density ratio (C/N/sub 0/) and delay spread for the time slot to achieve higher bit rate and higher transmission quality as well as higher delay-spread immunity. It is demonstrated by computer simulation and laboratory experiments that the proposed system can achieve a higher average bit rate with higher transmission quality in comparison with the fixed-rate quaternary phase-shift keying (QPSK) system and modulation level-controlled adaptive modulation system in both flat Rayleigh and frequency-selective fading environments. The simulated and experimental results also show that the proposed adaptive modulation techniques can be applied to 1-2-Mb/s indoor and outdoor microcellular systems with its delay spread of up to 250 ns and its terminal mobility of up to pedestrian speed without employing any special antifrequency-selective fading techniques, such as the adaptive equalizer and space diversity.

Millimeter-wave remote self-heterodyne system for extremely stable and low-cost broad-band signal transmission

We have developed a millimeter-wave remote self-heterodyne transmission system that enables extremely stable and low-cost broad-band transmission in the millimeter-wave band. The system was applied to a 60-GHz-band transmission system for the first time. The transmitter of the developed system transmits RF modulated signals and a local oscillation signal simultaneously, and the receiver detects these signals by using a square-law-type detection technique, thus creating a very stable and low phase-noise millimeter-wave transmission link without the use of an expensive and more advanced frequency-stabilization technology. Since the receiver no longer requires a millimeter-wave oscillator for frequency conversion, the devices used in this system can be miniaturized and the cost of the system can be reduced. This paper discusses the performance of the developed system in terms of its phase-noise degradation and carrier-to-noise power ratio (CNR). We also discuss the optimal transmitter design to obtain the maximum CNR. Using our miniaturized monolithic millimeter-wave integrated-circuit-based 60-GHz-band experimental system, we demonstrate that our millimeter-wave transmission link is completely free of phase-noise and frequency-offset degradation due to the use of a millimeterwave local oscillator. We show that equal transmission-power distribution between the RF signal and local carrier gives the maximum CNR under the transmission-power-limited conditions. Also, we demonstrate that QPSK-modulated satellite broadcast multichannel video signals with a 300-MHz bandwidth, in total, can be successfully transferred over a distance of 8 m.

R&D and standardization of body area network (BAN) for medical healthcare

A new major application of UWB is medical healthcare using advantages of low power spectrum density, high capacity of transmission and accurate ranging. As a core network of medical healthcare based on ICT, i.e. medical ICT, a body area network (BAN) has been researched and developed. BAN can provide a wide range of applications in primary for medical healthcare such as tele-metering vital sign, e.g. ECG, EEG, tele-controlling medical equipment, e.g. capsule endoscope and in addition for non-medical service such as entertainment. To harmonize with the strong demands from both medical healthcare societies and ICT industries, a standardization committee referred to as IEEE 802.15.6 was formally set up in December 2007. The objective of 15.6 is to define new physical (PHY) and media access control (MAC) layers for wireless BAN (WBAN). This invited paper introduces a progress of research and development of body area network, i.e. BAN and its standardization in IEEE802.15.6 in a field of medical ICT in order to encourage global collaboration as well as planting many R&D and business seeds in academia and industry.

Channel Models for Medical Implant Communication

Information regarding the propagation media is typically gathered by conducting physical experiments, measuring and processing the corresponding data to obtain channel characteristics. When this propagation media is human body, for example in case of medical implants, then this approach might not be practical. In this paper, an immersive visualization environment is presented, which is used as a scientific instrument that gives us the ability to observe RF propagation from medical implants inside a human body. This virtual environment allows for more natural interaction between experts with different backgrounds, such as engineering and medical sciences. Here, we show how this platform has been used to determine channel models for medical implant communication systems.

A Wireless Video Home-link Using 60GHz Band: Concept and Performance of the Developed System

A concept and requirements of a millimeter-wave video transmission system as a wireless home-link using 60-GHz band are described. This system can transmit broadcast television (TV) signals from TV antennas to TV set and thus can be regarded as a substitute for a feeder line. The feasibility study by investigating the systems CNR and SNR performances using MMIC-based experimental setup is also described.

RF Chipset for Impulse UWB Radar Using 0.13-

A novel ultra-wideband impulse radar architecture for 24-GHz-band short-range radar was developed using 0.13-mum InP high electron-mobility technology. The transmitter part generates an extremely wideband impulse from a pulse generator and then filters it through a bandpass filter. The obtained impulse had a full width at half maximum of 9 ps. Its frequency spectrum spread from dc to over 40 GHz and achieved sufficient flatness in the target band. The power amplifier (PA) for the transmitter had a gain of 15 plusmn0.1 dB, and the low-noise amplifier (LNA) for the receiver had a gain of 40 plusmn1 dB and a minimum noise figure of 1.9 dB. The achieved flatness of integration gain including the PA, LNA, and RF switch was less than plusmn1.2 dB. These RF circuits with gain flatness make a simple matched filter configuration possible without the use of a conventional correlator composed of a local oscillator. An ultra high-speed sample and hold circuit having an ultra-long hold time of more than 3 ns was also developed to detect the output pulses from the matched filter

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The creation of countermeasures against a large-scale disaster is an important focus of research for the future. This article briefly introduces some Japanese research and development activities for disaster-related technologies, including those carried out by the National Institute of Information and Communications Technology (NICT). First, we discuss lessons learned from the Great East Japan Earthquake that occurred on March 11, 2011. We show that the preferred communication tool in a disaster situation depends on the time that has elapsed after the disaster. We then summarize several research projects for developing robust and dependable communication networks, including an information distribution platform, and outline the research projects of NICTs Resilient ICT Research Center as well.

InP-HEMT Technology

This paper describes the first time experimental studies on 60-GHz band transmissions of terrestrial digital broadcasting signals (ISDB-T) with 64-QAM modulations on coded orthogonal frequency division multiplexing (COFDM) format. It has been a very difficult experiment to accomplish because it requires very stable and low phase-noise oscillators in the millimeter-wave band. The use of our proposed millimeter-wave self-heterodyne system, overcame this problem without using a stable oscillator, and provided a bit error rate (BER) of less than 10/sup -6/ without any forward error correction. We also discuss the relationship between the carrier-to-noise power ratio and the BER obtained, and demonstrate that the penalty of the required CNR for our experimental system is less than 1 dB compared to the results of a back-to-back BER test.

Resilient ICT research based on lessons learned from the Great East Japan Earthquake

Wireless Body Area Network (WBAN) has drawn considerable attention as a means to gather vital data from on-body sensors. In WBAN, however, a star network topology is mainly supported, connecting a central coordinator to vital sensor nodes put on different positions of a human body, so the links between the coordinator and the sensor nodes are often blocked by parts of the human body when the man takes different postures and motions. Therefore, to support real-time vital data gathering in WBANs, a scheme for mitigating such link blockings is essential. This paper proposes a cooperative scheme for ensuring reliable data transmission in a WBAN. For each sensor node on a human body, the proposed scheme autonomously assigns a sensor node as a cooperator out of other sensor nodes and the cooperator retransmits packets from the sensor node for a coordinator instead of the sensor node when the direct link between them is blocked. After presenting the cooperator selection algorithm, using the Received Signal Strength Indication (RSSI) data obtained from the experiment in an anechoic chamber, the paper evaluates the performance of the proposed scheme in terms of average and worst outage rates.

60 GHz band 64 QAM/OFDM terrestrial digital broadcasting signal transmission by using millimeter-wave self-heterodyne system

This paper provides channel models for wireless body area network (WBAN) in UWB frequency band, and also presents performance evaluation using the derived channel models. The channel model is given by a statistical model in which parameters are derived from actually measured channel transfer function in a hospital room environment. These models enable us to evaluate performance of UWB-based WBAN. In this paper, bit error ratio (BER) and packet error ratio (PER) are shown for UWB-based WBAN which employs a signalling scheme among OOK, BPPM, BPSK, and DPSK. The results show that both OOK and BPPM which generally uses a non-coherent receiver provide severe performance when the target PER is set to 10–2 under the packet size of 128 bytes. The other signalling schemes achieve the required performance from the viewpoint of such error ratio.