Tsutayuki Shibata

Analysis of On-Body Transmission Mechanism and Characteristic Based on an Electromagnetic Field Approach

In this study, an electromagnetic field approach is used to clarify the mechanism of on-body transmission. A homogeneous cylinder is used as an arm model, and the characteristic of electromagnetic field distribution around the cylinder is extracted based on surface wave approximation and numerical analysis, respectively. As a result, the surface wave approximation is found to be valid in the far-field region from the excitation source in the frequency range of 10-150 MHz. Moreover, in the near-field region of the excitation source, the attenuation along the cylinder surface is much smaller than that toward the outside. In addition, by using a numerical human body model, the path loss for on-body transmission is also formulated.

Adaptive beam steering reception system for ISDB-T based on pre-FFT diversity technique

The reception of high-definition television in a mobile environment with the same quality as that achieved at home has been considered to be difficult to achieve. In an attempt to solve this problem, we have developed an adaptive beam steering reception system and evaluated the performance of this new system by both indoor and outdoor experiments involving the reception of high-definition television. The experimental results revealed that the reception performance was significantly improved, such that terrestrial digital television broadcasts can be received in high-speed moving environments, and with the same stability as broadcasts that are received at home in a fixed reception area.

Maximum likelihood decoding for wavelet packet modulation

The multi-carrier modulation (MCM) technique is an attractive approach for high-speed digital radio communication systems in order to achieve a high spectral efficiency and to combat the frequency selectivity of the channel. Orthogonal frequency division multiplexing (OFDM) is a kind of MCM technique. Wavelet packet modulation (WPM) is another kind of MCM technique using the wavelet transformation instead of the Fourier transformation to multiplex information symbol sequences. In this paper we propose a maximum likelihood decoding method for WPM without coding before transmitting the signal. The proposed method performs maximum likelihood sequence estimation by utilizing a signal obtained in an intermediate stage of the demultiplexing process. Then, bit error performance under a flat fading channel and frequency-selective fading channel is evaluated by computer simulation. According to the results, the proposed method can improve the bit error performance in the region of high Doppler frequency.

CEllular Local Area Radio Network: CELARN

The cellular local area radio network (CELARN), which is suitable for transmitting data to indoor mobiles, such as forklifts in factories and warehouses, is proposed. CELARN consists of some radio networks and a wired network which integrates the radio networks. The base stations are connected to one another by the wired network in a logical ring. A data-frame makes the round of the base stations to transmit data. Moreover, the data-frame behaves as a token of the common radio control channel to prevent collisions. The transmission delay performance of CELARN in a car manufacturing factory is analyzed for the practical use.<<ETX>>

Estimation of received signal characteristics in mobile radio environments

A method to estimate the received signal characteristics in mobile radio environments that considers the power gain pattern of the receiving antenna has been developed. The delay-Doppler spectrum is also considered in this estimation method. The estimation method can be used as a tool to relate the performance of a mobile antenna in free space and received signal characteristics in mobile radio environments. The angular probability density distribution of wave arrival depending on the delay time and wave arrival angles is defined. The received signal characteristics are estimated assuming a general urban environment. By comparing the estimated results with measured ones, the availability of the developed estimation method is discussed.<<ETX>>

A Novel Multi-Service Simultaneous Reception by Sharing Diversity Branches

In this paper, we propose a new concept of receiver structure with diversity reception technique to realize multi-service simultaneous reception, which shares diversity branches between receiving communication services. In the proposed receiver structure, each diversity branch selects the receiving services dynamically according to channel states, and each communication service is always selected by at least one branch to realize multi-service simultaneous reception. A basic algorithm is also described to select combinations of a diversity branch and a receiving communication service. The total number of branches decreases and the effective number of branches per communication service increases, by sharing the branches between communication services in the proposed receiver. Simulation results are shown that the proposed diversity receiver achieves both complexity reduction and performance improvement.

Channel Tracking with Zero Padding Scheme for STBC-OFDM System under Fast Fading Environment

An inter-vehicle communication system is highly advantageous for driving safety support systems, such as collision avoidance systems at intersections. In an inter-vehicle communication system, a channel-tracking scheme is essential to achieve reliable wireless communication under the fast fading environment caused by surrounding vehicles. For coherent detection, decision feedback is a well-known channel-tracking scheme. In this scheme, replica signals are generated and channel estimation is performed by using the replica signals. However, because channel estimation performance depends on the signal-to-noise (SNR) at symbol time, decision feedback errors occur by the lower SNR caused by fast fading. The feedback errors degrade the transmission performance significantly. In an orthogonal frequency division multiplexing (OFDM) system, the time domain 0-padding scheme is a well-known channel estimation technique. Although better channel tracking performance is expected by applying the 0-padding scheme, the tracking performance is degraded when employing guard-bands in the OFDM system. In this paper, we propose an improved time domain 0-padding scheme for an STBC-OFDM system employing guard-bands based on the IEEE802.11p standard for inter-vehicle communication, and show the improved performance through computer simulations.

An adaptive array for multi-carrier transmission

The authors have proposed a novel algorithm for an adaptive array that is suitable for the multi-carrier transmission. It has already been confirmed that multi-carrier waves can be suppressed by the adaptive array in the multi-carrier transmission system (Fujimoto et al.). In this paper it is shown through computer simulation that not only the multipath waves but also the co-channel interference waves can be suppressed by the adaptive array.