Katsushi Sanda

Header reduction to increase the throughput in decentralized TDMA-based vehicular networks

In the decentralized-TDMA (D-TDMA) protocol the terminals select a free slot based on the frame information (FI) included in each packet to be transmitted. However, the FI constitutes a large portion of the packet which seriously compromised the throughput of the D-TDMA. We are proposing a technique for increasing the throughput by reducing the length of the FI without jeopardizing the packet success rate. Our technique, which is based on FI redundancies, lets the terminals transmit the relevant information when necessary. A computer simulation was conducted for an urban environment in which vehicles are moving. The simulation results show that the proposed technique significantly increases the throughput without degrading the quality of the D-TDMA protocol.

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.

An adaptive array direction control LSI for mobile digital HDTV receivers

This work presents a multi-antenna diversity LSI that enables the mobile reception of digital HDTV. A unique algorithm of four-branch combination with three-band division method drastically improves the performance of mobile reception, especially in high-speed environments. The rate of reception is 97% field-testing result in Japan.

A Novel MIMO-STBC Scheme for Inter-Vehicle Communications at Intersection

This paper proposes an inter-vehicle communication (IVC) scheme for safety driving support systems that transmits collision avoidance warnings at intersections. In order to realize high communication reliability, a transmission scheme based on multiple-input multiple-output (MIMO) with space-time block coding (STBC) is proposed. A key transmission feature of MIMO systems is determined by radio wave propagation. Therefore, the radio wave propagation at an intersection is analyzed by computer simulations using the ray-tracing method. In addition, this paper verifies the effectiveness of the proposed scheme using the propagation characteristics in computer simulations

A multiplexed transmission scheme with unequal error protection on MIMO frequency selective channels

Wireless transmissions with high data rate and high reliability are very demanding. We have focused on an Unequal Error Protection (UEP) using different modulation schemes. The UEP in our study means the multiplexed transmission where multiple modulations are transmitted simultaneously. The receive data bits with guaranteed reliability at each Eb / N0 can be obtained at the receiver. To achieve this UEP property, we have used the multiplexed transmission using the CDM (Code Division Multiplex). In order to increase the data rate and the reliability, we have also used the MIMO SC-FDE (Single Carrier - Frequency Domain Equalization) rather than MIMO OFDM (Orthogonal Frequency Division Multiplex), because the SC-FDE has the lower PAPR than the OFDM.

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.

Reception Quality of Terrestrial Digital Broadcasting Signals while Traveling at High Speed

To receive terrestrial digital broadcasting signals in an automobile, we previously proposed a method for controling the antenna directional pattern and demonstrated the effectiveness of the method by field experiment in an urban area. We have now investigated the reception quality during high-speed traveling and clarified the performance of doppler-shift compensation in the proposed method. A field experiment demonstrated that high-definition television (HDTV) signals can be received in an automobile traveling at about 100 km an hour.