Hironobu Hatamoto

Loosely Coupled Inductive Wireless Power Transfer Systems with Class-E Transmitter and Multiple Receivers

This paper presents a design procedure for dc-to-dc WPT systems with multiple receivers. For achieving high power-transfer efficiency, the class-E inverter and the class-E rectifiers are applied to the transmitter and the receivers, respectively. By using the numerical design algorithm, we can obtain the accurate component values for achieving the class-E ZVS/ZDS conditions and the impedance matching of the secondary side without system analyses. Additionally, the inductor designs are discussed from the magnetic-component design knowledge [13]. The WPT system with five receivers was designed and circuit experiments were carried out. The power-transfer efficiency was 84.4 % with 5.7 W output power in total.

An evaluation of transmission performance for wireless harness systems using propagation models in an automobile engine compartment

In this paper, transmission performance for wireless harness systems is evaluated using propagation models which include pathloss and power delay profile in an automobile engine compartment. In the wireless harness system in vehicles, it is assumed that an electronic control unit has a wireless access point (AP) and each sensor has a wireless station terminal (ST). First, pathloss and power delay profile models are analyzed using measured propagation data of the scattering parameter in the Toyota Priuss engine room which size is 0.9 × 1.2 × 0.6 m on condition that the vehicles engine is turned off. Second, performance results of channel capacity and throughput, where on-off keying based signals are transmitted between the AP and each ST, are evaluated using analyzed propagation models. Simulation results confirm that high channel capacity and throughput performance are satisfied when transmit power is less than 0 dBm in 2-3 GHz on condition that positions of APs antennas are fixed, positions of STs are uniformly set in the engine space, and wireless channels are quasi-static.

A Study on Power Delay Profile Measurement Using IEEE 802.11g Based Long Preamble Signals for WLAN Systems at 2.4 GHz Band

This paper proposes a measurement scheme of power delay profiles using IEEE 802.11g based wireless packets at 2.4 GHz band. In the proposed scheme, at first, a signal analyzer which can save the received Ich and Qch signal receive the OFDM based packets from wireless access point to mobile terminal. Secondly, positions of long preambles in the received IQ data are detected in the cross correlation process using a long preamble signal which is known between a transmitter and a receiver. Thirdly, the power delay profile is calculated by averaging of channel impulse responses which are estimated from received long preamble signals. Computer simulations confirm that the proposed scheme can be expected to achieve almost the same performance with PN sequence based measurement scheme.

Implementation of OFDM baseband transceiver with dynamic spectrum access for cognitive radio systems

VLSI architecture for OFDM baseband transceiver is developed, which is dedicated to cognitive radio systems. To facilitate dynamic spectrum access, this transceiver architecture employs a specialized FFT/IFFT module and a mapping/demapping module. Efficient mechanisms to omit input/ output of unused subcarriers are introduced. Also, calculation of spectrum intensity for subcarrier level carrier sensing is successfully integrated to the FFT module. Whole transmitter/ receiver modules are implemented by keeping compatibility with IEEE 802.11g. A prototype system is constructed by using Xilinx Virtex-II FPGA, which can transmit video sequence in real time.

VLSI design of OFDM baseband transceiver with dynamic spectrum access

The VLSI design of OFDM baseband transceiver is described, which is dedicated to cognitive radio systems. To facilitate dynamic spectrum accessing, this receiver architecture employs a specialized FFT module and a mapping/demapping module. Efficient mechanisms to omit input/output of unused subrcarriers are introduced. Also, calculation of spectrum intensity for subcarrier level carrier sensing is successfully integrated to the FFT module. Whole transmitter/receiver modules are implemented by maintaining compatibility with IEEE 802.11g. Implementation results show that the proposed architecture can process OFDM symbols in 60 MHz operation.

Relay-Assisted Re-Transmission Scheme based on Mutual Information for Wireless Mesh Networks

This paper proposes a relay-assisted re-transmission scheme based on mutual information for wireless mesh networks. In the proposed scheme, re-transmission is done not from the source node but from the relay node, and minimal amount of spectrum corresponding to the remaining uncertainty for the data sequence is re-transmitted, where the number of spectrum components to be fed back is determined based on expected mutual information after re-transmission. Moreover, to directly convert reduction of feedback spectrum to spectrum efficiency improvement in carrier sense multiple access with collision avoidance (CSMA/CA) introduced systems, the re-transmitted spectrum is mapped on whole the bandwidth with equal spacing, thereby the time duration for the re-transmission is reduced. Computer simulation confirms that the proposed scheme can achieve much higher system throughput efficiency especially than the conventional two-hop transmission schemes.

A study on cooperative multiple relay transmission scheme for broadband wireless mesh networks

This paper proposes a cooperative multiple relay transmission scheme for broadband wireless mesh networks in which the number of hops is limited to two. In the proposed scheme, a source node multicasts a signal to some relay nodes that locate sufficiently close to the source node. Then each relay node simultaneously transfers a different part of spectrum in a cooperative manner. Because only a part of spectrum is transferred from each relay node to the destination node, we can increase the distance from relay to destination nodes longer than that between source and relay nodes. Moreover, when more number of relay nodes are employed, we can increase the relay-to-destination distance because the relayed signal bandwidth can be reduced. This means that the proposed scheme has potential to keep high throughput by appropriately selecting a certain number of relay nodes in a mesh network even though the source-to-destination distance is relatively long. Computer simulation confirms that the proposed scheme can achieve high throughput while keeping the transmitted power for each node low.