Noritaka Deguchi

Detection of a metal obstacle in wireless power transfer via magnetic resonance

Wireless power transfer via magnetic resonance is a technique to realize higher transmission efficiency over a distance of several meters. However, if there are obstacles to the transmission coil, it is difficult to maintain high transmission efficiency. This is caused by variation of matching frequency for the transmission coil brought about by a metal obstacle. This paper evaluates the effect of the transmission performance via magnetic resonance for wireless power transfer when metal obstacles approach the transmission coil. In addition, this paper proposes a procedure for detecting metal obstacles via magnetic resonance.

Group-Wise Scrambling Diversity for Broadcast and Multicast Services in OFDM Cellular System

Broadcast and multicast services in OFDM cellular system provide the ability to transmit the same information from multiple base stations. For the services, cyclic delay diversity (CDD) is one of the promising diversity schemes, since it can be easily applied to any number of base stations. However, there is a problem in that CDD increases frequency selectivity and makes channel estimation more difficult. In this paper, we propose a new diversity scheme that can overcome the problem of CDD. In the proposed scheme, subcarriers are divided into several subcarrier-groups. By rotating phase of each subcarrier-group independently among base stations, the frequency selectivity of the whole band is increased as in the case of CDD. On the other hand, unlike in the case of CDD, the frequency selectivity within each subcarrier-group is not changed. Utilizing this property, channel estimation carried out within each subcarrier-group can avoid the problem of CDD.

Time Domain Loop Interference Channel Estimation and Cancellation for Mobile MIMO Wireless Relays

This paper presents a novel Time Domain (TD) based Multiple-Input Multiple Output (MIMO) implementation of the Expectation-Maximization (EM) algorithm. The algorithm is able to achieve Maximum Likelihood (ML) performance with reduced complexity. Results show how performance superior to the Recursive Least Square (RLS) algorithm, in terms of both convergence and residual Mean Squared Error (MSE), can be achieved with comparable complexity. The channel estimation technique is combined with a new TD based MIMO loop interference cancellation system for wireless relays. Performance results for a 2×2 Downlink (DL) Long Term Evolution (LTE) system are provided for both single-stream transmission with Maximal Ratio Combining (MRC) and dual-stream transmission with Spatial Multiplexing (SM). Results are shown at both low mobility and high mobility, with our EM algorithm showing up to a 2dB improvement in the Error Vector Magnitude (EVM) in the MRC case at 60kmph compared to the RLS.

A practical and cost-effective cyclic pulse synchronization system using IEEE 802.11 wireless LAN

Timing synchronization is important for collaborating machines. For various reasons concerning practicability, some machines cannot have cables to synchronize them. To synchronize wirelessly connected machines, this paper proposes a practical and cost-effective cyclic pulse synchronization system. The proposed system consists of a master machine with an IEEE 802.11 wireless LAN AP and slave machines with wireless LAN STAs. The master machine outputs a cyclic pulse to the AP. Then the STAs can reproduce synchronized cyclic pulses for the slave machines. Thus the machines can synchronize their work timing using the cyclic pulses. All functions to synchronize the pulses are implemented in a wireless LAN chip as user software applications without additional hardware. We evaluated the pulse synchronization precision of our system in the case of the peak network load. The proposed system achieves approximately 200 μs precision for the maximum pulse edge delay of STA output pulse to AP input pulse.