Hidetoshi Mishima

Inter-Carrier Interference Compensation for Zero Padding OFDM

Zero Padded (ZP)-OFDM has attracted a lot of attention as an efficient technique to improve the performance in severe frequency selective channels, and many works were devoted to the equalization methods of ZP-OFDM in static channel models. In this paper, we propose the ICI compensation method corresponding to ZP-OFDM in the time and frequency selective channel. In the proposed method, the channel variation within one OFDM symbol is assumed to be linear to reduce the computational complexity. Simulation results show that the proposed method improves the performance in the frequency and time selective channels.

Pilot-Assisted Channel Estimation for OFDM Systems in Time-Varying Multipath Channels

In this paper, a novel channel estimation technique is investigated to improve performance of pilot-aided mobile OFDM systems in time-varying multipath channels. The proposed method utilizes band dividing filters and Discrete Fourier Transforms (DFT) to separate and suppress aliases from desired signal. The aliases are detected by using the property of asymmetric channel power distribution. The simulation results demonstrate the robustness of the proposed method in time-varying multipath fading channels.

Cross detection method and its improved effect in BER for DAB diversity receiver

Broadcasting receivers with receiving function for digital radio service have been developed recently in the world. Especially in these receivers, DAB is widely deployed as digital radio broadcasting standards in many countries caused by the simplified digital demodulation architecture on receiver equipment. Though in DAB system, DQPSK is specified as modulation scheme, it has a general problem of deteriorating symbol error rate compared to that of synchronous detection. This is caused that demodulation method for DQPSK must be operated by using both noised received signal and noised delayed signal. Therefore, we propose a new noise reduction method using space diversity for decreasing noise effect. This method generates criterion symbol simply by referring some received signals in each antenna element, and also calculate phase difference between received signal and past received signal on another antenna element with depending on the phase shift of criterion symbol. Then DAB diversity receiver can obtain the advantageous effect in BER improvement effect by combining both conventional detected signals and additional generated signals as mentioned above. In this paper, we show that our proposal scheme can achieve the improved effect of required Eb/N0 of 0.2-0.5 dB on BER=10-3, in spite of simple additional receiver equipment.

A Study of Scalable Image Coding for Digital Video Disk.

MPEG2をベースにしたディジタルビデオディスクの画像符号化方式として, 良好な早送り再生が可能な階層符号化の検討をシミュレーションにより行った.本稿では提案方式の検討の概要と良好な早送りの実現を可能としたデータ処理手法について述べる.