Kazuhiro Okanoue

High track density magneto-optical recording using a crosstalk canceler

High track density magneto-optical recording, using a crosstalk canceller which eliminates crosstalk from two adjacent tracks, has been developed. By this recording method, both land area and groove area can be used for data storage tracks, and twice the track density, cornpared with the conventional method, has been achieved. Applying this crosstalk canceller also realizes intersymbol interference compensation.

New MLSE receiver free from sample timing and input level controls

A new maximum likelihood sequence estimator (MLSE) receiver which is tolerant of both aberrations in sample timing and variations in amplitude is presented. In the proposed receiver, input signals are represented in polar coordinates, and fractionally sampled signals are fed to the MLSE. These two features make it possible to greatly reduce control mechanisms without performance degradation. The performance of the receiver is evaluated both in computer simulations and in experiments in US time division multiple access (TDMA) cellular environments, and it is shown that under conditions of 65-dB amplitude variations it successfully achieves less than 3% bit error rate (BER) without controlling either input level or sample timing.

Seamless networked mobile computing realized by wireless Internet access

This paper gives a solution for a seamless network platform which brings flexible network connectivity into the mobile computing world. Areas being studied include future communication architecture, IP mobility support, flexible accessible radio with low power RF devices, programmable modems and software oriented MAC technologies. We discuss how to harmonize network-layer mobility and the wireless network to realize the seamless network, and especially in the radio modem we point out the key elements required in the adaptable modem, in order for flexible access to different wireless infrastructures. The practical mobile host architecture and the developed mobile computing network system are also described.

Reduced complexity maximum likelihood estimator for high speed wireless access-TCS-MLSCE

This paper proposes a received signal estimator with excellent compensation capability against multipath distortion, referred to the estimator as tap coefficient shift maximum likelihood symbol candidate estimator (TCS-MLSCE). The estimator adopts symbol-by-symbol maximum likelihood criterion based on both symbol candidates and decision feedback data for pre- and post-cursor estimates, respectively. It is shown that the structure can dramatically reduce the hardware size and the amount of calculation, compared to those of maximum likelihood sequence type estimators. By introducing a tap coefficient shift algorithm, the estimator improves the performance, especially in a case of a non-minimum phase. In the simulation, the degradation against DDFSE ranges less than 2.5 dB of E/sub b//E/sub 0/.