Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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A study on the mitigation of the influence of ADC nonlinearity in an OFDM receiver

M. Sawada, H. Okada, T. Yamazato, M. Katayama

Symposium on Information Theory and Its Applications (SITA) Vol. 1 page： 143-146 2005.11

Channel Coding for M-Ary Coherent-State Signals with Signal Constellations in Consideration of Signal States

T. Otake, H. Okada, T. Yamazato, K. Yamazaki, and M. Katayama

Symposium on Information Theory and Its Applications (SITA) Vol. 1 page： 203-206 2005.11

Language：Japanese

In quantum communication systems, the optimum detection process for M-ary PSK coherent-state signals which minimizes symbol error probability is Square-root Measurement(SRM). To minimize the bit error probability of the M-ary PSK coherent-state signals, it is effective to consider the allocation of the code words to the signals. In this paper, we show that the average bit error probability for such coded signals improves more than that of the uncoded signals which have the same information rate as the coded signals.

The Faculty Inventory for Student Involvement in Web-Enhanced Learning -The Online Survey of WebCT Users-

T. Yamazato, T. Nakai, H. Nakajima, H. Okada, M. Omura

3rd WebCT Conference page： 73-77 2005.11

Performance evaluation of route coding scheme in wireless multi-hop networks Reviewed

Okada H.

IEEE Vehicular Technology Conference Vol. 61 ( 5 ) page： 3092 - 3096 2005.10

Outage Probability of a Macro and Micro MIMO Diversity Scheme in an Indoor Fading and Shadowing Environment Reviewed

R. Uchida, H. Okada, T. Yamazato, M. Katayama

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E88-A ( 10 ) page： 2945-2951 2005.10

Language：English Publishing type：Research paper (scientific journal)

In this manuscript, a layered macro / micro diversity scheme is introduced at the receiver side of a MIMO STBC wireless control system under fading and shadowing environment. The combination of the outputs of micro diversity is based on soft-decision values, while the macro diversity branches are combined based on hard decision values. As a measure of the reliability of the system, the outage probability of frame-error rate is employed. The performance of the proposed system is analytically and numerically evaluated and the impact of the macro diversity in the outage probability is clarified.

Successive Interference Cancellation for Hierarchical Parallel Optical Wireless Communication Systems Reviewed

H. Okada, K. Masuda, T. Yamazato, M. Katayama

The 11th Asia-Pacific Conference on Communications page： 788-792 2005.10

Language：English

A parallel optical wireless communication system using two-dimensional LED array (2D LED array) and two-dimensional image sensor (2D image sensor) was proposed for the visible light communication systems. In this system, each LED of the 2D LED array is individually modulated, and the 2D image sensor recognizes each LED modulated data. However, the received data pattern will be degraded due to reduction of pixel size and/or defocussing of the LED data pattern. This phenomenon corresponds to the degradation of high spatial frequency components of the received data pattern. To overcome, we employ a hierarchical transmission scheme at a transmitter and a successive interference cancellation at a receiver. By allocating high priority data to low frequency components and low priority data to high frequency components, the reception of high priority data can be guaranteed. We also attempt to apply interference cancellation to overcome the degradation of high spatial frequency components of the received data pattern. By evaluating the bit error rate, we clarify the effect of the proposed system.

A Note on the Simple Regenerative Repeating Process for Communication Satellite

T. Yamazato, A. Ogawa

Technical Report of IEICE Vol. SAT2005-21 page： 27-32 2005.10

Language：English

We have been working on a relay process of communication satellite. We omit the regenerative process at the satellite. Only routing and other necessary operation are performed at satellite. Simple configuration and signal processing may promise robust and long-lasting operations in space. We call it simple regenerating repeater. However, an issue is how to realize the reliable transmission even if we omit the error correcting and detecting process at the satellite. To overcome this issue, we propose to place the error detection code prior to QAM mapping. Using the status of error detector, it is possible to give accuracy to the received signal so we can improve the performance by soft decoding. The FPGA experimental boards of the system are also introduced

Characterization of a simplified regenerative repeater for broadband satellite communications

H. Kuwamura, A. Ogawa, T. Yamazato

Technical Report of IEICE Vol. SAT2005-22 page： 33-35 2005.10

Outage probability of a macro and micro MIMO diversity scheme in an indoor fading and shadowing environment Reviewed

R Uchida, H Okada, T Yamazato, M Katayama

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E88A ( 10 ) page： 2945 - 2951 2005.10

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

In this manuscript, a layered macro/micro diversity scheme is introduced at the receiver side of a MIMO STBC wireless control system under fading and shadowing environment. The combination of the outputs of micro diversity is based on soft-decision values, while the macro diversity branches are combined based on hard decision values. As a measure of the reliability of the system, the outage probability of frame-error rate is employed. The performance of the proposed system is analytically and numerically evaluated and the impact of the macro diversity in the outage probability is clarified.

DOI： 10.1093/ietfec/e88-a.10.2945

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A-21-5 PERFORMANCE ANALYSIS OF A MULTI-ROUTE PACKET COMBINING SCHEME IN SENSOR NETWORKS Reviewed

Nakao Kouji, Yamazato Takaya, Okada Hiraku, Hirayama Yasuhiro, Katayama Masaaki

Proceedings of the Society Conference of IEICE Vol. 2005 page： 274 2005.9

A MIMO System with Relay Terminals for Reliable Wireless Control Reviewed

R. Uchida, H. Okada, T. Yamazato, M. Katayama

The 16th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communication page： - 2005.9

Language：English

In this manuscript, wireless communication system for reliable wireless control of industrial machines in indoor environment is considered. In indoor environment, transmitted signal fluctuates due to fading and shadowing. To combat the fading and shadowing, macro / micro spatial diversity can be used as an effective countermeasure. In this manuscript, macro / micro diversity is achieved by multiple wireless relay terminals, which is convenient in setting and moving the macro diversity branches. In the proposed scheme, channel between the transmitter and the receiver through relay terminals is considered as a MIMO channel and separation of the signals re-transmitted from the relay terminals is not required. This feature makes it possible to have higher order diversity without the cost of bandwidth inefficiency. In numerical examples, the performance of the proposed scheme is evaluated by average frame-error rate and outage probability of frame-error rate. With two relay terminals, the diversity gain of the proposed scheme is about 5-6 dB, which is 1 dB higher than that of conventional macroscopic diversity.

A Simple Regenerative Repeating Process for Broadband Communication Satellite Reviewed

T. Yamazato, A. Ogawa

23rd AIAA International Communications Satellite Systems Conference (ICSSC-2005) Vol. MOD-1-1 page： - 2005.9

Language：English

In this paper, we focus on relay process of broadband communication satellite. We omit the demodulation, error decoding and re-encoding process at the satellite. Just store the received signal as it is and then forward it to the destination in which the information is extracted from the header. We discuss the issue of analog-to-digital converter for this relay process. For given quantization level, reduction of signal accuracy can improve the transmission rate as we can adopt higher order of QAM. However, the degradation occurred due to the reduction of available quantized bit for accuracy. To overcome this issue, we propose to place the error detection code prior to QAM mapping. Using the status of error detector, it is possible to give an accuracy to the received signal so we can improve the performance by soft decoding.

Performance Analysis of a Multi-Route Packet Combining Sheme in Sensor Networks

K. Nakao, Y. Hirayama, T. Yamazato, H. Okada, and M. Katayama

Communications Society Conference of IEICE Vol. A-21-5 page： 274 2005.9

A New Coded QAM Modulation Scheme for Broadband Satellite Communication Reviewed

T. Yamazato, T. Yamaoka, H. Okada, M. Katayama, A. Ogawa

23rd AIAA International Communications Satellite Systems Conference (ICSSC-2005) Vol. MOD-3-3 page： - 2005.9

Language：English

In this paper, we propose a new multi-rate coded QAM for broadband satellite communication system. The overall coding rate is (m?2)/2 and Turbo code is adopted. The mapping is similar to bit-interleaved coded modulation (BICM) systems; unlike BICM mapping, we only assign four of Turbo coded bits. This brings a set-partitioning. We also consider the effect of quantization bits. Actually we try to realize high-order QAM by using the available quantization bits, which reduces the signal accuracy so the performance may degrade. As results, our proposed scheme achieve good performance even when the available quantization bits are less.

Effects of Error Rate and Transmission Rate on the Performance of Wireless Control Systems

R. Uchida, H. Okada, T. Yamazato, and M. Katayama

Communications Society Conference of IEICE Vol. B-5-156 page： 556 2005.9

A Study on ARQ Schemes of Multiple Route Coding for Wireless Multihop Networks

H. Okada, M. Saito, T. Wada, K. Ohuchi, T. Yamazato, M. Katayama

Communications Society Conference of IEICE Vol. B-5-149 page： 549 2005.9

A Study on Effects of Variations of Transmitter LED's Luminance for Hierarchical Coding in Parallel Optical Wireless Communication Systems

K. Masuda, T. Yamazato, H. Okada, and M. Katayama

Communications Society Conference of IEICE Vol. B-8-17 page： 209 2005.9

On the Second-order Statistics of the Channel Parameters for BFDM/OQAM Systems Reviewed

B. Mongol, T. Yamazato, H. Okada, M. Katayama

2nd International Symposium on Wireless Communication Systems page： 534-538 2005.9

Language：English

Recently, there has been increased interest in using multicarrier systems in rapidly time-varying multipath environment. Biorthogonal Frequency Division Multiplexing based on Offset QAM (BFDM/OQAM) is an attractive modulation method since it allows time-frequency well-localized pulses even at critical sampling (i.e. maximum spectral ef ciency). BFDM/OQAM system is naturally strong against intersymbol and intercarrier interference (ISI/ICI). However, for further improvement of the system a study on the channel statistics is needed. In this paper we analytically examine the channel parameters for BFDM/OQAM and derive their second-order statistics.

A New Coded QAM Modulation Scheme for Broadband Satellite Communication Reviewed

T. Yamazato, T. Yamaoka, H. Okada, M. Katayama, A. Ogawa

23rd AIAA International Communications Satellite Systems Conference (ICSSC-2005) Vol. MOD-3-3 page： - 2005.9

Language：English

Influence of the Nonlinearity of the ADC in an OFDM Receiver Reviewed

M. Sawada, H. Okada, T. Yamazato, and M. Katayama

The 10th International OFDM-Workshop 2005 page： 220-224 2005.8

Language：English

This paper discusses the influence of the nonlinearity of an analog-to-digital converter (ADC) in an orthogonal frequency division multiplexing (OFDM) receiver. We evaluate a signal constellation and a bit error rate (BER) performance with the consideration of quantization errors and clippings. As a result, the trade off between the quantization error and the clipping and the optimum range for an ADC input amplitude are shown. In addition, it is shown that the peak to average power ratio (PAPR) of the signal is not a good measure of the BER performance, since the peaks occur only with very low probabilities.

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Papers - YAMAZATO Takaya