Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Foreword: Special section on information theory and its applications Reviewed

Morita H.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E89-A ( 10 ) page： 2457 - 2458 2006.10

A study on route selection metrics for the multiple-route packet combining scheme in wireless multihop networks Reviewed

Y. Hirayama, H. Okada, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. J89-B ( 10 ) page： 2047-2051 - 2051 2006.10

A-21-15 A Study on Fusion Schemes for Joint Decoding Using Correlation between Observed Data Sequences Reviewed

Okada Hiraku, Kobayashi Kentaro, Yamazato Takaya, Mase Kenichi

Proceedings of the Society Conference of IEICE Vol. 2006 page： 227 2006.9

A study on the reduction of the influence of the interference using ADC nonlinearity in an OFDM receiver

M. Sawada, T. Yamazato, M. Katayama

Communications Society Conference of IEICE Vol. B-17-5 page： 515 2006.9

A Correlation Tolerant Relaying Scheme for the Spatial Diversity with Multiple Transmit and Receive Antennas

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

Communications Society Conference of IEICE Vol. B-5-122 page： 482 2006.9

Channel Estimation for BFDM/OQAM System in Dispersive Time-Varying Channels Reviewed

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

International Symposium on Wireless Communication Systems page： - 2006.9

Language：English

Pulse-shaping OFDM is well-known that it performs well in a mobile environment comparing with conventional OFDM. However, in highly mobile environment intersymbol and intercarrier interferences (ISI/ICIs) increase and can no longer be neglected. These ISI/ICIs deteriorate the performance of the systems. Practically, proper channel equalization and estimation are needed for further improvement of the systems. In this paper, more general case, namely Biorthogonal Frequency Division System based on Offset QAM (BFDM/OQAM) is considered. We first derive analytical equations for the channel statistics. Further, we propose maximum-likelihood channel estimator and its low-complexity versions. The performance analysis shows that the estimators are robust against Doppler spread of the channels.

The Effect of Multipath Hybrid Routing Protocol in Multihop Cellular Networks Reviewed

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

The 17th Annual IEEE International Symposium on Personal Indoor and Mobile Radio Communication page： - 2006.9

Language：English

This paper examines multihop cellular networks. There are some issues in these networks, such as route loss due to topological change and packet errors due to wireless nodes relay. To overcome these issues, we use a multiple route coding scheme in which packets are transmitted on multiple routes from a user node to multiple base stations. This scheme can achieve a diversity gain by combining packets that are transmitted along multiple routes. Some challenges must be met to establish multiple routes for this scheme. In this paper, we propose a routing protocol for multiple route coding. The key idea of this proposed scheme is using a hybrid routing protocol. This can mitigate an increase in control packets and multiple disjoint routes can be constructed. We evaluate the performance of this proposed scheme.

Optical Wireless Communicaiton using LED Traffic Light and High-Speed Camera

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

Technical Report of IEICE Vol. SIP2006-58 page： 25-30 2006.7

Language：Japanese

LEDs are expected as lightning sources for next generation, and data transmission system using LEDs attract attention. In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. Further, if each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we propose hierarchical coding scheme based on 2D fast Haar wavelet transform.

A Mathematical Model of Noise in Narrowband Power-Line Communication Systems Reviewed

M. Katayama, T. Yamazato, H. Okada

IEEE Journal on Selected Areas in Communications Vol. 24 ( 7 ) page： 1267-1275. 2006.7

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

This manuscript introduces a mathematically tractable and accurate model of narrowband power-line noise based on experimental measurements. In this paper, the noise is expressed as a Gaussian process whose instantaneous variance is a periodic time function. With this assumption and representation, the cyclostationary features of power-line noise can be described in close form. The periodic function that represents the variance is then approximated with a small number of parameters. The noise waveform generated with this model shows good agreement with that of actually measured noise. Noise waveforms generated by different models are also compared to that of the proposed mode.

A mathematical model of noise in narrowband power line communication systems Reviewed

Masaaki Katayama, Takaya Yamazato, Hiraku Okada

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS Vol. 24 ( 7 ) page： 1267 - 1276 2006.7

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

This manuscript introduces a mathematically tractable and accurate model of narrowband power line noise based on experimental measurements. In this paper, the noise is expressed as a Gaussian process whose instantaneous variance is a periodic time function. With this assumption and representation, the cyclostationary features of power line noise can be described in close form. The periodic function that represents the variance is then approximated with a small number of parameters. The noise waveform generated with this model shows good agreement with that of actually measured noise. Noise waveforms generated by different models are also compared with that of the proposed model.

DOI： 10.1109/JSAC.2006.874408

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Peformance analysis of UWB Impulse Radar Receiver using Parallel IPCP Reviewed

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

IEICE Transaction on Communications Vol. J89-A ( 6 ) page： 544-556 2006.6

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

In this paper, we consider two novel inter-period correlation processing (IPCP) receivers for UWB impulse radar. The conventional IPCP receiver uses the signal periodicity of signals, so it avoids estimation of unknown parameters determined by the targets. However, its accuracy of measurement is poor because the interval of receiver outputs is restricted to a code length. We propose a parallel IPCP receiver to improve accuracy. When there are multiple targets, the conventional IPCP receiver needs multiple thresholds to detect. This results in complexity of the receiver. So, we propose a parallel differential IPCP receiver. We present the analysis of proposed receivers.

An Inter-Vehicle Two-Way Communication System

M. Masamura, H.Okada, S. Makido, T. Yamazato, M. Katayama

4th Ad-hoc Network Workshop Vol. 4-21 - 4-24 page： - 2006.6

Language：Japanese

We propose an inter-vehicle two-way communication system for safety applications. The proposed system synchronizes with transmission timings mong cars by one-direction token transmissions in a linear network. The token contains the frame information about transmission/reception phase. The token transmission interval is set so that adjacent reception cars do not affect interference from other cars. Moreover, multiple channels are used in order to make the same transmission delays despite of their transmission directions and reduce them. This system can adapt changes of the network structure by allocating channels dynamically for every token.

An Analysis on Influence of Transmit and Receive Correlations on Performance of the MIMO System with Relay Terminals

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

Technical Report of IEICE Vol. RCS2006-46 page： 65-70 2006.6

Language：Japanese

In this manuscript, a spatial diversity scheme with multiple transmit and receive antennas and relay terminals for indoor factory fading/shadowing environment is considered. The scheme uses multiple transmit and receive antennas and relay terminals to provide diversity gain against the fading and shadowing. However, if the separations of antennas at a transmitter or a receiver are not enough, then the signals of the diversity branches may be influenced by transmit or receive correlation. This manuscript shows the analytical and numerical results of the effect of the transmit and receive correlations on the performance of the spatial diversi ty scheme.

Performance Analysis of ARQ Scheme for Multi-route Coding in Wireless Multi-hop Networks Reviewed

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

IEEE Vehicular Technology Conference (VTC) page： - 2006.5

Language：English

For reduction in bit errors on wireless channels, we proposed the multi-route coding scheme on multiple routes for wireless multi-hop networks. In this paper, we introduce ARQ to the multi-route coding. In the multi-route coding, the destination node combines and decodes sub packets which are encoded and divided by the source node. The intermediate node relays a sub packet, that is, only a part of a packet. Therefore, the intermediate node cannot detect packet errors, and only the destination node can do after combining and decoding sub packets. We propose the ARQ scheme between the source node and the destination node. We analyze the proposed ARQ scheme and evaluate the throughput performance.

Iterative channel decoding scheme using the correlation of transmitted information sequences - Extension to the case of more than two sensor nodes -

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

Technical Report of IEICE Vol. SN2006-32 page： 91-97 2006.5

Language：Japanese

In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node is correlated. The observation data is encoded and transmitted from each sensor node. Such observation data are collected at a fusion center. In this paper, we consider a channel decoding scheme using the correlation of observation data. Related works on the encoding and decoding scheme using the correlation of observation data are for the case of two correlated sources. An approach for more than two sources is still not presented. In this paper, we extend the iterative channel decoding scheme using the correlation of transmitted information sequences to the case of more than two sensor nodes. A problem in the extension to the case of more than two sensor nodes is how to use the information of correlation obtained from other sequences. Specifically, it is needed to use them with weighting to minimize the bit error rate. In this paper, we find the optimum weight that minimizes the BER from the analytical formula in the case of uncoded BPSK and apply it to the case of Turbo code.

Throughput Evaluation of ARQ Scheme for Multi-route Coding in Wireless Multi-hop Networks Reviewed

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

IEEE Vehicular Technology Conference (VTC) page： 668-672 2006.5

Language：English

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

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

DENSO TECHNICAL REVIEW Vol. 11 ( 1 ) page： 115-120 2006.5

Language：Japanese

An orthogonal frequency division multiplexing (OFDM) scheme, with highly spectrum efficiency and robustness against frequency selective fading, is applied to IEEE802.11a/g for high-speed wireless local area network (LAN) systems and digital terrestrial television broadcasting (DTTB) systems. The OFDM signal has large fluctuation in its amplitude, large dynamic range and high linearity are required for its transmitter and receiver. In the receiver, the Bit Error Rate (BER) performance is degraded by analog-to-digital converter (ADC) nonlinearity. We propose a new scheme to mitigate the influence of ADC nonlinearity in an OFDM receiver. In the proposed receiver, the weight for the soft Viterbi decoder is controlled based on the ADC output amplitude. We evaluate the BER performance for the proposed receiver when the control errors occur in the AGC amplifier. As a result, the effect of the proposed receiver on the BER performance is shown.

Multi-route Coding in Wireless Multi-hop Networks Reviewed

H. Okada, N. Nakagawa, T. Wada, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. E89-B ( 5 ) page： 1620-1626 2006.5

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

Wireless multi-hop networks have drawn much attention for the future generation mobile communication systems. These networks can establish multiple routes from a source node to a destination node because of flexible construction of network topology. The transmission by multiple routes has enough capability to achieve reliable communication because we can expect to obtain diversity gain by multiple routes. In this paper, we propose the multi-route coding scheme. At first, we discuss a channel model in multi-hop networks employing regenerative relay, which we named the virtual channel model. By using the virtual channel model, a packet is encoded on multiple routes as follows; a bit sequence of a packet is encoded and divided into subpackets, and each subpacket is transmitted on each route. We evaluate its packet error rate performance, and clarify effectiveness of the proposed scheme. In general, we should face degradation of a route condition such as the case when a subpacket does not reach a destination node. Hence, we have to consider the influence of subpacket loss. We also investigate it, and show tolerance of the proposed scheme over that.

A study on position estimation method based on MAP estimation for multiple targets in car radar networks

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

Technical Report of IEICE Vol. ITS2006-3 page： 39402 2006.5

Language：Japanese

In this paper, we consider radar networks for cars. The radar networks are the networks built with multiple radars. Using measured ranges provided by radars, target positions are estimated. The measured ranges include measurement errors. The estimation method of the target positions using a MAP stimation is an optimum method. However, when the number of targets increases, the MAP estimation method becomes complex. So we introduce the simpler methods based on the MAP estimation method. The performance is evaluated by computer simulations.

Cooperative transmission scheme using coded FSK

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

Technical Report of IEICE Vol. SN2006-28 page： 67-72 2006.5

Language：Japanese

In sensor networks, many sensor nodes are distributed. The observation data are collected at a fusion center. They are transmitted to a fusion center by direct or multihop transmission. In this paper, we consider the situation that the transmission by those ways is not possible (e.g. a helicopter collects the data). We realize the transmission by a cooperative transmission among the nodes. An approach proposed for cooperative transmission is assumed coherent propagation or multi-channel, or applied to only a few nodes. In this paper, we propose a scheme to achieve the cooperative co-channel transmission only coding by multiplying a random phase per symbol.

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Papers - YAMAZATO Takaya