Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/GCCE59613.2023.10315678

researchmap

Other Link： https://dblp.uni-trier.de/db/conf/gcce/gcce2023.html#TanushiTDU23

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2022COL0020

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1587/comex.2022col0020

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/GCCE56475.2022.10014227

researchmap

Other Link： https://dblp.uni-trier.de/db/conf/gcce/gcce2022.html#TokuiTDU22

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2022xbl0028

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2022xbl0001

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ISCIT52804.2021.9590603

researchmap

Other Link： https://dblp.uni-trier.de/db/conf/iscit/iscit2021.html#FukuyamaTDU21

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2021etl0007

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2021etl0020

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2021xbl0050

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2020xbl0003

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/GCCE46687.2019.9015428

researchmap

Other Link： https://dblp.uni-trier.de/db/conf/gcce/gcce2019.html#KameiTDU19

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper analyzes optical radio channel propagation characteristics by means of experimental measurement. The channel with an LED and a PD provided by the outstanding technologies co. ltd., is defined as an optical radio channel, and its delay profile is measured by NI-USRPs. As a result, small delayed paths are detected due to the LED or the PD in use. The delay profile is evaluated in a system with single carrier modulation where the frequency domain equalization is applied, in terms of the bit error rate (BER). The transmission performance is about 2dB degraded due to the small delayed paths.

Web of Science

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.15344/2456-4451/2019/143

researchmap

Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu  

DOI： 10.11527/jceeek.2014.0_260

CiNii Article

researchmap

Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu  

DOI： 10.11527/jceeek.2014.0_257

CiNii Article

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper shows performance of a transmit beamforming with DOA estimation in fast time selective fading channels with angle of arrival spread. The performance is confirmed by simulation where carrier frequency is assumed to be 20GHz and a linear array antenna is introduced. The unitary ESPRIT is applied for the DOA estimation. The beamfoming gain can be kept high as far as the maximum Doppler frequency f(D) is less than 10(4) in the fading channel.

Web of Science

researchmap

Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu  

DOI： 10.11527/jceeek.2013.0_308

CiNii Article

researchmap

Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu  

DOI： 10.11527/jceeek.2013.0_307

CiNii Article

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Service area upgrading and expanding is expected in current and future cellular systems. Since residential areas on a hilly and/or slope terrain are spreading in the outskirts of cities in Japan, the correction for the urban mobile propagation loss formula becomes one of the important issues in radio link and cell layout designs in those areas, especially within 1km distance from a base station. This paper introduces an example of correction formula for the slope terrain area based on an experimental study of mobile path loss prediction. The result shows the path loss at the objective point can be estimated by the urban mobile path loss and the correction value according to the factor expressed by the elevation angle from the base station antenna top. Although the average slope angle is only used as a parameter in the conventional correction for the slope terrain area with at least 5 to 10km length, the result means it is not enough for the correction to the area within 1km distance from a base station. ©2010 IEEE.

DOI： 10.1109/VETECF.2010.5594354

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes an adaptive soft clipping method for spectrum sharing OFDMA systems. The proposed method controls in-band and out-of-band distortion power by changing the nonlinearity parameter of soft clipping. The simulation results show that the proposed method can control the distortion power by 10 dB for a practical power amplifier. The results also show that a low-peak OFDMA transmitter can be realize with reasonable computational complexity because iterative processing for peak power reduction is unnecessary.

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

As one of the effective way to overcome the digital divide issue in the lightly populated area, the BWA (Broadband Wireless Access) system is expected and field trials have been conducted extensively in Japan. This paper introduces the results of BWA field experiments conducted in a typical intermediate and mountainous area in Japan. In the BWA network, WiMAX units are used as relay stations and R-LAN units are structuring the meshed network. The result shows that the study of effective frequency utilization is important to realize the multi-hop relaying. It is also suggested that the multiple channel transmission in the meshed network needs the topological node allocation study to reduce delay affects.

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

This paper proposes a novel turbo equalization method, called SC/Simplified-MMSE (S-MMSE), for multiple-input multiple-output (MIMO) channel signal transmission. Our method, which deals with residual inter sub stream interference as their average over a frame, achieves excellent error performance at small computational cost. We evaluate our method by link-level and system-level simulations. A complexity comparison is also presented.

DOI： 10.1109/vetecf.2003.1285094

Scopus

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Other Link： http://hdl.handle.net/10119/4704

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：European Signal Processing Conference, EUSIPCO  

This paper proposes a new spatial and temporal (S/T) pre-equalization technique for time-division-duplex (TDD) mobile multimedia communication systems. Base station (BS) employs an adaptive array antenna (AAA) and an adaptive decision feedback equalizer (DFE) for up-link signal reception. The weight vectors for the up-link AAA and DFE are also used for pre-equalization of signal to be transmitted. With the S/T pre-equalization at the transmitter, the needs for equalizers at mobile station (MS) can be eliminated. In order to evaluate performances of the proposed S/T pre-equalization scheme, this paper uses a detailed propagation model which looks into the mobile propagation mechanism more in detail than conventional multipath models. Performances of the proposed S/T pre-equalizer are then demonstrated through computer simulations. The results show that the proposed scheme is effective in reducing effects of both inter-symbol and cochannel interferences.

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Inst of Electronics, Inf & Commun Engineers of Japan  

This paper proposes Coherent-HYBrid Direct-Sequence Fast-Frequency-Hopping (CHYB-DS-FFH) CDMA with Adaptive Interference Cancelling (AIC) for cellular mobile communications. The features of CHYB-DS-FFH are symbol-by-symbol frequency diversity and low chip-rate DS multiplexing
both of which are based on a coherent FFH modulation and demodulation scheme. The combination of coherent FFH, space diversity, and AIC is very effective for reducing the performance degradation due to interference. Computer simulations demonstrate BER performance of a 2 hop 500-kHz-interval frequency hopping system using (i) a linear canceller or (ii) a nonlinear canceller. Both systems employ the two branch space diversity reception of 10 kb/s QPSK with FFH over a 1 MHz system bandwidth. In quasi-static channels, the average BER performance is 10-2 with average Eb/No less than 8 dB. In dynamic fading channels under full interference conditions, CHYB-DS-FFH with the linear adaptive interference canceller realizes a BER of 10-2 at the average Eb/No of 15 dB with maximum Doppler frequency fD of 5 Hz, whereas CHYB-DS-FFH with the non-linear adaptive interference canceller achieves the same BER at the average Eb/No of 15 dB with fD equal to 30 Hz.

Scopus

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.3169/itej.71.J80

CiNii Article

researchmap

Language：English   Publisher：IEEE  

DOI： 10.1109/WPMC.2017.8301814

researchmap

Other Link： https://dblp.uni-trier.de/db/conf/wpmc/wpmc2017.html#ChikamoriTDU17

Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.3169/itej.71.J80

CiNii Article

researchmap

Authorship：Lead author   Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.3169/itej.71.J80

CiNii Article

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Authorship：Lead author   Language：Japanese  

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

CiNii Article

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In recent years, service areas in cellular systems by using microcells or femtocells are widespread. In the mobile radio link design, several path loss estimation formulas are used. Radio propagation characteristics of the mobile systems in the slope areas are, however, not clear. In this study, we tried to correct the formula in urban areas to fit into slope areas within the distance of 1km from the base station. We propose a correction method taking account of the vertical plane angle, and the ratio of parallel course with respect to the base station. The correction method is based on our measurements using 2,100MHz band radio waves in cellular systems under different slope environments in Hiroshima, Okayama and Kitakyusyu in Japan. As a result, it was confirmed that the correction was effective to estimate the propagation path loss in the different slope areas.

CiNii Article

CiNii Books

researchmap

Language：Japanese  

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper experimentally evaluates broadband transmission performance of visible light communication using a transmission module circuit with a light emitting diode (LED) and a photodiode. In this experiment, OFDM signals of LTE systems are used and their error vector magnitude (EVM) is evaluated. The experimental results show that the EVM by transmission distance of 1.0 m is 4.5 % with 64QAM and its bandwidth of 5MHz. In addition, at the bandwidth of 20 MHz, the EVM by transmission distance of 0.5 m becomes less than 7.0 %.

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates transmission performance of a low-priority system with a non-linear distortion noise power control (DNC) method which controls non-linear distortion noise power according to required transmission quality of modulation schemes in cognitive radio systems by OFDM transmission. This DNC method employs the conventional clipping and filtering method, and its clipping level and distortion noise power ratio for filtering are selected so that the required noise power condition on each frequency band is satisfied. Distortion noise power characteristics to clipping levels with the DNC method are evaluated by computer simulations and the set clipping levels and distortion noise power ratios for filtering are determined from these results. The results of spectrum properties and BER performance show that the DNC method can satisfy required transmission quality of modulation schemes on frequency bands used by a low-priority system.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Sensor collaborative beamforming by adaptive transmission has been proposed for wireless sensor networks. In the beamforming, beamforming processing and collaborative transmitting sensor selection are adaptively performed according to reception quality of a receiving sensor, and power-saving effect by the beamforming was evaluated without frequency offset between transmitting and receiving sensors. This paper evaluates power-saving effect of the beamforming with frequency offset by computer simulation. The simulation results show that total power consumption of the beamforming with 3 collaborative sensor candidates can be decreased by 43% even with the normalized offset frequency of 1.0×10^<-3> between transmitting and receiving sensors.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates transmission performance and power-saving effect of sensor collaborative beamforming by adaptive transmission in which beamforming and collaborative transmitting sensor selection are adaptively performed according to reception quality of a receiving sensor. In this method, beamforming is used only in retransmission. Transmission performance and power-saving effect are evaluated by computer simulation. The simulation results show that the Signal-to-Noise power Ratio (SNR) by adaptive sensor collaborative beamforming can be improved by 18.0 dB at the Cumulative Distribution Function (CDF) of 10^<-2>. Total power consumption of the beamforming with 3 collaborative sensor candidates can be decreased by 14 % even with the transmission phase error of 60° among collaborative transmitting sensors.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates transmission performance with a non-linear distortion noise power control (DNC) method which controls non-linear distortion noise power according to required transmission quality of modulation schemes used in OFDM transmission systems for cognitive radio. This DNC method controls noise power added in a transmitter by clipping and filtering. Distortion noise power characteristics to clipping levels with the DNC method are evaluated by computer simulations and from these results the set clipping levels and distortion noise ratios for filtering are determined. The results of spectrum properties and BER performance with the DNC method show that the DNC method can control distortion noise power to satisfy required transmission quality of modulation schemes.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a novel iterative frequency offset estimation for sensor networks with Direct Sequence Spread Spectrum : DS-SS. In the proposed scheme, frequency offset is estimated based on the singular value decomposition in conjunction with a decorrelator that is introduced to improve the estimation performance in intersymbol interference channels. Because the frequency offset estimation attains high estimation performance in co-channel interference channels, the proposed estimation scheme achieves superior performance not only in intersymbol interference channels with co-channel interference, but also in the channel with big frequency offset. It is confirmed by computer simulation that the proposed estimation scheme achieves superior performance in 5-path Rayleigh fading with CIR=0dB, as far as the frequency offset normalized by the symbol duration is less than 7×10^1.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates in-band and out-of-band distortion noise power caused by non-linearity of an OFDM transmitter with multiple frequency bands by computer simulations. In addition, the effect of in-band and out-of-band distortion noise power reduction by using a clipping and filtering method is evaluated according to the number and frequency of used bands and filtering methods. The results of computer simulations show that out-of-band noise power can be reduced by 8.5dB with the optimized clipping level and filtering.

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEEE  

This paper proposes an iterative frequency offset estimation scheme for wireless sensor networks with direct-sequence spread spectrum. The proposed scheme is able to estimate large frequency offset that may occur at the receiver on devices with a sensor by iterating singular value decomposition (SVD)-based frequency offset estimation. In the proposed estimation scheme, a decorrelator is inserted in the iteration cycle that reduces the correlation between the received signals in order to improve the estimation performance, even in multipath fading channel with co-channel interference. It is confirmed by computer simulation that the proposed estimation scheme achieves exact frequency offset estimation in the channel, even when the frequency offset normalized by the symbol duration is 7 x 10(1).

Web of Science

researchmap

DOI： 10.1587/bplus.8.91

researchmap

Language：Japanese  

researchmap

Language：English   Publisher：IEEE  

We propose a model for predicting the path loss of a sloped area in a microcell service area of a mobile communication system. This is the prediction model to be proposed that targets a microcell. For practical use, a model requires parameters such as the base station height, angle of the sloped area, and distance from the base station to the sloped area. The proposed model uses a correction method based on the characteristics of the base station height to predict the path loss of the sloped area based on the path loss of flat terrain. The proposed model is verified based on measurements of a scale model and real environments. A 1/70 scale model is constructed of a residential area and the path losses are measured at 10.5 GHz. In real environments, the path losses are measured at 902 MHz. The measurement results show that the path losses predicted using the proposed model are close to the measured results.

DOI： 10.1109/APWiMob.2014.6920281

Web of Science

researchmap

Language：English   Publisher：IEEE  

This paper proposes a non-linear distortion noise power control method which uses clipping and in-band and out-of-band filtering methods for multi-band OFDM transmission. The proposed method selects appropriate clipping levels and filtering methods according to transmission power and required noise power conditions on own and the other system bands in a transmitter. The evaluation results show that the proposed method can control in-band and out-of-band distortion noise power so that required noise power conditions can be satisfied in multi-band transmission systems.

Web of Science

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a sensor collaborative beam forming method by adaptive transmission in which beam forming and collaborative transmitting sensor selection are adaptively performed according to reception quality of a receiving sensor. In this method, beam forming is used only in retransmission. Average Bit Error Rates (BERs) and Signal-to-Noise power Ratio (SNR) distribution in a receiving sensor are evaluated by computer simulation. The results show that the proposed method can improve the required E_b/N_0 for the average BER of 10^<-3> by 4.0 to 13.4 dB compared with that without beam forming. SNR distribution can also be improved by 5.8 to 19.8 dB at the Cumulative Distribution Function (CDF) of 10^<-2>.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates interference power reduction effect with the proposed transmission power control (TPC) method for low-priority systems by accurate estimation of interference power in high-priority systems before signal transmission in spectrum sharing systems. The utilization efficiency of the low-priority system with the TPC method in shared frequency bands is also evaluated. The results of computer simulations show that the TPC method can reduce interference power to less than permissible interference power of the high-priority system in the shared transmission power control band. The results also show that the total power ratio of -0.5dB for the low-priority system can be achieved in the band at transmission power reduction of 20dB.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a new transmission power control method for low-priority systems by the accurate estimation of interference power in high-priority systems before signal transmission. In the proposed method, the received spectrum of 1 sub-carrier in the high-priority system is calculated, and whole interference to the high-priority system is calculated by using the calculation result. The results of computer simulations show that the proposed method can reduce interference power to less than permissible one of the high-priority system in the shared transmission power control band.

CiNii Article

CiNii Books

researchmap

Language：Japanese  

researchmap

Language：English  

This paper proposes an iterative frequency offset estimation based on singular value decomposition (SVD). The proposed technique achieves high resolution estimation of frequency offset even in the presence of strong co-channel and inter-symbol interference. Moreover, the proposed technique can estimate large frequency offset, e.g., ΔfT = 12.8 with high precision. The proposed technique comprises two new ideas. One is frequency offset estimation by using SVD and an adaptive filter. The other is iteration of the above frequency offset estimation followed by a frequency offset reduction. The iteration of the frequency offset estimation improves the estimation performance. In fact, it is evaluated by computer simulation that estimate the frequency offset normalized by a symbol duration, ΔfT = 12.8, in wireless sensor networks with direct sequence spread spectrum (DS-SS). © 2013 IEEE.

DOI： 10.1109/ISPACS.2013.6704533

Scopus

researchmap

Language：English  

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

researchmap

Authorship：Lead author   Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

On spectrum sharing systems, transmission power control (TPC) effectively works to avoid harmful inter-system interference by reducing transmission power of a low-priority system in shared bands. In such cases, however, non-linear distortion noise severely affects transmission quality of low-priority TPC users because their transmission power is reduced. This paper proposes a non-linear distortion noise control method for adaptive modulation based on a clipping and filtering method to improve reception quality of the low-priority TPC users. The proposed method adaptively filters non-linear distortion noise in TPC bands according to required transmission quality of modulation schemes. From the relation between clipping levels and the non-linear distortion noise power when applying OFDM transmission, threshold levels for clipping and distortion noise power ratios for filtering used with the proposed method are investigated by computer simulations. Spectrum properties and BER performance with the proposed method are also evaluated. The results show the proposed method can meet required transmission quality according to modulation schemes of the low-priority users when sharing spectrum with TPC.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

As a scalable inexpensive Internet-access network, we have studied the Wireless Internet-access Mesh Network (WIMNET) that is composed of multiple access point (APs) connected through the Wireless Distribution System (WDS). Because all the traffics pass through an Internet gateway (GW) in WIMNET, the resolution of link congestions around the GW is very important. For this problem, we have proposed a WDS clustering algorithm to partition the APs into a set of WDS clusters where the APs in each cluster shares an GW, and have considered the adoption of a smart antenna for a Smart AP (SAP). Since the smart antenna is usually expensive, we have extended the WDS clustering algorithm to a cluster where only one or two SAPs are used. In this paper, we generalize this extension to a cluster with an arbitrary number of SAPs. Besides, we investigate the priority action of the smart antenna for multiple SAPs in one cluster. We evaluate the effectiveness through simulations using grid topology instances.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In wireless sensor networks, sensor collaborative beam forming in which plural transmitting sensors collaborate to form a signal beam has been studied to realize highly reliable transmission. In the beam forming, if there is frequency offset between transmitters and their receiver, the combined power by the beam forming decreases and it results in transmission performance degradation. This paper proposes a highly accurate estimation method of frequency offset under inter-symbol interferences owing to multipath propagation and co-channel interferences. The proposed method decomposes correlation matrix made from pilot signals into eigenvalues and estimates frequency offset from the eigenvector of the maximum eigenvalue. Under multipath propagation and co-channel interference conditions, the computer simulation results show that the proposed method can achieve estimation error of less than 1.0x10^<-4>, when the normalized frequency offset by a chip period in each pilot signal is 1.0x10^<-3>. This shows that the proposed method can realize highly accurate estimation of frequency offset even under multipath propagation and co-channel interference conditions.

CiNii Article

CiNii Books

researchmap

Authorship：Lead author   Language：English   Publisher：IEEE  

This paper proposes a non-linear distortion noise control method for secondary systems in spectrum sharing. The proposed method is based on conventional clipping and filtering methods, and adaptively shapes distortion noise power to improve reception quality of secondary users with transmission power control. In this paper, optimal clipping levels to control in-band distortion noise are investigated, and then the spectrum property and BER performance with the clipping levels are evaluated. The results confirm that the proposed method can control the distortion power effectively in shared bands and realize secondary systems with less degradation of reception quality when sharing spectrum with transmission power control.

DOI： 10.1109/VETECS.2012.6240058

Web of Science

researchmap

Language：English   Publisher：IEEE  

This paper proposes an adaptive non-linear distortion noise control method for low-priority systems under spectrum sharing environments. The proposed method adaptively controls distortion noise power of a transmitter to improve reception quality of shared bands with transmission power control. The distortion power is reduced to meet a required transmission quality. In this paper, the spectrum property and BER performance with the method are evaluated by computer simulations. The results confirm that the proposed method can effectively reduce the distortion power and adaptively control transmission SNRs according to the required transmission quality.

DOI： 10.1109/APCC.2012.6388146

Web of Science

researchmap

Language：English   Publisher：IEEE  

Mobile path loss estimation models for small cell area on a sloping terrain become important function in the radio link design of cellular systems. Okumura and Lee models are known for the sloping terrain path loss estimation, but the applicable cell size is lager than today's small cell area with less than 1.5km radius. Recently, a new estimation model called Fujitani model has been proposed for such a small cell including sloping terrain area. However, there were no comparison discussions about the estimation by the other models. In this paper, the path loss estimation comparisons by Okumura, Fujitani, and Lee models are discussed based on the same data measured in a typical short distance sloping terrain area. The result shows that Fujitani model is prospective for such sloping terrain path loss estimation in a small cell, but further measurement studies in various slope terrain areas and additional parameter considerations are needed to realize general applicability.

DOI： 10.1109/APCC.2012.6388183

Web of Science

researchmap

Language：English  

As a scalable cost-efficient Internet-access network, we have studied the Wireless Internet-access Mesh Network (WIMNET) that is composed of multiple access point (APs) connected through the Wireless Distribution System (WDS). Because all the traffics pass through an Internet Gateway (GW), the resolution of link congestions around the GW is very important. To solve this problem, we have proposed a clustering algorithm to partition the APs into a set of clusters where each cluster consists of the APs sharing the same GW. In addition, we have considered the use of a smart antenna at a special AP called a Smart AP (SAP). In this paper, we extend this clustering algorithm for smart antenna use at SAPs. Besides, we investigate the link activation strategy for the smart antenna, because it allows a variety of link activations for packet transmissions. We evaluate the effectiveness through simulations using the WIMNET simulator. © 2012 IEEE.

DOI： 10.1109/GCCE.2012.6379939

Scopus

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, a spectrum sharing method between wireless communication systems has been studied to use frequency resources with much higher efficiency. In general, different systems for spectrum sharing have different system bandwidths. Therefore, spectrum sharing systems such that a low-priority system has wider frequency bands than a high-priority system should be considered. In such spectrum sharing environments, reducing transmission power of the low-priority system in partial frequency bands overlapped with the high-priority system is considered to work effectively so as to avoid harmful interference to the high-priority system. This paper proposes a non-linear distortion noise control method based on a clipping and filtering method for the low-priority system to improve reception quality degradation which occurs in shared bands whose transmission power is reduced. The proposed method adaptively controls distortion noise power in shared bands with transmission power control according to the amount of the reduced power. In this paper, optimal clipping levels, required parameters in the proposed method, are investigated, and then the spectrum property and BER performance with the optimal clipping levels are evaluated by computer simulations. The results confirm that the proposed method can significantly improve reception quality of the low-priority system in shared bands with transmission power control.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

As a scalable Internet access network, we have studied the Wireless Internet-access Mesh Network (WIMNET) that is composed of multiple access point (APs) connected through the Wireless Distribution System (WDS). For large scale WIMNET, because the traffic through the Internet gateway (GW) becomes very high, it is composed of multiple WDS clusters where one cluster consists of APs sharing the same GW. Even in this hierarchial WIMNET, links around the GW are still crowded in each WDS cluster and may become bottlenecks of whole communications. Hence, we have proposed the adoption of a Smart AP (SAP) using the smart antenna technology for bandwidth enhancements. In this paper, we propose an extension of our WDS clustering algorithm for WIMNET such that the GW and one adjacent AP are selected as SAPs in each WDS cluster. Through simulations using grid topology instances, we verify the effectiveness of our algorithm extension.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We have studied the Wireless Internet-access Mesh NETwork (WIMNET) as a scalable wireless local area network that is composed of multiple access points (APs) connected through the Wireless Distribution System (WDS). To avoid the performance degradation due to traffic overloads, the number of APs in a single WDS is limited. Hence, we have proposed a WDS clustering algorithm to partition a given set of APs into a disjoint set of WDS clusters where the APs in one WDS cluster shares a single gateway (GW) to the Internet and are connected by a single WDS. As all the traffics from/to the Internet pass through the GW in a WDS cluster, links incident to the GW can be bottlenecks of whole communications. In this paper, in order to increase the throughput there by adopting the MIMO channel at the GW, we propose an extension of the WDS clustering algorithm to the WIMNET with the MIMO channel GW. Through simulations using several instances, we verify the effectiveness of our algorithm extension.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes an iterative peak power reduction method with adaptive intermediary over-sampling which uses the necessary minimum bandwidth according to iteration number for wireless OFDMA systems. The required bandwidth to each iteration number is evaluated by computer simulation, and over-sampling numbers in iterative processing are controlled by using the simulation results. The results show that the required bandwidth is 1.6, 2.0, and 2.7 times of the used signal bandwidth at the iteration number of 1, 2, and 3, respectively. The proposed adaptive over-sampling method can reduce its multiplication number by 13%.

DOI： 10.1587/transcom.E94.B.576

Web of Science

researchmap

Authorship：Lead author   Language：Japanese  

researchmap

Language：English  

In order to offer an inexpensive, scalable Internetaccess wireless network, we have studied the architecture, protocols, and design optimizations of the wireless Internet-access mesh network (WIMNET) that adopts multiple access-points (APs) connected by wireless links. WIMNET can improve the dependability to failures of links and/or APs by allocating APs redundantly in the network field. Because redundant APs may increase the operational cost and degrade the throughput due to increasing radio interferences, only the necessary APs for the connectivity between the hosts and the Internet gateway should be activated in communications. Previously, we have defined the active AP selection problem of selecting the minimum number of active APs, and proposed its heuristic algorithm. However, the throughput should be maximized in WIMNET as a bandlimited wireless network, even if the number of active APs is slightly increased. In this paper, we propose the extension of the active AP selection algorithm for the throughput maximization using the average hop count. We confirm the effectiveness of our algorithm extension through simulations in three instances, where the throughput is improved by about 10% with 7-14 additional active APs on average. © 2011 IEEE.

DOI： 10.1109/INCoS.2011.50

Scopus

researchmap

Language：English   Publisher：World Scientific Publishing Co. Pte Ltd  

As an inexpensive, flexible, and scalable Internet-access wireless network, we have studied the architecture, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET) that adopts multiple access-points (APs) connected through wireless links. WIMNET can improve the dependability to failures of APs and/or their links by allocating APs redundantly in the network field. Because redundant APs may increase the operational cost and degrade the throughput due to increasing radio interferences, only the necessary APs for connectivity between the hosts and the Internet gateway should be activated in communications. In this paper, we first define the active AP selection problem of selecting the minimum number of active APs, and prove the NP-completeness of its decision version through reduction from the known minimum set cover problem. Then, we propose an active AP selection algorithm of deactivating APs one by one until no more AP can be deactivated. Due to the limited transmission capacity in WIMNET, we further present an algorithm extension for throughput maximization. We verify the effectiveness of our proposal through simulations in three instances, where the number of active APs is reduced by more than 40% and the throughput is improved by more than 10% from the original in any instance. © 2011 World Scientific Publishing Company.

DOI： 10.1142/S0219265911002915

Scopus

researchmap

Language：English  

researchmap

Language：English  

researchmap

CiNii Article

researchmap

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates interference reduction effects by transmission power control (TPC) under spectrum sharing environment between different wireless systems in which an OFDMA system is assumed for the interfering system and the power density on a part of the interfering system band is reduced. The results of the computer simulations show that the undesired spectrum regrowth is caused by inter-sub-carrier interference, which results in degradation of interference reduction effects, and it is larger around the both ends of the TPC band. The spectrum regrowth on the TPC band is less than 1dB from the set transmission power density except 16 sub-carriers close to the band with default power density, when the transmission power density of the TPC band is 20 dB below the default density. On the other hand, the spectrum regrowth becomes more than 5 dB even around the center of the TPC band, when the transmission power density is reduced by -40 dB. Moreover, we also clarified the BER performance degradation on the victim system due to the spectrum regrowth.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Authorship：Lead author   Language：Japanese  

researchmap

Language：English  

researchmap

Language：English   Publisher：IEEE  

Service area upgrading and expanding is expected in current and future cellular systems. Since residential areas on a hilly and/or slope terrain are spreading in the outskirts of cities in Japan, the correction for the urban mobile propagation loss formula becomes one of the important issues in radio link and cell layout designs in those areas, especially within 1km distance from a base station. This paper introduces an example of correction formula for the slope terrain area based on an experimental study of mobile path loss prediction. The result shows the path loss at the objective point can be estimated by the urban mobile path loss and the correction value according to the factor expressed by the elevation angle from the base station antenna top. Although the average slope angle is only used as a parameter in the conventional correction for the slope terrain area with at least 5 to 10km length, the result means it is not enough for the correction to the area within 1km distance from a base station.

Web of Science

researchmap

Language：English  

In this study, it is investigated the validity of applying nonlinear device model to estimate distorted spectrum shapes of the OFDM signals for spectrum sharing studies. We used an LNA and two LNBs, which are off-the-shelf devices and the spectrum shape of OFDM signal distorted by the nonlinear devices, are evaluated by the means of model-based estimation and indoor experiment. As the results, the spectrum shapes obtained by the two evaluation show good agreement, thus the model-based estimation is considered to be an effective method on the spectrum sharing studies. © 2010 IEEE.

DOI： 10.1109/ICWITS.2010.5611834

Scopus

researchmap

Language：English  

We evaluated out-of-band distortion of OFDM signals caused by LNBs for FSS systems, which might be also important for spectrum sharing between the IMT-Advanced system and FSS expected from the result of WRC'07. The evaluation results show that the input power of interfering signals should not exceed -60dBm to make ACLR less than -50dB. The results also show that the AM-AM characteristic is the dominant factor to decide spectral properties, while AM-PM characteristics might be important for accurate estimation of out-of-band distortion by a part of non-linear amplifiers. © 2010 IEEE.

DOI： 10.1109/ICWITS.2010.5611819

Scopus

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates spectrum property of DFTS-OFDM transmission with non-linear distortion of a transmission power amplifier by computer simulations. N-times DFTS-OFDM transmission, which uses plural DFTs, and Clustered DFTS-OFDM transmission, in which DFT output signals are divided into plural clusters, are used in the simulations. The simulation results show that the PAPR of N-times DFTS-OFDM transmission with four DFTs increases by 2.0dB at the maximum compared with that with one DFT. In Clustered DFTS-OFDM transmission with four clusters, the maximum PAPR increase is 1.4dB. Although the out-of-band distortion power ratio with the input back-off value of 4dB is -30dB in both transmission systems, the devised sub-carrier mapping can reduce the occupied bandwidth of the distortion power. Clustered DFTS-OFDM transmission can especially reduce in-band distortion power by 4.5dB compared with N-times DFTS-OFDM transmission.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes an adaptive control method for soft clipping which is one of effective peak power reduction methods in Orthogonal Frequency Division Multiple Access (OFDMA) systems. The proposed method can control in-band and out-of-band distortion power according to the using rate of the system band and the required transmission quality. The out-of-band distortion power with soft clipping can be reduced by 6dB compared with hard clipping. The simulation results show that a low-distortion OFDMA transmitter can be realize with reasonable computational complexity because iterative processing is unnecessary.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates the required bandwidth to iterative peak power reduction to exactly reduce PAPRs in the proposed intermediary over-sampling method that can reduce computational complexity in OFDMA transmitters. The results of computer simulations show that the required bandwidth is 1.6, 2.0, and 2.7 times of the used signal bandwidth at the iteration number of 1, 2, and 3, respectively. In addition, the results show the iterative peak power reduction method with intermediary FFT/IFFT points can achieve the same BER performance as the usual over-sampling method.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

researchmap

Language：English   Publisher：IEEE  

This paper evaluates transmission performance and power-saving effect of the collaborative beamforming for wireless ubiquitous network systems. The evaluation of power-saving includes the power consumption for signal transmission to collaborative sensors in beamforming. The simulation result shows that the total power consumption of the beamforming with 3 collaborative sensors can be decreased to about 1/2 compared with that of a transmitting sensor without the beamforming in free-space propagation channels. In typical mobile propagation channels with shadowing, the total power consumption of the beamforming by using 3 collaborative sensors can be reduced to 1/7 of that without the beamforming. The above results confirm that the collaborative beamforming can be achieve lower power consumption, and greatly contributes to realize low-power transmission in wireless sensor network systems.

Web of Science

researchmap

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The large PAPR of orthogonal frequency division multiplexing (OFDM) transmission is one of the serious problems for mobile communications that require severe power saving. Iterative clipping and filtering is an effective method for the PAPR reduction of OFDM signals. This paper evaluates PAPR reduction effect with a graded band-limiting filter in the iterative clipping and filtering method. The evaluation result by computer simulation shows that the excellent peak reduction effect can be obtained in the fewer iteration numbers by using a roll-off filter instead of the conventional rectangular filter, and the iteration number with the roll-off filter achieving the same PAPR is fewer by twice. The result confirms that the clipping and filtering method by using a graded band-limiting filter can achieve low peak OFDM transmission with less computational complexity.

DOI： 10.1093/ietfec/e90-a.7.1362

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEEE  

In this paper, we propose a new peak power reduction method applicable to OFDMA systems for broadband wireless communications, in which a user uses some frequency bands in all system bands, by using iterative peak reduction. The proposed method separates the system bands into an information signal band and peak-reduction signal insertion bands, and generates peak-reduction signals in the peak-reduction signal insertion bands by using iterative signal processing. Moreover, low power peak-reduction signals are generated in the information signal band to improve peak-reduction performance. The results by computer simulations show that the proposed method can achieve the PAPR reduction of 3 to 4dB with almost no degradation of BER performance.

DOI： 10.1109/ISTMWC.2007.4299176

Web of Science

researchmap

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we proposed a new peak reduction method applicable to OFDMA systems, in which a user uses some frequency bands in all system bands, by using iterative peak reduction method for broadband wireless communications. The proposed method separates the system band into a information signal band and a peak-reduction signal band, and generates peak-reduction signals in the peak-reduction signal band by using iterative signal processing. Moreover, low level peak-reduction signals are generated in the information signal band to improve peak-reduction performance. The results by computer simulation show that proposed method can achieve the PAPR reduction of 3 to 4dB with almost no degradation of BER performance.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

One of the key technologies to realize future broadband mobile communications is orthogonal frequency division multiplexing (OFDM) transmission. However, the peak-to-average power ratio (PAPR) in OFDM transmission is so much larger than that in single carrier transmission that its adoption in mobile communication systems is uncertain. This paper evaluates the transmission performance possible with iterative peak reduction to design more efficient OFDM transmitters. The PAPR reduction effect and bit error rate (BER) performance are clarified by computer simulations. We calculate the set PAPR value that achieves a target PAPR in the iterative peak reduction method. The required E-b/N-0 performance is evaluated under the calculated PAPR condition. The results are effective in designing the back-off value of a transmission power amplifier given fixed transmission quality and computational complexity.

DOI： 10.1093/ietfec/e89-a.7.1968

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEEE  

In the radio link design of cellular CDMA system, system capacity has been estimated with the uniform traffic distribution condition so far. In many cases, however, actual traffic in a service area is not distributed uniformly. Therefore, this paper discusses the up link capacity of the cellular CDMA system applied in a service area with tapered traffic distribution condition. The analytical result shows that the system capacity is degraded according to the degree of traffic concentration to the service area center. It is also suggested that the cell size change in inverse to the degree of traffic concentration is effective to mitigate the system capacity degradation.

Web of Science

researchmap

researchmap

researchmap

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Future broadband mobile communication systems are necessary to achieve the bit rates of 100 Mbit/s. Orthogonal Frequency Division Multiplexing (OFDM) transmission is an attractive technology because it can remove the influence of frequency selective fading in broadband transmission by adding a suitable guard interval to each OFDM symbol. However, peak-to-average power ratio (PAPR) is very large in OFDM transmission. In this paper, we propose a new PAPR reduction method which can be applied even when unusable bands are inside the system band. In the proposed method, peak reduction signals are generated by iterative signal processing only in the usable frequency band, and filtering to remove out-of-band components of the peak reduction signals is incorporated into the iterative signal processing. The results of computer simulation show that the proposed method can effectively reduce peak power without expanding the spectrum both outside the system band and into unusable bands inside the system band. By using the proposed method, the broadband mobile communication system with low peak power and high flexibility of frequency band use can be realized.

DOI： 10.1093/ietfec/e88-a.7.1897

Web of Science

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper aims to improve the performance of the soft canceller followed by simplified minimum mean-square error (SC/SMMSE) turbo receiver [11] for multiple-input and multiple-output space-division multiplexing/orthogonal frequency division multiplexing (MIMO-SDM/OFDM) transmission; it performs iterative parallel soft interference cancellation and MMSE filtering, and stream-wise soft-input and soft-output decoding. For this aim, we newly introduce two detection techniques: 1) serial interference cancellation, and 2) cyclic redundancy check (CRC)-assisted interference cancellation and MMSE filter tap computation. Various computer simulations are conducted to evaluate the performance enhancement obtained via the use of the two detection techniques. The computer simulation results show that this paper's proposed serial SC/SMMSE turbo receiver with CRC achieves frame error rate (FER) performance gain over existing MIMO receivers (MMSE receiver, V-BLAST receiver, parallel SC/MMSE-matched filter (MF) turbo receiver, and parallel SC/S-MMSE turbo receiver) for QPSK, 16QAM and 64QAM modulation while keeping the comparable complexity order.

DOI： 10.1093/ietcom/e88-b.5.2110

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

researchmap

researchmap

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

researchmap

DOI： 10.1093/ietfec/e88-a.7.1897

CiNii Article

researchmap

Language：English   Publisher：IEEE  

According to the recent introduction of digital-TV broadcasting services and the band expansion for mobile communication services, new systems by the integration of mobile communication and terrestrial TV broadcasting systems in the UHF band are expected to realize efficient resource management and new attractive services. In this paper, the aspects on system configuration and mobile radio link design are examined to investigate the possibility of integration of mobile communication and TV broadcasting systems operating in the UHF band.

Web of Science

researchmap

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

MIMO channel transmission with turbo equalization is one of promising techniques to perform large capacity with limited bandwidth. Combinations of soft canceler and liner filter are proposed for the equalization parts, and matched filter(MF) or MMSE filter are used for the liner filter. The MF, however, does not have effects of intentional interference cancellation, thus causes FER performance degradation. On the other hand, the strict MMSE filtering needs symbol-by-symbol calculation of tap coefficients because of different degree of residual interference at each symbols. In this paper, we propose novel turbo equalization method for MIMO channel signal transmission. The proposed method utilized MMSE criterion to make tap coefficients based on the degrees of residual interference over a frame. The resultant tap coefficients are applied to all symbols on the frame. The proposed method achieves lower FER than those with MF, because our method also care for interference cancellation besides desired signal combining. Furthermore our method does not require much increase of computational complexity like symbol-by-symbol MMSE filter, as it applies common tap coefficient to all symbols over a frame. We show the effectiveness by link-level and system-level computer simulations and by complexity comparisons.

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes a new signal peak power reduction technique, Peak Reduction based on Control Signal lnsertion (PRCSI), for broadband mobile communications based on multi-channel signaling schemes. PRCSI reduces the peak power with a peak control signal that is generated symbol-by-symbol; no signal band expansion is incurred because the peak control signal is inserted into. the transmission signal band. PRCSI can achieve 4dB peak power reduction for 8-carrier signaling, while the E-b/N-0 value required to achieve 10(-3) average BER is I dB larger with PRCSI than without it. This BER performance degradation can effectively be compensated by the proper use of Trellis coding. The proposed technique is applied to OFDM transmission systems with large carrier number. The proposed technique can achieve 3-dB peak power ratio for 128-carrier OFDM signals with less than 1-dB performance degradation at the BER of 10(-3).

Web of Science

researchmap

Language：English   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A new space-time turbo equalization algorithm is derived for frequency-selective multiple-input-multiple-output (MIMO) channels with unknown interference. The algorithm is an extension of our proposed MIMO equalization algorithm [12], which performs joint channel estimation, multiple user's signal detection, and decoding, all in an iterative manner. This paper's proposed algorithm uses estimates of the correlation matrix of composite unknown interference-plus noise components to suppress the unknown interference while effectively separating multiple users' signals to be detected (referred to as "known user'' later). The correlation matrix of the composite unknown interference-plus-noise, components can be estimated by time averaging the instantaneous emperical correlation matrix over the training period. Since the iterative channel estimation Yields better channel estimates as more iterations are performed, thereby the estimate of the correlation matrix of the unknown interference-plus-noise components also becomes more accurate. This results in better, signal detection performances, even in the presence of unknown interferers. A series of computer simulations show that this paper's proposed algorithm can properly separate known users' signals while suppressing unknown interference.

DOI： 10.1109/TVT.2003.811615

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

researchmap

CiNii Article

researchmap

Language：English   Publisher：IEEE  

This paper proposes a novel turbo equalization method, called SC/Simplified-MMSE (S-MMSE), for multiple-input multiple-output (MIMO) channel signal transmission. Our method, which deals with residual inter sub stream interference as their average over a frame, achieves excellent error performance at small computational cost. We evaluate our method by link-level and system-level simulations. A complexity comparison is also presented.

Web of Science

researchmap

Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

MIMO channel signal transmission is one of the key technologies to realize broadband mobile communication systems with the bit rate of up to 100 Mbit/s. Space Division Multiplexing (SDM) with multiple antennas in MIMO channel transmission is a promising technology to achieve a high capacity system with very high peak throughput. In this paper, we describe the receiver constructions for MIMO-SDM systems with iterative signal processing. We also introduce the recent research activities of dual polarized antennas for MIMO-SDM channel signal transmission, required microwave propagation characteristics, and so on.

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Recently, joint spatial-temporal signal processing has been recognized as the key to reducing the effects of the intersymbol and cochannel interference seen in very high bit-rate mobile radio communications systems. Developing hardware simulators that can simulate mobile radio propagation scenarios in time and space domains is essential for evaluating the real-time performance of spatial-temporal signal processing schemes. This paper outlines a complex baseband platform developed for spatial-temporal mobile radio channel simulations. The platform consists of a complex baseband fading/array response simulator, a digital signal processor (DSP) board, and a general-purpose parameter estimator that uses systolic array implementation of the recursive least square (RLS) algorithm. Results of experiments conducted using the developed platform are presented to confirm the proper operation of the system.

DOI： 10.1109/TVT.2002.801772

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we discuss a cascaded connection of an adaptive array antenna, in which each antenna contains a feedforward filter, and the Viterbi equalizer. When using the feedforward filter, MMSE tap coefficients degrade the system performance because noise correlation in an array output becomes high. Computer simulations show that proposed methods have better BER performance under a large delay spread condition and when the feedforward filters have few taps. In addition, we propose a method applying a multi-input Viterbi algorithm with a multi-beam adaptive array antenna. As a result, the proposed method improves BER performance significantly.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Signal separation performances of receivers for MIMO channel signal transmission degrades due to correlation of the channel. This paper proposes an index to evaluate the performances of MIMO Turbo receivers which has MMSE filtering process. We define Space-Time Correlation in frequency selective MIMO Channels, and use the norm and phase component of the correlation value as the index for signal separation performance of a receiver. Simulation results show that FER performance of a receiver degrades with the index closer to I, showing the reliability of the proposed index.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

For broadband mobile communications, an indispensable effort should be to cope with severe Intersymbol Interference (ISI). We have proposed an iterative ISI equalization algorithm, Soft Canceller followed by MMSE filter (SC/MMSE) with a matched filter approximation, that offers low computational complexity without causing any serious performance degradation from that of the optimal receiver. In this paper, it is shown that the proposed SC/MMSE algorithm can further reduce computational complexity by adaptively selecting path components depending on their strengths. Computer simulation results show that the proposed SC/MMSE algorithm does not cause any serious performance degradation by neglecting the paths components having relatively low strengths.

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEEE  

Fading correlation is an obstacle that degrades the potential capacity of Multiple Input and Multiple Output (MIMO) channels. This paper proposes a hybrid MIMO system that mitigates the throughput loss in highly correlated propagation channels. In the proposed system, the transmitter uses the spatial multiplexing scheme or the selection transmit diversity scheme according to information fed back from the receiver. The receiver determines which of the two transmission schemes provides higher throughput from the metrics of the spatial correlation and Signal to Noise Ratio (SNR) of the channel. We define the spatial correlation for MIMO channels, and by computer simulations obtain throughput loss as a function of spatial correlation for the spatial multiplexing scheme. The obtained data is used for transmission scheme selection. Since the feedback information contains only commands of the selected transmission scheme and symbol constellation size, bandwidth loss due to the feed back is acceptable. Simulation results show that by using spatial correlation the proposed system can switch from the spatial multiplexing scheme to the transmit diversity scheme in highly correlated propagation environments, and so mitigate the severe throughput loss which occurs in conventional non hybrid spatial multiplexing MIMO systems.

DOI： 10.1109/WPMC.2002.1088399

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

MIMO communication systems have been recognized as being able to achieve high speed signal transmission and system capacity. In this paper, technical subjects on radio signal processing in this MIMO channel signal transmission are briefly summarized. Configuration and performances of our proposed SC/MMSE space-time MIMO turbo equalizer, which can satisfy the requirements defined in the technical subjects, are described. Results of computer simulations show that SC/MMSE space-time MIMO turbo equalizer can drastically reduce computational complexity required for the MIMO signal separation while keeping performance almost equivalent to the optimal receiver.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes a beam and null simultaneous steering Space-Time Equalizer (S/T-Equalizer). The proposed S/T-Equalizer performs separated S/T-signal processing in order to reduce computational complexity to a practical level. For spatial signal processing, a new Adaptive Array Antenna algorithm is used that combines the beam and null steering concepts. For temporal signal processing, a conventional delayed decision feedback sequence estimation equalizer may be used. The proposed S/T-Equalizer was prototyped, and a series of field tests was conducted using a 5 GHz frequency band to evaluate transmission performances of the proposed system. Results show that the proposed S/T-Equalizer can reduce inter-symbol interference effects while maintaining reasonable signal strength, thereby improving BER performance.

Web of Science

researchmap

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Providing results of a series of link-level simulations for a class of spatial and temporal equalizer (S/T-equalizer) is the primary objective of this letter, which is supplemental to this letter`s companion article. The S/T-equalizers discussed in this letter have a configuration that can be expressed as the cascaded connection of adaptive array antenna and maximum likelihood sequence estimator (MLSE): each of the adaptive ar ray antenna elements has a fractionally spaced tapped delay line (FTDL), and the MLSE has taps covering a portion of the channel delay profile. Both the desired and interference signals suffer from severe inter-symbol interference (ISI). A major difference of this article from its companion letter is that account is taken of the presence of co-channel interference (CCI). Bit error rate (BER) performance of the S/T-equalizer is presented as a result of the link-level simulations that use field measurement data.

Web of Science

researchmap

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This letter shows the results of a series of link level simulations conducted to evaluate the performances of spatial and temporal equalizers (S/T-equalizers) using field measurement data. The configuration of the spatial and temporal equalizer discussed in this letter can be expressed as a cascade of an adaptive array antenna and maximum likelihood sequence estimator (MLSE): each of the adaptive array antenna elements has a fractionally spaced tapped delay line (FTDL), and the MLSE has taps covering a portion of channel delay profile. Bit error rate (BER) performances of the S/T-equalizers are presented, and performance sensitivity to symbol timing offset is investigated.

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Combined effects of Co-channel Interference (CCI) and Inier-Symbol Interference (ISI) are chief handles to overcome for broadband multimedia mobile communications. Recently, joint spatial and temporal equalization (S/T-equalization) techniques have been recognized as technological basis that can solve these problems. To demonstrate effectiveness of S/T-equalizers in realistic mobile propagation environments, authors have conducted link-level simulations using multi-dimensional channel sounding field measurement data. This paper presents results of system-level simulations that takes into account the presence of multiple interferences, assuming a sectored cell layout. It is shown that without using neither spreading nor coding 7×10^<-3> BER can be achieved at more than 99% of the areas, even though all users use the same time- and frequency- slots in the cell layout considered.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Authorship：Lead author   Language：English   Publisher：IEEE COMPUTER SOC  

Joint spatial and temporal equalization techniques are considered most effective in reducing effects of Go-channel Interference (CCI) and Inter-Symbol Interference (ISI) in broadband mobile communications. This paper proposes a new configuration of Spatial and Temporal Equalizer (S/T-Equalizer) using separated spatial and temporal signal processing., An iterative parameter estimation technique is also proposed for the S/T-Equalizer. Computer simulations were conducted to demonstrate effectiveness of the proposed S/T-Equalizer. Results of computer simulations show that the proposed S/T-Equalizer can achieve excellent performances in the presence of CCI and ISI.

DOI： 10.1109/SPAWC.2001.923908

Web of Science

researchmap

Language：Japanese   Publisher：電気通信協会  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The MIMO system concept has been recognized as one of attractive techniques for post-IMT2000 mobile communication systems. MIMO systems accommodate several users using the same channel in a cell, thus high data rates and throughputs can be attained with a limited frequency bandwidth. We have proposed a space-time turbo-equalizer for frequency selective MIMO channels that achieves excellent performances without requiring prohibitively large computational effort[5], [6]. In fact, the space-time MIMO trubo-equalizer requires complexity of Ο((# of total paths)^3 ). In this paper, we evaluate performances of the space-time MIMO turbo-equalizer using field measurement data. Results of the simulations are presented to verify performaces of the MIMO space-time turbo-equalizer in real fields.

CiNii Article

CiNii Books

researchmap

researchmap

Language：English   Publisher：IEEE COMPUTER SOC  

This paper shows results of link level simulations conducted to evaluate performances of spatial and temporal equalizers (S/T-Equalizers) using field measurement data. The spatial and temporal equalizer discussed in this paper have a configuration expressed as a cascaded connection of adaptive array antenna and maximum likelihood sequence estimator (MLSE): each of the antenna elements has a fractionally spaced tapped delay line (FTDL), and the MLSE has taps covering a portion of channel delay profile. Bit error rate (BER) performances of the S/T-Equalizers, including the in the presence of Co-channel Interference (CCI) are presented. Performance sensitivity to symbol timing offset is also investigated. Major conclusions of this paper are that allocating more taps to spatial domain is more effective than to time domain when the total number of taps is fixed, and that increasing the FTDL length is effective in reducing performance sensitivity to timing offset.

DOI： 10.1109/SPAWC.2001.923856

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Combined effects of Co-channel Interference(CCI) and Inter-Symbol Interference(ISI) are chief handles to overcome for Broadband multimedia mobile communications. Recently, joint spatial and temporal equalization (S/T-equalization) techniques have been recognized as technological basis that can solve these problems. To demonstrate effectiveness of S/T-equalizer, performances have to be evaluated in realistic mobile propagation environments. This paper presents results of link-level simulations conducted to evaluate distributions of Signal to Interference plus Noise power ratio (SINR), achieves by various S/T-Equalizer configurations, in a field measurement data considered with an actual cell configuration.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Broadband signal transmission over mobile radio channels is required, which imposes plobrems due mainly to Co-channel Interference(CCI)and Inter-Symbol Interference(ISI). Recently, joint spatial and temporal equalization(S/T-equalization)techniques have been recognized as technological basis that can solve these problems. To demonstrate effectiveness of S/T-equalizer, performances have to be evaluated in realistic mobile propagation environments. This paper investigates different types of S/T-equalizer configurations and their performances through link-level simulations using field measurement data.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In broadband mobile communications, Co-Channel Interference(CCI), Inter-Symbol Interference(ISI), and relatively large propagation loss have to be overcome. Joint Space-Time-Equalization(S/T-Equalization) is considered most effective in solving these problems. This paper proposes a new S/T-Equalization technique that performs separated S/T-signal processing with acceptable levels of complexity. The algorithm used in an Adaptive Array Antenna combines the beam and null steering concepts; a sharp beam is steered towards the desired signal while nulls are steered towards interferers. For temporal equalization, a conventional DDFSE-type equalizer is used. The proposed S/T-Equalizer was prototyped, and field tests were conducted in the 5GHz frequency band. The results confirm that the proposed S/T-Equalizer can reduce ISI effects while maintaining reasonable signal strength, thereby improving BER performance. This paper outlines the field tests and its results.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In mobile multimedia communications, Co-channel Interference(CCI) and Inter-Symbol Interference(ISI) are major problems to overcome. Joint spatial and temporal equalization technique is considered most effective in solving the problem. This paper proposes a new configuration of spatial and temporal equalizer(S/T equalizer)using separated spatial and temporal signal processing for mobile radio communications. Computer simulations were conducted to evaluate performances of the proposed S/T equalizer. Results of computer simulations show that the proposed S/T equalizer can achieve excellent CCI and ISI canceling performance.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper proposes a new multiple-access (MA) scheme, coherent frequency hopping MA (CFHMA) with multiuser detection, which effectively obtains the diversity effect for realizing spectrally efficient mobile communications. CFHMA is fundamentally equivalent to a coherent fast frequency hopping frequency-division MA (FDMA) that incorporates low spreading factor direct-sequence (DS) code-division IMA (CDMA). Multiple users occupy the same frequency band, and they are simultaneously detected by multiuser detection. There are several implementations of CFHMA. Two major techniques are introduced: coherent hybrid DS fast FH (FFH) (CHYB-DS-FFH) and interleaved FH (IFH), This paper focuses on IFH and discusses its principle of operation, transmission system configuration, and performance aspects. The results suggest the feasibility of a spectrally efficient mobile radio system.

DOI： 10.1109/25.832984

Web of Science

researchmap

Language：English   Publisher：IEEE  

This paper proposes a beam and null simultaneous steering Space-Time Equalizer (S/T-Equalizer). The proposed S/T-Equalizer performs separated S/T-signal processing in order to reduce computational complexity to a practical level. For spatial signal processing, a new Adaptive Array Antenna algorithm is used that combines the beam and null steering concepts. For temporal signal processing, a conventional delayed decision feedback sequence estimation equalizer may be used. The proposed S/T-Equalizer was prototyped. A series of field tests war then conducted using the 5GHz frequency band to evaluate transmission performance of the proposed system The results show that the proposed S/T-Equalizer can reduce inter-symbol interference effects while maintaining reasonable signal strength, improving BER performance.

Web of Science

researchmap

Language：Japanese   Publisher：電気通信協会  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In broadband mobile communications, inter-symbol interference is one of the major problems to overcome. Adaptive equalizers have been considered effective in solving the problem. This paper proposes an adaptive equalizer utilizing the concepts of metric combining space and time-diversity. The proposed equalizer was prototyped for a real time operation at a transmission bitrate of 24Mbps. The prototyped equalizer has 2-branch space and 2-branch time-diversity capabilities, thereby 4-branch diversity in total. Experimental results show that the prototyped equalizer achieves almost the same performances as obtained through computer simulations.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In broadband mobile communications, co-channel interference and inter-symbol interference as well as relatively large propagation loss are the major problems to overcome. Adaptive Array Antennas have been considered effective in solving these problems. Previously, the concepts of beam steering and null steering have been developed as different technology bases for adaptive array antennas. This paper aims to combine beam and null steering concepts : main beam is steered toward the desired signal components while nulls being steered toward interference components. This paper also creates a new channel modeling scheme using ray-tracing to enhance the accuracy of system performance evaluations. Coverage achieved by the proposed antenna system is estimated by using the created channel modeling scheme. Results of a series of computer simulations show that the proposed antenna system can improve SIR performance over a omni antenna system by about 30dB at 95% coverage in a sub-urban area.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a new spatial and temporal pre-coding scheme for TDD multimedia mobile communication systems. SIR and BER performances are demonstrated through computer simulations. It is shown that the proposed scheme is effective in reducing signal distortions due to inter-symbol interference (ISI) and co-channel interference (CCI) under delay- and interference-rich multipath fading environments.

CiNii Article

CiNii Books

researchmap

Language：English  

researchmap

researchmap

Language：Japanese  

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Parallel modulation and demodulation schemes, such as multi-carrier transmission, are effective in high-speed digital mobile communications. This paper proposed a smooth envelope parallel modulation and demodulation scheme. The proposed scheme can be applied to two systems, a multi-carrier system and a multi-code system. The systems with 4 carriers and 4 codes achieve the peak suppression of 2 dB and 4 dB, respectively. Because the receivers of the systems employ the MLSE scheme, the BER performance is nearly equal to that of the systems without suppression.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes Coherent-HYBrid Direct-Sequence Fast-Frequency-Hopping (CHYB-DS-FFH) CDMA with Adaptive Interference Cancelling (AIC) for cellular mobile communications. The features of CHYB-DS-FFH are symbol-by-symbol frequency diversity and low chip-rate DS multiplexing; both of which are based on a coherent FFH modulation and demodulation scheme. The combination of coherent FFH, space diversity, and AIC is very effective for reducing the performance degradation due to interference. Computer simulations demonstrate BER performance of a 2 hop 500-kHz-interval frequency hopping system using (i) a linear canceller or (ii) a nonlinear canceller. Both systems employ the two branch space diversity reception of 10 kb/s QPSK with FFH over a 1 MHz system bandwidth. In quasi-static channels, the average BER performance is 10^&lt-2&gt with average E_b/N_o less than 8dB. In dynamic fading channels under full interference conditions, CHYB-DS-FFH with the linear adaptive interference canceller realizes a BER of 10^&lt-2&gt at the average E_b/N_o of 15 dB with maximum Doppler frequency f_D of 5 Hz, whereas CHYB-DS-FFH with the non-linear adaptive interference canceller achieves the same BER at the average E_b/N_o of 15 dB with f_D equal to 30 Hz.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes Code Frequency Division Multiple Access(CFDMA)generalized from Coherent Hybrid DS-FFH CDMA,and derives various types of transmission channels from CFDMA.Among CFDMA,Interleaved Frequency Hopping(IFH)is superior to the others in tracking the fading,and computer simulation verifies the performance.In fading channels,IFH of chip number K=2 achieves average BER of 10^-2> at 15 dB average E_b, N_O and 60 Hz maximum Doppler frequency f_D under full co-channel interference condition. IFH of K=4 achieves the BER at f_D=300 Hz under half co-channel interference condition.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes Coherent-HYBrid Direct-Sequence Fast- Frequency-Hopping(CHYB-DS-FFH) CDMA with Non-Linear Adaptive Interference Canceller(NL-AIC)for mobile radio communications.BER performance in Rayleigh fading environments is calculated by computer simulations.In quasi-static channels,average E_b, N_0 for achieving BER=10^-2> of NL-AIC is better than that of a linear AIC by 8 dB under a co-channel interference condition.In dynamic fading channels,CHYB-DS-FFH with NL-AIC achieves average BER of 10^ -2> at average E_b/N_0 of 15 dB at maximum Doppler frequency of 30 Hz under a co-channel interference condition.

CiNii Article

CiNii Books

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Event date： 2023.11.25 - 2023.11.26

Presentation type：Poster presentation  

researchmap

Event date： 2023.11.25 - 2023.11.26

Presentation type：Poster presentation  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.10.28

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.7.20 - 2023.7.21

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.6.12

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.3.1 - 2023.3.3

Presentation type：Oral presentation (general)  

researchmap

Event date： 2023.3

researchmap

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.11.19 - 2022.11.20

Language：Japanese   Presentation type：Poster presentation  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.10.22

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.9.6 - 2022.9.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.9.6 - 2022.9.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.9.6 - 2022.9.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.9.6 - 2022.9.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.9.6 - 2022.9.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.9.6 - 2022.9.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.3.15 - 2022.3.18

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.3.15 - 2022.3.18

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.3.15 - 2022.3.18

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.3.15 - 2022.3.18

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.3.15 - 2022.3.18

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.3.15 - 2022.3.18

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.11.27 - 2021.11.28

Language：Japanese   Presentation type：Poster presentation  

researchmap

Event date： 2021.10.23

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.10.23

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.10.23

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.10.23

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.10.23

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.3.9 - 2021.3.12

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.3.9 - 2021.3.12

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap