Details of a Researcher - Sanada, Yukitoshi

Papers - Sanada, Yukitoshi

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Miniaturization and Test Results of Shinkansen Antenna for Overhead Line Voltage Detection and Wireless Communication

MATSUMURA Yoshihiro, NISHIYAMA Takeshi, SASAKI Eishi, NISHIMOTO Kengo, AKUTSU Hiroyuki, SANADA Yukitoshi

電子情報通信学会論文誌B 通信 (電子情報通信学会) J104-B ( 1 ) 42 - 53 2021.01

The Shinkansen antenna for overhead line voltage detection and wireless communication antenna has both the function of detecting the overhead line voltage of 60 Hz and the function of wireless communication in the VHF band. The antenna installed on the roof of the leading car on the Tokaido Shinkansen has been unchanged since its opening, despite being one of the sources of noise. In order to reduce noise, it is necessary to shorten the detection rod that detects overhead line voltage. Therefore, we propose a miniaturized antenna configuration that uses a folded monopole structure and a parallel resonant circuit. When the detection rod is shortened, the performance of overhead line voltage detection deteriorates, but the deterioration is minimized by making the antenna substrate area as large as possible within the antenna radome shape that reduces noise. We confirm the effectiveness of the proposed antenna by simulations and measurements. Moreover, we investigate the influence of the snow and rain, and show the results evaluated by running test.

Forcible search with mixed gibbs sampling massive MIMO detection

Yamazaki K., Sanada Y.

IEEE Region 10 Annual International Conference, Proceedings/TENCON (IEEE Region 10 Annual International Conference, Proceedings/TENCON) 2020-November 292 - 296 2020.11

ISSN 9781728184555

In this paper, mixed Gibbs sampling multiple- input multiple-output (MIMO) detection with forcible search is proposed. In conventional Gibbs sampling MIMO detection, the problem of stalling occurs under high signal-to-noise ratios (SNRs) which degrades the detection performance. Mixed GS (MGS) is one solution to this problem. In the MGS, random sampling is carried out with a constant probability without judging if a current search is at a local minimum. In the proposed scheme, combined with MGS, multiple candidate symbols are forcibly changed when the search is captured by a local minimum. The search restarts away from the local minimum which effectively enlarges the search area in a solution space. Numerical results obtained through computer simulation show that the proposed scheme achieves better performance in a large scale MIMO system with QPSK signals.

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MIMO detection with block parallel gibbs sampling and maximum ratio combining

Tomura K., Sanada Y., Kobayashi Y.

IEEE Region 10 Annual International Conference, Proceedings/TENCON (IEEE Region 10 Annual International Conference, Proceedings/TENCON) 2020-November 496 - 500 2020.11

ISSN 9781728184555

In this paper, block parallel Gibbs sampling (BPGS) multiple-input multiple-output (MIMO) detection is proposed. In a conventional Gibbs sampling scheme, MIMO detection is carried out sequentially symbol-by-symbol. The proposed scheme divides a symbol vector to blocks and updates candidate transmit symbols in parallel in a block so that the total number of iterations in a unit period increases. Furthermore, maximum ratio combining (MRC) is adopted to BPGS to improve accuracy in this paper. Numerical results obtained through computer simulations show that bit error rate performance under high bit-energy-to-noise-spectrum-density conditions improves with the proposed scheme. It is also shown that the block size of three achieves the best performance when number of antennas is 16×16 and the number of iterations is 50.

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Performance evaluation of miniaturized antenna of the shinkansen used for overhead line voltage detection and wireless communication

Matsumura Y., Sasaki E., Nishiyama T., Nishimoto K., Akutsu H., Sanada Y.

International Symposium on Wireless Personal Multimedia Communications, WPMC (International Symposium on Wireless Personal Multimedia Communications, WPMC) 2020-October 2020.10

ISSN 9781728182964

Reducing the noise from the sound of train travel is an important issue in high-speed railways such as the Shinkansen. There has been no change in the shape of the antenna installed on the roof on the leading car of the Tokaido Shinkansen since the line started service, even though this is a source of the noise. Here, by changing (miniaturizing) the shape of this antenna from the standpoint of noise countermeasures, we developed an antenna that satisfied both the overhead line voltage detection performance and wireless detection performance, analyzed its performance by examination in factory and running tests, and confirmed that it can be provided for practical use. In this paper, we report a summary of the antenna, the results of the performance evaluation under environments of rain and accumulated snow, and the results of performance evaluation by running tests.

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Phase selection in round-robin scheduling sequence for distributed antenna system

Otsuru G., Sanada Y.

IEICE Transactions on Communications (IEICE Transactions on Communications) E103B ( 10 ) 1155 - 1163 2020.10

ISSN 09168516

One of key technologies in the fifth generation mobile communications is a distributed antenna system (DAS). As DAS creates tightly packed antenna arrangements, inter-user interference degrades its spectrum efficiency. Round-robin (RR) scheduling is known as a scheme that achieves a good trade-off between computational complexity and spectrum efficiency. This paper proposes a user equipment (UE) allocation scheme for RR scheduling. The proposed scheme offers low complexity as the phase of UE allocation sequences are predetermined. Four different phase selection criteria are compared in this paper. Numerical results obtained through computer simulation show that maximum selection, which sequentially searches for the phase with the maximum tentative throughput realizes the best spectrum efficiency next to full search. There is an optimum number of UEs which obtains the largest throughput in single-user allocation while the system throughput improves as the number of UEs increases in 2-user RR scheduling.

Low Complexity Belief Propagation based MIMO Detection with MMSE Pre-cancellation for Overloaded MIMO systems

Imamura T., Sanada Y.

IEEE Vehicular Technology Conference (IEEE Vehicular Technology Conference) 2020.09

Last author

In this paper, the application of minimum mean square error (MMSE) pre-cancellation prior to belief propagation (BP) is proposed as a detection scheme for overloaded multiple-input multiple-output (MIMO). In overloaded MIMO, the loops in a factor graph deteriorate the demodulation performance with BP. Therefore, the proposed scheme applies the MMSE pre-cancellation prior to BP and reduces the number of the loops. Furthermore, it is applied to the selected transmit and receive nodes so that the condition number of an inverse matrix in the MMSE weight matrix is minimized in order to suppress the residual interference and the noise after the MMSE precancellation. It is shown by numerical results obtained through computer simulation that the proposed scheme achieves better bit error rate (BER) performance than BP without the MMSE pre-cancellation. The proposed scheme improves the BER performance by 4.6-5.0 dB at a BER of 5.0 × 10-3 as compared with conventional BP. Numerical results also shows that the MMSE pre-cancellation reduces the complexity in BP by a factor of 1/896 in terms of the number of multiplication operations.

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Novel approximated zero forcing pre-coding technique with threshold for diffusion based molecular communication

Sohail Ahsan, Sanada Yukitoshi

IEICE Communications Express (一般社団法人電子情報通信学会) 9 ( 7 ) 348 - 353 2020.07

ISSN 2187-0136

This letter proposes approximated zero forcing precoding with a threshold in molecular communication (MC). Frequency domain precoding for channel equalization is investigated. Owing to the restriction of a transmitter in MC the main part of an equalized waveform is extracted and a corresponding rectangular waveform is transmitted. In the proposed equalization scheme, the frequency component of the transmit signal is suppressed if a threshold exceeds the channel coefficient in the proposed scheme. Numerical results obtained through computer simulation show that approximation by a single rectangular waveform achieves almost the same performance as that with rectangular approximation that suppresses inter-symbol interference with the proposed precoding technique.

Precoder Design Algorithm using Spatial Signal Synthesis with Multiple Antenna Subset Selection for Hybrid MIMO System

Tamate D., Sanada Y.

IEEE Vehicular Technology Conference (IEEE Vehicular Technology Conference) 2020-May 2020.05

ISSN 9781728152073

In this paper, a precoder design algorithm using spatial signal synthesis with selected multiple antenna subsets for hybrid multiple-input multiple-out-put (MIMO) systems is proposed. The hybrid MIMO systems are expected to be implemented in high frequency bands. To reduce power consumption and increase the bandwidth of a transmit signal, the resolution of phase shifters and the number of quantization levels in digital-analog (D/A) converters have to be limited. A baseband precoder needs to take the effect of quantization into account. On the other hand, when the number of transmit antennas is larger than that of receive antennas, spatial signal synthesis can be realized. The selection of antenna sets also needs to take the effect of quantization into account. In this paper, a transmit antenna selection scheme that improves the spectral efficiency by spatial signal synthesis with multiple antenna subsets is proposed. Numerical results obtained through computer simulation show that the proposed scheme with two antenna subsets of four transmit antennas and two receive antennas improves the spectrum efficiency by about 1.0 bit/s/Hz when the number of transmit and receive are 4.

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Novel frequency domain equalization with threshold for molecular communication

Sohail Ahsan, Sanada Yukitoshi

IEICE Communications Express (一般社団法人電子情報通信学会) 9 ( 2 ) 36 - 41 2020.02

ISSN 2187-0136

This letter proposes a frequency domain equalization (FDE) scheme with a threshold in molecular communication (MC). The responses of a MC channel are tendency to have low pass characteristics and inter-symbol interference limits the data rates of MC. However, because of the characteristics of the MC channel, equalization coefficients for high frequency components may increase. Therefore, noise enhancement occurs and it deteriorates communication performance. As large channel responses concentrate at around a zero-frequency component, in the proposed equalization scheme, the high frequency component of the received signal is eliminated if the equalization coefficient exceeds a threshold in the proposed scheme. Numerical results obtained through computer simulation show that the threshold improves the communication performance with the proposed FDE. It is also shown that the trade-off between the noise enhancement and the pulse waveform effects on the performance.

Detection schemes for massive MIMO system with low-resolution ADCs

Gao Peng, Sanada Yukitoshi

IEICE Communications Express (一般社団法人電子情報通信学会) 8 ( 10 ) 422 - 427 2019.10

ISSN 2187-0136

In a full-digital massive multi-user MIMO system, maximal-ratio combining (MRC) can obtain more considerable diversity gain while inter-stream interference (ISI) and multi-user interference (MUI) can be canceled using minimum mean square error (MMSE) algorithm. This letter evaluates the throughputs of detection schemes for different antenna numbers in the massive MIMO system with low-resolution analog-to-digital converters (ADCs). The letter makes a comparison between MRC and MMSE under quantization range limit. Numerical results show that MRC achieves better system performance with lower implementation complexity as the number of antennas increases.

Convergence improvement in repeating weighted boosting search algorithm for channel estimation

Taniguchi Y., Sanada Y.

IEEE Vehicular Technology Conference (IEEE Vehicular Technology Conference) 2019-September 2019.09

ISSN 9781728112206

The fifth generation mobile communication systems are expected to support the Internet-of-Things (IoT) applications. One of the problems in massive connections is the assignment of pilot sequences. For supporting a large number of the IoT devices, non- orthogonal sequences have to be assigned and a receiver in a base station needs to estimate channel impulse responses (CIRs) by solving a joint optimization problem. In this paper, a new channel estimation scheme for the IoT devices is proposed. The proposed scheme is based on a repeating weighted boosting search algorithm and modifies the generation process of candidate CIR vectors for faster convergence in search iterations. Instead of calculating the sum of weighted candidate CIR vectors, the proposed scheme generates a candidate CIR vector that is assumed to be closer to the global optimum. In this case, the proposed scheme improves the convergence rate as compared to the conventional scheme though the mean square errors (MSE) of the solutions is worse. If the number of subcarriers is limited, the MSE of the estimated CIR vectors with the proposed algorithm is equivalent to that with the conventional scheme. Thus, the proposed scheme is less complex and suitable for massive connections. Numerical results obtained through computer simulation have shown that the proposed scheme achieves faster convergence by about 17-35% as compared to the conventional scheme.

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Latency of uplink non-orthogonal multiple access grant-free transmission with multiuser detection in base station

Shiono S., Sanada Y., Kimura R., Matsuda H., Sawai R.

IEEE Vehicular Technology Conference (IEEE Vehicular Technology Conference) 2019-September 2019.09

ISSN 9781728112206

In this paper, the latency of non-orthogonal multiple access (NOMA) grant-free (GF) transmission in uplink is evaluated by link and system level simulations. In order to cancel interference among NOMA signals, multiuser detection (MUD) consisting of minimum mean square error demodulation followed by successive interference cancellation is applied. Retransmission happens only when a packet error occurs after serial interference cancellation (SIC). Therefore, the latency is reduced as compared to GF transmission without MUD. Numerical results obtained through system level simulation show that the application of MUD in uplink GF transmission improves the latency and increases the successful transmission rate without retransmission by a factor of about 3.0.

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User allocation with round-robin scheduling sequence for distributed antenna system

Otsuru G., Sanada Y.

IEEE Vehicular Technology Conference (IEEE Vehicular Technology Conference) 2019-September 2019.09

ISSN 9781728112206

One of key technologies in the fifth generation mobile communications is a distributed antenna system (DAS). In the DAS inter-user interference effects on its spectrum efficiency as distributed antennas are located closely. Round-robin (RR) scheduling is known as a scheme that achieves a trade-off between computational complexity and spectrum efficiency. In this research user equipment (UE) allocation scheme for RR scheduling are proposed. The proposed scheme determines the phases of UE allocation sequence that is pre-determined for low complexity. Numerical results obtained through computer simulation have shown that maximum selection that sequentially searches the phase with the maximum tentative throughput realizes the largest spectrum efficiency next to full search. The system throughput increases as the number of UEs increases in 2-user RR scheduling.

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Effect of quantization range limit for low-resolution analog-to-digital converters in full-digital massive MIMO system

Gao P., Sanada Y.

Proceedings - 2019 IEEE VTS Asia Pacific Wireless Communications Symposium, APWCS 2019 (Proceedings - 2019 IEEE VTS Asia Pacific Wireless Communications Symposium, APWCS 2019) 2019.08

ISSN 9781728112046

Low-resolution analog-to-digital converters (ADCs) may need to be implemented in a full-digital massive multi-user MIMO system for low-power consumption. In this paper, the performance with a proposed ADC design for low-resolution ADCs to suppress the amount of degradation due to the quantization process in the full-digital massive multi-user MIMO system is evaluated. In the proposed ADC design, quantization range limit is specified based on the mean amplitude of a received signal and the input amplitude is bounded to eliminate thermal noise. Numerical results show that, through clipping the thermal noise by setting the appropriate quantization range limit, the full-digital massive MIMO with low-resolution ADCs (even 1-bit ADCs) realizes better system throughput than that with infinite-resolution ADCs. It is also shown that the throughput with low-resolution ADCs is equivalent to that with infinite-resolution ADCs when the number of users is less than three (the number of streams is less than six).

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Quantized Precoding using Gibbs Sampling in Massive MIMO Downlink

Okawa R., Sanada Y.

Proceedings - 2019 IEEE VTS Asia Pacific Wireless Communications Symposium, APWCS 2019 (Proceedings - 2019 IEEE VTS Asia Pacific Wireless Communications Symposium, APWCS 2019) 2019.08

ISSN 9781728112046

The sum rate performance of quantized precoding using Gibbs sampling is evaluated in a massive multiple-input multiple-output (MIMO) system in this paper. The massive MIMO is a promising technique to improve spectrum efficiency and energy efficiency. In a full digital massive MIMO system, however, the resolution of digital-to-analogue converters (DACs) in transmit antenna branches have to be low enough because of their power consumption. Therefore, quantized precoding or precoding with the low resolution DACs is investigated. A conventional optimization criterion minimizes errors between a desired received signal and a designed signal. However, the system sum rate may decrease as it increases transmit power. This paper proposes two optimization criteria that take not only the errors but also the transmit power into account to select the candidate quantized transmit signal in order to maximize the sum rate. Moreover, Gibbs sampling is applied to obtain the suboptimal solution of the optimization problem. Numerical results obtained through computer simulation show that the proposed sum rate based criterion for the optimization achieves the approximately 1.3 times higher sum rate than the conventional criterion on a Rician fading channel. On the other hand, the proposed symbol-power-to-mean-square-error ratio (SMSER) based criterion shows faster optimization convergence.

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Effect of Joint Detection on System Throughput in Distributed Antenna Network

Ishikawa Haruya, Sanada Yukitoshi

IEICE TRANSACTIONS ON COMMUNICATIONS E102B ( 3 ) 641 - 647 2019.03

ISSN 0916-8516

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Mixed Gibbs sampling iterative MIMO detection and decoding with maximum ratio combining

Kobayashi Y., Sanada Y.

2019 URSI Asia-Pacific Radio Science Conference, AP-RASC 2019 (2019 URSI Asia-Pacific Radio Science Conference, AP-RASC 2019) 2019.03

ISSN 9789082598759

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Non-orthogonal multiple access with joint maximum likelihood detection in heterogeneous network

Sanada Yukitoshi

EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING (Eurasip Journal on Wireless Communications and Networking) 2018 ( 1 ) 2018.12

ISSN 1687-1472

As one of the key technologies in the fifth-generation mobile communication system, non-orthogonal multiple access (NOMA) has been investigated. In NOMA, multiple terminals are assigned the same frequency resources by a scheduler on the basis of the difference in propagation losses between a base station and user terminals. Each terminal cancels the signals for the other terminals and extracts its desired signal. On the other hand, the application of joint maximum likelihood (ML) detection to overloaded signals has also been investigated, and joint ML detection can be applied to a NOMA downlink. In this paper, the effect of joint ML detection in a heterogeneous NOMA network is presented. The numerical results obtained through system-level simulation show that joint ML detection in a heterogeneous NOMA downlink can effectively offload mobile traffic from a macro base station to a pico base station. It is shown that a heterogeneous NOMA network with joint ML detection improves the throughput performance by 0.2 bit/user/subcarrier as compared to that without joint ML detection at a cumulative probability of 0.5. The system throughput is also increased about twofold with joint ML detection.

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Performance of MMSE interference rejection followed by joint MLD for DAN

Miyagi H., Sanada Y.

IEICE Transactions on Communications (IEICE Transactions on Communications) E101B ( 12 ) 2471 - 2478 2018.12

ISSN 09168516

Copyright © 2018 The Institute of Electronics, Information and Communication Engineers. This paper applies minimum mean square error (MMSE) interference rejection followed by joint maximum likelihood detection (MLD) to a receiver in a distributed antenna network (DAN).DANreceivers capture not only the desired signals, but also the interference signals from nearby uncoordinated antennas. For the overloaded signal situation, nonlinear detection schemes such as joint MLD can be applied to the received signals. However, the amount of metric calculations in joint MLD increases exponentially with the number of signal streams. Therefore, MMSE interference rejection followed by MLD detection is proposed. The proposed scheme reduces the complexity by a factor of 1=2M (NT -1) where NT is the number of interference signals with 2MQAM modulation. The effect of residual interference after the MMSE interference rejection is evaluated. Numerical results obtained through computer simulation and experiment show that the performance of the proposed scheme is about 4:0 dB worse at a bit error rate (BER) of 10-3 than that of the joint MLD while its complexity is four times lower for QPSK signal streams. The BER performance degradation can be suppressed to about 2:5 dB by adjusting the value of the coefficient in the MMSE matrix.

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MU-MIMO-OFDM with Analog Beamforming and Spreading Codes for User Separation

Nakahara K., Terui K., Sanada Y.

ISPACS 2018 - 2018 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS 2018 - 2018 International Symposium on Intelligent Signal Processing and Communication Systems) 96 - 101 2018.11

ISSN 9781538657713

This paper presents a multiuser (MU)-multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) scheme that realizes signal separation among mobile terminals by spreading codes on top of analog beamforming with analog-digital hybrid massive MIMO. Multiuser MIMO scheme suffers from interference among terminals caused by inaccurate information of channel responses. The channel state information (CSI) of the terminals are outdated owing to a Doppler shift if there is a time lag between channel estimation and CSI feedback. Thus, this paper proposes an MU-MIMO-OFDM scheme with analog-digital hybrid massive MIMO and orthogonal spreading codes that separates signals for mobile terminals. Numerical results obtained through computer simulation show that on WINNER II Umi NLOS channel the proposed scheme improves bit error rate (BER) performance by 1.0dB at a bit error rate of 10 in comparison with the conventional MU-MIMO. -3

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