論文 - 眞田　幸俊

Gradient Descent Direction Random Walk MIMO Detection using Intermediate Search Point

ITO Naoki, SANADA Yukitoshi

（ICETC 2022）  2022年11月

研究論文（国際会議プロシーディングス）, 共著, 最終著者, 査読有り

Reduction of Out-of-Band Radiation with Quantized Precoding using Gibbs Sampling in Massive MU-MIMO-OFDM

YAMAKADO Taichi, OKAWA Riki, SANADA Yukitoshi

IEICE Transactions on Communications （一般社団法人 電子情報通信学会）  E105-B （ 10 ） 1240 - 1248 2022年10月

研究論文（学術雑誌）, 査読有り,  ISSN  0916-8516

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Pilot Signal Design for Mixed Numerology NOMA Transmission

Kanke H., Sanada Y., Matsuda H., Takahashi M., Kimura R.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2022-September 2022年09月

研究論文（国際会議プロシーディングス）, 査読有り,  ISSN  15502252

　概要を見る

In the fifth-generation mobile communication system (5G) mixed numerology is standardized to meet the requirements of various services. In this paper, mixed numerology signal transmission in which multiple signals with different numerologies is assumed. As a conventional pilot signal, demodulation reference signal (DMRS) in a forth generation mobile communication (4G) is applied. However, under mixed numerology non-orthogonal multiple access (NOMA), DMRS can not realize orthogonality between pilot signals. As a solution, new pilot signal design based on a Zadoff-Chu sequence is proposed. The proposed pilot signal assignment scheme improves orthogonality between signals with different numerologies and, as a result, reduces bit error rate (BER) performance. Numerical results obtained through computer simulation show that the proposed pilot signal assignment scheme improves the performance by about 2.0 dB at a BER of 10{-2}.

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User Scheduling at Base Station Cluster Boundary for Massive MIMO Downlink Transmission

YATA Masahito, SANADA Yukitoshi

（URSI-JSRM 2022）  2022年09月

最終著者

Performance of Cell-Free Distributed Antenna System with Adaptive-Resolution ADCs

Gao P., Sanada Y.

ITE Transactions on Media Technology and Applications （ITE Transactions on Media Technology and Applications）  10 （ 3 ） 90 - 99 2022年07月

ISSN  2186-7364

　概要を見る

In this paper, we propose a cell-free distributed antenna system (DAS) architecture with adaptive resolution- (AR-) analog-to-digital converters (ADCs) in access points (APs). The proposed scheme adopts accurate models of the combined effects of clipping, quantization, and thermal noise in the ADC to analyze the quantization characteristics with different resolutions at different received signal-to-interference-and-noise ratios (SINRs). The proposed resolution bit selection criterion of the AR-ADC scheme is then applied. The AR-ADC scheme is to minimize the ADC resolution bits under allowable quantization distortion, and obtain the corresponding optimal clipping factor of the signal-to-interference-plus-quantization-and-noise ratio (SIQNR) for the desired received signal. The contributions of this paper are as follows; 1) the AR-ADC scheme provides a receiver architecture that realizes better energy efficiency (EE), 2) the spectral efficiency (SE) performance is improved by allocating more resolution bits to the APs closer to each UE with the proposed criterion. Numerical results demonstrate that the proposed AR-ADC scheme improves the EE more than tenfold as compared with the other schemes except the system with only 1−bit ADCs. Moreover, the proposed AR-ADC doubles the SE as compared with the system with only 1−bit ADCs.

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BP MIMO Detection with MMSE Pre-cancellation Sub-matrix Switching

Imamura T., Sanada Y.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2022-June 2022年05月

ISSN  15502252

　概要を見る

In this paper, belief propagation (BP) multiple-input multiple-output (MIMO) detection with minimum mean square error (MMSE) pre-cancellation matrix switching in overloaded MIMO systems is proposed. Loops in a factor graph degrades the demodulation performance of the BP scheme. Therefore, several schemes that suppresses the negative impact of loopy BP have been proposed. Among them, the application of MMSE pre-cancellation prior to BP has been proposed. In the scheme, the effects of loops in the factor graph is suppressed by MMSE pre-cancellation. However, many loops with large coefficients remain in the factor graph even after MMSE pre-cancellation. Therefore, the proposed scheme applies MMSE pre-cancellation matrix switching every after a preset number of BP iterations in order to suppress the occurrence of large beliefs in the loops. Numerical results obtained through computer simulation show that the proposed scheme achieves better BER performance than BP with MMSE pre-cancellation without matrix switching. The proposed scheme outperforms the conventional without switching by 0.7 dB at BER= 10-3.

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Macro Cell Switching of Transmit Antennas in Distributed Antenna Transmission

Tsukamoto Takahito, Otsuru Go, Sanada Yukitoshi

IEICE TRANSACTIONS ON COMMUNICATIONS （一般社団法人 電子情報通信学会）  E105.B （ 3 ） 302 - 308 2022年03月

ISSN  0916-8516

　概要を見る

<p>In this paper, a macro cell switching scheme for distributed antennas is proposed. In conventional distributed antenna transmission (DAT), the macro cell to which each antenna belongs is fixed. Though a cell-free system has been investigated because of its higher system throughput, the implementation cost of front-hauls can be excessive. To increase the flexibility of resource allocation in the DAT with moderate front-haul complexity, we propose the macro cell switching of distributed antennas (DAs). In the proposed scheme, DAs switch their attribution macro cells depending on the amount of pre-assigned connections. Numerical results obtained through computer simulation show that the proposed scheme realizes a better system throughput than the conventional system, especially when the number of user equipments (UEs) is smaller and the distance between DAs are larger.</p>

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ミリ波の新幹線環境での活用を想定した45 GHz帯伝搬特性の曲線区間での測定・解析及び適切な地上局配置間隔

松村 善洋, 丹下 智之, 西山 武志, 笹木 栄志, 岩本 功貴, 中村 一城, 荒川 智樹, 井倉 裕之, 眞田 幸俊

電子情報通信学会論文誌B 通信 （電子情報通信学会）  J105-B （ 3 ） 362 - 374 2022年03月

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Two-Stage Belief Propagation Detection with MMSE Pre-Cancellation for Overloaded MIMO

Shioi Risa, Imamura Takashi, Sanada Yukitoshi

IEICE TRANSACTIONS ON COMMUNICATIONS （一般社団法人 電子情報通信学会）  E105.B （ 3 ） 309 - 317 2022年03月

ISSN  0916-8516

　概要を見る

<p>In this paper, two-stage BP detection is proposed for overloaded MIMO. The proposal combines BP with the MMSE pre-cancellation algorithm followed by normal BP detection. In overloaded MIMO systems, the loops in a factor graph degrade the demodulation performance of BP detection. MMSE pre-cancellation reduces the number of connections or coefficient values in the factor graph which improves the convergence characteristics of posteriori probabilities. Numerical results obtained through computer simulation show that the BERs of the proposed two-stage BP detection outperforms the conventional BP with MMSE pre-cancellation in a low bit energy range when the MMSE block size is four and the number of MMSE blocks is one. When the pre-cancellation is applied for complexity reduction, the proposed scheme reduces multiplication operations and summation operations by the same factor of 0.7 though the amount of the performance improvement to the conventional scheme is limited.</p>

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Attribution Macro Cell Switching in Distributed Antenna Transmission

Tsukamoto T., Otsuru G., Sanada Y.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2021-September 2022年03月

ISSN  15502252

　概要を見る

In this paper, a macro cell switching scheme for distributed antennas is proposed. In conventional distributed antenna transmission (DAT), a macro cell to which each antenna belongs is fixed. Though a cell-free system has been investigated because of its higher system throughput, the complexity of front-haul can be inevitably large. To increase the flexibility of resource allocation in the DAT with moderate front-haul complexity, the macro cell switching of distributed antennas (DAs) is proposed. In the proposed scheme, DAs switch their attribution macro cells depending on the amount of pre-assigned resources. Numerical results obtained through computer simulation show that the proposed scheme realizes a better system throughput than the conventional system especially when the number of user equipments (UEs) is smaller.

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Power-Based Criteria for Signal Reconstruction using 1-bit Resolution DACs in Massive MU-MIMO OFDM Downlink

OKAWA Riki, SANADA Yukitoshi

IEICE Transactions on Communications （一般社団法人 電子情報通信学会）  2021年10月

ISSN  0916-8516

　概要を見る

<p>The sum rate and bit error rate (BER) performance of nonlinier quantized precoding using Gibbs sampling are evaluated in a massive multiuser multiple-input multiple-output (MU-MIMO) system in this paper. Massive MU-MIMO is a key technology to handle the growth of data traffic. In a full digital massive MU-MIMO system, however, the resolution of digital-to-analogue converters (DACs) in transmit antenna branches have to be low to yield acceptable power consumption. Thus, a combinational optimization problem is solved for the nonlinier quantized precoding to determine transmit signals from finite alphabets output from low resolution DACs. A conventional optimization criterion minimizes errors between desired signals and received signals at user equipments (UEs). However, the system sum rate may decrease as it increases the transmit power. This paper proposes two optimization criteria that take the transmit power into account in order to maximize the sum rate. Mixed Gibbs sampling is applied to obtain the suboptimal solution of the nonlinear optimization problem. Numerical results obtained through computer simulations show that the two proposed criteria achieve higher sum rates than the conventional criterion. On the other hand, the sum rate criterion achieves the largest sum rate while it leads to less throughputs than the MMSE criterion on approximately 60% of subcarriers.</p>

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Likelihood-based Metric for Gibbs Sampling Turbo MIMO Detection

KOBAYASHI Yutaro, SANADA Yukitoshi

IEICE Transactions on Communications （一般社団法人 電子情報通信学会）  2021年09月

ISSN  0916-8516

　概要を見る

<p>In a multiple-input multiple-output (MIMO) system, maximum likelihood detection (MLD) is the best demodulation scheme if no <i>a priori</i> information is available. However, the complexity of MLD increases exponentially with the number of signal streams. Therefore, various demodulation schemes with less complexity have been proposed and some of those schemes show performance close to that of MLD. One kind of those schemes uses a Gibbs sampling (GS) algorithm. GS MIMO detection that combines feedback from turbo decoding has been proposed. In this scheme, the accuracy of GS MIMO detection is improved by feeding back loglikelihood ratios (LLRs) from a turbo decoder. In this paper, GS MIMO detection using only feedback LLRs from a turbo decoder is proposed. Through extrinsic information transfer (EXIT) chart analysis, it is shown that the EXIT curves with and without metrics calculated from received signals overlap as the feedback LLR values increase. Therefore, the proposed scheme calculates the metrics from received signals only for the first GS MIMO detection and the selection probabilities of GS MIMO detection in the following iterations are calculated based only on the LLRs from turbo decoders. Numerical results obtained through computer simulation show that the performance of proposed GS turbo MIMO detection is worse than that of conventional GS turbo MIMO detection when the number of GS iterations is small. However the performance improves as the number of GS iterations increases. When the number of GS iterations is 30 or more, the bit error rate (BER) performance of the proposed scheme is equivalent to that of the conventional scheme. Therefore, the proposed scheme can reduce the computational complexity of selection probability calculation in GS turbo MIMO detection.</p>

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Weight Adjustment in Channel Estimation using Gibbs Sampling for MIMO Systems

Chuman K., Sanada Y.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2021-September 2021年09月

ISSN  15502252

　概要を見る

Channel estimation is required to demodulate the multiple-input multiple-output (MIMO) signals and there are blind and non-blind channel estimation schemes. One of non-blind channel estimation schemes is using Gibbs sampling. In channel estimation using Gibbs sampling, when the number of received data symbols is small, estimation accuracy may be deteriorated owing to the unreliability of weights. In order to solve this problem, this paper introduces a coefficient for adjusting the weights used in channel estimation with Gibbs sampling. When the number of data symbols is small, larger coefficient values are found to be more suitable because they suppress the fluctuation of channel estimation. Numerical results obtained though computer simulation show that the proposed scheme improves by about 5dB as compared with a decision directed scheme in a 4 × 4 MIMO system when the number of data symbols is one.

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Quantized Precoding for Out-of-Band Radiation Reduction in Massive MU-MIMO-OFDM

Yamakado T., Okawa R., Sanada Y.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2021-September 2021年09月

ISSN  15502252

　概要を見る

In this paper, a non-linear precoding algorithm with low out-of-band (OOB) radiation in a massive multiple-input multiple-output (MIMO) system is proposed. Massive MIMO is a system with more than a few hundred antennas implemented in a base station and is characterized by better spectral efficiency and higher throughput. Full digital massive MIMO may require lower resolution in digital-to-analog converters (DACs) since each high-resolution DAC consumes a large amount of power. In massive MIMO systems with low resolution DACs, an output signal designed by nonlinear processing has been investigated. The conventional scheme focuses only on a sum rate or errors in received signals and causes large OOB radiation. This paper proposes an optimization criterion that takes OOB radiation power into account. Gibbs sampling is used as an algorithm to search for a sub-optimal solution for this criterion. Numerical results obtained through computer simulation show that the proposed criterion reduces the mean OOB radiation power by a factor of 10 as compared with the conventional criteria. Furthermore, the proposed criterion achieves larger sum rate over all subcarriers as compared with an error based criterion. On the other hand, as compared with a sum rate based criterion, the throughput on each subcarrier shows less variation and that demands a smaller number of link adaptation options although the average sum rate of the proposed criterion is smaller.

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Two-Stage Belief Propagation Detection with MMSE Pre-Cancellation for Overloaded MIMO

Shioi R., Imamura T., Sanada Y.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2021-September 2021年09月

ISSN  15502252

　概要を見る

In this paper, two-stage BP detection is proposed for overloaded MIMO. In the two-stage BP detection scheme, the BP with MMSE pre-cancellation algorithm followed by the normal BP detection is applied. In overloaded MIMO systems, the loops in a factor graph degrade the demodulation performance of BP detection. MMSE pre-cancellation reduces the number of connections or coefficient values in the factor graph and improves the convergence characteristics of posteriori probabilities. Numerical results obtained through computer simulation have shown that the BERs of the proposed two-stage BP detection are about 1.0-1.5dB better than those of the conventional BP with MMSE pre-cancellation when the MMSE block size is four and the number of MMSE blocks is one.

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Performance of CRC-Aided Erasure Demodulation for M-ary Chirp Spread Spectrum Signal

Sanada Y., Ono T.

17th IEEE VTS Asia Pacific Wireless Communications Symposium, APWCS 2021 - Proceedings （17th IEEE VTS Asia Pacific Wireless Communications Symposium, APWCS 2021 - Proceedings）  2021年08月

　概要を見る

In this paper, erasure demodulation for an M-ary chirp spread spectrum signal is proposed. This demodulation scheme is assumed to be implemented in IoT devices to receive a deactivation command. In the erasure demodulation scheme a demodulator regards bit elements in a coded bit sequence as erasure if the corresponding correlator output is larger than a threshold and they are different from bit elements in a coded bit sequence for the maximum correlator output. Those erasure bits are treated as both "0"and "1"and cyclic redundancy check (CRC) decoding following the erasure demodulation checks which output is correct. As one of those outputs must be the same as the transmit coded bit, block error rate (BLER) performance improves. Even though the erasure demodulation increases the probability of false alarm, it can reduce the miss probability of deactivation. On the other hand, as the number of erasure bits increases, the number of CRC decoding operations grows exponentially and the probability of CRC miss detection also increases. Thus, the threshold level has to be decided according to the computational capability of each IoT device, the target BLER, and the probability of CRC miss detection. The performance of CRC miss detection and the BLER on a Rayleigh fading channel, a Rician fading channel, and a Vehicular-B channel are evaluated through computer simulation. Furthermore, cumulative distribution function curves for the number of erasure bits are also presented for different channel models.

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Forcible search scheme for mixed gibbs sampling massive mimo detection

YAMAZAKI K., SANADA Y.

IEICE Transactions on Communications （IEICE Transactions on Communications）  E104.B （ 4 ） 419 - 427 2021年04月

ISSN  09168516

　概要を見る

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 Gibbs sampling (MGS) is one solution to this problem. In MGS, random sampling is carried out with a constant probability regardless of whether a current search falls into 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 the 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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User scheduling with beam selection for full digital massive mimo base station

YATA M., OTSURU G., SANADA Y.

IEICE Transactions on Communications （IEICE Transactions on Communications）  E104.B （ 4 ） 428 - 435 2021年04月

ISSN  09168516

　概要を見る

In this paper, user scheduling with beam selection for fulldigital massive multi-input multi-output (MIMO) is proposed. Inter-user interference (IUI) can be canceled by precoding such as zero-forcing at a massive MIMO base station if ideal hardware implementation is assumed. However, owing to the non-ideal characteristics of hardware components, IUI occurs among multiple user terminals allocated on the same resource. Thus, in the proposed scheme, the directions of beams for allocated user terminals are adjusted to maximize the total user throughput. User allocation based on the user throughput after the adjustment of beam directivity is then carried out. Numerical results obtained through computer simulation show that when the number of user terminals in the cell is two and the number of user terminals allocated to one resource block (RB) is two, the throughput per subcarrier per subframe improves by about 3.0 bits. On the other hand, the fairness index (FI) is reduced by 0.03. This is because only the probability in the high throughput region increases as shown in the cumulative distribution function (CDF) of throughput per user. Also, as the number of user terminals in the cell increases, the amount of improvement in throughput decreases. As the number of allocated user terminals increases, more user terminals are allocated to the cell-edge, which reduces the average throughput.

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User Set Elimination in Allocation Sequences of RR Scheduling for Distributed Antenna Transmission

Otsuru G., Sanada Y.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference）  2021-April 2021年04月

ISSN  15502252

　概要を見る

In this paper, user set elimination in the allocation sequences of round-robin (RR) scheduling for distributed antenna transmission (DAT) is proposed. In prior research, the initial phase selection of the user equipment (UE) allocation sequences in RR scheduling has been investigated. However, all of UE sets are included without taking their throughputs into account. Thus, a UE set is assigned even through its total throughput is the lowest. The proposed scheme eliminates the specific UE sets from the RR scheduling sequence according to the expected total throughput of those UE sets. In addition, the initial phase selection is applied to the remaining UE sets. Numerical results obtained through computer simulation show that fairness index as well as system throughput improve when the ratio of eliminated UE sets is small.

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Low complexity overloaded MIMO detection based on belief propagation with MMSE pre-cancellation

Imamura T., Sanada Y.

IEICE Transactions on Communications （IEICE Transactions on Communications）  E104B （ 3 ） 312 - 319 2021年03月

ISSN  09168516

　概要を見る

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) systems. In overloaded MIMO systems, the loops in the factor graph degrade the demodulation performance of BP. Therefore, the proposed scheme applies MMSE pre-cancellation prior to BP and reduces the number of 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 to suppress the residual interference and the noise after MMSE pre-cancellation. Numerical results obtained through computer simulation show that the proposed scheme achieves better bit error rate (BER) performance than BP without MMSE pre-cancellation. The proposed scheme improves the BER performance by 2.9-5.6 dB at a BER of 5.0 × 10− compared with conventional BP. Numerical results also show that MMSE pre-cancellation reduces the complexity of BP by a factor of 896 in terms of the number of multiplication operations. 3

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