IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Advance online publication
Showing 1-50 articles out of 78 articles from Advance online publication
  • Zhiling XIAO, Zhenya YAN
    Type: PAPER
    Article ID: 2021EBP3035
    Published: 2021
    [Advance publication] Released: June 10, 2021
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    This article proposes to apply the auto-correlation function (ACF), bispectrum analysis, and convolutional neural networks (CNN) to implement radar emitter identification (REI) based on intrapulse features. In this work, we combine ACF with bispectrum for signal feature extraction. We first calculate the ACF of each emitter signal, and then the bispectrum of the ACF and obtain the spectrograms. The spectrum images are taken as the feature maps of the radar emitters and fed into the CNN classifier to realize automatic identification. We simulate signal samples of different modulation types in experiments. We also consider the feature extraction method directly using bispectrum analysis for comparison. The simulation results demonstrate that by combining ACF with bispectrum analysis, the proposed scheme can attain stronger robustness to noise, the spectrograms of our approach have more pronounced features, and our approach can achieve better identification performance at low signal-to-noise ratios.

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  • Shoji KASAHARA
    Type: INVITED PAPER
    Article ID: 2021ITI0003
    Published: 2021
    [Advance publication] Released: June 09, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Bitcoin is one of popular cryptocurrencies widely used over the world, and its blockchain technology has attracted considerable attention. In Bitcoin system, it has been reported that transactions are prioritized according to transaction fees, and that transactions with high priorities are likely to be confirmed faster than those with low priorities. In this paper, we consider performance modeling of Bitcoin-blockchain system in order to characterize the transaction-confirmation time. We first introduce the Bitcoin system, focusing on proof-of-work, the consensus mechanism of Bitcoin blockchain. Then, we show some queueing models and its analytical results, discussing the implications and insights obtained from the queueing models.

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  • Nobuyuki SHIRAKI, Naoki HONMA, Kentaro MURATA, Takeshi NAKAYAMA, Shoic ...
    Type: PAPER
    Article ID: 2020EBP3151
    Published: 2021
    [Advance publication] Released: June 04, 2021
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    This paper proposes a method for cooperative multi-static Multiple Input Multiple Output (MIMO) radar that can estimate the number of targets. The purpose of this system is to monitor humans in an indoor environment. First, target positions within the estimation range are roughly detected by the Capon method and the mode vector corresponding to the detected positions is calculated. The mode vector is multiplied by the eigenvector to eliminate the virtual image. The spectrum of the evaluation function is calculated from the remaining positions, and the number of peaks in the spectrum is defined as the number of targets. Experiments carried out in an indoor environment confirm that the proposed method can estimate the number of targets with high accuracy.

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  • Kazuya MATSUBAYASHI, Naobumi MICHISHITA, Hisashi MORISHITA
    Type: PAPER
    Article ID: 2020EBP3122
    Published: 2021
    [Advance publication] Released: June 01, 2021
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    The composite right/left-handed (CRLH) coaxial line (CL) with wideband electromagnetic band gap (EBG) is applied to the wideband choke structure for a monocone antenna with short elements, and the resulting characteristics are considered. In the proposed antenna, impedance matching and leakage current suppression can be achieved across a wideband off.The lowest frequency (|S11| ≤ -10 dB) of the proposed antenna is about the same as that of the monocone antenna on an infinite ground plane. In addition, the radiation patterns of the proposed antenna are close to the figure of eight in wideband. The proposed antenna is prototyped, and the validity of the simulation is verified through measurement.

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  • Hideya SO, Kazuhiko FUKAWA, Hayato SOYA, Yuyuan CHANG
    Type: PAPER
    Article ID: 2020EBP3150
    Published: 2021
    [Advance publication] Released: June 01, 2021
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    In unlicensed spectrum, wireless communications employing carrier sense multiple access with collision avoidance (CSMA/CA) suffer from longer transmission delay time as the number of user terminals (UTs) increases, because packet collisions are more likely to occur. To cope with this problem, this paper proposes a new multiuser detection (MUD) scheme that uses both request-to-send (RTS) and enhanced clear-to-send (eCTS) for high-reliable and low-latency wireless communications. As in conventional MUD scheme, the metric-combining MUD (MC-MUD) calculates log likelihood functions called metrics and accumulates the metrics for the maximum likelihood detection (MLD). To avoid increasing the number of states for MLD, MC-MUD forces the relevant UTs to retransmit their packets until all the collided packets are correctly detected, which requires a kind of central control and reduces the system throughput. To overcome these drawbacks, the proposed scheme, which is referred to as cancelling MC-MUD (CMC-MUD), deletes replicas of some of the collided packets from the received signals, once the packets are correctly detected during the retransmission. This cancellation enables new UTs to transmit their packets and then performs MLD without increasing the number of states, which improves the system throughput without increasing the complexity. In addition, the proposed scheme adopts RTS and eCTS. One UT that suffers from packet collision transmits RTS before the retransmission. Then, the corresponding access point (AP) transmits eCTS including addresses of the other UTs, which have experienced the same packet collision. To reproduce the same packet collision, these other UTs transmit their packets once they receive the eCTS. Computer simulations under one AP conditions evaluate an average carrier-to-interference ratio (CIR) range in which the proposed scheme is effective, and clarify that the transmission delay time of the proposed scheme is shorter than that of the conventional schemes. In two APs environments that can cause the hidden terminal problem, it is demonstrated that the proposed scheme achieves shorter transmission delay times than the conventional scheme with RTS and conventional CTS.

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  • Michiharu NAKAMURA, Eisuke FUKUDA, Yoshimasa DAIDO, Keiichi MIZUTANI, ...
    Type: PAPER
    Article ID: 2020EBP3155
    Published: 2021
    [Advance publication] Released: June 01, 2021
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    Non-linear behavioral models play a key role in designing digital pre-distorters (DPDs) for non-linear power amplifiers (NLPAs). In general, more complex behavioral models have better capability, but they should be converted into simpler versions to assist implementation. In this paper, a conversion from a complex fifth order inverse of a parallel Wiener (PRW) model to a simpler memory polynomial (MP) model is developed by using frequency domain expressions. In the developed conversion, parameters of the converted MP model are calculated from those of original fifth order inverse and frequency domain statistics of the transmit signal. Since the frequency domain statistics of the transmit signal can be precalculated, the developed conversion is deterministic, unlike the conventional conversion that identifies a converted model from lengthy input and output data. Computer simulations are conducted to confirm that conversion error is sufficiently small and the converted MP model offers equivalent pre-distortion to the original fifth order inverse.

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  • Xiang WANG, Xin LU, Meiming FU, Jiayi LIU, Hongyan YANG
    Type: PAPER
    Article ID: 2021EBP3013
    Published: 2021
    [Advance publication] Released: June 01, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Leveraging on Network Function Virtualization (NFV) and Software Defined Networking (SDN), network slicing (NS) is recognized as a key technology that enables the 5G Infrastructure Provider (InP) to support diversified vertical services over a shared common physical infrastructure. 5G end-to-end (E2E) NS is a logical virtual network that spans across the 5G network. Existing works on improving the reliability of the 5G mainly focus on reliable wireless communications, on the other hand, the reliability of an NS also refers to the ability of the NS system to provide continued service. Hence, in this work, we focus on enhancing the reliability of the NS to cope with physical network node failures, and we investigate the NS deployment problem to improve the reliability of the system represented by the NS. The reliability of an NS is enhanced by two means: firstly, by considering the topology information of an NS, critical virtual nodes are backed up to allow failure recovery; secondly, the embedding of the augmented NS virtual network is optimized for failure avoidance. We formulate the embedding of the augmented virtual network (AVN) to maximize the survivability of the NS system as the survivable AVN embedding (S-AVNE) problem through an Integer Linear Program (ILP) formulation. Due to the complexity of the problem, a heuristic algorithm is introduced. Finally, we conduct intensive simulations to evaluate the performance of our algorithm with regard to improving the reliability of the NS system.

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  • Hiroshi HASEGAWA, Takuma YASUDA, Yojiro MORI, Ken-ichi SATO
    Type: PAPER
    Article ID: 2021EBP3027
    Published: 2021
    [Advance publication] Released: June 01, 2021
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    We propose an efficient network upgrade and expansion method that can make the most of the next generation channel resources to accommodate further increases in traffic. Semi-flexible grid configuration and two cost metrics are introduced to establish a regularity in frequency assignment and minimize disturbance in the upgrade process; both reduce the fragmentation in frequency assignment and the number of fibers necessary. Various investigations of different configurations elucidate that the number of fibers necessary is reduced about 10-15% for any combination of upgrade scenario, channel frequency bandwidth, and topology adopted.

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  • Weiwei XIA, Zhuorui LAN, Lianfeng SHEN
    Type: PAPER
    Article ID: 2020EBP3171
    Published: 2021
    [Advance publication] Released: May 14, 2021
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    In this paper, we propose a hierarchical Stackelberg game based resource allocation algorithm (HGRAA) to jointly allocate the wireless and computational resources of a mobile edge computing (MEC) system. The proposed HGRAA is composed of two levels: the lower-level evolutionary game (LEG) minimizes the cost of mobile terminals (MTs), and the upper-level exact potential game (UEPG) maximizes the utility of MEC servers. At the lower-level, the MTs are divided into delay-sensitive MTs (DSMTs) and non-delay-sensitive MTs (NDSMTs) according to their different quality of service (QoS) requirements. The competition among DSMTs and NDSMTs in different service areas to share the limited available wireless and computational resources is formulated as a dynamic evolutionary game. The dynamic replicator is applied to obtain the evolutionary equilibrium so as to minimize the costs imposed on MTs. At the upper level, the exact potential game is formulated to solve the resource sharing problem among MEC servers and the resource sharing problem is transferred to nonlinear complementarity. The existence of Nash equilibrium (NE) is proved and is obtained through the Karush-Kuhn-Tucker (KKT) condition. Simulations illustrate that substantial performance improvements such as average utility and the resource utilization of MEC servers can be achieved by applying the proposed HGRAA. Moreover, the cost of MTs is significantly lower than other existing algorithms with the increasing size of input data, and the QoS requirements of different kinds of MTs are well guaranteed in terms of average delay and transmission data rate.

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  • Maodudul HASAN, Eisuke NISHIYAMA, Ichihiko TOYODA
    Type: PAPER
    Article ID: 2021EBP3003
    Published: 2021
    [Advance publication] Released: May 14, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    Herein, a novel self-oscillating active integrated array antenna (AIAA)is proposed for beam switching X-band applications. The proposed AIAA comprises four linearly polarized microstrip antenna elements, a Gunn oscillator, two planar magic-Ts, and two single-pole single-throw (SPST) switches. The in/anti-phase signal combination approach employing planar magic-Ts is adopted to attain bidirectional radiation patterns in the Φ = 90° plane with a simple structure. The proposed antenna can switch its beam using the SPST switches. The antenna is analyzed through simulations, and a prototype of the antenna is fabricated and tested to validate the concept. The proposed concept is found to be feasible; the prototype has an effective isotropic radiated power of +15.•98 dBm, radiated power level of +4.•28 dBm, and cross-polarization suppression of better than 15 dB. The measured radiation patterns are in good agreement with the simulation results.

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  • Hiroki KAWAHARA, Kyo INOUE, Koji IGARASHI
    Type: PAPER
    Article ID: 2021EBP3025
    Published: 2021
    [Advance publication] Released: May 14, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    This paper provides on a theoretical and numerical study of the probability density function (PDF) of the on-off keying (OOK) signals in ASE-limited systems. We present simple closed formulas of PDFs for the optical intensity and the received baseband signal. To confirm the validity of our model, the calculation results yielded by the proposed formulas are compared with those of numerical simulations and the conventional Gaussian model. Our theoretical and numerical results confirm that the signal distribution differs from a Gaussian profile. It is also demonstrated that our model can properly evaluate the signal distribution and the resultant BER performance, especially for systems with an optical bandwidth close to the receiver baseband width.

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  • Zihang SONG, Yue GAO, Rahim TAFAZOLLI
    Type: INVITED PAPER
    Article ID: 2020DSI0002
    Published: 2021
    [Advance publication] Released: April 26, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Cognitive radio provides a feasible solution for alleviating the lack of spectrum resources by enabling secondary users to access the unused spectrum dynamically. Spectrum sensing and learning, as the fundamental function for dynamic spectrum sharing in 5G evolution and 6G wireless systems, have been research hotspots worldwide. This paper reviews classic narrowband and wideband spectrum sensing and learning algorithms. The sub-sampling framework and recovery algorithms based on compressed sensing theory and their hardware implementation are discussed under the trend of high channel bandwidth and large capacity to be deployed in 5G evolution and 6G communication systems. This paper also investigates and summarizes the recent progress in machine learning for spectrum sensing technology.

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  • Lijun GAO, Zhenyi BIAN, Maode MA
    Type: PAPER
    Article ID: 2020EBP3192
    Published: 2021
    [Advance publication] Released: April 22, 2021
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    DoS (Denial of Service) attacks are becoming one of the most serious security threats to global networks. We analyze the existing DoS detection methods and defense mechanisms in depth. In recent years, K-Means and improved variants have been widely examined for security intrusion detection, but the detection accuracy to data is not satisfactory. In this paper we propose a multi-dimensional space feature vector expansion K-Means model to detect threats in the network environment. The model uses a genetic algorithm to optimize the weight of K-Means multi-dimensional space feature vector, which greatly improves the detection rate against 6 typical Dos attacks. Furthermore, in order to verify the correctness of the model, this paper conducts a simulation on the NSL-KDD data set. The results show that the algorithm of multi-dimensional space feature vectors expansion K-Means improves the recognition accuracy to 96.88%. Furthermore, 41 kinds of feature vectors in NSL-KDD are analyzed in detail according to a large number of experimental training. The feature vector of the probability positive return of security attack detection is accurately extracted, and a comparison chart is formed to support subsequent research. A theoretical analysis and experimental results show that the multi-dimensional space feature vector expansion K-Means algorithm has a good application in the detection of DDos attacks.

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  • Supraja Eduru, Nakkeeran Rangaswamy
    Type: PAPER
    Article ID: 2020EBP3161
    Published: 2021
    [Advance publication] Released: April 21, 2021
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    In this paper, the uplink performance of Multi-User Multiple Input Multiple Output (MU-MIMO) Zero Forcing (ZF) receiver is investigated over correlated Rayleigh fading channels with channel estimation error. A mathematical expression for the sub-streams' output Signal to Noise Ratio (SNR) with transmit and receive-correlation is derived in the presence of erroneous channel estimates. Besides, an approximate and accurate expression for the Bit Error Rate (BER) of ZF receiver for 16-Quadrature Amplitude Modulation (QAM) with transmit-correlation is deduced in terms of the hypergeometric function. Subsequently, the developed analytical BER is verified by Monte-Carlo trails accounting various system parameters. The simulation results indicate that ZF receiver's BER relies solely on the transmit-correlation for the same number of transmit and receive-antennas at higher average SNR values per transmitted symbol (EsN0). Also, a logarithmic and exponential growth in the BER is observed with an increase in the Mean Square estimation Error (MSE) and correlation coefficient, respectively.

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  • Kyo Inoue
    Type: PAPER
    Article ID: 2020EBP3173
    Published: 2021
    [Advance publication] Released: April 14, 2021
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    Quantum noise ultimately restricts the transmission distance in fiber communication systems using optical amplifiers. This paper investigates the quantum-noise-limited performance of optical binary phase-shift keying transmission using gain-saturated phase-sensitive amplifiers (PSAs) as optical repeaters. It is shown that coherent state transmission, where ultimately clean light in the classical sense is transmitted, and endless transmission, where the transmission distance is not restricted, are theoretically achievable under certain system conditions owing to the noise suppression effects of the gain-saturated PSA.

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  • Junxuan WANG, Meng YU, Xuewei ZHANG, Fan JIANG
    Type: PAPER
    Article ID: 2020EBP3118
    Published: 2021
    [Advance publication] Released: April 13, 2021
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    Heterogeneous networks (HetNets) are emerging as an inevitable method to tackle the capacity crunch of the cellular networks. Due to the complicated network environment and a large number of configured parameters, coverage and capacity optimization (CCO) is a challenging issue in heterogeneous cellular networks. By combining the self-optimizing algorithm for radio frequency (RF) parameters with the power control mechanism of small cells, the CCO problem of self-organizing network is addressed in this paper. First, the optimization of RF parameters is solved based on reinforcement learning (RL), where the base station is modeled as an agent that can learn effective strategies to control the tunable parameters by interacting with the surrounding environment. Second, the small cell can autonomously change the state of wireless transmission by comparing its distance from the user equipment with the virtual cell size. Simulation results show that the proposed algorithm can achieve better performance on user throughput compared to different conventional methods.

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  • Zhenyu ZHANG, Shaoli KANG, Bin REN, Xiang ZHANG
    Type: PAPER
    Article ID: 2020EBP3195
    Published: 2021
    [Advance publication] Released: April 12, 2021
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    Time of Arrival (TOA) is a widely used wireless cellular network ranging technology. How to perform accurate TOA estimation in multi-path and non-line-of-sight (NLOS) environments and then accurately calculating mobile terminal locations are two critical issues in positioning research. For NLOS identification, it can be performed in the TOA measurement part and the position calculation part, respectively. In this paper, for the above two steps, two schemes for mitigating NLOS errors are proposed. First of all, a TOA ranging method based on clustering theory is proposed to solve the problem of line of sight (LOS) path estimation in multi-path channels. We model TOA ranging as a Gaussian mixture model and illustrate how LOS and NLOS can be measured and identified based on non-parametric Bayesian methods when the wireless transmission environment is unknown. Moreover, for NLOS propagation channels, this paper proposes a user location estimator based on the maximum a posteriori (MAP) criterion. Combined with the TOA estimation and user location computation scheme proposed in this paper, the terminal's positioning accuracy is improved. Experiments show that the TOA measurement and localization algorithms presented in this paper have good robustness in complex wireless environments.

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  • Yue YIN, Haoze CHEN, Zongdian LI, Tao YU, Kei SAKAGUCHI
    Type: PAPER
    Article ID: 2020EBP3170
    Published: 2021
    [Advance publication] Released: April 09, 2021
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    Communication systems operating in the millimeter-wave (mmWave) band have the potential to realize ultra-high throughput and ultra-low latency vehicle-to-vehicle (V2V) communications in 5G and beyond wireless networks. Moreover, because of the weak penetration nature of mmWave, one mmWave channel can be reused in all V2V links, which improves the spectrum efficiency. Although the outstanding performance of the mmWave above has been widely acknowledged, there are still some shortcomings. One of the unavoidable defects is multipath interference. Even though the direct interference link cannot penetrate vehicle bodies, other interference degrades the throughput of the mmWave V2V communication. In this paper, we focus on the multipath interference caused by signal reflections from roads and surroundings, where the interference strength varies in road scenarios. Firstly, we analyze the multipath channel models of mmWave V2V with relay in three typical road scenarios (single straight roads, horizontal curves, and slopes). Their interference differences are clarified. Based on the analysis, a novel method of ZigZag antenna configuration is proposed to guarantee the required data rate. Secondly, the performance of the proposed method is evaluated by simulation. It proves that the ZigZag antenna configuration with an optimal antenna height can significantly suppress the destructive interference, and ensure a throughput over 1 Gbps comparing to the conventional antenna configuration at 60 GHz band. Furthermore, the effectiveness of ZigZag antenna configuration is demonstrated on a single straight road by outdoor experiments.

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  • Akio KAWABATA, Bijoy CHAND CHATTERJEE, Eiji OKI
    Type: PAPER
    Article ID: 2020EBP3178
    Published: 2021
    [Advance publication] Released: April 09, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In distributed processing for communication services, a proper server selection scheme is required to reduce delay by ensuring the event occurrence order. Although a conservative synchronization algorithm (CSA) has been used to achieve this goal, an optimistic synchronization algorithm (OSA) can be feasible for synchronizing distributed systems. In comparison with CSA, which reproduces events in occurrence order before processing applications, OSA can be feasible to realize low delay communication as the processing events arrive sequentially. This paper proposes an optimal server selection scheme that uses OSA for distributed processing systems to minimize end-to-end delay under the condition that maximum status holding time is limited. In other words, the end-to-end delay is minimized based on the allowed rollback time, which is given according to the application designing aspects and availability of computing resources. Numerical results indicate that the proposed scheme reduces the delay compared to the conventional scheme.

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  • Nobuhide Nonaka, Satoshi Suyama, Tatsuki Okuyama, Kazushi Muraoka, Yuk ...
    Type: PAPER
    Article ID: 2020FGT0002
    Published: 2021
    [Advance publication] Released: April 07, 2021
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    In order to realize the higher bit rates compared for the fifth-generation (5G) mobile communication system, massive MIMO technologies in higher frequency bands with wider bandwidth are being investigated for 5G evolution and 6G. One of practical method to realize massive MIMO in the high frequency bands is hybrid beamforming (BF). With this approach, user selection is an important function because its performance is highly affected by inter-user interference. However, the computational complexity of user selection in multi-user massive MIMO is high because MIMO channel matrix size excessive. Furthermore, satisfying user fairness by proportional fairness (PF) criteria leads to further increase of the complexity because re-calculation of precoding and postcoding matrices is required for each combination of selected users. To realize a fair and low-complexity user selection algorithm for multi-user massive MIMO employing hybrid BF, this paper proposes a two-step user selection algorithm that algorithm that combines PF based user selection and chordal distance user selection. Computer simulations show that the proposed two-step user selection algorithm with higher user fairness and lower computational complexity can achieve higher system performance than the conventional user selection algorithms.

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  • Riki OKAWA, Yukitoshi SANADA
    Type: PAPER
    Article ID: 2020EBP3133
    Published: 2021
    [Advance publication] Released: April 02, 2021
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    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.

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  • Yoichi MATSUO, Tatsuaki KIMURA, Ken NISHIMATSU
    Type: PAPER
    Article ID: 2020EBP3177
    Published: 2021
    [Advance publication] Released: April 01, 2021
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    When a failure occurs in a network element, such as switch, router, and server, network operators need to recognize the service impact, such as time to recovery from the failure or severity of the failure, since service impact is essential information for handling failures. In this paper, we propose Deep learning based Service Impact Prediction system (DeepSIP), which predicts the service impact of network failure in a network element using a temporal multimodal convolutional neural network (CNN). More precisely, DeepSIP predicts the time to recovery from the failure and the loss of traffic volume due to the failure in a network on the basis of information from syslog messages and traffic volume. Since the time to recovery is useful information for a service level agreement (SLA) and the loss of traffic volume is directly related to the severity of the failure, we regard the time to recovery and the loss of traffic volume as the service impact. The service impact is challenging to predict, since it depends on types of network failures and traffic volume when the failure occurs. Moreover, network elements do not explicitly contain any information about the service impact. To extract the type of network failures and predict the service impact, we use syslog messages and past traffic volume. However, syslog messages and traffic volume are also challenging to analyze because these data are multimodal, are strongly correlated, and have temporal dependencies. To extract useful features for prediction, we develop a temporal multimodal CNN.We experimentally evaluated DeepSIP in terms of accuracy by comparing it with other NN-based methods by using synthetic and real datasets. For both datasets, the results show that DeepSIP outperformed the baselines.

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  • Satoshi SUYAMA, Tatsuki OKUYAMA, Yoshihisa KISHIYAMA, Satoshi NAGATA, ...
    Type: INVITED PAPER
    Article ID: 2020FGI0002
    Published: 2021
    [Advance publication] Released: April 01, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In sixth-generation (6G) mobile communication system, it is expected that extreme high data rate communication with a peak data rate over 100 Gbps should be provided by exploiting higher frequency bands in addition to millimeter-wave bands such as 28 GHz. The higher frequency bands are assumed to be millimeter wave and terahertz wave where the extreme wider bandwidth is available compared with 5G, and hence 6G needs to promote research and development to exploit so-called terahertz wave targeting the frequency from 100 GHz to 300 GHz. In the terahertz wave, there are fundamental issues that rectilinearity and pathloss are higher than that in the 28 GHz band. In order to solve these issues, it is very important to clarify channel characteristics of the terahertz wave and establish a channel model, to advance 6G radio access technologies suitable for the terahertz wave based on the channel model, and to develop radio-frequency device technologies for such higher frequency bands. This paper introduces a direction of studies on 6G radio access technologies to explore the higher frequency bands and technical issues on the device technologies, and then basic computer simulations in 100 Gbps transmission using 100 GHz band clarify a potential of extreme high data rate over 100 Gbps.

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  • Nobuhide Nonaka, Kazushi Muraoka, Tatsuki Okuyama, Satoshi Suyama, Yuk ...
    Type: PAPER
    Article ID: 2020FGP0011
    Published: 2021
    [Advance publication] Released: April 01, 2021
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    In order to enhance the fifth generation (5G) mobile communication system further toward 5G Evolution, high bit-rate transmission using high SHF bands (28 GHz or EHF bands) should be more stable even in high-mobility environments such as high speed trains. Of particular importance, dynamic changes in the beam direction and the larger Doppler frequency shift can degrade transmission performances in such high frequency bands. Thus, we conduct the world's first 28 GHz-band 5G experimental trial on an actual Shinkansen running at a speed of 283 km/h in Japan. This paper introduces the 28 GHz-band experimental system used in the 5G experimental trial using the Shinkansen, and then it presents the experimental configuration in which three base stations (BSs) are deployed along the Tokaido Shinkansen railway and a mobile station is located in the train. In addition, transmission performances measured in this ultra high-mobility environment, show that a peak throughput of exceeding 1.0 Gbps and successful consecutive BS connection among the three BSs.

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  • Ryota OKUMURA, Keiichi MIZUTANI, Hiroshi HARADA
    Type: PAPER
    Article ID: 2020EBP3142
    Published: 2021
    [Advance publication] Released: March 31, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In this paper, the world's first experimental evaluation of the Wi-SUN Japan Utility Telemetering Association (JUTA) profile-compliant feathery receiver-initiated transmission (JUTA F-RIT) protocol is conducted. Firstly, the transmission success rate in an interference environment is evaluated by theoretical analysis and computer simulations. The analysis is derived from the interference model focusing on the carrier sense. The analysis and simulation results agree as regards the transmission success rate of the JUTA F-RIT protocol. Secondly, we develop the dongle-type prototype that hosts the JUTA F-RIT protocol. Measurement results in a cochannel interference environment show that the transmission success rate at the lower MAC layer is around 94% when the number of terminals is 20. When the waiting time for the establishment of the communication link can be extended to exceed 10 s, the JUTA F-RIT protocol can achieve the transmission success rate of over 90% without the re-establishment of the communication link and re-transmission of data frames. Moreover, the experimental results are examined from two viewpoints of the performance of the frame transmissions and the timeout incident, and the feature of the JUTA F-RIT protocol are discussed.

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  • Koji YAMAMOTO, Takayuki NISHIO, Masahiro MORIKURA, Hirantha ABEYSEKERA
    Type: PAPER
    Article ID: 2020EBT0009
    Published: 2021
    [Advance publication] Released: March 31, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In this paper, a stochasic geometry analysis of the inversely proportional setting (IPS) of carrier sense threshold (CST) and transmission power for densely deployed wireless local area networks (WLANs) is presented. In densely deployed WLANs, CST adjustment is a crucial technology to enhance spatial reuse, but it can starve surrounding transmitters due to an asymmetric carrier sensing relationship. In order for the carrier sensing relationship to be symmetric, the IPS of the CST and transmission power is a promising approach, i.e., each transmitter jointly adjusts its CST and transmission power in order for their product to be equal to those of others. This setting is used for spatial reuse in IEEE 802.11ax. By assuming that the set of potential transmitters follows a Poisson point process, the impact of the IPS on throughput is formulated based on stochastic geometry in two scenarios: an adjustment at a single transmitter and an identical adjustment at all transmitters. The asymptotic expression of the throughput in dense WLANs is derived and an explicit solution of the optimal CST is achieved as a function of the number of neighboring potential transmitters and signal-to-interference power ratio using approximations. This solution was confirmed through numerical results, where the explicit solution achieved throughput penalties of less than 8% relative to the numerically evaluated optimal solution.

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  • Hiroyuki SHINBO, Kosuke YAMAZAKI, Yoji KISHI
    Type: INVITED PAPER
    Article ID: 2020DSI0001
    Published: 2021
    [Advance publication] Released: March 30, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    To achieve highly efficient spectrum usage, dynamic sharing of scarce spectrum resources has recently become the subject of intense discussion. The technologies of dynamic spectrum sharing (DSS) have already been adopted or are scheduled to be adopted in a number of countries, and Japan is no exception. The authors and organizations collaborating in the research and development project being undertaken in Japan have studied a novel DSS system positioned between the fifth-generation mobile communication system (5G system) and different incumbent radio systems. Our DSS system has three characteristics. (1) It detects dynamically unused sharable spectrums (USSs) of incumbent radio systems for the space axis by using novel propagation models and estimation of the transmitting location with radio sensor information. (2) It manages USSs for the time axis by interference calculation with propagation parameters, fair assignment and future usage of USSs. (3) It utilizes USSs for the spectrum axis by using methods that decrease interference for lower separation distances. In this paper, we present an overview and the technologies of our DSS system and its applications in Japan.

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  • Arata TAKAHASHI, Osamu TAKYU, Hiroshi FUJIWARA, Takeo FUJII, Tomoaki O ...
    Type: PAPER
    Article ID: 2020DSP0005
    Published: 2021
    [Advance publication] Released: March 30, 2021
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    Information exchange through a relay node is attracting attention for applying machine-to-machine communications. If the node demodulates the received signal in relay processing confidentially, the information leakage through the relay station is a problem. In wireless MIMO switching, the frequency spectrum usage efficiency can be improved owing to the completion of information exchange within a short time. This study proposes a novel wireless MIMO switching method for secure information exchange. An overloaded situation, in which the access nodes are one larger than the number of antennas in the relay node, makes the demodulation of the relay node difficult. The access schedule of nodes is required for maintaining the overload situation and the high information exchange efficiency. This study derives the equation model of the access schedule and constructs an access schedule with fewer time periods in the integer programming problem. From the computer simulation, we confirm that the secure capacity of the proposed MIMO switching is larger than that of the original one, and the constructed access schedule is as large as the ideal and minimum time period for information exchange completion.

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  • Takashi SHIBA, Tomoyuki FURUICHI, Mizuki MOTOYOSHI, Suguru KAMEDA, Nor ...
    Type: PAPER
    Article ID: 2020DSP0006
    Published: 2021
    [Advance publication] Released: March 30, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    We propose a spectrum regeneration and demodulation method for multiple direct RF undersampled real signals by using a new algorithm. Many methods have been proposed to regenerate the RF spectrum by using undersampling because of its simple circuit architecture. However, it is difficult to regenerate the spectrum from a real signal that has a band wider than a half of the sampling frequency, because it is difficult to include complex conjugate relation of the folded spectrum into the linear algebraic equation in this case. We propose a new spectrum regeneration method from direct undersampled real signals that uses multiple clocks and an extended algorithm considering the complex conjugate relation. Simulations are used to verify the potential of this method. The validity of the proposed method is verified by using the simulation data and the measured data. We also apply this algorithm to the demodulation system.

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  • Kenichiro YAMAMOTO, Osamu TAKYU, Keiichiro SHIRAI, Yasushi FUWA
    Type: PAPER
    Article ID: 2020DSP0007
    Published: 2021
    [Advance publication] Released: March 30, 2021
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    Recently, broadband wireless communication has been significantly enhanced; thus, frequency spectrum scarcity has become an extremely serious problem. Spatial frequency reuse based on spectrum databases has attracted significant attention. The spectrum database collects wireless environment information, such as the radio signal strength indicator (RSSI), estimates the propagation coefficient for the propagation loss and shadow effect, and finds a vacant area where the secondary system uses the frequency spectrum without harmful interference to the primary system. Wireless sensor networks are required to collect the RSSI from a radio environmental monitor. However, a large number of RSSI values should be gathered because numerous sensors are spread over the wireless environment. In this study, a data compression technique based on spatial features, such as buildings and houses, is proposed. Using computer simulation and experimental evaluation, we confirm that the proposed compression method successfully reduces the size of the RSSI and restores the original RSSI in the recovery process.

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  • Atomu SAKAI, Keiichi MIZUTANI, Takeshi MATSUMURA, Hiroshi HARADA
    Type: PAPER
    Article ID: 2020DSP0008
    Published: 2021
    [Advance publication] Released: March 30, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    The Dynamic Spectrum Sharing (DSS) system, which uses the frequency band allocated to incumbent systems (i.e., primary users) has attracted attention to expand the available bandwidth of the fifth-generation mobile communication (5G) systems in the sub-6 GHz band. In Japan, a DSS system in the 2.3 GHz band, in which the ARIB STD-B57-based Field Pickup Unit (FPU) is assigned as an incumbent system, has been studied for the secondary use of 5G systems. In this case, the incumbent FPU is a mobile system, and thus, the DSS system needs to use not only a spectrum sharing database but also radio sensors to detect primary signals with high accuracy, protect the primary system from interference, and achieve more secure spectrum sharing. This paper proposes highly efficient sensing methods for detecting the ARIB STD-B57-based FPU signals in the 2.3 GHz band. The proposed methods can be applied to two types of the FPU signal; those that apply the Continuous Pilot (CP) mode pilot and the Scattered Pilot (SP) mode pilot. Moreover, we apply a sample addition method and a symbol addition method for improving the detection performance. Even in the 3GPP EVA channel environment, the proposed method can, with a probability of more than 99%, detect the FPU signal with an SNR of -10 dB. In addition, we propose a quantized reference signal for reducing the implementation complexity of the complex cross-correlation circuit. The proposed reference signal can reduce the number of quantization bits of the reference signal to 2 bits for in-phase and 3 bits for orthogonal components.

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  • Yoji UESUGI, Keita KATAGIRI, Koya SATO, Kei INAGE, Takeo FUJII
    Type: PAPER
    Article ID: 2020DSP0011
    Published: 2021
    [Advance publication] Released: March 30, 2021
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    This paper proposes a measurement-based spectrum database (MSD) with clustered fading distributions toward greater storage efficiencies. The conventional MSD can accurately model the actual characteristics of multipath fading by plotting the histogram of instantaneous measurement data for each space-separated mesh and utilizing it in communication designs. However, if the database contains all of a distribution for each location, the amount of data stored will be extremely large. Because the main purpose of the MSD is to improve spectral efficiency, it is necessary to reduce the amount of data stored while maintaining quality. The proposed method reduces the amount of stored data by estimating the distribution of the instantaneous received signal power at each point and integrating similar distributions through clustering. Numerical results show that clustering techniques can reduce the amount of data while maintaining the accuracy of the MSD. We then apply the proposed method to the outage probability prediction for the instantaneous received signal power. It is revealed that the prediction accuracy is maintained even when the amount of data is reduced.

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  • Ryo TAKAHASHI, Hidenori MATSUO, Fumiyuki ADACHI
    Type: PAPER
    Article ID: 2020FGP0010
    Published: 2021
    [Advance publication] Released: March 29, 2021
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    Ultra-densification of radio access network (RAN) is essential to efficiently handle the ever-increasing mobile data traffic. In this paper, a joint multi-layered user clustering and scheduling is proposed as an inter-cluster interference coordination scheme for ultra-dense RAN using cluster-wise distributed MIMO transmission/reception. The proposed joint multi-layered user clustering and scheduling consists of user clustering using the K-means algorithm, user-cluster layering (called multi-layering) based on the interference-offset-distance (IOD), cluster-antenna association on each layer, and layer-wise round-robin-type scheduling. The user capacity, the sum capacity, and the fairness are evaluated by computer simulations to show the effectiveness of the proposed joint multi-layered user clustering and scheduling. Also shown are uplink and downlink capacity comparisons and optimal IOD setting considering the trade-off between inter-cluster interference mitigation and transmission opportunity.

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  • Satoshi DENNO, Kazuma YAMAMOTO, Yafei HOU
    Type: PAPER
    Article ID: 2020EBP3183
    Published: 2021
    [Advance publication] Released: March 25, 2021
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    This paper proposes relay selection techniques for XOR physical layer network coding with MMSE based non-linear precoding in MIMO bi-directional wireless relaying networks. The proposed selection techniques are derived on the different assumption about characteristics of the MMSE based non-linear precoding in the wireless network. We show that the signal to noise power ratio (SNR) is dependent on the product of all the eigenvalues in the channels from the terminals to relays. This paper shows that the best selection techniques in all the proposed techniques is to select a group of the relays that maximizes the product. Therefore, the selection technique is called “product of all eigenvalues (PAE)” in this paper. The performance of the proposed relay selection techniques is evaluated in a MIMO bi-directional wireless relaying network where two terminals with 2 antennas exchange their information via relays. When the PAE is applied to select a group of the 2 relays out of the 10 relays where an antenna is placed, the PAE attains a gain of more than 13dB at the BER of 10-3.

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  • Naoto TSUMACHI, Masaya SHIBAYAMA, Ryuji KOBAYASHI, Issei KANNO, Yasuhi ...
    Type: PAPER
    Article ID: 2020FGP0001
    Published: 2021
    [Advance publication] Released: March 23, 2021
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    In March 2020, the 5th generation mobile communication system (5G) was launched in Japan. Frequency bands of 3.7 GHz, 4.5 GHz and 28 GHz were allocated for 5G services, and the 5G use cases fall into three broad categories: Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC) and Ultra-Reliable Low Latency Communication (URLLC). The use cases and services that take advantage of the characteristics of each category are expected to be put to practical use, and experiments of practical use are underway. This paper introduces and demonstrates a touchless gate that can identify, authenticate and allow passage through the gate by using these features and 5G beam tracking to estimate location by taking advantage of the low latency of 5G and the straightness of the 28 GHz band radio wave and its resistance to spreading. Since position estimation error due to reflected waves and other factors has been a problem, we implement an algorithm that tracks the beam and estimates the user's line of movement, and by using an infrared sensor, we made it possible to identify the gate through which the user passes with high probability. We confirmed that the 5G touchless gate is feasible for gate passage. In addition, we demonstrate that a new service based on high-speed high-capacity communication is possible at gate passage by taking advantage of the wide bandwidth of the 28 GHz band. Furthermore, as a use case study of the 5G touchless gate, we conducted a joint experiment with an airline company.

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  • Tatsuki OKUYAMA, Nobuhide NONAKA, Satoshi SUYAMA, Yukihiko OKUMURA, Ta ...
    Type: PAPER
    Article ID: 2020FGP0013
    Published: 2021
    [Advance publication] Released: March 23, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    The fifth-generation (5G) mobile communications system initially introduced massive multiple-input multiple-output (M-MIMO) with analog beamforming (BF) to compensate for the larger path-loss in millimeter-wave (mmW) bands. To solve a coverage issue and support high mobility of the mmW bands, base station (BS) cooperation technologies have been investigated in high-mobility environments. However, previous works assume one mobile station (MS) scenario and analog BF that does not suppress interference among MSs. In order to improve system performance in the mmW bands, fully digital BF that includes digital precoding should be employed to suppress the interference even when MSs travel in high mobility. This paper proposes two mmW BS cooperation technologies that are inter-baseband unit (inter-BBU) and intra-BBU cooperation for the fully digital BF. The inter-BBU cooperation exploits two M-MIMO antennas in two BBUs connected to one central unit by limited-bandwidth fronthaul, and the intra-BBU cooperates two M-MIMO antennas connected to one BBU with Doppler frequency shift compensation. This paper verifies effectiveness of the BS cooperation technologies by both computer simulations and outdoor experimental trials. First, it is shown that that the intra-BBU cooperation can achieve an excellent transmission performance in cases of two and four MSs moving at a velocity of 90 km/h by computer simulations. Second, the outdoor experimental trials clarifies that the inter-BBU cooperation maintains the maximum throughput in a wider area than non-BS cooperation when only one MS moves at a maximum velocity of 120 km/h.

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  • Toshiro NAKAHIRA, Tomoki MURAKAMI, Hirantha ABEYSEKERA, Koichi ISHIHAR ...
    Type: PAPER
    Article ID: 2020FGP0014
    Published: 2021
    [Advance publication] Released: March 23, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    In this paper, we examine techniques for improving the throughput of unlicensed radio systems such as wireless LANs (WLANs) to take advantage of multi-radio access to mobile broadband, which will be important in 5G evolution and beyond. In WLANs, throughput is reduced due to mixed standards and the degraded quality of certain frequency channels, and thus control techniques and an architecture that provide efficient control over WLANs are needed to solve the problem. We have proposed a technique to control the terminal connection dynamically by using the multi-radio of the AP. Furthermore, we have proposed a new control architecture called WiSMA for efficient control of WLANs. Experiments show that the proposed method can solve those problems and improve the WLAN throughput.

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  • Yutaro KOBAYASHI, Yukitoshi SANADA
    Type: PAPER
    Article ID: 2020FGT0001
    Published: 2021
    [Advance publication] Released: March 23, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In a multiple-input multiple-output (MIMO) system, maximum likelihood detection (MLD) is the best demodulation scheme if no a priori 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.

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  • Sakae NAGAOKA, Mark BROWN, Daniel DELAHAYE
    Type: PAPER
    Article ID: 2020EBP3019
    Published: 2021
    [Advance publication] Released: March 22, 2021
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    Air traffic management (ATM) systems around the world are being modernized to accommodate shifts towards performance- and trajectory-based operations. These shifts will require new indices for safety, efficiency and complexity. The authors have been developing an index for evaluating air traffic control (ATC) difficulty that utilizes the relative positions and velocity vectors of aircraft pairs as input data. Prior to practical application of the index, it is necessary to understand the effects of input data error, i.e. errors in the positions and velocities of a pair of aircraft, on the estimated difficulty value. Two sensitivity analyses were therefore performed for a pair of aircraft cruising at constant speeds on intersecting linear tracks at the same altitude. Sensitivity analysis examines how uncertainty in inputs relates to uncertainty in outputs. Firstly, an analysis of propagation error was carried out. The formula of the propagation error at a certain point was derived based on the assumed input error, and the distribution of propagation error was investigated for all possible situations and compared with the distribution of difficulty values to clarify its characteristics. Secondly, a sensitivity analysis based on variance was carried out that evaluated the effect of each input parameter using a conditional variance value called the Sobol indices. Using a Monte Carlo method, we investigated the effect of each input parameter on the calculated difficulty value for all possible situations of aircraft pairs on intersecting trajectories. As a result, it was found that the parameter that most affects the difficulty value is the intersection angle of the trajectories.

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  • Jian-Yu PAN, Kuei-Chiang LAI, Yi-Ting LI, Szu-Lin SU
    Type: PAPER
    Article ID: 2020EBP3111
    Published: 2021
    [Advance publication] Released: March 22, 2021
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    Iterative block decision feedback equalization with hard-decision feedback (HD-IBDFE) was proposed for single-carrier transmission with frequency-domain equalization (SC-FDE). The detection performance hinges upon not only error propagation, but also the accuracy of estimating the parameters used to re-compute the equalizer coefficients at each iteration. In this paper, we use the erasure zone (EZ) to de-emphasize the feedback values when the hard decisions are not reliable. EZ use also enables a more accurate, and yet computationally more efficient, parameter estimation method than HD-IBDFE. We show that the resulting equalizer coefficients share the same mathematical form as that of the HD-IBDFE, thereby preserving the merit of not requiring matrix inverse operations in calculating the equalizer coefficients. Simulations show that, by using the EZ and the proposed parameter estimation method, a significant performance improvement over the conventional HD-IBDFE can be achieved, but with lower complexity.

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  • Kuei-Chiang LAI, Chi-Jen CHEN
    Type: PAPER
    Article ID: 2020EBP3165
    Published: 2021
    [Advance publication] Released: March 22, 2021
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    In this paper, we address the problem of detector design in severely frequency-selective channels for spatial multiplexing systems that adopt filter bank multicarrier based on offset quadrature amplitude modulation (FBMC/OQAM) as the communication waveforms. We consider decision feedback equalizers (DFEs) that use multiple feedback filters to jointly cancel the post-cursor components of inter-symbol interference, inter-antenna interference, and, in some configuration, inter-subchannel interference. By exploiting the special structures of the correlation matrix and the staggered property of the FBMC/OQAM signals, we obtain an efficient method of computing the DFE coefficients that requires a smaller number of multiplications than the linear equalizer (LE) and conventional DFE do. The simulation results show that the proposed detectors considerably outperform the LE and conventional DFE at moderate-to-high signal-to-noise ratios.

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  • Risa FUJITA, Fujun HE, Eiji OKI
    Type: PAPER
    Article ID: 2020EBP3176
    Published: 2021
    [Advance publication] Released: March 22, 2021
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    This paper presents an analytical model that yields the unavailability of a network function when each backup server can protect two functions and can recover one of them. Previous work describes a model to deal with the case that each function can be protected only by one server. In our model, we allow each function to be protected by multiple servers to ensure function availability. This requires us to know the feasible states of a connected component and its state transitions. By adopting the divide-and-conquer method, we enumerate the feasible states of a connected component. We then classify its state transitions. Based on the obtained feasible states and the classification of the state transitions, we enumerate the feasible states incoming to and outgoing from a general state, the transfer rates, and the conditions. With those informations, we generate multiple equations about the state transitions. Finally, by solving them, we obtain the probabilities that a connected component is in each state and calculate the unavailability of a function. Numerical results show that the average unavailability of a function is reduced by 18% and 5.7% in our two examined cases by allowing each function to be protected by multiple servers.

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  • Daisuke INOUE, Kyogo OTA, Mamoru SAWAHASHI, Satoshi NAGATA
    Type: PAPER
    Article ID: 2020FGP0003
    Published: 2021
    [Advance publication] Released: March 17, 2021
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    This paper presents the physical-layer cell identity (PCID) detection probability using the narrowband primary synchronization signal (NPSS) and narrowband secondary synchronization signal (NSSS) based on the narrowband Internet-of-Things (NB-IoT) radio interface considering frequency offset and the maximum Doppler frequency in the 28-GHz band. Simulation results show that the autocorrelation based NPSS detection method is more effective than the cross-correlation based NPSS detection using frequency offset estimation and compensation before the NPSS received timing detection from the viewpoints of PCID detection probability and computational complexity. We also show that when using autocorrelation based NPSS detection, the loss in the PCID detection probability at the carrier frequency of fc = 28 GHz compared to that for fc = 3.5 GHz is only approximately 5% at the average received SNR of 0 dB when the frequency stability of a local oscillator of a user equipment (UE) set is 20 ppm. Therefore, we conclude that the multiplexing schemes and sequences of NPSS and NSSS based on the NB-IoT radio interface associated with autocorrelation based NPSS detection will support the 28-GHz frequency spectra.

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  • Tsubasa SHOBUDANI, Mamoru SAWAHASHI, Yoshihisa KISHIYAMA
    Type: PAPER
    Article ID: 2020FGP0004
    Published: 2021
    [Advance publication] Released: March 17, 2021
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    This paper proposes time division multiplexing (TDM) based reference signal (RS) multiplexing for faster-than-Nyquist (FTN) signaling using orthogonal frequency division multiplexing (OFDM).We also propose a subframe structure in which a cyclic prefix (CP) is appended to only the TDM based RS block and the first FTN symbol to achieve accurate estimation of the channel response in a multipath fading channel with low CP overhead. Computer simulation results show that the loss in the required average received SNR satisfying the average block error rate (BLER) of 10-2 using the proposed TDM based RS multiplexing from that with ideal channel estimation is suppressed to within approximately 1.2 dB and 1.7 dB for QPSK and 16QAM, respectively. This is compared to when the improvement ratio of the spectral efficiency from CP-OFDM is 1.31 with the rate-1/2 turbo code. We conclude that the TDM based RS multiplexing with the associated CP multiplexing is effective in achieving accurate channel estimation for FTN signaling using OFDM.

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  • Kana AONO, Bin ZHENG, Mamoru SAWAHASHI, Norifumi KAMIYA
    Type: PAPER
    Article ID: 2020FGP0005
    Published: 2021
    [Advance publication] Released: March 17, 2021
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    This paper presents the bit error rate (BER) performance of frequency domain equalization (FDE) using cyclic-shifted code division multiplexing (CDM) pilot signals for single-carrier line-of-sight (LOS) -multiple-input multiple-output (MIMO) multiplexing. We propose applying different cyclic-shift resources of the same Zadoff-Chu sequence to transmission-stream-specific pilot signals that are essential for estimating the channel response for FDE and phase noise in LOS-MIMO. To validate the effectiveness of the cyclic-shifted pilot multiplexing, we use partial low-density parity-check (LDPC) coding with double Gray mapping and collaborative decoding. Simulations show that pilot signal multiplexing using a cyclic-shifted Zadoff-Chu sequence, and frequency domain averaging of the estimated channel response are effective in achieving accurate channel estimation for single-carrier LOS-MIMO. We also show that the required received signal-to-noise power ratio at the BER of 10-7 using partial LDPC coding is decreased by more than 6.6 dB compared to that without LDPC coding even for the deep notch depth of -20 dB regardless of the relationship between the notch frequencies in the direct and cross links for 2 × 2 LOS-MIMO in a Rummler fading channel. Therefore, we conclude that the CDM-based pilot signal multiplexing with different cyclic shifts is effective in accurately estimating the channel response specific to the combination sets of transmitter and receiver antennas and in achieving a low pilot-overhead loss for single-carrier LOS-MIMO.

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  • Daisuke INOUE, Kyogo OTA, Mamoru SAWAHASHI, Satoshi NAGATA
    Type: PAPER
    Article ID: 2020FGP0006
    Published: 2021
    [Advance publication] Released: March 17, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    This paper proposes a physical-layer cell identity (PCID) detection method that uses joint estimation of the frequency offset and secondary synchronization signal (SSS) sequence for the 5G new radio (NR) initial access with beamforming transmission at a base station. Computer simulation results show that using the PCID detection method with the proposed joint estimation yields an almost identical PCID detection probability as the primary synchronization signal (PSS) detection probability at an average received signal-to-noise ratio (SNR) of higher than approximately -5 dB suggesting that the residual frequency offset is compensated to a sufficiently low level for the SSS sequence estimation. It is also shown that the PCID detection method achieves a high PCID detection probability of greater than 90% and 50% at the carrier frequency of 30 and 50 GHz, respectively, at the average received SNR of 0 dB for the frequency stability of a user equipment oscillator of 3 ppm.

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  • Manabu MIKAMI, Koichi SERIZAWA, Kohei MOTO, Hitoshi YOSHINO
    Type: PAPER
    Article ID: 2020FGP0007
    Published: 2021
    [Advance publication] Released: March 17, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    Fifth generation mobile communication system (5G) mobile operators need to explore new use cases and/or applications together with vertical industries, the industries which are potential users of 5G, in order to fully exploit the new 5G capabilities in terms of its application. Vehicular communications for platooning are considered to be one of new use cases of 5G whose low-latency and ultra-reliability are required. This paper presents our field evaluations on latency and reliability performance of 5G V2V Direct communication towards application to truck platooning. The authors build a field experimental environment, for V2X communications of truck platooning, with actual large-size trucks and a prototype system employing 5G New Radio (NR) technologies, and performed some field experiments in rural areas. In this paper, we introduce the 5G NR-V2X prototype system. Its most distinctive feature is that the prototype system is equipped with V2V Direct communication radio interface (i.e., sidelink), in addition to the traditional radio interfaces between BS and UE (i.e., downlink and uplink). Then, we present the field evaluation results of radio propagation environment results and over-the-air transmission performance of latency and reliability characteristics on the V2V Direct communication of the prototype in real public express highway environment including tunnel area as well as tunnel outside area, in order to assess 5G NR-V2X system applying to truck platooning. The radio propagation and the latency performance evaluation results clarify that the latency performance is degraded due to Hybrid Automatic Repeat reQuest (HARQ) retransmission at the outside of tunnel more possibly than the inside of tunnel, since larger path loss values can be observed at the outside of tunnel than the inside of tunnel, in V2V Direct communications of truck platooning. The over-the-air latency and reliability evaluation results confirm that it is important to set an appropriate maximum number of HARQ retransmissions since there is a trade-off problem in order to realize low latency and high reliability simultaneously.

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  • Chihiro MORI, Miyu NAKABAYASHI, Mamoru SAWAHASHI, Teruo KAWAMURA, Nobu ...
    Type: PAPER
    Article ID: 2020FGP0008
    Published: 2021
    [Advance publication] Released: March 17, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    This paper presents the average block error rate (BLER) performance of circular 32QAM and 64QAM schemes employing a frequency domain equalizer (FDE) for discrete Fourier transform (DFT)-precoded orthogonal frequency division multiplexing (OFDM) in multipath Rayleigh fading channels. The circular QAM scheme has an advantageous feature in that the fluctuation in the amplitude component is smaller than that for the cross or rectangular QAM scheme. Hence, focusing on the actual received signal-to-noise power ratio (SNR) taking into account a realistic peak-to-average power ratio (PAPR) measure called the cubic metric (CM), we compare the average BLER of the circular 32QAM and 64QAM schemes with those of cross 32QAM and rectangular 64QAM schemes, respectively. We investigate the theoretical throughput of various circular 32QAM and 64QAM schemes based on mutual information from the viewpoint of the minimum Euclidean distance. Link-level simulation results show that the circular 32QAM and 64QAM schemes with independent bit mapping for the phase and amplitude modulations achieves a lower required average received SNR considering the CM than that with the minimum Euclidean distance but with composite mapping of the phase and amplitude modulations. Through extensive link-level simulations, we show the potential benefit of the circular 32QAM and 64QAM schemes in terms of reducing the required average received SNR considering the CM that satisfies the target average BLER compared to the cross 32QAM or rectangular 64QAM scheme.

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  • Manabu MIKAMI, Kohei MOTO, Koichi SERIZAWA, Hitoshi YOSHINO
    Type: PAPER
    Article ID: 2020FGP0009
    Published: 2021
    [Advance publication] Released: March 17, 2021
    JOURNALS RESTRICTED ACCESS ADVANCE PUBLICATION

    Fifth generation mobile communication system (5G) mobile operators need to explore new use cases and/or applications together with vertical industries, the industries that are potential users of 5G, in order to fully exploit the new 5G capabilities in terms of its application. Vehicle-to-Everything (V2X) communications for platooning are considered to be one of new 5G use cases requiring low-latency and ultra-reliability are required. This paper presents our field trial of dynamic mode switching for 5G New Radio (NR) based V2X sidelink communications towards application to truck platooning. The authors build a field trial environment, for V2X communications of truck platooning, with actual large-size trucks and a prototype system employing 5G NR technologies, and performed some field trials in rural areas. In this paper, we introduce the 5G NR-V2X prototype system. Its most distinctive characteristic is that the prototype system is equipped with vehicle-to-vehicle (V2V) Direct communication radio interface (i.e., sidelink), in addition to the traditional radio interfaces between base station (BS) and user equipment (UE), i.e., downlink and uplink. Moreover, it is also most distinctive that the sidelink (SL) interface supports a new function of dynamic mode switching between two modes of BS In-Coverage mode (SL Mode-1) and BS Out-of-Coverage mode (SL Mode-2) in order to achieve seamless V2V communications between BS in-coverage area and BS out-of-coverage area. Then, we present the evaluation results on over-the-air latency performance on the V2V Direct communication of the prototype using SL dynamic mode switching with two experimental base station antenna sites in a public express highway environment towards application to truck platooning. The results demonstrate that our developed the SL dynamic mode switching achieves the seamless V2V Direct communications between in-coverage area and out-of-coverage area.

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  • Erik Dahlman, Gunnar Mildh, Stefan Parkvall, Patrik Persson, Gustav Wi ...
    Type: INVITED PAPER
    Article ID: 2020FGI0001
    Published: 2021
    [Advance publication] Released: March 08, 2021
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    The paper provides an overview of the current status of the 5G evolution as well as a research outlook on the future wireless-access evolution towards 6G

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