IEICE Communications Express
Online ISSN : 2187-0136
ISSN-L : 2187-0136
Volume 10 , Issue 8
Showing 1-34 articles out of 34 articles from the selected issue
Special Cluster on Advanced Communication Technologies in Conjunction with Main Topics of ICETC2020
  • Masaharu Takahashi
    Type: FOREWORD
    2021 Volume 10 Issue 8 Pages 421
    Published: August 01, 2021
    Released: August 01, 2021
    JOURNAL FREE ACCESS
    Download PDF (120K)
  • Ryota Kawase, Taichi Okumura, Masaki Murakami, Yoshihiko Uematsu, Taka ...
    Type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2021 Volume 10 Issue 8 Pages 422-427
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 09, 2021
    JOURNAL FREE ACCESS

    This study reports that the expected capacity guaranteed routing (ECGR) testbed was built and the face recognition service was provided in the testbed. ECGR, which guarantees that the expected capacity calculated based on link failure probability exceeds the requested capacity of flows, has been proposed. On the ECGR testbed, we verify that the assigned expected capacity meets the required capacity. Fault tolerance experiments were conducted to evaluate the impact of not only single link failure but also multiple link failures on the service. From these evaluations, we verified that it is possible to provide highly reliable services on the ECGR.

    Download PDF (860K)
  • Kakeru Matsubara, Yuta Goto, Koki Ito, Kazushi Shimada, Kazuki Maruta, ...
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 428-434
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 09, 2021
    JOURNAL FREE ACCESS

    This letter adopts higher-order modulation scheme than 16QAM to our previously proposed semi-blind uplink interference suppression scheme for multicell multiuser massive MIMO systems. Our semi-blind approach is attained by the decision feedback channel estimation (DFCE) and the sample matrix inversion (SMI) spatial adaptive filtering. However, its efficiency depended on inter-cell interference (ICI), in particular for higher-order QAM. We propose to employ cell partitioning-based M-ary QAM to avoid ICI at the initial condition and verify overall spectral efficiency improvement.

    Download PDF (371K)
  • Kai Isaka, Teruyuki Miyajima, Yoshiki Sugitani
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 435-440
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 09, 2021
    JOURNAL FREE ACCESS

    This paper proposes a neural network-based time-domain equalizer (TEQ) in OFDM systems. The proposed TEQ based on the minimum output energy criterion does not require the transmission of a training signal or the insertion of a cyclic prefix to suppress inter-symbol interference; thus, the proposed TEQ does not degrade bandwidth efficiency. Further, an arbitrary decision delay and multiple receive antennas are introduced to improve the bit error rate performance. By simulation, we show that the proposed TEQ is significantly superior to a conventional scheme.

    Download PDF (244K)
  • Tomoki Tokunaga, Kimihiro Mizutani
    Type: LETTER
    Subject area: Network Management/Operation
    2021 Volume 10 Issue 8 Pages 441-446
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 09, 2021
    JOURNAL FREE ACCESS

    In recent years, a scheme for generating a large amount of mobile traffic data has been proposed. In the state-of-the-art of the schemes, Generative Adversarial Networks (GANs) is used to transform a large amount of traffic data into a coarse-grained representation and to generate the original traffic data from the coarse-grained data. However, in order to generate the original traffic data, the coarse-grained data must be preserved and it takes waste storage cost. In this paper, we propose a scheme for generating the mobile traffic data without requiring a coarse-grained process by using Conditional SR-GAN. In evaluation using real mobile traffic data, our proposed scheme not only does reduce the storage cost by more than 25% compared to the traditional scheme, but also can generate the original mobile traffic data with 94% accuracy.

    Download PDF (2945K)
  • Ryohei Banno, Yusuke Kitagawa, Kazuyuki Shudo
    Type: LETTER
    Subject area: Network System
    2021 Volume 10 Issue 8 Pages 447-450
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 09, 2021
    JOURNAL FREE ACCESS

    Blockchain systems are built on top of overlay networks. While typical blockchains are based on unstructured overlays, some other blockchains utilizes structured overlays to improve the inefficiency of information propagation in unstructured overlays. However, using structured overlays have security risks such as Eclipse Attack. In this paper, we propose a method for blockchain systems to exploit a semi-structured overlay with Flexible Routing Tables (FRT), so that we can obtain both communication efficiency and safety.

    Download PDF (200K)
  • Koki Ito, Kakeru Matsubara, Kazushi Shimada, Yuta Goto, Kazuki Maruta, ...
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 451-457
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 16, 2021
    JOURNAL FREE ACCESS

    This paper expands an analytical formulation of maximal ratio transmission (MRT) precoded massive multiple-input multiple-output (MIMO) systems. Evaluating performance on massive MIMO systems where both base station (BS) and user terminals (UTs) have array antennas could impose impractical computation complexity. The existing work derived the power distribution of inter-user interference (IUI) but that of the desired signal was treated as fixed. This paper enhances its modeling accuracy by deriving the latest. The consistency of the proposed model is confirmed by comparing it to the simulation results.

    Download PDF (142K)
  • Toru Nishiyama, Takuyuki Hirakawa, Syo Nakaie, Shigeru Tomisato, Satos ...
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 458-462
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: February 22, 2021
    JOURNAL FREE ACCESS

    In this paper, in order to establish the storage batch signal processing technology on the network, the method of separating the IoT/M2M terminal signal that collided or interfered and the method of demodulating the data after signal separation, which cannot be realized by the conventional receivers. We proposed a method of signal separation by feature quantity extraction using short-time Fourier transform and the method of using the obtained feature quantity for demodulation. In addition, the effectiveness of the proposed method for multi-valued modulated signals will be evaluated by computer simulation.

    Download PDF (253K)
  • Masaya Suzuki, Kimihiro Mizutani
    Type: LETTER
    Subject area: Network System
    2021 Volume 10 Issue 8 Pages 463-468
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    Distributed large scale neural networks are widely used in complicated image recognition and natural language processing among several organizations, but it takes much maintenance cost for keeping the nodes (i.e, computation servers) performance and their network topology in a churn environment that nodes insertion/deletion occurs frequency. To reduce the cost in the environment, we proposed Distributed Skip Mesh List Architecture, which can provide high stability against node insertion/deletion and automatic node management to a distributed large scale neural network management. In the evaluation, we confirmed that it reduces the maintenance cost (e.g., transmission messages for managing nodes) with high stability.

    Download PDF (206K)
  • Hina Watanabe, Masaharu Takahashi
    Type: LETTER
    Subject area: Antennas and Propagation
    2021 Volume 10 Issue 8 Pages 469-473
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    With the growing aging society, extending healthy life expectancy has been attracting attention. Small devices using IoT and wireless technologies are expected to have effect on self-health management. However, batteries and power cables cause problems such as the restriction on human motion or the devices’ size. Therefore, wireless power transmission (WPT) addresses these problems and use of WPT may help with improving daily health care management. In this paper, we propose a WPT system between mobile devices and a sensor on the fingertip by using Near Field Communication (NFC). The proposed system can transfer enough power for IoT sensors.

    Download PDF (3320K)
  • Naoya Tanuma, Yuta Goto, Kazuki Maruta, Chang-Jun Ahn
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 474-479
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    Decoder of polar coded bits requires the successive cancellation (SC). Its capability is known to be limited when the code length is shorter. Encoding block size for the polar coding is predetermined and the block is divided into two types: frozen bits that contain fixed zeros and information bits that contain data. This letter proposes a new decoding scheme that artificially extends the block length by concatenating the copied codeword at the receiver side, focusing on the polar codes’ generator matrix characteristics. Since it simply doubles the computation load, we additionally apply a convolutional neural network (CNN) to determine its applicability by observing the received signal power spectrum. Computer simulations verifies its effectiveness; improved bit error rate and reduced computation complexity.

    Download PDF (114K)
  • Go Yazawa, Takahiro Kubo, Natsuki Yasuhara, Shinichi Yoshihara
    Type: LETTER
    Subject area: Network System
    2021 Volume 10 Issue 8 Pages 480-485
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    For transmitting video or financial transaction information, communication interruption must be short, so hitless redundancy switching (HRS) technology is a useful solution. However, when this technology is used in multiple sites, a large amount of resources is required for HRS devices to communicate. In this paper, we propose an efficient resource allocation method and demonstrate that it can reduce resource usage by 97% in a numerical simulation.

    Download PDF (273K)
  • Naoya Tanuma, Yuta Goto, Kazuki Maruta, Chang-Jun Ahn
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 486-491
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    This article proposes a known bits puncturing scheme for systematic polar code. The puncturing deteriorates BER performance because the removed bits are generally unknown at the receiving side. Polar code supports systematic encoding which generate the codeword that has the same value of information bits. Exploiting this characteristic, known bits, which are pre-shared between the transmitter and the receiver, are punctured from the codeword. The receiving side then set punctured bits to the known values and it can assist the decoding capability. Computer simulation verifies its effectiveness in terms of BER as well as throughput performance.

    Download PDF (198K)
  • Yutao Liu, Toru Nishiyama, Shigeru Tomisato, Kazuhiro Uehara
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 492-497
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    Automatic Modulation Classification (AMC) of the transmitted signals remains a challenging area in modern intelligent communication systems such as cognitive radio system. In this research, we propose a new system for AMC using Convolutional Neural Network (CNN) with constellation diagrams in Additive White Gaussian Noise channel and use the trained model to recognite five digital modulation methods: BPSK, QPSK, 8PSK, 16QAM and 64QAM with constellation diagrams. We have achieved high efficiency and high precision recognition of modulation methods by using new CNN models, improved input image size, number of dropout layers and simulation hyperparameters.

    Download PDF (382K)
  • Takuya Yamamoto, Takaya Yamazato, Hiraku Okada, Masayuki Kinoshita, Ko ...
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 498-504
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    This study describes intelligent transport image sensor communication (ITS-ISC) systems that use LED arrays as transmitters that imitate traffic lights. Three signal-transmission schemes -luminance modulation, spatial modulation, and combined luminance and spatial modulation- use LED array. However, their suitability for ITS-ISC has not been explored yet. Therefore, we compare the communication performance of these three systems under strong saturation and present the results.

    Download PDF (795K)
  • Karin Umeda, Takashi Nishitsuji, Takuya Asaka, Takumi Miyoshi
    Type: LETTER
    Subject area: Network System
    2021 Volume 10 Issue 8 Pages 505-510
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    In wireless sensor networks, distributed processing technology for deep learning that utilizes edge computing and mobile terminals has been attracting interest; however, with the expansion of the use of wireless sensor networks, the amount of data and the increase in server load are issues, especially for deep learning. Although the existing studies which improve the data processing speed and latency reduction of distributed processing, there is still a problem in which the amount of communication and the load on the server increase. In this paper, we propose load balancing algorithm for deep learning to reduce the communication volume and server load.

    Download PDF (143K)
  • Rei Hasegawa, Yuzo Moriuchi, Noriyuki Shimizu, Takeshi Yasunaga, Hidek ...
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 511-515
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    Local 5G is expected as a system to provide a communication service within a certain specific area and it is also supposed to apply the spectrum sharing which is attractive techniques to utilize the frequency resources. In order to utilize those shared spectrum, it is required to improve the interference control among systems which use the shared spectrum. In this paper, we examine and report the application of the control method with the arrangement of multiple base station when compensating for the coverage of the part where the received power locally decreases.

    Download PDF (379K)
  • Enzo Tsukui, Kentaro Toba, Takaha Fujita, K.I. Amila Sampath, Joji Mae ...
    Type: LETTER
    Subject area: Optical Fiber for Communications
    2021 Volume 10 Issue 8 Pages 516-521
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    We numerically study transmission limitations of an unrepeated optical link using Kramers-Kronig (KK) relation-based direct detection. The transmission distance is limited by the thermal noise of the optical front-end and the signal distortions caused by fiber nonlinearity in optical amplifier-free transmission and by amplified spontaneous emission (ASE) noise and fiber nonlinearities when pre-amplification is enabled at the receiver. The transmission limits of QPSK, 16-QAM, and 64-QAM modulation formats in optical amplifier-free 25-GBaud transmission can be extended from 109, 80, and 52 km to 186, 134, and 90 km by enabling pre-amplification at the receiver, respectively.

    Download PDF (347K)
  • Kimitoshi Murano, Yoshio Kami, Youji Kotsuka
    Type: LETTER
    Subject area: Electromagnetic Compatibility (EMC)
    2021 Volume 10 Issue 8 Pages 522-527
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    This study proposes a new method of suppressing a noise component propagating along a differential transmission line by using a near-field noise-suppression device (NSD). An NSD proposed here is composed of certain passive electronic components and features a resonance structure. In this study, a method of analyzing the transmission characteristics of a differential transmission line loaded with an NSD is presented, and several examples of the use of the method are presented. Moreover, the measured mixed-mode S-parameters of the differential transmission line loaded with an NSD are presented as examples of the transmission characteristics, and its validity is experimentally verified.

    Download PDF (798K)
  • Keita Onose, Hiroto Kuriki, Ryota Kimura, Ryo Sawai
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 528-532
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    In this letter, we propose an advanced incumbent protection method that considers three-dimensional aspects of 5G New Radio (NR) beamforming for dynamic spectrum access (DSA). The proposed method further introduces a concept of area-based protection to satisfy protection criteria for a primary system (PS) with inaccurate location information. We show some computer simulation results for deploying a 5G based secondary system (SS) in a millimeter-wave band which is primarily assigned to a fixed wireless access (FWA) based PS. The results demonstrate that the proposed method increases allowable transmission powers of the SS by up to 15 dB, compared to a conventional method.

    Download PDF (333K)
  • Shotaro Ishikura, Miki Yamamoto
    Type: LETTER
    Subject area: Internet
    2021 Volume 10 Issue 8 Pages 533-537
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    Copa [1] is a practical delay-based end-to-end congestion control. It can attain a unique Nash equilibrium with other flows with achieving high throughput and low queueing delay. In this paper, we propose adaptive time window [2] which can resolve Copa’s technical problem of initial phase overshoot of the congestion window size caused by slightly long time period for measuring the smallest roundtrip time. Our evaluation results show that our proposed adaptive window improves convergence of congestion window in the initial phase [2] and also shows good performance even in the situation that network jitter fluctuates measured RTT.

    Download PDF (775K)
  • Eri Hosonuma, Taku Yamazaki, Takumi Miyoshi, Ryo Yamamoto, Thomas Silv ...
    Type: LETTER
    Subject area: Network
    2021 Volume 10 Issue 8 Pages 538-543
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    In ad hoc networks, backoff-based opportunistic routing enables flexible forwarder selection based on a random backoff time. However, it assumes to require symmetry of each link due to the use of reverse path information. In this letter, we verify an asymmetric link problem based on their behavior and propose a solution to this problem. The proposed method confirms and ensures the destination reachability of each terminal based on link symmetry using a flag and restricts the acknowledgment procedure to avoid the problem. Finally, we examine the impact of asymmetric link use and the effectiveness of the proposed method by simulations.

    Download PDF (688K)
  • Hiroto Kuriki, Keita Onose, Ryota Kimura, Ryo Sawai
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 544-551
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: March 29, 2021
    JOURNAL FREE ACCESS

    In this letter, we propose and evaluate a new area-based primary protection method for dynamic spectrum access, in which a secondary system uses a frequency band assigned to a primary system while it keeps an aggregate interference below an acceptable level of the primary system. We consider that a location information of a primary system’s reception station (PRS) whose antenna boresight faces towards a moving primary transmission station is ambiguous. To accurately calculate the aggregate interferences from the secondary system to the PRS in such a situation, the proposed method predicts a range of the PRS’s antenna rotation. Our simulation results show that the proposed method can increase availability of the secondary system significantly in a practical urban scenario.

    Download PDF (2021K)
  • Yuki Sato, Takeru Kyono, Kai Ikuta, Yuichiro Kurokawa, Moriya Nakamura
    Type: LETTER
    Subject area: Fiber-Optic Transmission for Communications
    2021 Volume 10 Issue 8 Pages 552-557
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: April 09, 2021
    JOURNAL FREE ACCESS

    We proposed a novel nonlinear equalization scheme using a support vector machine (SVM) for optical fiber communication systems. The scheme works even when the received symbols are completely distorted on a constellation map. Whereas conventional SVM-based nonlinear equalization is performed on a two-dimensional (2D) in-phase-quadrature (IQ)-plane, our proposed scheme uses the SVM in a higher dimensional signal space after tapped delay lines. By employing the proposed scheme, we can enlarge the separation between the distorted symbols. We investigated the basic performance using simulated optical fiber transmission of 10-GSymbol/s 16QAM signals. The receiver sensitivity was improved by 2 dB at a BER of 10-5.

    Download PDF (319K)
  • Yuki Miyashita, Takeru Kyono, Kai Ikuta, Yuichiro Kurokawa, Moriya Nak ...
    Type: LETTER
    Subject area: Fiber-Optic Transmission for Communications
    2021 Volume 10 Issue 8 Pages 558-563
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: April 09, 2021
    JOURNAL FREE ACCESS

    We investigated the performance of artificial neural network (ANN)-based nonlinear equalizers for optical nonlinearity compensation by comparing activation functions, including a sigmoid function, ReLU, and Leaky ReLU. We compared the learning speeds and compensation performances by evaluating the resulting error vector magnitudes of the compensated signals. The performance was investigated using simulated 100-km optical fiber transmission of 10-GSymbol/s 16QAM signals. When the number of hidden-layer units in the ANN was small, the sigmoid function showed better performance in learning speed than ReLU and Leaky ReLU. This point is important because the number of ANN units has to be reduced in order to improve the computational complexity of the ANN-based nonlinear equalizer.

    Download PDF (287K)
Regular Section
  • Liuyi Yang, Tomio Kamada, Chikara Ohta
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 564-569
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: May 14, 2021
    JOURNAL FREE ACCESS

    As the demand for indoor localization applications continues to grow, device-free localization based on Wi-Fi Channel State Information (CSI) has become a popular research topic. Wi-Fi signals are, however, easily affected by environmental factors such as furniture changes. These factors disable the original localization system, and rebuilding it will cost a lot of time and workforce. This is a major challenge of device-free Wi-Fi localization. To address this issue, we use a transfer learning method, “Integration of Global and Local Metrics for Domain Adaptation (IGLDA),” and improve it, aiming to adapt the original localization model to the changing environment. Consequently, the localization accuracy is improved from 26.3 % to 82.2 % by only recollecting 37.5 % of data.

    Download PDF (460K)
  • Amila Kariyawasam, Masaki Shiraiwa, Yoshinari Awaji, Katsumi Takano, J ...
    Type: LETTER
    Subject area: Fiber-Optic Transmission for Communications
    2021 Volume 10 Issue 8 Pages 570-575
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: May 20, 2021
    JOURNAL FREE ACCESS

    We experimentally studied field trajectory shaping of optical binary phase shift keying-vestigial sideband (BPSK-VSB) signal for optical quadrature phase-shift keying (QPSK)-VSB generation. The field trajectory of the BPSK-VSB signal is an ellipse. In phase-shift method-based optical BPSK-VSB modulation, the ellipticity of the field trajectory can be controlled by manipulating the amplitude response of the Hilbert transformer. When the Hilbert transformer has a high-pass amplitude response, the field trajectory of the optical BPSK-VSB signal reaches a circle with increasing cut-off frequency. We numerically calculated and experimentally demonstrated the achievability of circular field trajectories in BPSK-VSB modulation for cut-off frequencies greater than 20% of the baseband bandwidth.

    Download PDF (1186K)
  • Ryota Ishioka, Junji Higashiyama, Yasunori Suzuki, Keisuke Nagase
    Type: LETTER
    Subject area: Electromagnetic Compatibility (EMC)
    2021 Volume 10 Issue 8 Pages 576-581
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: May 25, 2021
    JOURNAL FREE ACCESS

    Reducing the transmit power of mobile phones is effective in preventing electromagnetic interference (EMI) with medical devices in hospitals. However, to our best knowledge, no study has shown transmit power measurement results of mobile phones for which the configured-maximum-transmit-power was controlled by specific base station (BS) parameters. This letter shows transmit power measurement results from a mobile phone for which the configured-maximum-transmit-power is experimentally controlled by indoor BSs in a hospital. Reduction in the mobile phone transmit power and the issue of preventing EMI with medical devices are discussed based on the measurement results.

    Download PDF (1059K)
  • Shuichi Ohno, Keitaro Terada, Tetsuya Yokotani, Koichi Ishibashi
    Type: LETTER
    Subject area: Network
    2021 Volume 10 Issue 8 Pages 582-586
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: May 27, 2021
    JOURNAL FREE ACCESS

    Some IoT services require simplified mechanisms in networks in order to communicate reliably and with low latency. This paper proposes a mechanism for connecting MQTT brokers for this purpose. In this proposal, the ring topology for connecting multiple brokers can efficiently process message routing and provide reliable and low latency communication. This paper describes the architecture and detailed operations of multiple ring-based brokers in MQTT. It also reports a prototype of the proposed system and its evaluation. Finally, the results demonstrate that this proposal is a promising and suitable approach.

    Download PDF (225K)
  • Ryochi Kataoka, Issei Kanno, Takahiro Hayashi, Naoto Tsumachi, Toshino ...
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 587-592
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: May 28, 2021
    JOURNAL FREE ACCESS

    This paper demonstrates the feasibility of interference cancellation for 5G receivers applicable for spectrum sharing with different radio systems through field experiments. In the demonstration system, the receiver cancels the signals of the existing primary radio system that are received asynchronously with respect to the 5G signal by implementing real-time signal processing on the field-programmable gate array. Through experiments, we confirm that the proposed asynchronous successive interference cancellation method can reduce interference and improve the block error rate performance significantly in the region where the received power level of the interference signal is high.

    Download PDF (4099K)
  • Wuyang Jiang, Yunlong Gao, Ying Cui, Zhi Liu
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 593-598
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: May 31, 2021
    JOURNAL FREE ACCESS

    This letter investigates the optimal tradeoff between user experience and communications and computation resource consumptions in designing efficient mobile edge computing (MEC) systems which are based on orthogonal frequency division multiple access (OFDMA) and operating in time division duplexing (TDD) mode. First, we establish a communication model for offloading scalable tasks in TDD-OFDMA systems. Then, we formulate the system utility maximization problem with respect to the service level selection and resource allocation. Finally, we propose two algorithms to obtain a globally optimal solution and a low-complexity suboptimal solution, respectively, using convex optimization and difference of convex (DC) programming.

    Download PDF (133K)
  • Jin Jiang, Chao Zhang
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 599-604
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: June 02, 2021
    JOURNAL FREE ACCESS

    Orbital Angular Momentum (OAM) is the intrinsic property of electromagnetic waves, which can be applied in wireless transmission. When OAM is applied with the traditional modulation and coding, the Euclidean space model with the OAM dimension is required. Due to the introduction of quantum OAM, the OAM can be used to enlarge the traditional Euclidean space, and need higher-order tensor space to analyze traditional multi-dimensional Euclidean space. In this paper, the high-dimension Euclidean space is established based on quantum OAM in high-order tensor model, which can be used for the optimization of the joint coding and modulation. The performances of bit error rate confirm the capability of high-dimension Euclidean space model in the corresponding signal processing.

    Download PDF (269K)
  • Jin Jiang, Chao Zhang
    Type: LETTER
    Subject area: Wireless Communication Technologies
    2021 Volume 10 Issue 8 Pages 605-610
    Published: August 01, 2021
    Released: August 01, 2021
    [Advance publication] Released: June 02, 2021
    JOURNAL FREE ACCESS

    Orbital Angular Momentum (OAM) is the intrinsic property of electromagnetic waves. Similar to the spectrum spread in the frequency domain, the OAM spread can be constructed in the OAM domain. In the Uniform Circular Array (UCA) scheme of OAM, the OAM spread turns out to be an efficient way of beam-forming to the propagation direction. In this paper, the system architecture of OAM spread transmission is highlighted with the Carrier Interferometry (CI) codes. Besides, the Multi-Loop UCA scheme combined with CI codes to generate multiple OAM modes is analyzed and evaluated. The simulation results show that the more OAM modes are multiplexed, the smaller the beam angle for beamforming. Correspondingly, the adjacent channel interference at the receiving end is smaller. In addition, the combination of OAM and Multi-Input Multi-Output (MIMO) with UCA scheme is expected to be applied in 6G.

    Download PDF (642K)
ERRATA
feedback
Top