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• February 2019 Vol. 16 No. 2

    

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  A Survey on Terahertz Communications

  Zhi Chen, Xinying Ma, Bo Zhang, Yaxin Zhang, Zhongqian Niu, Ningyuan Kuang, Wenjie Chen, Lingxiang Li, Shaoqian Li

  2019, 16(2): 1-35.

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  With the exponential growth of the data traffic in wireless communication systems, terahertz (THz) frequency band is envisioned as a promising candidate to support ultra- broadband for future beyond fifth generation (5G), bridging the gap between millimeter wave (mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency (IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.
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  Vehicle-to-Infrastructure Channel Characterization in Urban Environment at 28 GHz

  Longhe Wang, Bo Ai, Danping He, Ke Guan, Jiayi Zhang, Junhyeong Kim, Zhangdui Zhong

  2019, 16(2): 36-48.

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  Both ultra-reliable low latency and high-data-rate communications are required by connective vehicles. Millimeter wave (mmWave) with large bandwidth is a key technology to support high-data-rate communications. In this paper, the 28 GHz wideband vehicle-to-infrastructure channel is characterized for the urban environment in a major street in Manhattan. The deployment of the transmitter and the receiver, as well as the traffic models, are selected by considering the recommendation by 3GPP TR 37.885. Ray tracing simulator with calibrated electromagnetic parameters is employed in this work to practically conduct intensive simulations. The 3D environment model is reconstructed from OpenStreetMap. The power delay profile, path loss, root-mean-square delay spread, K-factor and so on, are extracted from the calibrated simulation results. The evolution of the parameters, as well as their statistical properties, are analyzed and modeled. The work of this paper helps the researchers understand the propagation channel for designing mmWave technologies and communication system in a similar scenario.
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  Low Complexity Joint Hybrid Precoding for Millimeter Wave MIMO Systems

  Mingyang Cui, Weixia Zou

  2019, 16(2): 49-58.

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  In millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems, hybrid precoding has been widely used to overcome the severe propagation loss. In order to improve the spectrum efficiency with low complexity, we propose a joint hybrid precoding algorithm for single-user mmWave MIMO systems in this paper. By using the concept of equivalent channel, the proposed algorithm skillfully utilizes the idea of alternating optimization to complete the design of RF precoder and combiner. Then, the baseband precoder and combiner are computed by calculating the singular value decomposition of the equivalent channel. Simulation results demonstrate that the proposed algorithm can achieve satisfactory performance with quite low complexity. Moreover, we investigate the effects of quantization on the analog components and find that the proposed scheme is effective even with coarse quantization.
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  Coalition Game Based Full-Duplex Concurrent Scheduling in Millimeter Wave Wireless Backhaul Network

  Haiyan Jiang, Yong Niu, Jiayi Zhang, Bo Ai, Zhangdui Zhong

  2019, 16(2): 59-75.

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  With the development of self-interference (SI) cancelation technology, full-duplex (FD) communication becomes possible. FD communication can theoretically double the spectral efficiency. When the time slot (TS) resources are limited and the number of flows is large, the scheduling mechanism of the flows becomes more important. Therefore, the effectiveness of FD scheduling mechanism for the flows is studied in millimeter wave wireless backhaul network with the limited TS resources. We proposed a full duplex concurrent scheduling algorithm based on coalition game (FDCG) to maximize the number of flows with their QoS requirements satisfied. We transformed the problem of maximizing the number of flows with their QoS requirements satisfied into the problem of maximizing sum rate of concurrently scheduled flows in each slot. We obtained the scheduled flows with maximum sum rate in first slot by using coalition game.And then with certain restrictions, the maximum sum rate of concurrently scheduled flows can also be achieved in subsequent time slots. The simulation results show that the proposed FDCG algorithm can achieve superior performance in terms of the number of flows that meet their QoS requirements and system throughput compared with other three algorithms.
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  A Broadband 630-720 GHz Schottky Based Sub-Harmonic Mixer Using Intrinsic Resonances of Hammer-Head Filter

  Yue He, Yaoling Tian, Li Miao, Jun Jiang, XianJin Deng

  2019, 16(2): 76-84.

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  An room temperature low noise anti-parallel Schottky diode based 630-720GHz sub-harmonic mixer (SHM) is designed, built and measured. Intrinsic resonances in low-pass hammer-head filter have been adopted to prevent the LO and RF power leak from the IF channel, while greatly minimizing the transmission line size. The mixer consists of 15um quartz terahertz circuit and 127um Al2O3 IF transformer circuit. An improved lumped element equivalent noise model of SBDs guarantees the accuracy of simulation. The measurement indicates that with local oscillating (LO) signal of 2-8 mW, the lowest double sideband (DSB) conversion loss is 8.2 dB at 645 GHz, and the best DSB noise temperature is 2800 K at 657GHz. The 3 dB bandwidth of conversion loss is 75 GHz from 638 to 715 GHz. The work IF frequency band is above 20GHz ranging from 1 to 20 GHz with -10dB return loss.
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  A Low Power, High Sensitivity SiGe HBT Static Frequency Divider up to 90 GHz for Millimeter-Wave Application

  Peigen Zhou, Jixin Chen, Pinpin Yan, Debin Hou, Wei Hong

  2019, 16(2): 85-94.

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  A layout and connection optimization for static frequency divider is presented. The layout optimization provides a new circle topology transistors placement and reasonable connection structure, which reduces the parasitic effectively and enables self-oscillation frequency enhancement. Besides, bandwidth enhancement techniques based on a center-tap capacitor in input balun design and inductive peaking in latch design are adopted to improve further high frequency performance with low power consumption. As a proof of concept, design of a divide-by-2 static frequency divider in 0.13 μm SiGe BiCMOS technology is reported. With single-ended input clock signal, the divider is measured to be operated from 40 to 90 GHz. Phase noise measurements of a 90 GHz input clock signal indicate ideal behavior with no measurable noise contribution from the divider. The divider followed by a buffer that can deliver more than -10 dBm output power, which is sufficient to drive succeeding stage. To the author’s knowledge, the divider exhibits a competitive power dissipation and the highest FOM among silicon based frequency dividers that operating higher than 70 GHz.
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  Hybrid Precoder and Combiner Design with Finite Resolution PSs for mmWave MIMO Systems

  Ran Zhang, Weixia Zou, Ye Wang, Mingyang Cui

  2019, 16(2): 95-104.

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  Hybrid precoding and combining have been considered as a promising technology, which can provide a compromise between hardware complexity and system performance in millimeter wave multiple-input multiple-output systems. However, most existing hybrid precoder and combiner designs generally assume that infinite resolution phase shifters (PSs) are used to produce the analog beamformers. In a practical scene, the design with accurate PSs can lead to high hardware cost and power consumption. In this paper, we investigate the hybrid precoder and combiner design with finite resolution PSs in millimeter wave systems. We employ alternate optimization as the main strategy to jointly design analog precoder and combiner. In addition, we propose a low complexity algorithm, where the analog beamformers are implemented only by finite resolution PSs to maximize spectral efficiency. Then, the digital precoder and combiner are designed based on the obtained analog beamformers to improve the spectral efficiency. Finally, simulation results and mathematical analysis show that the proposed algorithm with low-resolution PSs can achieve near-optimal performance and have low complexity.
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  High Resolution Radar Real-Time Signal and Information Processing

  Teng Long, Tao Zeng, Cheng Hu, Xichao Dong, Liang Chen, Quanhua Liu, Yizhuang Xie, Zegang Ding, Yang Li, Yanhua Wang, Yan Wang

  2019, 16(2): 105-133.

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  Radar is an electronic device that uses radio waves to determine the range, angle, or velocity of objects. Real-time signal and information processor is an important module for real-time positioning, imaging, detection and recognition of targets. With the development of ultra-wideband technology, synthetic aperture technology, signal and information processing technology, the radar coverage, detection accuracy and resolution have been greatly improved, especially in terms of one-dimensional (1D) high-resolution radar detection, tracking, recognition, and two-dimensional (2D) synthetic aperture radar imaging technology. Meanwhile, for the application of radar detection and remote sensing with high resolution and wide swath, the amount of data has been greatly increased. Therefore, the radar is required to have low-latency and real-time processing capability under the constraints of size, weight and power consumption. This paper systematically introduces the new technology of high resolution radar and real-time signal and information processing. The key problems and solutions are discussed, including the detection and tracking of 1D high-resolution radar, the accurate signal modeling and wide-swath imaging for geosynchronous orbit synthetic aperture radar, and real-time signal and information processing architecture and efficient algorithms. Finally, the latest research progress and representative results are presented, and the development trends are prospected.
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  How to Select the Best Sensors for TDOA and TDOA/AOA Localization?

  Yue Zhao, Zan Li, Benjian Hao, Pengwu Wan, Linlin Wang

  2019, 16(2): 134-145.

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  This paper focuses on the sensor subset optimization problem in time difference of arrival (TDOA) passive localization scenario. We seek for the best sensor combination by formulating a non-convex optimization problem, which is to minimize the trace of covariance matrix of localization error under the condition that the number of selected sensors is given. The accuracy metric is described by the localization error covariance matrix of classical closed-form solution, which is introduced to convert the TDOA nonlinear equations into pseudo linear equations. The non-convex optimization problem is relaxed to a standard semi-definite program (SDP) and efficiently solved in a short time. In addition, we extend the sensor selection method to a mixed TDOA and angle of arrival (AOA) localization scenario with the presence of sensor position errors. Simulation results validate that the performance of the proposed sensor selection method is very close to the exhaustive search method.
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  A Single-Site Positioning Method Based on TOA and DOA Estimation Using Virtual Stations in NLOS Environment

  Rui Zhang, Weiwei Xia, Feng Yan, Lianfeng Shen

  2019, 16(2): 146-159.

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  This paper presents a single-site positioning method based on the joint estimation of propagation time-of-arrival (TOA) and direction-of-arrival (DOA), with the assist of virtual stations in the typical non-line-of-sight (NLOS) environment. Consider the influence of multipath noise on the positioning performance, the proposed method firstly presents a modified high-resolution estimation technique called Multipath noise Limiting Matrix Pencil (MLMP) algorithm to achieve the TOA/DOA estimations, in which the matrix pencil and matrix enhancement process are implemented to deal with the measurements from the uniform linear array (ULA) receiver. Meanwhile, the subspace dimension estimation is improved via an adaptive threshold, for enhancing the performance of high-resolution techniques in low signal-noise-ration (SNR) situation. Next the proposed method generates virtual stations utilizing the known floor plan of surrounding reflectors, and adopts a weighted Least Square (WLS) position estimator to calculate the required position, combining the TOA/DOA estimations with the location of virtual stations. Simulations are conducted to evaluate the proposed method under NLOS conditions, and the results show that comparing with the multipath fingerprinting scheme, the proposed method has better performance in various simulation scenarios.
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  On Multicast Routing With Network Coding: A Multiobjective Artificial Bee Colony Algorithm

  Huanlai Xing, Fuhong Song, Lianshan Yan, Wei Pan

  2019, 16(2): 160-176.

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  This paper is concerned with two important issues in multicast routing problem with network coding for the first time, namely the load balancing and the transmission delay. A bi-objective optimization problem is formulated, where the average bandwidth utilization ratio and the average transmission delay are both to be minimized. To address the problem, we propose a novel multiobjective artificial bee colony algorithm, with two performance enhancing schemes integrated. The first scheme is an elitism-based food source generation scheme for scout bees, where for each scout bee, a new food source is generated by either recombining two elite solutions randomly selected from an archive or sampling the probabilistic distribution model built from all elite solutions in this archive. This scheme provides scouts with high-quality and diversified food sources and thus helps to strengthen the global exploration. The second one is a Pareto local search operator with the concept of path relinking integrated. This scheme is incorporated into the onlooker bee phase for exploring neighboring areas of promising food sources and hence enhances the local exploitation. Experimental results show that the proposed algorithm performs better than a number of state-of-the-art multiobjective evolutionary algorithms in terms of the approximated Pareto-optimal front.
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  High Speed Regular Expression Matching Engine with Fast Pre-Processing

  Zhe Fu, Jun Li

  2019, 16(2): 177-188.

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  Regular expression matching is playing an important role in deep inspection. The rapid development of SDN and NFV makes the network more dynamic, bringing serious challenges to traditional deep inspection matching engines. However, state-of-the-art matching methods often require a significant amount of pre-processing time and hence are not suitable for this fast updating scenario. In this paper, a novel matching engine called BFA is proposed to achieve high-speed regular expression matching with fast pre-processing. Experiments demonstrate that BFA obtains 5 to 20 times more update abilities compared to existing regular expression matching methods, and scales well on multi-core platforms.
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  Joint Optimization of Satisfaction Index and Spectrum Efficiency with Cache Restricted for Resource Allocation in Multi-Beam Satellite Systems

  Pei Zhang, Xiaohui Wang, Zhiguo Ma, Junde Song

  2019, 16(2): 189-201.

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  Dynamic resource allocation (DRA) is a key technology to improve system performances in GEO multi-beam satellite systems. And, since the cache resource on the satellite is very valuable and limited, DRA problem under restricted cacheresources is also an important issue to be studied. This paper mainly investigates the DRA problem of carrier resources under certain cache constraints. What’s more, with the aim to satisfy all users’ traffic demands as more as possible, and tomaximize the utilization of the bandwidth, we formulate a multi-objective optimization problem (MOP) where the satisfaction index and the spectrum efficiency are jointly optimized. A modified strategy SA-NSGAII which combines simulatedannealing (SA) and non-dominated sorted genetic algorithm-II (NSGAII) is proposed to approximate the Pareto solution to this MOP problem. Simulation results show the effectiveness of the proposed algorithm in terms of satisfaction index, spectrum efficiency, occupied cache, and etc.
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  Measures for Error Avalanche and Energy Avalanche Effect in Secure Wireless Fieldbus Systems

  Bohua Li, Yukui Pei

  2019, 16(2): 202-214.

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  The wireless fieldbus is a vital part in present industrial automatic controls and software-defined systems. Accompanying, security is an upcoming problem determines its future leapfrog development. Wireless fieldbus systems can be made secure by encrypting the data. Unfortunately, the diffusion character of encryption brings significant vulnerabilities in terms of deteriorated error performance and energy efficiency. In this paper, we first propose an AES-dependent Hsiao (AD-Hsiao) code to improve the error correction capability, which leverages the prior information of data similarity and AES decryption to assist syndrome decoding. Then, we develop “Random Coset” scheme to reduce energy consumption. Based on mapping written data into several data candidates, this scheme lessens the number of bits written to memory and thereby boosts the write energy efficiency. Simulation results show that the AD-Hsiao code can correct majority of double errors in a single codeword with limited latency and area cost as the Hamming code. Moreover, the (72,64) AD-Hsiao code improves the reliability by 102 over the (72,64) Hamming code at 8 dB AWGN channel, and also exceeding the high cost (78,64) BCH code. In addition, the “Random Coset” improves energy efficiency by 6.6~14% than the current scheme while requires small ROM storage.
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  A Localized Inter-Actuator Network Topology Repair Scheme for Wireless Sensor and Actuator Networks

  Yong Feng, Hai Liu, Jie Yang, Xiaodong Fu

  2019, 16(2): 215-232.

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  Node failure is one of the most severe problems that wireless sensor and actuator networks (WSANs) have to deal with. The failure of actuator nodes, in particular, may result in substantial consequences such as network partitioning, incorrect and incomplete decision execution for WSANs. This paper proposes an efficient localized scheme, called LANTR, to repair the damaged topology of inter-actuator network while single actuator node paralyzes. For the failure of an ordinary actuator node, LANTR can rapidly repair the topology through relocating only one-hop neighbors of the failure node, meanwhile, keep the original topology structure as much as possible. Given the magnitude of cut vertex actuators playing on the connectivity, LANTR designs a novel method for each cut vertex to select out a specific guardian node with the minimum degree or minimum cumulative degree from its neighbors, which can reduce the repair influence on the original topology and effectively reduce the coverage loss rate. The performance of the proposed scheme is evaluated and compared with several existing representative topology repair schemes, and the results indicate that LANTR can more effectively and efficiently repair the topology of inter-actuator networks.
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  Design and Implementation of an SDN-Enabled DNS Security Framework

  Zhenpeng Wang, Hongchao Hu, Guozhen Cheng

  2019, 16(2): 233-245.

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  The Domain Name System (DNS) is suffering from the vulnerabilities exploited to launch the cache poisoning attack. Inspired by biodiversity, we design and implement a non-intrusive and tolerant secure architecture Multi-DNS (MDNS) to deal with it. MDNS consists of Scheduling Proxy and DNS server pool with heterogeneous DNSs in it. And the Scheduling Proxy dynamically schedules m DNSs to provide service in parallel and adopts the vote results from majority of DNSs to decide valid replies. And benefit from the centralized control of software defined networking (SDN), we implement a proof of concept for it. Evaluation results prove the validity and availability of MDNS and its intrusion/fault tolerance, while the average delay can be controlled in 0.3s.
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  Low Transmission Overhead for Polar Coding Physical-Layer Encryption

  Hongxu Jin, Rongke Liu, Chenyu Zhang

  2019, 16(2): 246-256.

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  In this paper, for physical-layer security (PLS), a novel scheme of polar coding encryption is introduced in the wiretap channel (WTC) model. To decrease transmission overhead of the shared secret information and enhance the security performance against an attacker, we have employed the two following encryption technologies: Firstly, randomization of output bits is not dependent on the traditional randomized bit-channels but they are directly flipped through the random bit sequence. Secondly, for employing Advanced Encryption Standard (AES), we utilize the secret seed to extend an initial secret key of AES cryptosystem, which it appears a good avalanche performance. Result analyses demonstrate that the proposed scheme is strongly resistant against conventional attacks.