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    COVER PAPER
  • COVER PAPER
    Junhui Zhao, Jin Liu, Lihua Yang, Bo Ai, Shanjin Ni
    2021, 18(2): 1-12.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    As a development direction of urban rail transit system, the train autonomous circumambulate system (TACS) can operate in a safer, more efficient, and more economical mode. However, most urban rail transit systems transmit signals through industrial, scientific, and medical (ISM) frequency bands or narrow frequency bands, which cannot meet the requirements of TACS. As a promising solution, the 5th generation (5G) mobile communication provides more services for the future urban rail transit systems, and covers the shortages of exiting communication technologies in terms of capacity and reliability. In this paper, we first briefly review the research status of current train control system and introduce its limitations. Next, we propose a novel network architecture, and present new technologies and requirements of the proposed architecture for TACS. Some potential challenges are then discussed to give insights for further research of TACS.
  • COMMUNICATIONS THEORIES & SYSTEMS
  • COMMUNICATIONS THEORIES & SYSTEMS
    Tao Fang, Dan Wu, Meng Wang, Jiaxin Chen
    2021, 18(2): 13-26.
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    UAV-assisted D2D networks can provide auxiliary communication for areas with poor communication facilities by using the characteristics of easy deployment of unmanned aerial vehicle (UAV), then it becomes a promising technology. However, the coexistence of UAV and D2D aggravates the conflict of spectrum resources. In addition, when the UAV performs the communication service, it will inevitably cause the location change, which will make the original channel allocation no longer applicable. Inspired by the influence of frequent channel switching on channel allocation, we define the communication utility as a tradeoff between the throughput and channel switching cost. In the considered model, we investigate the multi-stage hierarchical spectrum access problem with maximizing aggregate communication utilities in UAV-assisted D2D networks. In particular, due to the hierarchical feature of the considered network, we adopt Stackelberg game to formulate this spectrum access problem where both the throughput and channel switching cost are considered. We prove that the proposed game has a stable Stackelberg equilibrium (SE), and the heterogeneous network based channel allocation (HN-CA) algorithm is proposed to achieve the desired solution. Simulation results verify the validity of the proposed game and show the effectiveness of the HN-CA algorithm.
  • COMMUNICATIONS THEORIES & SYSTEMS
    Qiyishu Li, Xiangbin Yu, Mingfeng Xie, Ning Li, Xiaoyu Dang
    2021, 18(2): 27-39.
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    In this paper, the performance of uplink multiuser massive multiple-input multiple-output (MIMO) system with spatial modulation over transmit-correlated Rayleigh fading channel is investigated, where a large number of antennas are deployed at the base station and linear zero-forcing (ZF) receiver is employed for detection. By taking the transmit correlation and the randomness of shadow fading in to account, the bit error rate (BER) performance of the system is analyzed. According to the performance analysis, an approximated expression of overall average BER of the system is attained. Besides, asymptotic performance is studied and the corresponding BER expression at high signal-to-noise ratio is derived. On this basis, the diversity gain of the system can be obtained for performance evaluation. Simulation results show that the derived theoretical expressions match the simulated values well, which verifies the correctness of our analysis.
  • COMMUNICATIONS THEORIES & SYSTEMS
    Jiaxin Li, Zhongwen Guo, Hongyang Ma
    2021, 18(2): 40-48.
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    In this paper, we develop a novel hybrid automatic-repeat-request(ARQ) protocol for the quantum communication system using quantum stabilizer codes. The quantum information is encoded by stabilizer codes to against the channel noise. The two-photon entangled state is prepared for codeword secure transmission. Hybrid ARQ protocol rules the recognition and retransmission of error codewords. In this protocol, the property of quantum entangled state ensures the security of information, the theory of hybrid ARQ system improves the reliability of transmission, the theory of quantum stabilizer codes corrects the flipping errors of codewords. Finally, we verify the security and throughput efficiency of this protocol.
  • COMMUNICATIONS THEORIES & SYSTEMS
    Hui Che, Yong Bai
    2021, 18(2): 49-64.
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    Faster-than-Nyquist (FTN) signaling can improve the spectrum efficiency (SE) of the transmission system. In this paper, we propose a coded modulation FTN (CM-FTN) transmission scheme with precoder and channel shortening (CS) optimization to improve bit error rate (BER) performance and reduce the complexity of FTN equalizer. In our proposal, the information rate (IR) or spectral efficiency (SE) is employed and verified as a better performance metric for CM-FTN than the minimum Euclidian distance (MED). The precoder of CM-FTN is optimized for maximizing the IR criterion using the bare-bones particle swarm optimization (BB-PSO) algorithm. Further, a three-carrier CM-FTN system model is used to capture the broadening effect of precoder. Also targeting for the IR maximization, the inter-symbol interference (ISI) length for CS is optimized to reduce the receiver complexity without performance loss. Simulation results demonstrate that our method has a 0.6dB precoding gain compared with the non-precoding scheme and a maximum of 87.5\% of the complexity of FTN equalizer is reduced without BER loss.
  • COMMUNICATIONS THEORIES & SYSTEMS
    Jianfei Li, Juan Wen
    2021, 18(2): 65-85.
    Abstract ( )   Knowledge map   Save
    Scheduling schemes assign limited resources to appropriate users, which are critical for wireless network performance. Most current schemes have been designed based on saturated traffic, i.e., assuming users in networks always have data to transmit. However, the user buffer may sometimes be empty in actual network. Therefore, these algorithms will allocate resources to users having no data to transmit, which results in resource waste. In view of this, we propose new scheduling schemes for one-hop and two-hop link scenario with unsaturated traffic. Furthermore, this paper analyzes their key network performance indicators, including the average queue length, average throughput, average delay and outage probability. The two scheduling algorithms avoid scheduling the links whose buffers are empty and thus improve the network resource utilization. For the one-hop link scenario, network provides differentiated services via adjusting the scheduling probabilities of the destination nodes (DNs) with different priorities. Among the DNs with same priority, the node with higher data arrival rate has larger scheduling probability. For the two-hop link scenario, we prioritize the scheduling of relay-to-destination (R-D) link and dynamically adjust the transmission probability of source-to-relay (S-R) link, according to the length of remaining buffer. The experiment results show the effectiveness and advantage of the proposed algorithms.
  • REVIEW PAPER
  • REVIEW PAPER
    Ying Cai, Haochen Zhang, Yanfang Fan, Hongke Xia
    2021, 18(2): 86-109.
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    Opportunistic Mobile Social Networks (OMSNs) are kind of Delay Tolerant Networks (DTNs) that leverage characteristics of Mobile Ad Hoc Networks (MANETs) and Social Networks, particularly the social features, to boost performance of routing algorithms. Users in OMSNs communicate to share and disseminate data to meet needs for variety of applications. Such networks have attracted tremendous attention lately due to the data transmission requirement from emerging applications such as IoT and smart city initiatives. Devices carried by human is the carrier of message transmission, so the social features of human can be used to improve the ability of data transmission. In this paper, we conduct a comparative survey on routing algorithms in OMSNs. We first analyze routing algorithms based on three social features. Since node selfishness is not really considered previously in aforementioned routing algorithms, but has significant impact on network performance, we treat node selfishness as another social feature, classify and elaborate routing algorithms based on incentive mechanism. To assess the impact of social features on routing algorithms, we conducted simulation for six routing algorithms and analyzed the simulation result. Finally, we conclude the paper with challenges on design of routing in OMSNs and point out some future research directions.
  • NETWORKS & SECURITY
  • NETWORKS & SECURITY
    Xiang Yu, , Zhangxiang Shu, Qiang Li, Jun Huang
    2021, 18(2): 110-135.
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    Traditional multi-level security (MLS) systems have the defect of centralizing authorized facilities, which is difficult to meet the security requirements of modern distributed peer-to-peer network architecture. Blockchain is widely used in the field of access control with its decentralization, traceability and non-defective modification. Combining the blockchain technology and the Bell-LaPadula model, we propose a new access control model, named BC-BLPM, for MLS environment. The "multi-chain" blockchain architecture is used for dividing resources into isolated access domains, providing a fine-grained data protection mechanism. The access control policies are implemented by smart contracts deployed in each access domain, so that the side chains of different access domains storage access records from outside and maintain the integrity of the records. Finally, we implement the BC-BLPM prototype system using the Hyperledger Fabric. The experimental and analytical results show that the model can adapt well to the needs of multi-level security environment, and it has the feasibility of application in actual scenarios.
  • NETWORKS & SECURITY
    Dingcheng Yang, Qian Dan, Lin Xiao, Chuankuan Liu, Laurie Cuthbert
    2021, 18(2): 136-151.
    Abstract ( )   Knowledge map   Save
    Unmanned Aerial Vehicles (UAVs) acting as aerial users to access the cellular network form a promising solution to guarantee its safe and efficient operations via the high-quality communication. Due to the flexible mobility of UAVs and the coverage range limits of ground base station(GBS), the signal-to-noise ratio (SNR) of the communication link between UAVs and GBS will fluctuate. It is an important requirement to maintain the UAV's cellular connection to meet a certain SNR requirement during the mission for UAV flying from take off to landing. In this paper, we study an efficient trajectory planning method that can minimize a cellular-connected UAV's mission completion time under the connectivity requirement. The conventional method to tackle this problem adopts graph theory or a dynamic programming method to optimize the trajectory, which generally incurs high computational complexities. Moreover, there is a non-negligible performance gap compared to the optimal solution. To this end, we propose an iterative trajectory optimizing algorithm based on geometric planning. Firstly, we apply graph theory to obtain all the possible UAV-GBS association sequences and select the candidate association sequences based on the topological relationship among UAV and GBSs. Next, adopting the triangle inequality property, an iterative handover location design is proposed to determine the shortest flight trajectory with fast convergence and low computation complexity. Then, the best flight trajectory can be obtained by comparing all the candidate trajectories. Lastly, we revealed the tradeoff between mission completion time and flight energy consumption. Numerical results validate that our proposed solution can obtain the effectiveness with set accuracy and outperform against the benchmark schemes with affordable computation time.
  • NETWORKS & SECURITY
    Chengyuan Huang, Jiao Zhang, Tao Huang, Yunjie Liu
    2021, 18(2): 152-174.
    Abstract ( )   Knowledge map   Save
    The varied network performance in the cloud hurts application performance. This increases the tenant’s cost and becomes the key hindrance to cloud adoption. It is because virtual machines (VMs) belonging to one tenant can reside in multiple physical servers and communication interference across tenants occasionally occurs when encountering network congestion. In order to prevent such unpredictability, it is critical for cloud providers to offer the guaranteed network performance at tenant level.
    Such a critical issue has drawn increasing attention in both academia and industry. Many elaborate mechanisms are proposed to provide guaranteed network performance, such as guaranteed bandwidth or bounded message delay across tenants. However, due to the intrinsic complexities and limited capabilities of commodity hardware, the deployment of these mechanisms still faces great challenges in current cloud datacenters. Moreover, with the rapid development of new technologies, there are new opportunities to improve the performance of existing works, but these possibilities are not under full discussion yet. Therefore, in this paper, we survey the latest development of the network performance guarantee approaches and summarize them based on their features. Then, we explore and discuss the possibilities of using emerging technologies as knobs to upgrade the performance or overcome the inherent shortcomings of existing advances. We hope this article will help readers quickly understand the causes of the problems and serve as a guide to motivate researchers to develop innovative algorithms and frameworks.
  • NETWORKS & SECURITY
    Xiongyan Tang, Chang Cao, Youxiang Wang, Shuai Zhang, Ying Liu, Mingxuan Li, Tao He
    2021, 18(2): 175-185.
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    In 6G era, service forms in which computing power acts as the core will be ubiquitous in the network. At the same time, the collaboration among edge computing, cloud computing and network is needed to support edge computing service with strong demand for computing power, so as to realize the optimization of resource utilization. Based on this, the article discusses the research background, key techniques and main application scenarios of computing power network. Through the demonstration, it can be concluded that the technical solution of computing power network can effectively meet the multi-level deployment and flexible scheduling needs of the future 6G business for computing, storage and network, and adapt to the integration needs of computing power and network in various scenarios, such as user oriented, government enterprise oriented, computing power open and so on.
  • SIGNAL PROCESSING
  • SIGNAL PROCESSING
    Jie Wang, Zhouhua Ran, Qinghua Gao, Xiaorui Ma, Miao Pan, Kaiping Xue
    2021, 18(2): 186-199.
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    Device-free gesture recognition is an emerging wireless sensing technique which could recognize gestures by analyzing its influence on surrounding wireless signals, it may empower wireless networks with the augmented sensing ability. Researchers have made great achievements for single-person device-free gesture recognition. However, when multiple persons conduct gestures simultaneously, the received signals will be mixed together, and thus traditional methods would not work well anymore. Moreover, the anonymity of persons and the change in the surrounding environment would cause feature shift and mismatch, and thus the recognition accuracy would degrade remarkably. To address these problems, we explore and exploit the diversity of spatial information and propose a multidimensional analysis method to separate the gesture feature of each person using a focusing sensing strategy. Meanwhile, we also present a deep-learning based robust device free gesture recognition framework, which leverages an adversarial approach to extract robust gesture feature that is insensitive to the change of persons and environment. Furthermore, we also develop a 77GHz mmWave prototype system and evaluate the proposed methods extensively. Experimental results reveal that the proposed system can achieve average accuracies of 93\% and 84\% when 10 gestures are conducted in different environments by two and four persons simultaneously, respectively.
  • SIGNAL PROCESSING
    Chunyu Liu, Heli Zhang, Hong Ji, Xi Li
    2021, 18(2): 200-214.
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    Adaptive bitrate video streaming (ABR) has become a critical technique for mobile video streaming to cope with time-varying network conditions and different user preferences. However, there are still many problems in achieving high-quality ABR video streaming over cellular networks. Mobile Edge Computing (MEC) is a promising paradigm to overcome the above problems by providing video transcoding capability and caching the ABR video streaming within the radio access network (RAN). In this paper, we propose a flexible transcoding strategy to provide viewers with low-latency video streaming services in the MEC networks under the limited storage, computing, and spectrum resources. According to the information collected from users, the MEC server acts as a controlling component to adjust the transcoding strategy flexibly based on optimizing the video caching placement strategy. Specifically, we cache the proper bitrate version of the video segments at the edge servers and select the appropriate bitrate version of the video segments to perform transcoding under jointly considering access control, resource allocation, and user preferences. We formulate this problem as a nonconvex optimization and mixed combinatorial problem. Moreover, the simulation results indicate that our proposed algorithm can ensure a low-latency viewing experience for users.
  • SIGNAL PROCESSING
    Zeyu Hu, Chunjing Hu, Zexu Li, Yong Li, Guiming Wei
    2021, 18(2): 215-227.
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    The concept of edge network caching has been proposed to alleviate the excessive pressure on the core networks. Furthermore, video segment caching technology, a method to cut the whole video into segments and cache them separately, has brought a novel idea to solve the caching problem in the smaller space for massive data. The adoption of segment caching in edge networks will divide the simple video transmission process into two coupling stages because of separate data caching, which leads to more complicated resource allocation. In this paper, this problem is discussed, and its mathematical model is established to minimize the energy consumption of video transmissions. By introducing an efficient prediction window of channel fading, an optimal dynamic scheduling algorithm based on Q-learning is proposed to minimize power consumption while ensuring smooth video streaming. The proposed Q-learning algorithm is simulated and the impacts of channel state, target video bit rate and large-scale channel parameter are evaluated. Simulation results show that the proposed method can effectively reduce the total power consumption while ensuring the smooth playback of video service, thanks to the fact that the proposed method is intelligent which can effectively utilize idle resources in favorable channel states.
  • SIGNAL PROCESSING
    Jingwei Yin, Wei Men, Guangping Zhu, Xiao Han
    2021, 18(2): 228-240.
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    Cross-ice acoustic information transmission is an effective means of communication in polar sea areas covered by ice. However, the channel is extremely complicated because of the combined influence of water, ice, and air. Based on the normal-mode theory, this paper establishes a cascade acoustic channel (CAC) model for the transmission of underwater acoustic waves across ice layer. The model can calculate the displacement response of the ice layer’s upper surface by separating the upward waves from normal modes in the water and multiplying it by a transmission coefficient matrix. The relationship between the displacement response of the upper surface of ice layer and the acoustic frequency is calculated by the finite-element method, and the calculation result was consistent with that of the CAC model. To verify the applicability of the model, a cross-ice acoustic communication experiment was conducted in Songhua River in January 2019. Experimental results show the energy of the acoustic signals received by geophones is closely related to sound frequency and cross-ice acoustic communication is feasible. The result of present research is important for understanding cross-ice acoustic channel characteristics and developing future cross-ice acoustic communication in polar sea areas.
  • EMERGING TECHNOLOGLES & APPLICATIONS
  • EMERGING TECHNOLOGLES & APPLICATIONS
    Zhan Xu, Guanjie Hu, Minzheng Jia, Lan Dong
    2021, 18(2): 241-249.
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    The 5th generation mobile communications aims at connecting everything and future Internet of Things (IoT) will get everything smartly connected. To realize it, there exist many challenges. One key challenge is the battery problem for small devices, such as sensors or tags. Batteryless backscatter, also referred to as or battery-free backscatter, is a new potential technology to address this problem. One early and typical type of batteryless backscatter is ambient backscatter. Generally, batteryless backscatter utilizes environmental wireless signals to enable battery-free devices to communicate with each other. These devices first harvest energy from ambient wireless signals and then backscatter these signals so as to transmit their own information. This paper reviews the current studies about batteryless backscatter, including various backscatter schemes and theoretical works, and then introduces open problems for future research.
  • EMERGING TECHNOLOGLES & APPLICATIONS
    Meng Zhang
    2021, 18(2): 250-258.
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    With the advent of 5G era, the rise of cloud services, virtual reality/virtual reality (AR/VR), vehicle networking and other technologies has put forward new requirements for the bandwidth and delay of the bearer network. Traditional Ethernet technology cannot meet the new requirements very well. Flex Ethernet (FlexE) technology has emerged as the times require. This paper introduces the background, standardization process, functional principle, application mode and technical advantages of FlexE technology, and finally analyses its application prospects and shortcomings in 5G mobile transport network.
  • EMERGING TECHNOLOGLES & APPLICATIONS
    Jinhua Pan, Lusheng Wang, Hai Lin, Zhiheng Zha, Caihong Kai
    2021, 18(2): 259-270.
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    To support dramatically increased traffic loads, communication networks become ultra-dense. Traditional cell association (CA) schemes are time-consuming, forcing researchers to seek fast schemes. This paper proposes a deep Q-learning based scheme, whose main idea is to train a deep neural network (DNN) to calculate the Q values of all the state-action pairs and the cell holding the maximum Q value is associated. In the training stage, the intelligent agent continuously generates samples through the trial-and-error method to train the DNN until convergence. In the application stage, state vectors of all the users are inputted to the trained DNN to quickly obtain a satisfied CA result of a scenario with the same BS locations and user distribution. Simulations demonstrate that the proposed scheme provides satisfied CA results in a computational time several orders of magnitudes shorter than traditional schemes. Meanwhile, performance metrics, such as capacity and fairness, can be guaranteed.
  • EMERGING TECHNOLOGLES & APPLICATIONS
    Ahmed Jawad Kadhim, Jaber Ibrahim Naser
    2021, 18(2): 271-289.
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    Internet of Vehicles (IoV) is a new style of vehicular ad hoc network that is used to connect the sensors of each vehicle with each other and with other vehicles’ sensors through the internet. These sensors generate different tasks that should be analyzed and processed in some given period of time. They send the tasks to the cloud servers but these sending operations increase bandwidth consumption and latency. Fog computing is a simple cloud at the network edge that is used to process the jobs in a short period of time instead of sending them to cloud computing facilities. In some situations, fog computing cannot execute some tasks due to lack of resources. Thus, in these situations it transfers them to cloud computing that leads to an increase in latency and bandwidth occupation again. Moreover, several fog servers may be fuelled while other servers are empty. This implies an unfair distribution of jobs. In this research study, we shall merge the software defined network (SDN) with IoV and fog computing and use the parked vehicle as assistant fog computing node. This can improve the capabilities of the fog computing layer and help in decreasing the number of migrated tasks to the cloud servers. This increases the ratio of time sensitive tasks that meet the deadline. In addition, a new load balancing strategy is proposed. It works proactively to balance the load locally and globally by the local fog managers and SDN controller, respectively. The simulation experiments show that the proposed system is more efficient than VANET-Fog-Cloud and IoV-Fog-Cloud frameworks in terms of average response time and percentage of bandwidth consumption, meeting the deadline, and resource utilization.