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    FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    Design and Analysis of Novel Ka Band NOMA Uplink Relay System for Lunar Farside Exploration
    Jian Jiao, Yizhi He, Ye Wang, Shaohua Wu
    2020, 17(7): 1-14.
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    This paper proposes a novel Ka band non-orthogonal multiple access (NOMA) uplink relay system for Lunar farside exploration, where a satellite relay node with the help of NOMA scheme, amplifies and forwards the signal from the Earth Base Station (EBS) to a Lunar rover and a lander. We assume that the signal undergoes shadowed-Rician fading for the source-relay link and Rayleigh fading for the relay-destination link. Then, the analytical expressions for the outage probability (OP) and ergodic capacity are derived for the satellite relay node equipped with single and multiple antennas, respectively. In addition, we obtain the optimal power allocation coefficients by maximizing the sum ergodic capacity of the system, and we calculate the power consumption of the NOMA uplink relay system to achieve the same OP performance of OMA system and provide some useful guides for the design of the Earth-to-Lunar communication system. Simulations are provided to confirm the reliability of our analytical results and show the impact of various parameters on the system performance.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    Service-Driven Coded Forward Scheme Based on Streaming Transmission Model for Lunar Space Communication Networks
    Shushi Gu, Ye Wang, Guoqing Chen, Shuo Shi
    2020, 17(7): 15-26.
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    With the rapid development of lunar exploration, a large amount of scientific data and media stream service needs to be transmitted through Lunar Space Communication Networks (LSCNs). Due to limited transmitter power and intermittent, long delay and packet loss connections, the reliable and efficient multi-priority services’ transmission in LSCNs becomes an urgent problem. Firstly, we propose a Streaming Transmission Model (STM) based on temporal and spatial topology graph to describe the delay and energy consumption for data transmission in LSCNs. Then, we further devise a Coded Forward Scheme based on STM, termed CFS-STM, to achieve multi-priority service in two steps: i). Link Stability Function (LSF) is established by solving an optimization problem to choose the appropriate single-hop path. ii). Raptor code is employed to further save delay and energy with adjustable code-rate according to the different channel conditions. Experiment results show that, CFS-STM can significantly improve the transmission efficiency of multi-service priority streaming delivery in LSCNs.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    Dual-Hop Deep Space-Terrestrial FSO/RF Communication under Solar Scintillation: Performance Analysis and Challenges
    Guanjun Xu, Zhengqi Zheng, Weizhi Wang
    2020, 17(7): 27-37.
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    Deep space communication has been a fundamental guarantee for space exploration but encounters solar scintillation during superior solar conjunction. In this paper, a paradigm for deep space-terrestrial free space optical (FSO)/radio frequency (RF) communication is proposed, and the outage probability performance of the dual-hop amplify-and-forward (AF) based FSO/RF communication system is investigated. Specifically, the asymmetric dual-hop channel models are considered, where the Gamma-Gamma distribution characterizes the FSO link between the deep space probe and a relay satellite that undergoes coronal turbulence, while the RF link between the satellite and the terrestrial receiver follows the shadowed-Rician fading model due to the shadowing effect. Moreover, the closed-form expressions of the outage probability for both channel state information (CSI)-assisted and fixed gain relay systems are presented with the consideration of multiple antennas equipped on the destination, which provide practical insights to the link performance. Simulation results present the validation of our theoretical expressions and highlight a strategy for the improvement of the outage probability performance for deep space-terrestrial communication. Finally, some open issues and research directions that should be further investigated for the actual deep space communication system during superior solar conjunction are identified.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    A Publish-Subscribe Networking Architecture for Future Manned Deep Space Exploration
    Liuting Gu, Lai Yu, Wenfeng Li, Kanglian Zhao
    2020, 17(7): 38-51.
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    With the further development of the Deep Space Networking (DSN), more and more satellites and space probes will be put into space which makes the DSN more diverse and complex. We argued that Information Centric Networking (ICN) may be a suitable architecture for the DSN. In this paper, a publish-subscribe networking architecture based on ICN is proposed for future manned deep space exploration network. It adopts the publish-subscribe mechanism and decouples the control plane and data plane logically. In the proposed architecture, the improvement of routing is made to tolerant the long propagation delay and frequent link disruptions of deep space. And the multi-source transmission is considered to deal with the large amount of data in the future manned deep space exploration network. We evaluated the feasibility of the architecture and the performance of the protocol stack, the improved routing mechanism and the multi-source transmission. The results indicate that Publish-Subscribe Networking (PSN) can cope with the harsh transmission conditions, and the multi-source transmission can reduce the delivery time of data. It enables the network to allocate and share resources more efficiently and keeps the network well managed.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    A Shortest-Path Tree Approach for Routing in Space Networks
    Olivier De Jonckère, Juan A. Fraire
    2020, 17(7): 52-66.
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    A new space era is bringing deployments of thousands of networked assets in near-Earth and deep-space. Delay-Tolerant Networking (DTN) protocols and algorithms such as Contact Graph Routing (CGR) are state-of-the-art technologies certainly capable of achieving this ambitious objective. Nevertheless, in this paper, we highlight and analyze the roots of current scalability limits of CGR, to then propose more efficient alternatives. In particular, we leverage a different graph modeling approach that enables optimizations such as priority queues and spanning-tree searches in the core route determination process. While such abstract data types are difficult to adapt to CGR, we incorporate them into a novel Shortest-Path Tree Approach for Routing in Space Networks (SPSN), which is presented as a compute-efficient alternative. This paper thoroughly describes the SPSN approach including route object modeling, capacity-oriented search, and potential route management techniques. Prototype evaluations analyzed in this paper present significant evidence that SPSN outperforms legacy CGR in more than an order of magnitude in contact plans comprising thousands of contacts.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    Fault Tolerant Design of Large-Scale Digital Beam Forming in SRAM-FPGAs for Software Defined Satellite Platforms
    Zhen Gao, Jinhua Zhu, Tong Yan, Linghua Guo, Xiangping Chen, Yinqiao Li, Xiaolei Wan
    2020, 17(7): 67-79.
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    Large scale digital beamforming (LS-DBFs) are widely used in satellite communications for spectrum reuse and transmission enhancement. SRAM-FPGAs are a popular option for software defined satellite platforms due to their rich computation resources and high flexibility. However, they are sensitive to soft errors, which limit their application in space. This paper discusses the application of coding based fault tolerance schemes for the protection of LS-DBFs on software defined payloads. Since multiple FPGAs are usually needed to support the whole LS-DBFs system, different decomposition schemes are compared in terms of resource efficiency and reliability when the coding based scheme is applied to protect the DBFs on a FPGA. Theoretical analysis and hardware experiments shows that resource efficiency and reliability are a pair of contradictory requirements for decomposition schemes. The protection with vertical decomposition could improve the reliability by 96% with 1.5x redundancy. And the protection with horizontal decomposition could improve the reliability by 85% with 1.2x redundancy.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    Study on the Two-Sides Matching between Multiple Rovers and Multiple Orbiters in Mars Relay Communications
    Peng Wan, Yafeng Zhan
    2020, 17(7): 80-93.
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    In Mars relay communications, if multiple rovers and multiple orbiters are visible with each other at the same time in certain contact, there are not only issues concerned with the multiple rovers’ access to single orbiter, but also the issues concerned with the optimal access orbiter selection for each rover, which is a complex multi-objective decision-making problem relating to the resource allocation optimizations in deep-space networks. In this paper, the two-sides matching between multiple rovers and multiple orbiters in Mars relay communications is proposed based on the access preferences, taking the two-sides combined fitness of preferences and the single-side evaluation equilibrium as the optimization objectives, which utilizes the parallel capsule operations architecture encapsulated with several one-to-many two-sides matching algorithms to obtain stable multiple access matching results. Simulation results show that, our method performs better than the CCSDS Proximity-1 protocols, and could achieve the effective utilization of deep space communication network resources.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    An Optimal Bit-Rate Allocation Algorithm to Improve Transmission Efficiency of Images in Deep Space Exploration
    Yong Xu, Jionghui Li, Xiangyu Lin, Fan Bai
    2020, 17(7): 94-100.
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    As fixed compression ratio is used in traditional deep space exploration image transmission application, the same compression code rate is allocated to each image. However, since the information of each image in a space observation mission is nonuniform, the image with more information will inevitably lead to more compression distortion than the image with less information. Obviously, it’s not an efficient way to transmit information in terms of data importance or overall distortion. Therefore, we proposed a combinatorial optimal bit rate allocation algorithm to improve the efficiency of image transmission in space application. Different from traditional method, the rate-distortion model of wavelet coefficients for each image in a transmission task was built, and under the overall maximum transmission rate constraint, an bit-rate optimal allocation was applied for each image to minimize the overall distortion of a batch of images. The proposed algorithm can be widely used in image compression algorithm with embedded code stream characteristics, such as JPEG2000 and SPIHT. Experimental results shows that in the range of 2.6 to 10 compression ratio, the algorithm can reduce image distortion MSB by 40%~64% at the same overall transmission code rate, which equivalent to improvement of PSNR 3 dB to 5.4 dB.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    Non-Coherent Multi-Symbol Detection of PR-CPM for Deep Space Relay Satellites with Physical-Layer Network Coding
    Meng Wang, Chongzheng Hao, Xiaoyu Dang, Xiangbin Yu
    2020, 17(7): 101-112.
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    The demand for wireless spectrum and data transmission has increased dramatically with the rapid growth of deep-space exploration and communication. The satellite relay communication is an essential technique to solve the issues above. The method of combining Physical-layer Network Coding (PNC) with Continuous Phase Modulation (CPM) on relay satellites can improve communication efficiency and perform the collection and transmission of space data effectively. Partial-Response CPM (PR-CPM) signals possess excellent spectrum and power characteristics and are suitable for deep-space communications with limited bandwidth and massive data transmission. In this paper, a partial response non-coherent multi-symbol detection algorithm is proposed based on the Maximum-Likelihood principle. The proposed algorithm fully utilizes the memory properties of PR-CPM signals and makes decisions on specified symbols by observing a number of symbols each time. Simulation results indicate that the performance gain under the Bit Error Rate of 10-4 is about 2 dB when 5 symbols are inspected, compared with the case where the observation length is 3.
  • FEATURE TOPIC: SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION
    CGR-QV: A Virtual Topology DTN Routing Algorithm Based on Queue Scheduling
    Yaowen Qi, Li Yang, Chengsheng Pan, Hanrui Li
    2020, 17(7): 113-123.
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    In this paper, we proposed a CGR-QV algorithm in order to solve the problems of low message delivery rate and low throughput problems in deep space communication networks, which are caused by the high delay, asymmetric data transmission rate, and frequent topology switching characteristics. The proposed method separate different message types in the queues, establish the relationship between TTL, wait time and Hurst to prevent the phenomenon of “starvation” and redundancy. In view of the impact of congestion on the network, improved algorithm use the Elastic load balancing strategy establish the relationship between optimal thresholds and network performance reliability. Simulation result show that the algorithm has improved in throughput as about 19%, message delivery rate improved as about 7.5% and bandwidth rejection rate decreased as about 4.7%, the algorithm can balance the impact of topology updates and resource consumption better in space communication networks.
    • REVIEW PAPER
  • REVIEW PAPER
    An Overview of Terahertz Antennas
    Yejun He, Yaling Chen, Long Zhang, Sai-Wai Wong, Zhi Ning Chen
    2020, 17(7): 124-165.
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    The terahertz (THz) antennas, which have features of small size, wide frequency bandwidth and high data rate, are important devices for transmitting and receiving THz electromagnetic waves in the emerging THz systems. However, most of THz antennas suffer from relatively high loss and low fabrication precision due to their small sizes in high frequency bands of THz waves. Therefore, this paper presents a detailed overview of the most recent research on the performance improvement of THz antennas. Firstly, the development of THz antennas is briefly reviewed and the basic design ideas of THz antennas are introduced. Then, THz antennas are categorized as metallic antennas, dielectric antennas and new material antennas. After that, the latest research progress in THz photoconductive antennas, THz horn antennas, THz lens antennas, THz microstrip antennas and THz on-chip antennas are discussed. In particular, the practical difficulties for the development of THz antennas are discussed with promising approaches. In addition, this paper also presents a short review of the process technology of THz antennas. Finally, the vital challenges and the future research directions for THz antennas are presented.
    • COMMUNICATIONS THEORIES & SYSTEMS
  • COMMUNICATIONS THEORIES & SYSTEMS
    Multi-User File-Sharing Systems Based on LWE
    Xuyang Wang, Aiqun Hu, Hao Fang
    2020, 17(7): 166-182.
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    Multi-user file-sharing plays an important role in the cloud storage. It allows different users to share files via the cloud. However, it usually faces many security issues because the cloud is usually public and semi-trusted. To overcome these issues, we propose multi-user file-sharing systems (MFS) in this paper. According to the date sources, we propose two frameworks of MFS based on the framework of proxy re-encryption (PRE), unique source (uni-source) MFS and multi-source MFS. We formalize the security models, which contain ciphertext security, secret key security and master secret security. With the frameworks, we propose two secure and efficient MFS schemes based on LWE, the uni-source MFS UM and the multi-source MFS MM. We prove that UM is secret key and ciphertext security, and MM is secret key, master secret and ciphertext security with the hardness assumptions of LWE and SIS. Furtherly, we prove they have some useful properties, such as non-interactive and anonymous.
  • COMMUNICATIONS THEORIES & SYSTEMS
    Bidirectional Viterbi Decoding Algorithm for OvTDM
    Haocheng Wang, Yafeng Wang, Yue Hu
    2020, 17(7): 183-192.
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    Overlapped time domain multiplexing (OvTDM) is an innovative encoding scheme that can obtain high spectral efficiency. However, the intentional inter-symbol interference (ISI) caused by OvTDM will make the decoding process more complex. The computational complexity of maximum likelihood sequence detection increases exponentially with the growth of spectral efficiency in OvTDM. As a consequence of high complexity, the decoding effort for a given spectral efficiency may occasionally exceed the physical limitations of the decoder, leading inevitably to buffer overflows and information erasures. In this paper, we propose a bidirectional Viterbi algorithm (BVA) based on the bidirectional sequence decoding for OvTDM. With the BVA, the decoding operation starts simultaneously from the both ends of the corresponding trellis and stops at the middle of trellis. The simulation results show that compared with Viterbi algorithm (VA), the decoding time of BVA can be reduced by about half. And the memory space of two decoders in BVA are about half of that in VA, which means that the BVA has lower memory requirements for decoder. And the decoding performance of BVA is almost the same as VA.
  • COMMUNICATIONS THEORIES & SYSTEMS
    Making More Sense of Human Intention Detection via Reconstruction Models
    Wei Liang, Dalin Zhang, Xigang Yuan
    2020, 17(7): 193-206.
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    Movement intention recognition paves the path to developing Brain-Computer Interface (BCI) applications. Current research mostly focuses on questions like “which hand is intended to move”. While answering questions like “whether a hand is intended to move” is more desirable for widely realworld applications, because we cannot continuously perform intention tasks during usage, and the gap periods may cause unintended operation resulting in system failures. However, this kind of intention detection task is more difficult, since for a “whether” problem, it is hard to know what the “not” situation is and consequently to acquire training samples for the “not” situation. Furthermore, the occurrence of genuine intentions is comparatively scarce and unexpected, making the intention detection task hard and computation-consuming. To tackle this problem, we propose a Reconstruction-based Intention Detection (RID) framework, which utilises a reconstruction model to represent a high-level abstraction of EEG signals and leverages the reconstruction errors to determine “whether” there is a movement intention. Our framework is not only theoretically flexible and robust to any sophisticated real-world scenarios but also hand-crafted feature and domain knowledge free. Comprehensive experiments on detecting movement intention tasks with different reconstruction models demonstrate the promising performance of the proposed reconstruction intention detection framework.
    • EMERGING TECHNOLOGIES & APPLICATIONS
  • EMERGING TECHNOLOGIES & APPLICATIONS
    Investigation of Model Ensemble for Fine-Grained Air Quality Prediction
    Hong Zheng, Yunhui Cheng, Haibin Li
    2020, 17(7): 207-223.
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    Air pollution which is detrimental to people’s health is a wide spread problem across many countries around the world. Developing better air quality prediction approaches is an important research issue. Existing methods often focus on the prediction of air pollution concentrations, which is not as intuitive to the public as the air quality levels. In this paper, near future fine-grained air quality level prediction task is explored with a series of machine learning ensemble methods. Included ensemble methods are majority voting, averaging, weighted averaging and 16 different stacking tactics. To investigate the performances of these ensemble methods, comprehensive comparative experiments are conducted. Included contrast models are classical Autoregressive Integrated Moving Average (ARIMA), popular deep learning model Long Short-Term Memory (LSTM) neural network, and nine of the base-level models such as Support Vector Machine (SVM), Random Forest (RF), Logistic Regression (LR) and several boosting models. Datasets acquired from a coastal city Hong Kong and an inland city Beijing are used to train and validate all the models. Experiments show that performances of the ensemble methods outperform most of the individual models, especially when stacking with probability distributions together with engineered original features, which demonstrates the best performance.
  • EMERGING TECHNOLOGIES & APPLICATIONS
    The Analysis of Multiuser Relaying Mixed RF/FSO Networks over Exponentiated Weibull Fading Channel
    Zhengguang Gao, Jiawei Zhang, Pengfei Zhu, Yuefeng Ji
    2020, 17(7): 224-235.
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    In this paper, the performance of multiuser relaying mixed radio frequency (RF)/free space optical (FSO) networks over exponentiated Weibull Fading Channel is studied. Based on the transmit opportunistic scheduling, a unified cumulative distribution function (CDF) of the end-to-end signal to noise ratio (SNR) for multiuser dual-hop relaying system is derived. Then the average symbol error rate (ASER), outage probability and ergodic channel capacity are analyzed in detail. Furthermore, in order to simplify the analysis of system performance, the asymptotic results for the outage probability and ASER are derived at high SNR regime. We also demonstrate Monte Carlo simulation to ensure the effectiveness of the results. The simulation results show that deploying the transmit opportunistic scheme can improve the proposed system performance. And aperture averaging and heterodyne detection technique can suppress the impact of turbulence on FSO networks.
  • EMERGING TECHNOLOGIES & APPLICATIONS
    Use of NOMA for Maritime Communication Networks with P-DF Relaying Channel
    Yancheng Ji, Xiao Zhang, Guoan Zhang, Xiaojun Zhu, Qiang Sun, Wei Duan
    2020, 17(7): 236-246.
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    In this paper, a partial decode-and-forward (P-DF) cooperative relaying network (CRN) with non-orthogonal multiple access (P-DF-CRN-NOMA) for maritime space communications is proposed. Without loss of generality, three kinds of relay forwarding protocols are studied to characterize the superiority of the proposed P-DF-CRN-NOMA scheme, where, after receptions from the coastal base station (BS), the island relay forwards the successful decoded symbols to the ship user to avoid the performance loss provided by the high decoding requirement in decode-and-forward (DF). To further improve the system performance, as well as for a fairness comparison, the maximum ratio combining (MRC) is utilized at the ship user. Specifically, to present the impact of the channel qualities, the scenarios of the weak and strong links that from the source to destination (S-D) are both considered. The closed-form expressions for the outage probability of the P-DF-CRN-NOMA are derived considering the three proposed forwarding cases. Qualitative numerical results corroborating our theoretical analysis, especially for the high signal-to-noise ratio (SNR), show that the proposed P-DF-CRN-NOMA scheme significantly improves the outage probability performance in comparison to the conventional CRN-NOMA schemes. Furthermore, for an increased S-D link, the corresponding outage probability performance will be also better for all the cases.
  • EMERGING TECHNOLOGIES & APPLICATIONS
    A WiFi Fingerprint Based High-Adaptability Indoor Localization via Machine Learning
    Jianzhe Xue, Junyu Liu, Min Sheng, Yan Shi, Jiandong Li
    2020, 17(7): 247-259.
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    For received signal strength (RSS) fingerprint based indoor localization approaches, the localization accuracy is significantly influenced by the RSS variance, device heterogeneity and environment complexity. In this work, we present a high-adaptability indoor localization (HAIL) approach, which leverages the advantages of both relative RSS values and absolute RSS values to achieve robustness and accuracy. Particularly, a backpropagation neural network (BPNN) is devised in HAIL to measure the fingerprints similarities based on absolute RSS values. With this aid, the characteristics of the applied area could be specially learned such that HAIL could be adaptive to different environments. The experiments demonstrate that HAIL achieves high localization accuracy with the average localization error of 0.87m in the typical environments. Moreover, HAIL has the minimum amount of large errors and decreases the average localization error by about 30%~50% compared with the existing approaches.