Domain Adaptive Transfer Attack (DATA)-based Segmentation Networks for Building Extraction from Aerial Images

Semantic segmentation models based on convolutional neural networks (CNNs) have gained much attention in relation to remote sensing and have achieved remarkable performance for the extraction of buildings from high-resolution aerial images. However, the issue of limited generalization for unseen images remains. When there is a domain gap between the training and test datasets, CNN-based segmentation models trained by a training dataset fail to segment buildings for the test dataset. In this paper, we propose segmentation networks based on a domain adaptive transfer attack (DATA) scheme for building extraction from aerial images. The proposed system combines the domain transfer and adversarial attack concepts. Based on the DATA scheme, the distribution of the input images can be shifted to that of the target images while turning images into adversarial examples against a target network. Defending adversarial examples adapted to the target domain can overcome the performance degradation due to the domain gap and increase the robustness of the segmentation model. Cross-dataset experiments and the ablation study are conducted for the three different datasets: the Inria aerial image labeling dataset, the Massachusetts building dataset, and the WHU East Asia dataset. Compared to the performance of the segmentation network without the DATA scheme, the proposed method shows improvements in the overall IoU. Moreover, it is verified that the proposed method outperforms even when compared to feature adaptation (FA) and output space adaptation (OSA).Comment: 11pages, 12 figure

Cross Layer Optimization of Wireless Control Links in the Software-Defined LEO Satellite Network

The low earth orbit (LEO) satellite network can benefit from software-defined networking (SDN) by lightening forwarding devices and improving service diversity. In order to apply SDN into the network, however, reliable SDN control links should be associated from satellite gateways to satellites, with the wireless and mobile properties of the network taken into account. Since these characteristics affect both control link association and gateway power allocation, we define a new cross layer SDN control link problem. To the best of our knowledge, this is the first attempt to explore the cross layer control link problem for the software-defined satellite network. A logically centralized SDN control framework constrained by maximum total power is introduced to enhance gateway power efficiency for control link setup. Based on the power control analysis of the problem, a power-efficient control link algorithm is developed, which establishes low latency control links with reduced power consumption. Along with the sensitivity analysis of the proposed control link algorithm, numerical results demonstrate low latency and high reliability of control links established by the algorithm, ultimately suggesting the feasibility, both technical and economical, of the software-defined LEO satellite network. © 2019 BMJ Publishing Group. All rights reserved.1

Performance Evaluation of High-Frequency Mobile Satellite Communications

Communication satellites have a much longer propagation delay than terrestrial communication networks such as cellular or WiFi. In addition, as the carrier frequency moves up, mobile satellite communications show worse performances than the conventional fixed satellite communications. The mobile satellite service (MSS) has not been actively pursued with long latency at high-frequency bands for future applications. In this paper, the adverse impact of long propagation delay in the conventional satellite system is investigated with various user mobility and Doppler-shifted carrier frequency. The satellite network is modeled as a basic delayed feedback channel system and the communication performance is analyzed under delayed channel state information (CSI) for assessing the system feasibility in mobile conditions. The results of performance analysis are provided at high-frequency bands with high-speed user movement, specifically on the outage probability and the channel capacity exploiting three types of channel models: conventional land mobile satellite (LMS) channel models of E. Lutz and C. Loo, and Nakagami fading model. In the circumstance with various user speeds, system performances are evaluated with different propagation delays in the LMS channel models and for line-of-sight (LOS) components in the Nakagami fading. In addition, the conventional models are compared depending on different altitudes for geostationary orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO) satellites, as well as high-altitude platforms (HAP). © 2019 IEEE.1

Cross-layer optimization for satellite-terrestrial heterogeneous networks

The advanced multibeam satellite equipped with phased array antenna can effectively serve a large number of users over its coverage area by beamforming narrow spotbeams and managing interbeam interference. In this paper, we in-vestigate a cross-layer scheme of resource allocation and user scheduling when the multibeam satellite has a choice between routing signals to a ground gateway/feeder antenna/gap filler or sending directly to end user terminals. The satellite scheduler faces a problem of choosing a better signal path by considering transmission diversity to improve reliability and throughput. We solve a general utility problem based on channel conditions and potential interbeam interference that is primarily determined by geographical distribution of users and gateway locations. The optimum solution chooses users to be served at each transmit opportunity and the optimum transmission strategy that gives the highest marginal return of the utility in terms of transmit power allocation and signal path selection. Our cross-layer optimized scheme for satellite-terrestrial heterogeneous networks takes into joint account the PHY layer beamforming, the MAC layer scheduling, and the Network layer routing path selection. From the optimum scheduling policy, a computationally efficient algorithm is proposed. Simulation results show that the use of gateway/feeder antenna can increase the sum capacity of the multibeam satellite regardless of the interference level

Connectivity Analysis of Mega Constellation Satellite Networks with Optical Inter-Satellite Links

Recently, low earth orbit (LEO) satellite-based systems have attracted tremendous attention and various technologies have been developed for payload miniaturization and optical communications. In addition, mega-constellation architectures are expected to be deployed with LEO satellites for global broadband networks. In this article, we present a thorough analysis of mega-constellation architecture in terms of a change in the number of visible satellites and antenna steering capability to investigate the impact of increase in the constellation size and adoption of optical intersatellite links. The network architecture is evaluated with respect to satellite antenna steering capability and the satellite visibility considering the very narrow beam divergence of optical communications. We analyze the impact of a change in relative positions among the satellites due to continuous satellite movement in the constellation. The results offer guidelines for designing a novel visibility matrix using a time-varying satellite topology. This could defuse the problem of the conventional studies using fixed visibility matrices. The proposed time-varying visibility matrix achieves better performance than the previous preassigned links in terms of end-to-end link distance and hop count of LEO satellite networks. © 1965-2011 IEEE.1

Resource allocation and user scheduling for a multibeam satellite with signal path diversity

The advanced multibeam satellite equipped with phased array antenna can effectively serve a large number of users over its coverage area by beamforming narrow spotbeams and managing interbeam interference. In this paper, we investigate a scheme of resource allocation and user scheduling when the multibeam satellite has a choice of routing signals to a gateway/feeder antenna or sending directly to end user terminals. The satellite scheduler faces a problem of choosing a better signal path by considering transmission diversity to improve reliability and throughput. We formulate a general utility problem and give a resource allocation and user scheduling solution based on channel conditions and potential interbeam interference that is primarily determined by geographical distribution of users and gateway locations. By comparing direct transmission to users and routing via gateway/feeder antenna, the scheduler chooses users to be served at each transmit opportunity and the optimum transmission strategy that gives the highest marginal return of the utility in terms of transmit power allocation and signal path selection. From the optimum scheduling policy, a computationally efficient algorithm is proposed. Simulation results show that the use of gateway/feeder antenna can increase the sum capacity of the multibeam satellite regardless of the interference level

Modeling and Analysis of Solar Power Relays for Space-Terrestrial Heterogeneous Networks

The space-based solar power transmission from satellites has been a long-term project and is finally planned to be realized in a few decades. Space-terrestrial heterogeneous networks can feed solar power from the space to large rectennas (rectifying antennas) located in unpopulated areas, and then distribute to each user through terrestrial power line or wireless links. In this paper, as a step stone for implementing economically feasible end-to-end solar power transmission from satellites to end-users, we focus on the modeling of solar power relays from satellites to terrestrial power grids via ground rectennas for space-terrestrial heterogeneous networks. We survey the mathematical model of the terrestrial smart grid power system, apply it to the satellite for space-based solar power transmission, and model solar power relays for ultimate integration of space power satellite and Earth smart grid. Compared to the terrestrial power delivery system, we identify distinct features for space power transmission, and formulate a joint problem of making decisions on solar power generation and resource allocation for rectenna feed

End-To-End Reliability of Satellite Communication Network Systems

Satellite communication networks with onboard processing (OBP) satellites can provide high-speed data transmission rates and global service coverage with reduced propagation delays. This article proposes a means of analyzing the quantitative reliability of the satellite communication network systems. First, we identify the four major factors that affect the quality of network services: the OBP states, uplink channels, downlink channels, and uplink packet collision losses. Based on these four factors, a Markov model is derived to analyze the probability distributions of various network states. Analytic results show the network reliability with respect to the OBP structures and space radiation environments. The relationship between network reliability and throughput according to the packet traffic load is also quantitatively analyzed. Finally, based on the developed model, a method is suggested for iteratively updating the reliability distribution of network systems affected by changes in the four factors as well as network access time changes. The numerical results show an indication of the satellite network reliability to provide references whether adjusted elements of the four factors are eligible to sustain reliable end-to-end services.1

Challenges for Efficient and Seamless Space-Terrestrial Heterogeneous Networks

By interconnecting satellites in the sky with ground stations on earth, space-terrestrial networks can extend the coverage area and increase the throughput for both commercial and nonprofit applications. To realize the seamless and economic sky-to-earth networks, we still have to advance the technologies that bridge different types of channels, and find killer-applications that are essential for our life. In this article we review the current state-of-the-art technologies of multibeam satellites and relaying as fundamental cornerstones, and then address the issues of low-latency random access, mobility support, and multipath protocols for realizing a seamless heterogeneous network. We then illustrate two impactful applications: for emergency communication as a near-future and non-profit application, and for simultaneous transmission of information and power as a long-term application.close0

Sensing Coverage-Based Cooperative Spectrum Detection in Cognitive Radio Networks

With the advancement of the Internet of Things (IoT), conventional principles of spectrum allocation cannot mitigate spectrum depletion so that a cognitive radio technology is proposed as a solution. The hidden primary user (PU) problem, however, is a critical issue in cognitive radio networks, because spectrum sensing nodes (SNs) can misclassify spectrum occupancy. To cope with this, machine learning-based cooperative spectrum sensing schemes (CSSs) have been proposed. The CSSs without considering the node placement, however, are still faced with the hidden PU problem. In this paper, we present how to place SNs to guarantee the performance of machine learning-based CSSs. We verify that the hidden PU problem makes the overlap of data distribution, which deteriorates the spectrum sensing ability. Based on the Kullback-Leibler divergence, analytical expressions for the spectrum sensing coverage of a single SN are derived. Then, we propose a strategy on how to place a few SNs to cover the whole area of the PU and prove the feasibility of our proposal by the experiment results.1