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See detailSecure Energy Efficiency Maximization in Cognitive Satellite-Terrestrial Networks
Lu, Weixin; An, Kang; Liang, Tao et al

in IEEE Systems Journal (2021), 15(2), 2382-2385

This article investigates the secure energy efficiency (EE) optimization problem in a cognitive satellite-terrestrial network with a capable eavesdropper. The objective is to maximize the secure EE for ... [more ▼]

This article investigates the secure energy efficiency (EE) optimization problem in a cognitive satellite-terrestrial network with a capable eavesdropper. The objective is to maximize the secure EE for the primary satellite network while satisfying the allowable signal-to-interference-plus-noise ratio requirements of the secondary and primary users along within the transmit power limitation of both satellite and the terrestrial base station. Owing to the nonconvexity and intractability of the original optimization problem, a beamforming scheme and associated transformation algorithms are proposed by jointly applying the Taylor approximation, fraction programming, and alternating search to cope with the implementation difficulty. The key is to convert the original optimization problem into a simple convex framework and obtain the optimal solution step by step. Finally, numerical simulations are given to verify the feasibility and practicability of the proposed optimization algorithms. [less ▲]

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See detailOn the Secrecy Performance of NOMA-Based Integrated Satellite Multiple-Terrestrial Relay Networks With Hardware Impairments
Guo, Kefeng; An, Kang; Zhou, Feng et al

in IEEE Transactions on Vehicular Technology (2021), 70

Integrated satellite terrestrial networks and non-orthogonal multiple access (NOMA) have been confirmed to be promising and effective approaches to achieve substantial performance gains for future ... [more ▼]

Integrated satellite terrestrial networks and non-orthogonal multiple access (NOMA) have been confirmed to be promising and effective approaches to achieve substantial performance gains for future wireless paradigms. This paper studies the effect of hardware impairments (HIs) on the secrecy performance of NOMA-based integrated satellite multiple-terrestrial relay networks (ISMTRNs). Particularly, we consider two important wiretapping cases: Case I, colluding case: all eavesdroppers cooperatively overhear the information; and Case II, non-colluding case: one eavesdropper with the best wiretapping quality is chosen to overhear the main channel information. Specially, the closed-form expressions for the secrecy outage probability (SOP) of the considered NOMA-based ISMTRNs in the presence of the above two eavesdropping cases and partial relay selection scheme are obtained. To obtain further insights in high signal-to-noise ratios (SNRs) regime, the asymptotic analysis of SOP with two considered cases are also derived, which give efficient means to evaluate the benefit of NOMA scheme and the impacts of HIs on the SOP. Moreover, we obtain Monte Carlo (MC) simulations for the secrecy energy efficiency (SEE). [less ▲]

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See detailAuction-based Multi-Channel Cooperative Spectrum Sharing in Hybrid Satellite-Terrestrial IoT Networks
Zhang, Xiaokai; Guo, Daoxing; An, Kang et al

in IEEE Internet of Things Journal (2020)

In this paper, we investigate the multi-channel cooperative spectrum sharing in hybrid satellite-terrestrial internet of things (IoT) networks with the auction mechanism, which is designed to reduce the ... [more ▼]

In this paper, we investigate the multi-channel cooperative spectrum sharing in hybrid satellite-terrestrial internet of things (IoT) networks with the auction mechanism, which is designed to reduce the operational expenditure of the satellitebased IoT (S-IoT) network while alleviating the spectrum scarcity issues of terrestrial-based IoT (T-IoT) network. The cluster heads of selected T-IoT networks assist the primary satellite users transmission through cooperative relaying techniques in exchange for spectrum access. We propose an auction-based optimization problem to maximize the sum transmission rate of all primary S-IoT receivers with the appropriate secondary network selection and corresponding radio resource allocation profile by the distributed implementation while meeting the minimum transmission rate of secondary receivers of each TIoT network. Specifically, the one-shot Vickrey-Clarke-Groves (VCG) auction is introduced to obtain the maximum social welfare, where the winner determination problem is transformed into an assignment problem and solved by the Hungarian algorithm. To further reduce the primary satellite network decision complexity, the sequential Vickrey auction is implemented by sequential fashion until all channels are auctioned. Due to incentive compatibility with those two auction mechanisms, the secondary T-IoT cluster yields the true bids of each channel, where both the non-orthogonal multiple access (NOMA) and time division multiple access (TDMA) schemes are implemented in cooperative communication. Finally, simulation results validate the effectiveness and fairness of the proposed auction-based approach as well as the superiority of the NOMA scheme in secondary relays selection. Moreover, the influence of key factors on the performance of the proposed scheme is analyzed in detail. [less ▲]

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See detailErgodic Capapcity of NOMA-Based Satellite Networks with Randomly Deployed Users
Yan, Xiaojuan; Xiao, Hailin; An, Kang et al

in IEEE Systems Journal (2020), 14(3), 3343-3350

In this letter, we investigate the ergodic capacity of an uplink satellite network using a power-domain nonorthogonal multiple access (NOMA for simplicity) to serve users simultaneously in the ... [more ▼]

In this letter, we investigate the ergodic capacity of an uplink satellite network using a power-domain nonorthogonal multiple access (NOMA for simplicity) to serve users simultaneously in the consideration of random deployment of satellite users. Taking into account the deployed information of served users, we derive expression for the achievable ergodic capacity of the considered networks, where an entire link budget involving propagation loss, channel statistical prosperities, and location information is considered. Moreover, expression for ergodic capacity with OMA scheme is also derived to facilitate the performance comparison. Numerical simulation results are provided to attest the validity of theoretical results and show the vital effect of key parameters, such as the deployed information and link quality on the considered networks. [less ▲]

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See detailDelay Constrained Resource Allocation for NOMA Enabled Satellite Internet of Things with Deep Reinforcement Learning
Yan, Xiaojuan; An, Kang; Zhang, Qianfeng et al

in IEEE Internet of Things Journal (2020)

With the ever increasing requirement of transferring data from/to smart users within a wide area, satellite internet of things (S-IoT) networks has emerged as a promising paradigm to provide cost ... [more ▼]

With the ever increasing requirement of transferring data from/to smart users within a wide area, satellite internet of things (S-IoT) networks has emerged as a promising paradigm to provide cost-effective solution for remote and disaster areas. Taking into account the diverse link qualities and delay qualityof- service (QoS) requirements of S-IoT devices, we introduce a power domain non-orthogonal multiple access (NOMA) scheme in the downlink S-IoT networks to enhance resource utilization efficiency and employ the concept of effective capacity to show delay-QoS requirements of S-IoT traffics. Firstly, resource allocation among NOMA users is formulated with the aim of maximizing sum effective capacity of the S-IoT while meeting the minimum capacity constraint of each user. Due to the intractability and non-convexity of the initial optimization problem, especially in the case of large-scale user-pair in NOMA enabled S-IoT. This paper employs a deep reinforcement learning (DRL) algorithm for dynamic resource allocation. Specifically, channel conditions and/or delay-QoS requirements of NOMA users are carefully selected as state according to exact closed-form expressions as well as low-SNR and high-SNR approximations, a deep Q network is first adopted to yet reward and output the optimum power allocation coefficients for all users, and then learn to adjust the allocation policy by updating the weights of neural networks using gained experiences. Simulation results are provided to demonstrate that with a proper discount factor, reward design, and training mechanism, the proposed DRL based power allocation scheme can output optimal/near-optimal action in each time slot, and thus, provide superior performance than that achieved with a fixed power allocation strategy and orthogonal multiple access (OMA) scheme. [less ▲]

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See detailThe Application of Power-Domain Non-Orthogonal Multiple Access in Satellite Communication Networks
Yan, Xiaojuan; An, Kang; Liang, Tao et al

in IEEE Access (2019), 7

Satellite communication networks are expected to be indispensable as part of an integrated complement for the upcoming 5G networks since they can provide the most comprehensive coverage and reliable ... [more ▼]

Satellite communication networks are expected to be indispensable as part of an integrated complement for the upcoming 5G networks since they can provide the most comprehensive coverage and reliable connection for areas where are economically unviable and/or difficult to deploy terrestrial infrastructures. Meanwhile, the power-domain non-orthogonal multiple access (NOMA), which can serve multiple users simultaneously within the same time/frequency block, has been viewed as another promising strategy used in the 5G network to provide high spectral efficiency and resource utilization. In this paper, we introduce a general overview of the application of the NOMA to various satellite architectures for the benefits of meeting the availability, coverage, and efficiency requirements targeted by the 5G. The fundamental and ubiquitous features of satellite link budget are first reviewed. Then, the advantage and benefit of introducing the NOMA scheme in various satellite architectures, such as conventional downlink/uplink satellite networks, cognitive satellite terrestrial networks, and cooperative satellite networks with satellite/terrestrial relays, are provided, along with the motivation and research methodology for each scenario. Finally, this paper reviews the potential directions for future research. [less ▲]

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See detailOn the Performance of the Uplink Satellite Multiterrestrial Relay Networks With Hardware Impairments and Interference
Guo, Kefeng; An, Kang; Zhang et al

in IEEE Systems Journal (2019), 13(3), 2297-2308

In this paper, we consider an uplink satellite multiterrestrial relay network, which employs a single-antenna user to communicate with a satellite via multiple decode-and-forward (DF) terrestrial relays ... [more ▼]

In this paper, we consider an uplink satellite multiterrestrial relay network, which employs a single-antenna user to communicate with a satellite via multiple decode-and-forward (DF) terrestrial relays. Due to the spectrum sharing policy, terrestrial relays are interfered by cochannel interference (CCI). For inevitable radio frequency (RF) front-end imperfections, the interconnected nodes of the whole network are always impaired by inherent hardware impairments (HIs). Specifically, in order to improve the overall system performance, a partial relay selection scheme is used to enhance the system performance by improving the spatial diversity. On this foundation, we have derived the closed-form expressions for the outage probability (OP) and throughput of the considered system, where both the satellite and terrestrial channels are under independent nonidentical distributions. To get better insights at high signal-to-noise-ratios (SNRs), the asymptotic behaviors for the system performance are also derived. From the asymptotic results, the impacts of CCI and the HIs on the system performance are quantitatively analyzed. Especially, the OP and throughput will have bounds when the system is under HIs. Monte Carlo (MC) simulation results corroborate the theoretical analysis and illustrate the joint effects of CCI and HIs on the considered system. [less ▲]

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