| 1. |
- Alsharoa, A., et al.
(author)
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Trajectory optimization for multiple UAVs acting as wireless relays
- 2018
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In: 2018 IEEE International Conference on Communications Workshops, ICC Workshops 2018 - Proceedings. - : IEEE. - 9781538643280 ; , s. 1-6
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Conference paper (peer-reviewed)abstract
- This paper proposes a novel wireless relay selection scheme involving multiple mobile Unmanned Aerial Vehicles (UAVs) to support communicating ground users. The goal is to optimize the transmit power levels and trajectories of the relaying UAVs in order to maximize the data rate transmission of the ground users which are suffering from the absence of direct link. Assuming that each UAV is initially characterized by a predefined trajectory for a primary task, we propose to modify it whenever it is needed and the energy and trajectory boundaries constraints allow. We propose to solve this problem using an iterative two steps solution; first, a Mixed Integer Linear Programming (MILP) problem is formulated to optimally determine the users- UAVs associations and the UAVs' corresponding transmit power levels. In the second step, an efficient algorithm based on a recursive shrink-and-realign process is proposed to optimize the UAV trajectories. The performance of the proposed method shows advantages in terms of average throughput compared to the predefined trajectories solution.
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| 2. |
- B. da Silva Jr., Jose Mairton, 1990-, et al.
(author)
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How to Split UL/DL Antennas in Full-DuplexCellular Networks
- 2018
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In: IEEE International Conference on Communication (ICC’18). - Kansas City, MO, USA : IEEE Communications Society.
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Conference paper (peer-reviewed)abstract
- To further improve the potential of full-duplex com-munications, networks may employ multiple antennas at thebase station or user equipment. To this end, networks thatemploy current radios usually deal with self-interference andmulti-user interference by beamforming techniques. Althoughprevious works investigated beamforming design to improvespectral efficiency, the fundamental question of how to split theantennas at a base station between uplink and downlink infull-duplex networks has not been investigated rigorously. Thispaper addresses this question by posing antenna splitting as abinary nonlinear optimization problem to minimize the sum meansquared error of the received data symbols. It is shown that thisis an NP-hard problem. This combinatorial problem is dealt withby equivalent formulations, iterative convex approximations, anda binary relaxation. The proposed algorithm is guaranteed toconverge to a stationary solution of the relaxed problem with muchsmaller complexity than exhaustive search. Numerical resultsindicate that the proposed solution is close to the optimal in bothhigh and low self-interference capable scenarios, while the usuallyassumed antenna splitting is far from optimal. For large numberof antennas, a simple antenna splitting is close to the proposedsolution. This reveals that the importance of antenna splittingdiminishes with the number of antennas.
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| 3. |
- Chu, Thi My Chinh, et al.
(author)
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Non-orthogonal multiple access for DF cognitive cooperative radio networks
- 2018
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In: IEEE International Conference on Communications Workshops. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538643280 ; , s. 1-6
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Conference paper (peer-reviewed)abstract
- In this paper, we study a power domain non-orthogonal multiple access (NOMA) scheme for cognitive cooperative radio networks (CCRNs). In the proposed scheme, a secondary transmitter communicates with two secondary users (SUs) by allocating transmit powers inversely proportional to the channel power gains on the links to the respective SUs. A decode-and-forward (DF) secondary relay is deployed which decodes the superimposed signals associated with the two SUs. Then, power domain NOMA is used to forward the signals from the relay to the two SUs based on the channel power gains on the corresponding two links. Mathematical expressions for the outage probability and ergodic capacity of each SU and the overall power domain NOMA CCRN are derived. Numerical results are provided to reveal the impact of the power allocation coefficients at the secondary transmitter and secondary relay, the interference power threshold at the primary receiver, and the normalized distances of the SUs on the outage probability and ergodic capacity of each SU and the whole NOMA system. © 2018 IEEE.
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| 4. |
- Du, Rong, 1989-, et al.
(author)
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Power Allocation for Channel Estimation and EnergyBeamforming in Wirelessly Powered Sensor Networks
- 2018
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In: Proceedings of IEEE International Conference on Communications Workshops. - 9781538643280
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Conference paper (peer-reviewed)abstract
- Wirelessly powered sensor networks (WPSNs) are becoming increasingly important to monitor many internet-of-things systems. In these WPSNs, dedicated base stations (BSs) with multiple antennas charge the sensor nodes without the need of replacing their batteries thanks to two essential procedures: i) getting of the channel state information of the nodes by sending pilots, and based on this, ii) performing energy beamforming to transmit energy to the nodes. However, the BSs have limited power budget and thus these two procedures are not independent, contrarily to what is assumed in some previous studies. In this paper, we investigate the novel problem of how to optimally allocate the power for channel estimation and energy transmission. Although the problem is non-convex, we provide a new solution approach and a performance analysis in terms of optimality and complexity. We also provide a closed form solution for the case where the channels are estimated based on a least square estimation. The simulations show a gain of approximately 10% in allocating the power optimally, and the importance of improving the channel estimation efficiency.
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| 5. |
- Geraci, Giovanni, et al.
(author)
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Supporting UAV Cellular Communications through Massive MIMO
- 2018
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In: 2018 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS). - : IEEE. - 9781538643280 - 9781538643297
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Conference paper (peer-reviewed)abstract
- In this article, we provide a much-needed study of UAV cellular communications, focusing on the rates achievable for the UAV downlink command and control (C&C) channel. For this key performance indicator, we perform a realistic comparison between existing deployments operating in single-user mode and next-generation multi-user massive MIMO systems. We find that in single-user deployments under heavy data traffic, UAVs flying at 50 m, 150 m, and 300 m achieve the C&C target rate of 100 kbps - as set by the 3GPP - in a mere 35%, 2%, and 1% of the cases, respectively. Owing to mitigated interference, a stronger carrier signal, and a spatial multiplexing gain, massive MIMO time division duplex systems can dramatically increase such probability. Indeed, we show that for UAV heights up to 300m the target rate is met with massive MIMO in 74% and 96% of the cases with and without uplink pilot reuse for channel state information (CSI) acquisition, respectively. On the other hand, the presence of UAVs can significantly degrade the performance of ground users, whose pilot signals are vulnerable to UAV-generated contamination and require protection through uplink power control.
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| 6. |
- Liu, Chengpeng, et al.
(author)
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Secrecy Performance Analysis in Downlink NOMA Systems with Cooperative Full-duplex Relaying
- 2018
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In: 2018 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS). - : IEEE. - 9781538643280
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Conference paper (peer-reviewed)abstract
- We introduce the cooperative full-duplex relaying to a downlink non-orthogonal multiple access (NOMA) system and analyze the secrecy performance of each NOMA user. In particular, we enable the near NOMA user, which is close to a base station (BS), to act as a full-duplex relay for the far NOMA user, which is far away from the BS. By taking imperfect self-interference cancellation into consideration, we analytically derive the secrecy outage probabilities of both NOMA users with integral expressions. To reduce the computational complexity of both secrecy outage probabilities, we adopt approximation techniques and obtain approximated secrecy outage probabilities with closed-form expressions. Simulation results validate the correctness of our analysis and reveal that suppressing the self-interference at the full-duplex relay can enhance the secrecy performance of NOMA users. Meanwhile, simulation results demonstrate the advantages of the cooperative full-duplex relaying in the NOMA system over the OMA system.
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