Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Dexin Wang
Ph.D. Final
Nov 26, 2018, 9:00 am - 11:00 am
LSC #324
SWIPT in Cooperative Networks
Abstract: In recent years, the capacity and charging speed of batteries have become the bottleneck of mobile communications systems.
Energy harvesting (EH) is regarded as a promising technology to significantly extend the lifetime of battery-powered devices.
Among many EH technologies, simultaneous wireless information and power transfer (SWIPT) proposes to harvest part of the
energy carried by the wireless communication signals. In particular, SWIPT has been successfully applied to energy-
constrained relays that are mainly or exclusively powered by the energy harvested from the received signals. These relays are
known as EH relays, which attract significant attention in both the academia and the industry.

In this research, we investigate the performance of SWIPT-based EH cooperative networks and the optimization problems
therein. Due to hardware limitations, the energy harvesting circuit cannot decode the signal directly. Power splitting (PS) is a
popular and effective solution to this problem. Therefore, we focus on PS based SWIPT in this research.

In the first part of this research, we investigate the application of SWIPT in EH relay networks under various settings. Different
from existing work that employs time-switching (TS) based SWIPT, we propose to use PS based SWIPT. As a result, our
proposed approach gives rise to a truly full-duplex (FD) EH relay network, where the information reception and transmission
take place simultaneously at the relay all the time. This more thorough exploitation of the FD feature consequently leads to a
significant capacity improvement compared with existing alternatives in the literature. Furthermore, when multiple relays are
available in the network, we explore the relay selection (RS) and network beamforming techniques in EH relay networks.
Assuming orthogonal bandwidth allocation, both single relay selection (SRS) and general relay selection (GRS) without the limit
on the number of cooperating relays are investigated and the corresponding RS methods are proposed. We will show that our
proposed heuristic GRS methods outperform the SRS methods and achieve very similar performance compared with the
optimal RS method achieved by exhaustive search but with dramatically reduced complexity. Under the shared bandwidth
assumption, network beamforming among EH relays is investigated. We propose a joint PS factor optimization method based
on semidefinite relaxation. Simulations show that network beamforming achieves the best performance among all
aforementioned techniques.

In the second part of this research, we study the problem of power allocation and PS factor optimization for SWIPT over doubly-
selective wireless channels. In contrast to existing work in the literature, we take the channel variation in both time and
frequency domains into consideration and jointly optimize the power allocation and the PS factors. The objective is to maximize
the achievable data rate with constraints on the delivered energy in a time window. Since the problem is difficult to solve directly
due to its nonconvexity, we proposed a two-step approach, named joint power allocation and splitting (JoPAS), to solve the
problem along the time and frequency dimensions sequentially. Simulations show significantly improved performance compared
with the existing dynamic power splitting scheme. A suboptimal heuristic algorithm, named decoupled power allocation and
splitting (DePAS), is also proposed with significantly reduced computational complexity and simulations demonstrate its near-
optimum performance.
Adviser: Liuqing Yang
Co-Adviser: N/A
Non-ECE Member: Haonan Wang, Statistics
Member 3: Edwin Chong, ECE
Addional Members: Jie Luo, ECE
[1] D. Wang, L. Yang, and X. Cheng, “A low-complexity cooperative algorithm for robust localization in wireless sensor networks,” in Int. Conf. Comput. Netw. Commun., Feb. 2016, pp. 1–5.

[2] D. Wang, Q. Wang, H. Cheng, and H. Huang, “An improved motion-search method based on pattern classification,” in IEEE Int. Conf. Acoust. Speech Signal Process., Mar. 2010, pp. 2134–2137.

[3] D. Wang, L. Yang, A. Florita, S. M. S. Alam, T. Elgindy, and B.-M. Hodge, “Automatic regionalization algorithm for distributed state estimation in power systems,” in IEEE Glob. Conf. Signal Inf. Process., Dec. 2016, pp. 787–790.

[4] D. Wang, R. Zhang, X. Cheng, and L. Yang, “Capacity-Enhancing Full-Duplex Relay Networks based on Power-Splitting (PS-)SWIPT,” IEEE Trans. Veh. Technol., vol. 66, no. 6, pp. 5445–5450, Jun. 2017.

[5] D. Wang and L. Yang, “Cooperative robust localization against malicious anchors based on semi-definite programming,” in IEEE Mil. Commun. Conf., Oct. 2012, pp. 1–6.

[6] A. Nelson, S. Chakraborty, Dexin Wang, P. Singh, Qiang Cui, Liuqing Yang, and S. Suryanarayanan, “Cyber-physical test platform for microgrids: Combining hardware, hardware-in-the-loop, and network-simulator-in-the-loop,” in IEEE Power Energy Soc. Gen. Meet., Jul. 2016, pp. 1–5.

[7] D. Wang, R. Zhang, X. Cheng, Z. Quan, and L. Yang, “Joint Power Allocation and Splitting (JoPAS) for SWIPT in Doubly Selective Vehicular Channels,” IEEE Trans. Green Commun. Netw., vol. 1, no. 4, pp. 494–502, Dec. 2017.

[8] D. Wang, X. Cheng, and L. Yang, “Joint Power Allocation and Splitting (JoPAS) for SWIPT in Time-Variant Wireless Channels,” in IEEE Glob. Commun. Conf., Dec. 2016, pp. 1–5.

[9] M. Karabacak, D. Wang, H. Ishii, and H. Arslan, “Mobility Performance of Macrocell-Assisted Small Cells in Manhattan Model,” in IEEE Veh. Technol. Conf. (VTC Spring), May 2014, pp. 1–5.

[10] D. Wang, R. Zhang, X. Cheng, L. Yang, and C. Chen, “Relay Selection in Full-Duplex Energy-Harvesting Two-Way Relay Networks,” IEEE Trans. Green Commun. Netw., vol. 1, no. 2, pp. 182–191, Jun. 2017.

[11] D. Wang, R. Zhang, X. Cheng, and L. Yang, “Relay Selection in Two-Way Full-Duplex Energy-Harvesting Relay Networks,” in IEEE Glob. Commun. Conf., Dec. 2016, pp. 1–6.

[12] D. Wang, L. Yang, and X. Cheng, “Underwater localization and tracking based on semi-definite programming,” in IEEE Int. Conf. Signal Process. Commun. Comput., Aug. 2013, pp. 1–5.

[13] Y. Li, X. Cheng, Y. Cao, D. Wang, and L. Yang, “Smart choice for the smart grid: Narrowband internet of things (NB-IoT),” IEEE Internet of Things Journal, vol. 5, no. 3, pp. 1505–1515, Jun. 2018.

[14] D. Wang, R. Zhang, X. Cheng, and L. Yang, “Full-duplex energy-harvesting relay networks: Capacity-maximizing relay selection,” J. Comm. and Inf. Netw., vol. 3, no. 3, pp. 79–85, Sep. 2018.

[15] ——, “Relay selection in power splitting based energy-harvesting half-duplex relay networks,” in IEEE Veh. Technol. Conf., Sydney, NSW, Australia, Jun. 2017.
Program of Study:
ECE 514
ECE 516
ECE 520
ECE 568
ECE 580A6
ECE 614
ECE 651
ECE 652