Optimal Resource Allocation in Full-Duplex Wireless-Powered Communication Network (1403.2580v3)

Abstract: This paper studies optimal resource allocation in the wireless-powered communication network (WPCN), where one hybrid access-point (H-AP) operating in full-duplex (FD) broadcasts wireless energy to a set of distributed users in the downlink (DL) and at the same time receives independent information from the users via time-division-multiple-access (TDMA) in the uplink (UL). We design an efficient protocol to support simultaneous wireless energy transfer (WET) in the DL and wireless information transmission (WIT) in the UL for the proposed FD-WPCN. We jointly optimize the time allocations to the H-AP for DL WET and different users for UL WIT as well as the transmit power allocations over time at the H-AP to maximize the users' weighted sum-rate of UL information transmission with harvested energy. We consider both the cases with perfect and imperfect self-interference cancellation (SIC) at the H-AP, for which we obtain optimal and suboptimal time and power allocation solutions, respectively. Furthermore, we consider the half-duplex (HD) WPCN as a baseline scheme and derive its optimal resource allocation solution. Simulation results show that the FD-WPCN outperforms HD-WPCN when effective SIC can be implemented and more stringent peak power constraint is applied at the H-AP.

• The paper demonstrates an optimal resource allocation strategy by maximizing the weighted sum-rate under both ideal and imperfect self-interference cancellation conditions.
• It employs convex optimization for perfect SIC and an iterative algorithm for non-convex cases, ensuring robust time and power allocation in FD-WPCNs.
• Simulations indicate that FD systems can outperform HD setups under strict power constraints, underscoring the importance of efficient SIC for future wireless networks.

Overview of "Optimal Resource Allocation in Full-Duplex Wireless-Powered Communication Network"

The paper by Hyungsik Ju and Rui Zhang addresses the optimization of resource allocation in a novel wireless-powered communication network (WPCN) utilizing full-duplex (FD) capabilities. Traditional energy-constrained wireless networks rely predominantly on fixed energy inputs, such as batteries, which limits their operational lifespan. This research investigates an alternative approach by employing simultaneous wireless energy transfer (WET) and wireless information transmission (WIT) using FD systems. Here, a hybrid access point (H-AP) exploits FD technology to broadcast energy to users in the downlink (DL) while receiving information from them in the uplink (UL) utilizing time-division-multiple-access (TDMA).

Key Contributions and Methodology

1. FD-WPCN with Ideal SIC: The paper initially examines resource allocation under the assumption of perfect self-interference cancellation (SIC). The problem is modeled to maximize the weighted sum-rate (WSR) of UL information transmission by optimizing both the time and power allocations. The resulting optimization problem is determined to be convex, allowing for efficient solutions via convex optimization techniques. The paper reveals strategic allocation, where users with stronger DL/UL channels or higher priorities receive more resources.
2. FD-WPCN with Imperfect SIC: With practical limitations including residual self-interference, the problem becomes non-convex, complicating the quest for optimal solutions. The authors propose an iterative algorithm offering locally optimal solutions by adjusting the time and power allocations based on the SIC-imposed constraints.
3. Baseline HD-WPCN Analysis: As a comparative measure, the paper explores a half-duplex (HD) WPCN baseline. Here, the time-division protocol segregates WET and WIT, providing a framework to contrast the efficiency gains presented by FD operation, especially under stringent power constraints.

Numerical Results and Implications

The simulation results indicate that the FD-WPCN can outperform traditional HD setups when efficient SIC is implemented, and stricter peak power constraints are utilized at the H-AP. Especially for larger networks, the FD approach shows marked improvement in throughput, primarily when residual interference can be minimized – a significant finding given current advancements in SIC techniques capable of achieving up to 110dB interference cancellation.

Practical and Theoretical Implications

The research presents practical implications for deploying FD systems in WPCNs, considerably enhancing network longevity by energy harvesting. Theoretically, it advances our understanding of the dual role of communication signals for both data and energy transfer in wireless networks. Moreover, the work emphasizes the necessity of efficient SIC mechanisms, which remain a pivotal challenge in actualizing the potential of FD systems.

Future Directions

Future research might focus on addressing the non-convexity arising from imperfect SIC more comprehensively and exploring advanced SIC techniques or machine learning methods to further optimize resource allocation dynamically. Additionally, extending this analysis to consider multi-hop FD-WPCNs or integrating with emerging standards could broaden the practical applicability of these insights.

In summary, this paper provides a detailed exploration and methodological advancements in optimizing FD-WPCNs, posing significant implications for future wireless energy solutions. The results underline potential strategies for managing wireless resources in energy-constrained environments, signaling a substantive shift in the design and operational paradigm of future wireless networks.