Wireless Powered Communication Networks: An Overview (1508.06366v2)

Abstract: Wireless powered communication network (WPCN) is a new networking paradigm where the battery of wireless communication devices can be remotely replenished by means of microwave wireless power transfer (WPT) technology. WPCN eliminates the need of frequent manual battery replacement/recharging, and thus significantly improves the performance over conventional battery-powered communication networks in many aspects, such as higher throughput, longer device lifetime, and lower network operating cost. However, the design and future application of WPCN is essentially challenged by the low WPT efficiency over long distance and the complex nature of joint wireless information and power transfer within the same network. In this article, we provide an overview of the key networking structures and performance enhancing techniques to build an efficient WPCN. Besides, we point out new and challenging future research directions for WPCN.

• The paper introduces WPCNs that leverage microwave wireless power transfer to replace manual battery management and enhance device longevity.
• It evaluates key performance techniques such as energy beamforming, joint scheduling, and cooperative relaying to optimize energy and data transmission.
• The study discusses challenges like the doubly-near-far problem and outlines future directions including full-duplex solutions and green energy integration.

Overview of Wireless Powered Communication Networks

This paper provides a comprehensive analysis of Wireless Powered Communication Networks (WPCNs), which leverage microwave wireless power transfer (WPT) technology to remotely replenish the batteries of wireless communication devices. This paradigm replaces conventional manual battery management with remote charging, promising enhancements in throughput, device longevity, and operational costs. However, significant challenges persist, including the inefficiency of WPT over distances and complex integration of simultaneous wireless information and power transfer.

Key Concepts and System Models

The paper details basic structures and models employed in WPCNs. The architecture comprises dedicated Energy Nodes (ENs) that broadcast energy to Wireless Devices (WDs), which utilize this energy to transmit data to Access Points (APs). A key distinction is made between systems with separated ENs and APs versus integrated Hybrid Access Points (HAPs). Although combining ENs and APs into HAPs simplifies coordination, it also introduces the "doubly-near-far" problem, which can lead to significant performance discrepancies among WDs based on their relative distance to HAPs.

Energy and information transmissions are categorized as either out-band or in-band. The former avoids interference by using separate frequencies for energy and information, while the latter, considered more spectrum-efficient, allows for concurrent use of the same frequency band at the cost of potential co-channel interference.

Performance Enhancement Techniques

Several strategies to augment WPCN performance are explored:

1. Energy Beamforming: Utilizes antenna arrays to direct energy efficiently towards WDs, requiring precise channel state information (CSI) for optimization. Techniques like reverse-link training and feedback mechanisms are crucial, especially given the energy constraints on WDs.

2. Joint Communication and Energy Scheduling: Proposes dynamic allocation of time-frequency resources to balance energy delivery and data transmission. This approach is responsive to real-time conditions, such as channel variations and device energy states, aiming to mitigate issues like the doubly-near-far problem.

3. Wireless Powered Cooperative Communication: Introduces cooperative strategies among WDs, like relaying data for distant nodes. This method leverages localized energy availability and inter-device cooperation to maximize overall network efficiency.

4. Multi-node Cooperation: Describes collaboration among multiple ENs and APs through centralized coordinated processing, akin to MIMO and CoMP techniques, offering significant gains in energy distribution and data throughput.

Future Directions and Challenges

The paper outlines potential extensions and future research avenues:

• Advanced Beamforming: Requires developing algorithms to handle imperfect CSIT and adaptive beamforming methods, accounting for nonlinear energy conversion.
• Full-Duplex Solutions: Encourages exploration into full-duplex communication and energy transfer systems, which promise more efficient resource usage despite requiring sophisticated interference management.
• Cluster-Based Architectures: Suggests the potential for cluster-head nodes within large WPCNs to balance the energy needs and communication tasks among multiple WDs.
• Green and Cognitive WPCNs: Highlights prospects for integrating renewable energy sources into WPCNs to reduce reliance on fixed power while simultaneously managing coexistence with other networks, fostering cooperative approaches in spectrum management.

Conclusion

This thorough exploration of WPCN illustrates its potential as a transformative solution for sustainable wireless communication. The various strategies and models proposed offer a framework for overcoming current limitations, paving the way for more efficient and self-sustaining networks. Continued research in this arena is poised to yield practical innovations and broaden the application scope of WPCNs.