Wireless Information Transfer with Opportunistic Energy Harvesting (1204.2035v2)

Abstract: Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the narrowband flat-fading channel subject to time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy opportunistically via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any time due to the practical circuit limitation. Therefore, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference condition. In this paper, we derive the optimal mode switching rule at the receiver to achieve various trade-offs between wireless information transfer and energy harvesting. Specifically, we determine the minimum transmission outage probability for delay-limited information transfer and the maximum ergodic capacity for no-delay-limited information transfer versus the maximum average energy harvested at the receiver, which are characterized by the boundary of so-called "outage-energy" region and "rate-energy" region, respectively. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control, information and energy transfer scheduling, and the receiver's mode switching. Our results provide useful guidelines for the efficient design of emerging wireless communication systems powered by opportunistic WEH.

• The paper derives an optimal mode switching strategy that balances delay-limited information transfer and energy harvesting by defining outage-energy and rate-energy regions.
• It employs channel state information with joint transmit power control and scheduling to enhance throughput and energy collection efficiency.
• Numerical results demonstrate that the optimal switching approach outperforms heuristic methods in reducing outage probability and increasing ergodic capacity.

Wireless Information Transfer with Opportunistic Energy Harvesting

This paper by Liang Liu, Rui Zhang, and Kee-Chaing Chua explores the intricate balance between wireless information transfer and energy harvesting in energy-constrained networks. The work addresses the challenge of optimizing the receiver's operation, which opportunistically switches between information decoding (ID) and energy harvesting (EH) due to the constraints in practical circuitry.

Overview of the Study

The authors consider a narrowband flat-fading channel with time-varying interference. They propose a framework for a point-to-point wireless link where the receiver lacks a fixed power supply and relies instead on wireless energy harvesting (WEH) from ambient signals. Given the single-antenna receiver's limitations, an essential aspect of the paper is determining when to switch between ID and EH modes to achieve optimal performance.

Key Contributions

• Mode Switching Optimization: The paper derives the optimal switching strategy to balance the trade-offs between delay-limited and no-delay-limited information transfer. It defines the boundaries of the "outage-energy" (O-E) region and "rate-energy" (R-E) region, characterizing achievable performance metrics in both scenarios.
• Channel State Information (CSI) Utilization: For scenarios where CSI is available at the transmitter, the paper explores joint optimization strategies involving transmit power control and scheduling alongside receiver mode switching.
• Numerical Results and Insights: The authors present numerical results, illustrating the performance differences between optimal and heuristic strategies such as periodic, interference-based, and SINR-based switching. The analysis highlights how knowledge of CSI can enhance both outage probability and ergodic capacity compared to scenarios without CSI.

Practical and Theoretical Implications

From a practical standpoint, the paper offers insights into designing systems that might be limited by energy constraints—particularly relevant for wireless sensors and IoT devices expected to operate indefinitely without manual recharging. Theoretically, the work contributes to understanding the potential for interference as a resource rather than solely a hindrance in wireless systems.

Future Directions

The implications of this paper open pathways for future exploration, including:

• Multi-user Interference Channels: Extending the current framework to multi-user scenarios where interference becomes a resource for WEH could further enhance system efficiency.
• Wide-band Interference Management: Addressing interference across wider bands can better equip the framework for real-world applications.

The paper provides a comprehensive analysis of opportunistic WEH, offering a blend of innovative theoretical insights and practical guidelines, potentially shaping the design of future energy-constrained wireless communication networks.