Simultaneous Information and Power Transfer for Broadband Wireless Systems (1211.6868v3)

Abstract: Far-field microwave power transfer (MPT) will free wireless sensors and other mobile devices from the constraints imposed by finite battery capacities. Integrating MPT with wireless communications to support simultaneous information and power transfer (SIPT) allows the same spectrum to be used for dual purposes without compromising the quality of service. A novel approach is presented in this paper for realizing SIPT in a broadband system where orthogonal frequency division multiplexing and transmit beamforming are deployed to create a set of parallel sub-channels for SIPT, which simplifies resource allocation. Supported by a proposed reconfigurable mobile architecture, different system configurations are considered by combining single-user/multiuser systems, downlink/uplink information transfer, and variable/fixed coding rates. Optimizing the power control for these configurations results in a new class of multiuser power-control problems featuring circuit-power constraints, specifying that the transferred power must be sufficiently large to support the operation of the receiver circuitry. Solving these problems gives a set of power-control algorithms that exploit channel diversity in frequency for simultaneously enhancing the throughput and the MPT efficiency. For the system configurations with variable coding rates, the algorithms are variants of water-filling that account for the circuit-power constraints. The optimal algorithms for those configurations with fixed coding rates are shown to sequentially allocate mobiles their required power for decoding in the ascending order until the entire budgeted power is spent. The required power for a mobile is derived as simple functions of the minimum signal-to-noise ratio for correct decoding, the circuit power and sub-channel gains.

• The paper introduces a novel SWIPT framework that leverages OFDM for simultaneous data transmission and power transfer.
• It presents a dual-antenna mobile architecture with full-duplex modes to efficiently split power between information decoding and energy harvesting.
• Comprehensive power-control algorithms are developed to enhance spectral efficiency while addressing circuit power constraints in single and multi-user environments.

Analysis of "Simultaneous Information and Power Transfer for Broadband Wireless Systems"

This paper addresses the integration of simultaneous wireless information and power transfer (SWIPT) into broadband wireless systems utilizing orthogonal frequency division multiplexing (OFDM). The authors, Kaibin Huang and Erik G. Larsson, propose a novel approach for realizing SWIPT by leveraging multiple-input multiple-output (MIMO) techniques alongside transmit beamforming to optimize the efficiency in both information transmission and microwave power transfer (MPT).

Key Contributions

1. SWIPT System Framework: The paper introduces a system model where multi-antenna base stations can communicate with multiple mobiles and simultaneously supply power. This setup involves using OFDM to partition the broadband channel into narrowband sub-channels, thus simplifying resource allocation and enabling SWIPT.
2. Reconfigurable Mobile Architecture: A dual-antenna mobile architecture is proposed to support two models: downlink and uplink information transfer. For downlink IT, the architecture splits incoming power for simultaneous energy harvesting and information decoding. For uplink IT, it operates in full-duplex mode, leveraging separate antennas for transmitting information and receiving power.
3. Power-Control Algorithms: The authors develop a comprehensive set of power-control algorithms that maximize throughput under circuit power constraints. These algorithms optimize power distribution over varying sub-channel conditions and configurations, factoring in single/multi-user environments, and variable or fixed coding rates.
4. Optimization in Various Configurations: The variation in system configurations tackles both single-user and multi-user scenarios, addressing the challenges in optimal resource allocation. The solution for single-user setups involves variants of water-filling algorithms adapted to include circuit power constraints. For multi-user setups, heuristic scheduling techniques are suggested for allocating transmit power efficiently under multiple constraints.

Theoretical Implications and Practical Relevance

From a theoretical perspective, this research extends classic information-theoretic frameworks by incorporating wireless power transfer requirements and constraints. Incorporating multi-user circuit power constraints into resource allocation notably distinguishes this work within the literature. The proposed framework confirms the feasibility of integrating SWIPT into modern broadband systems, marking a significant move towards power-sustainable communications systems.

Practically, these advancements could support ubiquitous sensor networks by alleviating battery constraints, echoing the push towards fully autonomous wireless systems. The proposed architectures and algorithms offer potent pathways for future cellular and IoT applications where traditional battery-dependent models fall short.

Numerical Results and Observations

The authors provide simulation results illustrating how the proposed power-control schemes significantly enhance spectral efficiency compared to naive power allocation strategies and time-division-based systems (TD-IPT). However, TD-IPT can outperform in specific high-circuit power scenarios where full antenna resources are better utilized. This performance metric underscores the importance of judiciously selecting between SWIPT and TD-IPT based on environmental conditions and system requirements.

Future Directions

This work opens several avenues for further research and development:

• Extended Multi-Cell Considerations: Future investigations could include cooperative SWIPT across multiple cells to improve power sharing and manage interference better.
• Adaptive Resource Management: Integrating adaptive coding schemes alongside dynamic power control can further optimize the SWIPT efficiency under realistic channel variations.
• Integration with Emerging Technologies: Exploring synergies between SWIPT systems and upcoming technologies such as massive MIMO and energy-efficient mmWave communications could unlock new levels of performance and efficiency.

In conclusion, Huang and Larsson's contribution to the SWIPT aspect in broadband systems reconciles the dual objectives of data transmission and energy efficiency, thereby expanding the horizons of wireless communication technology and its infrastructural applications.