Joint Wireless Information and Energy Transfer in a Two-User MIMO Interference Channel (1303.1693v2)

Abstract: This paper investigates joint wireless information and energy transfer in a two-user MIMO interference channel, in which each receiver either decodes the incoming information data (information decoding, ID) or harvests the RF energy (energy harvesting, EH) to operate with a potentially perpetual energy supply. In the two-user interference channel, we have four different scenarios according to the receiver mode -- ($ID_1$, $ID_2$), ($EH_1$, $EH_2$), ($EH_1$, $ID_2$), and ($ID_1$, $EH_2$). While the maximum information bit rate is unknown and finding the optimal transmission strategy is still open for ($ID_1$, $ID_2$), we have derived the optimal transmission strategy achieving the maximum harvested energy for ($EH_1$, $EH_2$). For ($EH_1$, $ID_2$), and ($ID_1$, $EH_2$), we find a necessary condition of the optimal transmission strategy and, accordingly, identify the achievable rate-energy (R-E) tradeoff region for two transmission strategies that satisfy the necessary condition - maximum energy beamforming (MEB) and minimum leakage beamforming (MLB). Furthermore, a new transmission strategy satisfying the necessary condition - signal-to-leakage-and-energy ratio (SLER) maximization beamforming - is proposed and shown to exhibit a better R-E region than the MEB and the MLB strategies. Finally, we propose a mode scheduling method to switch between ($EH_1$, $ID_2$) and ($ID_1$, $EH_2$) based on the SLER.

• The paper presents optimal transmission strategies using rank-one beamforming to maximize RF energy harvesting in two-user MIMO interference channels.
• It employs iterative water-filling for ID mode and introduces a novel SLER-maximization method to balance rate and energy trade-offs.
• A dynamic mode scheduling mechanism is proposed to switch between mixed ID and EH configurations, enhancing overall system efficiency.

Analysis of Joint Wireless Information and Energy Transfer in Two-User MIMO Interference Channels

This paper presents an in-depth paper of joint wireless information and energy transfer (JWIET) in a two-user multiple-input multiple-output (MIMO) interference channel (IC). The research addresses a crucial aspect of simultaneous information transmission and radio-frequency (RF) energy harvesting (EH), thus catering to the increasing demand for energy-efficient wireless communication systems. Such systems are pivotal for applications in wireless sensor networks and IoT devices requiring perpetual operation without frequent battery replacements.

Research Context and Objectives

The paper focuses on a two-user MIMO IC where each receiver can function either in information decoding (ID) mode or energy harvesting (EH) mode. This setup yields four operational scenarios: ($ID_1$, $ID_2$), ($EH_1$, $EH_2$), ($EH_1$, $ID_2$), and ($ID_1$, $EH_2$). The primary objectives include deriving optimal transmission strategies that maximize the harvested energy or the achievable information rate.

Analytical Framework

1. Optimal Transmission for EH Mode: The authors derive that for the ($EH_1$, $EH_2$) scenario, the optimal transmission strategy involves rank-one beamforming at the transmitters, aligning with the strongest eigenvector of their respective channels to maximize energy transfer.
2. Strategies for ID Mode: For the ($ID_1$, $ID_2$) scenario, the work utilizes established iterative water-filling algorithms to achieve the best possible sum rate without any CSI exchange between transmitters.
3. Rate-Energy Tradeoff for Mixed Modes: When one receiver is in ID mode and the other in EH mode, the paper establishes that a rank-one beamforming strategy maximizes the rate-energy (R-E) trade-off region. It introduces maximum energy beamforming (MEB) and minimum leakage beamforming (MLB), speculating on necessary conditions for optimal performance.
4. Novel Transmission Strategy: A novel signal-to-leakage-and-energy ratio (SLER) maximization beamforming method is introduced. This approach balances the energy harvested at the EH receiver while minimizing interference at the ID receiver. The SLER scheme showcases a superior R-E region compared to MEB and MLB.
5. Mode Scheduling Strategy: The paper also proposes a mode scheduling mechanism to optimize system efficiency by dynamically switching between the mixed-mode configurations ($EH_1$, $ID_2$) and ($ID_1$, $EH_2$) based on SLER metrics.

Implications and Future Work

The research provides significant insights into designing efficient communication strategies for JWIET systems. The key findings underline the importance of a rank-one beamforming design in optimizing energy and information transfer in MIMO ICs. Optimization of R-E tradeoff curves opens avenues for implementing wireless systems that better balance data throughput with energy efficiency.

The proposed solutions, particularly the SLER maximization, can be foundational for developing future wireless communication standards incorporating energy harvesting capabilities. The implications are significant for the deployment of green communication systems aimed at reducing energy consumption while enhancing system throughput.

Conclusion

The paper successfully addresses complex transmission strategy optimization issues in two-user MIMO interference channels under joint information and energy transfer constraints. While the exact optimal R-E boundaries remain an open research question, the authors provide rigorous analysis and insightful strategies with implications for both theoretical and practical advancements in the field. Future explorations could involve extending these strategies under partial CSI constraints or exploring robust designs under channel uncertainties, contributing further to the scalability and applicability of JWIET systems.