SWIPT: Wireless Info & Power Transfer

Updated 15 November 2025

SWIPT is a wireless technique that simultaneously transmits data and energy, enabling devices to be self-powered.
It employs receiver architectures like time switching, power splitting, and integrated designs to optimize information decoding and energy harvesting.
Advanced network designs use joint resource allocation, innovative modulation, and MIMO techniques to balance rate-energy trade-offs and enhance system performance.

Simultaneous Wireless Information and Power Transfer (SWIPT) refers to the fundamental capability of wireless networks to deliver both information and usable energy over the same radiative wireless medium, to one or more receiver nodes. SWIPT encompasses a set of system models, device architectures, resource allocation strategies, and modulation/receiver techniques that deliberately exploit the dual nature of electromagnetic signals to achieve simultaneous communication and energy harvesting. It has emerged as a critical enabler for the deployment of self-powered wireless devices, ultra-low-maintenance sensor networks, and next-generation communication infrastructure.

1. Fundamental Principles and System Models

At the core of SWIPT lies the transmission of modulated electromagnetic waves that carry both energy (in the classical RF sense) and digital information. The receiver's architecture is engineered to extract a portion of the received signal's power for DC conversion (energy harvesting, EH), while decoding the modulated information symbols (information decoding, ID) from the same or another fraction. The principal system models span the following domains:

Narrowband/multicarrier point-to-point and multiuser links, modeled as $y = hx + z$ , where $x$ is the information-bearing symbol and $h$ the wireless channel coefficient.
MIMO systems with advanced smart antenna processing, where spatial beamforming can be exploited to direct energy and information to different users or locations (Ding et al., 2014).
Optical-wireless links employing resonant beam or external-cavity designs, in which the laser-induced optical field acts as a joint information and power carrier (Fang et al., 2021, Bai et al., 2021).
Relay-based networks and multi-hop cooperative systems, where the relays themselves may be energy-constrained and rely on SWIPT mechanisms (DI et al., 2015, DI et al., 2014, Liu, 2016).

Receiver Models

The receiver partitioning between energy and information extraction fundamentally shapes achievable trade-offs. Common architectures include:

Time Switching (TS): Alternates between all-EH and all-ID over time (Krikidis et al., 2014).
Power Splitting (PS): Splits received RF power with fraction $\rho$ for EH and $1-\rho$ for ID.
Antenna or Spatial Switching (AS/SS): Allocates subsets of antennas or spatial eigenmodes separately for EH and ID (Ding et al., 2014).
Integrated Receivers: Use rectification before any signal splitting, exploiting modulation schemes tailored for post-rectifier detection (Kim et al., 2021).

2. Achievable Rate–Energy Trade-offs and Analytical Models

The central performance question in SWIPT is the rate–energy (R–E) trade-off: for a fixed channel, what is the achievable region of (information rate, harvested energy) pairs as system parameters are varied? The precise boundary is dictated by:

Receiver architecture: TS, PS, AS, integrated, thermal-based, or hybrid.
Resource allocation: Power control, beamforming, subcarrier/antenna assignment, and scheduling strategies.
Physical-layer modulation & waveform design: Multitone PSK, high-PAPR schemes, deterministic vs. Gaussian signaling (Dhull et al., 27 Aug 2024, Kim et al., 2021, Luo et al., 12 Sep 2025).

For a PS receiver, the region is characterized by: $\left\{ (R, E): \begin{aligned} & R = \log_2\left(1 + \frac{(1-\rho)|h|^2 P_s}{N_0}\right) \ & E = \eta \rho |h|^2 P_s,\;\; 0 \leq \rho \leq 1 \end{aligned} \right\}$ for a narrowband link with transmit power $P_s$ and conversion efficiency $\eta$ .

In MIMO, the Pareto boundary is found by jointly optimizing the transmit covariance matrix and splitting ratios, often using convex-optimization (SDR/relaxation) and alternating methods (Krikidis et al., 2014, Ding et al., 2014).

In relay and cooperative systems, the bottleneck is the ability of the relay(s) to both decode and accrue sufficient energy for forwarding, giving rise to more intricate max-min rate formulations that depend on joint splitting, scheduling, and allocation (DI et al., 2015, Liu, 2016, DI et al., 2014, Zawawi et al., 2015).

3. Practical Transceiver and Modulation Architectures

Rectenna Design: Rectifying antennas (rectennas) are essential for RF-DC conversion. The nonlinear transfer characteristic (e.g., $I_D = I_s(e^{v_D/nV_T} - 1)$ ) introduces strong dependence on the shape and statistical properties of the input waveform, motivating energy-centric waveform and modulation design.

Integrated Receivers and High-PAPR Modulation: Recent work introduces PPM and high-PAPR waveforms, which maximize the fourth-order rectifier response, yielding significantly higher DC power compared to constant-envelope or classical modulations (Kim et al., 2021). Experimental results confirm up to $2.6\times$ gains in DC power for 8-PPM vs. CW.

Multitone and PSK schemes: Multitone PSK exploits rectifier nonlinearity to balance PCE (power conversion efficiency) and BER, achieving up to $40\%$ PCE at $-6$ dBm input and good BER at moderate tone and phase order (Dhull et al., 27 Aug 2024). Carefully designed tone spacing and phase intervals minimize input-circuit "ripple" and optimize DC extraction.

Diplexer-Based and Non-Orthogonal Splitting: Architecture advances include diplexer-based receivers, which naturally split mixing products into baseband (ID) and doubling-frequency (EH) components, achieving a SWIPT power-splitting factor of $0.5$ under idealized assumptions (Qin et al., 2016).

Temperature-Based Paradigms: A distinct approach encodes information and power in thermal fluctuations induced by the RF signal, producing a virtual MIMO channel with memory, optimizing rate and average harvested energy without explicit splitting (Faddoul et al., 26 Mar 2024).

4. Resource Allocation and Network-Level Design

Resource Allocation: The concurrent delivery of information and power introduces complex cross-layer optimization. State-of-the-art methods provide:

Joint power, subcarrier, and pairing assignment in OFDMA or multi-cell SWIPT networks, maximizing the sum harvested energy or network throughput under user-specific constraints (Jalali, 2020, DI et al., 2014).
Mixed-integer and D.C. programming formulations to accommodate discrete variables in subcarrier or antenna assignment, dual decomposition, and MM algorithms for tractability.
Energy-aware beamforming and null-space techniques in coordinated/multiuser MIMO, often relying on low-complexity null-space designs that avoid unnecessary dedicated energy beams unless specially designed deterministic waveforms are used (Luo et al., 12 Sep 2025).

Relay Positioning and Relaying Protocols: In relay-based SWIPT, the relay should be physically closer to the source (harvesting node) as opposed to the classic mid-point deployment, due to the path loss in energy transfer (DI et al., 2014, DI et al., 2015). Use of rateless codes and mutual-information accumulation at the destination improves both rate and E2E robustness (DI et al., 2015).

New Physical Layers: Emerging concepts include fluid antennas for positional adaptation of the energy/information beams, and pinching-antenna systems that exploit physical movement of antennas along waveguides to optimize the spatial energy and information field (Zhang et al., 23 Oct 2025, Li et al., 26 Apr 2025).

5. Performance Benchmarks and Experimental Results

Optical SWIPT: Resonant beam free-space systems achieve $\sim$ 4.2 W DC power and $12.41$ bps/Hz spectral efficiency at $L=1$ m with $P_{in}=200$ W, far exceeding typical RF SWIPT figures (multi-watt vs. milliwatt regime, double-digit spectral efficiency) (Fang et al., 2021). At longer ranges ( $d=20$ m), electrical power and spectral efficiency up to $9$W and $18$bps/Hz are observed using transfer-matrix/eigenmode-stability theory for beam design (Bai et al., 2021).
RF SWIPT Experimental Platforms: PPM-integrated receiver SWIPT at 2.4 GHz shows that $4$-PPM can provide nearly $2\times$ the harvested DC power of a CW signal, while supporting $\sim$ 1–3 Mbps with sub-$10$ μW to mW harvested (realized with low-power ADC and low-complexity DSP) (Kim et al., 2021).
Resource Allocation Gains: Jointly optimized spectrum and power allocation in OFDMA SWIPT yields $20$– $50\%$ harvested energy gain over heuristic or decoupled schemes. Antenna switching in multi-antenna receivers further increases energy or rate per user by up to $25$– $40\%$ (Jalali, 2020).
Trade-offs: Increasing transmission range or reducing aperture size reduces E2E optical SWIPT efficiency, while PS or TS architectures always require explicit optimization to balance user-specific information and power needs.

6. Advanced SWIPT Network Architectures and Emerging Directions

Full-Duplex MISO SWIPT: Joint optimization of BS beamforming, MS-side power splitting, and uplink transmit power in full-duplex regimes promises further reductions in total transmit power and spectral/energy efficiency trade-off envelopes, with robust performance possible even under CSI imperfections via SDR/zero-forcing hybrid solutions (Okandeji et al., 2017).
Cooperative/Cognitive SWIPT: SWIPT frameworks integrated into cooperative or cognitive radio architectures substantially expand achievable rate regions, with secondary users able to harvest energy from the primary’s transmission, then relay the information in a power-aware superposition coding fashion (Krikidis et al., 2014).
Channel State Information Acquisition: SWIPT performance is highly sensitive to CSI at the transmitter. Analytic performance bounds for TS SWIPT under different CSI acquisition methods (none, TDD, FDD) show that TDD provides the best rate-outage-energy trade-off, especially as the number of transmit antennas increases (Liu et al., 2016).
Bandwidth and Modulation Choices: High-PAPR, multicarrier, and constant-envelope PSK/FSK modulations, adapted for nonlinear rectification, are consistently superior for maximizing energy harvesting while maintaining information throughput (Dhull et al., 27 Aug 2024, Kim et al., 2021).

7. Practical Challenges and Open Problems

Key implementation and research challenges in SWIPT include:

RF and optical safety constraints: Especially as transmit power or optical intensity rises for increased range.
Nonlinear rectifier modeling and waveform dependence: Accurate modeling of energy-harvesting circuits and joint waveform/receiver co-design.
CSI acquisition and resource overhead: The impact of training/feedback protocols on both energy and rate performance.
Multiuser/interference management: Joint scheduling and beamforming in dense deployments, including null-space and NOMA approaches.
Integration with mobile and moving elements: Robustness for UAV, robotic, or fluid-antenna SWIPT deployments (Zhang et al., 23 Oct 2025).
Security in SWIPT: Use of energy signals as artificial noise, secrecy constraints, and eavesdropper resilience (Ding et al., 2014).

A plausible implication is that realizing the full potential of SWIPT in practical large-scale deployments will require advances spanning device physics, cross-layer network optimization, robust and scalable algorithm design, and the integration of new physical-layer capabilities including optical, thermal, and spatial adaptation.