# Performance Enhancement for Full-Duplex Relaying with Time-Switching-Based SWIPT in Wireless Sensors Networks

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## Abstract

**:**

## 1. Introduction

- We propose a SIMO system model in which a two-antenna FD relay node can harvest energy from RF signals of a single-antenna source and then use the harvested energy to transfer information to a multi-antenna destination. Specifically, the destination can adopt SC or MRC to decode the received information.
- Both static TS factor (STSF)- and optimal dynamic TS factor (ODTSF)-based methods are investigated in our work. Especially in ODTSF methods, we derive the exact closed form of optimal dynamic TS factor for maximizing the total throughput obtained at the destination.
- To fully investigate the system performance, we propose four protocols, namely static time-switching factor with selection combining (STSF-SC), static time-switching factor with maximal ratio combing (STSF-MRC), optimal dynamic time-switching factor with selection combining (ODTSF-SC), and optimal dynamic time-switching factor with maximal ratio combing (ODTSF-MRC).
- Monte Carlo simulations are performed to corroborate the effectiveness of our proposed methods. Specifically, the results show that ODTSF-MRC always outperforms other schemes in terms of outage probability.

## 2. System Model

#### 2.1. Energy Harvesting and Information Transmission

**Remark**

**1.**

#### 2.1.1. Case 1: Selection Combining (SC) Is Adopted at the Destination

**Remark**

**2.**

#### 2.1.2. Case 2: Maximal Ratio Combining (MRC) Is Adopted at the Destination

## 3. Outage Probability (OP) Analysis

#### 3.1. Case 1: Static Time-Switching Factor (STSF)

#### 3.1.1. With SC

**Theorem**

**1.**

**Proof.**

#### 3.1.2. With MRC

**Theorem**

**2.**

**Proof.**

#### 3.2. Case 2: Optimal Dynamic Time-Switching Factor (ODTSF)

**Lemma**

**1.**

**Proof.**

#### 3.2.1. With SC

**Lemma**

**2.**

**Proof.**

**Theorem**

**3.**

**Proof.**

#### 3.2.2. With MRC

**Lemma**

**3.**

**Proof.**

**Theorem**

**4.**

**Proof.**

## 4. Simulation Results

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 2.**Schematic illustration of EH and IT processes with a time-switching relaying protocol at the relay.

**Figure 3.**Outage probability versus $\mathsf{\Phi}$ (in dB) with ${\gamma}_{\mathrm{th}}=1$ bps/Hz, $\eta =0.8$, M = 2.

**Figure 4.**Outage probability versus number of antennas at the destination with ${\gamma}_{\mathrm{th}}=1$ bps/Hz, $\eta =0.8$, $\mathsf{\Phi}=5$ dB.

**Figure 5.**Outage probability versus time-switching factor $\alpha $ with ${\gamma}_{\mathrm{th}}=1$ bps/Hz, $\eta =0.8$, $\mathsf{\Phi}=3$ dB, M = 2.

**Figure 6.**Outage probability versus ${\gamma}_{\mathrm{th}}$ with $\eta =0.8$, M = 2, and $\mathsf{\Phi}=5$ dB.

Symbol | Parameter Name | Fixed Value | Varying Range |
---|---|---|---|

${\gamma}_{\mathrm{th}}$ | SNR threshold of the system | 1 | 0.5 to 8 |

$\eta $ | Energy harvesting efficiency | 0.8 | none |

$\alpha $ | Time-switching factor | 0.05–0.95 | 0.05 to 0.95 |

${d}_{\mathrm{SR}}$ | Distance between source S and relay R | 1 | none |

${d}_{\mathrm{RD}}$ | Distance between relay R and destination D | 0.5 | none |

${\lambda}_{\mathrm{SR}}$ | Rate parameter of $|{h}_{\mathrm{SR}}{|}^{2}$ | 1 | none |

${\lambda}_{\mathrm{RD}}$ | Rate parameter of $|{h}_{\mathrm{R}}{|}^{2}$ | 0.5 | none |

${\lambda}_{\mathrm{RR}}$ | Rate parameter of $|{h}_{\mathrm{RR}}{|}^{2}$ | 5 | none |

$\mathsf{\Psi}$ | Transmit-power-to-noise-ratio | 5 dB | −5 to 15 (dB) |

M | No. of antennas at the destination | 2; 3 | 1 to 10 |

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**MDPI and ACS Style**

Tin, P.T.; Nguyen, T.N.; Tran, D.-H.; Voznak, M.; Phan, V.-D.; Chatzinotas, S.
Performance Enhancement for Full-Duplex Relaying with Time-Switching-Based SWIPT in Wireless Sensors Networks. *Sensors* **2021**, *21*, 3847.
https://doi.org/10.3390/s21113847

**AMA Style**

Tin PT, Nguyen TN, Tran D-H, Voznak M, Phan V-D, Chatzinotas S.
Performance Enhancement for Full-Duplex Relaying with Time-Switching-Based SWIPT in Wireless Sensors Networks. *Sensors*. 2021; 21(11):3847.
https://doi.org/10.3390/s21113847

**Chicago/Turabian Style**

Tin, Phu Tran, Tan N. Nguyen, Dinh-Hieu Tran, Miroslav Voznak, Van-Duc Phan, and Symeon Chatzinotas.
2021. "Performance Enhancement for Full-Duplex Relaying with Time-Switching-Based SWIPT in Wireless Sensors Networks" *Sensors* 21, no. 11: 3847.
https://doi.org/10.3390/s21113847