# Smart Beamforming for Direct LEO Satellite Access of Future IoT

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## Abstract

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## 1. Introduction

- A thorough analysis has been conducted to show that the proposed method is able to obtain a beamformer in the direction of the target user, without neither acquiring channel state information nor carrying out an exhaustive search through multiple angles;
- The theoretical throughput has been derived. The expressions reveal that the proposed RSBA can benefit from beamforming techniques to lower the collision probability when a large population of terminals is transmitting simultaneously;
- Practical implementation aspects have been tackled, such as the estimation of the covariance matrices and the determination of the number of users;
- We have shown by simulations that the proposed beamforming technique is able to distinguish and separate users that are located in different spots. Numerical results also reveal that performance gains can be achieved with respect to fixed beamforming networks.

## 2. Massive MIMO in LEO Satellites for Massive IoT

## 3. System Model

#### 3.1. Compensation Strategies

#### 3.2. Link Budget

## 4. Resource Sharing Beamforming Access

#### 4.1. Determination of the Number of Terminals

#### 4.2. Throughput Analysis

## 5. Numerical Results

#### 5.1. Number of Terminals

#### 5.2. Signal-to-Interference-Plus-Noise Ratio

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Appendix A

## References

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**Figure 5.**Beampattern displayed in the $uv$-plane. The beamformer points at a terminal that is located at $(\theta ,\varphi )=(24.91{}^{\circ},7.89{}^{\circ})$ or, equivalently $u=0.4172,v=0.0578$. There are nine interfering users and three of these select the same pattern as the user of interest.

**Figure 7.**MAPE versus ${N}_{\mathrm{U}}$ for different values of ${N}_{\mathrm{S}}$ and ${N}_{x},{N}_{y}$.

**Figure 8.**SINR versus ${N}_{\mathrm{U}}$ for different values of ${N}_{\mathrm{S}}$ and ${N}_{x},{N}_{y}$.

**Figure 9.**SINR versus ${N}_{\mathrm{U}}$ in fixed and digital beamforming schemes for ${N}_{x}={N}_{y}=24$.

**Figure 10.**User positions and 4.3 dB contour of the beams generated by the proposed beamforming with a planar array of $24\times 24$ antenna elements.

**Figure 11.**User positions and 4.3 dB contour of the beams generated by a fixed beamforming with a planar array of $24\times 24$ antenna elements.

Parameters | Value |
---|---|

Carrier frequency | ${f}_{c}=29$ GHz |

Minimum elevation angle | ${\psi}_{\mathrm{MIN}}=40$${}^{\circ}$ |

Field of view | ${\theta}_{\mathrm{MAX}}=44.44$${}^{\circ}$ |

Satellite altitude | $h=600$ Km |

Maximum distance | ${d}_{\mathrm{MAX}}=882$ km |

EIRPD for terminals | $EIRPD=-36.82$ dBW/Hz |

Maximum gain of antenna elements | ${G}_{R}=5$ dB |

Satellite antenna gain-to-noise temperature | $G/T=5$ dB/K |

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**MDPI and ACS Style**

Caus, M.; Perez-Neira, A.; Mendez, E. Smart Beamforming for Direct LEO Satellite Access of Future IoT. *Sensors* **2021**, *21*, 4877.
https://doi.org/10.3390/s21144877

**AMA Style**

Caus M, Perez-Neira A, Mendez E. Smart Beamforming for Direct LEO Satellite Access of Future IoT. *Sensors*. 2021; 21(14):4877.
https://doi.org/10.3390/s21144877

**Chicago/Turabian Style**

Caus, Marius, Ana Perez-Neira, and Eduard Mendez. 2021. "Smart Beamforming for Direct LEO Satellite Access of Future IoT" *Sensors* 21, no. 14: 4877.
https://doi.org/10.3390/s21144877