# Enhanced Integrated Satellite-Terrestrial NOMA with Cooperative Device-to-Device Communication

^{*}

## Abstract

**:**

## 1. Introduction

- A novel user pairing scheme is proposed, considering the satellite channels and the terrestrial D2D channels. In order to study this problem, graph theory is invoked—modeling it as a maximum weighted perfect matching problem.
- Power allocation for NOMA in each transmission period considers the achieved rates through orthogonal multiple access (OMA). In this way, the proposed power allocation guarantees that user pairing will lead to a higher rate for each pair member and an overall rate increase for the network.
- The impact of various system parameters inherent to satellite-based access and D2D networks have been evaluated, i.e., the elevation angle and the bandwidth allocation, respectively. As a result, guidelines are given in order to achieve improved satellite-terrestrial cooperation and spectral efficiency, compared to standalone NOMA and OMA deployments.

## 2. System Model

#### 2.1. Topology

#### 2.2. Channel Model

#### 2.3. Transmission Parameters and Achievable Rates

## 3. Satellite-Aided NOMA with Cooperative D2D Communication

#### 3.1. SANOCO-D2D Operation

**Remark**

**1.**

**Remark**

**2.**

Algorithm 1: Graph creation. |

Algorithm 2: SANOCO-D2D. |

#### 3.2. Toy Network

## 4. Performance Evaluation

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## Acknowledgments

## Abbreviations

5G | Fifth Generation |

AWGN | Additive White Gaussian Noise |

BS | Base Station |

C-NOMA | Cooperative NOMA |

CSI | Channel State Information |

D2D | Device-to-Device |

FSL | Free Space Pathloss |

GEO | Geosynchronous Earth Orbit |

IoT | Internet of Things |

LEO | Low Earth Orbit |

LMS | Land Mobile Satellite |

LoS | Line of Sight |

MC | Medium Channel |

MEO | Medium Earth Orbit |

MP | Multipath Component |

NOMA | Non-Orthogonal Multiple Access |

OMA | Orthogonal Multiple Access |

QoS | Quality-of-Service |

SANOCO-D2D | Satellite-Aided NOMA with Cooperative D2D Communication |

SC | Strong Channel |

SIC | Successive Interference Cancellation |

SNR | Signal-to-Noise Ratio |

TDMA | Time-Division Multiple Access |

UE | User Equipment |

WC | Weak Channel |

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**Figure 2.**An illustrative example of the graph setup that is used by the proposed technique in order to find the optimal user pairing policy ${\mathbf{u}}_{\mathbf{i},\mathbf{j}}^{*}$ and the maximum sum rate ${R}_{\mathrm{max}}$ for $N=4$ UEs.

**Figure 3.**Optimal user pairing policy ${\mathbf{u}}_{\mathbf{i},\mathbf{j}}^{*}$ that gives the maximum sum rate ${R}_{\mathrm{max}}$ for $N=4$ UEs and the studied toy network.

**Figure 4.**Spectral efficiency for scenario 1, $E={10}^{\circ}$ and different terrestrial D2D bandwidth values.

**Figure 6.**Spectral efficiency for scenario 1, ${B}_{d}=0.4$ MHz and different elevation angle values.

**Figure 8.**Spectral efficiency for scenario 2, $E={10}^{\circ}$ and different terrestrial D2D bandwidth values.

**Figure 10.**Spectral efficiency efficiency for scenario 2, ${B}_{d}=0.4$ MHz and different elevation angle values.

**Table 1.**An example of the different possible pairs and the corresponding achievable system sum rate for the possible formations with $N=4$ UEs.

Possible Formed Pairs | System Sum Rate |
---|---|

${P}_{1,2}=\{{\mathrm{UE}}_{1},{\mathrm{UE}}_{2}\}$ and ${P}_{3,4}=\{{\mathrm{UE}}_{3},{\mathrm{UE}}_{4}\}$ | ${w}_{1,2}+{w}_{3,4}=7$ |

${P}_{1,3}=\{{\mathrm{UE}}_{1},{\mathrm{UE}}_{3}\}$ and ${P}_{2,4}=\{{\mathrm{UE}}_{2},{\mathrm{UE}}_{4}\}$ | ${w}_{1,3}+{w}_{2,4}=12$ |

${P}_{1,4}=\{{\mathrm{UE}}_{1},{\mathrm{UE}}_{4}\}$ and ${P}_{2,3}=\{{\mathrm{UE}}_{2},{\mathrm{UE}}_{3}\}$ | ${w}_{1,4}+{w}_{2,3}=3$ |

**Table 2.**Loo’s model’s channel parameters and average range D between the LEO satellite and UE for different elevation angles and channel states.

${\mathit{E}}^{\circ}$ | Line-of-Sight | Intermediate Shadow | Deep Shadow | D (km) | ||||||
---|---|---|---|---|---|---|---|---|---|---|

M (dB) | $\Sigma $ (dB) | MP (dB) | M (dB) | $\Sigma $ (dB) | MP (dB) | M (dB) | $\Sigma $ (dB) | MP (dB) | ||

10${}^{\circ}$ | −0.7 | 1.9 | −38.3 | −18.4 | 8.6 | −14.7 | −24.4 | 9.4 | −23.9 | 2300 |

20${}^{\circ}$ | 0.7 | 2.1 | −25.5 | −10.0 | 4.9 | −23.3 | −25.3 | 7.0 | −26.5 | 1700 |

40${}^{\circ}$ | −0.2 | 1.0 | −32.9 | −8.6 | 3.8 | −16.1 | −15.1 | 2.6 | −16 | 1000 |

60${}^{\circ}$ | 0.1 | 1.9 | −27.2 | −6.9 | 2.2 | −18.6 | −13.1 | 4.2 | −19.7 | 900 |

Simulated frames | 100,000 |

Number of UEs N | 32 |

Region of interest circle radius R | 500 m |

Satellite downlink frequency ${f}_{s}$ | 1.625 GHz |

D2D operating frequency ${f}_{d}$ | 2 GHz |

Satellite Tx antenna gain ${G}_{t}^{s}$ | 24 dBi |

Satellite transmit SNR | 0–30 dB |

UE satellite Rx antenna gain ${G}_{r}^{s}$ | 2.7 dBi |

System receiver noise temperature ${T}_{s}$ | 25.7 dBK |

UE transmit SNR and ${P}_{d}$ | 23 dBm and 0.1995 Watt |

System receiver noise temperature ${T}_{d}$ | 24.6 dBK |

D2D Tx/Rx antenna gain ${G}_{g}^{d}$ with $g=\{t,r\}$ | 0 dBi |

D2D pathloss model | $127+30{log}_{10}\left(d\right)$ |

D2D log-normal shadowing | 8 dB |

Satellite Bandwidth ${B}_{s}$ | 5 MHz |

UE speed | 3 km/hr |

Maximum Doppler Shift | 40 kHz |

Terrestrial Environment | Urban |

**Table 4.**Comparative table regarding the key characteristics of the SANOCO-D2D and the scheme of [6].

SANOCO-D2D | NOMA Scheme [6] | |
---|---|---|

Complexity | Medium | Low |

D2D Cooperation | Yes | No |

Relaying Mode | Half Duplex | N/A |

CSI Overhead | Medium | Low |

Power Allocation | Optimal | Optimal |

Dynamic D2D Channel Bandwidth | Yes | N/A |

Reliability | High | Medium |

Spectral Efficiency | High | Medium |

Sum Rate | High | Medium |

Fairness | High | Low |

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**MDPI and ACS Style**

Karavolos, M.; Nomikos, N.; Vouyioukas, D.
Enhanced Integrated Satellite-Terrestrial NOMA with Cooperative Device-to-Device Communication. *Telecom* **2020**, *1*, 126-149.
https://doi.org/10.3390/telecom1020010

**AMA Style**

Karavolos M, Nomikos N, Vouyioukas D.
Enhanced Integrated Satellite-Terrestrial NOMA with Cooperative Device-to-Device Communication. *Telecom*. 2020; 1(2):126-149.
https://doi.org/10.3390/telecom1020010

**Chicago/Turabian Style**

Karavolos, Michail, Nikolaos Nomikos, and Demosthenes Vouyioukas.
2020. "Enhanced Integrated Satellite-Terrestrial NOMA with Cooperative Device-to-Device Communication" *Telecom* 1, no. 2: 126-149.
https://doi.org/10.3390/telecom1020010