# Analysis of Packet Diversity in Buffer-Aided Relaying over Symmetric and Asymmetric Rayleigh Fading Channels

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## Abstract

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## 1. Introduction

#### Contributions

- The first scheme known as joint packet and relay selection (JPARS)-SNR is proposed for SNR-based relay selection. The relay selection is carried out first. The most suitable channel based on channel quality is picked for information transfer from all channels. After the relay selection, the packet selection is executed. If the chosen channel is of C2, the scheme picks the best matching from buffers of all relays. The best match is found according to the channel to packet matching notion. According to the condition of C2, the packet that affords the highest end-to-end SNR is picked from the buffer of the corresponding relay. In this design, the overall outage probability of the system is enhanced.
- JPARS-buffer state-based (BSB) being the second proposed scheme considers current buffer possession in relay selection. The relay with the freest or most occupied buffer space is selected for information processing. The packet selection step is the same as in JPARS-SNR scheme.
- The proposed JPARS-SNR scheme is simulated for both symmetric and asymmetric channel configurations and investigation for the outage probability, throughput and end-to-end packet delay are presented. The proposed JPARS-BSB scheme is simulated for the symmetric channel configuration using the relay thresholding technique.
- The results are analyzed with the existing schemes.

## 2. Relay and Packet Selection Schemes

#### 2.1. Network Model

#### 2.1.1. Channel Model

#### 2.1.2. Transmission Scheme

#### 2.2. Max-Link Scheme

#### 2.3. AF Max-Link Scheme

#### 2.4. AF Packet Selection Scheme

#### 2.5. Buffer Occupancy-Based AF Scheme

#### 2.6. Motivation for Proposed Work

## 3. Joint Packet and Relay Selection (JPARS) Schemes

#### 3.1. SNR-Based JPARS Scheme

#### 3.1.1. Step 1: Relay Selection

#### 3.1.2. Phase 2: Packet Selection

#### 3.2. Buffer State-Based Relay and Packet Selection

#### 3.2.1. Step 1: Relay Selection

#### 3.2.2. Step 2: Packet Selection Selection

#### 3.3. Buffer Access

## 4. Numerical Results

#### 4.1. Outage Probability: Symmetric Channel Conditions ${\overline{\gamma}}_{C1}={\overline{\gamma}}_{C2}=\overline{\gamma}$

#### 4.2. Outage Probability: Asymmetric Channel Conditions ${\overline{\gamma}}_{C1}=\alpha \phantom{\rule{3.33333pt}{0ex}}\overline{\gamma}$ and ${\overline{\gamma}}_{C2}=\beta \phantom{\rule{3.33333pt}{0ex}}\overline{\gamma}$

#### 4.3. Average Throughput

#### 4.4. Packet Delay

## 5. Conclusions and Future Works

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 4.**Outage probability of the proposed JPARS, AF Max-Link and AF-dual-hop schemes with the combinations of (K,L) as (1,2), (2,2) and (2,8).

**Figure 5.**Outage probability of the proposed JPARS schemes for $L=3$ with the increasing number of relays.

**Figure 6.**Outage probability of the proposed JPARS-SNR-based scheme for $K=2$ with the increasing buffer size.

**Figure 7.**Outage probability of the proposed JPARS-buffer state-based-based scheme for $K=2$ with the increasing buffer size.

**Figure 8.**Outage probability of the proposed JPARS-SNR scheme when C1 is prioritized for $L=4$, $K=2\phantom{\rule{3.33333pt}{0ex}}\mathrm{and}\phantom{\rule{3.33333pt}{0ex}}3$, $\alpha =2\phantom{\rule{3.33333pt}{0ex}}\mathrm{and}\phantom{\rule{3.33333pt}{0ex}}3$ and $\beta =1$.

**Figure 9.**Outage probability of the proposed JPARS-SNR scheme when C2 is prioritized for $L=4$, $K=2\phantom{\rule{3.33333pt}{0ex}}\mathrm{and}\phantom{\rule{3.33333pt}{0ex}}3$, $\alpha =1$ and $\beta =2\phantom{\rule{3.33333pt}{0ex}}\mathrm{and}\phantom{\rule{3.33333pt}{0ex}}3$.

**Figure 11.**Average throughput of the proposed schemes for $K=2$ and $L=3$ in asymmetric channel conditions.

**Table 1.**Comparison on relay selection and packet selection schemes in buffer-aided cooperative relaying.

Sr. | Scheme | Relaying Technique | Relay Selection | Packet Selection | Buffer Access |
---|---|---|---|---|---|

1 | Max-Link | DF | Yes | No | FIFO |

2 | AF Max-Link | AF | Yes | No | FIFO |

3 | AF-dual-hop | AF | No | Yes | Random |

4 | AF buffer state-based | AF | Yes | No | FIFO |

5 | JPARS-SNR | AF | Yes | Yes | Random |

6 | JPARS-BSB | AF | Yes | Yes | Random |

**Table 2.**Comparison on packet delay of JPARS-SNR, JPARS-BSB and AF Max-Link schemes for symmetric channel conditions $\overline{\gamma}=20\phantom{\rule{3.33333pt}{0ex}}$ dB.

AF Max-Link | JPARS-SNR | JPARS-BSB | |||||
---|---|---|---|---|---|---|---|

Max. | Min. | Max. | Min. | Max. | Min. | ||

$K=2$ | $L=2$ | 80 | 2 | 60 | 2 | 51 | 2 |

$L=8$ | 1094 | 2 | 862 | 2 | 478 | 2 | |

$K=3$ | $L=2$ | 132 | 2 | 107 | 2 | 52 | 2 |

$L=8$ | 1530 | 2 | 1107 | 2 | 489 | 2 |

**Table 3.**Comparison on maximum and minimum packet delay of JPARS-SNR and AF Max-Link schemes for $K=2$ and asymmetric channel conditions ${\overline{\gamma}}_{C1}=\alpha \overline{\gamma},\phantom{\rule{3.33333pt}{0ex}}{\overline{\gamma}}_{C2}=\beta \overline{\gamma}$.

AF Max-Link | JPARS-SNR | ||||
---|---|---|---|---|---|

Max. | Min. | Max. | Min. | ||

$\alpha =2,\phantom{\rule{3.33333pt}{0ex}}\beta =1$ | $L=2$ | 176 | 2 | 141 | 2 |

$L=8$ | 43,214 | 2 | 36,728 | 2 | |

$\alpha =1,\phantom{\rule{3.33333pt}{0ex}}\beta =2$ | $L=2$ | 42 | 2 | 39 | 2 |

$L=8$ | 120 | 2 | 103 | 2 |

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**MDPI and ACS Style**

Nasir, H.; Javaid, N.; Raza, W.; Shafiq, M. Analysis of Packet Diversity in Buffer-Aided Relaying over Symmetric and Asymmetric Rayleigh Fading Channels. *Symmetry* **2020**, *12*, 241.
https://doi.org/10.3390/sym12020241

**AMA Style**

Nasir H, Javaid N, Raza W, Shafiq M. Analysis of Packet Diversity in Buffer-Aided Relaying over Symmetric and Asymmetric Rayleigh Fading Channels. *Symmetry*. 2020; 12(2):241.
https://doi.org/10.3390/sym12020241

**Chicago/Turabian Style**

Nasir, Hina, Nadeem Javaid, Waseem Raza, and Muhammad Shafiq. 2020. "Analysis of Packet Diversity in Buffer-Aided Relaying over Symmetric and Asymmetric Rayleigh Fading Channels" *Symmetry* 12, no. 2: 241.
https://doi.org/10.3390/sym12020241