# Heterogeneous Network Switching Strategy Based on Communication Blind Area Dwell Time

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## Abstract

**:**

## 1. Introduction

## 2. Methodology

#### 2.1. Basic Theory of VLC

_{S}represents the transmit power, and P

_{R}represents the received power under the circumstance of LOS.

_{R}

_{(signal)}is the signal received power, B is the noise bandwidth, P

_{R}

_{(ISI)}is the inter-code interference power, I

_{bg}is the dark current, and I

_{2}is the noise bandwidth factor. The thermal noise can be expressed as

_{k}is the absolute temperature, C

_{pd}is the fixed capacitance per unit area of the photodetector, G is the open-loop voltage gain, $\mathsf{\Gamma}$ is the channel noise coefficient, g

_{m}is the transconductance coefficient, and I

_{2}, I

_{3}are both noise bandwidth coefficients. The signal-to-noise ratio (SNR) can be expressed as [14]:

#### 2.2. The Technology of ACO-OFDM

## 3. VLC Heterogeneous Networking Technology Research

#### 3.1. Visible Light Source Layout

#### 3.2. ACO-OFDM Channel Processing

#### 3.3. CBDHVHO Scheme

_{threshold}refers to the threshold time, which follows a random distribution in the interval [T

_{res}, T

_{max}]. T

_{res}is the time limit of the response time for the user’s thought stream to remain uninterrupted [18], and T

_{max}is the maximum waiting time for the visible channel interruption. When the T

_{S}is greater than T

_{threshold}, the user receiving equipment in the communication blind area will be affected by the channel interruption. In order to maintain normal communication, the vertical handover is accessed at this time, and in order to prevent the switching handover cost from being too high, the execution of the vertical handover will be maintained until the end of the mobile process. When the T

_{S}is less than the T

_{threshold}, the user’s receiving device is basically not affected by the channel response interruption. The implementation of horizontal handover can ensure high-quality user communication.

## 4. Simulation Results

#### 4.1. Communication Stability Performance Evaluation

_{HO}is the handover failure probability of the specified scheme, P(r) is the utilization of the RF communication uplink server after r iterations, and B is the maximum queue length of the RF communication uplink.

#### 4.1.1. Performance Analysis for Handover Failure Probability

_{t=0.5}scheme and D-VHO

_{t=1}scheme have a handover failure probability of 0.016 and 0.013, respectively, which is because the scheme does not perform handover during partial dwell time, and the CBDHVHO scheme has a handover failure probability of 0.009 due to its lower handover cost and seamless connection. The handover failure probability is 0.009 because the handover failure probability is closely related to the number of handovers; more handovers will result in more delay time and more dwell packets, so the handover failure probability will increase.

#### 4.1.2. Performance Analysis for BER

#### 4.2. Heterogeneous Networking System Power Performance Evaluation

_{HO}presents the average number of handovers and N

_{r}represents the number of executions. N

_{HO}(r) represents the number of r-th execution.

#### Analysis of the Average Number of Handovers for Different Programs

_{t=0.5}scheme sets the residence time under a VLC network to 0.5 s, which means that when the residence time of a user receiving equipment under a VLC network is lower than 0.5 s, no handover is performed, so the average number of handovers is lower, 1.424. Similarly, the average number of handovers for the D-VHO

_{t=1}scheme is 1.04. The average number of handovers for the CBDHHO scheme is 1.006, but considering that the channel response interruption time in the communication blind area is very short, the CBDVHO scheme is used to assist in order to maintain continuous and stable communication with the user receiving equipment, so the total number of handovers will increase a little compared to the D-VHO

_{t=1}scheme.

#### 4.3. Communication Quality Performance Evaluation

_{th}is the average throughput, T

_{i}(r) represents the network dwell time when executing the r-th time, and T

_{d}(r) represents the network handover delay time when executing the r-th time.

#### 4.3.1. Analysis of the Average Network Throughput of Different Solutions

#### 4.3.2. Analysis of the Impact of Different Velocities on the Average Network Throughput

_{t=0.5}scheme decreases from 162.8908 Mbps to 137.7859 Mbps; the D-VHO

_{t=1}scheme decreases from 167.0896 Mbps to 127.5167 Mbps; and the average network throughput of the CBDHVHO scheme increases from 172.4695 Mbps to 231.5928 Mbps. The above data show that the scheme has good applicability for mobile velocity.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Nomenclature

OFDM | Orthogonal frequency division multiplexing |

ACO-OFDM | Asymmetrically clipped optical OFDM |

BER | Bit error rate |

I-VHO | Instant vertical handover |

D-VHO | Dwell vertical handover |

VLC | Visible light communication |

RF | Radio frequency |

HHO | Horizontal handover |

VHO | Vertical handover |

CAD-VHO | Channel adaptive residence vertical handover |

HA-VHO | Hybrid application vertical handover |

RSS | Received signal strength |

FFT | Fast Fourier transformation |

LOS | Line of sight |

NLOS | Non-line of sight |

LED | Light-emitting diode |

DC | Direct Current |

SNR | Signal-to-noise ratio |

CP | Cyclic prefix |

QAM | Quadrature amplitude modulation |

IFFT | Inverse fast Fourier transformation |

AWGN | Additive white Gaussian noise |

DCO-OFDM | DC-biased Optical OFDM |

## References

- Lee, K.; Park, H.; Barry, J.R. Indoor channel characteristics for visible light communications. IEEE Commun. Lett.
**2011**, 15, 217–219. [Google Scholar] [CrossRef] - Yeh, C.-H.; Liu, Y.-L.; Chow, C.-W. Real-time white-light phosphor-LED visible light communication (VLC) with compact size. Opt. Exp.
**2013**, 21, 26192–26197. [Google Scholar] [CrossRef] [PubMed] - Vegni, A.M.; Little, T.D.C. Handover in VLC systems with cooperating mobile devices. In Proceedings of the International Conference on Computing, Networking and Communications (ICNC), Maui, HI, USA, 30 January–2 February 2012; pp. 126–130. [Google Scholar]
- Wang, F.; Yang, F.; Song, J.; Han, Z. Access Frameworks and Application Scenarios for Hybrid VLC and RF Systems: State of the Art, Challenges, and Trends. IEEE Commun. Mag.
**2022**, 60, 55–61. [Google Scholar] [CrossRef] - Wang, F.; Wang, Z.; Qian, C.; Dai, L.; Yang, Z. Efficient vertical handover scheme for heterogeneous VLC-RF systems. IEEE/OSA J. Opt. Commun. Netw.
**2015**, 7, 1172–1180. [Google Scholar] [CrossRef] - Hou, J.D.; O’Brien, D.C. Vertical handover decision-making algorithm using fuzzy logic for the integrated radio-and-OW system. IEEE Trans. Wirel. Commun.
**2006**, 5, 176–185. [Google Scholar] [CrossRef] - Bao, X.; Okine, A.A.; Adjardjah, W.; Zhang, W.; Dai, J. Channel adaptive dwell timing for hando-ver decision in VLC-WiFi heterogeneous networks. EURASIP J. Wirel. Commun. Netw.
**2018**, 2018, 244. [Google Scholar] [CrossRef] - Okine, A.A.; Bao, X.; Mongoungou, J.; Adjardjah, W.; Zhang, W. A Hybrid Application-Aware VHO Scheme for Coexisting VLC and WLAN Indoor Networks. J. Netw. Syst. Manag.
**2022**, 30, 52. [Google Scholar] [CrossRef] - Wu, Y.; Zhang, S. Research on indoor VLC-WiFi heterogeneous wireless access network. Semicond. Optoelectron.
**2017**, 38, 853–856. [Google Scholar] - Wang, S.Q.; Tang, Y.F.; Du, J.Y. Research on handover strategy of heterogeneous networks based on user service quality. Int. J. Commun. Syst.
**2022**, 35, e5048. [Google Scholar] [CrossRef] - Shi, G.; Li, Y.; Cheng, W. Accuracy Analysis of Indoor Visible Light Communication Localization System Based on ReceivedSignal Strength in Non-Line-of-Sight Environments by Using Least Squares Method. Opt. Eng.
**2019**, 58, 056102. [Google Scholar] [CrossRef] - Ghassemblooy, Z.; Popoola, W.; Rajbhandari, S. Optical Wireless Communications: System and Channel Modelling with Matlab
^{®}; CRC Press: Boca Raton, FL, USA, 2019. [Google Scholar] - Chaudhary, N.; Alves, L.N.; Ghassemblooy, Z. Feasibility Study of Reverse Trilateration Strategy with a Single Tx for VLP. In Proceedings of the 2019 2nd West Asian Colloquium on Optical Wireless Communications (WACOWC), Tehran, Iran, 27–28 April 2019; pp. 121–126. [Google Scholar]
- Wang, Y.; Wu, X.; Haas, H. Fuzzy logic based dynamic handover scheme for indoor li-fi and RF hybrid network. In Proceedings of the 2016 IEEE International Conference on Communications, ICC, Kuala Lumpur, Malaysia, 22–27 May 2016; pp. 1–6. [Google Scholar]
- Ma, S.; Yang, R.; Deng, X.; Ling, X.; Zhang, X.; Zhou, F.; Li, S.; Ng, D.W.K. Spectral and Energy Efficiency of ACO-OFDM in Visible Light Communication Systems. IEEE Trans. Wirel. Commun.
**2022**, 21, 2147–2161. [Google Scholar] [CrossRef] - Liu, H.L.; Liu, Z.Y. Coverage uniformity with improved genetic simulated annealing algorithm for indoor visible light com-munications. Opt. Commun.
**2017**, 48, 76–81. [Google Scholar] [CrossRef] - Tekin, M.; Savaşcihabeş, A.; Ertuğ, Ö. M-CSK-Flip OFDM for Visible Light Communication Systems. In Proceedings of the 2021 44th International Conference on Telecommunications and Signal Processing (TSP), Brno, Czech Republic, 26–28 July 2021; pp. 106–109. [Google Scholar] [CrossRef]
- Nah, F.F.H. A study on tolerable waiting time: How long are web users willing to wait? Behav. Inf. Technol.
**2004**, 23, 153–163. [Google Scholar] [CrossRef] - Zeshan, A.; Baykas, T. Location Aware Vertical Handover in a VLC/WLAN Hybrid Network. IEEE Access
**2021**, 9, 129810–129819. [Google Scholar] [CrossRef] - Jiang, Y.; Sun, D.; Zhu, X.; Zhou, T.; Wang, T.; Sun, S. Robust Frequency-Domain Timing Offset Estimation for DCO-OFDM Systems. IEEE Commun. Lett.
**2022**, 26, 1603–1607. [Google Scholar] [CrossRef] - Zhang, J.; Li, Y.; Xiao, W.; Zhang, Z. Online Spatiotemporal Modeling for Robust and Lightweight Device-Free Localization in Nonstationary Environments. IEEE Trans. Ind. Inform.
**2023**, 19, 8528–8538. [Google Scholar] [CrossRef] - Zhang, J.; Li, Y.; Xiong, H.; Dou, D.; Miao, C.; Zhang, D. HandGest: Hierarchical Sensing for Robust-in-the-Air Handwriting Recognition with Commodity WiFi Devices. IEEE Internet Things J.
**2022**, 9, 19529–19544. [Google Scholar] [CrossRef] - Nguyen, B.C.; Tran, X.N.; Hoang, T.M.; Dung, L.T. Performance Analysis of Full-Duplex Vehicle-to-Vehicle Relay System over Double-Rayleigh Fading Channels. Mob. Netw. Appl.
**2020**, 25, 363–372. [Google Scholar] [CrossRef] - Lei, T.; Ni, S.; Cheng, N.; Chen, S.; Song, X. SCMA Codebook for Uplink Rician Fading Channels. IEEE Commun. Lett.
**2023**, 27, 527–531. [Google Scholar] [CrossRef]

**Figure 7.**Comparison of the handover failure probabilities of the proposed I-VHO, D-VHO, and CBDHVHO schemes.

**Figure 9.**Comparison of the average number of handovers for the proposed I-VHO, D-VHO, CBDVHO, and CBDHHO schemes.

**Figure 10.**Comparison of the average network throughput of the proposed I-VHO, D-VHO, and CBDHVHO schemes.

**Figure 11.**Comparison of the impact of different velocities of the proposed I-VHO, D-VHO, and CBDHVHO schemes on the average network throughput.

Parameter | Value |
---|---|

Room size | 6 m × 6 m × 3 m |

Velocity | 0.3~0.7 m/s |

Movement time duration | 1–30 s |

Throughput for VLC | 400 Mbps |

Throughput for Wi-Fi | 100 Mbps |

Number of VLC APs | 9 |

Radius of APs | $1\mathrm{m},\sqrt{2}$ m |

Number of iterations | 1000 |

Number of RF APs | 1 |

Handover delay time | 0.1~1 s |

Time frame for response time | 1 s |

Maximum waiting time | 2 s |

BER Scope | ${10}^{-7}$~0.025 |

Communication blind area dwell time | 0~7 s |

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**MDPI and ACS Style**

Zhang, C.; Tang, Y.; Wang, X.; Zhang, Y.; Li, X.
Heterogeneous Network Switching Strategy Based on Communication Blind Area Dwell Time. *Sensors* **2023**, *23*, 6166.
https://doi.org/10.3390/s23136166

**AMA Style**

Zhang C, Tang Y, Wang X, Zhang Y, Li X.
Heterogeneous Network Switching Strategy Based on Communication Blind Area Dwell Time. *Sensors*. 2023; 23(13):6166.
https://doi.org/10.3390/s23136166

**Chicago/Turabian Style**

Zhang, Cheng, Yanfeng Tang, Xiuzhuo Wang, Yan Zhang, and Xiuyang Li.
2023. "Heterogeneous Network Switching Strategy Based on Communication Blind Area Dwell Time" *Sensors* 23, no. 13: 6166.
https://doi.org/10.3390/s23136166