Performance Improvement for Wireless Sensors Networks by Adopting Hybrid Subcarrier Intensity Modulation Over Exponentiated Weibull Turbulence Channels

Yi Wu,Yuan Hao,Zhongchao Wei,Lin Zhao,Ting Jiang,Hongzhan Liu,Dongmei Deng

doi:10.1109/access.2020.3003329

Abstract

We conduct a research on free space optical (FSO) communication system that is applied for transmission in wireless sensor networks (WSN), which is based on the hybrid pulse position modulation-binary phase shift keying-subcarrier intensity modulation (PPM-BPSK-SIM) undergoes novel Exponentiated Weibull fading channels. When battery-charged sensor transmission nodes with limited energy is transmitted, it is vital to study the performance of the transmission link. We have derived the exact joint probability function of the transmission link when the atmospheric turbulence and pointing errors are considering. On the basis of them, the unconditional average bit error rate (BER) for hybrid PPM-BPSK-SIM is derived, then the closed expression of the outage probability and the average channel capacity are also derived. Research results indicates that increasing the receiver aperture by aperture averaging effect can distinctly improve the performance of the link. Additionally, for any circumstances of atmospheric turbulence and pointing errors, by combining the utilization of hybrid PPM-BPSK-SIM modulation and symbol with average length greater than eight, the average BER performance can be conspicuously enhanced. The outage probability and average channel capacity of the FSO link are jointly affected by atmospheric turbulence and pointing error, and optimization strategies in different scenarios are given by our research.

Highlights

Wireless sensor networks (WSN) have raised extensive research in recent years due to their advantages of small size and low cost
We use the novel Exponentiated Weibull (EW) distribution model to quantitatively describe atmospheric turbulence, the interference caused by pointing errors is considered, and the receiver employs intensity modulation/direct detection (IM/DD) to obtain the performance of the free space optical (FSO) transmission link
In summary, we have studied the performance of the FSO link in the wireless sensor networks when the hybrid L-ary pulse position modulation (LPPM)-BPSK-SIM is adopted

Summary

INTRODUCTION

Wireless sensor networks (WSN) have raised extensive research in recent years due to their advantages of small size and low cost. Y. Wu et al.: Performance Improvement for Wireless Sensors Networks by Adopting Hybrid Subcarrier Intensity Modulation average BER of FSO communication links under interference in WSN in order to improve the operating efficiency of the entire networks. BPSK is widely used in FSO links as a low BER binary modulation, but little research has been done on the improvement of high-order modulation and hybrid subcarrier intensity modulation for communication systems, let alone that the receiver aperture is considered. We derived the unconditional BER of various PPM-BPSK-SIM when intensity modulation/direct detection (IM/DD) is employed at the receiver [34], closed solution of the outage probability and average channel capacity are obtained, and simulation analysis shows that the adoption of hybrid subcarrier intensity modulation undoubtedly improve the FSO link transmission in wireless sensor networks [35].

SYSTEM AND CHANNEL MODELS

AVERAGE BIT ERROR RATE

NUMERICAL RESULTS AND DISCUSSION

CONCLUSION