تحسين أداء أنظمة اتصالات الضوء المرئي
Performance Enhancement of Visible Light Communication Systems
- الباحث
- سمير م. حميد
- المشرف
- سنان ماجد عبد الستار - أثير علاء صبري
- الجامعة
- الجامعة التكنولوجية
- الكلية / القسم
- قسم الهندسة الكهربائية / هندسة الالكترونيك والاتصالات
- الشهادة
- دكتوراه
- السنة
- 2022
- لغة الرسالة
- انكليزي
- الكلمات المفتاحية
- Visible light communication;LED;Performance enhancement;Optical wireless
Abstract
Optical wireless communication (OWC) encourages higher-speed communication solutions. Visible light communication (VLC) has become a promising technology in the OWC. Researchers have extensively utilized optical orthogonal frequency division multiplexing (O-OFDM) in VLC to get high data rate transmission for free spectrum bandwidth. The main challenges that impair the performance of VLC O- OFDM systems are the high peak-to-average power ratio (PAPR), the non-linearity characteristic of the light-emitting diode (LED), and clipping noise. Various VLC O-OFDM systems are developed, investigated, analyzed, and evaluated in this thesis using Matlab 2019 software. DC-biased OFDM (DCO-OFDM) has inefficient power requirements, whereas asymmetrically clipped OFDM (ACO- OFDM) has low spectral efficiency. Asymmetrically clipped DC-biased (ADO-OFDM) is a modern performance enhancement technology. The main drawback of ADO-OFDM is clipping noise, primarily affecting even subcarriers. This thesis proposes a new ADO-OFDM design for VLC that reduces the computational complexity of traditional ADO-OFDM and has better spectral efficiency than that of DCO-OFDM and ACO-OFDM. Many performance enhancement approaches are presented and simulated for VLC systems, including improving bit error rate (BER) and PAPR reduction. The results show that the BER enhancement model of the convolutional encoder/ Viterbi decoder with the examined O-OFDM mitigates the LED non-linearity and it increases the signal-to-noise ratio (SNR) gain by 10 dB. The BER is further improved using the multiple input multiple output (MIMO) approach that collaborates with ADO-OFDM. It attained BER = 10-4 for an SNR of 15 dB. Different PAPR reduction techniques are illustrated. The results outperform the combination of the enhancement model with the -law companding approach by about 75% PAPR reduction. Moreover, another new companding is proposed to be used with ADO-OFDM to achieve PAPR reduction and BER boosting. It can reduce PAPR to 1.8 dB with a BER of 10-5 at SNR = 26 dB. Finally, the thesis concludes that performance enhancement is achieved by adopting MIMO-ADO-OFDM. In addition, spatial multiplexing has maximized spectral efficiency, which reaches a spectral efficiency of 23.952 bit/s/Hz. Multi-user MIMO can be performed using ADO-OFDM by decomposing received signals and eliminating inter- user interference.
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