Görünür Işık Haberleşmesi için Fourier ve Trigonometrik Dönüşüm Tabanlı Çok Taşıyıcılı Modülasyonların Karşılaştırılması

Abstract

Kablosuz verideki artış nedeniyle yakın gelecekte radyo frekans spektrumunun yetersiz kalması ön görülmektedir. Görünür Işık Haberleşmesi (VLC) yüksek hız vaat eden alternatif bir çözümdür. VLC sistemleri, diğer kablosuz haberleşme sistemlerine benzer şekilde, Çoklu Taşıyıcılı Modülasyon (MCM) tercih ederler, ancak optik iletişim için iletimden önce sinyaller gerçek ve tek kutuplu olacak şekilde dönüştürülürler. Bu makalede, Ayrık Fourier Dönüşümü (DFT) ve Ayrık Trigonometrik Dönüşümü (DTT) kullanan iki optik MCM grubu Bit Hata Oranı (BER), spektral verimlilik ve karmaşıklık açısından sorgulanmaktadır. DFT tabanlı teknikler, gerçek çıkış sinyali elde etmek için karmaşık eşlemeli sinyaller ve onların Hermit simetrilerini kullanırlar, DTT tabanlı tekniklerde ise giriş sinyali gerçek eşlenmiş ise çıkış zaten gerçek olacaktır. DFT tabanlı tekniklerin kullanılan eşleme nedeniyle daha düşük BER'lere sahip oldukları görülmektedir. DTT tabanlı teknikler spektral verimliliği arttırır ancak bu teknikler daha yüksek hata oranlarına sahip gerçek eşlemelerle sınırlıdırlar. Her iki dönüşüm için de gerçek sinyaller, bir öngerilim eklenerek (DCO-MCM), asimetrik olarak kırpılarak (ACO-MCM) veya pozitif ve negatif değerleri ayrı ayrı göndererek (UnO-MCM) tek kutuplu hale getirilir. Dc bileşen eklemek (DCO-MCM) BER'leri arttırırken, ACO-MCM ve UnO-MCM in daha düşük BER'lerle yakın performanslara sahip oldukları gösterilmiştir.

Keywords

• Bit hata oranı
• ayrık fourier dönüşüm
• ayrık trigonometrik dönüşüm
• çok taşıyıcılı modülasyon
• görünür ışık haberleşmesi.

Comparison of Fourier and Trigonometric Transform based Multicarrier Modulations for Visible Light Communication

Abstract

It is predicted that the radio frequency spectrum will be insufficient in the near future due to the increase in wireless data. Visible Light Communication (VLC) is an alternative solution, which promises high speeds. Similar to other wireless communication systems, VLC systems prefer Multicarrier Modulation (MCM), but the signals are converted to be real and unipolar before transmission for optical communication. In this paper, two optical MCM groups that utilize Discrete Fourier Transform (DFT) and Discrete Trigonometric Transform (DTT) are questioned with respect to Bit Error Rate (BER), spectral efficiency and complexity. DFT based techniques use complex mapped signals together with their Hermitian symmetries to obtain real output signals, while DTT based techniques already output real signals when the input signal is real mapped. It is seen that DFT based techniques have lower BERs because of used mapping. DTT based techniques improve spectral efficiency, but they are limited to real mappings with higher error rates. For both transformations, the real signals are made unipolar by adding a bias (DCO-MCM), by asymmetrically clipping (ACO-MCM) or by sending positive and negative values separately (UnO-MCM). It is shown that, adding a dc bias (DCO-MCM) increases BERs, where ACO-MCM and UnO-MCM have close performances with lower BERs.

Keywords

• Bit Error Rate
• Discrete Fourier Transform
• Discrete Trigonometric Transform
• Multicarrier Modulation
• Visible Light Communication.

References

1. Çürük SM. Alignment of transmitters in indoor Visible Light Communication for flat channel characteristics. ETRI J 2022; 44(1): 125–134.
2. Chen C, Zhong WD, Wu D. Non-Hermitian Symmetry Orthogonal Frequency Division Multiplexing for multiple-input multiple-output Visible Light Communications. J Opt Commun Netw 2017; 9(2): 36-44.
3. Zhang X, Babar Z, Petropoulos P, Haas H, Hanzo L. The Evolution of optical OFDM. IEEE Commun Surv Tut 2021; 23(3): 1430-1457.
4. Xia L, Wang X, Sun Z, Cheng Z, Jin J, Yuan Y, Liu G, Jiang T, Huang Y. Signal clipping at transmitter and receiver of O-OFDM for VLC under optical power constraint. China Commun 2022; 19(6): 154-168.
5. Farid SM, Saleh MZ, Elbadawy HM, Elramly SH. Novel unipolar optical modulation techniques for enhancing Visible Light Communication systems performance. IEEE Access 2022; 10: 67925-67939.
6. Xu XY, Zhang Q, Yue DW. Orthogonal Frequency Division Multiplexing with index modulation based on discrete Hartley transform in Visible Light Communications. IEEE Photonics J 2022; 14(3): 1-10.
7. Ma S, Yang R, Deng X. Spectral and energy efficiency of ACO-OFDM in Visible Light Communication systems. IEEE Trans Wirel Commun 2022; 21(4): 2147-2161.
8. Niu S, Wang P, Chi S, Liu Z, Pang W, Guo L. Enhanced optical OFDM/OQAM for Visible Light Communication systems. IEEE Wirel Commun Lett 2021; 10(3): 614-618.

9. Hong H, Li Z. Hybrid adaptive bias OFDM-based IM/DD Visible Light Communication system. Photonics 2021; 8(7): 257-267.
10. Armstrong J, Lowery AJ. Power efficient optical OFDM. Electron Lett 2006; 42(6): 370-372.
11. Vappangi S, Mani VV. Performance analysis of DST-based Intensity Modulated / Direct Detection (IM/DD) systems for VLC. IEEE Sens J 2018; 19(4): 1320-1337.
12. Azim AW, Le Guennec Y, Maury G. Spectrally augmented Hartley transform precoded asymmetrically clipped optical OFDM for VLC. IEEE Photonics Technol Lett 2018; 30(23): 2029-2032.
13. Che M, Kuboki T, Kato K. Dimmable optical OFDM based on discrete Hartley transform for indoor visible light illumination and communication. In: 23rd Opto-Electronics and Communications Conference (OECC); 2018, Jeju island, Korea, IEEE, 1-2.
14. Narmanlıoğlu Ö, Uysal M. DCT-OFDM based Visible Light Communications. In: 24th Signal Processing and Communication Application Conference (SIU); 2016, Zonguldak, Turkey, IEEE, 521-524.
15. Zhao H, Liu J, Liang K, Zhang Y, Yi D, Zhong C, Liu S. DHT-based IM/DD optical OFDM system for power data transmission. In: 6th International Conference on Information Engineering for Mechanics and Materials, 2016, Inner Mongolia, Atlantis Press, 20-24.
16. Moreolo MS, Muñoz R, Junyent G. Novel power efficient optical OFDM based on Hartley transform for Intensity-Modulated Direct-Detection systems. J Lightwave Technol 2010; 28(5): 798-805.
17. Moreolo MS. Performance analysis of DHT-based optical OFDM using large-size constellations in AWGN. IEEE Commun Lett 2011; 15(5): 572-574.
18. Dissanayake SD, Armstrong J. Comparison of ACO-OFDM, DCO-OFDM and ADO-OFDM in IM/DD systems. J Lightwave Technol 2013; 31(2): 1063-1072.
19. Godwin RJ, Veena K, Kumar DS. Performance analysis of direct detection Flip-OFDM for VLC system. In: International Conference on Emerging Trends in Engineering, Technology and Science (ICETETS); 2016, India, IEEE, 442-446.
20. Armstrong J, Schmidt BJC. Comparison of asymmetrically clipped optical OFDM and DC-biased optical OFDM in AWGN. IEEE Commun Lett 2008; 12(5): 343-345.
21. Sharifi AA, A new post-coding approach for PAPR reduction in DC-biased optical OFDM systems. Optoelectron Lett 2019; 15(4): 302-305.
22. Tsonev D, Haas H. Avoiding spectral efficiency loss in unipolar OFDM for optical wireless communication. In: IEEE International Conference on Communications; 2014, 3336–3341.
23. Bhadoria MP, Pandey G, Dixit A. Performance evaluation of Visible Light Communication for DCO and ACO optical OFDM techniques. In: National Conference on Communications (NCC); 2019, Bangalore, India, IEEE, 1-6.
24. Çürük SM. Comparison of optical OFDM techniques in Visible Light Communication. In: International Conference on Engineering Technologies; 2021, 227-231.
25. Johnson SG, Frigo M. A modified split-radix FFT with fewer arithmetic operations. IEEE Trans Signal Process 2006; 55(1): 111-119.
26. Skodras AN, Aburdene MF, Nandi AK. Two-band fast Hartley transform. Electron Lett 2015; 51(1): 57-59.