Orthogonal Frequency Division Multiplexing (OFDM) technology1 has found wide application in optical communication systems due to its efficient use of available bandwidth, absence of intersymbol interference, and mitigation of dispersion and nonlinearity effects in the optical channel. However, OFDM has several drawbacks, the key one is the problem of high peak-to-average power ratio (PAPR)2 . In optical transmission systems3 , this becomes particularly relevant as it leads to nonlinear distortions caused not only by power amplifiers but also by LED emitters, thereby reducing the efficiency of converting light into communication and significantly impacting the lifespan of the LED and laser diode. This paper describes a new PAPR reduction method based on the application of the Kronecker product in the transmitter and receiver matrices formation in asymmetrically-clipped optical OFDM. It is applied in the transmitter side by the Kronecker product of the IFFT matrix and the data matrix, and then in the receiver by the Kronecker product of the FFT matrix and the channel matrix. Creating these matrices can distribute the signal power across all subcarriers and maintain orthogonality, thereby contributing to reducing the peak-factor. Numerical experiments were conducted to evaluate the effectiveness of the method. Simulation results show that this approach can reduce the peak-factor value by 2.3%. Overall, the developed method based on the Kronecker product provides a promising solution for reducing PAPR in OFDM optical systems and can be used to improve the performance and efficiency of data transmission in optical communication systems, moreover, this signal undergoes further transformation - the formation of quasi-orthogonal multiplexing methods for transmission on the air network.
KEYWORDS: Orthogonal frequency division multiplexing, Signal filtering, Modulation, Fourier transforms, Energy efficiency, Signal processing, Optical filters, Electronic filtering
This article proposes a method for improving energy efficiency by reducing the peak power of the emitted signal in systems with DFT-s-OFDM for fiber-optic segments of future mobile networks of the 5G and 6G generation, based on the use of an improved "raised cosine" shaping filter, as well as ZT-DFT-s-OFDM technology for improved energy efficiency. Various new waveforms and modulation schemes are presented that would be both energetically and spectrally efficient. The analysis of the ratio of the peak signal power level to the average level for signals with DFT-s-OFDM in its various modifications in radio-optic networks is presented, various technologies for the formation of DFT-s-OFDM are analyzed depending on the method of access to the subscriber, such as DFDMA, LFDMA and IFDMA, considering the bandwidth extension factor.
KEYWORDS: Modulation, Orthogonal frequency division multiplexing, Signal processing, Radio over Fiber, Filtering (signal processing), Radio optics, Quadrature amplitude modulation, Networks, Electronic filtering, Frequency division multiplexing
6G mobile networks will support a wide range of services with different technical requirements and in different frequency bands. To achieve this goal, the use of radio-over-fiber (RoF) technology together with optical space division multiplexing (SDM) technology is an important basis for creating both a transport architecture and a hybrid radio-optical centralized architecture or cloud radio access network (C-RAN) 6G fronthaul. At the same time, the 6G signals processing technologies and the modulation schemes must meet the stringent requirements for a mobile data transmission network. The paper presents a study and simulation results of the process of signal conversion and retransmission with a promising data processing technology – DFT-s-OFDM with rotated QAM modulation over a fiber-optic line using RoF technology; a numerical estimation of PAPR level is also given.
The article provides an overview of the use of space division multiplexing (SDM) technology in radio-over-fiber (RoF) data transmission systems in future high-speed scalable 6G wireless networks. The features of using the SDM technology in the radio access network are analyzed. The application of new specialized few-mode fibers in 6G networks for the useful information transmission is proposed. The results of experimental studies of custom optical fibers designed for vortex mode generation are also presented.
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