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In this paper, a delta-sigma modulation is proposed for OFDM-PON to enable transmission of OFDM signals via binary IM-DD channels. The delta-sigma modulation is an independent digital signal processing block that converts the analog OFDM signal into binary bit sequence. The OFDM signal can be simply retrieved from the bit sequence, using a low pass...
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... For some iterates "i", the output bit stream, S(0) = S(i), then a limit cycle of some period exists. The Limit cycle is the major issue in the enhancement of performance of SDM [33][34][35][36]. For this purpose, the input and output bit stream as a function of iterate are plotted in Figures 5 and 6 respectively. ...
Sigma-delta modulators use a noise-shaping technique to curtail the noise power in the band of interest during digital-to-analog conversion. Error feedback modulator employs an efficient noise transfer function for time varying inputs than any other sigma-delta modulators. However, the efficiency of the conventional noise transfer function degrades and the quantizer saturation issue provokes when the input signal reaches to full scale. This work proposes a new noise transfer function which is a combination of transfer functions of two-stage Feed-forward delays and a novel Hybrid multi-stage noise shaping-error feedback sigma-delta modulator. The noise transfer function of two-stage Feed-forward delays mitigates the concern of quantizer saturation. The noise transfer function offered by the Hybrid multi-stage noise shaping-error feedback architecture provides sustainable solutions to limit cycles and idle tones. The simulation concludes that the proposed noise-shaping approach obtains comparatively high signal-to-quantization noise ratio than the conventional error feedback modulators. Other performance parameters like spurious-free dynamic range, effective number of bits and signal-to-noise plus distortion ratio are also significantly improved.
... Two commonly exploited versions of the standard DMalso known as linear delta modulation (LDM)-are adaptive delta modulation (ADM) [1,2,[10][11][12][13][14][15][16][17] and sigma delta modulation [1,2,18,19]. ADM has been introduced to resolve the main drawbacks of LDM, i.e. the slope overload and the granular noise, caused by the inadequate choice of quantization step size. ...
Abstract A novel 2‐bit adaptive delta modulation (ADM) algorithm is presented based on uniform scalar quantization and fractional linear prediction (FLP) for encoding the signals modelled by a Gaussian probability density function. The study focusses on two major areas: realization of a 2‐bit adaptive quantizer based on Q‐function approximation that significantly facilitates quantizer design; and implementation of a recently introduced FLP approach with the memory of two samples, which replaces the first‐order linear prediction used in standard ADM algorithms and enables improved performance without increasing transmission costs. It furthermore represents the first implementation of FLP in signal encoding, therefore confirming its applicability in a real signal‐processing scenario. Based on the performance analysis conducted on a real speech signal, the proposed ADM algorithm with FLP is demonstrated to outperform other 2‐bit ADM baselines by a large margin for the gain in signal‐to‐noise ratio achieved over a wide dynamic range of input signals. The results of this research indicate that ADM with adaptive quantization based on Q‐function approximation and adaptive FLP represents a promising solution for encoding/compression of correlated time‐varying signals following the Gaussian distribution.
... One downstream transmitter presented in Fig. 3a constitutes a pseudo-random bit sequence (PRBS) generator providing random binary sequences at 2.5-200 Gbps which are fed to 4-QAM sequence generator having 2-bits per symbol. The 4-QAM signal output is modulated using an OFDM modulator having 512 subcarriers, 64 cyclic prefix points and 1024 fast Fourier transform (FFT) points [47,48]. Then the OFDM modulator generates the in-phase (I) and quadrature (Q) components of the signal for further transmission in the I/Q optical modulator. ...
... In this work, two separate SMF fiber links via bidirectional power splitter are utilized for isolating the upstream and downstream frequencies in the remote nodes (RNs) as it reduces the Rayleigh backscattering (RB) noise interference in the proposed TWDM-PON system utilizing OFDM modulation [43,47]. Table 2 presents the fiber and free-space link parameters used in this proposed work. ...
Today’s access networks are in high demand to fulfill the high bandwidth requirement because of extensive improvement in high transmission rate applications for cloud computing, big data analytics, and other next-generation 5G smart applications. In this work, the symmetrical and bidirectional time and wavelength division multiplexing-passive optical network (TWDM-PON) system is proposed and demonstrated. Orthogonal frequency division multiplexing (OFDM) with 4-level quadrature amplitude modulation is used for downstream and upstream transmission. Also, 625 nm red light-emitting diode is utilized for visible light communication (VLC) using a wireless link to encourage the economic high transmission rate fiber/VLC optical network. The TWDM-PON employing OFDM with the VLC system has been analysed for downstream and upstream channels for variable fiber-wireless link range. Additionally, the impact of a high transmission rate and usage of digital signal processing (DSP) unit to reduce losses due to fiber nonlinearity effects in the proposed link has been investigated. The results show that the maximum faithful wireless and wired range for the proposed system is 140 m and 60 km respectively at 20 Gbps to attain the minimum 3.8 × 10⁻³ BER. The decrease in error vector magnitude (EVM%) by almost 52% with the use of DSP in the proposed system provides a high transmission rate of 200 Gbps in the proposed link. Further, comparative performance of the proposed system with previous latest works in literature reveals a superior performance of the proposed link. The proposed TWDM-PON system provides a next-generation access network from rural areas to urban areas.
... TCM uses set partitionaing and small number of states at the transmitter and Viterbi decoding algorithm is applied to the trellis, with surviving partial paths corresponding to partial signal sequences that are closest to the received sequences. DSM is a modulation technique for encoding analog signal into digital signal [9]- [12]. It is used to convert high bit-count, low-frequency digital signals into lower bit-count, higher-frequency digital signals as part of the process to convert digital signals into analog as part of a digital-to-analog converter (DAC). ...
Visible Light Communication (VLC) has become an accolade to its radio frequency counterpart. In VLC system, orthogonal frequency division multiplexing (OFDM) has drawn much attention, because of simple equalization, high spectral efficiency, high data rate and robustness to intersymbol interference (ISI). Besides, there are emerging applications that ought to be gotten with low latency and high reliability. To diminish power requirements with no transmission capacity extension, Trellis coded modulation (TCM) is utilized as a part of the framework in which the free distance of trellis diagram is equivalent to the minimum distance between the points of constellation focuses in partitioned subsets, which augments the coding gain up i.e. the performance parameter viably. TCM together with VLC-OFDM enhances the transmission execution in reasonable frameworks. In this paper, we propose OFDM which is based on TCM and is planned and exeuted for digitized OFDM frameworks by presenting delta sigma modulation (DSM) considering VLC channel. Simulation results show that the proposed TCM based VLC-OFDM offers incredible robustness against noises and nonlinear degradation. Copyright © 2019 Institute of Advanced Engineering and Science. All rights reserved.
... TCM uses set partitionaing and small number of states at the transmitter and Viterbi decoding algorithm is applied to the trellis, with surviving partial paths corresponding to partial signal sequences that are closest to the received sequences. DSM is a modulation technique for encoding analog signal into digital signal [9]- [12]. It is used to convert high bit-count, low-frequency digital signals into lower bit-count, higher-frequency digital signals as part of the process to convert digital signals into analog as part of a digital-to-analog converter (DAC). ...
span lang="EN-US">Visible Light Communication (VLC) has become an accolade to its radio frequency counterpart. In VLC system, orthogonal frequency division multiplexing (OFDM) has drawn much attention, because of simple equalization, high spectral efficiency, high data rate and robustness to intersymbol interference (ISI). Besides, there are emerging applications that ought to be gotten with low latency and high reliability. To diminish power requirements with no transmission capacity extension, Trellis coded modulation (TCM) is utilized as a part of the framework in which the free distance of trellis diagram is equivalent to the minimum distance between the points of constellation focuses in partitioned subsets, which augments the coding gain up i.e. the performance parameter viably. TCM together with VLC-OFDM enhances the transmission execution in reasonable frameworks. In this paper, we propose OFDM which is based on TCM and is planned and exeuted for digitized OFDM frameworks by presenting delta sigma modulation (DSM) considering VLC channel. Simulation results show that the proposed TCM based VLC-OFDM offers incredible robustness against noises and nonlinear degradation.</span
... the standard of 4G network and provides high data rates that makes it an advantageous choice for an indoor optical wireless communication (OWC) [8] . The real valued positive characteristics can be attained in two of the following categories such as DC biased-optical OFDM (DCO-OFDM) and asymmetrically clipped-optical OFDM (ACO-OFDM). ...
Universal filtered orthogonal frequency division multiplexing (UF-OFDM) is an alluring next generation 5G waveform for communication with small bursts transmission. Moreover, there are arising applications in which short data packet transmissions are awaited to carry fault-finding messages that must be obtained with low latency and high reliability. Visible light communication (VLC) acts as an ideal technology to accomplish these requirements. VLC uses intensity modulation and direct detection techniques and hence they require the signals to certainly be real valued positive sequences. In this paper, a digitized UF-OFDM based on delta sigma modulation (DSM) is proposed. The implementation of the proposed digital UF-OFDM is analyzed in comparison with continuous-time domain representation of UF-OFDM (CT-UF-OFDM). The simulation result exhibits that the system which is projected has better SNR performance than the digitized OFDM. It is found that around 15.8 dB of SNR is improved using the proposed scheme as compared to digital OFDM.
... Increasing the spectral efficiency (SE) is one effective method for high-capacity transmission based on band-limited optical devices. Recently, several alternative spectrally efficient modulations, such as discrete multi-tone (DMT) quadrature amplitude modulation (QAM) [12]- [14], four-level pulse amplitude modulation (PAM-4), and duo-binary (DB) [15]- [18], have been investigated in NG-PON2. DMT is considered suitable for WDM-PON thanks to its high spectrum efficiency, flexible bandwidth configuration, robustness against fiber chromatic dispersion (CD), and orthogonality for convergent multi-band orthogonal frequency division multiplexing (OFDM). ...
This work presents an experimental demonstration of 100-Gbps time-and wavelength-division multiplexed passive optical network (TWDM-PON) with 4×25-Gbps downstream transmission. We take a comparison of faster-than-Nyquist non-return-to-zero (FTN-NRZ), four-level pulse amplitude modulation (PAM-4), electrical duo-binary (EDB), and optical duo-binary (ODB) on the same transmission link. The use of low-cost 10-Gbps optics in combination with digital signal processing (DSP) makes it feasible for a 25-Gb/s per wavelength transmission over 20-km standard single-mode fiber (SSMF) in a cost-effective way. The spectra efficiency and ISI robustness by going to the higher rate are analyzed theoretically. We achieve link budgets of 33.18 dB for FTN-NRZ, and less than 30 dB budgets for PAM-4, ODB, and EDB in downstream transmission. FTN combination with feedforward equalization (FFE) allows FTN-NRZ to have a 4.18 dB margin in power requirement of PR(x) 30 of 10G-EPON, while PAM-4 and ODB with FFE also meet PR(x) 30 with 0.25 dB margin. The results indicate that FTN-NRZ, PAM-4, and ODB can be used for 100G-EPON with 10-Gbps optics, and FTN-NRZ has better performance than other modulations, which is more suitable for next-generation 100G-EPON transmission technique with low-cost.
In this paper, we proposed and experimentally demonstrated a laser sharing filter bank multicarrier passive optical network (FBMC-PON) uplink architecture, to provide high spectrum efficiency frequency division multiple access (FDMA) to the optical network terminals (ONTs) with aggregated uplink data rate of up to 100 Gb/s/λ for each optical network unit (ONU), in a fiber to the frontage (FTTF) scenario utilizing existing copper infrastructure. Intensity modulation (IM) and heterodyne detection are implemented, combined with polarization division multiplexing (PDM) to double the system capacity. The uplink performance of FBMC-PON is emulated with two asynchronous ONT bands in transmission over 20 km single mode fiber (SMF). FBMC with prototype filters (PFs) PHYDYAS, extended Gaussian filter (EGF) and isotropic orthogonal transform algorithm (IOTA) is discussed in comparison with orthogonal frequency division multiplexing (OFDM) in terms of frequency guard band and multiple access interference (MAI). The laser from an external cavity laser (ECL) is split and shared among ONTs. The experimental results show that FBMC can achieve significant improved receiver sensitivity compared to OFDM in the asynchronous uplink. FBMC with PHYDYAS can avoid MAI with frequency guard interval of one time the subcarrier spacing. With optical receiving power (ROP) of -23 dBm, to support 2, 4 and 8 ONTs, the required optical power of the narrow linewidth laser is respectively 10, 16 and 22 dBm with bit error rate (BER) at the hard decision forward error correction (HD-FEC) threshold.
Optical wireless communication (OWC) in the infrared and visible range is an appealing technology, principally in environment arenas where radio communication encounters difficulties. One of the most important subdivisions of OWC technology is the visible light communication (VLC) that uses visible light between the range 400 and 800 THz. VLC uses intensity modulation/direct detection. Hence the signals ought to be strictly real valued positive sequence. The fundamental modulation techniques such as on–off keying and pulse position modulation are in accordance with existing constant current light emitting diode (LED) drivers, however it comes with one drawback of having low spectral efficiency and restricted feasible data rates of VLC. Orthogonal frequency division multiplexing (OFDM) is one of the superior techniques that encode digital data on to multiple carrier frequencies and is widely known for providing high spectral efficiency. Despite of these advantages it comes with the disadvantage of high peak to average power ratio besides complicated digital-to-analog converter and modification of LED drivers of VLC system being pre-requisite. In this paper, we present delta sigma modulation (DSM) based OFDM which offers excellent robustness against noises and nonlinear distortions in VLC systems. The digital OFDM is analyzed in terms of complementary cumulative distribution function, error vector magnitude, bit error rate and received constellation diagram by means of MATLAB simulation to characterize the waveforms. Simulation results show that the DSM considerably enhances the system performance of digitized OFDM. It is found that 12.04 dB of SNR achieved at OSR as 16 using delta sigma modulator.
A delta-sigma-modulated intermediate-frequency-over-fiber (IFoF) transmission system assisted by a correlative-level coding technique is proposed and experimentally demonstrated. Unlike conventional delta-sigma IFoF systems with multiple output levels to achieve higher signal quality or larger capacity, a correlative-level encoder is exploited as a second modulator preceded by the delta-sigma modulator. The encoder compresses the bandwidth of the delta-sigma modulated signal by creating a correlation between adjacent signal symbols. As a result, the sampling frequency of the delta-sigma modulator in the proposed system can be increased beyond the transmission bandwidth of the IFoF system, considerably improving the in-band signal quality and the transmission capacity over the conventional multi-level approach. This is because the quantization noise from the delta-sigma modulation in the proposed scheme is more aggressively pushed away from the signal bandwidth with the high sampling frequency. According to experimental results, the proposed link provides at least a 40% larger transmission capacity for similar in-band signal quality or 2.1% better average EVM performance for the same capacity than the conventional four-level pulse-amplitude-modulation delta-sigma IFoF systems.
