Discrete Fourier Transform Spreading Research Articles

Orthogonal Circulant Multiplexing for Bandwidth- Limited Direct-Detected Optical Communication Systems

We propose and investigate a novel orthogonal circulant multiplexing (OCM) technology for bandwidth-limited direct detection (DD) optical systems. We analytically derive that any OCM, i.e. using any orthogonal circulant matrix for multiplexing, can redistribute the noise uniformly across the subcarriers. However, the distribution of inter-symbol interference (ISI) and inter-carrier interference (ICI) strongly depends on the design of OCM. The previously proposed orthogonal chirp division multiplexing (OCDM), although showing better ISI/ICI tolerance than discrete-Fourier-transform spread (DFT-S) orthogonal frequency division multiplexing (OFDM), is a kind of OCM with poorer performance. We propose and analytically reveal that OCM based on chirp-like polyphase sequence (CLPS), general chirp sequence (GCS), sparse CLPS (SCLPS), and sparse GCS (SGCS) can achieve flatter ISI/ICI distribution across subcarriers and so better performance than OCDM in bandwidth-limited DD systems. The optimal parameter vector of the E-parameter CLPS is a Zadoff-Chu sequence while the parameter α in GCS should be larger. The optimal performance can be achieved by either CLPS (or GCS) using a larger E (or α) or SCLPS (or SGCS) with optimized sparsity. ∼110Gbit/s experiments using Mach-Zehnder modulator or electro-absorption modulator and receiver of 10-GHz photodiode or 8-GHz avalanche photodiode are conducted. The results agree with the theory and show that the proposed OCM outperforms conventional OFDM, DFT-S OFDM, and OCDM.

Papr reduction of FBMC-OQAM signals using Phase Search-PTS and modified discrete fourier transform spreading

In this research, a novel peak-to-average power ratio (PAPR) reduction technique for filter bank multicarrier (FBMC) modulation systems is presented. With multicarrier systems like FBMC, the strategy focuses on the survival of the fittest principle to suit the value of PAPR. The Filter Bank Multicarrier with Offset Quadrature Amplitude Modulation (FBMC-OQAM) has recently captured the attention of numerous academics due to its minimal adjacent channel leakage ratio (CLR). Unfortunately, the issue of increased PAPR measurement has a negative impact on the effectiveness of the FBMC system's energy measurement. In this study, the Phase search-based Partial Transmit Sequence (PS-PTS) approach and Modified Discrete Fourier Transform Spreading (MDFT) are developed for the PAPR reduction of the FBMC-OQAM signals. The increased PAPR measurement is reduced using the PTS and MDFT with osprey optimization method, which may result in a PAPR reduction of roughly 5.1 dB as comparable to the conventional approach.

Research on alleviating nonlinear problem by data feature extraction and fusion based on DFT-spread

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) system is susceptible to nonlinear effects because of its intrinsic high peak-to-average ratio (PAPR). In this paper, two methods based on discrete Fourier transform spread (DFT-S) are introduced to improve the nonlinear tolerance of CO-OFDM system by extracting and fusing data features, which extract the features of communication data and perform feature fusion to get the important significance of the data. The first one is based on the 2-ary amplitude shift keying (2-ASK) modulation and the Hermitian symmetry of DFT, and the other one is based on the advantages of selective mapping algorithm and characteristics of data subcarrier mapping mode which has a significant impact on PAPR. Simulation results show that compared with the traditional CO-OFDM and DFT-S CO-OFDM systems, the improved methods have better performance in terms of PAPR and BER.

Transmission of 4096-QAM OFDM at D-band.

We experimentally demonstrate the transmission of multi-order quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) millimeter wave signals at D-band. Meanwhile, the system nonlinearity analysis is also given, which is originated from the unsatisfactory optoelectronic devices, multi-order QAM and the high peak-to-average power ratio (PAPR) of OFDM signal. To alleviate the system nonlinearity, Volterra nonlinearity compensation (VNC) is adopted. Probabilistic shaping (PS) has been regarded as an effective approach to ensure the system robustness. By using the technologies of probabilistic shaping and Volterra nonlinearity compensation, 57.21-Gbit/s 4096-QAM OFDM signal at 117 GHz can be delivered over 13.42-m wireless distance in our experiment, achieving the normalized general mutual information (NGMI) threshold of 0.83 with 25% soft-decision forward-error correction (SD-FEC) overhead. In addition, we simulated the D-band millimeter wave simulation system in VPI software. The NGMI performance between conventional and discrete Fourier transform-spread (DFT-S) 16-QAM OFDM has been compared in simulation at the same optical signal-to-noise ratio (OSNR). The case of conventional 16-QAM OFDM has better performance. To the best of our knowledge, this is the first demonstration of transmission of multi-order QAM OFDM millimeter wave signal at D-band using PS and VNC methods.

OFDM-based 2D generalized optical quadrature spatial modulation for MIMO-OWC systems

An innovative scheme, named orthogonal frequency division multiplexing (OFDM)-based two-dimensional (2D) generalized optical quadrature spatial modulation (GOQSM), is proposed for bandlimited multiple-input multiple-output optical wireless communication (MIMO-OWC) systems. In this scheme, by way of combining two consecutive time slots into one time block, 2D GOQSM mapping can be executed in spatial domain and time domain. Therefore, more spatial bits can be transmitted, resulting in the increase of system spectral efficiency. Furthermore, discrete Fourier transform (DFT) spreading is further introduced in OFDM-based 2D GOQSM systems, so as to substantially reduce the peak-to-average power ratio (PAPR) of the transmitted signals. To evaluate and compare the performance of OFDM-based 2D GOQSM systems with other traditional systems, numerical simulations are conducted under various spectral efficiencies. The obtained simulation results prove that the proposed OFDM-based 2D GOQSM scheme with DFT spreading can achieve better bit error rate performance and lower PAPR than other benchmark schemes.

PAPR Reduction of OFDM with DFT Spreading Method

Future communication systems will demand the transmission of huge amounts of data, therefore will require a highly linear power amplifier. The Orthogonal Frequency Division Multiplexing (OFDM) technique is widely used in multimedia services for providing high data rates and providing high Quality of Service. The transmitter power amplifier's range of operation in a communication system is linear. Signal distortion happens when the input signal's amplitude exceeds the linear range of the transmitter power amplifier. Therefore, the transmitter's input signal has to have a low peak to average power ratio (PAPR). The OFDM system has been recognized as the high rate wireless radio channel transmission. Therefore, it will also be highly beneficial for the high-speed communication system. However, due to the extremely high PAPR issue, using the OFDM system in a communication system is not simple. It results in extremely low power efficiency. Therefore, it is crucial to lower the PAPR in the OFDM system in order to employ it in the communication system. By using a discrete Fourier matrix, the Discrete Fourier Transform spreading strategy may significantly lower the PAPR of an OFDM signal. This paper describes the PAPR reduction approach in OFDM signals and examines the effectiveness of OFDM.

Multi-band DFT-S 100 Gb/s 32 QAM-DMT transmission in intra-DCI using 10 G-class EML and low-resolution DAC.

In this paper, 100 Gb/s/λ 32 quadrature amplitude modulation discrete multi-tone (QAM-DMT) transmission using 10 G-class electro-absorption modulated laser (EML) and 4/5-bit digital-to-analog converters (DACs) are experimentally demonstrated to meet the requirement of intra-datacenter interconnection (intra-DCI). Unequal length multi-band (ULM) discrete Fourier transform spread (DFT-S) precoding is investigated to alleviate the distortion induced by the high peak-to-average power ratio (PAPR) of DMT. The results show that the required computational complexity of ULM DFT-S precoding with 2-bands (k1=256, k2=64) decreases sharply compared to the traditional DFT-S technique with only about 0.5 dB receiver sensitivity penalty. In addition, compared to the equal length multi-band (ELM) DFT-S precoding, the ULM DFT-S precoding can bring about 2.5 dB receiver sensitivity improvement with slight added computational complexity. With the assistance of ULM DFT-S precoding and noise shaping (NS) technique, the bit-error ratio (BER) of 100 Gb/s 32 QAM-DMT signal generated by 5-bit DAC over 2-km single-mode fiber (SMF) transmission can reach the hard-decision forward error correction (HD-FEC) threshold with received optical power (ROP) of -6.5 dBm, with only additional 39.9% multiplier and 33.7% adder.

Orthogonal Subblock Division Multiple Access for OFDM-IM-Based Multi-User VLC Systems

In this paper, we propose and experimentally demonstrate an orthogonal subblock division multiple access (OSDMA) scheme for orthogonal frequency division multiplexing with index modulation (OFDM-IM)-based multi-user visible light communication (MU-VLC) systems, where both single-mode index modulation (SM-IM) and dual-mode index modulation (DM-IM) are considered. In order to overcome the low-pass frequency response and the light-emitting diodes (LED) nonlinearity issues of practical MU-VLC systems, OSDMA is employed together with discrete Fourier transform spreading (DFT-S) and interleaving. The feasibility and superiority of the proposed scheme have been successfully verified via both simulations and hardware experiments. More specifically, we evaluate and compare the peak-to-average power ratio (PAPR) performance and the bit error rate (BER) performance of OFDM-SM-IM, DFT-S-OFDM-SM-IM, OFDM-DM-IM and DFT-S-OFDM-DM-IM without and with interleaving. Experimental results show that remarkable distance extensions can be achieved by employing DFT spreading and interleaving for both SM-IM and DM-IM in a two-user OSDMA-VLC system.

Performance evaluation of MIMO DFT-Spread WR-OFDM system for spectrum efficiency and power efficiency

ABSTRACT It is important to design a spectrum-efficient and power-efficient wireless communication system, which is the main design target in cellular and wireless communication engineering. Basically, to make it, the desired system must have a low peak-to-average power ratio (PAPR), low-level of out-of-band (OOB) power emission and can provide a high throughput. In this paper, we propose a high-throughput cellular communication system, namely Discrete Fourier Transform-Spread Windowing and Restructuring Orthogonal Frequency Division Multiplexing (DFT-Spread WR-OFDM), which has considerably low PAPR and low OOB power emission for upcoming next-generation beyond 5G (B5G) and 6G cellular communication systems. High PAPR is still one of the challenging issues for the MIMO-OFDM system. The proposed system is an effective arrangement of DFT-Spreading and windowing techniques to reduce PAPR and OOB power emission, respectively. Multiuser diversity is obtained using localized subcarrier mapping. We take advantages of spatial multiplexing to enhance the data throughput significantly. Additionally, frequency-domain equalization (FDE)-minimum mean squared error (MMSE) is used to combat the inter-symbol interference (ISI) effect. Simulation results verify that the suggested system considerably lowers PAPR and OOB power emission compared to the conventional systems. Furthermore, the proposed scheme shows better bit error rate (BER) performance over the MIMO Rayleigh fading channel environment. Simulation results also confirmed that the channel capacity of our suggested system is better than the conventional multi-carrier systems.

Chirp-Like Polyphase Sequence Based Discrete Circulant Transform Spread OFDM for Bandwidth-Limited IM/DD Systems

We propose and investigate chirp-like polyphase sequence (CLPS) based discrete circulant transform spread (DCrT-S) OFDM in bandwidth-limited intensity-modulation and direct-detection systems. This scheme can control the distribution of residual inter-symbol interference (ISI) and inter-carrier interference (ICI) across subcarriers by adjusting the CLPS's parameters. We also propose a sparse CLPS (SCLPS) scheme, by inserting zeros between the elements of the CLPS, to further balance the effects of the ISI/ICI and the noise and improve the performance by optimizing both the CLPS's parameters and the sparsity. We reveal the optimal design rule of CLPS/SCLPS analytically and investigate the performance of the proposed schemes using two-parameter CLPS in ∼110-Gbit/s simulations and experiments. It is shown that the optimal parameter vector of the CLPS is a Zadoff-Chu sequence that spreads the ISI/ICI more evenly over subcarriers. The performance is further improved by optimizing the sparsity. The optimal CLPS and sparsity are insensitive to the received optical power, the system bandwidth, the length of cyclic prefix, the chirp parameter and the signal data rate, and so can be pre-set without channel information. Both CLPS- and SCLPS-based DCrT-S-OFDM outperform Nyquist PAM, conventional OFDM, discrete-Fourier-transform spread (DFT-S) OFDM, and orthogonal-circulant-transform precoded (OCT-P) OFDM. By using the proposed scheme, the data rate is enhanced by 6.7% and 3.2% compared to DFT-S-OFDM and OCT-P-OFDM at a bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> , while the complexity is reduced to 57.9% of OCT-P-OFDM.

2×2 MIMO Equalizer Enabled Transmitter Side IQ Imbalance Compensation for Optical Single Sideband Direct Detection System

Recently, optical single sideband (SSB) based direct detection (DD) has been considered as a promising candidate for inter data center interconnects (inter-DCIs). Kramers-Kronig (KK) receiver is always applied to eliminate the signal-to-signal beating interference (SSBI) caused by the square law-detection of a single-ended photodiode (PD) in SSB DD system. The electro-to optical (E/O) conversion of the complex signal can be realized by IQ modulator (IQM). However, IQ imbalance exists at the transmitter since the in-phase and quadrature-phase ports of IQM are driven by the real and imaginary parts of the signal, respectively. In this paper, we show the theoretical analysis of the transmitter side (Tx-side) IQ imbalance includes time delay, amplitude mismatch and phase mismatch. Tx-side IQ imbalance will seriously deteriorate the system performance. To deal with the impairment caused by Tx-side IQ imbalance, a 22 real-value multiple-input multiple-output (MIMO) equalizer is proposed and implemented, and the system with the impact of these three factors are investigated in simulation, respectively. Besides, a transmission of 180 Gb/s/ discrete Fourier transform spread (DFT-S) orthogonal frequency division multiplexing (OFDM) signal over 80-km single mode fiber (SMF) is experimentally demonstrated with bit error rate (BER) below the soft-decision forward error correction (SD-FEC) threshold of 210-2 enabled by the proposed 22 MIMO equalizer.

Numerical Simulation and Implementation of FBMC System with Low PAPR for Efficient 5G Applications

Recently, FBMC (Filter Bank Multi-Transporter) has emerged as an alternative to orthogonal frequencies Division Multiplexing (OFDM) (OFDM). As part of the FBMC strategy, wider ranges of frequencies are now within reach, as well as lower out-of-band (OOB) outflows. Comparatively speaking, The Peak-to-average Power Ratio (PAPR) in OFDM frameworks is still high for FBMC, so this isn't surprising. The FBMC framework has been given some OFDM-based PAPR reduction innovation.. PAPR advancements are reduced in this paper OFDM frameworks employ phase modification (PR) and modified PR (MPR) algorithms as a foundation for their proposed FBMC framework. Simply integrate DFT (Discrete Fourier Transform) Spread range and FBMC-OQAM (Filter Bank Multi-Transporter) into SC-FDMA (Single Bearer Recurrence Division Multiple Entrance). As long as you keep the quadrature sufficiency tweak in check, PAPR (peak normal power proportion), which was formerly negligible, is now much less. Taking advantage of DFT's single-bearer impact, unique approaches can be taken. There should be no problems with the quadrature phase channel in terms of the IQ coefficients for each subcarrier. We use FBMC waveforms to generate DFT augmentation and ITSM conditions, and then select the one with the lowest pinnacle power as a means of further increasing the amount decreased PAPR. Regardless of the number of candidates, the basic count portion, for example, DFT Share with IDFT, only executes once, unlike the typical SI (side data) based PAPR reduction Programs.

Efficient Technique for PAPR and BER Reduction in Downlink Large Scale MU-MIMO-OFDM System

Background &amp; Objective: The Orthogonal Frequency Division Multiplexing (OFDM) based large scale multiuser multiple input multiple output (LS-MU-MIMO) system is a preferred choice for signal transmission because it can substantially enhance the spectral and energy efficiency of the next-generation wireless systems. However, there are several practical issues in implementing large multiuser-MIMO-OFDM systems and one of the critical issues is the high Peak-to-Average- Power Ratio (PAPR). Due to the use of a large number of antennas at the Base Station (BS) of an LSMU- MIMO-OFDM system, it requires a large number of Power Amplifiers (PAs) which are needed to be connected to each antenna element. The high PAPR in an OFDM based LS-MU-MIMO system results in the decrease in the efficiency of PAs and enhancement in nonlinear signal distortions. This work is concerned with the reduction in PAPR of LS-MU-MIMO-OFDM systems using the SCFDMA scheme for the downlink transmission. The reduction in PAPR is achieved on the basis of discrete Fourier transform spreading (DFT-S) scheme known as DFT-SC-FDMA. The SC-FDMA scheme can achieve the reduction in PAPR of MIMO-OFDM signal up to the level of single-carrier transmission. Further, the reduction in PAPR is achieved with the sub mapping schemes such as localized FDMA (LFDMA) and distributed FDMA (DFDMA), Interleaved FDMA (IFDMA). Result: In this work, we propose to perform jointly multiuser MMSE precoding, SC-IFDMA and antenna reservation technique to reduce the PAPR and Bit Error Rate (BER) of the large MU-MIMO system. To show the effectiveness of the proposed scheme in the reduction of PAPR with different modulation techniques, subcarriers, and subcarrier mapping schemes, the results are compared with the existing OFDM based large MU-MIMO system. Conclusion: The MATLAB simulation results confirm that our proposed combination of MMSE MUprecoding, SC-IFDMA and antenna reservation technique is able to reduce PAPR and BER to a significant extent for LS-MU-MIMO-OFDM systems.

Reliability-aware subcarrier mapping strategy of QC-LDPC encoded symbols in bandwidth-limited IM/DD OFDM systems.

We propose a simple yet effective strategy to map forward error correction (FEC) encoded symbols to subcarriers in bandwidth-limited intensity-modulation and direct-detection (IM/DD) optical orthogonal frequency division multiplexing (OFDM) systems. The design exploits the reliability diversity of OFDM subcarriers in bandwidth-limited systems and allocates FEC encoded systematic symbols and parity-check symbols to high-reliability and low-reliability subcarriers, respectively. In contrast to adaptively-loaded OFDM or systems using multiple sets of FECs with different code rates for different subcarriers, the proposed design does not induce additional complexity and avoids the round-trip delay between transceivers. We investigate the performance of the proposed design in quasi-cyclic low-density parity-check (QC-LDPC) coded OFDM system under different decoding iterations. Experimental results of 120-Gb/s signals over 2 km and 100-Gb/s signals over 5 km show that the OFDM system using the proposed mapping strategy is superior to both OFDM and discrete-Fourier-transform spread (DFT-S) OFDM using conventional mappings without considering the subcarrier diversity or using pre-equalization, regardless of the received optical power, the FEC code rate, the length of the cyclic prefix, the transmission distance, the number of decoding iterations, and the degree distribution of the QC-LDPC optimized under either an infinite or a limited number of iterations. The proposed mapping is optimal when the systematic symbols and parity-check symbols are exactly loaded to high-reliability and low-reliability subcarriers respectively. The studies enable the proposed strategy promising for bandwidth-limited IM/DD OFDM systems such as low-latency data center interconnects.

Faster-Than-Nyquist 400 G Implementation Using 126-GBaud QPSK-OFDM With 88-GSa/s Undersampling

In this study, we demonstrated generation and transmission of 114 Gbaud and 126 Gbaud faster-than-Nyquist (FTN) discrete Fourier transform-spread (DFT-spread) quadrature phase shift keying orthogonal frequency division multiplexing (QPSK-OFDM) with 88-Gsa/s sampling rate digital-to-analog converters (DACs) experimentally. It is the first time to realize 400G FTN DFT-spread QPSK-OFDM signal per optical carrier for metro and regional applications, which will be a solution for network operators to address the issue of increasing bandwidth derived from the rapid popularization of mobile Internet and the wide application of IoT (Internet of Things technology). Delay-and-add filter (DAF) is adopted to realize frequency shaping at the transmitter to keep higher portions of energy of signal at low frequencies, which makes the OFDM much more robust to strong filtering effect. After pre-equalization, bit error rate (BER) performance of 114 GBaud and 126 GBaud FTN DFT-spread QPSK-OFDM has been significantly improved, and maximum-likelihood sequence estimation (MLSE) shows a better effect than binary decoding in the aspect of against the inter symbol interference (ISI) introduced by spectrum compression. The effective bit rate of dual polarization 126 Gbaud FTN DFT-spread QPSK-OFDM which is generated with 88 GSa/s sampling rate is 410.08 Gb/s, to the exclusion of all overhead including TSs, cyclic prefix (CP), and 20% forward error correction (FEC) coding. We successfully transmit 8 × 400 Gbit/s FTN DFT-spread QPSK-OFDM signal generated from 88 Gsa/s sampling rate DAC over 420 km single mode fiber (SMF) with the BER under 2.4 × 10−2.

Design Simulation and Assessment of Low PAPR FBMC System for Energy Efficient 5G Applications

As of late, filter bank multi-transporter (FBMC) has seemed incredible enthusiasm as an option in contrast to orthogonal frequencies Division Multiplexing (OFDM). FBMC plan has extended Frequency capability and low out of band (OOB) outpourings Compared to OFDM. In any case, FBMC still experiences high positions Peak-to-average power proportion (PAPR) in OFDM frameworks. Some OFDM-based PAPR decrease innovation has been received FBMC framework. In this paper, new advancements for PAPR decrease. The proposed FBMC framework depends on its development Use phase modification (PR) and altered PR (MPR) methods Used in OFDM frameworks. Novel comparable to SC-FDMA (single carrier repeat division) Multiple passageway), essentially unite DFT (Discrete Fourier Transform) Spread reach and FBMC-OQAM (channel bank multi-carrier With balance quadrature adequacy change) simply prompts The unimportant PAPR (top typical force extent) is decreased. Using the single carrier effect of DFT spread, exceptional The condition of the IQ coefficient of each subcarrier (in stage Should be content with the quadrature stage channel. So as to further build the amount decreased PAPR, we produce DFT augmentation and ITSM condition in FBMC waveform and select the one with the most minimal pinnacle power. Regardless of whether there are numerous Candidate age, the fundamental count part, for example, DFT Share with IDFT, simply execute once, in contrast to customary SI (side data) based PAPR decrease Program.

Peak-to-Average Power Ratio Reduction Method Based on Partial Transmit Sequence and Discrete Fourier Transform Spreading

Recently, filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) has received increasing attention from researchers, owing to its merits and superior spectral efficiency. High peak-to-average power ratio (PAPR) occurs in approximately all multicarrier systems, including FBMC/OQAM, and may cause bit-error-rate (BER) degradation if not appropriately handled. Conventional PAPR reduction methods for orthogonal frequency division multiplexing (OFDM), such as partial transmit sequence (PTS), selective mapping (SLM), and discrete Fourier transform (DFT) spreading, are ineffective in FBMC/OQAM because of the different structure of the symbols. This study proposes a novel method combining DFT spreading and PTS methods to reduce the PAPR of FBMC/OQAM systems with reasonable computational complexity. Numerical results obtained from various computer simulations show that the proposed method achieves a noticeable enhancement in the PAPR performance of the FBMC/OQAM signal compared to other existing methods without affecting the BER performance. Further, the computational complexity analysis and BER performance of the proposed method are presented in comparison to typical existing methods. From our computer simulations, the proposed method reduces the PAPR by approximately 32.8% compared to that of the conventional methods, and the BER performance is improved by 25% with a high-power amplifier effect.

PAPR reduction using twin symbol hybrid optimization-based PTS and multi-chaotic-DFT sequence-based encryption in CP-OFDM system

Orthogonal frequency division multiplexing (OFDM) is considered as one of the most significant transmission methodologies of the recent past. Moreover, it permits easy demodulation and modulation. To find the new OFDM-based waveform to be used in fifth generation which is one of the foremost open issues for wireless networks of the next generation. In addition, the OFDM is affected by the maximum Peak-to-Average Power Ratio (PAPR). In order to minimize these problems, this paper proposed a Twin Symbol Hybrid Optimization used as a basis of the Partial Transmit Sequence (TSHO-PTS) method of Cyclic Prefix-OFDM (CP-OFDM). This CP-OFDM achieves the requirements of 5G telecommunication standards. Moreover, the exhaustive searching for optimal phase factors might increase the computational cost of PTS. To beat this problem, a hybrid version of slap swarm optimization (SSO) and Bald Eagle Search (BES) algorithm is introduced to investigate the phase factor optimally by the PTS method. Digital chaotic sequences are used to ensure the physical layer security during the data transmission scheme for the Discrete Fourier Transform Spread OFDM (DFT-S-OFDM) subcarrier allocation. The simulation takes place in the MATLAB platform, and the performances are evaluated by several performance metrics like Complementary cumulative distribution function (CCDF), Bit Error Rate (BER), and computational complexity. The performance of the proposed model is compared with various existing approaches and previous works. From the implemented results, the proposed strategy achieved less (5 dB) PAPR, minimum (10–8) BER, less processing time (0.18 s) than the existing schemes, and hence the complexity also very low (7%) than others.

Demonstration of 200 Gbit/s Single λ Dual Band DMT Transmission With a SE of 6.29 bit/s/Hz

With the increasing demand of bandwidth, a higher capacity communication system is required for short-reach optical link. Intensity modulation/direct detection (IM-DD) is considered as a reasonable method, due to its low cost and power consumption. In the aspect of digital signal processing (DSP), discrete Fourier transform-spread (DFT-s) precoding can be used to reduce peak to average power ratio (PAPR) and average the noise among the subcarriers. In addition, probabilistic shaping (PS) turns out to further increase the system capacity. We experimentally demonstrated a 200 Gbit/s single λ dual band DMT transmission with a spectrum efficiency (SE) of 6.29 bit/s/Hz. The achievable information rate (AIR) of the proposed dual band signal increases about 30 Gbit/s compared with that of single band signal. Moreover, single-sideband (SSB) signal and signal with guard band are implemented to mitigate the frequency selective fading of optical fiber chromatic dispersion (CD). The performance of these two methods are quite closed for short reach transmission. Considering the signal-signal beat interference (SSBI) introduced by the SSB signal, an extra Volterra filter is applied in DSP. Besides, an extra optical filter is required to generate the SSB signal.

Comparison of Geometrically Shaped 32-QAM and Probabilistically Shaped 32-QAM in a Bandwidth-Limited IM-DD System

We use the generalized pair-wise optimization (PO) algorithm to optimize the geometrically shaped 32-ary quadrature amplitude modulation (GS-32-QAM) constellation and adopt the probabilistic fold shaping (PFS) scheme to generate the probabilistically shaped 32-QAM (PS-32-QAM) format. We present a detailed comparison among the application of GS-32-QAM, PS-32-QAM and uniform 32-QAM in an intensity modulation/direct detection (IM/DD) system with a bandwidth-limited digital-to-analog converter (DAC). We experimentally demonstrate the 32-QAM discrete Fourier transform-spread (DFT-S) discrete multi-tone (DMT) signal transmission over 1-km standard single mode fiber (SSMF) in an IM/DD system with a net data rate of 108.29-Gb/s/λ, and achieve 0.6 dB and 0.9 dB receiver sensitivity gain using PS and GS constellations, respectively. In the high signal to noise ratio (SNR) case with a net bit rate of 69.61-Gb/s/λ, the PS-32-QAM DMT signal can provide the receiver sensitivity gain of 0.5 dB while the receiver sensitivity gain of the GS-32-QAM DMT signal is 0.4 dB, compared to the uniform 32-QAM DMT signal. Although PS-32-QAM achieves better receiver sensitivity gain than GS-32-QAM in the high SNR case, the proposed GS-32-QAM format outperforms PS-32-QAM in the low SNR case.