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Showing papers on "Quadrature amplitude modulation published in 2017"


Journal ArticleDOI
TL;DR: The star-shaped 16-ary quadrature amplitude modulation scheme shows superiority over the PS-Square-16QAM in terms of the BER improvement.
Abstract: We investigate and compare the performance of star-shaped 16-ary quadrature amplitude modulation (Star-16QAM) and square-shaped 16QAM (Square-16QAM) in the probabilistic shaping (PS) and uniform schemes with coherent detection. With the help of PS technology, the bit error ratio (BER) improvement achieved in the PS-Star-16QAM scheme is greater than that of the PS-Square-16QAM when compared with the uniform schemes in our numerical simulation and experiment. Therefore, the PS-Star-16QAM shows superiority over the PS-Square-16QAM in terms of the BER improvement.

308 citations


Journal ArticleDOI
TL;DR: Monte Carlo simulations on BER corroborate the analyses and show that the proposed schemes appear as promising multi-carrier transmission alternatives by outperforming the existing OFDM-IM counterparts.
Abstract: Orthogonal frequency division multiplexing with index modulation (OFDM-IM) performs transmission by considering two modes over OFDM subcarriers, which are the null and the conventional $M$ -ary signal constellation The spectral efficiency (SE) of the system, however, is limited, since the null mode itself does not carry any information and the number of subcarrier activation patterns increases combinatorially In this paper, a novel IM scheme, called multiple-mode OFDM-IM (MM-OFDM-IM), is proposed for OFDM systems to improve the SE by conveying information through multiple distinguishable modes and their full permutations A practical and efficient mode selection strategy, which is constrained on the phase shift keying/quadrature amplitude modulation constellations, is designed Two efficient detectors that provide different tradeoffs between the error performance and detection complexity are also proposed The principle of MM-OFDM-IM is further extended to the in-phase and quadrature components of OFDM signals, and the method of generating multiple modes from the $M$ -ary pulse amplitude modulation constellation for this modified scheme is also introduced Bit error rate (BER) analyses are provided for the proposed schemes Monte Carlo simulations on BER corroborate the analyses and show that the proposed schemes appear as promising multi-carrier transmission alternatives by outperforming the existing OFDM-IM counterparts

252 citations


Journal ArticleDOI
TL;DR: A high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency is demonstrated.
Abstract: Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between -4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phase-shift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.

201 citations


Journal ArticleDOI
TL;DR: An intelligent constellation diagram analyzer is proposed to implement both modulation format recognition (MFR) and optical signal-to-noise rate (OSNR) estimation by using convolution neural network (CNN)-based deep learning technique, and the effects of multiple factors on CNN performance are comprehensively investigated.
Abstract: An intelligent constellation diagram analyzer is proposed to implement both modulation format recognition (MFR) and optical signal-to-noise rate (OSNR) estimation by using convolution neural network (CNN)-based deep learning technique. With the ability of feature extraction and self-learning, CNN can process constellation diagram in its raw data form (i.e., pixel points of an image) from the perspective of image processing, without manual intervention nor data statistics. The constellation diagram images of six widely-used modulation formats over a wide OSNR range (15~30 dB and 20~35 dB) are obtained from a constellation diagram generation module in oscilloscope. Both simulation and experiment are conducted. Compared with other 4 traditional machine learning algorithms, CNN achieves the better accuracies and is obviously superior to other methods at the cost of O(n) computation complexity and less than 0.5 s testing time. For OSNR estimation, the high accuracies are obtained at epochs of 200 (95% for 64QAM, and over 99% for other five formats); for MFR, 100% accuracies are achieved even with less training data at lower epochs. The experimental results show that the OSNR estimation errors for all the signals are less than 0.7 dB. Additionally, the effects of multiple factors on CNN performance are comprehensively investigated, including the training data size, image resolution, and network structure. The proposed technique has the potential to be embedded in the test instrument to perform intelligent signal analysis or applied for optical performance monitoring.

194 citations


Journal ArticleDOI
TL;DR: The use of DNNs in combination with signals' amplitude histograms (AHs) for simultaneous optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) in digital coherent receivers is experimentally demonstrated.
Abstract: We experimentally demonstrate the use of deep neural networks (DNNs) in combination with signals’ amplitude histograms (AHs) for simultaneous optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) in digital coherent receivers. The proposed technique automatically extracts OSNR and modulation format dependent features of AHs, obtained after constant modulus algorithm (CMA) equalization, and exploits them for the joint estimation of these parameters. Experimental results for 112 Gbps polarization-multiplexed (PM) quadrature phase-shift keying (QPSK), 112 Gbps PM 16 quadrature amplitude modulation (16-QAM), and 240 Gbps PM 64-QAM signals demonstrate OSNR monitoring with mean estimation errors of 1.2 dB, 0.4 dB, and 1 dB, respectively. Similarly, the results for MFI show 100% identification accuracy for all three modulation formats. The proposed technique applies deep machine learning algorithms inside standard digital coherent receiver and does not require any additional hardware. Therefore, it is attractive for cost-effective multi-parameter estimation in next-generation elastic optical networks (EONs).

188 citations


Journal ArticleDOI
TL;DR: The proposed OFDM-HIQ-IM and LP-OFDM-IQ-IM schemes, as revealed by both theoretical analyses and computer simulations, enable low-complexity detection and exhibit superior error rate performance over the existing OFDM -IM schemes.
Abstract: Index modulation concept has attracted considerable research interest in the past few years As a realization of index modulation in the frequency domain, orthogonal frequency division multiplexing with index modulation (OFDM-IM) has recently been proposed, which conveys information bits through both the subcarrier activation patterns and the amplitude phase modulation constellation points This paper proposes two enhanced OFDM-IM schemes aimed at achieving higher spectral efficiency and diversity gain, respectively The first one, termed OFDM with hybrid in-phase/quadrature index modulation (OFDM-HIQ-IM), explores the I- and Q- dimensions jointly for index modulation, allowing transmission of more index modulation bits in each subcarrier group The second one, termed linear constellation precoded OFDM-IQ-IM (LP-OFDM-IQ-IM), spreads information symbols across two adjacent active subcarriers through linear constellation precoding to harvest additional diversity gain By maximizing the minimum squared Euclidean distance, two different realizations of LP-OFDM-IQ-IM are derived, which leads to a rotated and a diamond-shaped constellation, respectively The proposed OFDM-HIQ-IM and LP-OFDM-IQ-IM, as revealed by both theoretical analyses and computer simulations, enable low-complexity detection and exhibit superior error rate performance over the existing OFDM-IM schemes

165 citations


Proceedings ArticleDOI
01 Sep 2017
TL;DR: It is shown that the normalized generalized mutual information represents an excellent forward error correction (FEC) threshold for uniform as well as for probabilistically shaped QAM and hence allows to accurately predict post-FEC performance from measured pre-Fec data.
Abstract: We show that the normalized generalized mutual information represents an excellent forward error correction (FEC) threshold for uniform as well as for probabilistically shaped QAM and hence allows to accurately predict post-FEC performance from measured pre-FEC data.

155 citations


Journal ArticleDOI
TL;DR: Simulation results verify the theoretical analysis and show that GPQSM outperforms the conventional GPSM scheme and the MIMO scheme under the same spectral efficiency.
Abstract: In this paper, we propose a novel scheme, which is called generalized precoding-aided quadrature spatial modulation (GPQSM), that extends the conventional quadrature spatial modulation to the receiver side. In GPQSM, spatial modulation works in both the in-phase and quadrature parts of the received signals, thus conveying additional information bits compared with conventional generalized precoding-aided spatial modulation (GPSM). The proposed scheme is general and can degenerate into the conventional multiple-input multiple-output (MIMO) scheme. A closed-form upper bound on the average bit error probability of GPQSM is derived. Simulation results verify the theoretical analysis and show that GPQSM outperforms the conventional GPSM scheme and the MIMO scheme under the same spectral efficiency.

153 citations


Journal ArticleDOI
TL;DR: A high-speed air-water optical wireless communication system with both downlink and uplink transmission employing 32-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) and a single-mode pigtailed green-light laser diode (LD).
Abstract: We experimentally demonstrate a high-speed air-water optical wireless communication system with both downlink and uplink transmission employing 32-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) and a single-mode pigtailed green-light laser diode (LD). This work is an important step towards the future study on optical wireless communications between underwater platforms and airborne terminals. Over a 5-m air channel and a 21-m water channel, we achieve a 5.3-Gbps transmission without power loading (PL) and a 5.5-Gbps transmission with PL in the downlink. The corresponding bit error rates (BERs) are 2.64×10-3 and 2.47×10-3, respectively, which are below the forward error correction (FEC) criterion. A data rate of 5.5 Gbps with PL at a BER of 2.92×10-3 is also achieved in the uplink.

143 citations


Journal ArticleDOI
TL;DR: In this article, a brief overview of the various machine learning methods and their application in optical communication is presented and discussed, and supervised machine learning algorithms, such as neural networks and support vector machine, are experimentally demonstrated for in-band optical signal to noise ratio estimation and modulation format classification, respectively.
Abstract: Linear signal processing algorithms are effective in dealing with linear transmission channel and linear signal detection, whereas the nonlinear signal processing algorithms, from the machine learning community, are effective in dealing with nonlinear transmission channel and nonlinear signal detection. In this paper, a brief overview of the various machine learning methods and their application in optical communication is presented and discussed. Moreover, supervised machine learning methods, such as neural networks and support vector machine, are experimentally demonstrated for in-band optical signal to noise ratio estimation and modulation format classification, respectively. The proposed methods accurately evaluate optical signals employing up to 64 quadrature amplitude modulation, at 32 Gbd, using only directly detected data.

142 citations


Journal ArticleDOI
Ronen Dar1, Peter J. Winzer1
TL;DR: In this paper, the potential benefits of digital nonlinearity compensation (NLC) techniques in fully loaded coherent wavelength-division multiplexed (WDM) transmission systems were explored. And the authors showed that while the BP gain is similar to single-carrier systems, PPRN removal can have a much stronger effect, particularly for higher order QAM systems, implying that SCM can be advantageous not only for constant modulus formats such as QPSK, but also for high spectral efficiency systems.
Abstract: We explore the potential benefits of digital nonlinearity compensation (NLC) techniques in fully loaded coherent wavelength-division multiplexed (WDM) transmission systems. After providing an overview of the various classes of nonlinear interference noise (NLIN) and digital signal processing approaches for their mitigation, we consider the two practically most relevant digital NLC methods known today: back-propagation (BP) and equalization of nonlinear phase and polarization rotation noise (PPRN). We consider a wide range of system configurations including a variety of modulation formats from quadrature phase-shift keying (QPSK) to 256-ary quadrature amplitude modulation (QAM), single-carrier and digital subcarrier multiplexed (SCM) optical superchannels, as well as both point-to-point line systems and optically routed networks (ORNs). Using theoretical predictions from the time-domain model for NLIN, we show that the gain in peak signal-to-noise ratio in fully loaded WDM systems using single-channel and three-channel joint BP is typically limited to 0.5 and 1 dB. The additional gain provided by increasing the number of jointly back-propagated channels beyond three is limited to 0.1 dB per additional back-propagated channel. The remarkably slow growth of the BP gain with the bandwidth of the back-propagated signal is shown to apply also for systems in which the receiver employs PPRN removal. We additionally explore the potential benefits of SCM across a wide range of system configurations, including the impact of BP and PPRN removal on SCM systems. We show that while the BP gain is similar to single-carrier systems, PPRN removal can have a much stronger effect, particularly for higher order QAM systems, implying that SCM can be advantageous not only for constant modulus formats such as QPSK, but also for high spectral efficiency systems. In the context of ORNs, we find that SCM not only improves system tolerance to nonlinearities, but also induces significantly smaller performance variations in various ORN scenarios.

Journal ArticleDOI
TL;DR: This paper presents 64-quadrature amplitude modulation (QAM) 60-GHz CMOS transceivers with four-channel bonding capability, which can be categorized into a one-stream transceiver and a two-stream frequency-interleaved (FI) transceiver.
Abstract: This paper presents 64-quadrature amplitude modulation (QAM) 60-GHz CMOS transceivers with four-channel bonding capability, which can be categorized into a one-stream transceiver and a two-stream frequency-interleaved (FI) transceiver. The transceivers are both fabricated in a standard 65-nm CMOS technology. For the proposed one-stream transceiver, the TX-to-RX error vector magnitude (EVM) is less than −23.9 dB for 64-QAM wireless communication in all four channels defined in the IEEE 802.11ad/WiGig. The maximum communication distance with the full rate can reach 0.13 m for 64 QAM, 0.8 m for 16 QAM, and 2.6 m for QPSK using 14-dBi horn antennas. A data rate of 28.16 Gb/s is achieved in 16 QAM by four-channel bonding. The transmitter, receiver, and phase-locked loop consume 186, 155, and 64 mW, respectively. The core area of the transceiver is 3.9 mm2. For the proposed two-stream FI transceiver, four-channel bonding in 64 QAM is realized with a data rate of 42.24 Gb/s and an EVM of less than −23 dB. The front end consumes 544 mW in transmitting mode and 432 mW in receiving mode from a 1.2-V supply. The core area of the transceiver is 7.2 mm2.

Journal ArticleDOI
TL;DR: Experimental results indicate that the compensation scheme can effectively reduce the inter-channel crosstalk, improve the bit-error rate (BER) performance, and recuperate the nondiffracting property of Bessel beams.
Abstract: We present a scheme to realize obstruction- and turbulence-tolerant free-space orbital angular momentum (OAM) multiplexing link by using self-healing Bessel beams accompanied by adaptive compensation techniques. Compensation of multiple 16-ary quadrature amplitude modulation (16-QAM) data carrying Bessel beams through emulated atmospheric turbulence and obstructions is demonstrated. The obtained experimental results indicate that the compensation scheme can effectively reduce the inter-channel crosstalk, improve the bit-error rate (BER) performance, and recuperate the nondiffracting property of Bessel beams. The proposed scheme might be used in future high-capacity OAM links which are affected by atmospheric turbulence and obstructions.

Journal ArticleDOI
TL;DR: In this paper, the authors extend this to generic multi-level modulations by establishing connection to PHY layer multicasting with phase constraints, and design the signal processing algorithms for minimizing the required power under per-user signal to interference noise ratio or goodput constraints.
Abstract: Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems aimed at creating constructive interference among transmitted data streams. This can be enabled by designing the precoded signal of the multiantenna transmitter on a symbol level, taking into account both channel state information and data symbols. Previous literature has studied this paradigm for Mary phase shift keying modulations by addressing various performance metrics, such as power minimization and maximization of the minimum rate. In this paper, we extend this to generic multi-level modulations, i.e., Mary quadrature amplitude modulation by establishing connection to PHY layer multicasting with phase constraints. Furthermore, we address the adaptive modulation schemes which are crucial in enabling the throughput scaling of symbol-level precoded systems. In this direction, we design the signal processing algorithms for minimizing the required power under per-user signal to interference noise ratio or goodput constraints. Extensive numerical results show that the proposed algorithm provides considerable power and energy efficiency gains, while adapting the employed modulation scheme to match the requested data rate.

Journal ArticleDOI
TL;DR: The proposed k-means-clustering-based fiber non linearity mitigation techniques can greatly mitigate the signal impairments caused by the amplified spontaneous emission noise and the fiber Kerr nonlinearity and improve the BER performance.
Abstract: In this work, we proposed two k-means-clustering-based algorithms to mitigate the fiber nonlinearity for 64-quadrature amplitude modulation (64-QAM) signal, the training-sequence assisted k-means algorithm and the blind k-means algorithm. We experimentally demonstrated the proposed k-means-clustering-based fiber nonlinearity mitigation techniques in 75-Gb/s 64-QAM coherent optical communication system. The proposed algorithms have reduced clustering complexity and low data redundancy and they are able to quickly find appropriate initial centroids and select correctly the centroids of the clusters to obtain the global optimal solutions for large k value. We measured the bit-error-ratio (BER) performance of 64-QAM signal with different launched powers into the 50-km single mode fiber and the proposed techniques can greatly mitigate the signal impairments caused by the amplified spontaneous emission noise and the fiber Kerr nonlinearity and improve the BER performance.

Journal ArticleDOI
TL;DR: In this article, the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-toback configuration and in unrepeated nonlinear fiber transmissions was investigated.
Abstract: This paper studies the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-to-back configuration and in unrepeated nonlinear fiber transmissions. For the back-to-back setup, various shaped quadrature amplitude modulation (QAM) distributions are found to have the same implementation penalty as uniform input. By demonstrating in transmission experiments that shaped QAM input leads to lower effective SNR than uniform input at a fixed average launch power, we experimentally confirm that shaping enhances the fiber nonlinearities. However, shaping is ultimately found to increase the AIR, which is the most relevant figure of merit, as it is directly related to spectral efficiency. In a detailed study of these shaping gains for the nonlinear fiber channel, four strategies for optimizing QAM input distributions are evaluated and experimentally compared in wavelength division multiplexing (WDM) systems. The first shaping scheme generates a Maxwell–Boltzmann (MB) distribution based on a linear additive white Gaussian noise channel. The second strategy uses the Blahut–Arimoto algorithm to optimize an unconstrained QAM distribution for a split-step Fourier method based channel model. In the third and fourth approach, MB-shaped QAM and unconstrained QAM are optimized via the enhanced Gaussian noise (EGN) model. Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%. This general behavior is observed in 9-channel and fully loaded WDM experiments.

Journal ArticleDOI
TL;DR: It is found that while modulation on the real part of the eigenvalue induces pulse timing drift and leads to neighboring pulse interactions and nonlinear inter-symbol interference (ISI), it is more bandwidth efficient than modulation in practical settings.
Abstract: In this paper, we experimentally investigate high-order modulation over a single discrete eigenvalue under the nonlinear Fourier transform (NFT) framework and exploit all degrees of freedom for encoding information. For a fixed eigenvalue, we compare different 4 bit/symbol modulation formats on the spectral amplitude and show that a 2-ring 16-APSK constellation achieves optimal performance. We then study joint spectral phase, spectral magnitude and eigenvalue modulation and found that while modulation on the real part of the eigenvalue induces pulse timing drift and leads to neighboring pulse interactions and nonlinear inter-symbol interference (ISI), it is more bandwidth efficient than modulation on the imaginary part of the eigenvalue in practical settings. We propose a spectral amplitude scaling method to mitigate such nonlinear ISI and demonstrate a record 4 GBaud 16-APSK on the spectral amplitude plus 2-bit eigenvalue modulation (total 6 bit/symbol at 24 Gb/s) transmission over 1000 km.

Journal ArticleDOI
TL;DR: The experimental results show that the proposed CCT technique and the pilot-aided secure key agreement are promising for physical-layer security enhancement in future OFDMA-PONs.
Abstract: This paper proposes a chaotic constellation transformation (CCT) technique for physical-layer security enhancement in orthogonal frequency-division multiple access based passive optical networks (OFDMA-PONs). The CCT is performed by using an advanced cat map whose control parameters are generated by a cross chaotic map. Moreover, a pilot-aided security key agreement scheme is proposed to ensure that the security keys are securely distributed between the transmitter and receiver. A 18.86 Gb/s encrypted 16-ary quadrature amplitude modulation based OFDM signal transmission over a 25 km standard single mode fiber is experimentally demonstrated. The experimental results show that the proposed CCT technique and the pilot-aided secure key agreement are promising for physical-layer security enhancement in future OFDMA-PONs.

Journal ArticleDOI
TL;DR: A hierarchical hypothesis-based theoretical framework has been developed to find the probability of error for the proposed BMC method, which is more robust than the one based on EC and at the same time it requires lower complexity than the maximum likelihood approach.
Abstract: This paper presents a hierarchical hypothesis test and a feature-based blind modulation classification (BMC) algorithm for linearly modulated signals. The proposed BMC method is based on the combination of elementary cumulant (EC) and cyclic cumulants. The EC is used to decide whether the constellations are from real, circular, or rectangular class, which is referred to as macro classifier. The cyclic cumulant is used to classify modulation within a subclass, which is referred to as micro classifier. For the micro classification, we use positions of nonzero cyclic frequencies (symbol rate frequency or carrier frequency) of the received signals. A hierarchical hypothesis-based theoretical framework has been developed to find the probability of error for the proposed classification. The method works over a flat fading channel without any knowledge of the signal parameters. The proposed method is more robust than the one based on EC and at the same time it requires lower complexity than the maximum likelihood approach. To validate the proposed scheme, measurement is carried out in realistic scenarios. The performance of the new algorithm is compared with the existing methods. In this paper, we have considered a six-class problem including binary phase-shift keying, quadrature phase-shift keying (QPSK), offset-QPSK, $\pi$ /4-QPSK, minimum shift keying, and 16-quadrature amplitude modulation.

Journal ArticleDOI
TL;DR: This paper theoretically and experimentally investigates the time-dependence of inter-core crosstalk in a homogeneous multi-core fiber when considering signals with various modulation formats and symbol rates and finds that crosStalk power fluctuations depend on the symbol rate, modulation and skew between cores.
Abstract: Inter-core crosstalk is a potential limitation on the achievable data-rates in optical fiber transmission systems using multi-core fibers. Crosstalk arises from unwanted coupling between cores of a homogenous multi-core fiber and it’s average power has been observed to vary over time by 10s of decibels, potentially requiring an additional performance margin to achieve acceptable outage probability. Most investigations of crosstalk have so far only considered continuous wave laser light or amplified spontaneous emission as sources of crosstalk. In this paper, we theoretically and experimentally investigate the time-dependence of inter-core crosstalk in a homogeneous multi-core fiber when considering signals with various modulation formats and symbol rates. We find that crosstalk power fluctuations depend on the symbol rate, modulation and skew between cores. For carrier-free signals, such as quadrature amplitude modulation, the crosstalk power is nearly constant for expected conditions of multi-core transmission systems. However, carrier-supported signals, such as OOK, always induce time-varying crosstalk powers.

Journal ArticleDOI
TL;DR: A novel modulator is proposed, which employs a Wilkinson power divider with a phase shift in one of the design branch and two transistors acting as switches in order to generate M-quadrature amplitude modulation backscatter modulation.
Abstract: Fully passive wireless networks are a key-enabling technologies for the internet of things. Backscatter radios are a hypothesis to design these passive wireless networks. Backscatter modulation allows a remote device to wirelessly transfer information without requiring a traditional transceiver. Instead, a backscatter device leverages a carrier transmitted by an access point or base station. Nevertheless, the traditional approach is to use amplitude shift keying or phase shift keying backscatter solutions which limits the data rate of the sensors, since it transfers only one bit per symbol period. We propose a novel modulator, which employs a Wilkinson power divider with a phase shift in one of the design branch and two transistors acting as switches in order to generate M-quadrature amplitude modulation backscatter modulation. The design strategy for high level order backscatter modulations will be explained and a design approach will be presented in this manuscript.

Journal ArticleDOI
TL;DR: A new carrier index differential chaos shift keying modulation method combining index modulation (IM) with multicarrier DCSK (MC-DCSK) is proposed, which can avoid the disaster caused by the previous designed selectors.
Abstract: A new carrier index differential chaos shift keying (DCSK) modulation method combining index modulation (IM) with multicarrier DCSK (MC-DCSK) is proposed. Two schemes employing two different index selectors and detectors to implement IM and demodulation are introduced. The new designed index selectors are one-to-one mappings between the index symbols and the carrier activation patterns, which can avoid the disaster caused by the previous designed selectors. Analytical bit error rate expressions of the two systems are derived over the additive white Gaussian noise as well as multipath Rayleigh fading channels. Simulation results verify the superiority of one scheme in energy efficiency and another scheme in spectral efficiency, respectively, compared with MC-DCSK.

Journal ArticleDOI
TL;DR: In this article, a four-channel wavelength-division-multiplex (WDM) 560 Gbit/s 128 quadrature amplitude modulation (128QAM)-discrete multi-tone (DMT) signal transmission in a short reach interconnect is demonstrated, where coordinated discrete Fourier transform spread and preequalization are jointly used to simultaneously overcome serious frequency domain power attenuation and reduce the peak-to-average power ratio of the DMT signal.
Abstract: In this paper, we experimentally demonstrated a four-channel wavelength-division-multiplex (WDM) 560 Gbit/s 128 quadrature amplitude modulation (128QAM)-Discrete MultiTone (DMT) signal transmission in a short reach interconnect Coordinated discrete Fourier transform-spread and preequalization are jointly used to simultaneously overcome serious frequency domain power attenuation and reduce the peak-to-average power ratio of the DMT signal An additional postdecision-directed least mean square equalizer is used afterward to further compensate the channel response and mitigate the devices’ implementation penalty These proposed algorithms and equalizer are validated through experiment in this paper, we achieved the highest capacity signal transmission in the four-channel WDM transmission system using intensitymodulation and directdetection over a 24-km single mode fiber with a bit-error-ratio under the hard-decision forward error correction limit of 38 × 10-3

Journal ArticleDOI
Marcin Pikus1, Wen Xu1
TL;DR: A routine to parallelize and increase the throughput of fixed length distribution matching with non-binary output alphabet is presented, achieving similar rate-versus-SNR performance as the symbol-level constant composition distribution matcher, thus providing a high throughput solution for PSCM.
Abstract: A routine to parallelize and increase the throughput of fixed length distribution matching with non-binary output alphabet is presented The routine performs parallel distribution matchings with binary output alphabets, and then maps the binary output streams to symbols from the primary, non-binary alphabet Fixed length distribution matching is essential for probabilistically shaped coded modulation (PSCM), such as the probabilistic amplitude shaping (PAS) In the PAS setup, the novel bit-level distribution matcher achieves similar rate-versus-SNR performance as the symbol-level constant composition distribution matcher, thus providing a high throughput solution for PSCM

Journal ArticleDOI
TL;DR: The recently proposed four-dimensional modulation format family based on 2-ary amplitude 8-ary phase-shift keying (2A8PSK), supporting spectral efficiencies of 5, 6, and 7 bits/symbol, is described in detail.
Abstract: We describe in detail the recently proposed four-dimensional modulation format family based on 2-ary amplitude 8-ary phase-shift keying (2A8PSK), supporting spectral efficiencies of 5, 6, and 7 bits/symbol. These formats nicely fill the spectral efficiency gap between the dual-polarization (DP) quadrature PSK (QPSK) and DP 16-ary quadrature-amplitude modulation (16QAM), with excellent linear and nonlinear performance. Since these modulation formats just use different parity bit expressions in the same constellation, similar digital signal processing can be seamlessly used for different spectral efficiency. A series of nonlinear transmission simulation results shows that this modulation format family outperforms the conventional modulation formats at the corresponding spectral efficiency. We also investigate the adaptive equalizer for these modulation formats.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the nonlinear LED characteristics in the design of pre-distorter for cognitive radio inspired NOMA in VLC, and proposed singular value decomposition-based Chebyshev precoding to improve performance of nonlinear multiple-input multiple-output (MIMO)-NOMA-VLC.
Abstract: Visible light communication (VLC) is one of the main technologies driving the future 5G communication systems due to its ability to support high data rates with low power consumption, thereby facilitating high speed green communications. To further increase the capacity of VLC systems, a technique called non-orthogonal multiple access (NOMA) has been suggested to cater to increasing demand for bandwidth, whereby users’ signals are superimposed prior to transmission and detected at each user equipment using successive interference cancellation. Some recent results on NOMA exist which greatly enhance the achievable capacity as compared with the orthogonal multiple access techniques. However, one of the performance-limiting factors affecting VLC systems is the nonlinear characteristics of a light emitting diode (LED). This paper considers the nonlinear LED characteristics in the design of pre-distorter for cognitive radio inspired NOMA in VLC, and proposes singular value decomposition-based Chebyshev precoding to improve performance of nonlinear multiple-input multiple-output NOMA-VLC. A novel and generalized power allocation strategy is also derived in this paper, which is valid even in scenarios when users experience similar channels. Additionally, in this paper, analytical upper bounds for the bit error rate of the proposed detector are derived for square $M$ -quadrature amplitude modulation.

Journal ArticleDOI
TL;DR: In this article, the average bit error probability has been analyzed for phase-shift keying in the presence of phase noise for a terrestrial free-space optical (FSO) link impaired by lognormal fading.
Abstract: For terrestrial free-space optical (FSO) communication systems, subcarrier intensity modulation represents an attractive alternative to on-off keying or pulse-position modulation, which is mainly because of the larger spectral efficiency. However, some degradation of the error performance must be taken into account due to nonperfect synchronization of carrier frequency and phase. In a recently published paper, the average bit error probability has been analyzed for $M$ -ary phase-shift keying in the presence of phase noise for a terrestrial FSO link impaired by lognormal fading. In the this paper, we are extending this study to a gamma-gamma model, which is usually applied in case of moderate-to-strong scintillation effects. On top of that, pointing errors, caused by a misalignment between transmitter and receiver of the FSO link, are considered as well. Since a closed-form solution is not available under general conditions and because numerical methods are time-consuming, suffering in part also from serious convergence and stability problems, we provide approximate closed-form expressions, which are accurate enough over a wide signal-to-noise ratio range.

Journal ArticleDOI
TL;DR: Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%.
Abstract: This paper studies the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-to-back configuration and in unrepeated nonlinear fiber transmissions. For back-to-back, various shaped quadrature amplitude modulation (QAM) distributions are found to have the same implementation penalty as uniform input. By demonstrating in transmission experiments that shaped QAM input leads to lower effective SNR than uniform input at a fixed average launch power, we experimentally confirm that shaping enhances the fiber nonlinearities. However, shaping is ultimately found to increase the AIR, which is the most relevant figure of merit as it is directly related to spectral efficiency. In a detailed study of these shaping gains for the nonlinear fiber channel, four strategies for optimizing QAM input distributions are evaluated and experimentally compared in wavelength division multiplexing (WDM) systems. The first shaping scheme generates a Maxwell-Boltzmann (MB) distribution based on a linear additive white Gaussian noise channel. The second strategy uses the Blahut-Arimoto algorithm to optimize an unconstrained QAM distribution for a split-step Fourier method based channel model. In the third and fourth approach, MB-shaped QAM and unconstrained QAM are optimized via the enhanced Gaussian noise (EGN) model. Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%. This general behavior is observed in 9-channel and fully loaded WDM experiments.

Journal ArticleDOI
TL;DR: High-quality real-time video streaming over an underwater wireless optical communication (UWOC) link up to 5 m distance is experimentally demonstrated using phase-shift keying (PSK) modulation and quadrature amplitude modulation (QAM) schemes.
Abstract: We experimentally demonstrate high-quality real-time video streaming over an underwater wireless optical communication (UWOC) link up to 5 m distance using phase-shift keying (PSK) modulation and quadrature amplitude modulation (QAM) schemes. The communication system uses software defined platforms connected to a commercial TO-9 packaged pigtailed 520 nm directly modulated laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter and an avalanche photodiode (APD) module as the receiver. To simulate various underwater channels, we perform laboratory experiments on clear, coastal, harbor I, and harbor II ocean water types. The measured bit error rates of the received video streams are 1.0 × 10-9 for QPSK, 4-QAM, and 8-QAM and 9.9 × 10-9 for 8-PSK. We further evaluate the quality of the received live video images using structural similarity and achieve values of about 0.9 for the first three water types, and about 0.7 for harbor II. To the best of our knowledge, these results present the highest quality video streaming ever achieved in UWOC systems that resemble communication channels in real ocean water environments.

Journal ArticleDOI
TL;DR: High spectral efficient back-to-back and wireless THz transmission around 325 GHz is experimentally demonstrated using a 64-QAM-OFDM modulation format and a 10 GHz wide wireless channel resulting in a data rate of 59 Gbit/s.
Abstract: We report on a record spectral efficient terahertz communication system using a coherent radio-over-fiber (CRoF) approach. High spectral efficient back-to-back and wireless THz transmission around 325 GHz is experimentally demonstrated using a 64-QAM-OFDM modulation format and a 10 GHz wide wireless channel resulting in a data rate of 59 Gbit/s.