Showing papers on "QAM published in 2017"
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
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
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.
116 citations
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.
111 citations
TL;DR: In this paper, a detailed comparison of applying three advanced modulation formats including pulse amplitude modulation-4 (PAM-4), carrierless amplitude and phase modulation-16 QAM (CAP-16), and discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) with low-cost direct detection for 100-Gb/s/λ metro optical transmission systems is presented.
Abstract: Metro network, as a medium distance transmission system, poses a special challenge of transmission capacity and cost. In this paper, we present a detailed comparison of applying three advanced modulation formats including pulse amplitude modulation-4 (PAM-4), carrierless amplitude and phase modulation-16 QAM (CAP-16), and discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) with low-cost direct detection for 100-Gb/s/λ metro optical transmission systems. These modulation formats are all experimentally demonstrated with similar digital signal processing algorithms. Three kinds of chromatic dispersion (CD) compensation ways named CD precompensation method, single sideband (SSB), and dispersion compensating fiber (DCF) are also compared. Two types of modulators including an IQ modulator and a dual-drive Mach–Zehnder modulator are employed to generate SSB or CD precompensated signals in this experiment and their transmission performance is also evaluated. To the best of our knowledge, this is the first time that the performance of single-wavelength 100-G signal transmission based on direct detection is evaluated over 480 km of standard single mode fiber with PAM-4, CAP-16, and DFT-S OFDM modulation formats.
86 citations
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.
77 citations
TL;DR: In this paper, a GaN blue laser diode (BLD)-based visible-light communication link is demonstrated in a seawater environment to provide 16-quadrature amplitude modulation orthogonal frequency-division multiplexing (QAM OFDM) data transmission at 14.8 Gbps over 1.7 m.
Abstract: A GaN blue laser diode (BLD)-based visible-light communication link is demonstrated in a seawater environment to provide 16-quadrature amplitude modulation orthogonal frequency-division multiplexing (QAM OFDM) data transmission at 14.8 Gbps over 1.7 m. Lengthening the seawater distance to 10.2 m only decreases the transmission data rate by 4 Gbps, as caused by the frquency response limitation of the used avalanche photodiode. To optimize the QAM-OFDM transmission, the sampling rate of the encoded data is compromised to avoid the aliasing and oversampling effects during the waveform extraction procedure. The sampling rate is optimized to 3–5 times of the encoded data bandwidth for suppressing peak-to-average power ratio. Oversampling not only filters out background noise but also attenuates data amplitude to degrade transmission performance. Without using the multicarrier spectrally filtered OFDM, the 16-QAM OFDM data format only promotes the transmission capacity of BLD up to 7.6 Gbps in seawater. With spectrally filtering out the sidelobes of each OFDM subcarrier, the allowable modulation bandwidth is greatly improved from 1.9 to 2.7 GHz, as the intercarrier interference induced crosstalk between subbands is relieved to improve the SNR of the carried data with a raw data rate of up to 10.8 Gbps.
65 citations
TL;DR: This paper proves that the full elimination of mutual coupling effect is not achievable solely by tuning the values of the antenna load impedances, and introduces the proposed A/D scheme for both PSK and QAM modulations, where performance gains with respect to conventional techniques are obtained.
Abstract: In this paper, we propose a joint analog-digital (A/D) beamforming scheme for the point-to-point multiple-input-multiple-output system, where we exploit mutual coupling by optimizing the load impedances of the transmit antennas. Contrary to the common conception that mutual coupling strictly harms the system performance, we show that mutual coupling can be beneficial by exploiting the concept of constructive interference. By changing the value of each load impedance for the antenna array based on convex optimization, the mutual coupling effect can be manipulated so that the resulting interference aligns constructively to the useful signal vector. We first prove that the full elimination of mutual coupling effect is not achievable solely by tuning the values of the antenna load impedances. We then introduce the proposed A/D scheme for both PSK and QAM modulations, where performance gains with respect to conventional techniques are obtained. The implementation of the proposed schemes is also discussed, where a lookup table can be built to efficiently apply the calculated load impedances. The numerical results show that the proposed schemes can achieve an improved performance compared to systems with fixed mutual coupling, especially when the antenna spacing is small.
61 citations
TL;DR: This paper proposes a low complexity implementation of minimum mean square error equalization to jointly tackle the channel and waveform-induced interference and finds that the benefits of FBMC and GFDM can be exploited with complexity comparable to the former (quasi-) orthogonal waveforms.
Abstract: This paper studies the link level performance of orthogonal frequency division multiplexing (OFDM) and four other advanced waveforms, namely, filtered OFDM (F-OFDM), universal-filtered OFDM (UF-OFDM), filter bank multicarrier (FBMC) and generalized frequency division multiplexing (GFDM). Compared to OFDM, the two filtered variants achieve lower out-of-band (OOB) emissions and can mostly preserve the conventional OFDM-based transceiver design. For the latter two non-orthogonal waveforms, this paper proposes a low complexity implementation of minimum mean square error equalization to jointly tackle the channel and waveform-induced interference. On this basis, the benefits of FBMC and GFDM can be exploited with complexity comparable to the former (quasi-) orthogonal waveforms. The observed benefits include lower peak-to-average power ratio (PAPR) and smaller frame error rate (FER) under challenging doubly dispersive multiple-input multiple-output (MIMO) fading channels. Additionally, linear filtering of FBMC offers an ultra-low OOB emission, while a good compromise in the usage of time and frequency resources can be achieved by circular filtering of GFDM. In the comparison of offset quadrature amplitude modulation (OQAM) versus QAM for non-orthogonal waveforms, OQAM can offer lower PAPR, while smaller FERs can be achieved by QAM in rich multipath fading channels.
61 citations
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.
60 citations
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.
TL;DR: The demonstrated high data-rate OFDM-based UVB communication link paves the way for realizing high-speed non-line-of-sight free-space optical communications.
Abstract: A demonstration of ultraviolet-B (UVB) communication link is implemented utilizing quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM). The demonstration is based on a 294-nm UVB-light-emitting-diode (UVB-LED) with a full-width at half-maximum (FWHM) of 9 nm and light output power of 190 μW, at 7 V, with a special silica gel lens on top of it. A −3-dB bandwidth of 29 MHz was measured and a high-speed near-solar-blind communication link with a data rate of 71 Mbit/s was achieved using 8-QAM-OFDM at perfect alignment. 23.6 Mbit/s using 2-QAM-OFDM when the angle subtended by the pointing directions of the UVB-LED and photodetector (PD) is 12 degrees, thus establishing a diffuse-line-of-sight (LOS) link. The measured bit-error rate (BER) of 2.8 ×10−4 and 2.4 ×10−4, respectively, are well below the forward error correction (FEC) criterion of 3.8 ×10−3. The demonstrated high data-rate OFDM-based UVB communication link paves the way for realizing high-speed non-line-of-sight free-space optical communications.
TL;DR: This work presents nonlinear impairment mitigation of wavelength division multiplexed signals, through optical phase conjugation (OPC), and demonstrates the operation of the system using both 16 and 64-quadrature amplitude modulation (QAM) signals.
Abstract: We present nonlinear impairment mitigation of wavelength division multiplexed signals, through optical phase conjugation (OPC). We conduct our experiments on a 400-km-long installed fiber link equipped with erbium-doped fiber amplifiers, with the OPC placed close to the middle of the link. Our OPC configuration realizes efficient reuse of the signal bandwidth, avoiding the loss of half of the spectral band typical of most phase conjugating schemes. We demonstrate the operation of the system using both 16- and 64-quadrature amplitude modulation (QAM) signals and report Q-factor improvements up to 0.5 and 2.5 dB for 16- and 64-QAM, respectively.
01 Mar 2017
TL;DR: An optimized codebooks generation method for four ring star QAM based signaling constellation is proposed and it is demonstrated that by selecting the optimum design parameters, the bit error rate (BER) can be improved.
Abstract: Sparse code multiple access (SCMA) is a non- orthogonal codebook (CB) based multiple access scheme, proposed to cope with the heterogeneous and challenging performance requirements for mission critical communication and massive machine-type communication (MTC) in the fifth Generation (5G) wireless system. In this paper, the performance of SCMA has been studied and analyzed, considering the impact of the energy diversity and minimum Euclidean distance of the mother constellation, overloading of the system and the layer specific operators for codebooks generation. An optimized codebooks generation method for four ring star QAM based signaling constellation is proposed. It is demonstrated that by selecting the optimum design parameters, the bit error rate (BER) can be improved. Moreover, an overloading technique is also proposed to enable higher connectivity at lower decoding complexity
TL;DR: The high accuracy of the proposed MFI scheme is experimentally demonstrated without sacrificing the tolerance of both laser phase noise and fiber nonlinearity for various modulation formats up to dual-polarization (DP) 64QAM.
Abstract: We propose a RF-pilot aided modulation format identification (MFI) technique to enable a hitless flexible coherent transceiver with fast format switching. For the MFI, modulation format information is encoded to the amplitude of the RF-pilot, which can be simultaneously used for the compensation of both laser phase noise and fiber nonlinearity. The proposed MFI technique is able to identify arbitrary modulation formats including multi-dimensional formats and hybrid QAM formats. The high accuracy of the proposed MFI scheme is experimentally demonstrated without sacrificing the tolerance of both laser phase noise and fiber nonlinearity for various modulation formats up to dual-polarization (DP) 64QAM. Finally, over 2240 km standard single mode fiber (SSMF) link, we experimentally demonstrate a hitless coherent transceiver with a fast block-by-block modulation format switching enabled by the proposed MFI.
TL;DR: This work reports the first on-line high-speed and large-capacity secure optical communication system by combining a quadrature amplitude modulation/quantum noise stream cipher technology and a quantum key distribution technology where secure key delivery is realized with an extremely weak laser light comparable to a single photon.
Abstract: We report the first on-line high-speed and large-capacity secure optical communication system. This was realized by combining a quadrature amplitude modulation/quantum noise stream cipher technology where a coherent multi-level optical signal is hidden in quantum noise and a quantum key distribution technology where secure key delivery is realized with an extremely weak laser light comparable to a single photon. In our security analysis, we adopt a realistic assumption, namely, that an adversary does not have a lossless fiber. To show the advantage of this scheme, we performed a 128 QAM, 70-Gbit/s single-channel transmission over 100 km with a spectral efficiency of as high as 10.3 bits/s/Hz. This is the fastest data rate and highest spectral efficiency yet achieved in quantum cryptography with a realistic assumption.
TL;DR: In this paper, the performance of a hybrid M-ary quadrature amplitude modulation multi-pulse pulse position modulation (hybrid QAM-MPPM) technique was investigated in both turbulence-free and gamma-gamma freespace optical (FSO) channels.
Abstract: The performance of a hybrid M-ary quadrature amplitude modulation multi-pulse pulse-position modulation (hybrid QAM-MPPM) technique is investigated in both turbulence-free and gamma-gamma freespace optical (FSO) channels. Both the spectral efficiency and asymptotic power efficiency of the hybrid QAM-MPPM are estimated and compared to traditional QAM and MPPM techniques. The bit error rate (BER) of intensity-modulation direct-detection (IM-DD) systems adopting the hybrid technique is investigated over turbulence-free FSO channels. Upper-bound expressions for the average BER and outage probability are derived for FSO systems by adopting a hybrid QAM-MPPM scheme over gamma-gamma turbulent channels. In addition, the performance of a Reed-Solomon coded hybrid QAM-MPPM is considered. The obtained expressions are used to numerically investigate the performance of the hybrid technique. Our results reveal that, under the conditions of comparable data rates, the same bandwidth, and the same energy per bit, FSO systems adopting the hybrid technique outperform those adopting traditional MPPM, QAM, and on-off keying (OOK) techniques by 1.5, 0.4, and 3 dB, respectively, in the case of turbulence-free channels. Moreover, the new technique shows a better BER performance under different turbulence levels when compared with traditional MPPM and QAM techniques in turbulent FSO communication channels. Also, it shows an improvement in outage probability compared to MPPM, QAM, and OOK over gamma-gamma FSO channels.
TL;DR: The proposed MB-OCT precoding exhibits an attractive ladder-like signal-to-noise-ratio (SNR) profile, thus can significantly reduce system BER by applying different quadrature amplitude modulation (QAM) level to different sub-bands and exhibits reduced implementation complexity and comparable BER performance with the adaptive-loaded DMT.
Abstract: In this paper, we propose and experimentally demonstrate a channel-independent multi-band orthogonal circulant matrix transform (MB-OCT) precoding, to efficiently combat the severe frequency-selective fading of visible light communications (VLC). The proposed MB-OCT precoding exhibits an attractive ladder-like signal-to-noise-ratio (SNR) profile, thus can significantly reduce system BER by applying different quadrature amplitude modulation (QAM) level to different sub-bands. The impacts of sub-band number, signal bandwidth, and length of cyclic prefix (CP) on bit error rate (BER) of the VLC system are investigated. We experimentally compare BER performance of the proposed MB-OCT precoding with that of the conventional MB discrete Fourier transform (MB-DFT) precoding and the adaptive-loaded discrete multitone (DMT). The results show that the MB-OCT precoding outperforms the MB-DFT precoding and the single-band case for different data rates. Furthermore, it exhibits reduced implementation complexity and comparable BER performance with the adaptive-loaded DMT. For ~700-Mb/s VLC system with 2-m transmission distance, the BER is reduced from 1.53 × 10−2 to 1.17 × 10−4 by using the proposed MB-OCT precoding.
TL;DR: In this article, a detailed comparison of applying three advanced modulation formats including pulse amplitude modulation-8 (PAM-8), carrierless amplitude and phase modulation-64 QAM (CAP-64), and discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) with a bandwidth limited direct-detection receiver for 100 Gb/s/λ optical transmission systems is presented.
Abstract: We present a detailed comparison of applying three advanced modulation formats including pulse amplitude modulation-8 (PAM-8), carrier-less amplitude and phase modulation-64 QAM (CAP-64), and discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) with a bandwidth-limited direct-detection receiver for 100 Gb/s/λ optical transmission systems. These modulation formats are all experimentally demonstrated with corresponding digital signal processing (DSP) algorithms. The comparison is carried out to evaluate the performance of each modulation format in terms of nonlinear equalization, received optical power and optical signal to noise ratio (OSNR). Our experimental results show that only 112 Gbit/s DFT-S OFDM is successfully achieved over 50 km of SSMF under the hard decision-forward error correction (HD-FEC) threshold of 3.8 × 10−3.
TL;DR: Analytical lower bound expressions of average symbol error rate (ASER) for general-order hexagonal quadrature amplitude modulation (QAM) and rectangular QAM and RQAM schemes are derived for multiple amplify-and-forward relay networks over independent and nonidentically distributed Nakagami-type fading channels with an integer-valued fading parameter using a well-known cumulative-distribution-function-based approach.
Abstract: In this paper, analytical lower bound expressions of average symbol error rate (ASER) for general-order hexagonal quadrature amplitude modulation (QAM) and rectangular QAM (RQAM) schemes are derived for multiple amplify-and-forward relay networks over independent and nonidentically distributed Nakagami-m fading channels with an integer-valued fading parameter using a well-known cumulative distribution-function-based approach. Furthermore, ASER expressions for 32-cross QAM, differentially encoded quadriphase shift keying (QPSK), and π/4-QPSK modulation schemes are derived for the considered systems. The asymptotic ASER expression is also derived for the RQAM scheme, which is useful to examine system's diversity order. Numerically evaluated results are verified by Monte Carlo simulation.
TL;DR: An intelligent system is made which does not require any knowledge of symbol rate, carrier frequency, and any training phase to set thresholds, and detects the type of modulation blindly in real time, and shows an improvement in the classification accuracy.
Abstract: Modulation classification using OPTICS clustering algorithm has been proposed.Algorithm is reliably classifying 4ASK, 8ASK, BPSK, QPSK and 8QAM above 9dB SNR.Classification is unsupervised and generalized for any orders ASK, PSK and QAM.Algorithm is implemented and tested on real time RF signal using labVIEW. Automatic recognition of digital modulation schemes is becoming an active research area in many covert operations. It has many military applications where surveillance and electronic warfare requires a type of modulation in intercepted signal to prepare jamming signals. Most of the approaches are based on modulated signal's component, but the modulation type can be best identified with the use of constellation diagram. The proposed technique is able to recognize M-QAM, M-ASK, and M-PSK modulation scheme in Additive White Gaussian Noise (AWGN) environment. As the constellation points form clusters in the I-Q plane, the order of the modulation can be obtained by estimating the correct number of clusters, which is calculated by OPTICS algorithm. The least square error has been calculated using linear regression from the obtained constellation points, to identify either ASK or PSK and QAM. The error is least for ASK which differentiates ASK from PSK and QAM. To identify between the PSK and QAM, k-means clustering is employed to find the number of centroids equal to order of modulation estimated by OPTICS. With the difference in maximum and minimum absolute value of the centroids, PSK or QAM is recognized. The proposed method shows an improvement in the classification accuracy which reaches 100% using 1024 symbols at 20dB compared to 98.89%, 98.05%, and 98% when using more complex classifiers like Support Vector Machine, Naive Bayes Classifier, KNN respectively. The method used is unsupervised whereas most of the methods in the literature require training phase to set the thresholds or weights for final model to detect modulation type. This algorithm is also implemented in LabVIEW, and tested on real-time signals. An intelligent system is made which does not require any knowledge of symbol rate, carrier frequency, and any training phase to set thresholds, and detects the type of modulation blindly in real time. Modulated RF signals are generated by NI PXIe-5673 (RF transmitter). NI PXI 5600 is used to downconvert RF signal and NI PXI-5142 (100 MS/s OSP digitizer) is used to sample the downverted signal.
TL;DR: In this article, a comprehensive study of the coded performance of long-haul spectrally-efficient WDM optical fiber transmission systems with different coded modulation decoding structures is presented, and the achievable information rates are derived for three different square quadrature-amplitude modulation (QAM) formats and the optimal format is identified as a function of distance and specific decoder implementation.
Abstract: A comprehensive study of the coded performance of long-haul spectrally-efficient WDM optical fiber transmission systems with different coded modulation decoding structures is presented. Achievable information rates are derived for three different square quadrature-amplitude modulation (QAM) formats and the optimal format is identified as a function of distance and specific decoder implementation. The four cases analyzed combine hard-decision (HD) or soft-decision (SD) decoding together with either a bit-wise or a symbol-wise demapper, the last two suitable for binary and nonbinary codes, respectively. The information rates achievable for each scheme are calculated based on the mismatched decoder principle. These quantities represent true indicators of the coded performance of the system for specific decoder implementations and when the modulation format and its input distribution are fixed. In combination with the structure of the decoder, two different receiver-side equalization strategies are also analyzed: electronic dispersion compensation and digital backpropagation. We show that, somewhat unexpectedly, schemes based on nonbinary HD codes can achieve information rates comparable to SD decoders and that, when SD is used, switching from a symbol-wise to a bit-wise decoder results in a negligible penalty. Conversely, from an information-theoretic standpoint, HD binary decoders are shown to be unsuitable for spectrally-efficient, long-haul systems.
TL;DR: A simple composite second-order (CSO) cancellation technique based on the digital signal processing (DSP) for the radio-over-fiber (RoF) transmission system implemented by using directly modulated lasers (DMLs) is proposed and demonstrated.
Abstract: We propose and demonstrate a simple composite second-order (CSO) cancellation technique based on the digital signal processing (DSP) for the radio-over-fiber (RoF) transmission system implemented by using directly modulated lasers (DMLs). When the RoF transmission system is implemented by using DMLs, its performance could be limited by the CSO distortions caused by the interplay between the DML’s chirp and fiber’s chromatic dispersion. We present the theoretical analysis of these nonlinear distortions and show that they can be suppressed at the receiver by using a simple DSP. To verify the effectiveness of the proposed technique, we demonstrate the transmission of twenty-four 100-MHz filtered orthogonal frequency-division multiplexing (f-OFDM) signals in 64 quadrature amplitude modulation (QAM) format over 20 km of the standard single-mode fiber (SSMF). The results show that, by using the proposed technique, we can suppress the CSO distortion components by >10 dB and achieve the error-vector magnitude performance better than 6% even after the 20-km long SSMF transmission.
TL;DR: A theoretical expression for the BER performance of SCMA systems with codebooks based on star quadrature amplitude modulation over the additive white Gaussian noise channel is derived based on the statistics of the phase angle in SCMA constellations.
Abstract: In this letter, the average bit error rate (BER) performance of sparse code multiple access (SCMA) systems with codebooks based on star quadrature amplitude modulation (star-QAM) signaling constellations over the additive white Gaussian noise channel is analyzed and evaluated Motivated by the fact that the phase rotation plays an important role in designing codebooks and thus can significantly affect the BER performance in SCMA system, we derive a theoretical expression for the BER performance based on the statistics of the phase angle in SCMA constellations Numerical and simulation results corroborate the proposed analysis
TL;DR: This work proposes an orbital angular momentum (OAM)-based, secure, energy-efficient multidimensional coded modulation, and proposes employing the Slepian sequences as either basis functions in baseband or impulse responses of antenna arrays in passband to further increase the dimensionality of the wireless system and enable beyond 1-Tb/s wireless transmission.
Abstract: To address key challenges for beyond 5G wireless technologies in a simultaneous manner, we propose an orbital angular momentum (OAM)-based, secure, energy-efficient multidimensional coded modulation. The key idea is to employ all available degrees of freedom (DOFs) to convey the information over the wireless links, including amplitude, phase, polarization state, and spatial-domain DOFs. In particular, the OAM is associated with the azimuthal phase dependence of the wavefront, and represents an underutilized DOF. Given that OAM eigenstates are orthogonal, an arbitrary number of bits per symbol can be transmitted. Here, we propose utilizing OAM DOF not only to improve spectral and energy efficiencies, but also to significantly improve the physical-layer security of future wireless networks. To implement the OAM multiplexer and demultiplexer in the RF domain, we propose using properly designed antenna arrays. We also propose employing the Slepian sequences as either basis functions in baseband or impulse responses of antenna arrays in passband to further increase the dimensionality of the wireless system and enable beyond 1-Tb/s wireless transmission. Monte Carlo simulations demonstrate high tolerance to fading effects of LDPC-coded multidimensional signaling schemes compared with the conventional LDPC-coded QAM.
TL;DR: A differential pulse code modulation (DPCM) based digital mobile fronthaul architecture is proposed and experimentally demonstrated to support universal filtered multicarrier signal that is one candidate waveform for the 5th generation mobile systems.
Abstract: A differential pulse code modulation (DPCM) based digital mobile fronthaul architecture is proposed and experimentally demonstrated. By using a linear predictor in the DPCM encoding process, the quantization noise can be effectively suppressed and a prediction gain of 7~8 dB can be obtained. Experimental validation is carried out with a 20 km 15-Gbaud/λ 4-level pulse amplitude modulation (PAM4) intensity modulation and direct detection system. The results verify the feasibility of supporting 163, 122, 98, 81 20-MHz 4, 16, 64, 256 QAM based antenna-carrier (AxC) containers with only 3, 4, 5, 6 quantization bits at a sampling rate of 30.72MSa/s in LTE-A environment. Further increasing the number of quantization bits to 8 and 9, 1024 quadrature amplitude modulation (1024 QAM) and 4096 QAM transmission can be realized with error vector magnitude (EVM) lower than 1% and 0.5%, respectively. The supported number of AxCs in the proposed DPCM-based fronthaul is increased and the EVM is greatly reduced compared to the common public radio interface (CPRI) based fronthaul that uses pulse code modulation. Besides, the DPCM-based fronthaul is also experimentally demonstrated to support universal filtered multicarrier signal that is one candidate waveform for the 5th generation mobile systems.
TL;DR: The obtained experimental and numerical results show that the proposed HCCD-based encryption scheme has excellent resistance to illegal optical network units.
Abstract: Physical layer security is of key interest for secure passive optical networks (PONs). We propose a hybrid chaotic confusion and diffusion (HCCD)-based encryption method for physical layer security enhancement in optical orthogonal frequency division multiplexed PONs (OFDM-PONs). Here, the real (I) and imaginary (Q) parts of OFDM symbols are separately scrambled by using different permutations before performing inverse fast Fourier transform. This scheme can realize that the transmitted quadrature amplitude modulation (QAM) symbols and the symbol-to-subcarrier mapping are simultaneously changed and disrupted. The scrambling permutations are generated by an improved logistic map, whose iteration parameters are set as the security keys. 11.3-Gb/s 16 QAM and 14.1-Gb/s 32 QAM IQ scrambled OFDM signals have been successfully transmitted over 25-km standard single mode fiber in an experimental demonstration. The scrambling performance and the security of the proposed encryption scheme are further analyzed. The obtained experimental and numerical results show that the proposed HCCD-based encryption scheme has excellent resistance to illegal optical network units.
TL;DR: Simulation results show the effectiveness of the proposed GASDRSE and STSDRSE techniques in increasing the data rate and spectral efficiency of 16-QAM FTN signaling, without increasing the bit-error-rate, the bandwidth, or the data symbols energy, when compared with the Nyquist signaling.
Abstract: Faster-than-Nyquist (FTN) signaling is a promising non-orthogonal transmission technique to considerably improve the spectral efficiency. This paper presents the first attempt in the literature to estimate the transmit data symbols of any high-order quadrature amplitude modulation (QAM) FTN signaling in polynomial time complexity. In particular, we propose a generalized approach to model the finite alphabet of any high-orderQAMconstellation as a high degree polynomial constraint. Then, we formulate the high-order QAM FTN signaling sequence estimation problem as a non-convex optimization problem. As an example of a high-order QAM, we consider 16-QAM FTN signaling and then transform the high degree polynomial constraint, with the help of auxiliary variables, to multiple quadratic constraints. Such transformation allows us to propose a generalized approach semidefinite relaxation (SDR)-based sequence estimation (GASDRSE) technique to efficiently provide a sub-optimal solution to the NP-hard non-convex FTN detection problem, with polynomial time complexity. For the particular case of 16-QAM FTN signaling, we additionally propose a sequence estimation technique based on concepts from the set theory. We show that the set theory SDR-based sequence estimation (STSDRSE) technique is of lower complexity when compared with the proposed GASDRSE. Simulation results show the effectiveness of the proposed GASDRSE and STSDRSE techniques in increasing the data rate and spectral efficiency of 16-QAM FTN signaling, without increasing the bit-error-rate, the bandwidth, or the data symbols energy, when compared with the Nyquist signaling.
TL;DR: The previous optimization algorithm for FSMSs is extended to cover an average power constraint, thus enabling temporal optimization with multiamplitude constellations output, such as QAM, and results in increased received SNR and, thereby, increased achievable information rates (AIR)s under memoryless assumption.
Abstract: In this paper, finite state machine sources (FSMSs) are used to shape quadrature amplitude modulation (QAM) for nonlinear transmission in optical fiber communication systems. The previous optimization algorithm for FSMSs is extended to cover an average power constraint, thus enabling temporal optimization with multiamplitude constellations output, such as QAM. The optimized source results in increased received SNR and, thereby, increased achievable information rates (AIR)s under memoryless assumption. The AIR is increased even further when taking the channel and transmitter memory into account via trellis processing at the receiver. Significant gains are reported in the highly nonlinear region of transmission for an FSMS of up to second order and 16QAM and particularly for unrepeated transmission. At the optimal launch power of WDM transmission, the FSMS order needs to be increased further in order to notably outperform previous probabilistic shaping schemes.
TL;DR: The adaptive multiband scheme mitigates equalization requirements and enhances the energy efficiency by avoiding frequency notches and utilizing the maximum available signal-to-noise ratio and channel bandwidth.
Abstract: A cognitive tri-band transmitter (TX) with a forwarded clock using multiband signaling and high-order digital signal modulations is presented for serial link applications. The TX features learning an arbitrary channel response by sending a sweep of continuous wave, detecting power level at the receiver side, and then adapting modulation scheme, data bandwidth, and carrier frequencies accordingly based on detected channel information. The supported modulation scheme ranges from nonreturn to zero/Quadrature phase shift keying (QPSK) to Pulse-amplitude modulation (PAM) 16/256-Quadrature amplitude modulation(QAM). The proposed highly reconfigurable TX is capable of dealing with low-cost serial channels, such as low-cost connectors, cables, or multidrop buses with deep and narrow notches in the frequency domain (e.g., a 40-dB loss at notches). The adaptive multiband scheme mitigates equalization requirements and enhances the energy efficiency by avoiding frequency notches and utilizing the maximum available signal-to-noise ratio and channel bandwidth. The implemented TX prototype consumes a 14.7-mW power and occupies 0.016 mm2 in a 28-nm CMOS. It achieves a maximum data rate of 16 Gb/s with forwarded clock through one differential pair and the most energy efficient figure of merit of 20.4 $\mu \text{W}$ /Gb/s/dB, which is calculated based on power consumption of transmitting per gigabits per second data and simultaneously overcoming per decibel worst case channel loss within the Nyquist frequency.