Showing papers on "Quadrature amplitude modulation published in 2016"
TL;DR: The history of research and development related to coherent optical communications is reviewed and the principle of coherent detection is described, including its quantum-noise characteristics, which discusses the role of digital signal processing in mitigating linear transmission impairments, estimating the carrier phase, and tracking the state of polarization of the signal in coherent receivers.
Abstract: The recently developed digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as $M$ -ary phase-shift keying and quadrature-amplitude modulation. Moreover, in the digital domain, we can equalize all linear transmission impairments such as group-velocity dispersion and polarization-mode dispersion of transmission fibers, because coherent detection preserves the phase information of the optical signal. This paper reviews the history of research and development related to coherent optical communications and describes the principle of coherent detection, including its quantum-noise characteristics. In addition, it discusses the role of digital signal processing in mitigating linear transmission impairments, estimating the carrier phase, and tracking the state of polarization of the signal in coherent receivers.
618 citations
TL;DR: A transmission system with adjustable data rate for single-carrier coherent optical transmission is proposed, which enables high-speed transmission close to the Shannon limit, and it is experimentally demonstrated that the optical transmission of probabilistically shaped 64-QAM signals outperforms the transmission reach of regular 16- QAM and regular 64-ZAM signals.
Abstract: A transmission system with adjustable data rate for single-carrier coherent optical transmission is proposed, which enables high-speed transmission close to the Shannon limit. The proposed system is based on probabilistically shaped 64-QAM modulation formats. Adjustable shaping is combined with a fixed-QAM modulation and a fixed forward-error correction code to realize a system with adjustable net data rate that can operate over a large reach range. At the transmitter, an adjustable distribution matcher performs the shaping. At the receiver, an inverse distribution matcher is used. Probabilistic shaping is implemented into a coherent optical transmission system for 64-QAM at 32 Gbaud to realize adjustable operation modes for net data rates ranging from 200 to 300 Gb/s. It is experimentally demonstrated that the optical transmission of probabilistically shaped 64-QAM signals outperforms the transmission reach of regular 16-QAM and regular 64-QAM signals by more than 40% in the transmission reach.
564 citations
TL;DR: A near maximum likelihood detector for uplink multiuser massive MIMO systems is proposed where each antenna is connected to a pair of one-bit ADCs, i.e., one for each real and imaginary component of the baseband signal.
Abstract: In massive multiple-input multiple-output (MIMO) systems, it may not be power efficient to have a pair of high-resolution analog-to-digital converters (ADCs) for each antenna element. In this paper, a near maximum likelihood (nML) detector for uplink multiuser massive MIMO systems is proposed where each antenna is connected to a pair of one-bit ADCs, i.e., one for each real and imaginary component of the baseband signal. The exhaustive search over all the possible transmitted vectors required in the original maximum likelihood (ML) detection problem is relaxed to formulate an ML estimation problem. Then, the ML estimation problem is converted into a convex optimization problem which can be efficiently solved. Using the solution, the base station can perform simple symbol-by-symbol detection for the transmitted signals from multiple users. To further improve detection performance, we also develop a two-stage nML detector that exploits the structures of both the original ML and the proposed (one-stage) nML detectors. Numerical results show that the proposed nML detectors are efficient enough to simultaneously support multiple uplink users adopting higher-order constellations, e.g., 16 quadrature amplitude modulation. Since our detectors exploit the channel state information as part of the detection, an ML channel estimation technique with one-bit ADCs that shares the same structure with our proposed nML detector is also developed. The proposed detectors and channel estimator provide a complete low power solution for the uplink of a massive MIMO system.
491 citations
TL;DR: In this paper, the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR, was investigated.
Abstract: Different aspects of probabilistic shaping for a multispan optical communication system are studied. First, a numerical analysis of the additive white Gaussian noise (AWGN) channel investigates the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR. It is shown that if a small penalty of at most 0.1 dB SNR to the full shaping gain is acceptable, just two shaped PMFs are required per quadrature amplitude modulation (QAM) over a large SNR range. For a multispan wavelength division multiplexing optical fiber system with 64QAM input, it is shown that just one PMF is required to achieve large gains over uniform input for distances from 1400 to 3000 km. Using recently developed theoretical models that extend the Gaussian noise (GN) model and full-field split-step simulations, we illustrate the ramifications of probabilistic shaping on the effective SNR after fiber propagation. Our results show that, for a fixed average optical launch power, a shaping gain is obtained for the noise contributions from fiber amplifiers and modulation-independent nonlinear interference (NLI), whereas shaping simultaneously causes a penalty as it leads to an increased NLI. However, this nonlinear shaping loss is found to have a relatively minor impact, and optimizing the shaped PMF with a modulation-dependent GN model confirms that the PMF found for AWGN is also a good choice for a multi-span fiber system.
278 citations
TL;DR: The performance of OFDM-IM is studied in terms of the achievable rate assuming an M-ary constellation and that channel state information is available at the receiver, and an interleaved grouping method is proposed for the use of subcarriers.
Abstract: Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a recently developed transmission technique that extends the principle of spatial modulation to OFDM subcarriers. In this paper, the performance of OFDM-IM is studied in terms of the achievable rate assuming an $M$ -ary constellation and that channel state information is available at the receiver. A closed-form lower bound is derived, based on which an interleaved grouping method is proposed for the use of subcarriers. In comparison with the existing grouping method, the proposed one can better benefit from the diversity effects over frequency-selective fading channels, especially when the spacing of any two subcarriers within a subcarrier group is larger than the coherence bandwidth. Through numerical results, it is revealed that OFDM-IM with interleaved grouping outperforms classical OFDM for small $M$ and certain ranges of signal-to-noise ratio. Finally, the effects of modulation types on the performance of OFDM-IM are studied. It is found that the superiority of OFDM-IM over classical OFDM is greater for phase-shift keying than for quadrature amplitude modulation.
241 citations
TL;DR: In this paper, the authors present a direct-conversion quadrature transmitter and receiver chipset at 240 GHz, which is implemented in a 0.13-μm SiGe bipolar-CMOS technology.
Abstract: This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz. It is implemented in a 0.13- $\mu{\hbox{m}}$ SiGe bipolar-CMOS technology. A wideband frequency multiplier ( $\times$ 16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens makes this chipset suited for applications requiring fixed and tunable LO. The chipset is packaged in a low-cost FR4 printed circuit board resulting in a complete solution with compact form-factor. At 236 GHz, the effective-isotropic-radiated-power is 21.86 dBm and the minimum single-sideband noise figure is 15 dB. The usable RF bandwidth for this chipset is 65 GHz and the 6-dB bandwidth is 17 GHz. At the system level, we demonstrate a high data-rate communication system where an external modem is operated in its two IF-bandwidth modes (250 MHz and 1 GHz). For the quadrature phase-shift keying modulation scheme, the measured data rate is 2.73 Gb/s (modem 1-GHz IF) with bit-error rate of ${\hbox{10}}^{-9}$ for a 15-cm link. The estimated data rate over the 17-GHz RF bandwidth is, hence, 23.025 Gb/s. Also, higher order modulation schemes like 16 quadrature amplitude modulation (QAM) with a data rate of 0.677 Gb/s and 64-QAM with a data rate of 1.0154 Gb/s (modem 250-MHz IF) is demonstrated. A second application demonstrator is presented where the wide tunable RF bandwidth of the chipset is used for material characterization. It is used to characterize an FR4 material (DE104) over the 215–260-GHz range.
128 citations
TL;DR: This paper introduces generalized space and frequency IM, where the indexes of active transmit antennas and subcarriers convey information bits and derives the achievable rate expression, and proposes a Gibbs-sampling-based detection algorithm for GSIM.
Abstract: Unlike in conventional modulation where information bits are conveyed only through symbols from modulation alphabets defined in the complex plane [e.g., quadrature amplitude modulation (QAM) and phase shift keying (PSK)], in index modulation (IM), additional information bits are conveyed through indexes of certain transmit entities that get involved in the transmission. Transmit antennas in multiantenna systems and subcarriers in multicarrier systems are examples of such transmit entities that can be used to convey additional information bits through indexing. In this paper, we introduce generalized space and frequency IM , where the indexes of active transmit antennas and subcarriers convey information bits. We first introduce IM in the spatial domain, which is referred to as generalized spatial IM (GSIM). For GSIM, where bits are indexed only in the spatial domain, we derive the expression for achievable rate and easy-to-compute upper and lower bounds on this rate. We show that the achievable rate in GSIM can be more than that in spatial multiplexing and analytically establish the condition under which this can happen. It is noted that GSIM achieves this higher rate using fewer transmit radio-frequency (RF) chains compared with spatial multiplexing. We also propose a Gibbs-sampling-based detection algorithm for GSIM and show that GSIM can achieve better bit error rate (BER) performance than spatial multiplexing. For generalized space–frequency IM (GSFIM), where bits are encoded through indexing in both active antennas and subcarriers, we derive the achievable rate expression. Numerical results show that GSFIM can achieve higher rates compared with conventional multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM). Moreover, BER results show the potential for GSFIM performing better than MIMO-OFDM.
128 citations
01 Dec 2016
TL;DR: A deep learning-based AMC method that employs Spectral Correlation Function (SCF) and Deep Belief Network (DBN) is proposed for pattern recognition and classification that achieves high accuracy in modulation detection and classification even in the presence of environment noise.
Abstract: Automated Modulation Classification (AMC) has been applied in various emerging areas such as cognitive radio (CR). In our paper, we propose a deep learning-based AMC method that employs Spectral Correlation Function (SCF). In our proposed method, one deep learning technology, Deep Belief Network (DBN), is applied for pattern recognition and classification. By using noise-resilient SCF signatures and DBN that is effective in learning complex patterns, we achieve high accuracy in modulation detection and classification even in the presence of environment noise. Our simulation results illustrate the efficiency of our proposed method in classifying 4FSK, 16QAM, BPSK, QPSK, and OFDM modulation techniques in various environments.
125 citations
TL;DR: This paper surveys the suitable modulation techniques for Li-Fi including those which explore time,frequency and colour domains including thoseWhich are considered to offer a practical solution forLi-Fi.
Abstract: Modulation techniques for light fidelity(Li-Fi) are reviewed in this paper.Li-Fi is the fully networked solution for multiple users that combines communication and illumination simultaneously.Light emitting diodes(LEDs) are used in Li-Fi as visible light transmitters,therefore,only intensity modulated direct detected modulation techniques can be achieved.Single carrier modulation techniques are straightforward to be used in Li-Fi,however,computationally complex equalization processes are required in frequency selective Li-Fi channels.On the other hand,multicarrier modulation techniques offer a viable solution for Li-Fi in terms of power,spectral and computational efficiency.In particular,orthogonal frequency division multiplexing(OFDM) based modulation techniques offer a practical solution for Li-Fi,especially when direct current(DC) wander,and adaptive bit and power loading techniques are considered.Li-Fi modulation techniques need to also satisfy illumination requirements.Flickering avoidance and dimming control are considered in the variant modulation techniques presented.This paper surveys the suitable modulation techniques for Li-Fi including those which explore time,frequency and colour domains.
109 citations
TL;DR: In this paper, a probabilistic shaping scheme for optical WDM systems, where nonlinear interference noise depends on the input optical signal power distribution, is proposed, and an example system is developed for a transmission distance around $3280$ Âkm.
Abstract: This work proposes a probabilistic shaping scheme for optical WDM systems, where nonlinear interference noise depends on the input optical signal power distribution. With $16$ -QAM, a white Gaussian channel analysis shows that the shaped constellation is able to achieve a reach improvement of up to $7\%$ , while split-step Fourier method simulations suggest that even higher gains are possible in practice. An example system is developed for a transmission distance around $3280$ km. A constellation mapping and a low-density parity-check code are developed for this regime to show a reach improvement of $7.1\%$ . These shaping schemes can also be extended to $64$ -QAM, where a reach improvement of over $10\%$ is expected.
108 citations
TL;DR: ATSC 3.0 will provide a considerable increase in the maximum transmission capacity when using the high-order NUCs such as 1024QAM and 4096QAM, which will represent a major milestone for terrestrial broadcasting since the highest order constellation currently available is uniform 256QAM.
Abstract: In this paper, we summarize and expound upon the choices made for the bit-interleaved coded modulation (BICM) part of the next-generation terrestrial broadcast standard known as ATSC 3.0. The structure of the ATSC 3.0 BICM consists of a forward error correcting code, bit interleaver, and constellation mapper. In order to achieve high efficiency over a wide range of reception conditions and carrier-to-noise (C/N) ratio values, several notable new elements have been standardized. First, 24 original low-density parity check (LDPC) codes have been designed, with coding rates from 2/15 (0.13) up to 13/15 (0.87) for two code sizes: 16 200 bits and 64 800 bits. Two different LDPC structures have been adopted; one structure more suited to medium and high coding rates and another structure suited to very low coding rates. Second, in addition to quaternary phase shift keying, non-uniform constellations (NUCs) have been chosen for constellation sizes from 16QAM to 4096QAM to bridge the gap to the Shannon theoretical limit. Two different types of NUCs have been proposed: 1-D NUCs for 1024- and 4096-point constellations, and 2-D-NUCs for 16-, 64-, and 256-point constellations. 2-D-NUCs achieve a better performance than 1-D-NUCs but with a higher complexity since they cannot be separated into two independent I/Q components. NUCs have been optimized for each coding rate for the 64 800 bits LPDCs. The same constellations are used for 16 200 bits LDPCs, although they have been limited up to 256QAM. Finally, a bit interleaver, optimized for each NUC/coding rate combination, has been designed to maximize the performance. The result is a BICM that provides the largest operating range (more than 30 dB, with the most robust mode operating below -5 dB C/N) and the highest spectral efficiency compared to any digital terrestrial broadcast system today, outperforming the current state-of-the-art DVB-T2 standard BICM by as much as 1 dB in some cases. ATSC 3.0 will also provide a considerable increase in the maximum transmission capacity when using the high-order NUCs such as 1024QAM and 4096QAM, which will represent a major milestone for terrestrial broadcasting since the highest order constellation currently available is uniform 256QAM. This paper describes the coding, modulation, and bit interleaving modules of the BICM block of ATSC 3.0 and compares its performance with other DTT standards such as ATSC A/53 and DVB-T2.
TL;DR: In this paper, a single-chip 110-170-GHz ( $D$ -band) direct conversion in-phase/quadrature-phase (I/Q) transmitter (TX) and receiver (RX) monolithic microwave integrated circuits (MMICs), realized in a 250-nm indium phosphide (InP) double heterojunction bipolar transistor (DHBT) technology, is presented.
Abstract: This paper presents design and characterization of single-chip 110–170-GHz ( $D$ -band) direct conversion in-phase/quadrature-phase (I/Q) transmitter (TX) and receiver (RX) monolithic microwave integrated circuits (MMICs), realized in a 250-nm indium phosphide (InP) double heterojunction bipolar transistor (DHBT) technology. The chipset is suitable for low-power ultrahigh-speed wireless communication and can be used in both homodyne and heterodyne architectures. The TX consists of an I/Q modulator, a frequency tripler, and a broadband three-stage power amplifier. It has single sideband (SSB) conversion gain of 25 dB and saturated output power of 9 dBm. The RX includes an I/Q demodulator with $D$ -band amplifier and $\times$ 3 multiplier chain at the LO port. The RX provides a conversion gain of 26 dB and has noise figure of 9 dB. A 48-Gbit/s direct quadrature phase-shift keying (QPSK) data transmission using a 144-GHz millimeter-wave carrier signal is demonstrated with a bit error rate (BER) of 2.3 $\,\times \hbox{ 10} ^{-3}$ and energy efficiency of 7.44 pJ/bit. An 18-Gbit/s 64-quadrature amplitude modulation (QAM) signal was transmitted in heterodyne mode with measured TX-to-RX error vector magnitude (EVM) of less than 6.8% and spectrum efficiency of 3.6 bit/s/Hz. The TX and RX have dc power consumption of 165 and 192 mW, respectively. The chip area of each TX and RX circuit is 1.3 $\,\times\,$ 0.9 $\hbox{mm}^{2}$ .
TL;DR: In this paper, a probabilistic shaping method for increasing the transmission reach of a WDM optical communication system employing quadrature amplitude modulation (QAM) was proposed. But the performance of the proposed 1024QAM shaped system is validated on all 5 channels of the WDM signal for selected distances and rates.
Abstract: In this paper, probabilistic shaping is numerically and experimentally investigated for increasing the transmission reach of wavelength division multiplexed (WDM) optical communication system employing quadrature amplitude modulation (QAM). An optimized probability mass function (PMF) of the QAM symbols is first found from a modified Blahut-Arimoto algorithm for the optical channel. A turbo coded bit interleaved coded modulation system is then applied, which relies on many-to-one labeling to achieve the desired PMF, thereby achieving shaping gain. Pilot symbols at rate at most 2% are used for synchronization and equalization, making it possible to receive input constellations as large as 1024QAM. The system is evaluated experimentally on a 10 GBaud, 5 channels WDM setup. The maximum system reach is increased w.r.t. standard 1024QAM by 20% at input data rate of 4.65 bits/symbol and up to 75% at 5.46 bits/symbol. It is shown that rate adaptation does not require changing of the modulation format. The performance of the proposed 1024QAM shaped system is validated on all 5 channels of the WDM signal for selected distances and rates. Finally, it was shown via EXIT charts and BER analysis that iterative demapping, while generally beneficial to the system, is not a requirement for achieving the shaping gain.
TL;DR: It is shown via EXIT charts and BER analysis that iterative demapping, while generally beneficial to the system, is not a requirement for achieving the shaping gain, and that rate adaptation does not require changing of the modulation format.
Abstract: In this paper, probabilistic shaping is numerically and experimentally investigated for increasing the transmission reach of wavelength division multiplexed (WDM) optical communication systems employing quadrature amplitude modulation (QAM). An optimized probability mass function (PMF) of the QAM symbols is first found from a modified Blahut–Arimoto algorithm for the optical channel. A turbo coded bit interleaved coded modulation system is then applied, which relies on many-to-one labeling to achieve the desired PMF, thereby achieving shaping gains. Pilot symbols at rate at most 2% are used for synchronization and equalization, making it possible to receive input constellations as large as 1024QAM. The system is evaluated experimentally on a 10 GBd, 5 channels WDM setup. The maximum system reach is increased w.r.t. standard 1024QAM by 20% at input data rate of 4.65 bits/symbol and up to 75% at 5.46 bits/symbol. It is shown that rate adaptation does not require changing of the modulation format. The performance of the proposed 1024QAM shaped system is validated on all 5 channels of the WDM signal for selected distances and rates. Finally, it is shown via EXIT charts and BER analysis that iterative demapping, while generally beneficial to the system, is not a requirement for achieving the shaping gain.
TL;DR: This paper derives a closed-form expression for the bit error rate (BER) of the FSO link in such conditions when the on-off keying (OOK) modulation is employed and when the fluctuations of the received signal are modeled by Gamma- Gamma distribution.
Abstract: Free-space optical (FSO) communication is known for its various impairments such as atmospheric turbulence and misalignment fading. In this paper, we study the performance of an FSO link operating under combined path loss and atmospheric and misalignment fadings. We derive a closed-form expression for the bit error rate (BER) of the FSO link in such conditions when the on-off keying (OOK) modulation is employed and when the fluctuations of the received signal are modeled by Gamma- Gamma distribution. In addition, we evaluate the effects of the combined fadings on the outage probability of the FSO link for different strengths of turbulence and pointing errors. Furthermore, we investigate the advantages of combining radio frequency (RF) with FSO to form hybrid FSO/ RF systems. The RF link is based on 16 quadrature amplitude modulation (16-QAM) and on Rician channel fading. We study the performance of the hybrid FSO/RF system in terms of outage probability and BER and find that the hybrid FSO/RF system can overcome the weaknesses of FSO links, which are sensitive to atmospheric variations and misalignment fading.
TL;DR: In this article, the authors investigate upper bounds for single-channel and multi-channel digital back-propagation (BP) in fully loaded wavelength-division multiplexed systems.
Abstract: We investigate upper bounds for single-channel and multi-channel digital back-propagation (BP) in fully loaded wavelength-division multiplexed systems. Using the time-domain model for nonlinear interference noise, we expand previous estimates of BP gains to accurately cover a wide range of system configurations, including a variety of modulation formats from quadrature phase-shift keying to 256-ary quadrature amplitude modulation. In typical scenarios, the potential benefit of single-channel BP is limited to $\sim 0.5$ dB in terms of the peak signal-to-noise ratio, and to $\sim 1$ and $\sim 1.2$ dB in the case of joint three- and five-channel BP. The additional gain from increasing the number of jointly back-propagated channels beyond five is limited to $\sim 0.1$ dB per additional back-propagated channel. We also study the role of BP for receivers that separately compensate for nonlinear phase and polarization rotation noise and show that while the additional gain provided by BP does not change significantly in long-haul systems, it holds the promise of being notably higher in short-reach ultra-high-capacity systems.
TL;DR: Both theoretical analysis and simulation results confirm the promising benefits of the new DCSK modulation scheme, which employs I/Q channels to send these two signals in a parallel and simultaneous manner, making the system easily extendable to multi-carriers.
Abstract: A novel non-coherent multi-level differential chaos shift keying (DCSK) modulation scheme is proposed in this paper. This new scheme is based on both the transmitted-reference technique and $M$ -ary orthogonal modulation, where each data-bearing signal is chosen from a set of orthogonal chaotic wavelets constructed by a reference signal. Thanks to this signaling design, the new scheme can achieve a higher attainable data rate, lower energy loss in reference transmission, increased bandwidth efficiency, better data security and better bit error rate (BER) performance as compared to the conventional DCSK. Unlike other DCSK-based systems that separate the reference and data-bearing signals using the TDMA scheme, this new system employs I/Q channels to send these two signals in a parallel and simultaneous manner, making the system easily extendable to multi-carriers. This transmission mechanism not only can further increase data rate but also can remove all radio frequency delay lines from detectors. Analytical BER expressions of the proposed system are derived for both additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Relevant simulation results are given and compared to non-coherent binary/ $M$ -ary DCSK systems. In addition, the impacts of various system parameters on noise performance are discussed. Both theoretical analysis and simulation results confirm the promising benefits of the new design.
TL;DR: It is shown that the proposed FBMC-QAM system satisfies the suggested orthogonality conditions and can use the multiple-input multiple-output transmission schemes as the conventional orthogonal frequency division multiplexing (OFDM) systems.
Abstract: A filter-bank multicarrier–quadrature amplitude modulation (FBMC-QAM) system with two prototype filters for transmitting QAM symbol is proposed, and the orthogonality conditions for the FBMC-QAM system without the intrinsic interference is derived. The proposed transmitter performs the individual filtering for the even and odd-numbered sub-carrier symbols, respectively. In order to satisfy the derived orthogonality conditions, we perform a sub-block wise reverse ordering procedure for the outputs of the odd-numbered sub-carrier filter. Also, this paper shows that the proposed FBMC-QAM system satisfies the suggested orthogonality conditions and can use the multiple-input multiple-output transmission schemes as the conventional orthogonal frequency division multiplexing (OFDM) systems. The signal-to-interference power ratio and the bit error rate (BER) for the proposed FBMC-QAM system are evaluated. Numerical results show that the proposed FBMC-QAM system has almost the same BER performance compared with the FBMC-OQAM and OFDM systems.
TL;DR: Simulation results show that the proposed approximation for the SEP of hexagonal QAM in additive white Gaussian noise is very accurate for all the best-known QAM constellations constructed from the hexagonal lattice, including triangular QAM, for both high and low signal-to-noise ratio.
Abstract: This letter studies the symbol error probability (SEP) of quadrature-amplitude modulation (QAM) signals constructed from the hexagonal lattice, known as hexagonal QAM or triangular QAM. In particular, we propose a simple and accurate approximation for the SEP of hexagonal QAM in additive white Gaussian noise. Simulation results show that the proposed approximation is very accurate for all the best-known QAM constellations constructed from the hexagonal lattice, including triangular QAM, for both high and low signal-to-noise ratio. In addition, the proposed approximation is suitable for the accurate estimation of the SEP of hexagonal QAM in slow-fading channels, such as Rayleigh fading channels.
TL;DR: Probabilistic shaping of quadrature amplitude modulation (QAM) is used to enhance the sensitivity of an optical communication system as discussed by the authors, which is demonstrated in back-to-back experiments by the shaping of 16QAM and 64QAM.
Abstract: Probabilistic shaping of quadrature amplitude modulation (QAM) is used to enhance the sensitivity of an optical communication system. Sensitivity gains of 0.43 and 0.8 dB are demonstrated in back-to-back experiments by the shaping of 16QAM and 64QAM, respectively. Furthermore, numerical simulations are used to prove the robustness of probabilistic shaping to a mismatch between the constellation used and the signal-to-noise ratio (SNR) of the channel. It is found that, accepting a 0.1-dB SNR penalty, only four shaping distributions are required to support these gains for 64QAM.
01 Oct 2016
TL;DR: This paper investigates application of DNN technique to automatic classification of modulation classes for digitally modulated signals and shows that the proposed method brings dramatic performance improvement over the existing classifier especially for high Doppler fading channels.
Abstract: Deep neural network (DNN) has recently received much attention due to its superior performance in classifying data with complex structure. In this paper, we investigate application of DNN technique to automatic classification of modulation classes for digitally modulated signals. First, we select twenty one statistical features which exhibit good separation in empirical distributions for all modulation formats considered (i.e., BPSK, QPSK, 8PSK, 16QAM, and 64QAM). These features are extracted from the received signal samples and used as the input to the fully connected DNN with three hidden layer. The training data containing 25,000 feature vectors is generated by the computer simulation under both additive Gaussian white noise (AWGN) and Rician fading channels. Our test results show that the proposed method brings dramatic performance improvement over the existing classifier especially for high Doppler fading channels.
TL;DR: A support vector machine (SVM)-based classification nonlinear equalizer (NLE) is demonstrated, for the first time, in coherent optical orthogonal frequency-division multiplexing (CO-OFDM).
Abstract: A support vector machine (SVM)-based classification nonlinear equalizer (NLE) is demonstrated, for the first time, in coherent optical orthogonal frequency-division multiplexing (CO-OFDM). For a 40-Gb/s 16 quadrature amplitude modulated (16QAM) CO-OFDM system at 400 km of transmission, SVM-NLE reduces the fiber-induced nonlinearity penalty by about 1 dB in comparison to the benchmark artificial-neural-network (ANN)-based and inverse-Volterra-series-transfer-function-based NLEs.
TL;DR: A high-spectral-efficiency, large-capacity, featured free-space-optical (FSO) transmission system by using low-density, parity-check (LDPC) coded quadrature phase shift keying (QPSK) combined with orbital angular momentum (OAM) multiplexing with excellent agreement of experimental, numerical, and analytical results is found.
Abstract: We experimentally demonstrate a high-spectral-efficiency, large-capacity, featured free-space-optical (FSO) transmission system by using low-density, parity-check (LDPC) coded quadrature phase shift keying (QPSK) combined with orbital angular momentum (OAM) multiplexing. The strong atmospheric turbulence channel is emulated by two spatial light modulators on which four randomly generated azimuthal phase patterns yielding the Andrews spectrum are recorded. The validity of such an approach is verified by reproducing the intensity distribution and irradiance correlation function (ICF) from the full-scale simulator. Excellent agreement of experimental, numerical, and analytical results is found. To reduce the phase distortion induced by the turbulence emulator, the inexpensive wavefront sensorless adaptive optics (AO) is used. To deal with remaining channel impairments, a large-girth LDPC code is used. To further improve the aggregate data rate, the OAM multiplexing is combined with WDM, and 500 Gb/s optical transmission over the strong atmospheric turbulence channels is demonstrated.
TL;DR: The Q-SCPA combines in-phase (I) and quadrature (Q) signals on a shared capacitor array that results in a 3 dB signal loss, and utilizes a class-G dual-supply architecture to improve efficiency at backoff.
Abstract: This paper presents an all-digital class-G quadrature switched-capacitor power amplifier (Q-SCPA) implemented in 65 nm CMOS. It combines in-phase ( I ) and quadrature ( Q ) signals on a shared capacitor array. The I / Q signals are digitally weighted and combined in the charge domain. Quadrature summation results in a 3 dB signal loss; Hence the Q-SCPA utilizes a class-G dual-supply architecture to improve efficiency at backoff. Unlike polar/EER counterparts, the Q-SCPA requires no wideband phase modulator or delay matching circuitry. The Q-SCPA delivers a peak output power of 20.5 dBm with a peak PAE of 20%. It is measured with a 10 MHz, 64 QAM LTE signal, and achieves an ACLR of $ , with an ${\bf EVM} 4%-rms.
TL;DR: This work uses an information theoretic approach based on the mutual information and the generalised mutual information to characterise a state-of-the-art dual polarisation m-ary quadrature amplitude modulation transceiver and applies this methodology to a 15-carrier super-channel to achieve the highest throughput ever recorded using a single coherent receiver.
Abstract: Optical fibre underpins the global communications infrastructure and has experienced an astonishing evolution over the past four decades, with current commercial systems transmitting data rates in excess of 10 Tb/s over a single fibre core. The continuation of this dramatic growth in throughput has become constrained due to a power dependent nonlinear distortion arising from a phenomenon known as the Kerr effect. The mitigation of fibre nonlinearities is an area of intense research. However, even in the absence of nonlinear distortion, the practical limit on the transmission throughput of a single fibre core is dominated by the finite signal-to-noise ratio (SNR) afforded by current state-of-the-art coherent optical transceivers. Therefore, the key to maximising the number of information bits that can be reliably transmitted over a fibre channel hinges on the simultaneous optimisation of the modulation format and code rate, based on the SNR achieved at the receiver. In this work, we use an information theoretic approach based on the mutual information and the generalised mutual information to characterise a state-of-the-art dual polarisation m-ary quadrature amplitude modulation transceiver and subsequently apply this methodology to a 15-carrier super-channel to achieve the highest throughput (1.125 Tb/s) ever recorded using a single coherent receiver.
TL;DR: In this paper, the authors achieved the field trial demonstration of 80 Gb/s polarization-division-multiplexing quadrature phase shift keying modulated W-band mm-wave signal delivery over a 300m Cassegrain antenna-based (CA-based) 4 × 4 MIMO wireless link.
Abstract: High-speed long-haul wireless transmission links are required to meet the demand of mobile backhauling and emergency communications. We experimentally demonstrated ultra-high-speed 432-Gb/s polarization-division-multiplexing 16-ary quadrature amplitude modulation modulated W-band millimeter-wave (mm-wave) signal delivery over a 2-m horn antenna-based (HA-based) 4 × 4 multiple-input multiple-output (MIMO) wireless link, enabled by photonic mm-wave generation and optical/antenna polarization multiplexing. We further achieved the field trial demonstration of 80-Gb/s polarization-division-multiplexing quadrature phase shift keying modulated W-band mm-wave signal delivery over a 300-m Cassegrain antenna-based (CA-based) 4 × 4 MIMO wireless link, adopting photonic mm-wave generation, multi-band multiplexing, and optical/antenna polarization multiplexing. To the best of our knowledge, 80 Gb/s or 74.7 Gb/s after removing 7% forward-error-correction overhead is a record for W-band wireless signal delivery over a few hundred meters.
TL;DR: It is shown in this paper that the phase of the channel has major impact on the performance of spatial multiplexing MIMO systems such as SM and QSM systems.
Abstract: This paper analyzes the performance of the recently proposed quadrature spatial modulation (QSM) multiple-input-multiple-output (MIMO) system over Nakagami-m fading channel. In the analysis, the general distribution of the Nakagami-m channel phase is considered. In the literature, performance analysis of spatial modulation (SM) over Nakagami-m channel with uniform phase is conducted. However, apart from the very special case of m = 1, where Nakagami-m fading corresponds to Rayleigh fading, the phase of the Nakagami-m distribution is not uniformly distributed. It is shown in this paper that the phase of the channel has major impact on the performance of spatial multiplexing MIMO systems such as SM and QSM systems. A general upper bound expression for the average bit error ratio (ABER) performance of QSM is derived, and the impact of different channel parameters is studied. Monte Carlo simulation results are provided to corroborate the exactness of the derived analysis.
TL;DR: The experimental results show that the adaptive feedback correction scheme can efficiently compensate for the atmospheric turbulence induced distortions, i.e., reducing power fluctuation of multicasted OAM channels, suppressing inter-channel crosstalk, and improving the bit-error rate (BER) performance.
Abstract: By using an adaptive feedback correction technique, we experimentally demonstrate turbulence compensation for free-space four-fold and eight-fold 16-ary quadrature amplitude modulation (16-QAM) carrying orbital angular momentum (OAM) multicasting links. The performance of multicasted OAM beams through emulated atmospheric turbulence and adaptive optics assisted compensation loop is investigated. The experimental results show that the scheme can efficiently compensate for the atmospheric turbulence induced distortions, i.e., reducing power fluctuation of multicasted OAM channels, suppressing inter-channel crosstalk, and improving the bit-error rate (BER) performance.
TL;DR: A chaos IQ-encryption-based optimal frame transmission technique in an orthogonal frequency-division multiple access-based passive optical network (OFDMA-PON) is proposed to enhance the physical layer security.
Abstract: For joint peak-to-average power ratio (PAPR) reduction and physical layer security enhancement, we propose a chaos IQ-encryption-based optimal frame transmission technique in an orthogonal frequency-division multiple access-based passive optical network (OFDMA-PON). The chaos IQ-encryption technique is utilized to enhance the physical layer security. In encrypting, the in-phase (I) and quadrature-phase (Q) parts of the quadrature amplitude modulation (QAM) symbols are coded with two phase sequences separately, which are generated using a 2-D logistic map. The encrypted OFDM symbols comprise an OFDM frame, and the frame with the minimum PAPR is transmitted to the optical network unit side. Thus, the transmitted OFDM signal is of a joint low PAPR and high physical layer security. In the demonstration, an 11.32-Gb/s encrypted 16 QAM OFDM signal has been experimentally transmitted over 25-km standard single mode fiber in an intensity-modulation/direct-detection OFDMA-PON.
TL;DR: Simulation results and analysis show that the proposed hybrid PTS-TR scheme could provide better PAPR reduction than conventional PTS and TR schemes in FBMC/OQAM systems.
Abstract: The filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is being studied by many researchers as a key enabler for the fifth-generation air interface. In this paper, a hybrid peak-to-average power ratio (PAPR) reduction scheme is proposed for FBMC/OQAM signals by utilizing multi data block partial transmit sequence (PTS) and tone reservation (TR). In the hybrid PTS-TR scheme, the data blocks signal is divided into several segments, and the number of data blocks in each segment is determined by the overlapping factor. In each segment, we select the optimal data block to transmit and jointly consider the adjacent overlapped data block to achieve minimum signal power. Then, the peak reduction tones are utilized to cancel the peaks of the segment FBMC/OQAM signals. Simulation results and analysis show that the proposed hybrid PTS-TR scheme could provide better PAPR reduction than conventional PTS and TR schemes in FBMC/OQAM systems. Furthermore, we propose another multi data block hybrid PTS-TR scheme by exploiting the adjacent multi overlapped data blocks, called as the multi hybrid (M-hybrid) scheme. Simulation results show that the M-hybrid scheme can achieve about 0.2-dB PAPR performance better than the hybrid PTS-TR scheme.