Amplitude And Phase Shift Keying Research Articles

Amplitude-Constrained Constellation and Reflection Pattern Designs for Directional Backscatter Communications Using Programmable Metasurface

The large scale reflector array of programmable metasurfaces is capable of increasing the power efficiency of backscatter communications via passive beamforming and thus has the potential to revolutionize the low-data-rate nature of backscatter communications. In this paper, we propose to design the power-efficient higher-order constellation and reflection pattern under the amplitude constraint brought by backscatter communications. For the constellation design, we adopt the amplitude and phase-shift keying (APSK) constellation and optimize the parameters of APSK such as ring number, ring radius, and inter-ring phase difference. Specifically, we derive closed-form solutions to the optimal ring radius and inter-ring phase difference for an arbitrary modulation order in the decomposed subproblems. For the reflection pattern design, we propose to optimize the passive beamforming vector by solving a multi-objective optimization problem that maximizes reflection power and guarantees beam homogenization within the interested angle range. To solve the problem, we propose a constant-modulus power iteration method, which is proven to be monotonically increasing, to maximize the objective function in each iteration. Numerical results show that the proposed APSK constellation design and reflection pattern design outperform the existing modulation and beam pattern designs in programmable metasurface enabled backscatter communications.

Development of Transmitter and Receiver With Set Partitioning 64APSK Coded Modulation Designed on Basis of Channel Capacity

In this paper, we present a prototype transmitter and receiver with set partitioning (SP)-64 amplitude and phase shift keying (APSK) coded modulation we developed for expanding satellite transmission capacity. SP-multi-level coded modulation is a transmission scheme that can improve noise immunity by properly combining a modulation scheme, bit allocation, and error-correction codes. We designed SP-64APSK coded modulation on the basis of channel capacity for expanding satellite transmission capacity. We confirmed that it has higher robustness to additive white Gaussian noise (AWGN) than DVB-S2X’s 64APSK modulation with Gray mapping through computer simulation. We also developed a prototype transmitter and receiver to implement our SP-64APSK coded modulation and evaluated its transmission performances in an AWGN channel and in a non-linear channel simulating 12-GHz-band satellite transponder characteristics. We describe the method of designing our SP-64APSK coded modulation through computer simulation, the modulation/demodulation process, and transmission performances of the prototype transmitter and receiver. We also indicate that 8K ultra-high definition television (UHDTV) with an encoded bit rate of 150 Mbps can be transmitted using the prototype within 34.5 MHz, which is the bandwidth of a single transponder for satellite broadcasting in Japan.

Performance analysis ofM‐ary amplitude and phase shift keying uncoded space‐time labeling diversity with three transmit antennas in nonlinear Rician channels

AbstractThis article investigates uncoded space‐time labeling diversity (USTLD) with three transmit antennas schemes based on amplitude and phase shift keying (APSK) modulation. The proposed USTLD schemes are DVB‐S2 and DVB‐S2X standards compatible and provide robustness against nonlinear distortion for both Rician frequency‐flat fast and quasi‐static fading channels. Numerical analysis of the proposed schemes is derived based on pairwise error probability. The analytical results are validated by Monte Carlo simulations, which converge accurately at high signal‐to‐noise ratio. Furthermore, by adapting constellation structure between square quadratic amplitude modulations and concentric rings of APSK modulations, the author proposes mapper design for 16‐APSK, 32‐APSK, and 64‐APSK modulations for USTLD using heuristic algorithm. Finally, the proposed USTLD schemes show bit error rate (BER) improvement over the existing two transmit USTLD scheme with error performance gain of 1.2 and 2.8 dB at a BER offor 16‐APSK and 64‐APSK USTLD scheme, respectively.

64APSK constellation scheme for short-reach DMT with ISDD enabled SFO compensation

Sampling frequency offset between digital-to-analog converter (DAC) and analog-to-digital converter (ADC) always exists in asynchronous optical discrete multi-tone (DMT) systems. The overall bit error rate (BER) performance may be seriously deteriorated due to SFO-induced phase rotation. Inter-symbol differential encoding/detection (ISDE/ISDD) with decision-aided residual phase compensation (RPC) has been employed to compensate SFO. No extra training sequences or pilot subcarriers are required for SFO compensation. However, the increased phase noise induced by ISDD is still a problem and may degrade the BER performance of the DMT receiver, especially for high-order modulation formats. In this work, we propose the use of amplitude and phase shift keying (APSK) constellation scheme to against the ISDD-induced phase noise and then improve the BER performance. In our simulations, the 64QAM and two types of 64APSK modulation formats for DMT are studied in both additive white Gaussian noise (AWGN) channel and intensity-modulation/direct-detection optical fiber transmission system. The simulated results exhibit that the employed two 64APSK constellation schemes outperform the conventional 64QAM modulation format in the presence of ISDD-induced phase noise. By using the proposed 64APSK constellation scheme, the SNR performance can be improved by up to 3dB when the BER is 1E-3 in AWGN channel. Besides, up to 2dB improvement in the receiver sensitivity in terms of the received optical power can be also achieved, compared to the conventional 64QAM modulation format.

Novel Data Pre-Distorter for APSK Signals in Solid-State Power Amplifiers

A computationally efficient data pre-distorter suitable for the 16 amplitude and phase-shift keying (APSK) constellation transmitted through a memoryless non-linear power amplifier is introduced. The proposed method is based on estimating the optimum value of the ring ratio that enables compensation for the power amplifier (PA) distortion occurring at each input back-off (IBO) level of a memoryless behavioral model. Previous results for data pre-distortion rely on iterative numerical optimization techniques which require increased computational resources. Instead, the proposed approach is numerically efficient and further provides insight on the generation of non-linear distortion. Computed and measured bit-error rate (BER) results for 16-APSK in additive white Gaussian noise (AWGN) channel and the presence of a PA are presented to prove the validity of the method. The performance evaluation of the pre-distorter based on a measured non-linear characteristic of a commercial power amplifier showed a BER reduction of up to four orders of magnitude at low IBO levels.

Algebraic Differential Spatial Modulation is Capable of Approaching the Performance of its Coherent Counterpart

We show that certain signal constellations invoked for classic differential encoding result in a phenomenon we term as the unbounded differential constellation size (UDCS). Various existing differential transmission schemes that suffer from this issue are identified. Then, we propose an enhanced algebraic field extension-based differential spatial modulation (AFE-DSM) scheme and its enhanced counterpart that strikes a diversity-rate tradeoff (AFE-DSM-DR), both of which overcome the UDCS issue without compromising its full transmit diversity advantage. Furthermore, the proposed schemes are extended to incorporate amplitude and phase shift keying (APSK) in order to exploit all the available degrees of freedom. Additionally, we propose a pair of detection schemes specially designed for APSK-aided differential transmission schemes. Explicitly, we conceive the buffered minimum mean squared error (B-MMSE) detector and buffered maximum likelihood (B-ML) detector, which exploit the knowledge of previously detected symbols in order to further improve the detection performance. Our simulation results have shown that the proposed detectors are capable of bridging the performance gap between the conventional differential detector (CDD) and the coherent detector that has full channel state information. Specifically, when employing the proposed APSK-aided AFE-DSM scheme operating at a rate of 2 b per channel use, the B-MMSE and B-ML detectors are observed to give about 3- and 3.5-dB signal-to-noise ratio gain with respect to their CDD counterpart at a bit error ratio of $10^{-5}$ .

Constant Envelope Precoding With Adaptive Receiver Constellation in MISO Fading Channel

Constant envelope (CE) precoding is an appealing transmission technique which enables the realization of high power amplifier (PA) efficiency. For CE precoding in a single-user multiple-input single-output (MISO) channel, a desired constellation is feasible at the receiver if and only if it can be scaled to lie in an annulus, whose boundaries are characterized by the instantaneous channel realization. Therefore, if a fixed receiver constellation is used for CE precoding in a fading channel, where the annulus is time-varying, there is in general a non-zero probability of encountering a channel that makes CE precoding infeasible, thereby causing a high probability of error. To tackle this problem, this paper studies the adaptive receiver constellation design for CE precoding in a single-user MISO flat-fading channel with an arbitrary number of antennas at the transmitter. We first investigate the fixed-rate adaptive receiver constellation design to minimize the symbol error rate (SER). Specifically, an efficient algorithm is proposed to find the optimal amplitude-and-phase shift keying (APSK) constellation with two rings that is both feasible and of the maximum minimum Euclidean distance (MED), for any given constellation size and instantaneous channel realization. Numerical results show that by using the optimized fixed-rate adaptive receiver constellation, our proposed scheme achieves significantly improved SER performance over CE precoding with a fixed receiver constellation. Furthermore, based on the family of optimal fixed-rate adaptive two-ring APSK constellation sets, a variable-rate CE transmission scheme is proposed and numerically examined.

Bit Error Rate Performance Comparison of Large Scale MIMO Receivers using Spatial Modulation

This paper proposes a novel approach of an Approximate Message Passing (AMP) detection method for Large Scale Multiple Input Multiple Output (LS-MIMO) receiver which uses MT transmit antennas and MR receive antennas to detect the information bits transmitted. An efficient transmission technique called Spatial Modulation (SM) in which the information bits are encoded and conveyed through the indexes of the transmit antennas using M-ary Amplitude and Phase Shift Keying (APSK) modulation to increase the efficiency of the receiver. Simulation results show that the Bit Error Rate (BER) performance of the proposed detection method performs near to the Maximum Likelihood (ML) detection and outperforms than the Modified Maximum Ratio Combiner (MMRC) detection.

Low-Complexity ML Detection for Spatial Modulation MIMO With APSK Constellation

Spatial modulation (SM) is a promising multiple-input–multiple-output (MIMO) transmission technology, which exploits the indexes of the transmit antennas for encoding information into the spatial dimension and, thus, for increasing the transmission rate. Optimal demodulation is realized by using a maximum-likelihood (ML) detector, which jointly estimates the information bits encoded into the transmit antenna indexes and into the transmitted symbol. If a large number of transmit antennas and/or a large modulation size are used; however, the computational complexity of ML demodulation may not be affordable for some applications. Against this background, we propose two novel near-ML but low-complexity detection schemes for SM-MIMO systems, which use $\boldsymbol{M}$ -ary amplitude and phase-shift keying (APSK) digital modulation. The proposed algorithms exploit specific features of the $\boldsymbol{M}$ -ary APSK constellation diagram, in order to avoid searching among all constellation points. It is shown, in particular, that the complexity of the proposed detection schemes is independent of the constellation size and that it only depends on the number of rings that constitute the APSK constellation. Simulation results are also provided, which confirm that the proposed detection schemes provide bit error probability performance close to that of ML demodulation but with lower demodulation complexity.

Approaching the Gaussian Channel Capacity With APSK Constellations

We consider the Gaussian channel with power constraint P. A gap exists between the channel capacity and the highest achievable rate of equiprobable uniformly spaced signal. Several approaches enable to overcome this limitation such as constellations with non-uniform probability or constellation shaping. In this letter, we focus on constellation shaping. We give a construction of amplitude and phase-shift keying (APSK) constellations with equiprobable signaling that achieve the Gaussian capacity as the number of constellation points goes to infinity.

Investigation and Analysis of SNR Estimation in OFDM system

Estimation of signal to noise ratio (SNR) of received signal and to transmit the signal effectively for the modern communication system. The performance of existing non-data-aided (NDA) SNR estimation methods are substantially degraded for high level modulation scheme such as M-ary amplitude and phase shift keying (APSK) or quadrature amplitude modulation (QAM).In this paper SNR estimation proposed method which uses zero point auto-correlation of received signal per block and auto/cross- correlation of decision feedback signal in orthogonal frequency division multiplexing (OFDM) system. Proposed method can be studied into two types; Type 1 can estimate SNR by zero point auto-correlation of decision feedback signal based on the second moment property. Type 2 uses both zero point auto-correlation and cross-correlation based on the fourth moment property. In block-by-block reception of OFDM system, these two SNR estimation methods can be possible for the practical implementation due to correlation based the estimation method and they show more stable estimation performance than the earlier SNR estimation methods.

Optimal 16-Ary APSK Encoded Coherent Optical OFDM for Long-Haul Transmission

In this letter, an optimal 4+12 amplitude and phase shift keying (APSK) modulated coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) system is proposed (the numbers 4 and 12 represent the constellation points located in the inner ring and the outer ring, respectively). Although the 4+12APSK modulation format has smaller average Euclidean distance than 16 quadrature amplitude modulation (QAM), the 4+12APSK modulated CO-OFDM system has the best transmission performance, with increased tolerance towards both amplified spontaneous emission noise and fiber nonlinearities compared with 16QAM and 8+8APSK modulated OFDM systems. The maximum reach at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor=8.2 dB (when bit-error rate (BER) equals 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ) is evaluated to assess the system performance based on a single-channel and five-channel wavelength division multiplexing (WDM) CO-OFDM system, and illustrates that the transmission performance of 4+12APSK modulated OFDM outperforms 8+8APSK modulated OFDM and 16QAM modulated OFDM by approximately 10.5%, and in the WDM system, it surpasses 8+8APSK modulated OFDM by approximately 5.6% and 16QAM modulated OFDM by 18.75%.

Application of differential amplitude and phase-shift keying in underwater acoustic communication based on orthogonal frequency division multiplexing

With the increase of of marine resource and underwater users, developing a high-bit-rate underwater acoustic communication has become a hot topic. Amplitude and phase-shift keying (APSK) is a modulation technique having high efficiency in spectrum utilization, it attracts more and more attention in high-bit-rate underwater acoustic communication. Differential APSK (DAPSK) is modulated using differential amplitude and phase code in time domain, and it has higher bandwidth efficiency and be easier to realize the system than APSK. A transmission system based on DAPSK modulation and OFDM is presented to solve the problems of effectiveness and reliability in high-bit-rate underwater acoustic communication. Simulation results show that the system using DAPSK modulation has a better performance than those using APSK and QAM modulation.

Performance evaluation of (D)APSK modulated coherent optical OFDM system

Performance of amplitude and phase shift keying (APSK) modulated coherent optical orthogonal frequency division multiplexing (CO-OFDM) with and without differential encoding is investigated. Numerical simulations based on 40Gbit/s single-channel and 5*40Gbit/s wavelength division multiplexing transmission are performed, and the impacts of amplified spontaneous emission noise, laser linewidth, chromatic dispersion, and fiber nonlinearity on the system performance are analyzed. The results show that compared with conventional 16 quadrature amplitude modulation (QAM) modulated optical OFDM signal, although 16(D)APSK modulated optical OFDM signal has a lower tolerance towards amplified spontaneous emission (ASE) noise, it has a higher tolerance towards fiber nonlinearity such as self-phase modulation (SPM) and cross-phase modulation (XPM): the optimal launch power and the corresponding Q2 factor of 16(D)APSK modulated OFDM signal are respectively 2dB and 0.5dB higher than 16QAM modulated optical OFDM signal after 640km transmission, both in single-channel and WDM CO-OFDM systems. Although the accumulated CD decreases the peak-to-average power ratio (PAPR) during transmission, 16(D)APSK modulated OFDM signal will still remain an advantage compared with 16QAM modulated OFDM signal up to 1000km single-channel transmission, meanwhile relaxing the needs for training symbols and pilot subcarriers and consequently increase the spectral efficiency.

APSK Modulated CO-OFDM System With Increased Tolerance Toward Fiber Nonlinearity

An amplitude and phase-shift keying (APSK) modulated coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) system is proposed, with increased tolerance toward fiber nonlinearity. Numerical simulation results, based on 30.2-Gb/s single-channel and 5×30.2-Gb/s wavelength-division-multiplexing (WDM) single-polarization CO-OFDM systems, show that compared with conventional 16 quadrature amplitude modulation (QAM) modulated optical OFDM signal, the 16 APSK modulated optical OFDM signal has a higher tolerance toward fiber nonlinearity, such as self-phase modulation and cross-phase modulation. The optimal launch power and the corresponding Q2 factor are, respectively, 2 and 0.5 dB higher than 16 QAM modulated optical OFDM signal after 640-km transmission, both in single-channel and WDM CO-OFDM systems.

Performance Analysis and Optimization of Non-Data-Aided Carrier Frequency Estimator for APSK Signals

This paper investigates the non-data-aided (NDA) carrier frequency estimation of amplitude and phase shift keying (APSK) signals. The true Cramer-Rao bound (CRB) for NDA frequency estimation of APSK signals are derived and evaluated numerically. Characteristic and jitter variance of NDA Luise and Reggiannini (L&R) frequency estimator are analyzed. Verified by Monte Carlo simulations, the analytical results are shown to be accurate for medium-to-high signal-to-noise ratio (SNR) values. Using the proposed closed-form expression, parameters of the algorithm are optimized efficiently to minimize the jitter variance.

Reduced-Complexity (Quasi-)Maximum-Likelihood Detectors with No Performance Degradation for S-QAM Modulated MIMO Systems

This paper proposes a rotation and scaling based transformation method to simplify the (quasi-)maximum-likelihood (ML) detectors (such as QRD-M, sphere decoding (SD), etc.) for the square quadrature amplitude modulation (S-QAM) modulated multiple-input and multiple-output (MIMO) systems with no performance degradation. The key idea of the simplification is to utilize the symmetric shape of the S-QAM constellation so that after rotation and scaling, real multiplication and addition with certain constellation points in symbol replica generation simply transform into bit shifting or even vanish. As an illustrative example, the QRD-M detector is employed in this work. By using the proposed method, the number of real multiplications of the symbol replica generation required for the QRD-M detector is reduced by 50% and 25% for 4-QAM and 16-QAM, respectively. The numbers of real addition reduction is twice the amount of multiplication. The underlying principle of the proposed rotation and scaling transformation can be straightforwardly extended to amplitude and phase-shift keying (APSK) modulated MIMO systems employing the QRD-M, SD, list sequential sphere decoder (LISS), list sphere decoding (LSD), and the full ML detectors.

Design and performance analysis of non-data-aided carrier phase estimators for amplitude and phase shift keying signals

This study studies the feedforward (FF) non-data-aided (NDA) carrier phase estimation of the amplitude and phase shift keying (APSK) signals. The true Cramer–Rao bounds (CRBs) for NDA phase estimation of APSK signals are derived and evaluated numerically using Gauss–Hermite quadrature. The jitter variance of the FF Viterbi–Viterbi (V&V) algorithm is analysed assuming the absence of data pattern noise. It is proved that, when the design parameter μ=2, the jitter variance is able to converge asymptotically to the modified CRB (MCRB) at high signal-to-noise ratios (SNRs). For practical application, the parameter μ is also optimised for 16/32/64-APSK signals at different SNRs. The analytical results of the jitter variance are verified by Monte-Carlo evaluations. It is shown that, for 32/64-APSK signals, the plain V&V algorithm cannot approach the CRBs due to the data pattern noise. A modified V&V algorithm based on the constellation partition and a linear combination of the sub-estimators is proposed to eliminate the divergence. Simulation results show that the jitter variance of the proposed estimator is very close to the CRB at the SNRs of interest and converges to the MCRB at high SNRs.

Numerical Study of APSK Format for Long-Haul Transmission and Its Performance Improvement by Zero-Nulling Method

Transmission performance of amplitude and phase shift keying (APSK) format is studied theoretically. The extinction ratio of the amplitude shift keying (ASK) signal of the APSK format causes a trade-off of the performance between the ASK and the phase shift keying (PSK) signal of the APSK format. Then, zero-nulling method is proposed to improve the performance of the APSK format, and its effectiveness is confirmed by the numerical simulation.

Numerical study of the performance improvement of the APSK transmission system using zero-nulling method

We have studied the transmission performance of amplitude and phase shift keying (APSK) format theoretically. As there is a trade-off between the performance of amplitude shift keying (ASK) and phase shift keying (PSK) through the extinction ratio of the ASK format, zero-nulling method to improve the performance of the PSK format had been proposed. A demerit of the zero-nulling method is a reduction of the total capacity. This paper described the effectiveness of the zero-nulling method when the total capacity of the system was identical.