M-ary Quadrature Amplitude Modulation Research Articles

Estimation of BER from Error Vector Magnitude for Optical Coherent Systems

This paper presents the estimation of bit error ratio (BER) from error vector magnitude (EVM) for M-ary quadrature amplitude modulation (QAM) formats in optical coherent systems employing carrier phase recovery with differential decoding to compensate for laser phase noise. Simulation results show that the relationship to estimate BER from EVM analysis for data-aided reception can also be applied to nondata-aided reception with a correction factor for different combined linewidth symbol duration product at the target BER of 10 − 3 . It is demonstrated that the calibrated BER, which would otherwise be underestimated without the correction factor, can reliably monitor the performance of optical coherent systems near the target BER for quadrature phase shift keying (QPSK), 16-QAM, and 64-QAM.

A Proposed Method to Reduce the BER in Wavelet based OFDM

Long term evolution (LTE) selects orthogonal frequency division multiplexing (OFDM) and its single-carrier counterpart SC-FDM as the basic transmission schemes. OFDM is a very interesting approach for high data rate transmission in a Gaussian channel and multipath fading environment that leads to inter symbol interference (ISI). In this paper, a proposed convolutional encoder model is used to improve the error rate performance of OFDM system, by using discrete wavelet transform (DWT) instead of fast Fourier transform (FFT) to reduce ISI. The performance of OFDM based on DWT using M-ary quadrature amplitude modulation (M-QAM) as a modulation scheme to achieve high data rate. The simulation results demonstrate that, the bit error rate (BER) is improved for a proposed convolutional encoder model as compared with the previous work. General Terms LTE, MATLAB simulator

Type of modulation identification using Wavelet Transform and Neural Network

Abstract Automatic recognition of the signal modulation type turned out to be useful in many areas, including electronic warfare or surveillance. The wavelet transform is an effective way to extract signal features for identification purposes. In this paper there are M-ary ASK, M-ary PSK, M-ary FSK, M-ary QAM, OOK and MSK signals analysed. The mean value, variance and central moments up to five of continuous wavelet transform (CWT) are used as signal features. The principal component analysis (PCA) is applied to reduce a number of features. A multi-layer neural network trained with backpropagation learning algorithm is considered as a classifier. There are two research variants: interclass and intraclass recognition with a wide range of signal-to-noise ratio (SNR).

Adaptive Threshold Estimation for Variable Rate MQAM in Full-Duplex Systems With Imperfect CSI

The adaptive threshold estimation algorithm for discrete variable rate M-ary quadrature amplitude modulation (VR-MQAM) is investigated in full-duplex (FD) systems with imperfect channel state information (CSI). First, detailed FD system modeling is carried out, taking into account the differences from the half-duplex systems on rate adaptations. Then, in this model, we obtain the closed-form expression of the VR-MQAM spectral efficiency by deriving the distribution of the received signal to interference and noise ratio (SINR). Finally, we propose an adaptive threshold estimation scheme for VR-MQAM, which can adapt to the variation of imperfect CSI as well as residual self-interference (SI). Numerical results reveal that both residual SI and CSI imperfection depress the performance of VR-MQAM. Comparing to the existing variable threshold scheme, our adaptive scheme improves the spectral efficiency without any extra complexity.

Increasing the information rates of optical communications via coded modulation: a study of transceiver performance.

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.

Universal soft demodulation schemes for M ‐ary phase shift keying and quadrature amplitude modulation

In this study, the authors propose an efficient universal soft demodulation method for M-ary phase shift keying (PSK) and quadrature amplitude modulation (QAM) schemes. The proposed method achieves the same performance as the Max-log method with much lower, linear-order complexity. The proposed demodulator recursively maps the detected symbol to a specific region in the first quadrant, so that finally there is only one constellation symbol left in the region, and thus it requires approximately one distance estimation per bit. The authors first derive the equations to estimate soft decision bit information for a few well-known M-ary PSK and QAM schemes, and subsequently present compact universal equations applicable to any M-ary PSK and QAM schemes, respectively. The simulation results reveal that the proposed method produces exactly the same performance as the Max-log method with greatly reduced computational complexity.

Signal‐to‐noise ratio estimation for DVB‐S2 based on eigenvalue decomposition

Signal-to-noise ratio (SNR) estimation is required in many receivers and systems of communications. In this study, the authors propose a novel SNR estimation method for DVB-S2 over additive white Gaussian noise channel. This is a non-data-aided, eigenvalue decomposition-based method. First, they use the even and odd component vectors of received signal to construct a novel 2 × 2 matrix, and propose an estimation variable using the standard condition number of this matrix. And then, they derive the relationship between this variable and SNR, and give the detailed expressions for SNR estimation on different modulations used in DVB-S2, including quadrature phase shift keying, 8PSK, 16 amplitude PSK (APSK) and 32APSK. Monte Carlo simulation results show the good estimation performance for different modulations. The proposed method is asymptotic unbiased and can be used for both constant and non-constant modulus constellations such as M-ary PSK, MAPSK and M-ary quadrature amplitude modulation.

Polynomial based Channel Estimation Technique with Sliding Window for M-QAM Systems

Pilot Symbol Assisted Modulation (PSAM) channel estimation techniques over Rayleigh fading channels have been analysed in recent years. Fluctuations in the Rayleigh fading channel gain degrades the performance of any modulation scheme. This paper develops and analyses a PSAM Polynomial interpolation technique based on Least Square (LS ) approxi-mations to estimate the Channel State Information (CSI) for M-ary Quadrature Amplitude Modulation (M-QAM) over flat Rayleigh fading channels. A Sliding window approach with pilot symbol adjustment is employed in order to minimize the computational time complexity of the estimation technique. The channel estimation performance, and its computational delay and time complexity is verified for di?erent Doppler frequen-cies ( fd), frame lengths (L), and Polynomial orders (P-orders). Simulation results show that the Cubic Polynomial interpolation gives superior Symbol Error Rate (SER) performance than the Quadratic Polynomial interpolation and higher P-orders, and the performance of the Polynomial estimation techniques degrade with increase in the P-orders.

Pilot-added carrier-phase recovery scheme for Nyquist M-ary quadrature amplitude modulation optical fiber communication system

A new two-stage carrier-phase recovery scheme using a combination of an optical pilot-aided algorithm with the crossed constellation transformation algorithm for either square-framed or non-square-framed M-level-quadrature amplitude modulation (QAM) Nyquist systems is proposed. It is verified in 32- and 128-QAM systems that it can provide high linewidth tolerance with little complexity.

The Influence of Digital Modulations on 320 Gbit/s Optical Time Division Multiplexing

In this article the optical time division multiplexingtechnique for high speed point-to-point optical networksis discussed. We performed test of influence of selected types modulation formats in the optical time division multiplexing simulation model with a distance of 30 km. Additionally, this paper focuses on maximum bandwidth usage, improvement of bit error rate and the another goal is to achieve the maximal transmission distance by using of special compensation optical fiber. Optimal length of compensation optical fiber was found and used during simulations. We demonstrated positive influence compensation optical fiber on bit error rate. For comparisonof modulation formats such as return-to-zero, non-return-to-zero, chirped-return-to-zero, carrier-suppressed-return-to-zero, and m-ary quadrature amplitude modulation were tested. Our results confirm that it is possible to achieve better bit error rate for selected modulation formats.

Error rate performance analysis of multiantenna MC DS-CDMA system over η–μ frequency selective fading channels with arbitrary parameters

Wireless communication channels have harmful impact on the performance of the wireless communication systems due to the severe influences of multipath fading, path loss, shadowing, intentional and unintentional interference, and noise, respectively. In this paper, we investigate the performance of the orthogonal multicarrier direct sequence code division multiple access (MC DS-CDMA) system coupled with multiple input multiple output (MIMO) system operating over independent nonidentically distributed (i.ni.d) η–μ multipath fading channels in terms of average error probability. Based on moment generating function (MGF) and probability density function (PDF) approaches, closed form expressions for average error probability of binary phase shift keying (BPSK), multilevel phase shift keying (MPSK), and square M-ary quadrature amplitude modulation (MQAM) schemes are derived and expressed in terms of Appell's hypergeometric functions and Lauricella's multivariate hypergeometric functions. The numerical results show that the effects of arbitrary fading parameters, decaying power factor (d), and signal constellation size on the system performance can be reduced using spatial and temporal path diversities. We validate the correctness of the analytical approaches using Monte Carlo simulation techniques.

Conditional Power and Rate Adaptation for MQAM/OFDM Systems Under CFO With Perfect and Imperfect Channel Estimation Errors

In this paper, a new conditional power and rate adaptation scheme for orthogonal frequency-division multiplexing (OFDM) systems is proposed in the presence of carrier frequency offset (CFO), with perfect and imperfect channel state information (CSI). The conventional adaptive scheme is shown to be a special case of the conditionally adaptive scheme technique that enables the resulting nonconvex optimization problem, which is solved in a feasible way. It leads to a solution for optimal power adaptation that maximizes the spectral efficiency of an OFDM system using $M$ -ary quadrature amplitude modulation (MQAM) under average power and instantaneous bit error rate (BER) constraints. Closed-form expressions for the average spectral efficiency (ASE) of adaptive OFDM systems are derived for perfect and imperfect CSI cases. The theoretical results and computer simulations show that range of the conditional adaptation becomes narrow and the performance of constant power and continuous rate is very close to that of the conditionally adaptive power and continuous rate for higher CFO or high signal-to-noise ratio (SNR) values.

Performance analysis of zero‐forcing‐precoded scheduling system with adaptive modulation for multiuser‐multiple input multiple output transmission

In this study, the author presents performance analysis of a zero-forcing (ZF)-precoded scheduling system with adaptive modulation for multiuser-multiple input multiple output transmission. The proposed scheduling system adapts the transmission rate and selects the best modulation to satisfy a given target bit error rate (BER). The author derive the tight closed-form expressions of the ZF-precoded system with adaptive modulation for the average spectral efficiency where user set non-scheduling and user set scheduling methods are presented. The author also presents the tight closed-form BER expressions of the non-scheduling and scheduling systems with adaptive modulation for M-ary quadrature amplitude modulation and M-ary phase shift keying modulation. From the analytical results, the author shows that the proposed scheduling system provides performance improvement of the average spectral efficiency over the non-scheduling system. Moreover, the proposed system provides the signal to noise ratio gain compared with the non-scheduling system to satisfy the target BER regardless of modulation types. This is because the diversity order of the proposed system is superior to that of the non-scheduling system by multi-user diversity.

Decision directed iterative channel estimation and Reed–Solomon decoding over flat fading channels

Iterative channel estimation and decoding over flat Rayleigh fading channels have been shown in literature to improve the performance of receivers in wireless communication systems. Turbo and low density parity check codes have mostly been used as the forward error correction (FEC) scheme in the iterative receiver structures. This study proposes a decision directed iterative channel estimation and decoding receiver using Reed–Solomon codes. In particular, the Koetter and Vardy, Reed–Solomon (KV–RS) soft decision decoder is adopted in the receiver structure as the FEC scheme. Two methods of deriving a priori information in joint iterative channel estimation and decoding receiver structures are also analysed in this study. The first method derives the a priori information employing the log likelihood ratio (LLR) method. A priori information derived using the LLR method is mostly used in iterative receiver structures in the literature. The second method derives the a priori information employing the distance metric (DM) method. The DM method is proposed in this study as an alternative approach to the LLR method of deriving a priori information in the iterative receivers. Hard and soft feedback information from the KV–RS decoder is considered to verify the performance of these methods. The performance of the two a priori information methods is documented through computer simulation assuming an M-ary quadrature amplitude modulation system. Simulation results verify the improvement in symbol error rate (SER) performance in the KV–RS iterative receiver structure in comparison with the KV–RS receiver without feedback. Also, the proposed DM method exhibits the same SER performance in comparison with the LLR method which is mostly used in the literature. More importantly, the proposed DM method has the advantage of less computational delay and time complexity compared with the LLR method.

Design Methodology of High Frequency M-ary ASK, FSK and QAM

This paper proposes a high data rate, low-power, low-voltage design of OTA-based M-ary ASK, FSK and QAM modulator and demodulator circuits. Conventional D/A converter of M-ary circuit has been replaced with the operational transconductance amplifier-based n-bits to 2n level converter which operates with input frequencies up to 2.1 GHz. OTA-based oscillator and PLL is being designed for high speed M-ary FSK. Eye diagram analysis has been carried out, conforming a very low signal distortion. Theoretical analysis of bit error rate has been done. The circuit analysis and simulation results confirm the reliability and accuracy of the design. Effective layouts and die photographs of the proposed designs are also presented.

Impact of M-ary Data Symbol Burst Transmission on Averaged Channel Capacity for ADF Relay Systems

In this paper, we consider M-ary phase shifting keying (MPSK) and M-ary quadrature amplitude modulation (MQAM) data symbol burst transmission for adaptive decode-andforward (ADF) relay systems over quasi-static Rayleigh fading channels. A burst has pilot symbols and data symbols. From pilot symbols, we can estimate the channel gain and detect each relay node’s transmission mode for ADF schemes. At first, we focus on the derivation of the received signal to noise ratio’s (SNR’s) probability density function (PDF) for ADF relay systems, in which error events at relay nodes and channel estimation errors are considered. Then, we derived the averaged channel capacity as an approximated closed-form for an arbitrary link signal-to-noise ratio (SNR) for different modulation orders. We verified its accuracy by comparison with simulation results.

Minimization of Wireless Sensor Network Energy Consumption Through Optimal Modulation Scheme and Channel Coding Strategy

Wireless sensor networks (WSNs) are composed of sensor nodes generally powered by batteries, for which recharging or replacement is difficult. Since battery technology has not progressed as rapidly as semiconductor technology, energy efficiency has become increasingly important in WSN. On the other hand, data exchanged between nodes are vulnerable to corruption by errors induced by random noise, signal fading and other factors. Therefore, improving link reliability and reducing energy consumption are prime concerns in the design of wireless sensor networks. In this context, performing optimal modulation schemes with suitable channel coding process is a crucial task at the physical layer of this class of networks. This paper investigates the best modulation strategy to minimize the total energy consumption required to send a given number of bits. Energy consumption with both uncoded and coded modulation techniques including M-ary QAM (MQAM), M-ary PSK (MPSK), M-ary FSK (MFSK) and MSK is analytically analyzed and simulated over transmission time, modulation rate and transmission distance. A comparative analysis in terms of energy consumption and probability of Bit Error Rate (BER) referring to MSK modulation with proper Error Control Codes (ECC) approach is presented in this paper. We show that the gain achieved with coded MSK scheme is very promising for obtaining optimal energy network consumption.

Design Strategies and Merit of System Parameters for Uniform Uncompensated Links Supporting Nyquist-WDM Transmission

We consider the transmission of Nyquist-wavelength-division-multiplexed channels based on polarization-multiplexed m-ary QAM multilevel modulation formats with DSP-based coherent detection over point-to-point uncompensated periodically amplified uniform fiber links. Taking into account both the effect of amplified spontaneous emission noise accumulation and generation of nonlinear interference (NLI) introduced by fiber propagation, we propose three different design strategies: the maximization of both the Q margin and the span-loss margin, for a given span length, and the maximization of the total link length given a target performance. We propose and apply an approximation for the Gaussian-noise model in order to evaluate the NLI intensity, deriving for the three design strategies the merit of link and signal parameters. Finally, we validate the proposed methodologies using experimental and simulative results already published in the literature.

A novel user pairing scheme for functional decode-and-forward multi-way relay network

In this paper, we consider a functional decode and forward (FDF) multi-way relay network (MWRN) where a common user facilitates each user in the network to obtain messages from all other users. We propose a novel user pairing scheme, which is based on the principle of selecting a common user with the best average channel gain. This allows the user with the best channel conditions to contribute to the overall system performance. Assuming lattice code based transmissions, we derive upper bounds on the average common rate and the average sum rate with the proposed pairing scheme. Considering M-ary quadrature amplitude modulation with square constellation as a special case of lattice code transmission, we derive asymptotic average symbol error rate (SER) of the MWRN. We show that in terms of the achievable rates, the proposed pairing scheme outperforms the existing pairing schemes under a wide range of channel scenarios. The proposed pairing scheme also has lower average SER compared to existing schemes. We show that overall, the MWRN performance with the proposed pairing scheme is more robust, compared to existing pairing schemes, especially under worst case channel conditions when majority of users have poor average channel gains.

Symbol Error Rate Analysis of Joint Diversity System With Channel Estimation Error

In this paper, we investigate the impact of channel estimation error on symbol error rate (SER) for joint diversity (i.e., combining space–time block coding and user scheduling) in multiple-input–multiple-output systems with a channel estimation error. Under a Gaussian distributed channel estimation error, the exact expressions of the joint diversity for SER with both M-ary quadrature amplitude modulation (QAM) and phase-shift keying (PSK) modulation are derived. Using probability density function approximation, we quantify the diversity order and signal-to-noise ratio (SNR) gain of SER for joint diversity in the presence of a channel estimation error. From the analysis results, we show that the diversity order is enhanced as the number of user terminals increases, regardless of the modulation type. This is because user scheduling provides multiuser diversity. Moreover, the SNR gain decreases as the number of user terminals increases. This is because the peak effective SNR in joint diversity decreases as the number of user terminals increases.