M-ary Quadrature Amplitude Modulation Research Articles

Evaluation of the Performance of a Reed Solomon Coded STBC MIMO System Concatenated with MPSK and MQAM in Different Channels

Background & Objective: Wireless technologies like Wi-Fi, WiMAX, and LTE are using Multiple Input, Multiple Output (MIMO) communications that play an important role in achieving high data rates. Bit Error Rate (BER) is one of the most important performance parameters in multipath channels for data communication. Methods: This research proposes a new method based on Reed Solomon (RS) coding to improve the efficacy of a Space-Time Block Coded (STBC) MIMO System concatenated with M-ary Phase Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) in reducing BER in Rayleigh, Rician and Nakagami channels. It is based on the error detection and correction properties intrinsic to RS coding processes. Binary data is coded using an RS encoder and the modulated signal STBC encoded and transmitted through Rayleigh, Rician and Nakagami channels. Signals received by two antennas are STBC decoded, demodulated, RS decoded and tested for BER. Results & Conclusion: Results show lower BER rates for RS Coded systems as compared for uncoded systems in all three channels. In addition, it was found that reduction in BER is greater for high Signal to Noise Ratio (SNR) but deteriorates for low SNR. Furthermore, this research observed that RS coding gives 63% to 98% improvement in BER in the Rayleigh as compared to Rician and Nakagami channels. This research has been able to successfully incorporate the BER reduction of STBC MIMO to further enhance the efficacy of an STBC MIMO system.

High-Throughput and Improved-Convergent Design of Pipelined Adaptive DFE for 5G Communication

This brief presents a high-throughput and improved convergent design of pipelined adaptive decision feedback equalizer (ADFE) for 5G communication system. The proposed ADFE design achieves 3.3 Gbps for 4-quadrature amplitude modulation (4-QAM) and 8th order feedback filter (FBF). A novel look-up table update scheme for M-ary QAM ADFE is proposed. Further, we present an efficient quantization scheme for the proposed design. Theoretical derivations and simulation results confirm that the convergence performance of the proposed ADFE is superior. For instance, the proposed design for 16-QAM and 16th order FBF takes 167 less iterations and improves 4.03 dB error performance, while it provides nearly 8.96 times higher throughput as compared to the best existing design.

Characterization of Orthogonal Frequency Division Multiplexing (OFDM) Communication Links

The demand for high data rate transmission is rapidly increasing in the area of wireless communications and Orthogonal Frequency Division Multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. The idea is to utilize a number of carriers, spread regularly over a frequency band, in such a way so that the available bandwidth is utilized to maximal efficiency. This study presents the comparison of the performance of different modulation schemes: M-ary phase shift keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) over Additive White Gaussian Noise (AWGN), Rayleigh and Rician multipath fading channels in OFDM system. Bit error rate (BER) was used to evaluate the performance of the system; the number of fast Fourier transform (FFT) points used during the transmission was also examined. The results showed that for all the channels, lower order modulation schemes perform better than the higher order schemes. This comes at the detriment of the data rate, as lower order schemes have lower data rates compared with their higher order counterparts. In addition, it was observed that the system performed better in AWGN channel than Rayleigh and Rician fading channels for all the modulation schemes used. It was observed that the number of FFT points used during the transmission do not have much effects on the performance of the system.

Low-complexity carrier phase estimation for M-ary quadrature amplitude modulation optical communication based on dichotomy.

In high-speed optical communication, the blind phase search (BPS) algorithm performs carrier phase estimation better but with higher computational complexity (CC), bringing a larger computational burden to the digital signal processing unit. In this paper, a new low-complexity CPE algorithm (DBPS) is proposed for M-ary quadrature amplitude modulation (M-QAM) formats. It uses the BPS algorithm to estimate the compensation phase interval, before using dichotomy to quickly and accurately determine the compensation phase value. Simulation results show the CC (multiplication / addition) of DBPS is reduced by 2.79 / 2.84 (16-QAM), 5.35 / 5.45 (64-QAM), and 2.98 / 3.01 (128-QAM) than that of BPS, and DBPS has a smaller phase tracking error variance. DBPS can relax the limitation of optical communication rate caused by high-speed data operations.

Modulation Scheme Identification Based on Artificial Neural Network Algorithms for Optical Communication System

Higher-order modulation schemes in optical communication systems that suffer from several impairments can use artificial intelligence (AI) algorithms, among other possible techniques, to mitigate these issues. In this paper, several techniques for optical communication systems have been proposed to enhance the performance of dual-polarization (DP) M-ary Quadrature Amplitude Modulation (M-QAM) as DP-16-QAM, DP-64-QAM, DP-128-QAM, and DP-256-QAM with 240Gbps data rate. Artificial neural networks (ANNs) with seven different training algorithms have been applied to optimize the optical communication system. A high optimization of modulation format identification (MFI) with accuracy up to 100% was obtained at about 13 dB OSNR and at 22 dB OSNR for the DP-265-QAM format.

Performance analysis of M‐APSK generalised spatial modulation with constellation reassignment

SummaryGeneralised spatial modulation (GSM) is a recently developed multiple‐input multiple‐output (MIMO) technique aimed at improving data rates over conventional spatial modulation (SM) systems. However, for identical antenna array size and configurations (AASC), the bit error rate (BER) of GSM systems in comparison with SM systems is degraded. Recently, a GSM system with constellation reassignment (GSM‐CR) was proposed in order to improve the BER of traditional GSM systems. However, this study focused on M‐ary quadrature amplitude modulation (M‐QAM) schemes. The focus of this paper is the application of a circular constellations scheme, in particular, amplitude phase shift keying (APSK) modulation, to GSM and GSM‐CR systems. An analytical bound for the average BER of the proposed M‐APSK GSM and M‐APSK GSM‐CR systems over fading channels is derived. The accuracy of this bound is verified using Monte Carlo simulation results. A 4 × 4 16‐APSK GSM‐CR system achieves a gain of 2.5 dB at BER of 10−5 over the traditional 16‐APSK GSM system with similar AASC. Similarly, a 6 × 4 32‐APSK GSM‐CR system achieves a gain of 2 dB at BER of 10−5 over equivalent 32‐APSK GSM system.

Implementation of 2x2 MIMO-OFDM System using Universal Software Radio Peripherals

Abstract: The 2x1 and 2x2 Multiple Input Multiple Output (MIMO) systems with Orthogonal Space-Time Block Code (OSTBC) are implemented using Universal Software Radio Peripherals (USRPs) and LabVIEW. Bit Error Rate (BER) is estimated and compared for both systems using different Mary Quadrature Amplitude Modulation (QAM) i.e. 4 QAM, 16 QAM, 64 QAM. The BER is reduced for a 2x2 MIMO than a 2x1. To improve spectral efficiency, Orthogonal Frequency Division Multiplexing (OFDM) is combined with MIMO configuration, known as MIMO-OFDM. 2x2 MIMO-OFDM with OSTBC is implemented with M-ary QAM and N IFFT(32, 64, 128 IFFT). Among these, better BER performance is observed for 2x2 MIMO with 64-IFFT. The MIMO-OFDM is used in Worldwide Interoperability for Microwave Access (WiMAX) which is the standard of IEEE 802.16. Index Terms: Multiple Input and Multiple Output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM), Bit Error Rate (BER), Universal Software Radio Peripheral (USRP)

Fractional Fourier Transform Based M-ary Chirp Modulation

In this paper, a novel M-ary chirp modulation scheme is proposed on the basis of the energy concentration property of chirp signals in fractional domain. In the proposed scheme, chirp signals with different phases are multiplexed in the same time-frequency bandwidth through reverse chirp-rate to increase information rate. In addition, fractional filters based on fractional Fourier transform (FRFT) are designed to separate chirp signals of different chirp-rates in the receiver. Moreover, the theoretical performance of fractional filters and the error probability of M-ary chirp system are derived. Both theoretical analysis and simulation prove that the proposed scheme outperforms M-ary quadrature amplitude modulation (QAM) system in the anti-noise performance.

Analysis of Bit Error Rate on M-ary QAM over Gaussian and Rayleigh Fading Channel

Transmission of signal over long distance through the channel will result in poor signal quality reception at the receiver. The Signal quality is affected by means of fading and it can be minimized by using effective modulation techniques. M-ary QAM is one of the effective modulation techniques as it has higher efficiency and effective form of modulation for data. M-QAM is a modulation where data bit selects M combinations of amplitude and phase shifts that are applied to carrier. The analysis carried out based on Bit Error Rate on various M -Quadrature Amplitude Modulation schemes like 16 -QAM, 64- QAM and 256- QAM over Gaussian and Rayleigh Fading channel. The input data entered into QAM modulator then transmits over Gaussian channel and the QAM demodulator is performed at the receiver. The same process repeated over Rayleigh fading channel for M-QAM. Rayleigh fading is multipath fading channel will vary randomly according to the Rayleigh distribution. The MATLAB simulation is carried out to get experimental results on M-QAM and compared. The analysis shows that improved Bit Error Rate in 16-QAM over Gaussian and Rayleigh fading channel.

Closed Form Expressions for Average Capacity and Symbol Error Rates Under Different Diversity Techniques Over EGK Fading Under Interference

In the last decade, many fact-findings have been given on the performance analysis of composite fading channels in wireless communication. Various literatures have presented the performance analysis which includes shaping and severity factors of the multipath and shadowing simultaneously. But very limited amount of literature has included above factors in the path of desired users and interferers both. However, this paper present various closed form expressions of average capacity and symbol error rates (SER) over generic composite fading channel by considering shaping and severity parameters of the multipath and shadowing simultaneously, not only in the desired but in the interfering path as well. Specifically, closed form expressions for average capacity with equal gain combining/maximal ratio combining (MRC) and without diversity scheme have been presented. SER of M-ary phase shift keying and M-ary quadrature amplitude modulation scheme under MRC diversity scheme has been also presented. Moreover, in this paper, performance degradation for interferers and performance improvement for desired users have been researched by decreasing the value of severity of either multipath or shadowing in the path of interferers and desired users respectively. All the proposed results have been numerically compared with the available literatures, showing the perfect agreement.

Hard-Decision Coded Modulation for High-Throughput Short-Reach Optical Interconnect.

Coded modulation (CM), a combination of forward error correction (FEC) and high order modulation formats, has become a key part of modern optical communication systems. Designing CM schemes with strict complexity requirements for optical communications (e.g., data center interconnects) is still challenging mainly because of the expected low latency, low overhead, and the stringent high data rate requirements. In this paper, we propose a CM scheme with bit-wise hard-decision FEC and geometric shaping. In particular, we propose to combine the recently introduced soft-aided bit-marking decoding algorithm for staircase codes (SCCs) with geometrically-shaped constellations. The main goal of this CM scheme is to jointly boost the coding gain and provide shaping gain, while keeping the complexity low. When compared to existing CM systems based on M-ary quadrature-amplitude modulation (MQAM, ) and conventional decoding of SCCs, the proposed scheme shows improvements of up to dB at a bit-error rate of in the additive white Gaussian noise channel. For a nonlinear optical fiber system, simulation results show up to reach increase. In addition, the proposed CM scheme enables rate adaptivity in single-wavelength systems, offering six different data rates between 450 Gbit/s and 666 Gbit/s.

Performance analysis of uncoded and SFBC OFDM system over composite fading channels

This paper presents the performance of uncoded and space-frequency block coded (SFBC) orthogonal frequency division multiplexing (OFDM) system for two recently proposed composite fading model i.e. Fisher–Snedecor (F) and κ-μ/gamma. Both models are adequate for wearable communication system. In this paper, we derive the exact and approximate expressions of average bit error rate (ABER) for uncoded and SFBC OFDM system using fast Fourier transform (FFT) and fractional Fourier transform (FrFT). Further, these generalized expressions reduce to special cases of both composite fading models. Particularly, M-ary quadrature amplitude modulation (MQAM) and M-ary phase-shift keying (MPSK) modulation schemes are considered to derive ABER expressions. The numerical results are compared with the previous results of Rayleigh and Nakagami-m distribution. Also, the Monte Carlo simulation results are provided to crosscheck the validity of derived expressions.

On the performance of adaptive hybrid MQAM-MPPM scheme over Nakagami and log-normal dynamic visible light communication channels.

In this paper, we introduce the idea of using adaptive hybrid modulation techniques to overcome channel fading effects on visible light communication (VLC) systems. A hybrid $ M $M-ary quadrature-amplitude modulation ($ M{\rm QAM} $MQAM) and multipulse pulse-position modulation (MPPM) technique is considered due to its ability to make gradual changes in spectral efficiency to cope with channel effects. First, the Zemax optics studio simulator is used to simulate dynamic VLC channels. The results of Zemax show that Nakagami and log-normal distributions give the best fitting for simulation results. The performance of $ M{\rm QAM} $MQAM-MPPM is analytically investigated for both Nakagami and log-normal channels, where we obtain closed-form expressions for the average bit-error rate (BER). The optimization problem of evaluating the hybrid modulation technique settings that lead to the highest spectral efficiency under a specific channel status and constraint of outage probability is formulated and solved using an exhaustive search. Our results reveal that the adaptive hybrid scheme improves system spectral efficiency compared to ordinary QAM and MPPM schemes. Our results reveal that the adaptive hybrid scheme improves system spectral efficiency compared to ordinary QAM and MPPM schemes. Specifically, at low average transmitted power, $ - 32\;{\rm dBm} $-32dBm, the adaptive hybrid scheme shows 280% improvement in spectral efficiency compared to adaptive versions of ordinary schemes. At higher power, $ - 20\;{\rm dBm} $-20dBm, 6.5% and 725% improvement are obtained compared to ordinary QAM and ordinary MPPM, respectively. Also, the adaptive hybrid scheme shows great improvement in average BER and outage probability compared to ordinary schemes. The hybrid scheme shows 28%, 34%, and 38% improvement, respectively, for $ m = 1,2,3 $m=1,2,3 for Nakagami channels at $ {\rm BER}{ = 10^{ - 3}} $BER=10-3. Also, the outage probability of hybrid schemes of $ {\rm BER}{ = 10^{ - 3}} $BER=10-3 shows 30% and 14% better performance than ordinary $ M{\rm QAM} $MQAM and MPPM schemes, respectively.

Bit error probability of M-QAM under η-μ or κ-μ fading and impulsive noise gated by a signal characterized by a Markov process or Poisson process

This article presents exact expressions for the bit error probability (BEP) of the M-ary quadrature amplitude modulation (M-QAM) scheme subject to η-μ or κ-μ fading and gated additive white Gaussian noise (GAWGN), which is a noise formed by the sum of a white Gaussian component of variance σg2 and a white Gaussian noise component of variance σi2 gated by a signal C(t). In this work, the signal C(t) is characterized by a Markov process or a Poisson process (telegraphic process) and is used to model the instants of appearance and disappearance of the impulsive noise in the communication system. The expressions presented in this paper are new, simple, written in terms of elementary functions and encompass, as special cases, the BEP expressions of a variety of fading models, such as Nakagami-m, Nakagami-q, Rayleigh, Rice and one side Gaussian. BEP curves are also shown in this work, corroborated by simulations performed with Monte Carlo method, for different values of the signal to impulsive noise ratio, modulation order and parameters that characterize the number of transitions of the signal C(t) from state zero to state one in a symbol interval.

Computationally Efficient Soft Detection Schemes for Coded Massive MIMO Systems

This paper presents a computationally efficient soft detection scheme for massive multiple-input multiple-output (MIMO) systems. The proposed scheme adopts joint iterative detection and decoding (JIDD) methods for their capacity limiting performances. In addition, the minimum mean square error parallel interference cancellation (MMSE-PIC)-based detection scheme is used for soft information exchange. We propose a number of techniques to reduce the computational complexity, while keeping almost the same performance as the conventional ones. First, a technique is proposed to approximate the Gram matrix to a constant valued diagonal matrix. This proposal can lead to elimination of complex matrix inversion process and multiple layer dependent estimations, resulting in huge complexity reduction. Second, compact equations to estimate soft-symbol values for M-ary (quadrature amplitude modulation) QAM are derived. From the investigation example of 2 8 -QAM in this paper, this proposal showed more than two orders of less computations compared to the conventional scheme. The simulation results demonstrate that the proposed method can achieve approximating performance to the conventional method with a largely reduced computational complexity.

Spectral efficiency of adaptive OFDM systems over high mobility Nakagami-m fading channels

ABSTRACT In this paper, we investigate the impact of rate and power adaptation (RPA) and rate adaptation (RA) using square M-ary quadrature amplitude modulation (MQAM) on the average spectral efficiency (ASE) of orthogonal frequency division multiplexing (OFDM) systems under instantaneous bit-error-rate (BER) constraint over high mobility Nakagami multipath fading (NMF) channels. Especially, the closed-form expressions for the average spectral efficiency (ASE) of RPA and RA are obtained when these adaptive schemes are used over NMF channels with existence inter-carrier interference (ICI) caused by the high mobility. By comparing the ASE of RPA and RA under different number of subcarriers, a simplified rate and subcarriers bandwidth adaptation (RSBA) algorithm is obtained. Simulation results indicate that RSBA is more suitable for high-speed communication environment than RA.

Simplified implementation of millimetre‐wave zero‐bias detector for an accurate detection in six‐port‐based receivers

In this Letter, a simplified design approach for zero-bias power detectors suited for integration in six-port receiver architectures is presented. The proposed concept uses the quadrature hybrid coupler as an effective way to improve the input impedance matching and linearity performance. The proposed solution has been experimentally validated through its implementation into a 60 GHz six-port receiver prototype to investigate its performance in detecting various M-ary quadrature amplitude modulation (M-QAM) signals. The obtained measurement results show a high accurate and linear detection responses for all investigated M-ary QAM modulation techniques (4-QAM, 16-QAM, 32-QAM). The variation in the error rates of the demodulated signals at the adjacent differential outputs is minimal (<1%), and the maximum error rate achieved does not exceed 5%. The obtained precision and linearity performances make the proposed structure highly suitable for the emerging millimetre-wave six-port receiver front-ends.

SNR-availability-based optical network provisioning

We review recently proposed metrics, Q availability and signal-to-noise ratio (SNR) availability, based on statistical performance of optical signals, for modulation format assignment in network provisioning. These metrics assign a modulation format aiming to maximize spectral efficiency while satisfying the specified service availability. Q availability is suitable for tunable modulations with a discrete data rate based on M-ary quadrature amplitude modulations (mQAMs), while SNR availability is more suitable for fine-tunable modulations such as time-domain hybrid mQAM or a probabilistically shaped signal as well as discrete mQAMs. We also present a new guideline, to the best of our knowledge, on how to estimate network capacity without full network simulations when fine-tunable modulations are provisioned using SNR availability. We apply this guideline on three different network topologies and show 18.7% to 35.7% capacity gains with probabilistically shaped signal over mQAMs. SNR availability serves as a useful metric for provisioning in future optical networks adopting fine-tunable modulations.

Phase Uniformly Distributed Circular MQAM Combined With Probabilistic Shaping for PM-CO-OFDM Systems in Satellite-to-Ground Optical Communications

Due to the rapid growth of high-resolution services, low earth orbit satellite-to-ground (LEO-StG) optical communications are expected to provide higher speed and better receiver sensitivity transmission. Here, we propose a phase uniformly distributed circular m-ary quadrature amplitude modulation (MQAM) combined with probabilistic shaping (PS) scheme for polarization multiplexing coherent optical orthogonal frequency-division multiplexing (PM-CO-OFDM) systems in LEO-StG communications to achieve high capacity transmission and improve receiver sensitivity as well as linewidth tolerance. In such scheme, the radius ratio of the circular 16/32QAM is optimized to maximize the minimum Euclidean distance (MED), and the constellation points of each ring are uniformly distributed to maximize the phase space of adjacent constellation points. Besides, the circular 16/32QAM is combined with probabilistic shaping (PS) to further increase the MED under the constraint of average transmit power. Simulation results of such circular 16/32QAM combined with PS scheme under different turbulence channels not only demonstrate its feasibility, but also show the improvements in receiver sensitivity and linewidth tolerance compared with regular 16/32QAM under same entropy. The improvement of receiver sensitivity is also experimentally validated. The superiorities of such scheme make it highly desirable for potential application in long-reach, non-relay, and high capacity LEO-StG optical communications .

Performance Study of Wireless Systems with Switch and Stay Combining Diversity over α-η-μ Fading Channels

In this paper, we consider a Switch and Stay Combiner (SSC) diversity scheme operating over α−η−μ fading channel. New and closed-form expressions for the average output SNR (ASNR), the moment-generating function (MGF), the outage probability (P_out), and the average symbol error rate (ASER) for M-ary quadrature amplitude modulation (QAM) signaling are derived. The expressions are obtained in terms of the well-known bivariate Fox’s H-function (BFHF). It is worth pointing out that the BFHF and the bivariate Meijer’s G-function (BMGF) have recently been used extensively in wireless communications literature to study the system's performance. The evaluated results are plotted for channel parameters of interest, and the effect of fading severity on the combiner performance is studied. Moreover, the results are shown to match those previously reported in the literature for other channel models such as η−μ as a special case, which confirms the validity of the obtained expressions. Also, insights on the optimal choice of the switching threshold are provided.