Quadrature Amplitude Modulation Research Articles

ОДНОВИМІРНА ЗГОРТКОВА МОДЕЛЬ НЕЙРОННОЇ МЕРЕЖІ ДЛЯ ОБРОБЛЕННЯ СИГНАЛІВ З АМПЛІТУДНОЮ МОДУЛЯЦІЄЮ БАГАТЬОХ СКЛАДОВИХ

The processing of radio signals using artificial neural networks (ANNs) has great potential for research, which can be explained by the adaptability of ANNs to various transmission conditions and the ability to detect abstract patterns of changes in signal parameters. The article reviews the works of other authors devoted to different ways of using ANNs for processing radio signals. Taking into account the information in the reviewed works, the research task was formed, which consists in developing an optimized ANN model for radio signal processing. Signals with amplitude modulation of many components (AMMC) were chosen to form training samples for ANN. The choice of modulation type is justified by greater energy efficiency compared to other widely used digital modulation types, such as quadrature amplitude modulation. Mathematic basis of AMMC signal generation is described. The process of finding the coordinates of three component 8-AMMC signal constellation is explained, the formation of signals in the time plane based on the found coordinates is explained as well as their discretization and the addition of white noise. An iterative algorithm for generating initial data for ANN based on the described ratios is proposed. The general structure of one-dimensional convolutional neural network is considered. Functions of individual neurons, connections between them, the formation of layers and the convolution operation are described mathematically. On the basis of the previously given ratios, a final display of the network was formed. Specific dimensions and activation functions for layers are selected. The use of convolutional layers is justified by time invariance. Based on the reviewed mathematical models, selected activation functions and dimensions, a neural model was formed. The process of validating the effectiveness of the formed neural model is described, which is based on comparing the symbolic error probabilities of the proposed and reference models at different signal-to-noise ratios. The validation results are presented. The advantages of the obtained model over the previously proposed purely recurrent model and the AMMC reference receiver are explained.

Enhanced voice over 5G transmission with unequal error protection and generative adversarial networks

SummaryVoice services have progressed significantly since the launch of mobile phones and have evolved from analog technology to digital ones. Since the launch of 5G, voice over 5G (Vo5G) will slowly take over legacy mobile technologies to provide better voice services. Nevertheless, interruptions and noise will continue to affect speech communication over wireless networks, ensuing in a reduced Quality of Service (QoS). Three enhanced transmission schemes for Vo5G are proposed. The first proposal benefits from the difference in weight of the bits of internet Low Bitrate Code (iLBC) coded packets to offer them diverse degrees of protection i.e. Unequal Error Protection (UEP). UEP enhances the reception quality by allowing the more significant bits to be decoded with greater reliability during 5G transmission. The second and third schemes substitute the usual Quadrature Amplitude Modulation (QAM) constellation with a Statistical QAM (SQAM) one. The second scheme arranges the significant bits on the SQAM constellation and the remaining bits onto the conventional QAM arrangement. For the third scheme, all the bits are arranged on the SQAM constellation. Generative Adversarial Networks (GAN) were incorporated into the third scheme as the third scheme provided better gains over the first and second schemes. GAN was used to synthesize and enhance parts of the speech file that were lost during transmission over the 5G channel resulting in a gain in Segmented Signal to Noise Ratio (SSNR). The addition of GAN boosted the gain obtained by the third scheme by 1.45 dB with 16‐QAM at a code rate of 1/3.

Alamouti-coded DSP algorithm with a simplified PTBC decoder for next-generation optical access networks

The use of Alamouti-coded polarization-time block code (A-PTBC) in combination with a simple single polarization coherent receiver enables phase-diverse coherent detection without any optical polarization tracking. However, applying this technique to high-speed single-carrier systems is not straightforward, as it requires specialized digital signal processing (DSP) algorithms for data recovery, which increases DSP complexity. In this paper, we propose a novel Alamouti-coded coherent algorithm designed to significantly reduce the complexity of the receiver DSP for data recovery. The proposed algorithm achieves the comparable performance to the conventional algorithm but requires only half the number of necessary equalizers for data recovery. We validate its performance through simulations and also experimentally demonstrate a 100 Gb/s 16-quadrature amplitude modulation (QAM) single-carrier coherent system employed the single-polarization coherent receiver over 20 km of standard single-mode fiber (SMF). Through the performance verification, the coherent system with the proposed algorithm exhibits performance comparable to that of the conventional Alamouti-coded coherent system and achieves a power budget of 34 dB when the transmit launch power is set to 7 dBm at a Bit Error Rate (BER) of 1 × 10−2 for 0-20 km fiber transmission.

Comparative analysis of coding schemes for effective wireless communication

Communication systems have recently focused on sending information efficiently and effectively from one sending point to another across a communication channel in the shortest amount of time. The main objective of this work is to compare the high-range coding scheme types, such as low density parity check (LDPC), turbo, and convolution, to see which works better and is more efficient. to establish a coding system with quadrature amplitude modulation (QAM) modulation and an additive white gaussian noise (AWGN) noisy channel to find which is more reliable and resilient for encoding and decoding. Because of this, digital media has to be sent over wireless channels and through satellites, requiring a connected network all the time, which has become a major concern over time. Furthermore, the high amount of data and efficiency are the focus points. After running the simulation, it was found that 64 QAM with a rate of 0.455 and an efficiency of 2.731 has a bit error rate (BER) of 0.001 and a 7.08 dB energy per bit Eb/No, and the 256 QAM simulation revealed that it has a BER of 0.001 and 11.88 dB Eb/No with a rate of 0.736 and an efficiency of 5.891. Over the AWGN channel noise, the simulation built a standard orthogonal frequency division multiplexing (OFDM) system, which used MATLAB.

A Single-Board Integrated Millimeter-Wave Asymmetric Full-Digital Beamforming Array for B5G/6G Applications

In this article, a single-board integrated millimeter-wave (mm-Wave) asymmetric full-digital beamforming (AFDBF) array is developed for beyond-fifth-generation (B5G) and sixth-generation (6G) communications. The proposed integrated array effectively addresses the challenge of arranging a large number of ports in a full-digital array by designing vertical connections in a three-dimensional space and successfully integrating full-digital transmitting (Tx) and receiving (Rx) arrays independently in a single board. Unlike the traditional symmetric array, the proposed asymmetric array is composed of an 8 × 8 Tx array arranged in a square shape and an 8 + 8 Rx array arranged in an L shape. The center-to-center distance between two adjacent elements is 0.54λ0 for both the Tx and Rx arrays, where λ0 is the free-space wavelength at 27 GHz. The proposed AFDBF array possesses a more compact structure and lower system hardware cost and power consumption compared with conventional brick-type full-digital arrays. In addition, the energy efficiency of the proposed AFDBF array outperforms that of a hybrid beamforming array. The measurement results indicate that the operating frequency band of the proposed array is 24.25–29.50 GHz. An eight-element linear array within the Tx array can achieve a scanning angle ranging from −47° to +47° in both the azimuth and the elevation planes, and the measured scanning range of each eight-element Rx array is –45° to +45°. The measured maximum effective isotropic radiated power (EIRP) of the eight-element Tx array is 43.2 dBm at 28.0 GHz (considering the saturation point). Furthermore, the measured error vector magnitude (EVM) is less than 3% when 64-quadrature amplitude modulation (QAM) waveforms are used.

Rate 5/6 TCM Code Having 64 States with 64 QAM for Fading Channel

Trellis Coded Modulation (TCM) is powerful technique employed in digital communication systems to improve the reliability and efficiency of data transmission. TCM combines error control coding and modulation schemes to achieve superior performance in challenging channel conditions. In TCM, information bits are encoded using a trellis encoder, which generates a sequence of encoded symbols. These symbols are then mapped onto a modulation scheme, such as Quadrature Amplitude Modulation (QAM) or Phase Shift Keying (PSK), to create the modulated signal. At the receiver, the received signal is demodulated and decoded using a trellis decoder, which employs maximum likelihood decoding to recover the original information bits. The trellis structure allows for efficient error correction and makes TCM particularly suitable for channels with fading, noise, and other impairments. TCM has been widely used in various communication standards and applications to enhance data transmission reliability and spectral efficiency. TCM is a coding technique that merges coding and modulation to attain substantial coding gain without compromising bandwidth efficiency. The emergence of TCM occurred in the late 1970s, and ever since, it has found extensive utilization in various contemporary information transmission systems. In this paper, a new methodology is introduced for the design of a 64-state rate 5/6 TCM code optimized for fading channels. The outcomes obtained from the study are remarkably encouraging, demonstrating coding gain of around 10 dB in comparison to uncoded 32 PSK. This substantial gain plays a pivotal role in boosting data rates, especially in situations where bandwidth-limited channels are involved.

A Novel 4 × 1 MISO-VLC System with FBMC-OQAM Downlink Signals

A novel visible-light communication (VLC) system with 4 × 1 multi-input–single-output (MISO) channels is designed. In the system, the filter bank multicarrier (FBMC) and offset quadrature amplitude modulation (OQAM) techniques are used to generate downlink signals. The principles and implementation methods are proposed and analyzed, and the light intensity and received light power distribution of four LED emitters are discussed. The results demonstrate that it not only satisfies the requirements of indoor information access but also provides daily lighting. The used FBMC-OQAM signals exhibit better reception performance than orthogonal frequency division multiplexing (OFDM) signals. The system used has a lower bit error rate (BER) and larger access bandwidth compared to a 1 × 1 single-input–single-output (SISO) system. It has the potential for application advantages in future indoor VLC system applications.

Channel estimation techniques based on intrinsic interference mitigation for FBMC/OQAM systems

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) emerges as a noteworthy alternative to orthogonal frequency division multiplexing (OFDM). FBMC/OQAM addresses the limitations of OFDM by utilizing real-valued, even-symmetrical prototype filters with smaller side lobes and faster spectrum decay. This results in lower out-of-band energy and higher spectral efficiency (SE). However, the orthogonality condition of FBMC/OQAM in the real domain introduces an intrinsic interference (II) component that poses challenges for channel estimation (CE). The conventional straightforward OFDM CE techniques cannot be applied directly. To obtain a precise CSI with the FBMC/OQAM system, Kalman filter (KF) is altered and incorporated into the use of AP and coding. The first proposed method, KalCod, employs a data spreading method to diminish the II effect. The simulation results indicate that KalCod has a superior capacity to the other CE methods, while still maintaining a reasonable level of complexity. In the second proposed method, modified Kalman-auxiliary pilot (KAP), an AP is used to eliminate the II at pilot symbols then updating the channel coefficients using modified KF. When used as a CE method for FBMC/OQAM systems, the modified KAP outperforms its competitors in terms of estimation accuracy, simpler implementation, as well as higher throughput and spectral efficiency.

Dynamics of multicavity hyperchaotic maps with rotational control operation and its applications

To provide more complex and random chaotic maps to applications and algorithms, we propose a boundary coupled modulation (BCM) model. By introducing the rotation-matrix (ROT), the corresponding rotation boundary coupled modulation (RBCM) model are constructed, and a series of hyperchaotic maps are generated with various attractors and numerous fixed points. The shape and size of the multicavity can be adjusted by controlling the parameters. Interestingly, RBCM maps are controlled by changing rotation coefficients (Rot-C, d, e, and θ), which can rotate the attractor of the enhanced BCM at any angle and direction. RBCM maps produce a more uniform topological space, and have multiple pairs of symmetric coexisting attractors. The BCM and RBCM maps exhibit rich dynamical behaviors, high complexity, and strong randomness.To verify the engineering practicability, we apply the BCM and RBCM maps to design pseudo-random number generators (PRNG), and test it with NIST, quadrature amplitude modulation (QAM) system. Finally, the FPGA implementation of the proposed chaotic map verifies.

Evaluating Puncture and Non-puncture for the Turbo Code Model based the on AWGN Channel with 16-QAM

In general, a 5G new radio network is defined by three primary utilization situations, namely upgraded versatile broadband, ultra-reliable, and low latency interchanges of information, as well as huge machine-type correspondences. These utilizations require improved throughput, inertness, dependability contrasted, and a 4G framework. As a coding plan for information, 5G Turbo codes attain high throughput, a variable code rate, and length, and crossover programmed rehash with good error-detecting capability. The execution boundaries of 5G advancements are normal and are tens and thousands of times better compared with 4G. In this paper, the evaluations of puncturing and non-puncturing for turbo code depending on the minimization of penetrating of efficient pieces are discussed. It also provides penetrating of equality pieces considering additive white Gaussian noise (AWGN) Channel with 16 quadrature amplitude modulation (QAM) to attain high spectral efficiency. In addition to this, the super encoder encodes the separated progression with a code speed of 1/3. The code block association progressively connects the yields from the super encoder. The sign mapper employed in this paper adjusts the progression using a 16-QAM balance. Also, the mapper takes effective pieces, one uniformity bit from the upper encoder, and the deinterleaved equity bit from the base encoder. The Orthogonal frequency-division multiplexing (OFDM) mapper parts into more modest equivalent channels, named subcarriers and the information is sent on these equivalent channels at a reduced rate.

Joint signal-to-signal beat interference mitigation for the field recovery of symmetric carrier-assisted differential detection with low carrier-to-signal power ratio

Joint signal-to-signal beat interference mitigation for the field recovery of symmetric carrier-assisted differential detection with low carrier-to-signal power ratio

Integrated segmented IQ-modulator for orthogonal sampling and multi-level high-bandwidth signal generation.

Photonic-assisted signal processing of high-bandwidth signals emerges as a solution for challenges encountered in electronic-based processing. Here we present a concept for a compact, photonic-assisted digital-to-analog converter (DAC) and optical IQ-modulator in one single integrated device based on two innovative concepts: a segmented Mach-Zehnder modulator and orthogonal sampling. For electrically driving the modulator, only a single radio frequency oscillator and no pulse source or electrical DAC are required. The presented and simulated proof-of-concept device with six segments can generate a multi-level and high-bandwidth signal from low-bandwidth electronic drivers; e.g., we show the generation of a 120 Gbps data rate, 16-quadrature amplitude modulation (16-QAM, 30 Gbaud) signal solely based on low-bandwidth (5 GHz) non-return-to-zero (NRZ) signals. Integrated on a silicon photonic platform, the device provides fixable speed and bandwidth operations, positioning it as a viable solution for diverse communication systems.

Experimental demonstration of flexible information rate PON beyond 100 Gb/s with rate-compatible LDPC codes

The applications of rate-compatible low-density parity-check (RC-LDPC) codes are investigated for a 16 quadrature amplitude modulation (16QAM) signal and coherent detection system. With rate-compatible signals, we can provide the flexible net data rate between 135.5 Gb/s and 169.7 Gb/s in a passive optical network (PON) link. Based on the LDPC codes defined in the IEEE 802.3ca standard, we construct two sets of RC-LDPC codes with a fixed and variable information bit length. Since the puncturing operation may degrade the performance of LDPC codes, we apply the protograph-based extrinsic information transfer (PEXIT) technique to optimize the puncturing positions to mitigate the degradation. Additionally, we explore four low-complexity LDPC decoding algorithms (min sum, offset min sum, variable weight min sum, and relaxed min sum with 2 nd min emulation) to investigate the relationship between the computational complexity and decoding performance. Simulation results indicate that the constructed codewords exhibit good performance in the waterfall region across a range of code rates. Finally, we conduct an experimental setup in a dual-polarization 25 GBaud 16QAM coherent PON to verify the effectiveness of the constructed LDPC codes with four decoding algorithms. The experimental results show maximal 4.8 dB receiver sensitivity differences, which demonstrate the feasibility of the method for constructing RC-LDPC codes in future high-speed flexible coherent PON.

Nonlinear-tolerant two-dimensional distribution matcher scheme for probabilistic shaping.

This Letter proposes a nonlinear-tolerant two-dimensional distribution matcher (2D-DM) scheme. It removes the corner points of probabilistically shaped quadrature amplitude modulation (QAM) to obtain better nonlinear tolerance. Because the remaining number of points is not a power of 2, we propose to divide constellation points into different layers and symbols. Then, the proposed 2D-DM performs matching using one-dimensional shapers, which generates the in-phase and quadrature components of QAM together. In fact, it realizes two-dimensional shapers from one-dimensional shapers. Simulation results show that two-dimensional shapers generated by the proposed 2D-DM have higher tolerance to power amplifier nonlinearity and fiber nonlinearity compared to one-dimensional shapers.

Extending the reach of multi-core fiber via Voronoi constellations with concatenated multilevel coding.

This Letter proposes a novel, to the best of our knowledge, coded modulation scheme for randomly coupled multi-core fiber (RC-MCF) via multidimensional (MD) constellation with concatenated two-level multilevel coding (MLC). In the proposed system, the 16-dimensional (16D) Voronoi constellation (VC), naturally fitting with the 16 degrees of freedom of a four-core fiber (two quadratures, two polarizations, and four cores), is generated by a latticed-based shaping method to provide higher shaping gains. Moreover, combining it with the concatenated two-level MLC can further achieve better performance-complexity trade-off. It is demonstrated by simulation results of long-haul multi-channel RC-MCF transmission that the proposed coded modulation scheme for four-core fiber transmission offers 77% reduction in the number of decoding operations and up to 21% (585 km) reach increase over the conventional bit-interleaved coded modulation scheme for quadrature amplitude modulation.

Dual high-order QAM-modulated mm-wave signal transmission in the Q-band enabled by simple IM/DD architecture and bandpass delta-sigma modulation.

The intensity-modulation (IM)/direct-detection (DD) systems have been proven effective and low-cost due to their simple system architecture. However, the Mach-Zehnder modulator (MZM) of the IM/DD systems only reserves its driving signal intensity. Therefore, the IM/DD systems are generally unable to transmit vector signals and have a restricted spectrum efficiency and channel capacity. Similarly, the radio-over-fiber (RoF) transmission systems based on IM/DD are limited by their simple architecture and generally cannot transmit high-order quadrature amplitude modulation (QAM) signals, which hinders the improvement of their spectrum efficiency. To address the challenges, we propose a novel, to the best of our knowledge, scheme to simultaneously transmit the dual independent high-order QAM-modulated millimeter-wave (mm-wave) signals in the RoF system with a simple IM/DD architecture, enabled by precoding-based optical carrier suppression (OCS) modulation and bandpass delta-sigma modulation (BP-DSM). The dual independent signals can carry different information, which increases channel capacity and improves spectrum efficiency and system flexibility. Based on our proposed scheme, we experimentally demonstrate the dual 512-QAM mm-wave signal transmission in the Q-band (33-50 GHz) under three different scenarios: 1) dual single-carrier (SC) signal transmission, 2) dual orthogonal-frequency-division-multiplexing (OFDM) signal transmission, and 3) hybrid SC and OFDM signal transmission. We achieve high-fidelity transmission of dual 512-QAM vector signals over a 5 km single-mode fiber (SMF) and a 1-m single-input single-output (SISO) wireless link operating in the Q-band, with the bit error rates (BERs) of all three scenarios below the hard decision forward error correction (HD-FEC) threshold of 3.8 × 10-3. To the best of our knowledge, this is the first time dual high-order QAM-modulated mm-wave signal transmission has been achieved in a RoF system with a simple IM/DD architecture.

A hybrid detection algorithm for 5G OTFS waveform for 64 and 256 QAM with Rayleigh and Rician channels

Abstract Signal detection in orthogonal time frequency space modulation is one of the critical aspects for enhancing the throughput of the beyond fifth-generation framework, especially in challenging environments characterized by high mobility and multipath propagation. In this work, we proposed a hybrid detection algorithm by combining zero-forcing equalization (ZFE) and minimum square error equalization (MMSE), also known as ZFE–MMSE, with Rician and Rayleigh channels for 64 and 256 quadrature amplitude modulation. The combination of ZFE and MMSE allows for a more comprehensive approach to equalization. ZFE addresses channel-induced distortions, while MMSE tackles the impact of noise. Together, they enhance the overall performance of the equalization process, resulting in improved signal detection accuracy. The analysis and comparison of the simulation parameters with traditional detection systems include bit error rate, power spectral density (PSD), and complexity. The projected algorithms achieve a signal-to-noise ratio and a PSD gain of 2 dB and −800, respectively, outperforming the traditional detection techniques.

Performance analysis of energy harvesting‐enabled relay networks in κ‐μ fading channels

AbstractIn this paper, we investigate the performance of an energy harvesting (EH)‐enabled multiple relay network operating over generalized ‐ fading channels. Our approach involves utilizing a partial relay selection strategy and employing an amplify and forward relay protocol for efficient EH from RF signals. Additionally, we integrate a selection combining scheme at the receiver to combine both direct and relaying path signals. In our research, we first obtain the exact closed‐form expression of the cumulative distribution function (CDF) for the system under investigation. Subsequently, we derive expressions for the outage probability (OP) and the moment generating function (MGF) using the derived CDF expression. Furthermore, with the assistance of a CDF‐based approach, we derive closed‐form expressions for the average symbol error rate (ASER) for coherent quadrature amplitude modulation (QAM) schemes, including rectangular QAM (RQAM) and hexagonal QAM (HQAM). We also analyze the ASER expression for non‐coherent frequency shift keying (NCFSK), leveraging the derived MGF expression. To gain valuable insights into the performance of EH‐enabled multiple relay networks, we assess the asymptotic expression of the OP. The outcomes indicate how the behavior of the system is affected by various factors such as time switching ratio, channel fading components, number of relays, and the distance between nodes. To corroborate the accuracy of the analytical findings, Monte Carlo simulations are executed.

Enhancing the performance of LiFi communication with OSTBC, QAM, and OFDM: High-capacity, low-complexity transceiver design

Light fidelity (LiFi) is one of the most promising areas within wireless optical communication system. It provides many benefits, including high capacity, improved security and enhanced cost-effectiveness. However, there is still challenges which are link blockages, attenuation, interference and bandwidth restriction of modulation techniques. Orthogonal space–time block coding (OSTBC) offers a suitable solution to address link blockage by providing an alternative communication channel between the transmitter and the receiver. OSTBC has more tolerate to the practical channel impact limitation such as attenuation and interference that may occur in overlapping regions. In addition, the use of the OSTBC technique enhances the system’s ability to transfer data as the transmission rate is duplicated by the number of transmitters and receivers. This paper proposes the utilisation of a LiFi transceiver-based OSTBC that employs quadrature amplitude modulation (QAM) in conjunction with orthogonal frequency-division multiplexing (OFDM). Co-simulation tools have been done by integrated Matlab with Optisystem, were used in the design of LiFi transceiver with all assumption required. The findings reveal the capability of LiFi transceiver of transmitting rate up to 15 Gbps with maintaining a satisfactory bit error rate (BER) of 10−4 over a link range of 200 m evenin the presence of realistic channel effects. Moreover, the LiFi transceiver’s structure used does not incorporate optical amplifier components, resulting in reduced computational complexity compared to conventional LiFi transceivers. The proposed system proved its progress over the previous work under the influence of the same input effects.

Broadband electro-optic chaotic system using coupling mutual feedback for intensity and phase chaos generation

An innovative dual-coupled dispersive electro-optic chaotic system utilizing two interlinked nonlinear feedback loops is introduced and demonstrated experimentally. This system efficiently converts phase chaos into intensity chaos while incorporating dispersion, achieved by integrating a broadband chirped fiber Bragg grating (CFBG) into a dual-loop opto-electronic oscillator (OEO) system. Consequently, this leads to the generation of broadband intensity and phase chaos with heightened complexity. Experimental findings indicate that the system achieved up to 24 GHz of 80% bandwidth and 35.5 GHz of 10 dB bandwidth for intensity chaos carriers, and up to 26 GHz of bandwidth with 40.52 GHz of 10 dB bandwidth for phase chaos carriers. The approach features a straightforward structure and mitigates delay characteristics inherently within the system itself. This two-dimensional chaotic source presents potential for secure communications in high-speed Quadrature Amplitude Modulation (QAM) systems.