Constellation Mapping Research Articles

Enhanced 4D-OFDM optical communication systems with color-coded constellations and probability constellation shaping.

The present work introduces a four-dimensional probability constellation mapping OFDM optical transmission system based on a two-dimensional inverse fast Fourier transform (2D-IFFT). A four-dimensional constellation structure employing color coding is designed, amalgamating geometric shaping with probability shaping to enhance the constellation figure of merit (CFM). Successful transmission of OFDM signals at 51.49 Gb/s is achieved over a 2 km seven-core optical fiber, validating the performance of the proposed constellation diagram. Under the conditions of multicore multiplexing and a bit error rate of 3.8 × 10-3, the receiver sensitivity of the OFDM signals mapped with the proposed color-coded four-dimensional constellation exhibits gains of 0.8 dB, 1.33 dB, and 1.83 dB compared to traditional four-dimensional constellations, 3D-OFDM, and 2D-OFDM modulation, respectively. Furthermore, under an entropy value of 4.4 bits/symbol, a receiver sensitivity gain of 1.36 dB is attained compared to a uniform distribution constellation, indicating the favorable error performance of this scheme with promising prospects for short-distance communication in the future.

Performance enhancement with geometrically shaped 4/8D-SP-50QAM for DDO-OFDM system

We design the 4-dimensional set-partitioning 50-ary quadrature amplitude modulation (4D-SP-50QAM) and 8D-SP-50QAM with 7 bit/symbol in direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems. Quadrant multiplexing (QM) and orthant symmetry (OS) are respectively used to reduce the number of constellation points and the complexity of constellation mapping, while improving system bandwidth utilization. The proposed 8D-SP-50QAM scheme outperforms 4D-SP-50QAM, 4D-OS-64QAM and 4D 128-ary polarization-ring-switching (4D-128PRS) in terms of generalized mutual information (GMI) and bit error rate (BER) performance at various fiber length. In addition, the GMI gain increases gradually with the increase of fiber length, proving that this scheme can effectively improve system capacity and nonlinear tolerance.

High-security space division multiplexing optical transmission scheme based on constellation grid selective twisting

In this paper, we propose a high-security space division multiplexing optical transmission scheme based on constellation grid selective twisting, which adopts the Rossler chaos model for encrypting PDM-16QAM signals, being applied to a multicore, few-mode multiplexing system. The bitstream of the program is passed through XOR function before performing constellation grid selective twisting and rotation of the constellation map to improve the security of the system. The proposed system is verified experimentally by using 80-wave and 4-mode multiplexing in one of the 19-core 4-mode fibers. Based on the proposed encryption method, a net transmission rate of 34.13 Tbit/s, a transmission distance of 6000 km, and a capacity distance product of 204.8 Pb/s × km is achieved under encrypted PDM-QPSK modulation. Likewise, a net transmission rate of 68.27 Tbit/s, a transmission distance of 1000 km, and a capacity distance product of 68.27 Pb/s × km is achieved based on encrypted PDM-16QAM modulation. It is experimentally verified that the sensitivity of the initial value in Rossler's chaotic model is in the range of 10−16∼10−17. Meanwhile, the proposed encryption scheme achieves a large key space of 10101, which is compatible with the high-capacity distance product multicore and few-mode multiplexing system. It is a promising candidate for the next-generation highly-secured high-capacity transmission system.

High-security multidimensional data protection system based on the Hartley algorithm-driven chaotic scheme

This paper proposes a high-security multidimensional data protection system based on the Hartley algorithm-driven chaotic scheme. We utilize the fast Hartley algorithm instead of the fast fourier computation, and we employ chaotic sequences generated by the multi-winged chaotic system to achieve chaos-driven 3D constellation mapping, effectively integrating the chaotic system with the stochastic amplitude modulator. We reduce the signal’s peak-to-average power ratio (PAPR) by deploying a random amplitude modulator. Simultaneously, this approach enhances the security of the physical layer of the signal. The PAPR reduction can reach up to 2.6 dB, while the most robust and stable modulator scheme can gain 2 dB. Finally, in the Hartley frequency domain, the signal's frequency is disrupted, providing the entire system with a key space of 10131 to resist violent cracking and thus improving the system's overall security. To validate the feasibility of our scheme in comparison to conventional IFFT-based encrypted 3D orthogonal frequency division multiplexing, We achieved a transmission rate of 27.94 Gb/s over a 2 km multicore fiber. Experimental results show that since the random amplitude generator effectively reduces PAPR, our proposed encryption scheme increases the forward error correction threshold range by 1.1 dB, verifying that our proposed scheme has highly reliable security performance.

Secure high-density constellation mapping OTFS modulation scheme with low PAPR

In this paper, a secure orthogonal time-frequency space (OTFS) modulation transmission system based on 3D dense constellation mapping (DCM) geometric shaping is proposed, and a selective reduction amplitude algorithm (SRA) for DCM to reduce peak average power ratio (PAPR) is presented. The DCM is based on regular tetrahedron construction to improve its space utilization efficiency. The proposed SRA involves reducing high PAPRs transmitter and restoring them at the receiving end, which only requires an additional 0.57% of the total transmission capacity. The algorithm reduces PAPR while ensuring the bit error rate performance of the system, so it is suitable for systems that need to process large amounts of transmitted data quickly. By verifying the actual transmission performance on a 2 km of 7-core optical fiber transmission system, the optical transmission with a bit rate of 33.93Gb/s is achieved. The experimental results show that when the bit error rate (BER) reaches the 3.8×10−3 threshold, the OTFS system using DCM and SRA could improve the receiver sensitivity by 3.7 dB compared with the OTFS system using concentric cube mapping and SRA, and 2.7 dB compared with the OFDM system using DCM. After adding the SRA, the PAPR of the OTFS system is reduced by more than 2.2 dB. When the received optical power reaches near the bit error rate threshold, the SRA valid data can be fully recovered by optimizing the SRA.

Research on Low-Density Parity-Check Decoding Algorithm for Reliable Transmission in Satellite Communications

Satellite communications face difficulties such as intensified environmental attenuation, dynamic time-varying links, and diverse business scenarios, which usually require channel coding schemes with high coding gain and high throughput. Low-density parity-check (LDPC) codes are dominant in satellite communication coding schemes due to their excellent performance in approaching the Shannon limit and the characteristics of parallel computing. The traditional weighted-Algorithm B decoding algorithm ignores the channel received information and involves frequent multiplication operations and iteration, which introduces the channel received information for hard-decision and constellation mapping processing. Meanwhile, we design the correlated reliability between the extrinsic information and the mapping processing information to improve the correctness of decoding. The multiplication operation in the iterative process can be replaced by the simple sum of the Hamming distance coefficient, the correlated reliability between the extrinsic information and the mapping processing information, and the extrinsic information frequency, thereby reducing the complexity and storage load of the system. The simulation results show that the presented MRAI-LDPC algorithm can obtain about 0.4 dB performance gain, and the average number of iterations is reduced by 68% under a low SNR. The algorithm can achieve better error-correcting performance and higher throughput, providing strong support for reliable transmission of satellite communications.

A new constellation mapping for PAPR reduction in OCDM without side information

A new constellation mapping for PAPR reduction in OCDM without side information

A Constellation Diagram Learning-Based Adaptive Sparse Nonorthogonal Wavelet Division Multiplexing for Sonar Image Underwater Acoustic Transmission

In underwater Internet of Things (IoT) applications, efficient and reliable transmission is demanding. Recently, the non-orthogonal multicarrier (MC) modulation is utilized as a promising spectrum-efficient solution in the UWA channel, where generally, the constellation mapping (CM) methods (such as 8-PSK and 16-QAM) are utilized to further increase the transmission rate. In this paper, we focus on the transmission of sonar images among IoT nodes and a constellation diagram learning-based adaptive sparse non-orthogonal wavelet division multiplexing (CDLA-SNOWDM) system is proposed to combat complex channel states between IoT nodes. We found that different CM methods contribute to unique time-frequency characteristics in constellation diagrams. We first utilize the time-frequency characteristics in designing the non-orthogonal subcarriers. The complex-valued CM signals are regarded as a new type of image. We introduce dictionary learning (DL) to non-orthogonal subcarrier designing, with the idea that designing CM signal adaptive non-orthogonal subcarriers can be regarded as designing an adaptive subcarrier dictionary. The CDLA-SNOWDM modulation is performed as a projection of the CM image to the subcarriers with an adaptive dictionary. The learned adaptive subcarriers can represent constellation diagrams more efficiently and improve transmission reliability. Both simulations and experiments show that the proposed scheme improved the reliability in transmitting sonar images over other orthogonal and non-orthogonal modulation schemes in UWA scenarios.

OCDM-SDM Optical Communication System Utilizing Four-Dimensional Constellation Mapping

In this paper, an orthogonal chirp division multiplexing (OCDM) Space division multiplexing (SDM) optical communication utilizing four-dimensional constellation mapping is proposed. A new 16-point four-dimensional constellation is designed, and its constellation figure of merit (CFM) can reach 1.17. A direct detection orthogonal chirp division multiplexing (DD-OCDM) transmission scheme based on four-dimensional constellation mapping is designed, and 32.8 Gb/s OCDM signal transmission is performed across 2 km seven core fiber through experiments, which verifies the performance of the proposed constellation. Under the condition of multi-core multiplexing and the bit error rate (BER) of 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , the receiver sensitivity of the OCDM signal, which is based on the proposed four-dimensional constellation mapping based on associated constellation mapping (16ACM-4D), has a gain of 0.59 dB, 3.26 dB, and 5.73 dB compared with the OCDM signals based on QPSK, 16QAM, and 16PSK, respectively. The results show that the proposed OCDM short-reach optical communication scheme based on four-dimensional constellation mapping has good bit error performance and anti-interference ability, and has broad application prospects in the future short-reach optical communication.

3D PCDM Probabilistic Shaping Transmission Scheme Based on Chaotic Constellation Mapping

3D PCDM Probabilistic Shaping Transmission Scheme Based on Chaotic Constellation Mapping

Performance analysis of spectrally shaped DDO-OFDM based on nonlinear differential coding and real-valued precoding

This paper presents a cost-effective spectrally shaped quadrature amplitude modulation (SS-QAM) signal in bandwidth limited direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems. The concatenation of the nonlinear differential coding (NLDC) and real-valued precoding sequentially implements spectral-shaping and multi-carrier modulation. Real-value discrete cosine transform (DCT) and discrete Hartley transform (DHT) are used to realize the uniform distribution of the fluctuation signal-to-noise ratio (SNR) and reduce the peak-to-average power ratio (PAPR). To broaden the flexibility of constellation mapping and improve the fine granularity of signals, six modulation formats are analyzed and evaluated in DDO-OFDM systems. Results show that SS-QAM is superior to uniformly distributed QAM in terms of reducing bit error rate (BER) and increasing normalized generalized mutual information (NGMI). Compared to the uniform 25/36/49/64/81/100 QAM OFDM signal, when the transmission distance is 20 km, SS-25/36/49 QAM signal can achieve error free transmission and SS-64/81/100 QAM can achieve 0.9971/1.0037/1.0255 Q-factor improvement and 0.0009/0.0014/0.0015 NGMI gain. When the transmission distance is 50 km, SS-25/36/49/64/81/100 QAM can achieve 0.4182/0.5169/0.9311/0.9988/1.0216/1.1487 Q-factor improvement and 0.0004/0.0008/0.0031/0.0043/0.0066/0.0083 NGMI gain. When the transmission distance is 80 km, SS-25/36/49/64/81/100 QAM can achieve 0.4754/0.7486/1.181/1.2012/1.2302/1.3904 Q-factor improvement and 0.0015/0.0046/0.0108/0.0152/0.0172/0.0205 NGMI gain. In addition, the Q-factor and NGMI gain increases as the fiber length increases, which verifies that the presented scheme is robust to the nonlinear effect.

Multi-carrier based positional modulation design with discrete phase values for metasurface elements

Positional modulation (PM) as an extension of directional modulation (DM) can transmit information to the desired position(s) with known constellation mappings, but with scrambled ones in other areas. In this paper, a multi-carrier based PM design is proposed with practical discrete phase values for the employed reconfigurable metasurface, where multiple signals can be transmitted to the desired position(s) at multiple frequencies over a single channel simultaneously, and the traditional narrowband single-carrier transmission can be considered as a special case. Design examples for both the single-carrier and multi-carrier cases are provided to show the effectiveness of the proposed design.

Modulation Format Identification and OSNR Monitoring Based on Multi-Feature Fusion Network

In this paper, we propose a multi-feature fusion network (MFF-Net) for a modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring scheme. The constellation map data used in this work comes from five modulation formats, namely 56 Gbit/s 4/8 phase shift keying (PSK) and 16/32/64 quadrature amplitude modulation (QAM). The constellation maps are input to one branch network of the MFF-Net, and then the constellation maps are processed by horizontal projection and used as input to another branch network as a way to fuse the two image features. The results show that the scheme achieves 100% MFI accuracy and 98.82% OSNR monitoring accuracy for the five modulation formats. In addition, the performance of MFF-Net and binarized convolutional neural network (B-CNN), visual geometry group network (VGG-Net), and traditional weighted multi-task learning (EW-MTL) are compared to present the superiority of the method. The effect of model structure on MFF-Net is also discussed. The robustness of the model is also evaluated for different transmission distances and bit rates.

Research and implementation of modulation recognition based on cascaded feature fusion

AbstractAiming at the problems of weak robustness of single feature and limited recognition range in modulation recognition, this paper proposes a modulation recognition algorithm based on cascaded feature fusion and multi‐classifier combination, in which time‐frequency map and instantaneous amplitude spectral density features are extracted from low intermediate frequency (IF) signal, constellation map and high‐order cumulant features are extracted from zero IF signal, and a three‐level recognition algorithm is designed through the decision fusion of decision tree, convolutional neural network, and support vector machine. In order to verify the performance of the algorithm, a modulation recognition system is designed and built based on USRP2974. The low IF and zero IF modulation signals are received through two channels, and the RF signals are received and processed in real time with the help of the built‐in CPU of the receiver. The recognition of 13 kinds of analog modulation and digital modulation signals is realized. Under the condition of wireless reception, the recognition rate of this system is more than 93% at 5 to 10 dB.

Performance improvement of non-orthogonal multiple access with a 3D constellation and a 2D IFFT modulator.

In this paper, we propose a performance improvement of non-orthogonal multiple access (NOMA) with a three-dimensional (3D) constellation and a two-dimensional Inverse Fast Fourier Transform IFFT modulator (2D-IFFT) for the passive optical network (PON). Two kinds of 3D constellation mapping are designed for the generation of a three-dimensional NOMA (3D-NOMA) signal. Higher-order 3D modulation signals can be obtained by superimposing signals of different power levels by pair mapping. Successive interference cancellation (SIC) algorithm is implemented at the receiver to remove interference from different users. Compared with the traditional two-dimensional NOMA (2D-NOMA), the proposed 3D-NOMA can increase the minimum Euclidean distance (MED) of constellation points by 15.48%, which enhances the bit error rate (BER) performance of the NOMA. The peak-to-average power ratio (PAPR) of NOMA can be reduced by 2 dB. A 12.17 Gb/s 3D-NOMA transmission over 25 km single-mode fiber (SMF) is experimentally demonstrated. The results show that at the bit error rate (BER) of 3.8 × 10-3, the sensitivity gain of the high-power signals of the two proposed 3D-NOMA schemes is 0.7 dB and 1 dB compared with that of 2D-NOMA under the condition of the same rate. Low-power level signal also has 0.3 dB and 1 dB performance improvement. Compared with 3D orthogonal frequency-division multiplexing (3D-OFDM), the proposed 3D-NOMA scheme could potentially expand the number of users without obvious performance degradation. Due to its good performance, 3D-NOMA is a potential method for future optical access systems.

SER Optimization in OFDM-IM Systems with Nonlinear Power Amplifiers

Power amplifiers (PAs) lead to nonlinear distortion in index modulation assisted OFDM (OFDM-IM) systems when the peak-to-average power ratio (PAPR) is high. But PAPR reduction in OFDM-IM is more complicated than that in traditional OFDM owing to the frequent switch of subcarrier states between active and idle. When implementing OFDM-IM on resource-limited platforms like battery-powered Internet of Things (IoT) devices, PAPR cannot always be ideally eliminated due to the complexity of the reduction algorithm and the limitation of computation resources. Hence, performance optimization under non-negligible PAPR becomes an important issue. This paper performs symbol error rate (SER) optimization in OFDM-IM systems with high PAPR. First, we derive a low complexity expression of receiver signal-to-noise ratio (SNR) in nonlinear OFDM-IM systems. Second, we find that SER in OFDM-IM is affected by the nonlinear distortion in both constellation mapping and index estimation. With this observation, we derive a closed-form expression of SER and prove that there is a lower bound. Third, we do SER optimization and identify the optimal system operating point with respect to the minimum SER. Finally, we validate our analysis through simulations.

SERs of Different Modulation Systems in 1G-4G

The Digital sub-band system is an indispensable technology for the development of modern society, which has a wide range of applications. This work is particularly concerned with developing applications for modulation techniques used in mobile communication. Based on MATLAB, this paper compared the modulation and demodulation of 2ASK, 2FSK, 2PSK, and QPSK horizontally and analysed the practical and theoretical error rates. With the constellation maps of 16QAM, 32QAM, 64QAM, and 256QAM, the relationship between the error rate and the signal-to-noise ratio was studied. In binary modulation systems, 2PSK has the best noise resistance and requires 6dB less SNR than 2ASK when employing the same demodulation approach. In addition, this paper outlined the technologies and modulation standards employed in the development of 1G-4G. To make the comparison clearer, the advantage, disadvantages, and modulation comparisons among 1G-5G are displayed. The analysis and research of digital sub-band modulation technology is the basis for developing new technology in the future.

A hybrid deep learning using reptile dragonfly search algorithm for reducing the PAPR in OFDM systems

Abstract Orthogonal frequency division multiplexing (OFDM) is a famous multi-carrier modulation technique as it has a vast range of features like robustness against multi-path fading, higher bandwidth efficiency, and higher data rates. Though, OFDM has its own challenges. Among them, high peak power to average power ratio (PAPR) of the transmitted signal is the major problem in OFDM. In recent years, deep learning has drastically enhanced the performance of PAPR. In addition, the excessive training data and high computational complexity lead to a considerable issue in OFDM system. Thus, this paper implements a new PAPR reduction scheme in OFDM Systems through hybrid deep learning algorithms. A new optimized hybrid deep learning termed O-DNN + RNN is implemented by integrating the deep neural networks (DNN) and recurrent neural networks (RNN), where the parameters of both DNN and RNN are optimized using Hybrid Reptile Dragonfly Search Algorithm (HR-DSA). The new deep learning model is adopted for determining the constellation mapping and demapping of symbols on each subcarrier. This new optimized hybrid deep learning helps in reducing the PAPR and maximizes the performance.

Sparse Space Shift Keying Modulation with Enhanced Constellation Mapping.

For reducing the switching frequency between the radio frequency (RF) chain and transmit antennas, a class of new sparse space shift keying modulation (SSSK) schemes are presented. This new class is proposed to simplify hardware implementation, through carefully designing the spatial constellation mapping pattern. Specifically, different from traditional space shift keying modulation (SSK), the proposed SSSK scheme utilizes more time slots to construct a joint design of time and spatial domain SSK modulation, while maintaining the special structure of single RF chain. Since part of the multi-dimension constellations of SSSK concentrate the energy in less time slots, the RF-switching frequency is effectively reduced due to the sparsity introduced in the time domain. Furthermore, through theoretical analysis, we obtain the closed-form expression of the bit error probability for the SSSK scheme, and demonstrate that slight performance gain can be achieved compared to traditional SSK with reduced implementation cost. Moreover, we integrate transmit antenna selection (TAS) to achieve considerable performance gain. Finally, simulation results confirm the effectiveness of the proposed SSSK scheme compared to its traditional counterpart.

Social Media Portraits and YouTubers during the COVID-19 Pandemic in Indonesia

Social media and Internet technology are like a coin. The existence of social media and Internet technology is a prospective medium for the realization of digital media. The advantages of digital media are that it has a high level of interactivity, high interconnectivity can be broadcast live or delayed, stored eternally; easy to use and inexpensive tends to be free. The fantastic growth of internet and social media users at this time has made the existence of these mediums shift and threaten conventional media technology (newspapers, radio, and analog television), and even threaten the existence of digital TV and radio broadcasting stations. Research problem formulation: how is the constellation map of social media and YouTubers during the COVID-19 pandemic in Indonesia? How is the competition between YouTubers in Indonesia during the COVID-19 pandemic in attracting social media users and Internet users in the world? The research paradigm is quantitative and qualitative. Data collection techniques were carried out by questionnaires, literature review, documentation, and interviews. As a result, the use of social media and the internet has experienced an extraordinary spike at the national and world levels. The collapse of several media companies during the COVI-19 pandemic was a major blow to the media industry. Media workers and media entrepreneurs are obliged to carry out digital transformation, by optimizing Internet and social media technology. The public must also be smarter in using internet technology and social media as a productive medium, not just as a consumptive and entertainment medium. Considering the various professions and jobs using internet technology and social media, nowadays and in the future it is very prospective.