Trellis-coded Modulation Research Articles

Deep learning-driven channel coding: enhancing performance in LDS-CDMA and NOMA systems

This paper presents an innovative approach to channel coding for LDS-CDMA and NOMA systems through the integration of deep learning techniques. By leveraging neural networks within the channel coding process, the proposed model achieves substantial improvements in error correction, leading to a significant reduction in Bit Error Rate (BER) and computational complexity when compared to traditional methods such as Unpunctured Turbo Trellis Coded Modulation (UTTCM). The results demonstrate that the deep learning-based system is particularly effective in challenging communication environments, such as those with low Signal-to-Noise Ratios (SNR) and high levels of multi-user interference, where it outperforms conventional coding techniques. This research underscores the potential of deep learning to enhance the efficiency and adaptability of wireless communication systems, particularly as networks evolve towards 6G and beyond. The flexibility offered by this approach allows for improved handling of dynamic and complex environments, ensuring higher data throughput and reduced latency. Future work may focus on implementing the proposed model in real-time applications, as well as investigating its synergy with emerging technologies like massive MIMO and NOMA, which could lead to even greater performance enhancements in next-generation communication systems.

Joint equalization and decoding with per-survivor processing based on super-trellis in time-varying underwater acoustic channels.

This Letter proposes a low-complexity joint equalization and decoding reception scheme based on super-trellis per-survivor processing, making it possible to apply maximum likelihood sequence estimation in high-order underwater acoustic communications under fast time-varying channels. The technique combines trellis-coded modulation states and intersymbol interference states and uses per-survivor processing to track channel parameters. Furthermore, a general trellis configuration for arbitrary order quadrature amplitude modulation signal is provided when truncate the channel is used to describe the intersymbol interference state to 1. Sea trials results show that the performance of proposed method can be more than 1.4 dB superiority than conventional schemes.

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.

Hybrid Optimized LMMSE-Based Channel Estimation with Low Power Trellis Coded Modulation

Data transfer in a wireless channel environment is plagued by numerous security issues and power transmission loss. Channel state information is crucial to attaining the performance benefit of reconfigurable intelligent surfaces (RISs) in wireless systems. Because of the Doppler effect, mobility makes accurate channel estimate (CE) more difficult. The parameter estimation approach is employed as an alternative to direct estimation in the channel matrix to address the aforementioned problems. Also, to lower the Mean Square Error (MSE) between the estimated and original channel, training-based CE, such as Linear Minimum Mean Square Error (LMMSE), and Least Square Error (LSE), are widely used in some wireless standards. To optimize the channel, certain intelligent optimized strategies are presented. For the Optimal CE, a Trellis Coded Modulation (TCM) with hybrid optimization in LMMSE has been provided. Moth amalgamated Elephant Herding Optimization (MAEHO) algorithm is the proposed hybrid optimization. Finally, the performance of the accepted model is determined in comparison to other existing techniques using a variety of metrics.

DESIGN OF SPACE TIME TRELLIS CODED OFDM

Space Time Trellis Code (STTC) is a technique that can be used to improve the performance ofthe Orthogonal Frequency Division Multiplexing (OFDM) system over wireless channels byproviding both coding gain and diversity gain. STTC is combined from two codes, Trellis CodeModulation (TCM) as an inner code and Space Time Block Code (STBC) as an outer code. TCMwhich combines the choice of a modulation scheme with that of a convolutional code provides thecoding gain, and the other code provides the diversity gain. Simulation is done over flat fading andfrequency selective Rayleigh fading channel for Eight Phase Shift Keying (8-PSK) TCM. It foundthat the best results are obtained for the case of two transmitters and three receivers which have again of about 18dB over that without STBC.

KNN-Based ML Model for the Symbol Prediction in TCM Trellis Coded Modulation TCM Decoder

Machine Learning is a booming technology today. In a machine learning set of training, data is to be provided to the model for training and that model predicts the output. Machine Learning models are trained using a computer program known as ML algorithms.The new machine learning-based Transition Metric Unit (TMU) of 4D- 8PSK Trellis coded Modulation TCM Decoder is presented in this work. The classic Viterbi decoder's branch metric unit, or TMU, takes on a complex structure. Trellis coded Modulation (TCM) is a combination of 8 PSK modulations and Error Correcting Code (ECC). TMU is one of the complex units of the TCM decoder, which is essentially a Viterbi decoder. Similar to how the first Branch metric is determined in the straightforward Viterbi decoder, the TCM decoder performs this BM computation via the TMU unit. The TMU becomes challenging and uses more dynamic power as a result of the enormous constraint length and the vast number of encoder states.In the proposed algorithm innovative KNN (K nearest neighbours) based ML model is developed. It is a supervised learning model in which input and output both are provided to the model, training data also called the labels, when a new set of data will come the model will give output based on its previous set experience and data.Here we are using this ML model for the symbol prediction at the receiver end of the TCM decoder based on the previous learning. Using the proposed innovation, the paper perceives the optimization of the TCM Decoder which will further reduce the H/W requirements and low latency which results in less power consumption.

Implementation of Turbo Trellis Coding Modulation Scheme for Fading Channel

In the context of data communication, encountering fading channels can lead to errors occurring at the receiving end due to multipath propagation. To address this challenge, researchers have persistently worked towards developing Error Correction Schemes that effectively manage these errors and guarantee error-free data reception for the receiver. One area of focus lies in the implementation of Forward Error Correction Schemes directly at the transmitter end. Nonetheless, integrating error correction coding using these schemes comes with the drawback of increased bandwidth requirements since additional bits must be included to facilitate error correction. Fortunately, there exists a coding scheme known as Trellis Coded Modulation (TCM), which specifically tackles this concern. In the case of TCM, the modulation scheme has been chosen based on the rate of the convolutional coding scheme. Nevertheless, TCM has certain limitations when it comes to correcting a high number of errors, which prompted the emergence of Turbo Coding. Turbo Coding employs two coders at the transmitter, arranged either in a serial or parallel configuration, along with an appropriate decoder at the receiver. This paper introduces a Turbo Coding scheme design utilizing convolutional coders with a rate of 2/3, arranged in a serially concatenated configuration, resulting in an effective rate of 4/9. For preserving bandwidth, the Turbo Coding is applied to TCM scheme. Consequently, when employing the convolutional coding scheme with a rate of 2/3, the modulation scheme has to be 8-QAM. However, to maintain bandwidth after coding, when utilizing the Turbo coding scheme with a rate of 4/9, the modulation scheme is upgraded to 512-QAM. MATLAB simulations were conducted to evaluate the error correcting capabilities of the designed scheme compared to the convolutional coding scheme that uses the constituent convolutional encoder. The comparison has also been made with the uncoded data communication utilizing simple QPSK modulation scheme. The results indicate that under Rician fading channel conditions, the Turbo Trellis Coding Modulation Scheme provides an approximate gain of 5 dB compared to the convolutional coding scheme and approximately 8 dB gain compared to uncoded one.

Design of Turbo Trellis Coding Modulation Scheme of Rate 4/9 for Rician Fading Channel

When the fading channels are encountered during data communication, errors are likely to occur at the receiving end due to multipath propagation. Researchers have been consistently striving to develop Error Correction Schemes that can effectively handle these errors and ensure error-free data reception at the receiver end. Of particular interest are the Forward Error Correction Schemes that can be implemented at the transmitter end itself. However, the implementation of error correction coding through these schemes incurs additional costs in terms of bandwidth expansion, as extra bits need to be added to facilitate error correction. Fortunately, there exists one coding scheme called Trellis Coded Modulation (TCM), which addresses this issue. TCM selects a modulation scheme based on the rate of the convolutional coding scheme. However, this coding technique has limitations in correcting the number of errors, leading to the development of Turbo Coding. This scheme utilizes two coders at the transmitter, arranged in either serial or parallel configuration, and a suitable decoder at the receiver. A design of Turbo Coding scheme has been presented in this paper, that employs convolutional coders having rate 2/3, in a serially concatenated configuration, providing an effective rate of 4/9. This turbo coding scheme is then applied to TCM scheme in order to preserve the bandwidth. Therefore, if using the convolutional coding scheme of rate 2/3, the modulation scheme is 8-QAM and in order to preserve bandwidth after coding, using the Turbo coding scheme of rate 4/9, then the modulation scheme will be 512-QAM. The simulations have been conducted in MATLAB and the error correcting capabilities of the designed scheme in comparison with convolutional coding scheme using the constituent convolutional encoder have also been compared. It has been observed that in the Rician fading channel conditions, the Turbo Trellis Coding Modulation Scheme provides approximately 5 dB gain compared to the convolutional coding scheme.

90-m/560-Mbps underwater wireless optical communication utilizing subband multiple-mode full permutation CAP combined with an SNR-weighted detector and multi-channel DFE.

In this paper, a joint signal processing scheme including a subband multiple-mode full permutation carrierless amplitude phase modulation (SMMP-CAP), signal-to-noise ratio weighted detector (SNR-WD), and multi-channel decision feedback equalizer (MC-DFE) is proposed to mitigate the bandwidth limitation of a high-speed long-reach underwater wireless optical communication (UWOC) system. Referring to the trellis coded modulation (TCM) subset division strategy, 16 quadrature amplitude modulation (QAM) mapping set is divided into four 4-QAM mapping subsets by SMMP-CAP scheme. An SNR-WD and an MC-DFE are employed to enhance the demodulation effect of this system in a fading channel. In a laboratory experiment, the minimal required received optical powers (ROPs) for data rates of 480 Mbps, 600 Mbps, and 720 Mbps, at hard-decision forward error correction (HD-FEC) threshold of 3.80 × 10-3, are -32.7 dBm, -31.3 dBm, and -25.5 dBm, respectively. Moreover, the proposed system successfully achieves a data rate of 560 Mbps in a swimming pool with a transmission distance up to 90 m and a total attenuation measured to be 54.64 dB. To the best of our knowledge, this is the first time to demonstrate a high-speed, long-distance UWOC system by employing an SMMP-CAP scheme.

CG-SCMA Codebook Design Based on Maximized Euclidian Distance

Sparse code multiple access (SCMA) is a multi-dimensional codebook based on a class of non-orthogonal multiple access (NOMA) technologies enabling the delivery of non-orthogonal resource elements to numerous users in 5G wireless communications without increasing complexity. This paper proposes a computer-generated sparse code multiple access (CG-SCMA) technique, where the minimum Euclidian distance (MED) of a star 16-point quadrature amplitude modulation is maximized by CG-SCMA, thus creating a complex SCMA codebook based on optimizing the difference between the first and other radiuses over rotated constellations. To specify the most suitable values for this constellation, it is divided into four sub-constellations using trellis coded modulation (TCM) in an effort to optimize MED. The new codebook has four sub-constellations with MED values of 3.85, 2.26, 2.26, and 3.85, respectively. Application of the message passing algorithm (MPA) ensures low complexity of the decoding process.

Recurrent Neural Network Based Joint Equalization and Decoding Method for Trellis Coded Modulated Optical Communication System

In this paper, a joint equalization and decoding method based on recurrent neural networks (RNNs) is proposed for trellis coded modulation (TCM) systems. For traditional methods based on concatenated equalizers and Viterbi decoder, the information may be lost between the equalization and decoding. However, our proposed joint method can obtain the information bits directly from the received symbols and the error also can be corrected in iterations. In two-dimensional eight-level pulse amplitude modulation (2D-PAM8) links, we experimentally demonstrate that, compared with the traditional method based on Volterra filter and Viterbi decoder, the proposed joint method based on RNNs with similar complexity can achieve bit-error rate (BER) performance improvements of 1 dB, 1 dB, and 2 dB in 87.5 Gb/s, 100 Gb/s, and 112.5 Gb/s transmissions at 7% hard-decision forward-error-correction (HD-FEC) limit, respectively. For the 10 km standard single-mode fiber (SSMF) link at 87.5 Gb/s, the traditional method cannot get the BER below the 7% HD-FEC limit whereas the joint RNNs method with similar complexity can get the BER below the 7% HD-FEC limit. As the nonlinearity increases, the proposed joint method can achieve greater improvement of BER performance.

Probabilistic Shaping for Trellis-Coded Modulation With CRC-Aided List Decoding

This paper applies probabilistic amplitude shaping (PAS) to cyclic redundancy check (CRC)-aided tail-biting trellis-coded modulation (TCM). CRC-TCM-PAS produces practical codes for short block lengths on the additive white Gaussian noise (AWGN) channel. In the transmitter, equally likely message bits are encoded by a distribution matcher (DM) generating amplitude symbols with a desired distribution. A CRC is appended to the sequence of amplitude symbols, and this sequence is then encoded and modulated by TCM to produce real-valued channel input signals. This paper proves that the sign values produced by the TCM are asymptotically equally likely to be positive or negative. The CRC-TCM-PAS scheme can thus generate channel input symbols with a symmetric capacity-approaching probability mass function. The paper provides an analytical upper bound on the frame error rate of the CRC-TCM-PAS system over the AWGN channel. This FER upper bound is the objective function used for jointly optimizing the CRC and convolutional code. Additionally, this paper proposes a multi-composition DM, which is a collection of multiple constant-composition DMs. The optimized CRC-TCM-PAS systems achieve frame error rates below the random coding union (RCU) bound in AWGN and outperform the short-blocklength PAS systems with various other forward error correction codes studied in Coşkun et al. (2019).

Application of a Trellis Coded Modulation to Ameliorate the 5G Communication for Tropical Regions

Objectives: To minimize the bit error rate and enhance the radio signal power by an application of the Trellis Coded Modulation (TCM) for the Fifth Generation (5G) technology in tropical regions. Methods: Various diversity techniques have been adopted to diminish the Bit Error Rate. A Communication link model has been proposed in this work and an STBC MIMO system (Space-Time Block Coding multiple-input multiple-output) has been applied to enhance the diversity gain and coding gain of the proposed model. The said model has been implemented in this work for tropical regions for increasing the radio signal power. Findings: The basic climatic feature of tropical regions is a heavy amount of rainfall throughout the year. Because of such rainfall, the radio signal power in these regions gets diminished, and the Bit Error Rate (BER) increases. By applying the proposed communication link model in the tropical regions the Bit Error Rate has been reduced. The values of the Bit Error Rate of the proposed model have been obtained for Rayleigh distribution, Rician distribution and various MIMO techniques. Novelty: A hardware cosimulation block and a 4x4 STBC MIMO has been developed with its subsequent verification on Xilinx Kintex-7 FPGA board. Keywords: Bit error rate; MIMO Systems; Xilinx system generator; Trellis coded modulation; FPGA; Signal attenuation

Performance-Enhanced Three-Dimensional Trellis Coded Modulation Based on Four-Winged Fractional-Order Chaotic Encryption For Physical Layer Security

In this paper, an encrypted three-dimensional (3D) trellis-coded modulation (TCM) based on mapping by set-partitioning (MSP) of 3D constellation is proposed, for highly reliable and secure short-reach transmission. 3D-TCM encoder encryption and 3D constellation rotation are realized with the implementation of a 4D four-winged fractional-order chaotic (FWFC) system and MSP of 3D constellation, the suggested approach demonstrates higher coding gain and chaotic encryption. A 35 Gb/s (5 Gb/s × 7) encrypted 3D-TCM-32CAP signal transmission over ∼2 km seven-core fiber is experimentally demonstrated. The results show that the encrypted 3D-TCM-32CAP obtains a 2.9 dB and 3.8 dB gain in receiver sensitivity at a bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> under the same bit rate, when compared with conventional 2D-TCM-32CAP and 3D-32CAP, respectively. Furthermore, a handsome key space of the proposed scheme is obtained ∼2.205 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">160</sup> , which is large enough to effectively guard against malicious attacks from illegal optical network units. In a nutshell, the experimental results indicate the proposed encrypted 3D-TCM-32CAP scheme combines the superiority of BER and security performance.

Low Power Trellis Coded Modulation (TCM) Decoder by Using Modified Resource Sharing Method for IoT Enabler

This paper proposes a new pre-computation approach based on the auxiliary trellis of the TCM decoder's ACSU (add compare select unit). The suggested method is based on pre-computation of path metrics and resource sharing of the ACSU unit. The Viterbi decoder itself is a power-consuming module of the communication system that comprises the TMU (transition metric unit) and ACSU (add compare select unit). By applying the suggested method, the authors would be able to achieve low dynamic power. The TCM decoder designed accordingly shows better SER/ BER results in comparison to the existing techniques. The 4D 8 PSK TCM encoder and decoder were implemented as per the design specifications given by consultative committee for space data system (CCSDS) for satellite applications. The simulations results are observed on 100 Mbps data for 8PSK modulation and the ¾ code rate of the TCM encoder. The results based on the new method show improved power-speed ratio with improved SER and BER.

Performance Enhancement of W-Band RoF System Using 4D Trellis Coded Modulation OFDM With Precoding

In the paper, a four-dimensional trellis-coded modulation 16-quadrature amplitude modulation-orthogonal frequency division multiplexing (4D TCM 16QAM-OFDM) combined with precoding scheme is proposed and experimentally demonstrated in W-band radio-over-fiber (RoF) system. In W-band RoF system, frequency selective fading can cause unbalanced signal-to-noise ratio (SNR) distribution on the sub-carriers of the 4D TCM 16QAM-OFDM signals. Orthogonal circulant matrix transform (OCT) precoding, discrete Fourier transform (DFT) precoding, and constant amplitude zero autocorrelation sequence (CAZAC) precoding can be used to balance the SNR over the data subcarriers of 4D TCM 16QAM-OFDM signals. Moreover, DFT precoding and CAZAC precoding can reduce the peak-to-average power ratio (PAPR) of 4D TCM 16QAM-OFDM signals. After 50km single-mode fiber (SMF) and 5m free space transmission, the experimental results show that, at 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> , compared with 4D TCM 16QAM-OFDM using OCT precoding and DFT precoding, 4D TCM 16QAM-OFDM using CAZAC precoding can achieve the receiver sensitivity improvement of 2.33 dB and 0.48 dB respectively. In addition, compared with 4D TCM 16QAM-OFDM without precoding, it can achieve the receiver sensitivity improvement of 3 dB by using CAZAC precoding. Furthermore, 4D TCM 16QAM-OFDM has higher spectral efficiency than 8QAM-OFDM at the same symbol rate. The receiver sensitivity for 4D TCM 16QAM-OFDM using CAZAC precoding is enhanced about 1.1 dB, compared with 8QAM-OFDM using CAZAC precoding.

High-security multi-level constellation shaping trellis-coded modulation method based on clustering mapping rules.

This paper proposes a high-security multi-level constellation shaping trellis-coded modulation (TCM) method based on clustering mapping rules, which is suitable for passive optical networks (PON) using three-dimensional (3D) carrier-less amplitude and phase modulation (CAP). This method combines the TCM mapping process with the constellation shaping and performs a multi-level mapping of the coded signal according to the classification label, so as to obtain better constellation shaping gain while expanding the coding gain of the TCM. The 3D constellation generated by the multi-level mapping adopts Chua's chaotic model for rotation encryption, which improves the ability of the optical access network to resist malicious attacks at the physical layer. Experiments show that 70 Gb/s (7×10 Gb/s) transmission is achieved on a 2 km weakly coupled seven-core fiber using the scheme proposed in this paper. At a bit error rate (BER) of 1 × 10-3, the difference in receiver sensitivity between the best and worst-performing cores is about 0.7 dB. The difference in receiver sensitivity between the cubic constellation and the chaotic spherical constellation is about 0.1 dB. The sensitivity of the chaotic spherical constellation receiver is about 6.98 dB higher than that of the 2D shaping constellation receiver. The experimental results show that the scheme has reliable security performance while improving the short-reach transmission capacity. It has broad application prospects in future short-reach communication research.

Underwater optical wireless communication performance enhancement using 4D 8PAM trellis-coded modulation OFDM with DFT precoding.

A 4D 8-pulse amplitude modulation trellis-coded modulation-based orthogonal frequency division multiplexing (4D 8PAM TCM-OFDM) scheme combined with discrete Fourier transform (DFT) precoding is proposed and experimentally demonstrated in an underwater optical wireless communications system. It can resist power fading caused by the attenuation, scattering, and reflection in the water channel. The experimental results show that, after transmission over the water-air channel and at the bit error rate of 3.8×10-3, the improvement in the receiver sensitivity is 0.88 dB using the 4D 8PAM TCM-OFDM scheme, compared to the conventional 64QAM-OFDM scheme. In addition, the proposed 4D 8PAM TCM-OFDM scheme combined with DFT precoding can compensate for unbalanced impairments, and it can obtain 1.28 dB receiver sensitivity improvement, compared to the conventional 64QAM-OFDM scheme with DFT precoding.

Modeling and Analyzing Trellis-Coded Modulation on Power Line Communication Systems

Power Line channels present a very harsh environment for high speed data transfer which degrades the data transmission. Using proper channel coding can enhance the data transmission over PLC systems. The purpose of using channel coding is to encode the information transmitted over communication channel in such a way that in presence of other interferences and noise, the error can be detected and possibly corrected. This paper investigates the Bit Error Rate (BER) performance of PLC systems based on Orthogonal Frequency Division Multiplexing (OFDM), in presence of Middleton class A noise, and applying Trellis Coded Modulation (TCM) / Rectangular Quadrature Amplitude Modulation (QAM) TCM as a channel coding. Simulations are undertaken in Matlab 2013b. The obtained results illustrates that although trellis codes produce improvements in the SNR in presence of Additive white Gaussian noise (AWGN), they do not perform well with multipath power line channel and Middleton class A noise. Therefore the Rectangular QAM TCM has been used to enhance the results.

Performance of signal detection with trellis code for downlink non-orthogonal multiple access visible light communication

This paper examines the implementation of multi-level amplitude modulation enforced by trellis coding in a downlink non-orthogonal multiple access channel for visible light communication (VLC). The non-orthogonal transmission is applied using superposition coding and successive interference cancellation with the support of a trellis decoder. The VLC is addressed by a channel model according to Lambert. Two levels of maximum likelihood signal detection are observed and compared, each for corresponding 4 and 8 trellis-coded modulation (TCM). The power ratio allotment is examined to investigate the system performance in the bit error rate. The simulation showed that a threshold of power ratio is needed to ensure good performance of signal detection. Further simulation with successive detection had shown effective results for up to three users.