Joint Demodulation Research Articles

Interference Modeling and Joint Demodulation Receiver for Multi-level PON with Baseband AMCC Superimposition

Interference Modeling and Joint Demodulation Receiver for Multi-level PON with Baseband AMCC Superimposition

A high-resolution joint demodulation algorithm for the fiber-optic low-finesse extrinsic Fabry-Perot interferometric sensor

In order to improve the resolution of the demodulation algorithm of the fiber-optic low-finesse extrinsic Fabry-Perot interferometric (EFPI) sensor, this paper presents a joint demodulation algorithm based on the synchronous squeezing wavelet transform phase extraction method and the weighted cosine similarity approach. This algorithm combines the advantages of the synchronous squeezing wavelet transform phase extraction method which can achieve high resolution in dynamic measurement, with the weighted cosine similarity method which can reduce signal interference to obtain high resolution. In the experiment, the joint demodulation algorithm realizes a high-resolution measurement of the EFPI sensor, reaching 0.020 nm and the greatest fluctuation 0.053 nm with an initial cavity length of 60 μm. The resolution of the joint demodulation algorithm has shown promising result at the sub-nanometer level.

An Intelligent Detection Based on Deep Learning for Multilevel Code Shifted Differential Chaos Shift Keying System With M-ary Modulation

Multilevel code shifted M-ary differential chaos shift keying (MCS-MDCSK) system provides higher data rate chaotic information transmission by applying multilevel code shifting aided M-ary modulation. However, the real-valued chaotic sequences induce interferences to signals while higher-order modulation shortens the Euclidean distance between adjacent symbols, thereby leading to performance degradation. To improve the bit-error rate (BER) performances, we propose an intelligent detector to achieve the joint demodulation and de-spreading at the receiver. In this design, we construct the recursive long short-term memory (LSTM) unit to extract features from the correlated chaotic modulated signals. Then we concatenate the LSTM unit with multiple full connection layers (FCLs) and compose the deep neural network (DNN) to recover the information. Owing to the serial concatenated LSTM-aided DNN, the intelligent detector can learn the joint chaotic modulation and spreading pattern, and achieve the joint demodulation and de-spreading. Consequently, larger performance gain can be attained and the reliability performances will be improved. Simulation results validate the proposed design. Moreover, for practical systems undergoing multiplicative fading, the intelligent MCS-MDCSK detector exhibits better BER performances than the benchmark systems.

Joint Demodulation and Error Correcting Codes Recognition Using Convolutional Neural Network

Demodulation of the communication signals and blind identification of error-correcting codes (ECC) are two essential purposes in adaptive modulation and coding (AMC) techniques and non-cooperative communication fields. The existing approaches treat them as two separate problems, namely the demodulation of signals with known a <i>priori</i> knowledge (such as channel state information (CSI) or channel noise) and the ECC type identification that depends on the demodulation results. In this paper, a novel one-stage ECC identification approach based on a multi-task deep convolutional neural network (MT-DCNN) is presented. With this architecture, the proposed method automatically recognizes the ECC types of the baseband in-phase and quadrature-phase (IQ) data without relying on any conventional demodulators. Precisely, the proposed MT-DCNN consists of three modules: the feature extraction module, the demodulation module, and the ECC types recognition module. Experiment results show that the proposed architecture can accurately identify the ECC types of the baseband IQ signals and is superior to those of the existing two-stage recognition approaches.

Low Complexity Precoding and Detection in Multi-User Massive MIMO OTFS Downlink

We consider the problem of degradation in performance of multi-carrier multi-user massive MIMO systems when channel induced Doppler spread is high. Recently, Orthogonal Time Frequency Space (OTFS) modulation has been shown to be robust to channel induced Doppler spread. In OTFS based systems, information symbols are embedded in the delay-Doppler (DD) domain where they are jointly modulated to generate the time-domain transmit signal. Due to the multi-path delay and Doppler shifts, the DD domain information symbols need to be jointly demodulated at the receiver. For multi-carrier based communication (e.g., Orthogonal Frequency Division Multiplexing (OFDM)), massive MIMO systems have been shown to achieve high spectral and energy efficiency with low complexity multi-user precoding in the downlink. Extending the same to OTFS based downlink multi-user massive MIMO systems is challenging due to the requirement for joint demodulation of all information symbols at the user terminal (UT). In this paper, we solve this problem by proposing a novel OTFS based multi-user precoder at the base station (BS) and a corresponding low complexity detector (LCD) at the user terminals (UTs), which allows for separate demodulation of each DD domain information symbol at the UT. The complexity of the proposed precoder increases only linearly with increasing number of BS antennas Q and the number of UTs. We show, through analysis, that as Q increases (with total transmitted power decreased linearly with Q), the proposed low complexity detector achieves a sum spectral efficiency close to that achieved with optimal joint demodulation at each UT. Numerical simulations confirm our analysis and also show that the spectral efficiency and error rate performance of the proposed OTFS based massive MIMO precoder (with the proposed LCD detector at each UT) is significantly more robust to channel induced Doppler spread when compared to OFDM based multi-user massive MIMO systems.

A Joint Demodulation and Estimation Algorithm for Plasma Sheath Channel: Extract Principal Curves With Deep Learning

For reentry communication, owing to the influence of the time-varying plasma sheath, the received IQ baseband signals are severely rotated on constellation. Researches have shown that the frequency of electron density varies from 20kHz to 100 kHz which is on the same order as the symbol rate of most TT&C communication systems and traditional estimation algorithms cannot track the variation of channel. In this letter, motivated by principal curve analysis, we propose a deep learning (DL) algorithm which is called symmetric manifold network (SMN) to extract the curves on the constellation and classify the signals based on the curves. The key advantage is that SMN can achieve joint optimization of demodulation and estimation. From our simulation results, the new algorithm significantly reduces the symbol error rate (SER) compared to existing algorithms and enables accurate estimation of fading with extremely high bandwidth utilization rate.

Maximum likelihood sequence estimation for optical complex direct modulation.

Semiconductor lasers are versatile optical transmitters in nature. Through the direct modulation (DM), the intensity modulation is realized by the linear mapping between the injection current and the light power, while various angle modulations are enabled by the frequency chirp. Limited by the direct detection, DM lasers used to be exploited only as 1-D (intensity or angle) transmitters by suppressing or simply ignoring the other modulation. Nevertheless, through the digital coherent detection, simultaneous intensity and angle modulations (namely, 2-D complex DM, CDM) can be realized by a single laser diode. The crucial technique of CDM is the joint demodulation of intensity and differential phase with the maximum likelihood sequence estimation (MLSE), supported by a closed-form discrete signal approximation of frequency chirp to characterize the MLSE transition probability. This paper proposes a statistical method for the transition probability to significantly enhance the accuracy of the chirp model. Using the statistical estimation, we demonstrate the first single-channel 100-Gb/s PAM-4 transmission over 1600-km fiber with only 10G-class DM lasers.

Performance Improvement of Iterative Demodulation and Decoding for Spatially Coupling Data Transmission by Joint Sparse Graph

Both low-density parity-check (LDPC) codes and the multiple access technique of spatially coupling data transmission (SCDT) can be expressed in bipartite graphs. To improve the performance of iterative demodulation and decoding for SCDT, a novel joint sparse graph (JSG) with SCDT and LDPC codes is constructed. Based on the JSG, an approach for iterative joint demodulation and decoding by belief propagation (BP) is presented as an exploration of the flooding schedule, and based on BP, density evolution equations are derived to analyze the performance of the iterative receiver. To accelerate the convergence speed and reduce the complexity of joint demodulation and decoding, a novel serial schedule is proposed. Numerical results show that the joint demodulation and decoding for SCDT based on JSG can significantly improve the system’s performance, while roughly half of the iterations can be saved by using the proposed serial schedule.

Dual-Stream Transceiver Structure With Single Antenna for Phase-Modulated OFDM

Constant envelope orthogonal frequency-division multiplexing (OFDM) can achieve 0-dB peak-to-average power ratio (PAPR) by transforming the OFDM signal to a constant envelope signal. However, its spectral efficiency is less than half of the OFDM. In this letter, a dual-stream transceiver structure with single antenna is proposed to increase the spectral efficiency. At the transmitter, the structure based on phase shifting is proposed to transmit two data streams simultaneously. At the receiver, the joint demodulation structure based on Taylor series expansion is proposed to separate the data streams and eliminate the need for a phase demodulator. The mathematical analysis reveals that the statistical PAPR of the baseband signal is 3 dB. The bit error rate performance is evaluated with additive white Gaussian noise channel and multipath fading channel under the condition of ideal power amplifier and solid-state power amplifier. Simulation results show that the proposed structure can improve the spectral efficiency and is robust against multipath fading.

Joint blind equalization and detection in chaotic communication systems using simulation-based methods

In this paper an importance sampling (IS)-based technique is proposed to achieve the blind equalizer and detector for chaotic communication systems. Chaotic signals are generated using nonlinear dynamical systems. These signals have wide applications in communication as a result of their appropriate properties such as pseudo-randomness, large bandwidth, and unpredictability for long time. Based on the different chaotic signal properties, different communication methods such as chaotic modulation, masking, and spread spectrum have been proposed before. In this paper, chaos masking is adopted for transmitting modulated message symbols over an unknown channel, in which the joint demodulation and equalization is a nonlinear problem. Several methods such as extended Kalman filter (EKF), particle filter (PF), minimum nonlinear prediction error (MNPE), have been previously presented for this problem. Here, a new approach, based on Monte Carlo sampling, is proposed to joint channel equalization and demodulation. At the receiver end, importance sampling is used to detect binary symbols according to maximum likelihood (ML) criterion. Simulation results show that the proposed method has better performance, compared to existing methods, especially at low SNR.

One Joint Demodulation and Despreading Algorithm for MOD5

IFF determines the response properties of the target to identify friend or foe through question and answer mechanism, and nowadays it plays an important role in the modern information warfare. This paper introduces the tran- sponder digital processing system in the new type of IFF, specially including the processing method of receiving and transmitting in MOD5 and the theory of basic MSK modulation, maximum likelihood Viterbi demodulation and Walsh spreading and despreading, discussing the shortage of maximum likelihood Viterbi demodulation, then proposing the weighted MSK demodulation and despreading algorithm and joint demodulation and despreading algorithm based on the improved maximum likelihood Viterbi demodulation algorithm. The joint demodulation algorithm is more outstanding than the maximum likelihood Viterbi demodulation algorithm according to simulation.

FTN 시스템을 위한 동시 복조 및 복호 기법

본 논문에서는 FTN (Faster than Nyquist) 방식을 이용한 데이터 전송기법에서 효율적으로 ISI (Inter Symbol Interference)를 제거하기 위한 기법을 제안한다. FTN 방식을 이용한 통신 시스템은 나이퀴스트 (Nyquist) 율 보다 빠르게 신호를 전송하는 방식으로 필연적으로 ISI가 발생한다. FTN 시스템에서 ISI를 제거하기 위한 여러 방안들이 제안되었으며 대표적으로 BCJR (Bahl-Cocke-Jelinek-Raviv) 알고리듬 기반의 ISI 제거 기법을 들 수 있다. 그러나 제안된 기법들은 매우 큰 구현 복잡도를 갖으며, 특히 고차 변조 기법을 사용할 경우 복잡도는 변조 차수에 따라 지수적으로 증가하는 단점이 있다. 구현 복잡도를 줄이기 위하여 길쌈부호가 적용된 시스템에서 SIC (Successive Interference Cancellation) 기법을 이용하여 ISI를 제거하는 기법이 제안되었다. 본 논문에서는 반복 복호가 가능한 채널 부호화 기법과 고차 변조가 적용된 시스템에서 복호기에서 생성된 정보를 이용하여 FTN 복조를 효율적으로 수행할 수 있는 기법을 제안한다. 제안하는 기법은 기존에 제안된 기법들에 비하여 낮은 구현 복잡도를 나타낼 뿐만 아니라 우수한 ISI 추정 성능으로 인하여 주어진 신호 대 잡음비 (Signalto-Noise Ratio) 영역에서 보다 나은 비트오율 (Bit Error Rate) 성능을 나타낸다. 또한 고차 변조 기법이 적용된 시스템에서도 큰 복잡도 증가 없이 적용이 가능하다.

Research on Communications at Low SNRs in Deep Space Explorations

与传统无线通信相比, 深空通信由于传输损耗巨大、探测器能量受限且轨道多变等因素, 须解决信噪比(Signal to Noise Ratio, SNR)极低、数据接收不连续及信道参数多变等难题. 针对这些问题, 论述了在深空探测极低SNR下需重点研究的深空天线组阵、编码与调制、联合解调译码、喷泉码以及其自主无线电实现等关键技术, 以有效协助解决上述深空通信难题. 同时, 讨论了这些关键技术的发展趋势及其在未来深空通信中的应用.

Joint Demodulation and EMS Decoding Algorithm for Q-ary LDPC Codes

To reduce the high decoding complexity of q-ary LDPC codes, a joint-demodulation and extended min-sum (JD-EMS) decoding algorithm is presented in this paper. By utilizing the squares of the distances between signal and constellation points over constellation graph as the decoder input soft messages, the proposed algorithm not only facilitates the computations of the decoder initial messages, but also avoids the performance loss due to conversions between probabilities and log-likelihoodratios. The elementary check node (ECN) processing is also improved in JD-EMS algorithm, thus the number of real additions can be reduced. Moreover, we also give an upper bound of the number of comparison candidates in the sorter at each ECN step. Simulation results indicate that, while significantly reducing the number of real additions at check nodes, JD-EMS algorithm performs as well as EMS algorithm on both AWGN and Rayleigh fading channels.

Network code assisted HARQ scheme in multi-user systems with cooperative relays

A network code assisted HARQ system considering uplink (UL) transmission with multiple mobile stations (MSs) cooperating with a relay-station (RS) is proposed. The RS is assumed to successfully monitor and decode the packets transmitted from the MSs to the base station (BS). The BS partitions the incorrectly decoded packets into groups based on their MS-to-BS channel conditions and feedbacks this partition to the RS. The RS employs a network-coded HARQ scheme within each group for subsequent retransmissions. We proposed a dynamic and adaptive partitioning method based on the BS channel state information and the corresponding HARQ retransmission schemes. Also, we derived a low-complexity joint demodulation and decoding structure. Simulations showed that our scheme improves the system throughput by 15% when compared with the relay assisted chase-combining HARQ system. We also explored suitable ranges of diversity orders for the RS-to-BS and MS-to-BS channels that provide significant system throughput improvements with practical implementation cost.

Iterative method of joint demodulation and filtering of communications channel parameters in digital information transmission systems

The iterative method, which can be applied to estimation of the unknown vector of discrete parameters in combination with filtering of the unknown vector of continuous signal parameters, is proposed. It is demonstrated that this method makes it possible to construct highly efficient algorithms for joint demodulation and filtering of communications channel parameters in code-division multiple-access and orthogonal frequency-division multiplexing systems.

An iterative interference cancellation method for co-channel multicarrier and narrowband systems

Coexistence of narrowband (NB) and multicarrier technologies will be a major concern in next generation wireless communication systems due to the co-channel interference (CCI) problem. In this paper, an efficient CCI cancellation method is proposed that may be utilized for improved coexistence of NB and multicarrier technologies. The method treats both co-channel signals as desired signals and enhances them in an iterative manner. In every iteration, the signals are demodulated, regenerated, and subtracted from the received signal successively in order to obtain a better estimate of the other co-channel signal. Computational complexity of the proposed method is compared in detail with the joint demodulation technique. Through computer simulations, it is shown that the proposed method has lower complexity compared to joint demodulation, and it yields significant gains in the symbol error rate (SER) performance of both the NB and multicarrier systems.

Joint Demodulation and Detection of Covert Modulated M-sequence

Abstract:The paper Present a new receiver for detection of covert M.sequence regardless the chipcode sequences and the type of modulation. A Higher Order Statistics (HOS) based onthe Kurtosis of the received signal is used to classify the type of the modulation, and sodecide the modulator. The Triple Correlations Function (TCF) of M. sequence of thedemodulated which differs from sequence to another according to the feedbackconnection is used to decide the generation function g (x) from the peak position of thisM-sequence. This paper is classified into four sections the first section, we introducesome property of modulation and how the (TCF) of the M.sequence generated.Secondly, the digital modulation classification is classified and tabulated usingtheoretical cumulants Statistics C40, C42. The Triple Correlation function (TCF) ofM.sequence is showed in section three. Computer simulation of determination offeedback polynomial y(x) at section four. Finally, the conclusion is presented in at therest of this paper.

A Joint Demodulation and Decoding Algorithm for High Order LDPC Coded Modulations

摘要: 该文用一种级联码模型描述了LDPC编码高阶调制系统。该级联码模型以LDPC码为外码，二-十进制转换码为内码，再加一个删余模块构成。基于这种级联码模型，该文给出了其联合校验方程和二分图，并提出了级联码置信度传播算法，实现了LDPC编码高阶调制系统的联合解调解码。仿真表明，该文提出的联合解调解码算法有效地改进了LDPC编码高阶调制系统的性能。 关键词: 低密度奇偶校验码; 高阶调制; 级联码置信度传播

A Joint Synchronization and Demodulation Scheme for UWB Systems

In this paper, a joint blind synchronization and demodulation scheme is developed for ultra-wideband (UWB) impulse radio systems. Based on the prior knowledge of the direct-sequence (DS) spread codes, the proposed approach can achieve frame-level synchronization with the help of frame-rate samples. Taking advantage of the periodicity of the DS spread codes, the frame-level synchronization can be carried out even in one symbol interval. On the other hand, after timing acquisition, these frame-rate samples can be re-utilized also for demodulation. Thus the acquisition time and the implementation complexity are reduced considerably. The performance improvement can be justified by both theoretical analysis and simulation results, in terms of acquisition probability and bit error rate (BER).