Showing papers on "SC-FDE published in 2020"

A Novel Signal Detection Scheme Based on Adaptive Ensemble Deep Learning Algorithm in SC-FDE Systems

Abstract: Reliable signal detection plays an essential role in enhancing the quality of signal transmission in wireless communication systems. In this paper, we combine signal detection theory with a deep learning model and propose a novel signal detection scheme based on adaptive ensemble long short term memory (AE-LSTM) neural network to handle wireless single carrier frequency domain equalization (SC-FDE) systems in an end-to-end manner. The feature information used for offline training of the deep learning model is extracted from the received signal containing channel state information (CSI) after the multi-path channel and fast Fourier transform (FFT), and the labels are assigned according to the constellation map adopted at the transmitter. To improve the adaptability of the system, we utilize the received power under different delays as the adaptive factor to integrate the output of each sub-network. Then the original data generated by the channel model is recovered by using the trained model instead of channel estimation and frequency domain equalization. Comparative experiments on SC-FDE symbol detection demonstrate that the proposed scheme achieves better performance in terms of reliability than the traditional scheme and the similar deep learning scheme.

Online LSTM-Based Channel Estimation for HF MIMO SC-FDE System

Abstract: The long distance high frequency (HF) communication suffers from time varying multipath fading. Multiple-Input Multiple-Output (MIMO) and Single-Carrier Frequency Domain Equalization (SC-FDE) have been introduced to HF communication system to combat fading. Because accurate channel estimation is essential for system operation, an architecture of signal flow chart has been designed for the HF MIMO SC-FDE system. In the architecture, an online Long Short-Term Memory (LSTM) estimator is proposed. Different from the channel responses time series created by the LSTM training and prediction loop, a corrected channel responses that are obtained through the received data symbols and the restored transmitting data symbols make up the channel responses time series. In order to evaluate the performance of channel estimators, a simulation system has been built. The uncorrelated and correlated channels are simulated referring to International Telecommunication Union (ITU)-R F.1487 standard and Kronecker model. The simulation results demonstrate that the online LSTM estimator outperforms Least Square (LS) and Recursive Least Square (RLS) estimators in terms of Bits Error Rate (BER) and Mean Square Error (MSE). The online LSTM estimator is capable of tracking the time varying HF MIMO channels. It has potentiality in actual long distance HF communication.

Efficient Joint Channel Equalization and Tracking for V2X Communications Using SC-FDE Schemes

Abstract: Our aim with this paper is to present a solution suitable for vehicle-to-everything (V2X) communications, particularly, when employing single-carrier modulations combined with frequency-domain equalization (SC-FDE). In fact, we consider the V2X channel to be doubly-selective, where the variation of the channel in time is due to the presence of a Doppler term. Accordingly, the equalization procedure is dealt by a low-complexity iterative frequency-domain equalizer based on the iterative block decision-feedback equalization (IB-DFE) while the tracking procedure is conducted employing an extended Kalman filter (EKF). The proposed system is very efficient since it allows a very low density of training symbols, even for fast-varying channels. Furthermore only two training symbols are required to initialize the tracking procedure. Thus, ensuring low latency together with reduced channel estimation overheads.

Analytical Performance Evaluation of Massive MIMO Techniques for SC-FDE Modulations

Abstract: In the Fifth Generation of telecommunications networks (5G), it is possible to use massive Multiple Input Multiple Output (MIMO) systems, which require efficient receivers capable of reaching good performance values. MIMO systems can also be extended to massive MIMO (mMIMO) systems, while maintaining their, sometimes exceptional, performance. However, we must be aware that this implies an increase in the receiver complexity. Therefore, the use of mMIMO in 5G and future generations of mobile receivers will only be feasible if they use very efficient algorithms, so as to maintain their excellent performance, while coping with increasing and critical user demands. Having this in mind, this paper presents and compares three types of receivers used in MIMO systems, for further use with mMIMO systems, which use Single-Carrier with Frequency-Domain Equalization (SC-FDE), Iterative Block Decision Feedback Equalization (IB-DFE) and Maximum Ratio Combining (MRC) techniques. This paper presents and compares the theoretical and simulated performance values for these receivers in terms of their Bit Error Rate (BER) and correlation factor. While one of the receivers studied in this paper achieves a BER performance nearly matching the Matched Filter Bound (MFB), the other receivers (IB-DFE and MRC) are more than 1 dB away from MFB. The results obtained in this paper can help the development of ongoing research involving hybrid analog/digital receivers for 5G and future generations of mobile communications.

A Physical Layer Security Technique for NOMA Systems with MIMO SC-FDE Schemes

Abstract: Current wireless communication systems employ Multi-Input, Multi-Output (MIMO) techniques to increase spectral efficiency, at the cost of higher hardware complexity. Most of these systems continue to employ traditional Orthogonal Multiple Access (OMA) schemes, which are suboptimal when compared to Non-Orthogonal Multiple Access (NOMA) schemes. By combining NOMA with MIMO, it is possible to achieve higher spectral efficiencies. However, security in NOMA-MIMO systems remains a problem. In this paper, we study the physical layer security issues of a power based NOMA-MIMO system with a Singular Value Decomposition (SVD) scheme, employed along with Single Carrier with Frequency Domain Equalization (SC-FDE) techniques. We consider a scenario where there is an unintended eavesdropper attempting to listen to the messages being exchanged. It is shown that the higher the channel estimate correlation between transmitter and receiver, the higher the secrecy rate, particularly for a scenario where there is a Line-Of-Sight (LOS) between all users. Therefore, power based NOMA MIMO-SVD schemes, combined with SC-FDE, can be considered efficient options for highly secure MIMO communications.

Performance Analysis of OAM Multiplexing Employing SC-FDE in the Presence of Ground Reflection

Abstract: This paper presents the theoretical system capacity of orbital angular momentum (OAM) multiplexing that employs single-carrier with frequency domain equalization (SC-FDE) in the presence of ground reflection. Considering that inter-symbol interference (ISI) remains even after inserting a guard interval (GI), in addition to inter-mode interference (IMI), we derive the effect of such residual IMI and ISI, and incorporate their impacts into the analysis of the system capacity. Moreover, in FDE, zeroforcing (ZF) and minimum mean square error (MMSE) are considered as the factors affecting the system capacity because the effect of noise enhancement differs among these two factors. In this study, we demonstrate theoretical results based on the tworay ground reflection model by using parameters of link distance and carrier frequency. The numerical results show that OAM multiplexing employing SC-FDE improves the system capacity compared with the case without FDE regardless of the link distance, and its effectiveness is remarkable in the cases of relatively lower carrier frequencies.

Estimating the performance of mimo sc-fde systems using siso measurements

Abstract: The demand for ubiquitous telecommunications services forces operators to have a special concern about signal quality and the coverage area they offer to their customers. This was usually checked by using suitable propagation models for Single Input Single Output (SISO) systems, which are no longer the case for new and future mobile generations, such as 5G and beyond. To guarantee good signal quality coverage, operators started to replace these models with Multiple Input Multiple Output (MIMO) ones. To achieve the best results, these models are usually calibrated with Drive Test (DT) measures; however, the DTs available for MIMO propagation models are sparse, in contrast to SISO ones. The main contribution presented in this paper is a methodology to extend the propagation models of SISO systems so they can be applied in MIMO sytems with Single-Carrier and Frequency-Domain Equalization (SC-FDE), while still using DTs acquired for SISO systems. This paper presents the impact on Bit Error Rate (BER) performance and its coverage area resulting from the application of our proposed method. We consider a MIMO SC-FDE system with an Iterative Block Decision Feedback Equalization (IB-DFE) receiver and we present the improvement expressions for the BER that we illustrate with some simulations.

Comparison of OFDM and SC-FDE for VLC Systems with a Nonlinear LED Model

Abstract: Single-carrier frequency domain equalization (SC-FDE) and orthogonal frequency division multiplexing (OFDM) are two attractive technologies for visible light communications (VLC). In this paper, we analyze these two schemes in VLC system with direct current (DC) biasing. We investigate the bit error rate (BER) performance of SC-FDE and OFDM schemes with a memory nonlinear light-emitting diode (LED) model in a simulated indoor scenario. The system performance of both schemes and the impact of LED nonlinear distortion are compared and discussed. We found through numerical simulations that the OFDM scheme exhibits a better BER performance compared to the SC-FDE scheme although it has a higher peak-to-average power ratio (PAPR).

A Method of Phase Noise Estimation and Compensation Based on Golay Sequence in Time Domain for SC-FDE Millimeter-Wave Communication Systems

Abstract: A method of phase noise (PHN) estimation and compensation based on the Golay sequence is proposed in the article for single-carrier frequency-domain equalization (SC-FDE) Millimeter-Wave Systems. First, the channel is estimated based on the correlation with the Golay sequence. Then, the 64-length cyclic prefix (CP) between data blocks is adopted to estimate the common phase error (CPE) of the data blocks after equalization in the frequency domain. Finally, the PHN estimation and compensation after equalization is computed so that the phase deviation can be avoided. Different from previous researches, the algorithm is developed in SC-FDE Systems, using a system symbol transmission rate of 2.4576G sym/s, 64QAM modulation, and each transmission frame structure of 9600 data blocks. In this case, the effect of PHN will be magnified. 1/2 LDPC encoding and decoding are also introduced into this system to further improve the performance. Compared with present algorithms, the algorithm shows better comprehensive performance in MSE of PHN before and after equalization, with the complexity of integrated computation taken into consideration.

An Efficient QAM Detection via Nonlinear Post-distortion for SC-FDE Transmission under PA Impairments with Memory.

Abstract: In this paper, we propose a novel receiver structure for single carrier transmission with frequency domain equalization (FDE) that is exposed to power amplifier (PA) nonlinearities. A two stage approach is adopted, in which linear communication channel is equalized at first stage and it is followed by a post-distortion unit where nonlinear distortion is reduced. In literature, there are some techniques that are proposed for the memoryless compensation of nonlinear distortion together with FDE. However, in this study, we show that even if a memoryless nonlinearity is utilized, received signal is impaired by nonlinear inter-symbol interference (ISI). Therefore, we propose a class of post-distortion techniques, which use neighbouring received symbols to supress the nonlinear interference. Two different, post-distortion techniques, namely Gaussian process regression (GPR) and neural network (NN) based post-distorters, are considered. In addition, a receiver structure, combining outputs of fractional delayed bank of FDE's, is proposed to overcome performance degradation problem of FDE for highly frequency selective channels under nonlinear distortion. Performance of the proposed techniques are compared with that of the state-of-the-art techniques in terms of bit error rate (BER) and achievable information rate (AIR) metrics via simulations. Simulation results demonstrate that GPR and NN based post-distortion methods outperform state-of-the-art techniques. Lastly, it is observed that proposed receiver architecture performs very close to linear system with the help of proposed fractionally delayed FDE bank.

Average PER Prediction Based on Statistical CSI for SC-FDE Systems

Abstract: In this paper, we propose a method to predict the average packet error rate (PER) of a coded single carrier frequency domain equalization (SC-FDE) transmission scheme after minimum mean square error (MMSE) equalization when statistical channel state information (SCSI) is available. We assume that the encoded bits are spread over several blocks (which may correspond to a frequency hopping system for instance) which are transmitted under independent multipath random fading channel realizations. The PER prediction technique used here is based on the effective SNR mapping approach that gathers the signal to noise ratios (SNR)s of the different blocks into one single value. The novelty of this contribution resides in the fact that we propose a new expression for the effective SNR that allows us to approximate its statistical distribution with a beta random variable whose parameters depend on the SCSI. This approach enables us to compute the PER prediction with a lower complexity that the one required by conventional approaches. Moreover, we show by simulations that the accuracy of our solution is very close to the conventional ones, typically within 1 dB of error for PER of the order of $10^{-2}$.

SC-FDE system signal detection method based on adaptive integrated deep learning model

Abstract: The invention relates to a signal detection method based on an adaptive integrated deep learning model. An integrated long short term memory (LSTM) neural network is adopted to replace a channel estimation and frequency domain equalization part of a receiving end of an SC-FDE system in an end-to-end mode. The data set required for training the LSTM neural network is composed of the characteristicsof the received signals extracted by the receiving end and the labels distributed to the constellation diagram corresponding to the modulation mode used by the sending end. In order to ensure the reliability of the system, a linear discriminant analysis (LDA) algorithm is adopted to reduce the dimension of the feature information, and the multi-dimensional feature information is used as the inputof the integrated model. In order to improve the adaptability of the system, the signal power of different sub-channels is adopted as an adaptive factor, and adaptive integration is carried out on the output of each sub-carrier at the network output end. According to the method, for different communication systems, only the data set needs to be generated according to the used system framework, the model obtained through training is used for replacing a certain part of the communication system, and high generalization is achieved.

A State-space Approach for MIMO Channel Tracking in SC-FDE Transmissions

Abstract: In this paper we consider a multi-input multi-output (MIMO) channel subject to time variations. These channel variations are due to the presence of a Doppler term which imposes a phase rotation on the original channel impulse response (CIR). On one hand, modern equalization schemes require the knowledge of the CIR or, equivalently, the channel frequency response (CFR). On the other hand, channel estimation procedures consume significant resources, particularly when transmitting training sequences. Therefore, we propose the use of a statespace approach, namely the extended Kalman filter (EKF), to interpolate the channel estimates obtained during the training stage onto the data transmission stage. Our approach is validated considering single-carrier frequency-domain equalization (SCFDE) transmissions.

SC-FDE SC-FDE Transceiver System Robust Narrowband Interference and Low Pilot Overhead

Abstract: The present invention relates to an SC-FDE transmission/reception system for coping with a narrowband interference signal and reducing a pilot overhead. The system comprises: a receiver for receiving a pilot signal in a narrowband jammer environment; a transmitter for transmitting a pilot signal; a CP remover for removing a CP from the received pilot signal; an FFT; and a channel estimator. According to the present invention, even in the presence of a jammer, frequency domain channel estimation is possible without time domain channel estimation.

Single Carrier Lagrange Vandermonde Division Multiplexing

Abstract: While fifth generation (5G) wireless networks stick to the orthogonal frequency division multiplexing (OFDM), next generation networks will improve major key performance indicators (KPIs) and support diverse use cases. Among KPIs, new levels of mobile performance with lower complexity transceivers are expected. To this end, we propose the single carrier Lagrange Vandermonde division multiplexing (SC-LVDM) that generalizes the single carrier frequency domain equalization (SC-FDE) and harvests the channel diversity. The SC-LVDM receiver blocks are build using the signature roots that have been judiciously selected to 1) guaranty the perfect recovery of the transmitted signals, 2) perform the one-tap equalization while 3) keeping the complexity low. Carrying out the simulations in frequency selective channels, our proposed scheme outperforms the SC-FDE where the performance results are shown in terms of bit error ratio (BER). SC-LVDM achieves a signal-to-noise ratio gain of 10 dB over the SC-FDE when applying the gradient descent algorithm for signature roots optimization.