MIMO-OFDM Communication Systems Research Articles

Attention-Aided Autoencoder-Based Channel Prediction for Intelligent Reflecting Surface-Assisted Millimeter-Wave Communications

Sixth-generation (6G) wireless communication networks will provide larger coverage and capacity with lower energy consumption and hardware costs than 5G. Intelligent reflecting surface (IRS)-aided millimeter-wave massive MIMO OFDM communication is a new technology that intelligently manipulates electromagnetic waves. This has recently attracted much attention given its potential to manage the wireless propagation environment at low hardware costs and with minimal energy usage. However, channel prediction is complicated by the fact that IRS is rarely equipped with power amplifiers, various radio frequency chains, or a significant number of reflecting components. In this paper, we propose a convolutional denoising autoencoder model and investigate a joint attention mechanism for channel prediction. Then, we employ the attention mechanism to identify features of channel subcarrier interference to improve the channel prediction performance. Long-range dependent specificity is captured through the attention mechanism to generate useful features from the input signal. The encoder-decoder design of the autoencoder serves as a dimensionality reduction method that enables the autoencoder to predict the spatial and temporal distribution features of continuous signals by exploiting the extraction of sequence features from the model. Numerical results show that the proposed algorithm significantly improves the performance of IRS-aided millimeter-wave massive MIMO OFDM communication systems compared with previous methods.

Walsh transform-based non-linear equalization algorithm for enhancing the efficiency of MIMO-OFDM communication system

Walsh transform-based non-linear equalization algorithm for enhancing the efficiency of MIMO-OFDM communication system

Emergence of energy optimization in MIMO-OFDM communication system with hybrid teamwork-grasshopper optimization

Abstract In the application of mobile multimedia and wireless communication system needs an enormous amount of data. Due to the usage of a huge data rate, a superior amount of energy is offered to BER, which effectively enhances the entire energy consumption rate in the system, and also, the generation of CO2 emission leads to global warming. Hence, professionals searched for energy-efficient approaches for attaining enhanced data rates in wireless communication systems. Then, professionals observed the energy efficacy as well as QoS as an essential factor in developing and validating the mobile multimedia communication system that has created superior interest in recent days. In this paper, energy-efficient models are suggested for MIMO-OFDM mobile multimedia communication systems with statistical QoS constraints. Hence, this research suggests a new MTGSO for energy optimization in the MIMO-OFDM mobile multimedia communication system to improve spectral efficiency and system capacity. Thus, the empirical result of the designed method attains better performance regarding average power constraints, achieving 29.8 %, 21.3 %, 123.8 %, and 4.2 % enhanced than SSO, FOA, GSO, and TOA. This energy-efficient hybrid algorithm for MIMO-OFDM proves its efficiency in terms of various performance measures and statistical measures.

An Excavated PSO-SQP Mechanisms for an Effective Radar Transmission in MIMO-OFDM Communication Systems

An Excavated PSO-SQP Mechanisms for an Effective Radar Transmission in MIMO-OFDM Communication Systems

АЛГОРИТМ ОБРАБОТКИ ПРОСТРАНСТВЕННО-ВРЕМЕННЫХ СИГНАЛОВ НА ОСНОВЕ СИСТЕМЫ MIMO-OFDM В УСЛОВИЯХ АКТИВНЫХ ПОМЕХ

An algorithm for processing space-time signals based on a MIMO-OFDM communicationsystem in the presence of active interference is described. Theoretical calculations are given, thedetection of approaches that often cause the bandwidth of the communication channel when leavinga point source of active interference. The task is relevant in the conditions of dense urban development,as well as the steadily growing need to improve noise immunity and communicationquality without bandwidth coverage. To process information in a MIMO-OFDM system withoutinterference, engineers mainly use the criterion of maximum signal-to-noise ratios, however, in thepresence of active interference, the Wiener criteria. It measures the minimum RMS pilot measurementerror in OFDM. In this case, a signal receipt of a monetary amount, an eigenvector is detected,weight processing is performed, a signal is received that occurs according to the minimumerror criterion. An orthogonal frequency division multiplexing technology with pilot subcarriers isreduced at the receive frequency in frequency and modulation code. Thresholding was found in thedecrypted code, produced by the RMS comparison. The arrival of big money comes from this ownnumber. Pilot-based enumeration searches for the minimum acceptable error. The eigenvector ofthe found signal will be for weight processing. Experiments are carried out to detect a signal in acommunication channel with and without adaptation using the Wiener criterion and the presenceof interference with two types of modulation (QAM-4, BPSK). The results show that the adaptationimproves the BER (bit error rate) state along the entire line of the curve and for all SNRs.The developed algorithm can be used for communication and control systems of unmanned aerialvehicles in the presence of active interference.

Operational Characteristics of Square-Law Combining Energy Detector in MIMO-OFDM Cognitive Radio Systems

To ensure effective spectrum usage, cognitive radio networks (CRNs) are being investigated extensively. The important function of CRNs is spectrum sensing (SS). This is the process of sensing the unused frequency spectrum and deciding whether the signal transmission of a primary user (PU) exists. In this work, the results of a performance analysis related to detecting PU signals using the energy detection (ED) SS method realized by employing the square-law combining (SLC) technique are presented. The assessment of the effectiveness of the ED method is performed in relation to prominent communication technology based on Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO) transmissions. Due to the impact of changes in the noise power of the PU signal, referred to as noise uncertainty (NU), the MIMO-OFDM transmission in a real communication environment cannot guarantee accurate sensing performed by employing ED based on the SLC method at the secondary user (SU). More precise SS can be achieved if dynamic detection threshold (DDT) changes are employed according to the channel conditions impacted by NU. Thus, this work investigated the effect of NU variations and DDT adjustments on the detection probability for various levels of false alarm probability. This interdependence is presented as receiver operating characteristic (ROC) curves. A mathematical model including different operational parameters was developed to define the fundamental parameters of the ED method based on the SLC approach. Using the developed mathematical model, an algorithm was created which simulates SLC ED processes using DDT in single-input single-output (SISO)- and MIMO-OFDM communication systems affected by NU. Based on the simulation results, comprehensive analyses of the impact of versatile DDT adaptations and NU variations on the shape of the ROC curves for the ED process performed with different numbers of transmitting and receiving antenna, modulation techniques, detection sample numbers, PU transmitting powers, and SNR values are presented.

Energy efficient equalizer design for MIMO OFDM communication systems using improved split complex extreme learning machine

Energy efficient equalizer design for MIMO OFDM communication systems using improved split complex extreme learning machine

Constrained Tensor Decomposition-Based Hybrid Beamforming for Mmwave Massive MIMO-OFDM Communication Systems

Hybrid beamforming design for OFDM systems is hugely challenging since their analog precoders and combiners are shared among all subcarriers. This paper proposes a novel two-stage joint hybrid precoder and combiner design for maximizing the average achievable sum-rate of frequency-selective millimeter-wave massive MIMO-OFDM systems. In the proposed approach, the analog precoder and combiner design is formulated as a constrained Tucker2 tensor decomposition problem, which allows maximizing the sum of the effective baseband gains over every subcarrier while suppressing inter-user and intra-user interferences. The solution is obtained by a projected alternate least-square-based algorithm, which is suitable for both single-user (SU) and multiuser (MU) systems. The digital precoder and combiner for SU systems is obtained from the effective baseband channel' SVD. In contrast, for MU systems, it is obtained from the regularized channel diagonalization method, which balances multiuser interference and noise suppression. Numerical simulation results validate the effectiveness of the proposed method.

Performance evaluation of chaotic spreading codes in massive MIMO OFDM system

Background/Objectives: Wireless communication systems are growing towards the implementation of 5G communication systems to satisfy the demand of services in future. OFDMA has some shortcoming like one or more subcarriers of OFDM are completely affected due to the characteristic of the transmission channel. Spreading scheme has been introduced to combat the aforementioned issue. Furthermore, communication channels are affected by multipath fading which changes the amplitude of the received signal. This fading severely affects the communication systems. Therefore, it is essential to develop a more robust technique for higher data transmission and larger throughput. The main objective of this study is to design a massive MIMOOFDM system for secure transmission of data. Chaos based sequence is used to spread the data before transmission which will solve intercell interference and improve the security of data. Methods: This study presents a chaos based massive MIMO-OFDM communication system. The proposed chaos based massive MIMO-OFDM system is implemented and its efficacy is evaluated by computing bit error rate. The effectiveness of the proposed system is investigated by varying the parameters including modulation methods such as PSK and QAM, number of users 10, 20 and 30 and spreading factor of 5, 10 and 15. Findings: Results clearly proved that the proposed system provides exceptional performance with 16QAM modulation scheme, 10 users at high spreading factor value of 15. Novelty: The uniqueness of the proposed system is with enhanced performance and usage of novel modulation scheme by varying the spreading factor value, when compared to its peers. Keywords: Communication system; spreading code; chaotic code; massive MIMO-OFDM; bit error rate

Non-linear equalisation and CFO compensation for MIMO-OFDM communication systems based on DWT

ABSTRACT Equalisation is one of the most important algorithms to improve the Bit-Error-Rate (BER) performance in communication systems. In general, equalisation can be classified into two categories: linear and non-linear equalisation. The linear equalisers include Zero Forcing (ZF), and Minimum Mean Square Error (MMSE) equalisers. The non-linear equalisers include ZF and MMSE equalisers that are based on Successive Interference Cancellation (SIC). The ZF equaliser suffers from noise enhancement. The MMSE equaliser can mitigate the noise enhancement using the estimated Signal-to-Noise Ratio (SNR). The ZF-SIC and MMSE-SIC equalisers suffer from error propagation, and high computational complexity, respectively. In this paper, the Orthogonal Frequency Division Multiplexing (OFDM) system is modulated and demodulated using Inverse Discrete Wavelet Transform (IDWT), and DWT instead of Inverse Discrete Fourier Transform (IDFT) and DFT, respectively. Also, we propose a Joint Low-complexity Regularised ZF-SIC (JLRZF-SIC) equaliser that jointly performs the equalisation, and Carrier Frequency Offset (CFO) compensation with lower complexity using banded matrix approximation. The proposed JLRZF-SIC equaliser can accomplish the equalisation, and CFO compensation processes with low-complexity compared to the corresponding MMSE-SIC equaliser. Simulation results show that the proposed JLRZF-SIC equaliser outperforms different linearand non-linear equalisers.

The Architectural Optimizations of a Low-Complexity and Low-Latency FFT Processor for MIMO-OFDM Communication Systems

Fast Fourier Transform (FFT) processor is a paramount signal processing component in MIMO-OFDM wireless communication systems. Furthermore, novel applications introduced in 5G incur much more rigorous requirements for FFT designs including complexity, latency, and re-configurability. This paper presents the VLSI architecture design and circuit implementation of a FFT processor that is jointly optimized for low-latency, low-complexity, and configurability. Specifically, the proposed architecture processes two data streams concurrently and supports power-of-two FFT sizes from 64 to 2048 symbols. Moreover, a novel data-processing sequence is presented so that data streams are processed in a time-multiplexing manner and an efficient hardware-sharing architecture can be designed. In addition, a highly efficient I/O reorder mechanism is proposed so that the memory elements are shared between processing stages and the efficiency for utilizing memory components is enhanced. Based on the architectural optimizations, two FFT processors are realized. The ultra-low latency design achieves a latency of 4 μs with 41% area reduction compared to the comparable designs. On the other hand, the ultra-low complexity structure achieves a latency of 25 μs with 24% area reduction compared to the state-of-the-art implementations.

Joint equalization and CFO compensation for performance enhancement of MIMO-OFDM communication systems using different transforms with banded-matrix approximation

The conventional Zero Forcing (ZF), and Minimum Mean Square Error (MMSE) equalizers suffer from noise enhancement, and high complexity, respectively. Moreover, the MMSE equalizer needs the estimation of the Signal-to-Noise Ratio (SNR) to work properly. In this paper, we propose Joint Low-Complexity Regularized ZF (JLCRZF) equalizers based on Successive Interference Cancellation (SIC) for Orthogonal Frequency Division Multiplexing (OFDM). The Bit-Error-Rate (BER) performance of the OFDM system model is tested using different transforms such as Discrete Fourier Transform (DFT), Discrete Sine Transform (DST), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT). The proposed JLCRZF-SIC equalizers jointly perform the equalization and Carrier Frequency Offset (CFO) compensation processes with lower complexity using banded-matrix approximation. Simulation results prove that the proposed JLCRZF-SIC equalizers outperform different linear, and non-linear equalizers, especially in the presence of estimation errors.

Performance evaluation for medium voltage MIMO-OFDM power line communication system

Power line communication (PLC) provides intelligent electrical functions such as power quality measurement, fault surveys, and remote control of electrical network. Most of research works have been done in low voltage (LV) scenario due to the fast development of in-home PLC. The aim of this paper is to evaluate the link-level performance of a medium voltage (MV) MIMO-OFDM communication system based on transmission link under underground power line channel. The MIMO channel is modeled as a modified multipath model in the presence of impulsive noise and background noise. We first perform a measurement on the practical MV MIMO channel parameters for a section of buried cable of 1 km long in Ganzhou city, Jiangxi province, China. Based on the measured channel, we design the frame structure based on an IEEE standard for broadband over power line networks [1] to support MV MIMO-OFDM transmission. According to designed frame structure, we design an encoder and a decoder for a dual binary tail-biting turbo code and optimize some key decoder parameters for low bit error rate performance. Finally, the link-level performance for both spatial multiplexing and spatial diversity are evaluated. Numeral results show that MV MIMO-OFDM is a promising approach to provide both high data rate and link reliability for PLC.

Weighted Neuro-Fuzzy Hybrid Algorithm for Channel Equalization in Time Varying Channel

In MIMO-OFDM communication systems, accurate and specific channel estimation and equalisations are plays a major role. In this paper, we use weighted neuro-fuzzy hybrid (WNFH) channel estimation algorithm for channel equalisation. The pilot is designed based on combination of neural network and fuzzy logic system. Scaled conjugate gradient (SCG) is mutual with group search optimiser (GSO) algorithm along with; the training procedure of neural network is prepared using the hybrid training algorithm. In the transmitter section, the projected system contains quadrature amplitude modulation (QAM) and transmitter. By considering the channel prediction error to recover the performance of symbol detection the minimum mean-square error (MMSE) estimation design is accomplished. To reduce the MMSE of channel estimation and the calculated pilot sequences present great superiority in MIMO-OFDM system. Experimentation outcome shows that the channel assessment is supportive.

Channel Estimation and Equalization of Underwater Acoustic MIMO-OFDM Systems: A Review Estimation du canal et l’égalisation des systèmes MEMS-MROF acoustiques sous-marins: une revue

High-speed underwater acoustic (UWA) communication is challenging due to limited bandwidth, extended multipath spread, severe Doppler effect, and large transmission loss. The use of multiple transducers at both transmitter and receiver increases the spatial diversity of the system, and orthogonal frequency-division multiplexing (OFDM) solves the problem of limited bandwidth due to its high spectral efficiency. Thus, the combination of multiple-input multiple-output (MIMO) and OFDM shifts the UWA communication to a whole new level; however, at the same time, it also increases the design challenges for the development of such systems. Intersymbol interference, intercarrier interference, and cochannel interference are introduced in the received signal by the extended multipath and Doppler shifts along with different types of noises due to the noisy acoustic channel. Therefore, many channel estimation and equalization schemes are developed for the UWA MIMO-OFDM communication systems. In this paper, these schemes are thoroughly reviewed, summarized, categorized, and compared with other similar algorithms in terms of complexity and performance while pointing out the prevailing research problems.

Hardware Implementation of the Compressed Beamforming Weights Calculation for the Practical Wireless MIMO-OFDM Communication System

The compressed beamforming weights (CBWs) feedback is used in the IEEE 802.11n/ac WLAN, an example of the practical beamforming multiple input multiple output-orthogonal frequency division multiplexing system, to reduce the amount of feedback information so that the beamformee can respond rapidly to the beamformer. The CBW associated with each sub-carrier includes the quantized angles obtained from QR-decomposition (QRD) of the right singular vectors of each corresponding channel matrix. Efficient matrix QRD and singular value decomposition (SVD) together are therefore desirable for computing the CBWs associated with all sub-carriers. Considering the exemplary antenna configuration of 4 beamformer and 2 beamformee antennas, we propose to apply the same matrix triangulation to compute the SVD of a 2-by-4 matrix and to compute the QRD of a 4-by-2 matrix. We can achieve gate count reduction by exploiting only one matrix triangulation module in our architecture. The VLSI implementation results under the TSMC 90-ns CMOS technology reveal that our architecture requires 194.25K gates while operating at frequency 200.75 MHz. Additionally, with better normalized matrix throughput and gate efficiency, our architecture outperforms one earlier architectural design to compute the CBWs.

Effect of Doppler Shift frequency on the performance of 2x2 OSTBC-OFDM System

In this paper the effect of the Doppler shift frequency on the performance of the 2x2 MIMO system has been studied and presented. A system with two transmits antennas and two receive antennas has been used. Accurate and efficient channel estimation which plays a key role in MIMO-OFDM communication system has been implemented using pilots and training sequences. To guarantee a much more reliable and robust transmission over a hostile wireless channel, a convolutional codes have been added to the 2x2 MIMOOSTBC-OFDM system as a Forward Error Correction (FEC) codes. Two types of convolutional code rate have been used (1/2 and 2/3) depending on the type of modulation. To make this code more robustness against channel impairments; interleaving has been used with the convolutional code. The system has been evaluated for four types of QAM modulation (4-QAM, 8-QAM, 16-QAM, and 64-QAM) as a baseband modulation. The system has been evaluated for three different values of Doppler Shift frequency (5, 50, and 100) Hz. The simulation results demonstrated the performance of the systems over Flat and multi-path Frequency-Selective fading channels, assuming the channels are with No Line Of Sight (NLOS), so the channels are Rayleigh fading channels. The results show that when the Doppler Shift Frequency increased the BER also increases and when Doppler Shift Frequency is 5Hz, the performance of the system is better for four types of QAM modulation and in the two cases of Flat and multi-path Frequency-Selective fading.

EFFICIENT ARCHITECTURE OF COMBINED RADIX DIF ALGORITHM FOR MIMO-OFDM APPLICATION

An efficient design of combined radix-2 Single path Delay Feedback (SDF)-Single path Delay Commutator (SDC)-Decimation In Frequency (DIF) algorithm is proposed in this paper which can be used in Orthogonal Frequency Division Multiplexing (OFDM) with Multiple Input Multiple Output (MIMO) applications. The MIMO-OFDM communication system has tremendous and swift growth in various applications used over last decade, especially wireless and digital communication where adaptability, reconfigurability, less chip size, hardware improvements, and lower power consumption are mandatory requirements during communication. The main aim of this structure is to improve the performance of combined Fast Fourier Transform (FFT) for the MIMO-OFDM system and also to reduce the complexity of the hardware.

A New Fuzzy Key Generation Method Based on PHY-Layer Fingerprints in Mobile Cognitive Radio Networks

Classical key generation is complicated to update and key distribution generally requires fixed infrastructures. In order to eliminate these restrictions researchers have focused much attention on physical-layer (PHY-layer) based key generation methods. In this paper, we present a PHY-layer fingerprints based fuzzy key generation scheme, which works to prevent primary user emulation (PUE) attacks and spectrum sensing data falsification (SSDF) attacks, with multi-node collaborative defense strategies. We also propose two algorithms, the EA algorithm and the TA algorithm, to defend against eavesdropping attacks and tampering attacks in mobile cognitive radio networks (CRNs). We give security analyses of these algorithms in both the spatial and temporal domains, and prove the upper bound of the entropy loss in theory. We present a simulation result based on a MIMO-OFDM communication system which shows that the channel response characteristics received by legitimates tend to be consistent and phase characteristics are much more robust for key generation in mobile CRNs. In addition, NIST statistical tests show that the generated key in our proposed approach is secure and reliable.

Main-Branch Structure Iterative Detection Using Approximate Message Passing for Uplink Large-Scale Multiuser MIMO Systems

The emerging large-scale/massive multi-input multioutput (MIMO) system combined with orthogonal frequency division multiplexing (OFDM) is considered a key technology for its advantage of improving the spectral efficiency. In this paper, we introduce an iterative detection algorithm for uplink large-scale multiuser MIMO-OFDM communication systems. We design a Main-Branch structure iterative turbo detector using the Approximate Message Passing algorithm simplified by linear approximation (AMP-LA) and using the Mean Square Error (MSE) criterion to calculate the correlation coefficients between main detector and branch detector for the given iteration. The complexity of our method is compared with other detection algorithms. The simulation results show that our scheme can achieve better performance than the conventional detection methods and have the acceptable complexity.