Wireless OFDM Systems Research Articles

Effective deep learning-based channel state estimation and signal detection for OFDM wireless systems

Abstract Deep learning (DL) algorithms can enhance wireless communication system efficiency and address numerous physical layer challenges. Channel state estimation (CSE) and signal detection (SD) are essential parts of improving the performance of an OFDM wireless system. In this context, we introduce a DL model as an effective alternative for implicit CSE and SD over Rayleigh fading channels in the OFDM wireless system. The DL model is based on the gated recurrent unit (GRU) neural network. The proposed DL GRU model is trained offline using the received OFDM signals related to the transmitted data symbols and added pilot symbols as inputs. Then, it is implemented online to accurately and directly detect the transmitted data. The experimental results using the metric parameter of symbol error rate show that, the proposed DL GRU-based CSE/SD provides superior performance compared with the traditional least square and minimum mean square error estimation methods. Also, the trained DL GRU model exceeds the existing DL channel estimators. Moreover, it provides the highest CSE/SD quality with fewer pilots, short/null cyclic prefixes, and without prior knowledge of the channel statistics. As a result, the proposed DL GRU model is a promising solution for CSE/SD in OFDM wireless communication systems.

Performance Evaluation of 256 PSK Modulation over Various Channels for MIMO –OFDM Wireless System using Receive Beamforming

The smart antennas are widely used for wireless communication, because it has a ability to increase the coverage and capacity of a communication system. Smart antenna performs two main functions such as direction of arrival estimation (DOA) and beam forming. Using beam forming algorithm smart antenna is able to form main beam towards desired user and null in the direction of interfering signals. In this project Direction of arrival (DOA) is estimated by using MUSIC algorithm. Receive Beam forming is performed by using LMS and LLMS algorithm .In this Paper, in order to perform secure transmission of signal over wireless communication we have used chaotic sequences. This paper evaluates the performance 256PSK over Different channels for MIMO-OFDM wireless system using beam forming with and without LMS and LLMS algorithm. The simulations are carried out using MATLAB.

Multi-stage error control technique for improving 3DV transmission over OFDM wireless systems

Multi-stage error control technique for improving 3DV transmission over OFDM wireless systems

Analytical Framework of CP-Free Multiuser OFDM System for Coordinated Multi-Point at mmWave

In this paper, a coordinated multipoint joint transmission (CoMP-JT) framework at mmWave for a cyclic prefix (CP)-free multiuser OFDM wireless communication system is developed and analyzed. The aim is to provide high-quality service to cell-edge users; otherwise, the cell-users would suffer from significant signal degradation due to undesired interference. The impact of complex Hadamard transform with block diagonalization channel precoding for multiuser interference reduction and designed subcarrier mapping for out-of-band (OOB) reduction are investigated. In addition, the paper studied the input back-off-aided high-power amplifier for peak-to-average power ratio (PAPR) reduction and forward error correction channel coding for improved bit error rate (BER) for cell-edge users at mmWave frequencies. Moreover, signal-to-interference-noise ratio and ergodic achievable rate are estimated both in the presence and absence of CoMP-JT-based transmission technique to verify their significance in terms of transmitted power. Numerical investigations showed an OOB reduction of 312 dB, PAPR reduction from 17.50 dB to 7.66 dB, and improved BER of 1×10−3 in 16-QAM for a signal-to-noise ratio of −6 dB. Hence, the simulation results demonstrated the effectiveness of the developed system.

Electrocardiogram transmission over OFDM system

Abstract Remote patient monitoring is an important area of research. Electrocardiogram (ECG) is a vital health parameter which can be remotely transmitted to monitor the patient’s health. In this field, there are many research directions which include ECG security, patient data hiding in ECG, ECG classification, ECG transmission and reception. In this paper, an effective methodology for ECG transmission over OFDM wireless communication system has been presented. Issues related to transmission of ECG as image have also been discussed. Before ECG is transmitted over OFDM analog ECG signal is to be converted into series of bits for which sampling and quantization has to be performed. The quantization error arises due to number of chosen samples and quantization levels. In this work, it is shown that the quantization error can be brought down to zero using symbolic aggregate approximation (SAX) for data representation. Performance of the ECG transmission using different methodologies has been compared using peak signal-to-noise ratio (PSNR) Structural Similarity Index Metric (SSIM), Bit Error Rate (BER) and Pixel Error Rate (PER).

Preamble based SNR Estimation in Frequency Selective Channels for Wireless OFDM System

Preamble based SNR Estimation in Frequency Selective Channels for Wireless OFDM System

PAPR Reduction Using Interleaver-Assisted PTS Algorithm for OFDM Wireless System

PAPR Reduction Using Interleaver-Assisted PTS Algorithm for OFDM Wireless System

Performance Evaluation of Encrypted Text Message Transmission in 5G Compatible Frequency-domain Subband Superposed Scheme Implemented MIMO OFDM Wireless Communication System

In this paper, an investigative study has been made on the performance evaluation of encrypted text message transmission in 5G compatible multiuser frequency-domain subband superposed (FDSS) scheme implemented MIMO OFDM wireless communication system. The 2×2 multiantenna configured simulated system under consideration incorporates modern channel coding (LDPC and Repeat and Accumulate (RA)) and signal detection (Cholesky decomposition based ZF detection, Group Detection (GD) approach aided Efficient Zero-Forcing (ZF) and Lanczos method based efficient signal detection) techniques. In the scenario of transmitting encrypted text message over AWGN and Rayleigh fading channels, it is noticeable that implementation of Repeat and Accumulate channel coding and Group Detection (GD) approach aided Efficient Zero- Forcing (ZF) signal detection techniques is very much robust and effective in retrieving transmitted text messages for all users.

User Perceived Qos Provisioning for Video Streaming in Wireless OFDMA Systems: Admission Control and Resource Allocation

In this paper, we investigate a joint admission control (AC) and resource allocation (RA) scheme for providing quality of service (QoS) guarantees for video streaming in OFDMA networks. The QoS provisioning is posed as a network utility maximization (NUM) problem. We prove that the QoS requirements are mainly dominated by the average data rate with the aid of diffusion approximation approach, allowing us to decompose the NUM problem into two tractable sub-problems, namely, the AC and the RA sub-problems. We develop an AC algorithm, which enables us to select a maximum user set such that all selected users can meet their QoS requirements related to user perceived video quality during the video playback period. In addition, in order to handle the computational complexity, we further split the RA sub-problem into the constrained Markov decision process associated problems performed at users together with a transmission problem performed at the base station. Correspondingly, we develop a power and sub-carrier allocation algorithm to minimize the average power consumption. The decision of AC is made in a long timescale and depends on the average channel state information (CSI), whereas the decision of RA is made in a short timescale and is subject to both instantaneous CSI and queue state information. Simulation results demonstrate the advantages of the proposed algorithms.

CFO compensation method using optical feedback path for coherent optical OFDM system

Abstract We investigate feasibility of carrier frequency offset (CFO) compensation method using optical feedback path for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Recently proposed CFO compensation algorithms provide wide CFO estimation range in electrical domain. However, their practical compensation range is limited by sampling rate of an analog-to-digital converter (ADC). This limitation has not drawn attention, since the ADC sampling rate was high enough comparing to the data bandwidth and CFO in the wireless OFDM system. For CO-OFDM, the limitation is becoming visible because of increased data bandwidth, laser instability (i.e. large CFO) and insufficient ADC sampling rate owing to high cost. To solve the problem and extend practical CFO compensation range, we propose a CFO compensation method having optical feedback path. By adding simple wavelength control for local oscillator, the practical CFO compensation range can be extended to the sampling frequency range. The feasibility of the proposed method is experimentally investigated.

A Novel Description approach based on sorted rectangles for scheduling information bearing in OFDMA systems

Dynamic time/frequency resource allocation has been widely employed in wireless OFDMA systems. In such mechanisms, sophisticated scheduling decisions need to be conveyed to users and may lead to considerable signaling overhead. In this paper, a new efficient approach, namely, Sorted-Rectangle Description (SRD) is proposed for describing the scheduling decision in an OFDMA frame. SRD first partitions a frame into minimum number of rectangular polygons, namely, rectangular bursts (RB), in which each RB contains the resource units belonging to the same assignment. We show that each RB-partitioned frame is sufficient to be fully reconstructed by the top-left coordinates of each RB in a specific sorted order. Sorting and reconstructing algorithms with linear time complexity in the total number of RBs are also proposed. Simulations based on a multi-user OFDMA system with full-buffer or periodic small-data traffic model are conducted to evaluate the performance of the proposed SRD method under two representative scenarios. The simulation results show that, for the full-buffer traffic model with a proportional fair (PF) scheduler, the proposed description approach can achieve significant reduction of the overhead ratio compared to that of the existing systems and is expected to lead to considerable increase of system throughput. Meanwhile, for the periodic small-data traffic model, it is shown that the proposed description approach can greatly reduce the rate of packet loss due to timeout or buffer overflow and thus provides significant improvement of the system capacity.

Decision-directed iterative methods for PAPR reduction in optical wireless OFDM systems

In this paper, we propose two iterative decision-directed methods for peak-to-average power ratio (PAPR) reduction in optical-orthogonal frequency division multiplexing (O-OFDM) systems. The proposed methods are applicable to state-of-the-art intensity modulation-direct detection (IM-DD) O-OFDM techniques for optical wireless communication (OWC) systems, including both direct-current (DC) biased O-OFDM (DCO-OFDM), and asymmetrically clipped O-OFDM (ACO-OFDM). Conventional O-OFDM suffers from high power consumption due to high PAPR. The high PAPR of the O-OFDM signal can be counteracted by clipping the signal to a predefined threshold. However, because of clipping an inevitable distortion occurs due to the loss of useful information, thus, clipping mitigation methods are required. The proposed iterative decision-directed methods operate at the receiver, and recover the lost information by mitigating the clipping distortion. Simulation results acknowledge that the high PAPR of O-OFDM can be significantly reduced using clipping, and the proposed methods can successfully circumvent the clipping distortions. Furthermore, the proposed PAPR reduction methods exhibit a much lower computational complexity compared to standard PAPR reduction methods.

Estimation of Cyclic Shift with Delayed Correlation and Matched Filtering in Time Domain Cyclic-SLM for PAPR Reduction

Time domain cyclic-selective mapping (TDC-SLM) reduces the peak-to-average power ratio (PAPR) in OFDM systems while the amounts of cyclic shifts are required to recover the transmitted signal in a receiver. One of the critical issues of the SLM scheme is sending the side information (SI) which reduces the throughputs in wireless OFDM systems. The proposed scheme implements delayed correlation and matched filtering (DC-MF) to estimate the amounts of the cyclic shifts in the receiver. In the proposed scheme, the DC-MF is placed after the frequency domain equalization (FDE) to improve the accuracy of cyclic shift estimation. The accuracy rate of the propose scheme reaches 100% at E b/N 0 = 5 dB and the bit error rate (BER) improves by 0.2 dB as compared with the conventional TDC-SLM. The BER performance of the proposed scheme is also better than that of the conventional TDC-SLM even though a nonlinear high power amplifier is assumed.

An Efficient Practical MIMO–OFDM Scheme with Coded Modulation Diversity for Future Wireless Communications

An efficient coded modulation diversity scheme is proposed to improve the performance of multiple-input-multiple-output orthogonal-frequency-division-multiplexing (MIMO---OFDM) systems in frequency-selective time-varying fading channels. By introducing the rotated modulation and space-time-frequency component interleavers, the proposed scheme globally optimizes powerful forward error correction codes, rotated quadrature amplitude modulation, linear precoding MIMO, and OFDM, thus can achieve modulation diversity and space-time-frequency diversities as much as possible. A simple efficient optimal precoder selection criterion is put forward for this scheme. Based on the analysis of average mutual information, optimal rotation angles are given for different modulation and coding schemes, and the superiority of the proposed scheme is proved. Both software simulation and hardware prototype test results also verify that this new scheme can significantly outperform the conventional bit-interleaved coded modulation scheme under the non-ideal channel estimation, which is up to 4.5 dB signal-to-noise-ratio gain. In a word, the proposed scheme is a simple, efficient and robust transmission technique for the future MIMO---OFDM wireless systems.

Oblivious Transfer Over Wireless Channels

We consider the problem of oblivious transfer (OT) over OFDM and MIMO wireless communication systems where only the receiver knows the channel state information. The sender and receiver also have unlimited access to a noise-free real channel. Using a physical layer approach, based on the properties of the noisy fading channel, we propose a scheme for honest-but-curious parties that enables the transmitter to send obliviously one-of-two files, i.e., without knowing which one has been actually requested by the receiver, while also ensuring that the receiver does not get any information about the other file.

Frequency Offset Estimation Algorithm of OFDMA Wireless Communication System Based on Compressed Sensing

The frequency offset problem of OFDMA wireless communication system has been an important obstructive factor for the rapid promotion of this technology. The frequency offset estimation algorithm of OFDMA wireless communication system based on compressed sensing reconstructs the optimized mathematical model of frequency offset. Under the premise of keeping its estimated performance, from the reduction of its computation complexity and the enhancement of real-time performance of the system, it provides an optimized algorithmic approach and thus improves the practicability of algorithm. The compressed sensing algorithm has realized the fast and accurate extraction of the frequency offset parameters, so the overall performance of the system can reach the optimal state.

A Continuous-State Reinforcement Learning Strategy for Link Adaptation in OFDM Wireless Systems

This paper presents a machine learning approach based on the concept of reinforcement learning andMarkov Decision Processes for link adaptation in orthogonal frequency-division multiplexing systemsthrough adaptive modulation and coding. Although machine learning techniques have attracted attentionfor link adaptation, the schemes proposed so far are based on off-line training algorithms, which makethem not well suited for real time and real-world operation. The proposed solution learns the bestmodulation and coding scheme for a given signal-to-noise ratio by interacting with the environment(the radio channel). Unlike the other solutions, it does not rely on an off-line and computationallyintensive training phase. Simulation results show that the proposed technique outperforms the wellknownsolution based on look-up tables for adaptive modulation and coding, and it can potentiallyadapt itself to distinct characteristics of the environment or the receiver radio frequency (RF) front end.

Study of High-Accurate Frequency Estimation in 60GHz Wireless Communication System

A high-accurate frequency estimation algorithm is proposed in the 60GHz OFDM wireless communication system. The phase offset is caused by the carrier frequency offset, and its accumulation has a linear relationship in the time. So the preamble sequence phase can be obtained by the algorithm in this paper, and then the carrier frequency offset value is calculated by the linear regression theory. The 60GHz wireless communication system simulation platform is established. In the platform, the algorithm is simulated with different carrier frequency offset, and the algorithm estimation performance is contrasted with the traditional algorithm. The results show that accuracy of the algorithm has 30dB higher than the auto- correlation algorithm, and that the BER performance of the algorithm is the same as witch in the case of no frequency offset. So the high-accuracy of frequency offset estimation is proposed by the algorithm in the 60GHz wireless communication.

An Iterative MIMO Receiver Employing Virtual Channels with a Turbo Decoder for OFDM Wireless Systems

An Iterative MIMO Receiver Employing Virtual Channels with a Turbo Decoder for OFDM Wireless Systems

Resource Allocation in Downlink OFDM Wireless Systems with User Rate Allowed Regions

In this paper, a novel adaptive resource allocation in downlink orthogonal frequency division multiplexing wireless system is investigated. Different from the conventional algorithms, user rate all...