OFDM Wireless Communication Research Articles

Wavelet OFDM Wireless Communication System for Autonomous Underwater Vehicles Using Loop-Shaped Antennas in Underwater Environments

Wavelet OFDM Wireless Communication System for Autonomous Underwater Vehicles Using Loop-Shaped Antennas in Underwater Environments

Payload symbol-based nonlinear RF fingerprint for wireless QPSK-OFDM devices

Radio Frequency (RF) fingerprinting is one physical-layer authentication method for wireless communication, which uses the unique hardware characteristic of the transmitter to identify its true identity. To improve the performance of RF Fingerprint (RFF) based on preamble with fixed duration, a nonlinear RF fingerprinting method based on payload symbols is proposed for the wireless OFDM communication with the bit mapping scheme of QPSK. The wireless communication system is modeled as a Hammerstein system containing the nonlinear transmitter and multipath fading channel. A parameter separation technique based on orthogonal polynomial is presented for the estimation of the parameters of the Hammerstein system. The Hammerstein system parameter separation technique is firstly used to estimate the linear parameter with the training signal, which is used to compensate the adverse effect of the linear channel for the demodulation of the successive payload symbols. The demodulated payload symbols are further used to estimate the nonlinear coefficients of the transmitter with the Hammerstein system parameter separation technique again, which is used as the novel RFF for the authentication of the QPSK-OFDM device. Numerical simulations have verified the proposed method, which can also be extended to the OFDM signals with other bit mapping schemes.

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.

A new Transmission and Reception Algorithms for Improving the Performance of SISO/MIMO- OFDM Wireless Communication System

The future wireless communication requires a reliable transmission at high data rates, so the transmission over frequency-selective fading Multiple-Input–Multiple-Output MIMO channels become interesting since the capacity of "MIMO" channels expressions enormous gains above that of their essential single-input–single-output "SISO" channels. This paper examines the performance of the Low Complexity Zero Forcing "LCZF" equalizer for both systems single-input–single-output-Orthogonal Frequency Division Multiplexing" SISO-OFDM" and spatially multiplexed-Multiple-Input–Multiple-Output "SM-MIMO-OFDM" with different "QAM" modulations. It is exploring a new algorithm to improve the performance of the "BER", spectral efficiency, and power efficiency and to reduce the complexity of the "RF" communication system under the effect of the Additive White Gaussian Noise "AWGN" and multipath fading channel. It is also improves an efficient channel by developing a Low Complexity Zero Forcing "LCZF" equalizer for both "SISO-OFDM" and "SM-MIMO-OFDM" wireless Communication systems. This is done by proposing a new algorithm at the receiver side to covert the Linear Convolution in to Cyclic Convolution by adding Zero Padding "ZP" to the channel impulse response in such a way to be the same length to the transmitted signal in the time domain which is of length N, where N is the length of "IFFT".

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).

Encrypted Image Transmission over Wireless OFDM Communication Channel

Encrypted Image Transmission over Wireless OFDM Communication Channel

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.

Independence-Checking Coding for OFDM Channel Training Authentication: Protocol Design, Security, Stability, and Tradeoff Analysis

In wireless OFDM communications systems, pilot tones, due to their publicly known and deterministic characteristic, suffer significant jamming/nulling/spoofing risks. Thus, the convectional channel training protocol using pilot tones could be attacked and paralyzed, which raises the issue of anti-attack channel training authentication (CTA), i.e., verifying the claims of identities of pilot tones and channel estimation samples. In this paper, we consider one-ring scattering scenarios with large-scale uniform linear arrays (ULA) and develop an independence-checking coding (ICC) theory to build a secure and stable CTA protocol, namely, ICC-based CTA (ICC-CTA) protocol. In this protocol, the pilot tones are not only merely randomized and inserted into subcarriers but also encoded as diversified subcarrier activation patterns (SAPs) simultaneously. Those encoded SAPs, though camouflaged by malicious signals, can be identified and decoded into original pilots for high-accuracy channel impulse response (CIR) estimation. The CTA security is first characterized by the error probability of identifying legitimate CIR estimation samples. The CTA instability is formulated as the function of probability of stably estimating CIR against all available diversified SAPs. A realistic tradeoff between the CTA security and instability under the discretely distributed AoA is identified and an optimally stable tradeoff problem is formulated, with the objective of optimizing the code rate to maximize security while maintaining maximum stability for ever. Solving this, we derive the closed-form expression of optimal code rate. Numerical results finally validate the resilience of proposed ICC-CTA protocol.

A Hybrid PAPR Reduction Scheme for Optical Wireless OFDM Communication Systems

A Hybrid PAPR Reduction Scheme for Optical Wireless OFDM Communication Systems

Performance Enhancement of Optical Wireless OFDM Communication

Performance Enhancement of Optical Wireless OFDM Communication

Numerically efficient UD filter based channel estimation for OFDM wireless communication technology

Channel estimation and prediction algorithms are developed for use in broadband OFDM data transmission over non-ideal channels. The scalar complex channel coefficients are described by Gauss-Markov AR models of a given order in state space form to model the channel fading statistics. On this basis, the conventional Kalman filtering and prediction algorithm (CKFPA) is presented as a starting point for further development. A novel numerically stable channel estimation algorithm based on the original KFPA solution, the so-called extended Array UD Covariance Filter (eUD-CF) algorithm, is developed. The aspects of a parallel implementation of the suggested algorithm are also considered.

An Empirical Study on the Performance of Wireless OFDM Communications in Highly Reverberant Environments

Reverberation chambers are closed reflective spaces that can emulate highly reverberant electromagnetic environments. The electromagnetic environment is primarily determined by the size of the cavity, effective conductivity, and leakage via apertures. In this effort, we investigate the performance of wireless OFDM communications in relation to the latter two by controlling the loading of a reverberation chamber and the effective aperture into a coupled cavity. A software defined radio measurement platform was used to assess the communication performance through a selection of link-level metrics including error vector magnitude, post processing signal-to-noise ratio, and throughput. The degradation of link quality is quantified for increasingly diffuse environments, as well as the improvement when leveraging a maximal ratio combining receiver diversity scheme. The link quality was found to improve in both the reverberation chamber and the coupled cavity for larger effective apertures. This result was analyzed using a time-dependent model for RF propagation in coupled cavities.

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.

Novel schemes for interference‐resilient OFDM wireless communication

SummaryThis research work introduces some novel techniques for interference‐resilient OFDM wireless communication. Firstly, novel schemes for spatial multiplexing and interference cancelation based on signal subspace estimation are proposed. Secondly, the OFDM system is designed such that it meets three main objectives simultaneously, namely, (i) interference‐resiliency, (ii) throughput maximization, and (iii) energy consumption minimization. Interference‐cancelation techniques in prior art mostly consider maximization of throughput without any focus on energy consumption. On the other hand, the literature in energy minimization is limited to interference‐free environments. Most of the previous techniques also have a drawback that they cannot operate in smart or dynamically changing interference environments. The focus here is on interference‐resilient communication with equal attention to both throughput and energy‐efficiency maximization in dynamic hostile environments. The optimization problem is formulated, and then optimal policies and switching thresholds are found for throughput and energy‐efficient interference‐resilient communication. Methodologies for estimating the channel and jammer conditions and then adapting the transmission strategies accordingly are proposed. Moreover, to have an effective defense against smart jamming scenario, a constant‐payoff scheme is also introduced. Simulation results are compared with previous techniques that demonstrate the efficacy of proposed research. Copyright © 2015 John Wiley & Sons, Ltd.

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.

A Shadowing-aware Automatic Gain Control Scheme for OFDM Wireless Communication System

A Shadowing-aware Automatic Gain Control Scheme for OFDM Wireless Communication System

A New Multipath Signals Receiving Scheme Based on DOA Estimation and Beamforming with Multi-antenna

In the vehicle wireless OFDM communication system, the efiect of multipath fading and Doppler frequency shift in channel may cause frequency selective fading at the frequency domain and intersubcarrier interference in an OFDM symbol, which can reduce the system transmission performance. To solve the above problems, this paper proposes a new receiving scheme to eliminate the multipath efiect at OFDM receiver which is to separate multipath signals and extract the main path based on DOA estimation and beamforming (OMSDB). This scheme takes advantage of spatial information of multipath signals, separates path signals and extracts the main path through beamforming each path signal. OMSDB can efiectively extract the main paththus greatly improves the performance of the receiver. In vehicle multipath channel, simulation results verify the efiectiveness of our proposed scheme.

Application of the Joint Fast Walsh Hadamard-Inverse Fast Fourier Transform in a LDPC Coded OFDM Wireless Communication System: Performance and Complexity Analysis

An efficient low complexity T transform which combines the Walsh Hadamard Transform and Discrete Fourier Transform (DFT) into a single fast orthonormal unitary transform is considered for the application in low density parity check coded orthogonal frequency division multiplexing (LDPC-OFDM) across additive white Gaussian noise channel model and multipath fading channel models. The T-transform is developed through the sparse matrices factorization method using Kronecker product scheme. T-transform based COFDM system, which is capable of reducing peak to average power ratio (PAPR) of the transmitted symbols and improving the bit error rate (BER) performance at a reasonable reduced complexity. Several signaling formats such as Quadrature phase shift keying and 16- ary Quadrature amplitude modulation (16-QAM) are considered. A T COFDM system is described which could provide an alternative to DFT-COFDM system, and is therefore a better alternative to balance the transform complexity, PAPR reduction and system performance. Simulation results are used to examine and compare the complexity, PAR and the BER performance of T-OFDM system and DFT-OFDM system. Numerical results show that the T-COFDM system outperforms the DFT-COFDM based in the multipath channel models.

An Adaptive Phase Tracking Scheme of OFDM Wireless Communication System

This paper proposes a new phase tracking algorithm for the 802.11a system. Since this system illuminates the basic structure of 802.11a system, and introduces the OFDM frame generation principle based the transmitter, phase error estimation and channel estimation. On the basis of this, this paper presents a phase tracking scheme based on adaptive Kalman filter, and then simulates the process based on 802.11a system. The result indicates that the BER has been improved because of this adaptive phase tracking scheme.