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Underwater acoustic (UA) channel is often affected by strong impulsive noise. In this paper, a compressive sensing based iterative algorithm is proposed to accurately estimate the channel state information and mitigate the impulsive noise, which is important to ensure high-speed data transmission in UA orthogonal frequency-division multiplexing communication systems. By exploiting the sparsity of...
In this paper, we present the baseband receiver design for IEEE 802.11ah. We study several key receiver algorithms, including coarse frequency offset estimation and coarse timing synchronization, fine frequency offset estimation, fine timing synchronization, channel estimation and MIMO equalization. For channel estimation, we propose to use decoded SIG field to improve its estimation. To further improve...
The carrier frequency offset(CFO) in OFDM system is one of the key factors that affect the performance of wireless communication. Based on the analysis of the CFO estimation algorithm, this paper presents FPGA implementation scheme in the problem of OFDM fractional CFO estimation using pilot-based algorithm, including CFO estimation and CFO compensation. The circuit modules in the program were written...
In the paper, operation algorithms of the N-OFDM modem for channels with the Additive White Gaussian Noise (AWGN) are considered. The algorithms are based on the Hartley transform under the optimal demodulation by the estimation of the received signals amplitudes using the Cauchy method. The experimental results for interference immunity estimation are provided for different values of spacing frequencies...
A novel blind time-frequency joint synchronization based on the cyclostationary of orthogonal frequency division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) systems is conceived in multipath channels conditions. The cyclic cumulants of OFDM/OQAM signals are derived firstly, symbol timing offset (STO) and carrier frequency offset (CFO) are estimated by employing two groups...
Air traffic and on-board data access services are expected to have tremendous growth, possibly even exponentially in the near future. In order to meet these challenges, Orthogonal Frequency Division Multiplexing (OFDM) can be deployed to enable the increased usage of broadband services on-board. The Doppler effect is one of the major issues in implementing OFDM modulation in aeronautical satellite...
Transmitting large amounts of data such as videos underwater is an important yet challenging problem in the harsh underwater environment in which radio-frequency waves are absorbed for distances above a few tens of meters, optical waves require narrow laser beams and suffer from scattering and ocean wave motion, and acoustic waves—while being able to propagate up to several tens of kilometers—lead...
Direction of arrival (DoA) estimation in the massive antenna systems with reduced hardware and signal processing complexity is a challenging task. To address the issue, this paper presents an approach to estimate the DoA in a large number of antennas system combined with an electromagnetic (EM) lens. An EM lens has the ability to focus the received signal energy as a function of the angle of arrival...
In this paper, we propose and analyze new spectrum-efficient communication and radar sensing systems (named ComSens) operating in full-duplex mode with frequency division duplex scheme. ComSens simultaneously use the pilot overhead for channel estimation and radar sensing. The performances of ComSens are analyzed in terms of ergodic communication data-rate and radar estimation rate. The total system...
A rugged method for distance estimation based on an OFDM signal combined with the Zadoff-Chu sequences is introduced. A software algorithm extracts a coarse distance in time domain exploiting the Zadoff-Chu properties. The distance, then, is fine adjusted evaluating the time offset from the subcarriers phase. Several tests were performed in laboratory considering a very harsh indoor environment and...
Underwater acoustic (UWA) channel estimation based on fast Bayesian matching pursuit (FBMP) is investigated in this paper. In UWA multipath channel, the positions of UWA channel taps usually obey the Bernoulli distribution, while the coefficients of UWA channel taps obey the complex-valued Gaussian distribution. Such knowledge of distribution is considered as a prior for UWA channel estimation based...
Generalized frequency division multiplexing (GFDM) with the flexible structure is one of the promising candidates for the fifth generation wireless communication system. This paper focuses on training sequence design that is used in the estimation of in-phase(I) and quadrature(Q) imbalance parameters on GFDM receivers as well as frequency selective channel. Combining with the structure of low complexity...
Residual BER — error floor is the ultimate metrics for the end-to-end transmission performance, but in practice can be assessed only by out-of-service tests, which network operators in particular try to avoid best they can, preferring in-service practical test methods. In this regard, constellation analysis is an excellent tool to not only identify and visualize various error generating analog impairments...
This paper analyzes the effect of bubble noise and Doppler shift in an underwater acoustic communication in addition to the influences by ambient noise and severe multipath propagation. Here Bubbles are assumed to be formed due to breaking of waves under strong winds. The bubble layer thus formed alters the speed of the sound in the field. The changed speed of the sound in the field, results in transmission...
In this study joint estimation of the symbol timing offset (STO), and channel impulse response (CIR) of each active user under the presence of the carrier frequency offset (CFO) is considered for the uplink of an orthogonal frequency-division multiple access (OFDMA) system. A new method based on the compressed sensing (CS) framework using pilot symbols is proposed for the joint estimation of the STO...
Orthogonal Frequency Division Multiplexing (OFDM) technology is the preferred technique for low voltage power line communication because it can combat the frequency selective fading caused by multi-path transmission effectively. And channel estimation is one of the crucial domains of OFDM. In this paper, an improved Linear Minimum Mean Square Error (LMMSE) method is proposed which chooses the fist...
Multi-carrier (MC) multiple-input multiple-output (MIMO) radar offers an additional degree of freedom in the array optimization through the carrier frequencies. In this paper, we study the MC-MIMO array optimization with respect to the direction of arrival (DOA) estimation based on the Cramer-Rao bound (CRB). In particular, we choose the transmit and receive antenna positions as well as the carrier...
It is indispensable to take a low complexity and high accuracy channel estimation algorithm into account under rapidly growth in wireless communication. In this paper, we propose an algorithm for channel estimation using complementary sequence (CS). By utilizing the fantastic autocorrelation property of CS, time domain channel estimation can be easily achieved. We analyzed the complementary sequence,...
The conventional algorithm of channel estimation based on IEEE802.11ac is Least Square (LS) algorithm, which uses the Very High Throughput-Long Training Field (VHTLTF) of frame header as training sequence. While the conventional algorithm does not take into account the effects of noise and the varying characteristics of channel in time domain. In order to describe the slow change of channel in time...
In this paper, we propose a block decision-aided (BL-DA) laser phase noise (LPN) estimation algorithm for coherent optical OFDM (CO-OFDM) systems. The OFDM symbols are divided into several blocks and the LPN estimation and compensation procedure is performed based on the decisions between these blocks. The proposed BL-DA algorithm can be applied for higher LPN estimation while at the same time ensuring...
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