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We propose computationally efficient carrier frequency offset estimators for multicarrier underwater acoustic communication using identical pilot tones equi-spaced in the frequency domain. The first estimator uses the phase of the maximal eigenvector of a channel-dependent correlation matrix. Next, the phase of the minimal eigenvector of a channel-independent correlation matrix is combined with the...
A new simplified widely linear iterative equalizer for SC-FDE systems is presented in this paper. The proposed equalizer does not require the computation of the correlation coefficient of the symbol decisions after the first iteration of the equalizer, reducing its complexity. It also has almost the same error performance of its more complex version.
At high SNR, strong correlations in the elements of the MIMO channel can lead to a decrease in channel capacity. In this paper we propose a new methodology to estimate these spatial correlations based on the analysis of the most significant eigenvalues of transmit and receive covariance matrices of the MIMO channel. Our study is based on measurements performed in a university campus with the following...
This paper proposes channel sounders suitable for time and frequency selective channels, i.e., double selective channels, inevitable in underwater acoustic communications (UWAC). As double selective channels in UWAC are highly dependent on their times and places, it is difficult for UWAC to define typical channel models. This paper proposes channel sounders, which transit maximum-length (M) sequence...
This paper is devoted for designing and investigation of some algorithms for direct sequence spread spectrum (DSSS) signal processing with time-shift keying for underwater communication. The results of marine experiments for developed system performance evaluation in shallow sea (depth ∼ 20–30 m) on distances up to 10 km on frequency of 12 kHz (bandwidth of 4 kHz) are supplemented.
In order to improve the channel estimation performance of OFDM based on compressive sensing, the pilot design criterion is studied. The Euclidean distance between the measurement matrix and the identity matrix is used as the definition of mutual coherence of measurement matrix. Then a new pilot design criterion based on the definition above is gotten. Simulation results demonstrate that compared to...
Signal estimation and its performance has always remained a challenge for wireless communication society. New techniques were developed for channel diversity and spectrum utilization. In this paper a new estimation approach based on Kalman state stabilization is proposed min-max, to achieve the objective of higher performance in MIMO system, using time variant interference modeling. A generic approach...
In this paper the impact of exponential correlation model on massive multiple input multiple output (MIMO) channel estimation is analyzed using a large number of antennas in the base station (BS) and a user terminal. We consider pilot-based channel estimation in the UL channel. The Linear minimum mean square error (LMMSE) estimator is used to investigate the effect of correlation factor on the average...
A low-density spatial downlink reference signal (LDS-RS) design is proposed for frequency-division duplex (FDD) massive full-dimensional multiple-input multiple-output (FD-MIMO) systems. By exploiting the spatial correlation between the channels of different antennas, this scheme can efficiently reduce the downlink RS overhead and therefore enhances the achievable spectral efficiency significantly...
In this paper, we studied the massive multiple-input multiple-output (MIMO) system performance with N antenna users and streams can be multiplexed per each user. The spectral efficiency (SE) of uplink and downlink expressions is derived for any N antenna users and these achievable using estimated channels and per user basis minimum mean squared error successive interference cancellation (MMSE-SIC)...
Sparse channel estimation (SCE) in orthogonal frequency division multiplexing (OFDM) systems with large number of virtual sub-carriers and regularly spaced pilots is studied in this paper. Such OFDM systems are present in wireless standards like long term evolution (LTE). We numerically evaluate the performance of popular compressive sensing (CS) algorithms and shows that low complexity CS algorithms...
Channel state information (CSI) is usually necessary for downlink precoding, power allocation, etc. in multiple-input multiple-output (MIMO) systems. When the base stations (BS) are equipped with massive elements, the training overhead required by conventional CSI estimation methods becomes overwhelming, leading to unacceptable loss of spectrum efficiency. In this paper, we investigate pilot design...
Channel estimation is a major overhead factor in large-scale multiple-input multiple-output \mbox{(MIMO)} systems, especially under the high- speed railway scenarios. This paper proposes a position-aided channel estimation scheme for high- speed railway communication systems, where both the transmitter and the receiver are equipped with large-scale antenna linear arrays. By joint spatio- temporal...
Practical generation of secret bits using wireless channel measurements between two terminals is presented in this paper. The model used for this implementation assumes imperfect reciprocity between the channel measurements made by the two terminals in the presence of a passive eavesdropper. The channel measurements (e.g., received signal strength values) are used to estimate the secret key rate in...
Accurate channel state information (CSI) at transmitter is of importance to sufficiently exploit the merits of massive multiple input multiple output (MIMO). Because of the large amount of antennas at base station (BS), the pilot overhead becomes unaffordable, especially in frequency-division duplexing (FDD) massive MIMO systems. To alleviate the overwhelming pilot overhead, a novel channel estimation...
In this work we characterize all ambiguities of the convolution on two fixed finite-dimensional complex vector spaces. It will be shown that the convolution ambiguities correspond to factorization ambiguities in the z-domain, which are generated by swapping their zeros. We use this polynomial description to show a deterministic version of a recently introduced masked Fourier phase retrieval design...
In an uplink massive multiple-input-multiple-output (MIMO) deployment with distributed single-antenna users and a large base-station array, we investigate the performance of low complexity Vertical Bell Laboratories Layered Space Time (C-V-BLAST) and zero forcing (ZF) receivers. Unlike previous work which assumes that the channel is perfectly known, we focus on the realistic scenario where the MIMO...
Network diversity multiple access or NDMA is the family of algorithms with the highest potential throughput in the literature of signal-processing-assisted random access. NDMA uses the concept of protocol-induced retransmissions to create an adaptive source of physical (PHY) layer diversity. This adaptive diversity is used to resolve packet collisions (via signal separation) without the explicit need...
An expression of correlation function of channel coefficients when one-ring scattering model is derived. Based on the correlation function a recursive model of channel coefficients is obtained. A nonrecursive algorithm of channel filtration is derived with Wiener filtration theory.
The proliferation of mobile devices has led to an increasing demand for radio spectrum resources. Currently, the spectrum allocation is static, which has resulted in underutilization of this resource. This situation has motivated the search for solutions to address the spectrum scarcity problem. The channel occupancy rate is a piece of information that can assist the decision making process regarding...
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