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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...
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...
As the communication systems have been increasingly complex, the problem of channel estimation for such complex communication systems has also emerged as an equally challenging task. To solve this problem, various schemes based on Least Mean Square (LMS) and its improved variants have been proposed. This paper presents an adaptive algorithm for channel estimation in non-Gaussian environment. The proposed...
Recent works have identified hybrid analog-digital processing as a cost-effective alternative to conventional full-digital processing in massive multiple-input multiple-output (MIMO) systems owing to the deployment of far less number of radio frequency (RF) chains. In this paper, we analyze the impact of oscillator phase noise on hybrid precoding in massive MIMO systems. Relying on the time division...
Channel estimation is an important component of wireless communications. This paper deals with the comparison between Mean Square Error (MSE) based neural networks and Minimum Error Entropy (MEE) based neural networks in additive non-Gaussian noise channel estimation. This essay analyzes MEE and MSE algorithms in several channel models utilizing neural networks. The aim of this study is first to compare...
In this paper, we propose a novel method to jointly estimate the activities and channel coefficients of devices in massive machine-type communications (mMTC) systems. We formulate a maximum a posteriori probability (MAP) estimation problem by exploiting the statistical prior information including the channel distribution and device activity probability. The formulated MAP problem is solved by a greedy...
In a binary input additive white Gaussian noise (BIAWGN) channel, belief propagation (BP) decoding for luby transform (LT) codes requires the knowledge of the signal-to-noise ratio (SNR) at the receiver to achieve its optimal performance. An erroneous estimation of the SNR at the decoder is referred to as “SNR mismatch”. SNR mismatch can significantly degrade the BP decoding performance of LT codes...
In this paper, a novel pilot extension scheme is proposed for massive MIMO uplink transmission, and its performance is evaluated analytically. Specifically, we divide the cell users into two groups, namely near users and far users, according to their distances to the service base stations. The far users are more motivated to mitigate the inter-cell interference than the near users at the price of...
In this paper, we propose two uplink pilot power control schemes to mitigate pilot contamination in a multi-cell massive multiple-input multiple-output (MIMO) system. These uplink pilot power control schemes can maximize the minimum signal-to-interference-plus-noise ratio (SINR) of the worst user or the mean SINR of the whole network for the downlink data transmission. Combinatorial optimization problems...
Multichannel receivers are usually employed in high-rate underwater acoustic communication to achieve spatial diversity. Passive time reversal combined with a single-channel adaptive decision feedback equalization (PTR-DFE) is a low-complexity solution to achieve both spatial and temporal focusing. Block-based PTR-DFE (BB-PTR-DFE) extends PTR-DFE to time-varying channels. Multichannel DFE (M-DFE)...
Multiuser Detection (MUD) and Channel Estimation techniques in Space-Division Multiple Access aided Orthogonal Frequency Division Multiplexing (SDMA-OFDM) systems recently received intensive interest in receiver design technologies. The maximum likelihood (ML) MUD that provides optimal performance has the cost of a dramatically increased computational complexity. The minimum mean-squared error (MMSE)...
In cognitive radio networks, cooperative spectrum sensing schemes improve the reliability of the detection by exploiting decisions made locally by several secondary users (SUs). Soft energy combining schemes provide optimal detection performance by combining the actual sensed information from the SUs, resulting in high cooperation overhead in terms of time, computational complexity, and bandwidth...
This study deals with the joint channel and carrier frequency offset (CFO) estimation in a Multiple Input Single Output (MISO) communications system. This problem arises in OFDM (Orthogonal Frequency Division Multiplexing) based multi-relay transmission protocols such that the geo-routing one proposed by A. Bader et al in 2012. Indeed, the outstanding performance of this multi-hop relaying scheme...
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...
We consider wireless information and power transfer in a multi-user massive multiple-input multiple-output (MU-Massive-MIMO) system, where several distributed antenna sets, also denoted as remote radio heads (RRHs), are deployed, while the users can simultaneously perform information detection and energy harvesting. Assuming a large number of antennas and autonomous power allocation for the information...
Multichannel blind deconvolution is a bilinear inverse problem that recovers an unknown signal observed as convolutions with multiple unknown filters. We are particularly interested in the case where the unknown filters are known to be short-length finite impulse response (FIR) filters a priori. Under this FIR prior, classical methods based on the commutativity of the convolution were proposed and...
In the channel blind estimation algorithm which exploits the first-order cyclostationarity in the received signal and performs circular deconvolution for Ultra Wide-Band (UWB) systems, there has a limitation that the duration of the channel must be less than the symbol duration. The problem can be effectively solved by using the channel shortening technique which compresses the length of the combined...
Data transfer in a broadband ionospheric radio channel is an actual problem currently. Ionospheric communication channel are characterized by non-stationarity, a hard interference situation, multipath propagation and dispersion distortion of signals. The frequency dispersion of the ionospheric channel is one of the most significant obstacles to the operation of decameter-band communication systems...
The problem of increasing the efficiency of data transmission through a HF radio channel in the case of using passive sounding was studied. The paper presents the main characteristics of the stochastic radio channel with scattering (delay spread, Doppler spread and the signal-to-noise ratio) and communication modem, which have an impact on the efficiency of a communication system. Algorithm for estimating...
A major challenge in realising a full-duplex (FD) transceiver is to decode the received signal in presence of the strong transmit signal termed as self-interference (SI). Usually SI is suppressed by reconstructing it using the transmit signal and subtracting it at the FD receiver. For good cancellation, an accurate estimate of the SI channel is essential. However, training for obtaining the SI channel...
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