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In this paper, a joint synchronization and Doppler scaling factor estimation algorithm has been proposed for underwater acoustic communications. The training sequence, which consists of two Zadoff-Chu (ZC) sequences being conjugate with each other, is utilized to synchronize and estimate Doppler scaling factor, time delay and carrier frequency offsets (CFOs). ZC sequences are well designed to show...
Time Difference Of Arrival (TDOA) method is very often used inside electronic intelligence systems. TDOA method requires the high signal to noise ratio at the output of the intermediate frequency amplifier for target localization, usually around 12 dB or more. At low signal-to-noise ratio TDOA is inaccurate and especially in case of the active jamming it is nearly impossible. The multilateral TDOA...
Polar coding is a low-complexity method for communication over noisy classical channels, which is capable of providing highly reliable data transmission. This paper proposes an enhanced polar codec scheme for mission critical applications in train-to-ground wireless communications. Firstly, we develop an enhanced polar coding scheme to support reliable data transmission under time-varying channel...
In this paper, we propose a novel pseudo-random beamforming (BF) technique in multi-cell downlink networks consisting of multiple base stations (BSs) and one BS coordinator. In the proposed technique, each BS first generates M BF matrices with a pseudo-random manner and each mobile station (MS) opportunistically feeds back the received signal-to-interference-and-noise (SINR) ratio for each random...
In this paper, the characteristics of two different uniformly spaced circular arrays are analyzed, including the beam width, the sidelobe peak level, the resolution and the Cramer-Rao bound(CRB) of the array. Firstly, according to the structure of the dual circular array, the formula of array pattern, the formula of resolution and the formula of CRB are deduced. Secondly, the effects of the elements...
In this paper, we propose an algebraic approach to design extremely low rate low-density parity-check (LDPC) codes by employing the primitive polynomials. We first investigate the requirements for the polynomials to construct 4-cycle free LDPC codes and then propose an algebraic approach to design the parity check matrix. To achieve a better decoding performance in the extremely low rate region, we...
The paper proposes a customized frequency domain energy detection spectrum sensing scheme. It is needed to fulfill requirements provided by the IEEE 802.22 standard, aimed at extending Internet services to Television White Space frequencies. It provides a detection scheme allowing to achieve strict sensitivity required by the protocol either in sensing time or in detection capabilities. In particular,...
Plane wave methods for ultrafast ultrasound imaging suffer from a low signal to noise ratio (SNR) and a limited field of view at greater imaging depths. Imaging using multiple focused coded beams in parallel is one strategy for high speed imaging that may improve on these limitations. However, the SNR and resolution of this strategy are degraded by the interference between the beams transmitted in...
We have previously reported increases in diagnostic shearwave and harmonic SNR using pressures that exceed the US FDA guideline for the Mechanical Index (MI). The MI is calculated using peak rarefaction pressure (PRP) measured in water with linear derating to account for tissue attenuation. However, acoustic propagation through water is a highly nonlinear process that inherently differs in attenuation,...
The growth in the number of places in Brazilian higher education was of great benefit to the country, bypassing the elitist model that marked the beginning of academic activities in Brazi. However, the social and economic impact can be minimized by the occurrence of the evasion phenomenon. We highlight the investments in science, technology and innovation that has higher education as its great ally,...
Sensing the presence of people in indoor spaces allows smart systems to be aware of and responsive to the occupants, and paves the way for a wide range of applications. In this paper, we show how the reflection patterns of ultrasonic signals can be leveraged to detect the presence of still persons. We propose the use of supervised learning over segmented reflection patterns, and prove that this method...
Exponentially increasing demands for higher data rates and quality of service cannot be satisfied by delivering more power as higher power levels may reduce Signal-to-Interference-plus-Noise Ratio (SINR) with negative impact on overall system performances. Simultaneously, the continuous shrinking in transistors size for denser circuits integration, following Moore's law, will be constrained by the...
In the present paper, the effects of signal-to-noise ratios (SNRs) on the measurement of 19 atomic Lick indices are analyzed. The stellar spectra of the large sky area multi-object fiber spectroscopic telescope (LAMOST) are selected under different conditions, which allows investigating the impact of SNRs on the accuracy and precision of the measurement of Lick/LAMOST indices. The experiment result...
In this paper, the haze attenuation of laser affects the performance of free space optical communication (FSOC). The Haze is regarded as coated particles, which considers haze as the inner and droplet aerosol as the outer core. Based on the coated scattering theory of Christian Mätzler, the scattering model of haze aerosols is established. According to the Meteorological Bureau, the fitting relationship...
Subcarrier index modulation (SIM) is an interesting transmission technique that has been considered to improve the spectral efficiency and/or the error performance of orthogonal frequency-division multiplexing (OFDM) systems. The subcarriers are split into groups, and within each group part of the information is carried by an index associated with a selection of active subcarriers. Other techniques...
The impact of the electrical phase modulation index 2πh in the performance of coherent detection optical OFDM systems based on electrical constant-envelope signals is analytically and numerically evaluated in this paper. A compromise between 2πh and system performance, that considers the effect of nonlinearities inserted by Mach-Zehnder optical modulators, is established. Moreover, it is shown that...
The well-being of the environment is one of the major factors that contributes to sustainability. Sustainable human settlements require local governance to plan, implement, develop, and manage human settlements expansions. This is important as the number anthropogenic activities is directly correlated to the increase in human population within a geographical region. Regional mapping of land cover...
Hyperspectral unmixing aims to estimate a set of endmembers and their corresponding percentages in pixels. NMF and its extensions with various constraints have been widely applied to hyperspectral unmixing. L1/2 regularizer and L2 regularizer can be added into NMF to enforce sparseness and smoothness respectively. In practice, an rigion in hyperspectral image may possesses different sparse level across...
Geosynchronous SAR (GEO SAR) has better coverage and revisiting performance than the low Earth orbit SAR. Thus GEO SAR can implement the repeat-pass interferometry as its revisit time of 1 day and the orbit drift (forming baseline) induced by perturbation. In comparison, the twin GEO SAR formation configuration in which the slave satellite repeats the master satellite' track can realize shorter revisit...
We propose a diffusion expectation-maximization algorithm with adaptive combiner for distributed estimation over sensor networks. Due to the spatial distribution of the nodes, variation of node profile across the network is a common phenomena in real applications. The unreliable nodes exist and provide inaccurate estimates, which may be caused by high levels of noise or malicious attacks. Instead...
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