Integer Frequency Research Articles

Designing Passive Harmonic Filter on Dynamic Positioning Vessel's Electrical System Affected using Electrical Thruster

Ship with a dynamic positioning system has the ability to maintain her position dynamically. To be able to maintain the position, generally, ship with a dynamic positioning system have several thrusters located at bow or stern of the ship. Based on the propulsion system, there are 2 types of thruster which are mechanical thruster and electrical thruster. In electrical type, the thruster is driven by an electric motor supplied from the generator. In addition, on dynamic positioning vessel equipped with the electrical thruster, there are also VFD or Variable Frequency Drive to control the speed of motor thruster. The use of VFD components in the system may cause harmonic interference. Harmonic itself can be regarded as distortion in the sinusoidal waves due to the interference of other waves that have integer frequency multiples of their fundamental frequency due to the operation of non-linear thruster motor. Some of the most affected components of this distortion are the communications equipment and the components used for measurement. This research conducted an analysis of harmonic disturbance arising from the operation of 2 units bow thruster on DP Ship by simulating 6 scenarios of generator configuration using simulation software . The results from this research were total harmonic distortion value or VTHD of the system that complies with standards and rules, also the specification of a passive harmonic filter to reduce the VTHD value at the specific harmonic order.

Robust Blind Detection of Integer Carrier Frequency Offset for Terrestrial Broadcasting Systems Using Band Segmented Transmission

In the integrated services digital broadcasting-terrestrial (ISDB-T) system, the combination of digital terrestrial transmission and MPEG-4 advanced video coding (MPEG-4 AVC) has offered ways to provide a variety of digital high-definition television (HDTV) programs. Using band segmented transmission orthogonal frequency division multiplexing (BST-OFDM), the delivery of innovative video-on-demand and HDTV services is supported. To take full advantage of the attractive benefits of BST-OFDM, it is important to estimate integer frequency offset (IFO) without a priori knowledge on the segment type that is transmitted over transmission and the multiplexing configuration control (TMCC) signal. To address this issue, an efficient IFO detection method is proposed for the ISDB-T system employing BST-OFDM. To enable IFO detection independent of the segment type, information-bearing TMCC signals that are asymmetrically distributed in the frequency domain are used as pilot symbols. Numerical analysis is performed to present the relationship between error probability and design parameter. We show via the numerical results that the multiple transmitted TMCC information is efficiently used for blind estimation of the IFO, achieving robust estimation in the presence of the fractional frequency offset.

Modal interactions in the nonlinear dynamics of a beam–cable–beam

Quadratic and cubic modal interactions characterize the geometrically nonlinear dynamics of a parametric analytical model composed by two cantilever beams connected by a suspended shallow cable. The natural frequencies and modes of the linearized model are determined exactly, by solving the integral–differential eigenproblem governing the undamped free oscillations. Interesting phenomena of linear cable–beam interaction (frequency veering and modal hybridization) are recognized in the spectrum. Global and local modes are distinguished by virtue of the two localization factors measuring the modal kinetic energy stored in the beams and cable, respectively. The localization level is also put in relation to the magnitude of the quadratic and cubic nonlinearities. Therefore, the exact linear eigensolution is employed to formulate a nonlinearly coupled two-degrees-of-freedom model, defined in the reduced space of the modal amplitudes corresponding to a global and a local mode. The modal interactions between the two modes are analyzed, with focus on the autoparametric excitation mechanisms that can be favored by the occurrence of integer frequency ratios (1:2 and 2:1). Such internal resonance conditions enable significant transfers of mechanical energy—essentially governed by the quadratic coupling terms—from the small amplitudes of the externally excited global mode to the high amplitudes of the autoparametrically excited local mode. Different regimes of periodic and quasi-periodic oscillations are identified.

Beyond 5G With UAVs: Foundations of a 3D Wireless Cellular Network

In this paper, a novel concept of three-dimensional (3D) cellular networks, that integrate drone base stations (drone-BS) and cellular-connected drone users (drone-UEs), is introduced. For this new 3D cellular architecture, a novel framework for network planning for drone-BSs and latency-minimal cell association for drone-UEs is proposed. For network planning, a tractable method for drone-BSs’ deployment based on the notion of truncated octahedron shapes is proposed, which ensures full coverage for a given space with a minimum number of drone-BSs. In addition, to characterize frequency planning in such 3D wireless networks, an analytical expression for the feasible integer frequency reuse factors is derived. Subsequently, an optimal 3D cell association scheme is developed for which the drone-UEs’ latency, considering transmission, computation, and backhaul delays, is minimized. To this end, first, the spatial distribution of the drone-UEs is estimated using a kernel density estimation method, and the parameters of the estimator are obtained using a cross-validation method. Then, according to the spatial distribution of drone-UEs and the locations of drone-BSs, the latency-minimal 3D cell association for drone-UEs is derived by exploiting tools from an optimal transport theory. The simulation results show that the proposed approach reduces the latency of drone-UEs compared with the classical cell association approach that uses a signal-to-interference-plus-noise ratio (SINR) criterion. In particular, the proposed approach yields a reduction of up to 46% in the average latency compared with the SINR-based association. The results also show that the proposed latency-optimal cell association improves the spectral efficiency of a 3D wireless cellular network of drones.

Polydyne displacement interferometer using frequency-modulated light.

A radio-frequency Frequency-Modulated (FM) signal is used to diffract a He-Ne laser beam through an Acousto-Optic Modulator (AOM). Due to the modulation of the FM signal, the measured spectra of the diffracted beams comprise a series of phase-synchronized harmonics that have exact integer frequency separation. The first diffraction side-beam emerging from the AOM is selected by a slit to be used in a polydyne displacement interferometer in a Michelson interferometer topology. The displacement measurement is derived from the phase measurement of selected modulation harmonic pairs. Individual harmonic frequency amplitudes are measured using discrete Fourier transform applied to the signal from a single photodetector. Phase signals are derived from the changes in the amplitudes of different harmonic pairs (typically odd-even pairs) with the phase being extracted using a standard quadrature method. In this study, two different modulation frequencies of 5 and 10 kHz are used at different modulation depths. The measured displacements by different harmonic pairs are compared with a commercial heterodyne interferometer being used as a reference for these studies. Measurements obtained from five different harmonic pairs when the moving mirror of the interferometer is scanned over ranges up to 10 μm all show differences of less than 50 nm from the reference interferometer measurements. A drift test was also used to evaluate the differences between the polydyne interferometer and reference measurements that had different optical path lengths of approximately 25 mm and 50 mm, respectively. The drift test results indicate that about half of the differences can be attributed to temperature, pressure, and humidity variations. Other influences include Abbe and thermal expansion effects. Rough magnitude estimates using simple models for these two effects can account for remaining observed deviations.

Locking of electrostatically coupled thermo-optically driven MEMS limit cycle oscillators

A model of coupled limit cycle oscillators is developed and analyzed to discover and map out the system’s locking behavior. This sixth order model is motivated by the physical problem of a pair of closely spaced doubly clamped, thin silicon beams, coupled to each other through electrostatic fringing fields. The beams are assumed to be detuned with respect to each other. The beams are optically thin and are situated above a thick silicon substrate. When illuminated with continuous laser light a cavity interferometer is formed. Coupling of this optical interference with thermal stresses creates an inherent feedback loop that can drive the beams into limit cycle oscillation. Numerical analysis is used to study the range of coupling strengths and detunings over which 1:1, and other integer frequency ratio locking can be obtained. Results show that 1:1 locking can occur over a broad range of detuning even at relatively low levels of coupling. For coupling strengths just above the threshold for locking, both locked and drift states can exist, depending on the initial conditions. Locking at 2:1, 3:1, 3:2 and 5:2 frequency ratios are observed for detunings that are close but not exactly equal to these integer ratios.

Timing and Integer Frequency Offset Estimation for DLMT System over Time-Varying Rayleigh Fading Channel

In this paper, we study the timing and integer carrier frequency offset (ICFO) estimation problem for dynamic lattice multicarrier transmission (DLMT) system over time-varying Rayleigh fading channel. Firstly, a novel preamble structure based on two constant amplitude zero auto-correlation (CAZAC) sequences is designed for DLMT system. Then, by using the designed dual-CAZAC preamble, a discrete cross ambiguity function (DCAF) based timing and ICFO estimation algorithm is proposed. Simulation results show that the proposed DCAF based timing and ICFO estimation algorithm can mitigate the impact of time-varying multipath Rayleigh fading channel and outperforms traditional estimators on the correct estimation probability performance.

Experimental demonstration of a 16.9 Gb/s link for coherent OFDM PON robust to frequency offset and timing error

Due to its merits of flexible bandwidth allocation and robustness towards fiber transmission impairments, coherent optical orthogonal frequency division multiplexing (CO-OFDM) technology draws a lot of attention for passive optical networks (PON). However, a CO-OFDM system is vulnerable to frequency offsets between modulated optical signals and optical local oscillators (OLO). This is particularly serious for low cost PONs where low cost lasers are used. Thus, it is of great interest to develop efficient algorithms for frequency synchronization in CO-OFDM systems. Usually frequency synchronization proposed in CO-OFDM systems are done by detecting the phase shift in time domain. In such a way, there is a trade-off between estimation accuracy and range. Considering that the integer frequency offset (IFO) contributes to the major frequency offset, a more efficient method to estimate IFO is of demand. By detecting IFO induced circular channel rotation (CCR), the frequency offset can be directly estimated after fast Fourier transforming (FFT). In this paper, circular acquisition offset frequency and timing synchronization (CAO-FTS) scheme is proposed. A specially-designed frequency domain pseudo noise (PN) sequence is used for CCR detection and timing synchronization. Full-range frequency offset compensation and non-plateau timing synchronization are experimentally demonstrated in presence of fiber dispersion. Based on CAO-FTS, 16.9 Gb/s CO-OFDM signal is successfully delivered over a span of 80-km single mode fiber.

A novel joint timing/frequency synchronization scheme based on Radon–Wigner transform of LFM signals in CO-OFDM systems

A joint timing and frequency synchronization method has been proposed for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) system in this paper. The timing offset (TO), integer frequency offset (FO) and the fractional FO can be realized by only one training symbol, which consists of two linear frequency modulation (LFM) signals with opposite chirp rates. By detecting the peak of LFM signals after Radon–Wigner transform (RWT), the TO and the integer FO can be estimated at the same time, moreover, the fractional FO can be acquired correspondingly through the self-correlation characteristic of the same training symbol. Simulation results show that the proposed method can give a more accurate TO estimation than the existing methods, especially at poor OSNR conditions; for the FO estimation, both the fractional and the integer FO can be estimated through the proposed training symbol with no extra overhead, a more accurate estimation and a large FO estimation range of [−5 GHz, 5GHz] can be acquired.

A complete cell search and synchronization in LTE

The initial process of identifying any available base station (BS) by a user equipment (UE) that wants to communicate is termed as cell search. To ensure a reliable communication, any UE has to be synchronized with the BS both in time and frequency domains. Cell search process is said to be complete once cell ID associated with long-term evolution (LTE) BS is decoded successfully. This paper presents a series of cell search and synchronization algorithms, which efficiently estimated time and frequency offsets as well as cell ID. The synchronization signals present in LTE, namely, primary synchronization signal (PSS) and secondary synchronization signal, that carry cell ID are critically exploited in the algorithms. The aforementioned algorithms are classified into two modules, namely, module I and module II, based on their computation complexity.In module I, a cyclic prefix (CP)-based maximum likelihood (ML) estimator is employed to obtain a coarse estimate of time and fractional frequency offset; however, the estimates are refined using synchronization signals. A joint estimation of timing, integer frequency offset (IFO), and PSS ID (sector ID) is carried out in module II. Both the modules operate on the cross-correlation approach of PSS with the received signal for obtaining timing and sector ID. IFO as a part of module II is detected from a finite hypotheses set using synchronization signals. Extensive simulations are carried out on a time-varying frequency-selective channel to analyze the performance of the algorithms.

A Study on an Integer Frequency Offset Estimation and Compensation for DOCSIS 3.1 Downstream

In this paper, we propose an integer frequency offset estimation and compensation method based on PLC preamble correlation in DOCSIS 3.1 Downstream system. The proposed method determines the PLC preamble subcarrier location recovered from PLC data and the one obtained from PLC preamble correlation. We showed the performance of PLC preamble detection in the received signal through the maximum value detection of PLC preamble correlation. Thus we can estimate and compensate for the integer frequency offset by computing the difference of PLC subcarrier locations.

Nonlinear dynamics of a parametric analytical model for beam-cable-beam structures

A parametric model is proposed to analytically describe the nonlinear dynamics of the structural system composed by two vertical cantilever beams connected by a suspended sagged cable. Focus is made on the geometric nonlinearities that characterize the boundary interactions between the linear beams and the nonlinear Irvine cable. The closed form solution of the linear eigenproblem governing the undamped small-amplitude vibrations enables – first – the clear distinction between global modes, dominated by the beam dynamics, and local modes, dominated by the cable vibrations, and – second – the parametric assessment of some parameter combinations corresponding to integer frequency ratios (1:1, 2:1) between global and local modes. Such internal resonances open the way to different phenomena of linear and nonlinear interactions, which can sustain the transfer of mechanical energy between the interacting modes and, consequently, the onset of high amplitude local oscillations. After the reduction to a single mode basis, the qualitative and quantitative relevance of the system nonlinearities is analyzed. In particular, the effects of the global, local, hybrid nature of the modal shapes on the softening/hardening behavior of the frequency response are investigated.

The US real GNP is trend-stationary after all

ABSTRACTThis article applies the Fractional Frequency Flexible Fourier Form (FFFFF) Dickey–Fuller (DF)-type unit root test on the natural logarithm of US real GNP over the quarterly period of 1875:1–2015:2, to determine whether the same is trend- or difference-stationary. While standard and Integer Frequency Flexible Fourier Form DF-type test fails to reject the null of unit root, the relatively more powerful FFFFF DF-type test provides strong evidence of the real GNP as being trend-stationary, i.e. US output returns to a deterministic log-nonlinear trend in the long run.

Synchronization Algorithm for STBC MIMO-OFDM System at Low SNR

The accurate timing and frequency synchronization is hard to obtain for space---time block codes (STBC) multiple input multiple output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems at low signal-to-noise ratio (SNR). In this paper, a new synchronization algorithm for STBC MIMO-OFDM system at low SNR is proposed. Firstly, a set of imaginary orthogonal complementary sequences with a set of imaginary complementary sequence sets and orthogonal matrix is constructed, and the proper length of the imaginary orthogonal complementary sequences is obtained by extending the sequences through transforming orthogonal matrix. Secondly, in order to improve the sequences' auto-correlation and cross-correlation, the training sequences are constructed with their minus conjugates, and then superimposed on data signals. Finally, good synchronization is obtained by cross-correlation operation between the training sequences and data signals at the receiver. The integer frequency offset is estimated to be $$\varepsilon \in [ - N/4,N/4]$$źź[-N/4,N/4]. Theoretical analysis and simulation prove that this synchronization algorithm achieves precise timing synchronization, wider frequency offset range and lower computational complexity at low SNR than conventional algorithm.

Efficient Integer Frequency Offset Estimation Architecture for Enhanced OFDM Synchronization

In orthogonal frequency-division multiplexing (OFDM) systems, integer frequency offset (IFO) causes a circular shift of the subcarrier indices in the frequency domain. The IFO can be mitigated through strict RF front-end design, which tends to be expensive, or by strictly limiting mobility and channel agility, which constrains operating scenarios. The IFO is, therefore, often estimated and removed at baseband, allowing implementations to benefit from the relaxed RF front-end specifications and to be tolerant to both Doppler shift and multistandard channel selection. This paper proposes a novel architecture for the IFO estimation which achieves reduced power consumption and lower computational cost than contemporary methods, while achieving excellent estimation performance, close to theoretically achievable bounds. A pilot subsampling technique enables fourfold resource sharing to reduce the computational cost, while multiplierless computation yields further power reduction. Performance exceeds that of the conventional techniques, while being much more efficient. When implemented on field-programmable gate array for IEEE 802.16-2009, the dynamic power reductions of 78% are achieved. The architecture and method is applicable to other OFDM standards including IEEE 802.11 and IEEE 802.22.

A Robust Maximum Likelihood Scheme for PSS Detection and Integer Frequency Offset Recovery in LTE Systems

Before establishing a communication link in a cellular network, the user terminal must activate a synchronization procedure called initial cell search in order to acquire specific information about the serving base station. To accomplish this task, the primary synchronization signal (PSS) and secondary synchronization signal (SSS) are periodically transmitted in the downlink of a Long Term Evolution (LTE) network. Since SSS detection can be performed only after successful identification of the primary signal, in this work we present a robust scheme for joint PSS detection, sector index identification and integer frequency offset (IFO) recovery in an LTE system. The proposed algorithm relies on the maximum likelihood (ML) estimation criterion and exploits a suitable reduced-rank representation of the channel frequency response to take multipath distortions into account. We show that some PSS detection methods that were originally introduced through heuristic reasoning can be derived from our ML framework by selecting an appropriate model for the channel gains over the PSS subcarriers. Numerical simulations indicate that the proposed scheme can be effectively applied in the presence of severe multipath propagation, where existing alternatives provide unsatisfactory performance.

Fractional Frequency Flexible Fourier Form to approximate smooth breaks in unit root testing

In this study, a Fractional Frequency Flexible Fourier Form DF-type unit root test is proposed. The small sample properties of the proposed test are found to be better than that of the integer frequency counterpart.

Enhanced Timing Advanced Estimation With Symmetric Zadoff-Chu Sequences for Satellite Systems

Timing advanced estimation with Zadoff-Chu sequences is sensitive to the frequency offset, especially for satellite systems with large Doppler shift and oscillator uncertainties. In this letter, Timing Advanced Estimation with Symmetric Zadoff-Chu sequences (TAE-SZC) is proposed to deal with the integer and fractional frequency offset, respectively. By adopting TAE-SZC, the effect of integer frequency offset can be resolved by the symmetric properties of Zadoff-Chu sequences, and an iterative compensation method is used to mitigate the effect of fractional frequency offset. Simulation results show that TAE-SZC outperforms the conventional timing advanced estimation methods without incurring additional consumption of time/frequency resource.

A New Timing and Frequency Synchronization Algorithm for Distributed MIMO-OFDM Systems

To solve the problems of time delay and different frequency offset between different transmit antennas and the same receive antennas for distributed multiple input multiple output orthogonal frequency division multiplexing systems. In this paper, a new timing and frequency synchronization algorithm is proposed. The search range of the fine timing synchronization is set with coarse time synchronization position and cyclic prefix, and the precise timing synchronization is obtained by utilizing the correlation between data information and training sequence. In the integer frequency offset estimation algorithm, the real component of the training sequence is taken as the real sequence, and then the differential relationship between the first and last samples is estimated accordingly. Theoretical analysis and simulation show that: (1) under multipath fading channel, the timing offset and frequency offset between different transmit and receive antennas can be effectively estimated with the synchronization algorithm proposed in this paper; (2) with signal noise ratio $$-$$-5Â dB, the probability of the correct synchronization is 95Â % and the precision of the frequency offset estimation can be as high as $$10^{-2}$$10-2, which is over the similar synchronization algorithm.

A Low-Complexity Integer Frequency Offset Estimation Scheme Using Combined Training Symbols for OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, an integer part of a frequency offset (IFO) that causesambiguity in data demodulation is estimated generally by comparing correlations between the received and local signalsfor IFO candidates. In this paper, we propose an IFO estimation scheme that provides a tradeoff between the estimationperformance and the computational complexity including a conventional scheme as a special case. In the proposedscheme, template signals are formed by combining frequency-shifted training symbols, allowing the receiver to reducethe number of IFO candidates in the estimation process. Numerical results illustrate the tradeoff of the proposed scheme:The proposed scheme exhibits a tradeoff between the correct estimation probability and the computational complexitytaking the number of the training symbols used to construct the template signal as a parameter.