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In this paper, as binary modulation schemes, the differential on-off keying (DOOK) system, which can achieve anti-background noise capability and high data transmission efficiency, is considered. In order to solve the synchronization slip, a visible-light framed DOOK system embedding {-1,+1}-synchronization signal pattern is proposed. Moreover, theoretical formulas of detection and false alarm probability...
This paper shows that preamble detectors, based on the mathematical and statistical properties of M-ary symbols in ISI-free environments, can provide reasonably good performance when operating on SOQPSK-TG samples in the presence of unknown ISI and a frequency offset. Of the preamble detectors examined in this paper, the preamble detector based on the concept of non-coherent post-detection integration...
With the introduction of multicore systems and parallel programs concurrency bugs have become more common. A notorious class of these bugs are data races that violate correlations between variables. This happens, for example, when the programmer does not update correlated variables atomically, which is needed to maintain their semantic relationship. The detection of such races is challenging because...
The purpose of this paper is to provide a method of verification for digital watermarks, based on removing the watermark with the help of another low quality audio track, lacking the watermark. We present results of a study on modern watermarking systems implemented in industry. The attack is based on the fact that we have little prior knowledge about the algorithm used on a certain watermarking scheme,...
Synchronization is one of the key technologies in frequency-hopping (FH) communication systems. Among four FH synchronization methods, synchronization-word (SW) is the most widely used but is still likely to be interfered. By combining SW with time of day (TOD), anti-reconnaissance capability is improved, but it takes relatively much more time to synchronize and cannot be used in Fast Frequency Hopping...
In order that an User Equipment (UE) can access a cell in a Long Term Evolution (LTE) systems, it must be able to perform an initial synchronization and search for a base station (eNodeB) to establish the downlink (DL) access. This process is called the initial cell search. Two synchronization signals are available to accomplish this process: the primary synchronization signal (PSS) and the secondary...
In direct sequence (DS) spread spectrum communication system, the first condition of receiving correct data is chip synchronization. Delay-locked loop (DLL) is an important part of implementing chip synchronization in digital receiver. This paper explores fundamental of digital DLL, presents basic structure of it. Much attention has been paid for algorithm of phase detector and working principle of...
This paper proposes a novel approach for frame synchronization which applies Maximum Likelihood Ratio Testing (MLRT) coupled to Post Detection Integration (PDI) scheme. This approach is robust to frequency and phase offsets, meanwhile it considers base band signal over sampling without matched filtering and perfect timing. Derivation and realization diagram of this approach is presented. Numerical...
This work proposes an effective code acquisition technique for Galileo BOC signals, exploiting a fast parabolic interpolator running on three estimated ambiguity samples in the neighbourhood of the coarse estimate. Performance analysis is carried out in comparison with the conventional approach, based on the power detector test. The numerical results, obtained from wide simulation trials under operating...
The optimal detector for CP (Cyclic Prefix)-OFDM (Orthogonal Frequency Division Multiplexing) signal with inherent periodic pilots in low signal to noise ratio environments relies on perfect time synchronization. In this paper, we modify the optimal detector and propose a new suboptimal sensing scheme based on pilots estimation (SSS-BPE). In the proposed SSS-BPE, the likelihood criterion and periodicity...
Self-encoded spread spectrum systems derive spreading codes from the data stream and have been shown to achieve a 3 dB power gain while providing time diversity for robust performance in wireless fading channels. Since the receiver does not knowledge of the initial spreading code, these systems present a unique challenge to code synchronization. In this paper, we present a method to achieve code acquisition...
This article proposes a new method of maintaining synchronization of carrier for the correlation receiver. We use PSK of fifth phase for this telecommunication system. However, we can apply this method for the correlation receiver of any other demodulation. As usual method for the synchronization, there is DLL (Delay Lock Loop). However we thought that we can directly find the value of phase difference,...
In this paper, the acquisition performances of different detectors are investigated and evaluated for frame acquisition in DVB-S2 system. Mean acquisition time in both single-dwell and multi-dwell procedures are derived based on a Markov chain model. Since it is quite complicated to analyze some parameters in close formula, a semi-analytical method is adopted to simplify the analysis. Performance...
Code synchronization is a critical step for fast and reliable code search in direct-sequence spread-spectrum (DS-SS) system. In this paper, we propose a novel differentially coherent (DC) detection scheme for rapid code acquisition over a fast Rayleigh fading mobile radio channel with frequency offset, and compare the performance with the conventional I-Q noncoherent detection scheme. Numerical results...
This contribution proposes an effective procedure for the acquisition of pseudo-noise code in satellite spread-spectrum localization systems. The main contribution of our work is twofold: first, we define a new objective function that is able to exploit the capabilities of different detectors in only one ambiguity function. Then, we introduce a compound detection procedure that, taking advantage of...
This paper analyzes the possibility to perform joint frame synchronization and code acquisition for the DVB-RCS mobile system. Since the standard foresees the adoption of Direct Sequence Spread Spectrum techniques, novel detectors able to cope with the scenario at hand are proposed. Comparison in terms of Mean Acquisition Time and complexity are carried out, and the best solution in terms of performance...
Satellite-based localization has attracted ever growing attention in the last few years. In this work, we present a signal processing technique for initial code acquisition and synchronization of satellite signals, such as the one used by position location techniques. Conventional approaches are based on the interpolation, usually carried out by (time-consuming) narrow-band over-sampling or (fast)...
Spectrum sensing is a central part in a cognitive radio and therefore a thorough design of a spectrum sensor is of highest priority. Here, a novel implementation of a spectrum sensing technique, using a generalized version of the Neyman Pearson test, is considered. This novel implementation overcomes the usual prerequisite of the known noise power. This benefit is achieved by normalizing the signal...
This paper presents a novel synchronization scheme that base on Baker Codes autocorrelation property for UWB impulse radio system. Simple threshold detection circuit is used to perform early quantization. An asynchronous pulse capture block is introduced to perform a direct down conversion of the UWB pulses from RF band to baseband. The new scheme provides run time synchronization tracking and resynchronization...
A hybrid PN-code acquisition scheme is proposed and studied for direct sequence code division multiple access communications in frequency-selective Rayleigh fading channels. The most important feature of the proposed system is its ability to dynamically estimate the number of multipath signals that may lie in the reference channel. The basic idea of the considered algorithm is to sort the partial...
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