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The problem of carrier frequency and phase synchronization exists in most wireless digital communication systems. These offsets are generally results from the Doppler effect, oscillator instabilities, and unknown transmission delays between receiver and transmitter. In this paper, we propose a joint synchronization algorithm applicable for short-burst PSK modulation systems. In the coarse estimation,...
In this paper, we propose a comparison method of training symbol (or preamble) and Cyclic Prefix (CP) to improved the frequency synchronization in orthogonal frequency division multiplexing (OFDM). The problems that arise in OFDM system is the time-shift and frequency mismatch between the oscillators in the transmitter and the receiver. It is known as a Carrier Frequency Offset (CFO) problem. By exploring...
A low rate of signal element transmissions in a communication system and a low SNR at the receiving side results in a normalized large frequency offset. To address this problem, the paper compares the performance from the aspect of the computational complexity, stability, noise immunity, and estimation accuracy. The performance is evaluated under different carrier frequency synchronization algorithms...
Aiming at pseudo random sequence, a precise synchronization method tolerating large capture error is proposed in this paper. It firstly formulates the correlation function of the pseudo random sequence in the range of one chip period around the capture position as two straight lines and parameters of which are acquired by employing least squares (LS) algorithm. Then, intersection point of the two...
Phase synchronization is a key problem which has to be carefully considered in the distributed radar systems. In this letter, the use of a continuous duplex phase synchronization method for the distributed frequency modulated continuous wave synthetic aperture radar system is investigated. The bistatic raw signal model containing the phase difference due to the spatially separated oscillators is introduced...
In order to improve the performance of the received system for the frequency selective channel at low SNR, spectrum combining technique before symbol timing synchronization for a randomly distributed sensor array is proposed. Moreover, to meliorate adverse effect on the demodulation performance caused by the single channel's nonlinear phase characteristic, a simple extensible average phase algorithm...
Orthogonal Frequency Division Multiplexing (OFDM) systems are very sensitive to symbol timing and frequency offsets. Therefore, it is very important to achieve a high precision time and frequency synchronization. With the absence of pilot symbols, blind synchronization algorithms using different metric functions or statistics of the received signal can be used. In this paper, a new blind symbol timing...
Determining the best frequency band for reconstructing display video leaking signal is the key problem in TEMPEST, which is the technology of electromagnetic leaking research. To solve such problem, a novel algorithm based on spectral centroid has been developed. Using the property that spectral centroid can accurately identify the signal energy center in frequency domain, the proposed algorithm can...
Cooperative technology could improve communication reliability by exploiting transmit diversity. However, the issue of imperfect frequency and timing synchronization makes it a challenge in practice. In this paper, we propose a novel cooperative communication scheme based on full space-time network code (FSTNC), which can maintain a stable network throughput and overcome the imperfect frequency and...
In this paper dynamic spectrum access has been considered as solution for spectrum inefficiency and spectrum scarcity problem. The synchronization of the signal, i.e. time and frequency recovery is proposed as one of the key parameters that are to be maintained and controlled adequately in order to achieve the best performance in cognitive radio networks. Given simulations provide the results that...
Based on the Digital Radio Mondiale(DRM) System specification, symbol timing and fractional frequency offset estimation for DRM receiving signal are achieved with the aid of cyclic prefix within the OFDM symbols. The redundancy of the signal is exploited without extra auxiliary data. The algorithm can work well with less bandwidth especially in capturing stage of symbol synchronization and tracking...
In this paper, an improved algorithm of coarse synchronization in the downlink of 3GPP LTE system is presented. This new algorithm can reduce the MSE (mean square error) of detected fractional carrier frequency offset (FCFO) by an order of magnitude and improve the accuracy rate of start point estimation by near 80 percent when SNR equals 0 in contrast with conventional coarse synchronization algorithms,...
Frequency offset estimation is an important issue in digital transceiver design, especially for coherent wireless transmission such as in WiMAX systems based on the IEEE 802.16e orthogonal frequency-division multiple access (OFDMA). The downlink synchronization, in WiMAX systems, involves synchronization of carrier frequency and timing as well as identification of the preamble index. This paper introduces...
Cooperative communications can be used to improve communication reliability. However, the transmissions from different relaying nodes result in a great challenge in practice. The use of TDMA for relaying transmissions causes large transmission delay. In contrast, FDMA and CDMA associate with the issue of imperfect frequency and timing synchronization due to the simultaneous transmissions from the...
We propose a frequency synchronization method for hybrid bi-static synthetic aperture radar (SAR), which denotes a SAR system with a spaceborne illuminator and an airborne receiver. Due to the high altitude difference, the method based on extracting the direct path signal is employed. The mathematical model to compute the frequency offset between the two sides' oscillators is given. Among the model,...
In this paper, we propose an efficient scheme using a new single-symbol preamble structure for OFDM data-aided synchronization. The preamble symbol is constituted of two successive equal-duration sub-symbols, the second one of which is a differentially encoded version of the first one, using an adequately designed precoding sequence. This structure leads to almost perfect channel autocorrelation profile...
Frequency synchronization plays a critical role in acquiring cooperative diversity for cooperative OFDM systems. However, the superposition of different carrier frequency offsets (CFOs) among each relay and destination makes the estimation difficult. In this paper, a novel multiple CFOs estimation algorithm is proposed. With this algorithm, the CFO corresponding to each relay can be accurately estimated...
We propose a new timing synchronization and frequency offset estimation algorithm using the characteristics of chirp training sequences based on Fractional Fourier Transform (FrFT). The training sequence is composed of one up and one down chirp signals. The received training sequence with timing and frequency offset is transformed by FrFT and the positions of the two peaks representing two chirps...
This paper outlines a hybrid OFDM synchronization technique for powerline communication. Initially, the timing and frequency offset are estimated by searching for the peak of an evaluated metric provided by a reference block transmitted at the beginning of each OFDM frame, and subsequently, autocorrelation properties induced at cyclic prefix on the time domain are exploited to maintain estimates of...
Fast acquisition is the major challenge for DS (direct sequence)/FH (frequency hopping) spread spectrum system. A DS/FH acquisition circuit which implements a digital noncoherent correlation scheme is studied extensively. The closed-form expressions of the mean acquisition time by single dwell decision and two-dwell decision are obtained with the state diagram respectively. The results show that,...
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