The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, the authors address the problem of true Cramer-Rao lower bound (CRLB) derivation for a non-data-aided (NDA) vector parameter estimation over non-constant gain flat Rayleigh fading channel (FRFC). General CRLB expressions for carrier frequency offset, carrier phase, symbol timing and signal to noise ratio (SNR) estimation are analytically developed going through the computation of the...
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...
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...
In order to increase the accuracy of timing estimation in frequency selective fading (FSF) channels and reduce the computational complexity, in this paper an adaptive symbol synchronization of OFDM blind channel estimation is proposed. First, by the ML algorithm used in flat fading channels, we give a rough estimated time position dML, then choose Δd, and give the maximum d1 of the measure function...
The capacity of a time hopping (TH) ultra-wide bandwidth (UWB) system with synchronization errors is analyzed for both additive white Gaussian noise and multipath fading channels. The analysis takes into account the inter-path interference, the inter-chip interference and the inter-symbol interference, in addition to the multiple access interference. The effects of pulse shape, number of users and...
In this paper, a new blind symbol synchronization algorithm is presented for orthogonal frequency-division multiplexing (OFDM) systems. The proposed algorithm extracts the timing which is not disturbed by delay spread within the guard interval by utilizing the cyclic prefix. A new timing function is introduced. By detecting the down-turn transition timing of the function, the symbol synchronization...
Time offset estimation is one of the main tasks of the initial ranging process in orthogonal frequency-division multiple access (OFDMA)-based network. Recently, the multiuser time offset estimation based on phase shift over adjacent subcarriers has been presented. This method can reduce the huge computation complexity of the timing recovery based on peak correlation searching of long PN codes. The...
The wireless network scenario here is based on N users that communicate one with the others through a central relay node by adopting the Analog Network Coding (ANC) paradigm. In this paper, we propose a communication scheme for ANC able to guaratee the simultaneous transmissions of N ?? 2 interfering terminals using the concept of multiuser processing (i.e., channel estimation and detection). Under...
In this paper, we propose a coarse and fine frequency synchronization method which is suitable for the 3rd Generation Partnership Project (3GPP) long term evolution (LTE) orthogonal frequency division multiple access (OFDMA) system in time division duplexing (TDD) mode. In general, primary synchronization signal (PSS) correlation based estimation method and cyclic prefix (CP) correlation based tracking...
A fine time tracking system is presented for orthogonal frequency division multiplexing (OFDM) systems working in multipath fading channels. Due to the channel variability, coarse timing is the most common sampling synchronization level performed in these environments. However, in case of slow time variant channels, fine time tracking can help in some way to the channel equalization, improving the...
This work analyzes combined effects of major synchronization errors, including the symbol time offset (STO), carrier frequency offset (CFO) and sampling clock frequency offset (SCFO) of orthogonal frequency-division multiplexing (OFDM) systems. Such errors degrade the performance of an OFDM receiver by introducing inter-carrier interference (ICI) and inter-symbol interference (ISI) into the systems...
In timing synchronization, the Cramer Rao Bound has been used as performance bounds for timing estimation in AWGN channel. However, the instantaneous CRB for timing estimation in fading channels depends on the channel realizations and may fail to bound the mean square error (MSE) of the estimator because the equivalent signal-to-noise ratio (SNR) is too low. In this paper, we demonstrate that the...
We present two new noise variance estimation methods for OFDMA signals transmitted through an unknown multipath fading channel. We focus on blind estimation as it does not require any pilot sequences and is therefore applicable to contexts, such as cognitive radio for instance, where little prior signal knowledge is available. The two estimators are respectively based on the time-frequency sparsity...
In the space-time cooperative relay orthogonal frequency division multiplexing (OFDM) system, a challenge is the lack of perfect timing synchronization, which degrades the performance of the receiver greatly. This paper investigates a timing synchronization scheme to solve this problem. Unlike the conventional algorithms, our attempt primarily aims to obtain the different time delays of source and...
This paper presents a new method to use correlator in modern communications after analysing the application and performance of the traditional correlator in detail. According to the results of simulation, the new method have more precise frequency and timing synchronization in wireless communications, which improves its ability against interference of multipath and frequency selective fading. Even...
This work presents a blind synchronizer for orthogonal frequency-division multiplexing (OFDM) systems based on signal-to-interference-and-noise-ratio (SINR) maximization. Due to the incurred losses from inter-symbol interference (ISI) and inter-carrier interference (ICI) introduced by synchronization errors, the SINR of the received data drops drastically. By taking advantage of this characteristic,...
A frequency offset estimation algorithm for DTMB system based on signalpsilas second-order cyclostationary is developed. A unified structure of the method is given for diverse modes in DTMB system. Simulations show that this approach has good performance for both single-carrier and multi-carrier modes in AWGN and dynamic Rayleigh fading channel.
In this paper, we propose a new frequency synchronization algorithm for orthogonal frequency division multiplexing (OFDM) system by combining PN sequences with cyclic prefix. It is the improvement of Tufvesson's algorithm. In the new algorithm, the frequency offset is estimation with two steps. First a small step (span of the correlation) is used to estimate frequency offset which will result in a...
A novel timing offset estimator for orthogonal frequency division multiplexing (OFDM) systems is proposed. The estimator is a modification to Schmidl method by a kind of new preamble. The performance of the estimator is presented in terms of mean and variance by simulation in multipath fading channel. The results show that the proposed estimator has smaller variance than Schmidl and Minn's estimators,...
In this paper, a joint carrier synchronization and equalization algorithm is proposed for OFDM systems in the tracking stage. Significantly, the carrier synchronization scheme is a dual-loop, which is composed of an outer and an inner loops, with the multirate processing to eliminate the carrier frequency offset and the channel phase variation. In addition, the gain equalization loop is employed to...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.