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In this paper, we propose a new technique for synchronization and channel estimation in M-QAM OFDM radio over fiber (RoF) system by using constant amplitude zero auto-correlation (CAZAC) sequence based training preamble. Delay and correlate method is used to identify the training sequence in the received signal vector and to correct the symbol timing offset. For an optimum demodulation of OFDM signal,...
As an overlay cognitive radio, transform domain communication system (TDCS) has been proposed to support reliable communications with low probability of interception. However, most of research on TDCS assume perfect synchronization to simplify algorithm design. In this paper, we present a low complexity symbol timing offset (STO) and carrier frequency offset (CFO) estimation method for practical TDCS...
The paper describes the mechanism of Agilent 3458A sampling time jitter present when external triggering is used at synchronous two channel sampling. Based on measurements it is shown that the master DMM adds approximately 3.2 ns of its own time jitter while triggering the slave DMM and that the effective time jitter for externally triggered DMM remains at 7 ns, well below ±50 ns maximum jitter as...
On the basis of the Markovian theory of an optimal nonlinear filtering in modified polygauss approximation a posteriori density of probability the task of synthesis and analysis of quasioptimal algorithm timing recovery with feedback on decision in coherent receiver of M-ary alphabets APK-signal is decided.
This paper proposes a novel symbol timing estimation technique for multiband orthogonal frequency division multiplexing (MB-OFDM) based ultra wideband system. The symbol timing is estimated in two steps namely, coarse synchronization and fine synchronization. The coarse synchronization is obtained using the correlation between adjacent symbols. A new algorithm is proposed using maximum likelihood...
In this paper, two fast and accurate FFT-based frequency offset estimation methods for OFDM systems are proposed. We analyze and simulate proposed methods in both Gaussian and multipath fading channels, and compare the results with those obtained using well known Schmidl's method. The simulation results are presented in terms of Error Variance (EV). Both proposed FFT-based methods have significantly...
In orthogonal frequency division multiple access (OFDMA) uplink system, estimations of time delay and carrier frequency offset (CFO) are both particularly challenging. In this paper, a coarse CFO and time delay estimation method is proposed for interleaved OFDMA uplink system. By exploiting the special scheme of interleaved OFDMA, the repetitive time-domain training symbol is designed, and the training...
This paper studies the frame synchronization of Orthogonal Frequency Division Multiple Access-Time Division Duplexing (OFDMA-TDD) systems and proposes a new method for downlink of IEEE 802.16 to improve frame synchronization performance. In this paper, we adapt three existing timing metrics for frame synchronization in OFDM mode of WiMAX. Among the methods considered, it is shown that direct application...
This paper presents a new joint frame synchronization and frequency offset estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems as a modification to Zhang's method (Zhang et al., 2005). By designing a new training preamble weighted by PN sequence, the timing estimator is improved (at least 3dB with low SNR). By estimating time offset first, the computational load is greatly...
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...
In SC-FDE (single carrier with frequency domain equalization) systems, timing offset brings ISI (inter-symbol interference). In order to obtain better timing precision in multi-path, a new timing offset estimation method applied to SC-FDE systems is proposed based on the analysis of Schmidl & Coxpsilas and Minnpsilas algorithms. By designing new training symbols and introducing corresponding calculation...
The synchronization problem is analyzed for low voltage power-line communication of orthogonal frequency division multiplexing (OFDM). It is analysed theoretically what affect synchronization problem such as frequency synchronization error and timing synchronization error. A new symbol timing and carrier frequency synchronization algorithm is presented and the algorithm divides the OFDM symbol into...
In this paper, we analyze the performance of a non-data aided near maximum likelihood (NDA-NML) estimator for symbol timing recovery in binary digital communications. The analysis of the estimator is performed for an additive noise only channel and the simulation results are extended to a flat fading channel. The probability distribution of the timing estimates is derived, presented and compared with...
In the cooperative spatial multiplexing MIMO-OFDM systems in multipath fading environments, the streams from different transmit antennas are not aligned in the time domain, and have different frequency offsets. The preambles and synchronization algorithms in the centralized MIMO-OFDM systems can no longer apply. A new preamble structure is proposed for this system, and the corresponding timing and...
We propose a three-stage cross correlation-based timing synchronization algorithm for multiband-OFDM UWB systems. By utilizing the time-domain base sequence of the packet/frame synchronization preamble, the proposed algorithm first performs a coarse estimation on the reference symbol boundary, followed by a fine estimation on locating the exact boundary of the FFT window for the symbol, and a final...
Synchronization at receiver, including mode detection, frame synchronization, sampling time recovery (STR) and carrier frequency synchronization four parts, is crucial for digital communication systems. Time domain synchronous (TDS) block transmission system, in which pseudo noise (PN) sequences are padded between two adjacent data blocks as guard intervals (GI), is widely used in wireless communication...
Orthogonal frequency division multiplexing (OFDM) systems are sensitive to time and frequency offset errors. In this paper, a method of joint timing and frequency synchronization for OFDM systems has been proposed based on preamble structure defined in IEEE 802.16 standard. The proposed method in coarse frame detection has good robustness and anti-noise ability. The coarse and fine frequency offset...
An Ultra-Wideband (UWB) channel exhibits frequency dependent delay characteristics in different bands of transmission. In [6] we studied and quantified the differences of delay parameters over frequency bands 3.1-4.6 GHz in several UWB channel models (CM). Based on this observation, we proposed an adaptive timing synchronization scheme (ATS) which estimates and maintains the timing delays of each...
We propose a new robust timing recovery algorithm with small symbol timing jitter for orthogonal frequency-division multiplexing (OFDM) systems. The concept of coarse FFT window selection and adaptive reference pilot generation are employed in this paper. This proposed scheme avoids inter-symbol interference (ISI) as well as delayed locked loop (DLL) tracking failure over frequency selective time-varying...
Mobile ad-hoc networks (MANET) are often characterized with rapidly changing topologies, presenting a constant challenge for time synchronization. This challenge holds especially true in tactical edge ground military networks, where topological instabilities are enhanced by hostile transmission environments. In the absence of GPS, time synchronization within the context of a tactical environment requires...
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