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We present a time-lens based all-optical 10 Gb/s frame synchronizer and retimer. Our scheme can work with a 4096-bit frame, with frequency offset up to 1MHz, which is demonstrated by experimental results.
In the lately released Chinese mobile multimedia broadcasting standard CMMB, cyclic-prefix based OFDM technique has been adopted. Traditional timing synchronization for this system requires a correlator to correlate the last Ng samples of the received OFDM symbol with their copies ahead, and at least N (the length of OFDM symbol) data and Ng correlation results have to be stored for implementation,...
Some recently proposed robust methods for time domain timing and frequency synchronization in OFDM systems incorporate the use of cross-correlation based threshold detection in their timing adjustment and joint time-frequency algorithms. In this paper, we analyze the threshold criterion used and derive its theoretical performance. This translates into a better characterization of these OFDM synchronization...
This paper analyzes the synchronization problem of OFDM in FH communication system, studies timing synchronization and frequency synchronization using pilots according to the characterization of OFDM and FH. This algorithm determines the time position and frequency offset using the correlation of the pilots. The research result indicates that this algorithm is available in the FH system.
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 this paper we investigate the time and frequency synchronization as well as the sector and cell search for the 3GPP long term evolution (LTE) downlink. The proposed algorithms rely on the synchronization and cell-specific reference signals and are hence compliant to most recent 3GPP specifications. Time and (fractional) frequency offset coarse synchronization are performed in the time domain with...
Fast verification of the prototype design on software radio platform has become one of the most important research topics in communication systems. Based on OFDM receiver which is implemented on FPGA, the paper focuses on many key issues in the implementation of the strategy in software wireless platform such as OFDM frame synchronization, frequency compensation, symbol timing, etc. The proposed corresponding...
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...
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 ambient information society, a variety of networks consisting of sensory and computational devices are embedded in the environment and individuals. They are autonomously connected, merged, and divided depending on the context and provide a network service appropriate for time, place, occasion, and individuals. In this paper, we investigate how such dynamic network formation is performed focusing...
Worldwide interoperability for microwave access (WiMAX) is standardized in the IEEE 802.16e-2005/802.16d-2004, the physical layer of WiMAX is based on orthogonal frequency division multiplexing (OFDM) modulation which is particularly sensitive to the timing synchronization. This paper gives a new method based on the idea of cross-correlation and difference which can confront frequency-offset when...
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...
The time synchronization is one of the main issues in frequency hopping mobile ad hoc networks (FH MANET) or time synchronous wireless sensor networks (TWSN). In the former case a network wide time reference is needed in FH code phase synchronization and in the latter case, e.g., in time stamping of the sensed phenomenon. Herein, a distributed decision making method (s) that solves the problems considering...
The physical layer of IEEE802.16e is based on orthogonal frequency division multiplexing (OFDM) modulation which is particularly sensitive to the timing synchronization. This paper gives a new method based on the idea of difference. The new method can confront frequency-offset when it is in the moment of the symbol timing synchronization and reduce the computation complexity. In the new method, the...
A new training symbol weighted by the PN sequence was designed and an efficient timing and frequency offset estimation scheme for orthogonal frequency division multiplexing systems was proposed. The timing synchronization is accomplished by using the piecewise symmetric conjugate of the primitive training symbol and the good autocorrelation of the PN weighted factor. After the time synchronization...
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, the sampling frequency synchronization for OFDM systems is modeled as a frequency recovery loop, and how the noise component of the frequency recovery loop affects on the symbol synchronization is analyzed. Both the theoretical analyses and numeric simulation show the symbol synchronization is necessary for the coherent detection in an OFDM system because even small noise component...
In infrastructure-less wireless systems network-wise time and frequency synchronization can be achieved by exchanging mutual synchronization errors among neighboring nodes. Cooperative synchronization is based on the use of distributed digital locked loops (D-DLLs), as the extension to distributed systems of the classical concept of (analog or digital) locked loops. The convergence to a synchronized...
IEEE 802.1AS is being developed in the 802.1 working group as part of a set of standards for audio/video bridging (AVB). AVB networks will carry time-sensitive, high-quality, audio/video traffic, and IEEE 802.1AS will provide synchronization for these networks and ensure that the jitter, wander, and synchronization requirements for the time-sensitive traffic can be met. IEEE 802.1AS includes an IEEE...
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