Joint Synchronization Algorithm Research Articles

FPGA implementation of joint synchronization algorithm based on short training sequence

Synchronization processing is a vital component of the Orthogonal Frequency Division Multiplexing (OFDM) receiver, playing a decisive role in determining the performance of the OFDM receiver. Based on the repetitive structure of the Short Training Sequence (STS) in the IEEE 802.11 physical layer protocol data unit, this paper proposes and implements a joint synchronization algorithm to address issues related to data packet detection and coarse frequency offset correction during the synchronization process. Through software simulation and Field-Programmable Gate Array (FPGA) board-level validation, it is concluded that the algorithm ensures performance while, to some extent, conserving FPGA resources.

Robust timing and frequency joint synchronization method for QNSC-enabled security optical communications system based on CO-OFDM

The security of optical fiber communication network has been paid more and more attention, and Quantum Noise Stream Cipher (QNSC) can guarantee its physical layer security. However, the QNSC system realized with CO-OFDM technology is very susceptible to timing synchronization error and carrier frequency offset. Existing symbol timing and frequency synchronization algorithms based on preambles have problems of timing metric platform, interference of side lobes, and low timing and frequency synchronization accuracy especially in optical signal transmission scenario of high-order modulation and low SNR. Furthermore, the preamble is not encrypted, which can be easily identified by illegal receiver. In order to solve above problems, a robust timing and frequency joint synchronization algorithm is proposed. The algorithm is composed of the preamble interleaved by conjugate, negative and image sequences of original element sequence. The preamble conforms to the preamble structure of Schmidl, Minn and CNI by adding negative and conjugate operator at the specific interval of the preamble. The correspond timing metric method, i.e. combination of Schmidl, Minn and CNI timing metric strategies, can fully extract characteristics of the preamble, and then timing and frequency joint synchronization is accurately obtained. For timing synchronization, experiments in 10Gbit/s CO-OFDM based QNSC system have illustrated that proposed algorithm has better timing synchronization performance than baseline algorithms. The detection probability is augmented and timing offset mean is decreased than that of baseline algorithms especially at low SNR. The simulation illustrates that proposed algorithm has more accurate frequency offset (FO) estimation performance compared with the baseline algorithms even at low SNR. Furthermore, the simulation illustrates the security performance of CO-OFDM based QNSC system is improved by encrypting the preamble with secret key.

A Low Complexity joint synchronization algorithm based on CAZAC sequence for OFDM system

To solve the problem of timing ambiguity and reduce the complexity of integer frequency offsets (IFO) estimation for OFDM system, this paper proposes a novel synchronization algorithm based on CAZAC sequence in time domain. The algorithm constructs a training sequence with conjugate and symmetry properties. Firstly, timing synchronization and IFO estimation are completed simultaneously by utilizing the cross-correlating of the training sequence and local signal based on the analysis of the impact of IFO on the timing of meric peak positions. Then the fractional frequency offsets (FFO) estimation is done using the repeatability of the symmetrical training sequence. Compared with the existing representative algorithms, the proposed algorithm achieves better synchronous performances with lower computational complexity and acceptable transmission efficiency.

Design of OFDM Joint Synchronization Algorithm Based on Cyclic Prefix

By studying the Maximum Likelihood (ML) algorithm and applying it to Orthogonal Frequency Division Multiplexing (OFDM) system, we analyze its performance. OFDM system has obvious advantages over other wireless communication systems, but it also has disadvantages, such as being sensitive to synchronization errors. The ML algorithm can solve this shortcoming of OFDM system. ML algorithm uses the redundant information carried by the cyclic prefix in OFDM code element. At the same time, ML algorithm calculates its maximum likelihood estimation algorithm to complete the code element timing synchronization and carrier frequency synchronization. Compared with other synchronization algorithms, ML algorithm can complete initial capture and synchronous tracking in one step, so it is widely used in OFDM systems. In this paper, we build a traditional OFDM system and apply the ML algorithm to OFDM synchronization simulation. By changing the design of relevant parameters, we describe the ML algorithm in detail and obtain the same results as the theory.

Efficient joint timing and frequency synchronization algorithm for coherent optical OFDM systems.

A joint timing and frequency synchronization algorithm is proposed for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems. The timing and frequency synchronization is realized by using only one training symbol which is composed of conjugated symmetric sequence. The timing estimation of the proposed algorithm has the advantage of being robust to poor optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD), and the frequency estimation range of fractional subcarrier spacing can be achieved. The feasibility and effectiveness of the proposed joint synchronization algorithm is verified in both simulations and a 47.3 Gbit/s 16-ary quadrature amplitude modulation (16-QAM) CO-OFDM system.

A joint synchronization parameter estimation in fractional Fourier transform orthogonal frequency division multiplexing underwater acoustic communication system

In the conditions of Gaussian noise, symmetric alpha stable impulse noise, multipath propagation, Doppler effect, and so on, a joint synchronization algorithm is proposed for underwater acoustic communication system based on fractional Fourier transform orthogonal frequency division multiplexing. The algorithm realizes the orthogonal multicarrier underwater acoustic communication system synchronization based on that the symmetrical triangular linear frequency modulation signal has the energy convergence in the domain of fractional Fourier transform. In order to verify the effectiveness of the algorithm, hyperbolic frequency modulation signal and linear frequency modulation signal are used as the evaluation index, and the synchronization performance of bit error rate of them is compared by simulation and pool experiments. The simulation results show that the proposed algorithm in this article is resistant to Gaussian noise, symmetric alpha stable pulse noise, multipath propagation, and Doppler effect, compared with traditional synchronization algorithms; the synchronization error probability is low at the same signal-to-noise ratio.

A Novel Joint Synchronization Algorithm for OFDM Systems based on Single Training Symbol

A Novel Joint Synchronization Algorithm for OFDM Systems based on Single Training Symbol