Satellite communication systems are able to provide diverse services for ground terminals in ubiquitous global coverage, which play a vital role in high-mobility communication environments Existing technologies developed primarily for satellite communications cannot be readily applied to satellite high-mobility communication scenarios, since high Doppler frequency offset caused by the fast movement of wireless terminals, and low signal-to-noise ratio (SNR) circumstances caused by limited link budgets in satellites incur more difficulty of the synchronization, especially for short burst transmission To solve such a problem in satellite high-mobility communications, we propose a novel method named GP-MASO-MLE, which consists of a coarse estimation algorithm based on the Gaussian process (GP) model and Newton-Raphson method, and a fine correction algorithm based on the improved maximum likelihood estimation (MLE) jointly with turbo decoding iterations Simulation results show that the proposed algorithm can approach to the bit error rate (BER) performance bound of ideal Doppler frequency offset correction within 01 dB, which can be well applied in code-aided (CA) satellite high-mobility communication systems for its good performance In addition, the computational complexity of the proposed algorithm is lower than other traditional turbo synchronization algorithms

Iterative Doppler Frequency Offset Estimation in Satellite High-Mobility Communications

The invention discloses a time-domain correlation and coding aiding based carrier synchronization method which achieves carrier synchronization by the aid of time-domain correlation functions of pilot frequency and output soft information of an iterative decoder of a coding system. Firstly, a pilot frequency and data add-drop frame structure is adopted, namely the pilot frequency is equally divided into two sections to be inserted into an initial position and a middle position of a data block; secondly, rough carrier estimation is performed by the aid of the time-domain correlation function of the pilot frequency, and a received signal is compensated by the aid of a rough estimation value; and finally, fine carrier estimation is performed by the aid of the time-domain correlation functions of the pilot frequency and the Turbo decoding soft information, and a fine estimation value is utilized for compensating the received signal to achieve effective carrier synchronization. The method includes the specific steps of baseband complex signal receiving, rough estimation, signal correction, soft demodulation, data demultiplexing, Turbo decoding expansion, hard decision, decoding termination condition, data multiplexing, and modulation and fine estimation. The method overcomes the defects of the prior art, and carrier frequency estimation accuracy is improved while operation complexity is lowered.

Time-domain correlation and coding aiding based carrier synchronization method

The invention discloses a carrier frequency offset estimation method based on time frequency joint. The carrier frequency offset estimation method mainly solves the problems that in the prior art, estimation precision is low under the condition that an estimation range is large, and the estimation range is small under the condition that the estimation precision is high. The carrier frequency offset estimation method comprises the implementation steps that (1) according to the influence of different frequency offsets on signal bit error rate performance, the fine estimation parameters of fine estimation aiming to achieve estimation precision under the condition of meeting signal-to-noise ratio losses are determined; (2) rough estimation parameters are determined according to the fine estimation parameters; (3) rough estimation is carried out by utilizing the rough estimation parameters to obtain a frequency offset rough estimation value fco; (4) the fine estimation is carried out by utilizing the fine estimation parameters to obtain a frequency offset fine estimation value fre; (5) finally, a frequency offset estimation value f is obtained, and f=fre+fco. In the estimation range that a normalization frequency offset ranges from -0.5 to 0.5, the estimation precision of the method can reach 3*10-5 and can even reach higher precision, and the method can be used for the carrier synchronization and wireless channel estimation of a wireless communication system.

Carrier frequency offset estimation method based on time frequency joint

In short burst communication system, a joint rotational periodogram averaging (RPA) and demodulation soft information carrier estimation algorithm is proposed in this paper. Firstly, the coarse carrier estimation is carried out with periodogram averaging method after that the pilot sequence is rotated with different frequency offsets. Then, further fine carrier estimation is done by stepwise searching on the criterion of Maximum-Mean-square Soft Output (M2S2O). Simulation results show that the proposed algorithm with short pilots and lower complexity can achieve an excellent Bit Error Rate (BER) performance and eliminate large carrier offsets as much as half of the symbol rate. When BER is in the region of 10-2~10-5, Signal-to-Noise (SNR) degradation is within 0.3dB.

A joint rotational periodogram averaging and demodulation soft information carrier synchronization algorithm

Considering low estimation accuracy and small synchronization range of carrier synchronization algorithms in low signal-to-noise ratio (SNR) for short burst communication systems, a joint time-domain correlation and code-aided carrier synchronization algorithm is proposed. Firstly, a frame structure in which the pilot symbols are separated with data symbols is used. Then, a new frequency estimation method using the summation of the entire cross correlation is deduced based on the time-domain correlation frequency estimation criterion. Based on this, the summation of the cross correlation of the pilot symbols after removing modulation is utilized to perform coarse synchronization and of the pilot symbols and decoding soft information is utilized to perform fine synchronization. So a joint time-domain correlation and code-aided carrier synchronization algorithm is obtained. Simulations by the Turbo code verify that the proposed algorithm can obtain higher estimation accuracy with only 32 QPSK pilot symbols, and the SNR degradation of Turbo decoder is within 0.5dB when the normalized frequency offset is smaller than 1.5×10-3.

Joint time-domain correlation and code-aided carrier synchronization algorithm

To solve the carrier recovery problem with large frequency offset in short burst communication systems using shaped-offset quadrature phase shift keying(SOQPSK), a joint pilot and demodulation soft information carrier synchronization algorithm is proposed. First, a coarse estimation based on a few short pilot sequence is carried out. Then, further fine search is done around the coarse estimation region. The precise carrier synchronization parameters are obtained based on the maximum-mean-square soft output of SOQPSK Simulation results show that at E b N 0 >0dB the proposed algorithm can eliminate large carrier offsets as much as half the data rate, resist phase confusion and achieve effective carrier synchronization with only 30 pilot bits and low computation complexity, achieving a BER performance which is very near that of the optimal coherent demodulation. When BER is in the region of 10−2∼10−5, SNR degradation is within 0.3dB.

Zhu Jili

Papers

A joint pilot and demodulation soft information carrier synchronization for SOQPSK signals