Jinhua Sun

Joint pilot and iterative decoding carrier synchronization for short burst transmission system

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 pilot and iterative decoding soft-output carrier synchronization algorithm is proposed, which utilizes the time-domain correlation algorithm for coarse estimation and makes hard decision directly for systematic soft-information and parity soft-information from extended Turbo decoder, and obtains the prior probability for fine estimation which is based on ML algorithm. Theoretical analysis and simulation results show that Turbo decoder can obtain more reliable soft-output information with small residual frequency offset after initial coarse synchronization when the normalized frequency offset is less than 1.5×10-3, then joint pilot and soft-output from the decoder are used to estimate fine carrier parameters, which can make turbo code achieve optimal BER performance.

Pilot design of data-aided carrier synchronization for short burst transmission

In short burst communication system, the position and the number of pilot symbols have a great effect on frequency estimation accuracy and estimation range based on time-domain correlation frequency estimation algorithm. So a frequency estimation algorithm having a higher frequency estimation accuracy based on the summation of the entire cross correlation is given, and its estimation variance is derived. By analyzing the effect of pilot position in a burst on estimation accuracy and estimation range, a scheme of variable D - spaced preamble middle(VDPM) frame structure is proposed which can choose the distance between pilot blocks according to systems requirements for estimation accuracy and estimation range. Simulation results show that the frame structure can satisfy the requirements for frequency estimation range and estimation accuracy, and the estimation algorithm can achieve a higher estimation accuracy with only a few pilot symbols which is suitable for short burst communication system.

A Phase Increment-Based Frequency Estimator for General PSAM in Burst Communications

In this paper, a two-stage phase-increment-based frequency estimator with a general pilot-symbol-assisted- modulation (PSAM) structure is proposed for burst-mode communications. We derive the true Cramer-Rao bounds (CRBs) under the general PSAM structure for pure data-aided (DA) estimator. The proposed phase increment-based estimator is a pure DA estimator and implemented via two stages. In the first stage, a joint auto-correlation with one-symbol delay (AC-1) and simplified L&R (S-L&R) estimator is employed for the coarse estimation. In another stage, a two-step simplified cross-correlation algorithm with three disjoint pilot blocks is proposed for the fine estimation, where the problem of phase ambiguity is solved in the first stage such that wide estimation range as large as half of symbol rate can be guaranteed, and the fine estimation improves overall estimation accuracy. It is shown that the proposed estimator exhibits wide operating range while providing both high accuracy and moderate complexity, and efficient pilot utilization.

Joint time-domain correlation and code-aided 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.

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

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.

Carrier frequency offset synchronization algorithm for short burst communication system

The problem of carrier frequency and phase synchronization exists in most wireless digital communication systems. These offsets are generally results from the Doppler effect, oscillator instabilities, and unknown transmission delays between receiver and transmitter. In this paper, we propose a joint synchronization algorithm applicable for short-burst PSK modulation systems. In the coarse estimation, the M&M estimator is utilized to guarantee wide estimation range nearly 45% of symbol rate. In order to improve the poor estimation accuracy of M&M estimator, we choose cross correlation with far spacing between two adjacent pilot blocks. The length of the pilot blocks and the spacing between pilot blocks are designed according to the requirement of bit error ratio(BER) performance loss and efficient spectrum utilization. Simulation results reveal that the proposed joint algorithm can correct very wide frequency offsets with performance near the ideal situation at limited pilot symbols.

Multi Block Overlapping Zero Padding Algorithm for Weak Signal Acquisition

Global navigation satellite systems (GNSS) can implement high-precision navigation and positioning, requiring rapid and accurate signal acquisition under very weak signal conditions. Double block zero padding (DBZP) is an efficient algorithm for unaided weak signal acquisition. Considering the acquisition problem of weak direct sequence spread spectrum continuous phase modulation signal, the subblock combining and zero padding method is studied in detail. To solve the weakness of fixed number of subblock and fixed number of signal samples in each subblock given frequency resolution and Doppler searching range in DBZP, a multi block overlapping zero padding (MBOZP) algorithm is proposed, which combines with the ideas of data subblock overlapping. This algorithm optimizes the combination of data subblock by introducing the data subblock overlapping, which can increase the length of coherent accumulation and improve the performance of acquisition under the determined frequency resolution and Doppler searching range. Compared with the traditional DBZP, the simulation results show that MBOZP can obtain higher acquisition probability at small frequency offset.

The joint frequency-phase estimate based on symmetrical burst

Considering the great influence of the residual frequency offset on the phase estimate in burst-mode communication systems, the symmetrical frame structure is applied to the joint frequency-phase estimate. Firstly, based on a general data frame structure, the Cramer-Rao Bounds(CRBs) for asymmetrical burst and symmetrical burst with DA/NDA synchronization mode are given. Secondly, the concept of symmetrical burst is used in the joint frequency-phase estimator, comparison and analysis are made compared with asymmetrical case. On this basis, the pre-phase/post-phase offset estimators are proposed. Theoretical analysis and simulation results show that compared with the maximum likelihood phase offset estimate based on the asymmetrical burst, the estimate based on symmetrical structure can achieve lower mean square error and has greater ability against the residual frequency offset. Besides, the symmetrical burst has universality which can be applied to other phase offset algorithms.

A joint time-frequency domain algorithm for carrier frequency estimation

To solve the problem that both the estimation range and estimation accuracy cannot be satisfied at the limited pilot overhead for data-aided carrier synchronization in burst signals, a new joint time-frequency carrier frequency offset estimation algorithm is proposed. The basic idea of the algorithm is combining the advantages of wide estimation range of frequency-domain estimation algorithms and high estimation accuracy of time-domain estimation algorithms. Firstly, the coarse frequency offset is estimated by frequency-domain periodogram peak, then the remaining frequency offset is estimated by the summation of the entire time cross correlation. System parameters design needs trade-off between the error performance requirement and system complexity. Simulation results show that the algorithm has high estimation accuracy within the estimated range of 50% of the symbol rate, and it has low complexity which is suitable for short burst communication systems.

Green communication: Adaptive carrier synchronization system design

Considering both large cost and high complexity of current carrier synchronization systems at low Signal-to-Noise Ratio (SNR), an adaptive carrier synchronization system design in accordance with Green communication is proposed. First, the proposed design takes advantage of parameter control method to change an optimal scheme to some suboptimal schemes. Within the requirement of satisfying less SNR degradation it is then by comparing these suboptimal schemes to pick out the schemes with both small cost as well as low complexity. Simulation results and analysis show that for the optimal scheme the SNR loss is only 0.1dB, but for the suboptimal schemes the normalized pilot cost and complexity can be reduced at most by 16 percent and 38 percent respectively, which is accordable with the concept of Green communication.