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Li Y.,Xidian University | Tian B.,Xidian University | Yi K.,Xidian University | Yu Q.,Xidian University | And 3 more authors.
IEEE Communications Letters | Year: 2016

In this letter, a robust nondata-aided (NDA) carrier tracking method is proposed for low-density parity-check (LDPC) coded systems with symbol rate sampling. The proposed method has a novel and hybrid carrier tracking loop combined with the frequency-locked loop (FLL), increasing/decreasing sampling rate blocks, phase-locked loop (PLL), and modified symbol decision method, which is capable of improving estimation accuracy of the frequency offsets and phase offsets at low signal to-noise ratios (SNRs). When applied to the (4096, 3072) LDPC coded system, numerical simulations and comparisons are provided to validate the effectiveness of the proposed carrier tracking method in the case of relatively low SNRs. © 2015 IEEE. Source


Li Y.-H.,Xidian University | Tian B.,Xidian University | Yi K.-C.,Xidian University | Yu Q.,Xidian University | And 2 more authors.
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2016

For carrier synchronization in the case of symbol rate sampling and low signal to noise ratios (SNRs), a novel hybrid carrier tracking loop is proposed, and an intuitive method of determining loop parameters is also investigated. The carrier synchronous loop improves the estimated accuracy of the carrier frequency offset and the phase offset in low SNR environments through modifying the original symbol hard decision method and adding sampling rate conversion blocks which enable the digital frequency-locked loop (FLL) and digital phase-locked loop (PLL) to operate under the condition of different rate sampling. The parameter determination method selects optimal parameters in the z-domain directly according to the stability and unit step response characteristics of the closed-loop systems. Simulation results confirm the feasibility of this algorithm in terms of determining the parameters and indicate that the proposed carrier tracking loop achieves better synchronization performance at relatively low SNRs. © 2016, Chinese Institute of Electronics. All right reserved. Source


Li Y.,Xidian University | Tian B.,Xidian University | Yi K.,Xidian University | Yu Q.,Xidian University | Yu Q.,Institute of Chinese Electronic Equipment System Engineering Corporation
Digital Signal Processing: A Review Journal | Year: 2016

In digital communication systems, typical methodologies in determining loop parameters of the digital phase-locked loop (DPLL) are based on the mapping transformation from the analog domain to the digital domain. However, such transform based algorithms are relatively complicated and not straightforward, and they also cause the problem that loop parameters are affected by the pre-detection integration time greatly. To solve these issues, an effective direct method of determining loop parameters of the second-order DPLL in the z-domain is proposed in this paper. Through ascertaining specific positions of the closed-loop system function's poles inside the right-hand side of the z-plane's unit circle, unknown parameters are calculated directly and flexibly in this method, which enables the DPLL to acquire good low-pass filtering characteristic and system stability. This novel method not only reduces the complexity of solving the parameters, but also eliminates the effect of the pre-detection integration time on loop parameters. Simulation results are provided to confirm the feasibility of the proposed method and to show that the DPLL obtained by this method achieves the similar tracking performance to the discretized PLL. © 2016 Elsevier Inc. All rights reserved. Source


Li Y.,Xidian University | Tian B.,Xidian University | Yi K.-C.,Xidian University | Yu Q.,Xidian University | Yu Q.,Institute of Chinese Electronic Equipment System Engineering Corporation
IEICE Transactions on Communications | Year: 2016

In modern communication systems, it is a critical and challenging issue for existing carrier tracking techniques to achieve nearideal carrier synchronization without the help of pilot signals in the case of symbol rate sampling and low signal-To-noise ratio (SNR). To overcome this issue, this paper proposes an effective carrier frequency and phase offset tracking scheme which has a robust confluent synchronization architecture whose main components are a digital frequency-locked loop (FLL), a digital phase-locked loop (PLL), a modified symbol hard decision block and some sampling rate conversion blocks. As received signals are sampled at symbol baud rate, this carrier tracking scheme is still able to obtain precise estimated values of carrier synchronization parameters under the condition of very low SNRs. The performance of the proposed carrier synchronization scheme is also evaluated by usingMonte-Carlo method. Simulation results confirm the feasibility of this carrier tracking scheme and demonstrate that it ensures that both the rate-3/4 irregular low-density parity-code (LDPC) coded system and the military voice transmission system utilizing the direct sequence spread spectrum (DSSS) technique achieve satisfactory bit-error rate (BER) performance at correspondingly low SNRs. Copyright © 2016 The Institute of Electronics, Information and Communication Engineers. Source


Zhao J.,PLA Military Transportation University | Jia P.,PLA Military Transportation University | Jia P.,Institute of Chinese Electronic Equipment System Engineering Corporation | Fu S.,PLA Military Transportation University
Proceedings - 2012 IEEE 2nd International Conference on Cloud Computing and Intelligence Systems, IEEE CCIS 2012 | Year: 2012

In the research domain of intelligent driving technology, modeling of the dynamic and uncertain environment is very important for path planning. The accuracy and computational efficiency of path planning depend on environment modeling to a great extent. Inspired by selective attention mechanism of human, this paper proposes multi-scale grid method to model the road environment of intelligent vehicle. The road environment is divided into multi-scale grids. The grids representing the regions close to the vehicle are of large size. The grids representing the regions far away from the vehicle are of small size. The multi-scale gird function is presented to calculate the size of grid. Experimental results show that the proposed algorithm provides an efficient solution to the conflict between computational complexity and modeling accuracy. © 2012 IEEE. Source

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