Journal of Xidian University

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Joint carrier synchronization and symbol timing for MQAM in non-cooperation communication systems

LIU Mingqian1,2,3;CHEN Qian2;WU Yun3;LI Bingbing1   

  1. (1. Collaborative Innovation Center of Information Sensing and Understanding, Xidian Univ., Xi'an 710071, China;
    2. School of Electronic and Optical Engineering, Nanjing Univ. of Science and Technology, Nanjing 210094, China;
    3. Xuzhou LEO Medical Equipments Co., Ltd., Xuzhou 221116, China)
  • Received:2017-01-04 Online:2018-02-20 Published:2018-03-23


Aiming at the problem of symbol timing and carrier synchronization of (M-ary Quadrature Amplitude Modulation) MQAM signals with large symbol rate deviation in non-cooperative communication systems under multipath channels,a new method based on the improved Gardner algorithm for MQAM signal timing carrier joint synchronization is proposed. First, the method obtains timing offset estimation and carrier offset coarse estimation using the relationship between frequency offset and output value of the Gardner algorithm. Then, locking is performed with the difference of the absolute value between estimation and the output value of timing error detection which is half a symbol different from the estimation. Finally, the method uses the phase-locked loop to track the fine frequency offset and phase offset. Simulation result shows that the proposed joint estimation method of timing offset and carrier offset has a good estimation performance under the condition of multipath channels.

Key words: synchronization, symbol timing, carrier frequency offset, joint estimation, non-cooperation communication