Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency errors. In this paper, a new method utilizing pilots to do frequency synchronization in frequency domain is proposed with large estimation range. It needs no such prerequisite assumption that a perfect symbol timing synchronization [IEEE Transactions on Communications 42 (1994) 2908; 45 (1997) 1613] has been done before performing integer carrier frequency synchronization. Also, a new adjusting model for fine carrier frequency is proposed. Simulation and performance analysis show that our overall frequency estimator has high accuracy. The corresponding FPGA circuit through test in high definition TV (HDTV) prototype in Team of Expert Engineering Group (TEEG) in China proves its availability and feasibility.

Timing jitter, frequency offset, carrier phase jitter and sampling clock frequency offset are the main synchronization errors encountered by OFDM systems. As many literatures have proved, OFDM systems are very sensitive to frequency errors. In this paper, an improved method to do decimal frequency offset estimation in time domain is proposed. In addition, lots of simulations have proved that when the decimal frequency offset in data streams approaches to 0.5 of the subcarrier spacing, a wrong estimated frequency offset with inverse polarity will be presented, therefore, a novel adjusting model to deal with this problem is also proposed in this paper. Simulation results show that the mean square error (MSE) can be significantly improved by over three order of magnitude at high SNR with the proposed method compared with the conventional method [1], [2]. The correspondent Field Programmable Gate Array (FPGA) circuit through test in HDTV prototype in Team of Engineering Expert Group (TEEG) proves its feasibility and availability.

The latest research works on the synchronization scheme for either continuous transmission mode or burst packet transmission mode for the wireless OFDM communications are overviewed in this paper. The typical algorithms dealing with the symbol timing synchronization, the carrier frequency synchronization as well as the sampling clock synchronization are briefly introduced and analyzed. Three improved methods for the fine symbol timing synchronization in frequency domain are also proposed, with several key issues on the synchronization for the OFDM systems discussed.

该文提出了在多径衰落信道环境下，宽带数字电视地面广播BDB-T系统中符号定时恢复的改进新算法，导出了计算公式井设计了相应的FPGA硬件电路，计算机仿真驶在高清晰度数字电视功能样机上的调试证明了改进算法的优良性能。

Most existing methods for HPA predistortion with memory effects are based on polynomial or indirect learning structures. Few papers concern about the memory predistortion with LUT based techniques. Based on the previously presented method, we propose an improved two-dimensional LUT indexing method for HPA predistortion with memory. Computer simulations and corresponding analysis demonstrate that the proposed method has more effective predistortion capabilities but lower computational complexity.