摘要:
提出了一种水下正交频分复用(OFDM)系统鲁棒的频率偏移估计方法,即通信帧由一个训练帧和多个数据帧组成。其中克服大的多普勒频移,也就是粗频移估计(Rough Frequency Offset Estimation,RFOE),是通过训练帧来实现的,而克服时变的和小的多普勒频移,也就是精细多普勒频移估计(Accurate Frequency Offset Estimation,AFOE),是通过每一个数据帧实现的。RFOE和AFOE都是使用OFDM数据或循环前缀(Cyclic Prefix,CP)中没有被多径干扰的那部分数据计算得到的。在海试中,采用这种算法实现了通信速率与作用距离的乘积为133km·kbps的无误码通信,并比较了不同算法的试验结果,试验结果表明该算法能克服水下信道多径和时变的影响。
Abstract:
A robust frequency estimation scheme for acoustic underwater Orthogonal Frequency-Division Multiplexing (OFDM) system was proposed.The communication frame structure consists of a training frame and multiple data frames.The frequency offset is estimated by using the training frame,known as Rough Frequency Offset Estimation (RFOE),to overcome larger Doppler shift,while time varying and smaller frequency offsets are estimated by using every data frame,known as Accurate Frequency Offset Estimation(AFOE).Both RFOE and AFOE are calculated with the Cyclic Prefix(CP) segment which is not contaminated by multipath in the time domain.The underwater experiments achieved 133km·kbps at zero symbol error.Trial results of these two algorithms are compared.These results indicate that the algorithm is effective in time-varying and multipath underwater channels.
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