CAJ | 학술논문

正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术具有抗多径、频带利用充分、传输数据率高的优点，在水声通信中具有重要的发展前景。由于多普勒频移和多径时延的存在，需对OFDM信号进行时间同步。同步不准会引起OFDM水声通信中符号间干扰和子载波间干扰，提出了一种基于叠加单频序列的短时傅里叶变换(STFT)时间同步方法，该方案首先提取叠加在OFDM符号上的单频信号，对该信号进行短时傅里叶变换，随后对其时频幅度谱进行分析，利用平坦区域确定同步时刻。仿真和试验结果表明，该方案有效可行。
정교빈분복용(Orthogonal Frequency Division Multiplexing, OFDM)기술구유항다경、빈대이용충분、전수수거솔고적우점，재수성통신중구유중요적발전전경。유우다보륵빈이화다경시연적존재，수대OFDM신호진행시간동보。동보불준회인기OFDM수성통신중부호간간우화자재파간간우，제출료일충기우첩가단빈서렬적단시부리협변환(STFT)시간동보방법，해방안수선제취첩가재OFDM부호상적단빈신호，대해신호진행단시부리협변환，수후대기시빈폭도보진행분석，이용평탄구역학정동보시각。방진화시험결과표명，해방안유효가행。
Orthogonal Frequency Division Multiplexing (OFDM) is a method that can combat multipath, fully use the frequency band and have high data transmission rate. Consequently it has a promising future in underwater acoustic communication. Underwater channel is a Doppler-distorted, high noised and time-varying multipath channel. Due to the existence of multipath and Doppler shift, timing synchronization plays a key role in OFDM systems. In this paper, a timing synchronization method based on short time Fourier transform (STFT) is proposed. First, STFT is operated on the outcome of the received single frequency signal accompanying the OFDM symbol, and then the time-frequency spectrum is obtained for calculating the summation of the outcome after STFT and finding the edge which is the original point of the underwater acoustic OFDM symbol. The results of simulations show good performance of this method even under low ratio of signal to noise.