Adaptive Doppler compensation for direct-sequence spread-spectrum underwater acoustic communication

作者：Lei K^*; Han J; Huang J

来源：Journal of Northwestern Polytechnical University, 2010, 28(6): 829-833.

• Direct-sequence spread spectrum
• Doppler compensation
• Doubly-spread channel
• Underwater acoustic communication

In the direct-sequence spread-spectrum underwater acoustic communication, carrier tracking and symbol synchronization are adversely affected by the movement between the transmitter and the receiver. In this case, conventional RAKE receiver may fail to function and Doppler compensation must be adopted. However, the existing methods of Doppler compensation employ only one interpolator, this will lead to residual Doppler and performance degradation of the receiver in frequency-spread channel. So in this paper, an algorithm is presented for direct-sequence spread-spectrum communication, which is implemented as follows: First, by Fig. 1 and Eq. (4), the cross-ambiguity function is calculated and the path delay τ k and Doppler Δ k are initially estimated. Then, by Eq. (6) through (10), polyphase filter interpolator is combined with RAKE receiver to perform Doppler compensation at symbol rate on each path of the channel. Finally, as shown in Fig. 2-(b), the demodulated symbols on each path are considered as time diversity and combined by RAKE receiver. By simulations in doubly-spread underwater acoustic channel, our method of Doppler compensation achieves error-free demodulation (Fig. 6) and outperforms the existing method with higher signal-to-distortion ratio (Fig. 5) and 5dB output SNR signal-to-noise ratio (Fig. 7), thus has better capability of tracking the time-varying channel.

• 出版日期2010
• 单位西北工业大学