Study Of Allied Time And Frequency Coding Underwater Acoustic Communication Based On Ofdm Technology

Orthogonal frequency division multiplexing (OFDM) has both high spectrum efficiency and data transmission rate. Therefore, high-speed communication based on OFDM has been studied because of the limited band-with in underwater acoustic channel. Spread spectrum (SS) technology has good ability to confront interference, and has been widely used in underwater networks. In the paper, an allied time and frequency coding communication model is built combing OFDM and SS technology. The model has good ability to confront narrow-band interference and can further increase the data rate in point-to-point communication.The main research of the paper includes three parts as follows:1. Analyzed the influence caused by narrow-band interference in underwater acoustic channel. Analysis and simulation result indicates that, the interference can increase the bit error rate (BER).2. Allied OFDM and SS technology to build a time and frequency coding model (TF-OFDM), presents a signal detection and decoding method.3. Analyzed the data rate of TF-OFDM system and its performance in confronting narrow-band and multi-path interference in underwater channel, computer simulation result indicates that, in high SNR, TF-OFDM has better BER performance in low SNR, it has the same BER with OFDM;TF-OFDM has increased the transmission data rate and has good ability to confront multi-path interference ,compared to OFDM system. The TF-OFDM requires a higher SNR (≥3dB in the paper) in signal detection and decoding, meanwhile, TF-OFDM has increased system complexity and computation amount.