Implementation of underwater acoustic modem based on the OMAP-L138 processor

With the development of underwater acoustic (UWA) communication network technology and improvement of embedded digital signal processing chip, acoustic modem has received much attention recent years. By analyzing power consumption, board size, reliability and flexibility in application, we implement the acoustic modem based on the OMAP-L138 board. The modular algorithm is based on block-by-block processing. We used feedback buff from previous block as well as pre-data from next block to ensure the continuity of the entire frame signal. To match the A/D sampling frequency of integrated TLV320AIC23B codec, we proposed block-resampling algorithm based on polyphase filter. By analyzing the workload, an optimized algorithm of block resampling is put forward. The time complexity has been reduced by a factor of I or D. The acoustic modem proposed in this paper has been tested using data collected from lake experiment. The communication rate can reach 4kbps with BER performance of 10^-3-10^-4. The results of off-line processing indicate that high-speed, stable and real-time data transmission can be achieved by using the hardware and algorithm mentioned above.