OFDM-System Design Using Adaptive Modulation and Channel Estimation for Underwater Acoustic Communication

Underwater Acoustic (UWA) channels are known as some of the most challenging communication media. Since the Underwater acoustic channels are time varying multipath channel achieving the high data rate, a low latency and a high throughput which often is a very difficult objective. In this work, we designed an OFDM transceiver system which is suitable for underwater acoustic communication with limited bandwidth to enhance the data rate at the receiver. To enhance the data rate at the OFDM receiver we have used efficient adaptive modulation scheme, channel estimation and channel equalization schemes for UWA communication. We have focused on the efficient modulation schemes like QPSK, DPSK and 16-QAM which is best suited for adaptive techniques based on the SNR of the Rayleigh fading channel to enhance the data rate. The simulation results show that the performance of the OFDM system with the use of Adaptive modulation is better when compared to the OFDM system without Adaptive modulation schemes. Also we have used the Kalman filter for channel estimation which minimizes the mean squared error and gives us the best estimation even in the presence of noise. From the simulation results, we have found that these modulation techniques and channel estimation method are best suited to achieve high data rate for underwater acoustic communication.