UC San Diego

Underwater wireless sensor networks are crucial in understanding certain phenomena that take place within our vast oceans. They can be used as an integral tool in countless environmental monitoring applications like understanding the growth and spread of algal blooms and monitoring the health of coral reefs. These networks often rely on acoustic communication, which poses a number of challenges for reliable data transmission. Three of these key challenges are high power consumption when transmitting, frequency selective fading, and high variability in the communication channel over time due to factors like multipath delay spread, doppler shift, and noise interference due to low SNRs. Current modems are traditionally configured for specific environments and must withstand the worst anticipated channel conditions. This tendency limits potential performance of the modem when the channel improves. This thesis introduces the design of a low cost underwater acoustic modem that can measure the underwater communication channel and adapt its bit rate and modulation scheme to maintain reliable data transmission while optimizing data rates and effectively minimizing power consumption