Proteus II: Design and Evaluation of an Integrated Power-Efficient Underwater Sensor Node

Abstract

We describe the design and evaluation of an integrated low-cost underwater sensor node designed for reconfigurability, allowing continuous operation on a relatively small rechargeable battery for one month. The node uses a host CPU for the network protocols and processing sensor data and a separate CPU performs signal processing for the ultrasonic acoustic software-defined Modulator/Demodulator (MODEM). A Frequency Shift Keying- (FSK-) based modulation scheme with configurable symbol rates, Hamming error correction, and Time-of-Arrival (ToA) estimation for underwater positioning is implemented. The onboard sensors, an accelerometer and a temperature sensor, can be used to measure basic environmental parameters; additional internal and external sensors are supported through industry-standard interfaces (I2C, SPI, and RS232) and an Analog to Digital Converter (ADC) for analog peripherals. A 433 MHz radio can be used when the node is deployed at the surface. Tests were performed to validate the low-power operation. Moreover the acoustic communication range and performance and ToA capabilities were evaluated. Results show that the node achieves the one-month lifetime, is able to perform communication in highly reflective environments, and performs ToA estimation with an accuracy of about 1-2 meters.

Underwater Acoustic Micromodem for Underwater Internet of Things

“…For shallow water communication, it can reach the data rate of 30 bit/s. Lee et al [13] use STM32F103 as the core processor to realize UAC at the speed of 5 kbit/s within a distance of 500 m. A low-power, low-cost underwater sensor node called Proteus II was described in [14], and its acoustic modem uses FSK modulation and is able to communicate 150 bit/s at a range of 140 m in lake experiment. The acoustic modem called ahoi developed by Renner et al [15] keeps the cost within $600 and can achieve 1 and 2.…”