The WHOI micromodem-2: A scalable system for acoustic communications and networking

A successor to the WHOI Micromodem-1 underwater acoustic modem has recently been developed. The Micromodem-2 has the same compact form-factor as the Micromodem-1 and will support all of the existing applications for the Micromodem-1, as well as interoperate with the Micromodem-1. Existing acoustic communications protocols using phase-shift keying (PSK) as well as frequency-hopping frequency-shift keying (FH-FSK) are supported, as are navigation features including narrow-band and broadband long-baseline (LBL) navigation. The Micromodem-2 is significantly more capable than the Micromodem-1 in computational ability and memory, bandwidth, non-volatile data storage, user expansion interfaces, and real-time clock precision. The expanded capabilities will allow new communications algorithms, modulation, errorcorrection methods, navigation features, and networking capabilities to be implemented. The improvements in processing capability and acoustic interfaces on the Micromodem-2 allow it to operate at acoustic frequencies from approximately 1kHz to 100kHz. The significant increases in available non-volatile storage enable the Micromodem-2 to capture data in-situ for diagnostic and research purposes. The Micro mo dem-2´s firmware architecture is similar to the Micromodem-1´s firmware architecture, using a real-time operating system based on modular signal processing blocks. It has been improved to increase modularity and facilitate future portability, and it offers significant improvements in timing for use with navigation and networking applications.