Communications aspects of underwater telemetry

Problems associated with reliable underwater telemetry are studied in three categories dictated by the degree to which multi-path propagation effects are experienced. The maximum range obtainable under ideal conditions of a typical telemetry system is investigated as a function of the required information bandwidth. The relevant acoustic properties of the sea are summarized and systems, originally used in electromagnetic communication to combat `flat¿ and `frequency selective¿ fading are reviewed and their adaptability to thepresent application is discussed. Inter-symbol distortion arising from large differential delays during multi-path propagation is discussed and some proposals are made for the realization of a practical system particularly suitable for underwater telemetry where large path differentials are encountered.