Long haul communications in the HF spectrum utilizing high speed modems

Abstract

In the past ten years reliable high-speed satellite systems have pushed slower less reliable communication systems to the bottom of the list for development programs. Concern over reduced budgets, vulnerability of expensive satellite systems, and recent advances in HF technology are creating new interest in upgrading existing HF communication systems. Nondevelopment Items (NDI) are defined as the use of off-the-shelf commercial items instead of costly, time-consuming conventional research and development programs. The Navy Department's current policies are designed to insure the maximum use of NDI to fulfill Navy requirements. The speed of HF systems can be improved using current signaling and modulation techniques, and reliability can be increased by error-correcting codes or error detection used in conjunction with automatic repeat request (ARQ) schemes. Improved HF systems not only provide survivable back-up capability, but increased capacity for present communication needs.