Variable Data Rate Voice Encoder to Narrowband and Wideband Speech

摘要

Past designs for many military communications systems were based upon specific radio links with fixed and limited channel capacities. Accordingly, many different voice compression algorithms, operating at various fixed rates, were implemented. While still being used today, these incompatible systems are an obstacle to interoperable communications. Emerging net-centric communications promise to provide connectivity to all military users but voice interoperability will still require compatible voice encoding as well as encryption for secure communications. This report details a Variable Data Rate (VDR) voice encoder that is designed to provide interoperable secure voice communications for net-centric users. While being backwards compatible with the Federal standard voice encoder (MELP) at 2400 bits per second (bps), it operates at a range of data rates up to 26,000 bps. Because the rate setting can be changed dynamically, the VDR encoder can provide efficient use of network bandwidth yet be interoperable at any and all rates simultaneously, and, with the proper encryption, even when secure.