A modular approach to packet voice terminal hardware design

Abstract

In addition to encoding and decoding speech, packet voice terminal functions include packetization and depacketization; the application and interpretation of voice, internet, and local network protocols; dialing, ringing, ancillary signaling; and interface to local network transmission media. In this paper we describe a modular packet voice terminal design in which the partitioning of the hardware is effected along these basic functional lines. Interfaces are provided between the speech processing, protocol handling, and local network interfacing functions such that each of these is implemented in a physically independent module with considerable freedom for modifying or replacing any one module independently of the others. This allows for a broad choice of voice coders on the one hand, and a variety of local network types on the other. Specific modules discussed include a microprocessor-based protocol-handling section, an interface module to a local area coaxial cable network which uses a contention-based mechanism for packet voice communication, and a variety of voice coder/decoder designs covering the rate spectrum from 2.4 to 64 kbps.