Compressed voice in integrated services frame relay networks: voice synchronization

The simplicity of the frame relay (FR) protocol, designed primarily for data communications, makes it difficult to apply existing voice synchronization algorithms requiring network layer (OSI layer 3) processing for voice transmission. The paper presents a novel adaptive playout algorithm, designed to absorb network delay jitter by adaptive variation of the holding time of voice packets at the playout buffer. The algorithm requires no common time-reference between sender and receiver or special processing in the FR switches and has been optimized to operate in a mixed voice-data FR environment characterized by bursty interLAN Ethernet traffic. It meets the quality of service (QoS) requirements of conversational voice applications. Performance evaluation of the playout algorithm includes quantitative simulation results as well as qualitative subjective tests using speech coders.