Impairment reduction for tandem VoIP calls

Abstract

A method and apparatus are provided for allowing IP endpoints to communicate over a PSTN with improved signal quality. Watermarks are used in the handshaking between the end-points when a communication session is being established, the watermarks indicating that the endpoints are capable of VoIP. If the two end-points establish that they are each VoIP-capable then packet data is inserted into a TDM channel using a framing technique managed by the gateways, with the bearer data being native to the VoIP devices, avoiding the lossy conversion of packet-voice data to 64 kb/s PCM and back to packet data again, realizing that the other end-point will be able to decode the data. If an IP-enabled endpoint determines that the other endpoint is not IP-enabled, then the data is inserted into the TDM channel by the gateway after conversion to 64 kb/s PCM so that the resulting TDM stream remains compatible with the PSTN and non-IP endpoints.

Dependencies are inferred from the claim text.