ADAPTIVE ENCODE DELAY TO REMOVE PACKET TIMING JITTER
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-28
In the current iDEN 3:l system, because the VSELP encode process runs at a background priority and can be interrupted by the decode process and because the VSELP encode inherently has a wide CPU loading depending on the type of voice stream being encoded, there exists a substantial timing variation in the encode times of various voice frames. These types of processes (i.e. 6: 1 or 3: I VSELP) are usually data-driven and a packet is generated whenever the VSELP encode is complete. For the iDEN 3:1 system, this variation is some- times too much and results in the Base Radio (BR) dropping voice packets over the air causing very choppy audio. The variation also makes JITA lock- ing either slow or non-converging, also causing choppy audio. The iDEN 6:l system sends out packets whenever the VSELP encode process is fin- ished. In Figure I, the encoded packets are sent out whenever the encode is finished. In the diagram, an example is shown of decode and encode timing in a worst case type of situation. This results in extreme timing variation.