Packet transport of VBR interframe DCT compressed digital video on a CSMA/CD LAN

The feasibility of providing teleconference/picturephone video services over 10-Mb/s IEEE 802.3 CSMA/CD (carrier sense multiple access with collision detection) local area networks is examined. The system considered is based on variable-bit-rate (VBR) video codecs which produce an interframe discrete cosine transform/differential pulse code modulation (DCT/DPCM) codec output format compatible with the evolving CCITT H.261 standard for px64 kb/s motion video. Transport-level protocol functions (such as delay compensation, flow control, and error control) required to support real-time video at an acceptable quality level are identified and discussed. A simulation model used for assessing the performance of the LAN with several video and data users is described. The model provides quantitative measures of network performance (such as packet loss or delay vs. throughput). Preliminary performance evaluation results demonstrate that, with appropriate transport-level delay compensation, potentially acceptable video and data quality levels can be provided on a well-loaded (~55%) CSMA/CD LAN. With appropriate transport buffering, acceptably low video packet loss rates can be achieved, although the corresponding subjective quality has yet to be established