FEC and priority for VBR video distribution over ATM

Video services promise to become a major traffic component of future B-ISDN networks. Proliferation of video services, particularly for home-entertainment purposes, may involve the use of variable-bit-rate (VBR) video compression. Asynchronous transfer mode (ATM) technology will be the means of handling the switching and multiplexing problems that will arise, but it involves the risk of cell losses due to buffer overflow. This paper assumes the use of a VBR source encoding scheme which achieves a modest level of compression, so as to make a low-cost home decoder feasible, and generates data of two levels of value with respect to the reconstruction process. The use of forward error correcting (FEC) codes has been proposed previously to reconstruct lost cells containing high-value video data. The paper focuses on the final ATM link to the home and compares the efficacy of FEC with simple priority treatment of high-value cells with respect to cell-discard in the ATM multiplexer. It is shown that priority is preferable to FEC with regard to quality, traffic handling capacity and simplicity, but requires longer buffers for the same rate of cell loss. Such buffers would increase the end-to-end delay of the video signals, presenting a potential problem for teleconference video applications, but the characteristic is not likely to be a problem for distribution applications.