Buffer and Channel Sharing by Several InterframePicturephone® Coders

Simulations are described which test the feasibility of several conditional replenishment type Picturephone coders sharing the same transmission channel. Channel sharing takes advantage of the fact that many different users are rarely in rapid motion at the same time. Thus, when the data from several sources is averaged together prior to transmission, it is much more uniform than that from a single source. Since the peaks in the averaged data are smaller than with a single source, less buffering is required, and the channel rate required for transmission is much closer to the average data rate generated. Results indicate that by combining twelve sources prior to transmission, a 2:1 reduction in the bit rate of the system described by Candy, et al., 1 can be obtained. This means that twelve Picturephone sources could share a 12 megabits per second (one way) transmission facility.