Impact of network transmission delay and echo on Group 3 facsimile performance

This paper provides information on a laboratory study conducted by COMSAT Laboratories to evaluate the effect of echo and delay on facsimile call retention rates. The term "call retention" is defined as the ability of a pair of facsimile terminals to maintain a circuit connection until all pages have been successfully transmitted after negotiation of the high speed signaling rate. The results of this study indicate that the effect of network echo has the potential of degrading facsimile call retention. In addition, propagation delay reduces retention rates even further. The results of this work are currently under consideration by the International Telecommunication Union (formerly CCITT) in the formulation of test methodologies for assessing facsimile terminal implementation performance.