The Effects of Transmission Delay in Four-Wire Teleconferencing

Two technological developments have recently entered the field of international communication. The first is the advent of the communi* This paper is drawn from the author's thesis which has been accepted by the University of Pennsylvania in partial fulfillment of the requirements for the degree of Master of Science. 1673 Hi80 TIIE BELL SYSTEM TECHNICAL JOURNAL, DECEMBER 1966 cation satellite. The second is the now widespread ability to establish teleconferences (telephone conference calls).* Relatively little is directly known about either of these by itself, let alone how they may interact. This paper represents an attempt to systematically experiment with time-delayed communication in the context of conference telephony. The research examines the influence of the delay factor upon human teleconferencing performance on a given task and also explores the development of group structure in a network having several time delays. In the present connection, the significant factor resulting from the use of a satellite is the relatively large amount of time delay introduced into the signal transmission. Riesz and Klemmer 1 , in a study of delayed conversation between two people, found that round-trip delays less than 600-milliseconds do not degrade the acceptability of the circuit. Mitchell- and Emling and Mitchell 3 have given the significant parameters of time delay for various types of satellites. Low orbit satellites (with a typical round-trip time delay of 100 milliseconds) and medium orbit satellites (with 190 milliseconds) should cause little trouble because of time delay.