Subjective Evaluation of Dedicated Multiple-Hop Satellite Communications for Government and Military Users

Acceptability of telephone communications over a circuit which included two synchronous orbit satellite links in tandem is the primary subject presented. Round trip delay in the order of 1100 ms was caused by such a circuit, and the question studied was this: wall this phenomenon cause actual users to rate the circuit unacceptable? The users consisted of military and civilian government personnel who were experienced in world-wide telephone communications over military networks. The statistics of almost 200 users revealed that with 99-percent certainty, less than 2 percent of the users will rate the circuit including two synchronous orbit satellite links in tandem unacceptable. The circuit used was equipped with Western Electric Company 3A echo suppressors at both ends. Tests were also performed with circuits including three and four synchronous orbit satellite links in tandem of which the third and fourth satellite links were provided by simulation circuitry. The results in these cases yielded a surprisingly small number of users who rated the circuit unacceptable. A definite change from the normal conversational mode to accomodate the delay accounts for this fact.