Performances of a Date Dissemination Code on Telephone Lines Using Commercial Modems

F. Cordara, V. Pettiti, R. Quasso, E. Rubiola

Abstract:	A coded time/date information dissemination system (CTD), based on telephone lines and commercial modems, is now in its experimental phase in Italy at IEN. This service, born from a cooperation with other metrological laboratories (TUG, Austria, SNT, Sweden, VSL, The Netherlands), represents an attempt towards an European standardization. This paper will give some results of an experimental analysis in which a few modems have been tested, both in laboratory conditions and connected to the telephone network, in order to evaluate the timing capability of the system. When the system is used in a one-way mode, in many practical cases the modems delay turns out to be the main factor which limits the accuracy, even more than the telephone line delays. If the two-way mode is wed, the modems asimmetry, i.e., the delay difference between transmission and reception, is almost always the most important source of uncertainty, provided the link is not including a space segment. Comparing the widely wed V.22 modems to the old V.21 ones, the [otters turn out to be better both in delay time (30-100 ms V.22, and 7-15 ms V.21) and asimmetry (10-50 us V.21, and 10 ms V.22). Time transfer accuracies of 10 us (same town) to 100 us (long distance calls) have been obtained in two-way mode with commercial V.21 modems.
Published in:	Proceedings of the 24th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 3, 1992 Ritz-Carlton Hotel McLean, Virginia
Pages:	243 - 254
Cite this article:	Cordara, F., Pettiti, V., Quasso, R., Rubiola, E., "Performances of a Date Dissemination Code on Telephone Lines Using Commercial Modems," Proceedings of the 24th Annual Precise Time and Time Interval Systems and Applications Meeting, McLean, Virginia, December 1992, pp. 243-254.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In