Issue No. 03 - May/June (2002 vol. 6)
<p>Delay, echo, codec type, and packet loss all come into play in achieving the quality of PSTN calls in packet-based telephony.</p>
J. Janssen, D. De Vleeschauwer, M. Büchli and G. H. Petit, "Assessing Voice Quality in Packet-Based Telephony," in IEEE Internet Computing, vol. 6, no. , pp. 48-57, 2002.