Method for tracking the size of a multicast audience

A method of estimating the size of a multicast audience comprising:

• (a) transmitting to receivers receiving the multicast a plurality of requests each including a probability parameter (P), whereby each terminal replies or not with a corresponding probability;
• (b) counting the number (r) of replies to each request;
• (c) determining, from the counts and parameters, estimates of the number of receivers;
• (d) filtering the estimates;
• wherein the method further includes repeatedly computing a new probability parameter to be included in a subsequent step (a), by forecasting, from the counts and parameters, a upper bound for the number of receivers and determining therefrom the new probability parameter.

A method of estimating the size of a multicast audience comprising:

• (a) transmitting to receivers receiving the multicast a plurality of requests each including a probability parameter (P), whereby each terminal replies or not with a corresponding probability;
• (b) counting the number (r) of replies to each request;
• (c) determining, from the counts and parameters, estimates of the number of receivers;
• (d) filtering the estimates;
• including adaptively adjusting the parameters of said filtering of the estimates as a function of the power spectrum of past values of the estimates.