MULTICAST TRANSMISSION METHOD AND SYSTEM

摘要

The transmission system according to the invention can be used for reliably multicasting a group of data packets from a primary station ( 2 ) via a network ( 4 ), such as the Internet, to a plurality of secondary stations ( 6 ). The primary station ( 2 ) collects feedback information, which is related to a state of reception (L_i) of the group of data packets, from the secondary stations ( 6 ). In order to prevent an implosion of feedback information messages from congesting the network ( 4 ) the primary station ( 2 ) repeatedly transmits feedback requests, which comprise a reply probability value (p) and the worst state of reception (L_thresh) reported to the primary station ( 2 ) thus far, to the secondary stations ( 6 ). The secondary stations ( 6 ) transmit the feedback information to the primary station ( 2 ) in dependence on the reply probability value (p) and only when the state of reception (L_i) is worse than the worst state of reception reported thus far (L_thresh). The reply probability value (p) and the worst state of reception reported thus far (L_thresh) are adapted by the primary station ( 2 ) in dependence on the feedback information received so that a maximum number of feedback information messages are collected from the secondary stations ( 6 ) without congesting the network ( 4 ). If the state of reception (L_i) comprises the number of data packets erroneously received (L_i) by the secondary stations ( 6 ), the primary station ( 2 ) can transmit correction information based on this number of erroneously received data packets (L_i) and the group of data packets transmitted to the secondary stations ( 6 ) so that the secondary stations ( 6 ) can effectively correct the erroneously received data packets with the correction information.