Reliable multicast data retransmission method by grouping wireless terminals in wireless communication medium and apparatus for the same

A multicast data retransmission method used in a system that retransmits multicast packets by using a wireless terminal and an access point, the multicast data retransmission method comprising the steps of:

• (a) receiving from the access point information on a group which the wireless terminal belongs to;
• (b) if the wireless terminal is selected as a repeater that is to retransmit the multicast packets, receiving information from the access point about the order in which repeaters retransmit the multicast packets;
• and
• (c) receiving a retransmission command from the access point and retransmitting the multicast packets to other wireless terminals.

An apparatus for multicast data retransmission, the apparatus comprising:

• a grouping unit which groups wireless terminals based on distances between the wireless terminals and amplitudes of signals output from the wireless terminals;
• a repeater selecting and retransmission order arranging unit which selects the repeater to retransmit the multicast packets from each group, and arranges the order in which repeaters retransmit the multicast packets;
• a multicast packet train header creating unit which creates a multicast packet train header before the multicast packets are multicasted;
• a multicast packet train header transmitting unit which transmits the created multicast packet train header to all wireless terminals;
• and
• a retransmitting unit which retransmits the multicast packets in the order arranged by the repeater selecting and retransmission order arranging unit, after the multicast packet train header transmitting unit multicasts the multicast packet train header.

A structure of a multicast packet train header used in multicast data transmission, the structure of multicast packet train header comprising:

• multicast train ID information which is used to identify a multicast packet train;
• information about the number of groups of wireless terminals, the wireless terminals being connected to a wireless network and receiving the multicast packets;
• information about the number of multicast packet in each group which indicates the number of multicast packet in each group, the multicast packet being to be transmitted after the multicast packet train header is multicasted;
• and
• forward error correction information which is used to correct an error of the multicast packet train header.