Patent ID: 8059572

Claim:
A method of transmitting and receiving multicast data in a network in which a multicast service is provided from a network entity and then transmitted to at least one mobile terminal, the method comprising the steps of: receiving a query message containing information on the multicast service from the network entity; receiving, from the mobile terminal, a request frame for requesting multicast data; in response to the request frame, transmitting to the network entity a report message allowing the mobile terminal to join the multicast service; receiving multicast data corresponding to the multicast service from the network entity and transmitting the received multicast data to the mobile terminal; determining, based on a group table provided on the network for managing the multicast service, the number of mobile terminals that have joined the multicast service; changing a multicast data transmitting and receiving mode of the multicast service according to the number of mobile terminals which have joined the multicast service; transmitting a keep-alive request to the mobile terminal for enabling the mobile terminal to enter a power savings mode; receiving a response to the keep-alive request before the mobile terminal enters the power saving mode, wherein the multicast data transmitting and receiving mode is one of a point-to-multipoint bearer mode and a point-to-point bearer mode, wherein the mobile terminal can simultaneously receive data via both the point-to-multipoint bearer mode and the point-to-point bearer mode, and wherein the mobile terminal is configured to be in an active state; and transmitting to the mobile terminal a request message for confirming whether the mobile terminal exists in the network, wherein the request message is transmitted through any one of a separate action frame, beacon, and piggybacked multicast data, and wherein the piggybacked multicast data is created by modifying a type and a subtype of a frame control field in a media access control (MAC) frame, or by setting a retry bit in the frame control field of the MAC frame.