Communication device and data transfer method

A data transfer method of a communication device to transfer a received packet to a data terminal device, the communication device being coupled to the data terminal device in a wire or wireless system, the data transfer method comprising:

• determining whether or not a compression state of a compressed header added to the packet is Full Context indicating a maximum compressed state on a down link in which the packet is transferred from the communication device to the data terminal, by the communication device;
• transferring, to the down link, the packet to which the compressed header is added and transmitting an activation request signal used on case of activating a routing module using a robust header compression (RoHC) algorithm to the data terminal device including the routing module, when the compression state of the compressed header is the Full Context, by the communication device;
• decompressing the compressed header and transmitting the decompressed header to the data terminal device, when the compression state of the compressed header is not the Full Context, by the communication device;
• and
• activating the routing module using the RoHC algorithm and decompressing the compressed header transferred from the communication device, when the data terminal device receives the activation request signal, by the data terminal device.