Patent ID: 8155080

Claim:
A heterogeneous network system that performs a vertical handover between different networks in which a first network and a second network are coexisted based on a media independent handover, the heterogeneous network system comprising: a multi mode terminal for acquiring neighboring network information while performing wireless communication through the first network, generating a new address (NCoA) at a preliminary time of the vertical handover, requesting the second network for DAD (Duplicate Address Detection) of the new address, and transmitting BU (Binding Update) to activate the second network in response to a response to the DAD request, and performing wireless communication through the activated second network, wherein the preliminary time of vertical handover is a time at which a signal strength in the first network, on which the multi mode terminal currently performs wireless communication, is smaller than a predetermined signal strength; a media independent handover server for providing the neighboring network information in response to the BU request from the multi mode terminal at a predetermined cycle; and a home agent for performing a switchover from the first network to the second network according to the BU request from the multi mode terminal, and transmitting a switchover result to the multi mode terminal; wherein the multi mode terminal includes a MIH layer for transmitting an LGD (Link Going Down) message at the preliminary time of the vertical handover, and a MIH user layer for performing operations related to the generation of the new address, DAD, and BU in response to the LGD message.