Handover method for minimizing packet call reconnection delay time between different mobile communication schemes and multi-mode terminal for the same

Abstract

A multi-mode terminal having first and second modems supporting different communication services and method for performing a handover thereof are provided. The method includes receiving, by the first modem, a message including starting condition for handover to a second communication network, wherein the condition is defined by a first communication network; determining, by the first modem, whether the starting condition for handover in the received message is satisfied; if the starting condition for handover in the received message is satisfied, receiving by the second modem, a command from the first modem to handover to the second communication network; and registering, by the second modem, into the second communication network in response to the command of the first modem, and connecting to the second communication network to perform communication.

What is claimed is: 
     
         1 . A method of handover for a multi-mode terminal having first and second modems supporting different communication services, the method comprising the steps of:
 receiving, by the first modem, a message including starting condition for handover to a second communication network, wherein the condition is defined by a first communication network;   determining, by the first modem, whether the starting condition for handover in the received message is satisfied;   if the starting condition for handover in the received message is satisfied, receiving by the second modem, a command from the first modem to handover to the second communication network; and   registering, by the second modem, into the second communication network in response to the command of the first modem, and connecting to the second communication network to perform communication,   wherein the first modem determines whether a measurement control message comprising a measurement report condition is received from the first communication network, monitors whether a state of the communication service through the first communication network satisfies the measurement report condition contained in the measurement control message, and transmits a measurement report message to the first communication network if the measurement report condition is satisfied.   
     
     
         2 . The method of  claim 1 , wherein registering, by the second modem, into the second communication network, comprises:
 turning on the second modem through a communication path connecting between the first and second modems;   determining whether a registration process between the second modem and the second communication network succeeds while maintaining communication with the first communication network;   if the registration process succeeds, disconnecting the communication with the first communication network; and   if the communication with the first communication network is disconnected, the second modem performing a communication to the second communication network.   
     
     
         3 . The method of  claim 1 , wherein the first communication network is a wideband code division multiple access (WCDMA) network, and the second communication network is a CDMA network, and the first modem and the second modem process signals transmitted or received through the WCDMA network and the CDMA network, respectively. 
     
     
         4 . The method of  claim 1 , wherein the first communication network is a WCDMA network and the second communication network is a global systems for mobile communication (GSM) network, and the first modem and the second modem process signals transmitted or received through the WCDMA network and the GSM network, respectively. 
     
     
         5 . The method of  claim 1 , wherein the message including starting condition for handover is contained in a measurement control message received from the first communication network. 
     
     
         6 . The method of  claim 1 , further comprising transmitting a measurement report message to the first communication network for informing that communication state is a state where the handover to the second communication network must be performed if the handover start condition is satisfied. 
     
     
         7 . The method of  claim 6 , further comprising:
 receiving a handover command from a UTRAN (Universal Mobile Telecommunications System Radio Access Network) in response to the measurement report message; and   if the handover command from the UTRAN is received, reconnecting communication to the second communication network to perform communication.   
     
     
         8 . The method of  claim 5 , wherein whether the starting condition for handover of the received message is satisfied comprises:
 receiving a measurement control message from the first communication network;   monitoring based on a starting condition for handover contained in the measurement control message whether the multi-mode terminal is located in a boundary area; and   if the multi-mode terminal is located in a boundary area, transmitting a measurement report message to the first communication network in response to the measurement control message.   
     
     
         9 . The method of  claim 2 , wherein determining whether the registration process between the second modem and the second communication network succeeds, comprises:
 the first modem turning on the second modem through the communication path connected between the first and second modem;   the second modem, which is turned on, registering in the second communication network; and   if the registration in the second communication network succeeds, the first modem receiving from the second modem a message for informing of the success of the registration.   
     
     
         10 . The method of  claim 3 , wherein performing the communication, comprises:
 if a message for informing of success of registration in the second communication network is received from the second modem, requesting for disconnect to the first communication network;   if an accept message responding to the request is received, disconnecting from the first communication network and transmitting a origination message to the second modem through the communication path;   commanding the second modem to request the second communication network for a connection; and   establishing a communication type path between the second modem and the second communication network to perform the communication service through the second communication network.   
     
     
         11 . A multi-mode terminal, having first and second modems supporting different communication services, comprising:
 the first modem for receiving from a first communication network a message including starting condition for handover to a second communication network, determining whether the starting condition for handover in the received message is satisfied through the first communication network, and transmitting, to the second modem, a command to handover to the second communication network if the starting condition for handover in the received message is satisfied; and   the second modem for receiving the command to handover to the second communication network, registering into the second communication network in response to the command of the first modem, and performing the communication to the second communication network,   wherein the first modem determines whether a measurement control message comprising a measurement report condition is received from the first communication network, monitors whether a state of the communication service through the first communication network satisfies the measurement report condition contained in the measurement control message, and transmits a measurement report message to the first communication network if the measurement report condition is satisfied.   
     
     
         12 . The multi-mode terminal of  claim 11 , wherein the first modem turns on the second modem through a communication path connected between the first and second modem if the starting condition for handover is satisfied, determines whether a registration process between the second modem and the second communication network succeeds while maintaining communication with the first communication network, disconnects the communication from the first communication network if the registration process succeeds, and allows the second modem to perform a communication to the second communication network if the communication with the first communication network is disconnected. 
     
     
         13 . The multi-mode terminal of  claim 11 , wherein the first communication network is a wideband code division multiple access (WCDMA) network and the second communication network is a CDMA network, and the first modem and the second modem process signals transmitted or received through the WCDMA network and the CDMA network, respectively. 
     
     
         14 . The multi-mode terminal of  claim 11 , wherein the first communication network is a WCDMA network and the second communication network is a global systems for mobile communication (GSM) network, and the first modem and the second modem process signals transmitted or received through the WCDMA network and the GSM network, respectively. 
     
     
         15 . The multi-mode terminal of  claim 11 , wherein the first modem monitors, based on the starting condition for handover contained in a measurement control message received from the first communication network, whether the multi-mode terminal is located in a boundary area, transmits a measurement report message to the first communication network in response to the measurement control message if the multi-mode terminal is located in a boundary area, and turns on the second modem if a handover command from a UTRAN (Universal Mobile Telecommunications System Radio Access Network) is received from the first communication network in response to the transmission of the measurement report message. 
     
     
         16 . The multi-mode terminal of  claim 15 , wherein the first modem turns on the second modem through the communication path connected between the first and second modems if the handover command from the UTRAN is received, and disconnects the packet call from the first communication network if a message for informing of success of registration in the second communication network is received from the second modem. 
     
     
         17 . The multi-mode terminal of  claim 12 , wherein the first modem requests the first communication network for a disconnect if a message for informing of the success of the registration in the second communication network is received from the second modem, disconnects the communication from the first communication network if an accept message responding to the request is received from the first communication network, and transmits a communication origination message to the second modem through the communication path. 
     
     
         18 . The multi-mode terminal of  claim 17 , wherein the second modem requests connection to the second communication network if the communication origination message is received and transmits to the first modem a message for informing of success of a connection with the second communication network in response to the request if the connection with the second communication network succeeds.