Method and system for recognizing call switch-over from 1xEV-DO system to 1X system

A method for recognizing a call switch-over from a CDMA 2000 1xEV-DO system (1xEV-DO system) to a CDMA 2000 1X system (1X system) when a hybrid access terminal is switched from a 1xEV-DO mode to a 1X mode,

• wherein the 1X system comprises:
• a base station comprising
• a 1X transceiver for transmitting/receiving voice signals and/or low-rate data to/from the hybrid access terminal:
• a 1X controller for controlling the 1X transceiver;
• and
• a 1X mobile switching center for providing a communication access path of the 1X system for voice signals and/or low-rate data to/from the hybrid access terminal, storing information of the hybrid access terminal registered in the 1X mobile switching center in a home location register (HLR), and storing information of hybrid access terminals located in a region of the 1X mobile switching center;
• wherein the 1xEV-DO system comprises, in said base station;
• a 1xEV-DO access network transceiver subsystem for transmitting/receiving high-rate data to/from the hybrid access terminal;
• and
• a 1xEV-DO access network controller for controlling the 1X transceiver;
• the method comprising the steps of:
• allowing the hybrid access terminal to make a call-connection with the 1xEV-DO system in the 1xEV-DO mode and enter a 1xEV-DO traffic state, thereby enabling the hybrid access terminal to transmit/receive high-rate data;
• performing the call switch-over by switching the hybrid access terminal from the 1xEV-DO mode to the 1X mode in response to voice signals and/or low-rate data received from the 1X system at the hybrid access terminal while the hybrid access terminal is being in the 1xEV-DO traffic state;
• detecting, by the 1xEV-DO access network controller, a call drop between the hybrid access terminal and the 1xEV-DO system as a result of said switching the hybrid access terminal from the 1xEV-DO mode to the 1X mode;
• when the call drop is detected by the 1xEV-DO access network controller, transmitting, by the 1xEV-DO access network controller, a first message to the 1X mobile switching center to inquire whether or not voice signals or low-rate data are received in the hybrid access terminal;
• in response to the first message received at the 1X mobile switching center, sending, by the 1X mobile switching center, a second message to the 1xEV-DO access network controller to confirm that voice signals or low-rate data are received in the hybrid access terminal;
• recognizing, by the 1xEV-DO access network controller and based on the second message received at the 1xEV-DO access network controller, that the hybrid access terminal has been switched from the 1xEV-DO mode to the 1X mode;
• and
• storing, by the 1xEV-DO access network controller, the recognition information so that a user knows the reason for the call drop.