Patent ID: 7664069

Claim:
A system for preventing a call drop from occurring between a CDMA 2000 1xEV-DO (Evolution-Data Optimized) system and a hybrid access terminal in traffic with the CDMA 2000 1xEV-DO system, by limiting a predetermined search time for a 1X system, the system comprising: the hybrid access terminal operated in a 1X mode in relation to the 1X system for receiving a voice signal transmission service or a low-rate data transmission service from the 1X system and in a 1xEV-DO mode in relation to the 1xEV-DO system for receiving a high-rate data transmission service from the 1xEV-DO system, the hybrid access terminal in traffic with the 1xEV-DO system being periodically switched into the 1X mode so as to update overhead messages and being forced to return to the 1xEV-DO mode if the predetermined search time lapses; a base station transceiver subsystem including a 1xEV-DO access network transceiver for transmitting/receiving packet data to/from the hybrid access terminal and a 1X transceiver for transmitting/receiving voice or data to/from the hybrid access terminal; a base station controller including a 1xEV-DO access network controller for controlling a packet data transmission service of the 1xEV-DO access network transceiver and a 1X controller for controlling a transmission service of the 1X transceiver; and a packet data serving node (PDSN) connected to the 1xEV-DO access network controller so as to transmit/receive the packet data to/from the 1xEV-DO system, wherein a TDMA (time division multiple access) method is utilized in the case of a forward link transmitting data from the 1xEV-DO system to the hybrid access terminal, and a CDMA (code division multiple access) method is utilized in the case of a reverse link transmitting data from the hybrid access terminal to the 1xEV-DO system, and wherein a hard handoff is carried out in the case of the forward link by transmitting data with maximum power without performing power control, and a soft handoff is carried out in the case of the reverse link while performing the power control with respect to each hybrid access terminal.