Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-10-26
2001-11-20
Trost, William (Department: 2683)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S552100, C455S432300
Reexamination Certificate
active
06321097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dual mode cellular phone and, in particular, to a method for automatically switching a dual mode cellular phone to a digital or analog mode when a user is mobile.
2. Description of the Related Art
A dual mode cellular phone is compatible with both a digital Code Division Multiple Access (CDMA) communication system and an analog Advanced Mobile Phone Service (AMPS) communication system. This dual mode cellular phone is tuned to the digital communication system in a common service area where the digital and analog base stations are both installed, and to the analog communication system in an analog service area where only the analog base station is installed.
When the dual mode cellular phone is set to a digital preference mode, it is tuned to the digital base station in the common service area. However, in the analog service area, upon power-up, the dual mode cellular phone first attempts to search for the digital base station. If the search fails, then the dual mode cellular phone searches for the analog base station. Subsequently, the dual mode cellular phone is tuned to the analog base station, allowing the user to talk over the phone.
When the user terminates the call upon completion of the telephone conversation, the dual mode cellular phone again searches for the digital base station for a specified time (e.g., approximately 60 seconds). Similarly, even when the user terminates an incoming call after completion of the conversation, the dual mode cellular phone searches for the digital base station for the specified time. Further, even when the dual mode cellular phone is set to an analog mode, it searches for the digital base station in an idle state at specified time intervals (e.g., 3 minutes).
Searching for the digital base station disadvantageously causes the dual mode cellular phone to consume twice the amount of operating current as that consumed in the idle state. Further, and perhaps even more disadvantageous, the dual mode cellular phone cannot receive an incoming call during the search for the digital base station. Accordingly, the dual mode cellular phone may have a reduced call reception ratio and a reduced battery run-time.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for automatically switching a dual mode cellular phone to an analog or digital mode according to a change of the service area in order to increase the call reception ratio and reduce battery consumption.
It is another object of the present invention to provide a method for reducing the frequency of searching for a digital base station in an analog service area in order to reduce battery consumption and increase the call reception ratio.
To achieve the above and other objects, there is provided a method for automatically switching to a digital or analog mode in a dual mode cellular phone. The method includes the steps of: checking whether or not the phone is set to a digital preference mode, upon power-on; checking whether or not a digital signal is received from a base station and setting the phone to the digital mode upon receipt of the digital signal, when the phone is set to the digital preference mode; setting the phone to the analog mode, when the phone is not set to the digital preference mode or the digital signal is not received from the base station; and returning to the step of checking whether or not the digital signal is received, when a call end key of the phone is not depressed or a call release message is not received from the base station.
Further, the dual mode cellular phone returns to the step of checking whether or not the digital signal is received, when the phone is set to the analog mode, a call attempt has failed, and the phone is set to a redial-on mode wherein an unsuccessful predetermined number of redials have been performed or a redial-off mode.
Moreover, the dual mode cellular phone returns to the step of checking whether or not the digital signal is received, when the phone is set to the analog mode, a registration attempt has been successfully performed in an access state, and a predetermined time interval has elapsed with respect to the phone having entered an idle state.
Additionally, the dual mode cellular phone returns to the step of checking whether or not the digital signal is received, when the phone is set to the analog mode and receives an analog signal with a low power or loses a word synchronization signal.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings, where the same reference numerals are used to represent the same functional elements.
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Dilworth & Barrese LLP
Gesesse Tilahun
Samsung Electronics Co,. Ltd.
Trost William
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