Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-05-28
2001-11-27
Vo, Nguyen T. (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S553100, C455S069000
Reexamination Certificate
active
06324408
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to mobile stations for use in both public and private wireless systems and, more particularly, to a power level control in a mobile station.
BACKGROUND OF THE INVENTION
A wireless communication system, in the form of a cellular system, is designed to cover a large geographic area. The system is divided into numerous cells providing air interface between mobile stations and land-based systems, such as the public land mobile network (PLMN). Recently, cellular based system design is used as a foundation for smaller, private systems, such as wireless office systems (WOS). These private systems may share the spectrum with the public cellular systems. Being smaller in scale than a public cellular system, a private cellular system is intended to operate at lower power levels.
Mobile stations are conventionally designed to adjust mobile station power level to keep the mobile transmitting at a high enough power level to minimize bit errors in the uplink direction. The balancing objective is to keep the mobile transit power low enough to minimize interference to other systems, and to extend the battery life of the mobile. In the public cellular systems the power level is controlled by commands in a digital control channel (DCCH). In wireless office systems the power level is set in control message commands sent to the mobile station. In either case the appropriate power level is determined by the wireless system and the mobile station controls its transmitter responsive to such commands. The power level used for private wireless systems is substantially lower than that used for public wireless systems. In fact the transmit power level in public wireless systems may be on the order of 100 mWatts, while for a WOS on the order of 1 mWatt.
The lower power level used for private wireless systems is an appealing feature for environments such as hospitals where any type of traditional cellular communications is strictly banned. The reasons for the ban include possible interference with hospital equipment such as heart monitors due to the high power level emitted from traditional public cellular system mobile stations.
As long as a private wireless system is operating normally, the power level from a mobile station will stay at low power level for office use. However, if the private wireless system experiences problems, there are possible failure situations where the mobile system will operate in the public network, and thus at higher power level, even if located within the area of the private wireless system. This can cause problems in sensitive environments, such as a hospital. One solution to this problem is to manufacture a mobile station that can only be used at a low power level, such as for hospital environments. The power level is then limited to never reach above the power level allowed in a hospital environment. However, this requires that a special mobile station be manufactured just for hospital use, resulting in a higher manufacturing costs. Administration costs would increase due to handling of non-standard phones. Further, the mobile station could never be used in a PLMN environment. Finally, one of the main features of wireless office system phones is the ability to use the phone both in the PLMN and the private wireless office environment, which would be removed.
The present invention is directed to overcoming one or more of the problems discussed above in a novel and simple manner.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a power control for use in sensitive environments for private wireless systems.
Broadly, there is disclosed herein, a mobile station for use in wireless systems. The mobile station includes a transmitter for broadcasting radio signals to a wireless system in which the mobile station is communicating. A control is operatively associated with the transmitter for controlling mobile station transmit power in a normal mode or a safe mode, the normal mode transmitting at a select power level responsive to a command received from the wireless system. The safe mode includes programmable limit means for selectively limiting the mobile station to transmit at a relatively low power level in the wireless system.
More particularly, there is disclosed herein a mobile station adapted for use in both public and private wireless systems. The control includes a transmitter for broadcasting radio signals to one of the wireless systems. A control is operatively associated with the transmitter for controlling mobile station transmit power to normally transmit at a relatively high power level when the mobile station is communicating in the public wireless system and at a relatively low power level when the mobile station is communicating in the private wireless system, responsive to commands received from the wireless system in which the mobile station is communicating. Programmable limit means are operatively associated with the control for selectively controlling the mobile station to operate in a normal mode or safe mode, the safe mode limiting the mobile station to communicating at the relatively low power level in either wireless system.
It is a feature of the invention that the mobile station includes a keypad and the mode is selected by entering a passcode using the keypad. The programmable limit means compares the entered passcode to a mode passcode stored in a memory.
It is another feature of the invention that the mobile station includes a display for displaying an indication if the programmable limit means it is in the safe mode.
It is a further feature of the invention that the programmable limit means is programmable to permit the mobile station to communicate at the relatively high power level in the safe mode in response to a user entering a power level passcode. The mobile station includes a keypad and the power level passcode is entered using the keypad. The programmable limit means compares the entered power level passcode to a power passcode stored in a memory. The mobile station includes a display for displaying an indication that the mobile station is communicating at the relatively high power level in the safe mode.
In accordance with one aspect of the invention, the programmable limit means is programmed to prevent communicating at the relatively high power level if the mobile station is communicating in the private wireless system.
In accordance with another aspect of the invention, the programmable limit means is programmed to automatically return to communicating at the limited relatively low power level if the mobile station enters the private wireless system while communicating at the relatively high power level.
It is disclosed in accordance with a further aspect of the invention the method of controlling power level in a mobile station adapted for use in plural wireless systems. The method comprises the steps of providing a transmitter for broadcasting radio signals to one of the wireless system; controlling the transmitter to normally transmit at a power level responsive to commands received from the one wireless system, the commands normally requiring the transmitter to transmit at a relatively high power level when the mobile station is communicating in public wireless systems and at a relatively low power level when the mobile station is communicating in private wireless systems; and selectively controlling the mobile station to operate in a normal mode or a safe mode, the safe mode limiting the mobile station to communicating at the relatively low power level in any of the wireless systems.
Further features and advantages of the invention will be readily apparent from the specification and from the drawing.
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Vo Nguyen T.
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