Method for multi-mode handoff using preliminary time alignment of a mobile station operating in analog mode
First Claim
1. In a multi-channel communication system in which a mobile station is designed for communication with one or more base stations over analog and digital communication channels using analog and digitally modulated communication signals, respectively, a method for maintaining a connection initiated on the analog communication channel comprising the steps of:
- time aligning said mobile station to a predetermined system time of said base station;
identifying an available digital communication channel; and
transmitting to said mobile station over said analog communication channel a handoff message and performing handoff of the connection to the available digital communication channel.
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Accused Products
Abstract
A method for handoff of an analog connection within a cellular communication system which relies upon mobile station synchronization to a system time is disclosed herein. In order to reduce the acquisition time for a mobile station commencing operation in a digital mode, an estimate of master system time is transferred to the mobile station in analog mode before entering digital mode. The alignment operates within the protocols of existing analog systems, and hence requires only minimal changes in the mobile station. Time alignment may be initiated upon the base station sending to the mobile station a command to continually transmit a periodic signaling tone. The base station compares the phase of the signaling tone from the mobile station to a master system clock and determines an error signal. The base station notifies the mobile station to delay or advance in time the transmitted signaling tones based on the error signal. This procedure may continue until the calculated error falls below a predetermined level. Having attained time alignment, the base station is able to transfer to the mobile station absolute time of day information with increased accuracy. The mobile station is then commanded into digital mode where transition time is reduced to a level tolerable by the end user due to the performed alignment.
207 Citations
23 Claims
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1. In a multi-channel communication system in which a mobile station is designed for communication with one or more base stations over analog and digital communication channels using analog and digitally modulated communication signals, respectively, a method for maintaining a connection initiated on the analog communication channel comprising the steps of:
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time aligning said mobile station to a predetermined system time of said base station; identifying an available digital communication channel; and transmitting to said mobile station over said analog communication channel a handoff message and performing handoff of the connection to the available digital communication channel. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In a code division multiple access (CDMA) spread spectrum communication system in which a mobile station is designed for communication with a base station over a digital communication channel using spread spectrum communication signals and over an analog communication channel using analog communication signals, a method for directing communications between said mobile station and said base station comprising the steps of:
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time aligning said mobile station to a predetermined system time of said base station during communication between said mobile station and said base station over said analog communication channel; and transmitting from said base station to said mobile station over said analog communication channel a handoff message identifying an available CDMA communication channel, and establishing communication between the mobile and base stations over the available CDMA communication channel. - View Dependent Claims (9, 10)
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11. In a multi-channel communication system in which a mobile station is designed for communication over an analog communication channel with a first base station using analog modulated communication signals, and for communication over a digital communication channel with a second base station using digitally modulated communication signals, a method for transferring a connection initiated on the analog communication channel to the digital communication channel comprising the steps of:
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time aligning said mobile station to a predetermined system time, said predetermined system time being provided to said mobile station by a system controller over said analog communication channel via said first base station; and transmitting from said first base station to said mobile station over said analog communication channel a handoff message and performing handoff to the digital communication channel associated with said second base station. - View Dependent Claims (12, 13, 14, 15)
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16. In a multi-channel communication system in which a mobile station is designed for communication with one or more base stations over analog and code division multiple access (CDMA) communication channels using analog and spread spectrum communication signals, respectively, wherein each base station transmits a common pilot signal of a different code phase with respect to other base stations in said system, a method for directing communications between said mobile station and said base stations comprising the steps of:
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identifying base stations within the vicinity of said mobile station at which usable signal transmissions from said mobile station are received; time aligning said mobile station to a predetermined system time during communication between said mobile station and a first of said base stations over said analog communication channel; and transmitting from said first base station to said mobile station over said analog communication channel a handoff message identifying an available CDMA communication channel, and establishing communication between the mobile station and a second base station over the available CDMA communication channel. - View Dependent Claims (17)
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18. In a multi-channel communication system in which a mobile station is designed for communication with one or more base stations over analog and digital communication channels using analog and digitally modulated communication signals, respectively, a system for maintaining a connection initiated on the analog communication channel comprising:
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a time alignment network, at least partially disposed within a first of said base stations in communication with said mobile station over said analog communication channel, for time aligning said mobile station to a predetermined system time; a system controller for identifying an available digital communication channel within said communication system; and a first base station transmitter for transmitting to said mobile station over said analog communication channel a handoff message and performing handoff of the connection to the available digital communication channel. - View Dependent Claims (19, 20, 21)
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22. In a code division multiple access (CDMA) spread spectrum communication system in which a mobile station is designed for communication with a base station over a digital communication channel using spread spectrum communication signals and over an analog communication channel using analog communication signals, a system for directing communications between said mobile station and said base station comprising:
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a time alignment network of said base station for time aligning said mobile station to a predetermined system time during communication between said mobile station and said base station over said analog communication channel; and a base station transmitter for transmitting from said base station to said mobile station over said analog communication channel a handoff message identifying an available CDMA communication channel wherein communication is subsequently established between the mobile and base stations over the available CDMA communication channel. - View Dependent Claims (23)
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Specification