Seamless handoff system and method
First Claim
1. A method for a mobile subscriber to control cell handoff in a multicellular CDMA communication system while roving among individual cells, each cell associated with a base station which transmits a global pilot signal, where the subscriber has a preexisting communication link with one of the base stations, comprising the steps of:
- a) receiving a plurality of transmissions from a plurality of candidate base stations with which the preexisting link is not established;
b) selecting a received transmission associated with a candidate base station;
c) attempting to acquire a global pilot signal from said selected transmission;
d) if said global pilot cannot be acquired, selecting a received transmission associated with a different candidate base station;
e) repeating steps b-d until a global pilot associated with a selected candidate base station is received;
f) ramping transmitter power of the mobile subscriber while transmitting a short access code from the mobile subscriber to said selected candidate base station;
g) monitoring transmit power to said selected candidate base station;
h) detecting a return transmitted signal from said candidate base station;
i) comparing transmit power to said selected candidate base station with transmit power to the preexisting communication link;
j) if said transmit power to said selected candidate base station is equal to or greater than the transmit power of the preexisting communication link, repeat steps b-i, otherwise transmitting a long access pilot to said selected candidate base station and establishing a new communication link; and
k) abandoning the preexisting communication link.
1 Assignment
0 Petitions
Accused Products
Abstract
A multicellular communications system where transmission between a roving subscriber and multiple base station transceivers is maintained throughout the territory. Each mobile subscriber unit has global code seeds for the entire communications system or an updated neighbor list and continuously searches to access available cell base stations while maintaining a communication link with one base station. Candidate cell base stations are interrogated and communicated with. The candidate base station that requires less transmitting energy from the mobile subscriber unit is closely monitored. When the mobile subscriber unit can successfully communicate with less transmit power than currently required by the present base station, the mobile subscriber unit is handed off to the candidate base station transceiver.
45 Citations
10 Claims
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1. A method for a mobile subscriber to control cell handoff in a multicellular CDMA communication system while roving among individual cells, each cell associated with a base station which transmits a global pilot signal, where the subscriber has a preexisting communication link with one of the base stations, comprising the steps of:
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a) receiving a plurality of transmissions from a plurality of candidate base stations with which the preexisting link is not established; b) selecting a received transmission associated with a candidate base station; c) attempting to acquire a global pilot signal from said selected transmission; d) if said global pilot cannot be acquired, selecting a received transmission associated with a different candidate base station; e) repeating steps b-d until a global pilot associated with a selected candidate base station is received; f) ramping transmitter power of the mobile subscriber while transmitting a short access code from the mobile subscriber to said selected candidate base station; g) monitoring transmit power to said selected candidate base station; h) detecting a return transmitted signal from said candidate base station; i) comparing transmit power to said selected candidate base station with transmit power to the preexisting communication link; j) if said transmit power to said selected candidate base station is equal to or greater than the transmit power of the preexisting communication link, repeat steps b-i, otherwise transmitting a long access pilot to said selected candidate base station and establishing a new communication link; and k) abandoning the preexisting communication link. - View Dependent Claims (2, 3, 4, 5)
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6. A mobile subscriber system that controls cell hand-off in a multicellular CDMA communication system while roving among individual cells, each cell associated with a base station which transmits a global pilot signal, where the subscriber has a preexisting communication link with one of the base stations, comprising:
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means for receiving a plurality of transmissions from a plurality of candidate base stations with which the preexisting link is not established; means for selecting a received transmission associated with a candidate base station; means for attempting to acquire a global pilot signal from said selected transmission; means for selecting a received transmission associated with a different candidate base station if said global pilot cannot be acquired; means for ramping transmitter power of the mobile subscriber while transmitting a short access code from the mobile subscriber to said selected candidate base station; means for monitoring transmit power to said selected candidate base station; means for detecting a return transmitted signal from said candidate base station; means for comparing transmit power to said selected candidate base station with transmit power to the preexisting communication link; means for transmitting a long access pilot to said selected candidate base station and establishing a new communication link if said transmit power to said selected candidate base station is less than the transmit power of the preexisting communication link; and means for abandoning the preexisting communication link. - View Dependent Claims (7, 8, 9, 10)
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Specification