Seamless soft handoff in a CDMA cellular communications system
First Claim
1. A method for mobile station processing of transmitted duplicate base station communications, each communication including a plurality of frames identified by frame sequence numbers, comprising the steps of:
- receiving the duplicate base station communications;
comparing frame sequence numbers for substantially simultaneously received frames within the received duplicate base station communications;
processing the substantially simultaneously received frames if the frame sequence numbers match; and
generating a signal for transmission from the mobile station to an origination source of the duplicate base station communications if the frame sequence numbers do not match, the signal identifying non-synchronous reception of the frames within the duplicate base station communications and requesting a timing adjustment be made to the duplicate base station communication transmissions to provide for substantially synchronous reception of frame sequence number matching frames within the received duplicate base station communications at the mobile station.
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Accused Products
Abstract
During a "make before you break" handoff performed within a CDMA communications system, duplicate downlink communications are generated and routed through different base stations for delivery to the mobile station. At the mobile station, the duplicate signals are received and the frame sequence numbers of the substantially simultaneously received frames therein are compared. If the sequence numbers do not match, the duplicate signals are identified as not being synchronously received by the mobile station. In response thereto, the mobile station signals the communications network on the uplink with a timing adjustment message, and appropriate timing modifications are made with respect to the transmission of the duplicate signals in order to provide for substantially synchronous reception. Diversity combination and decoding are then performed on the received signals. Alternatively, the mobile station buffers the earlier arriving signal and waits for the later arrival of the sequence number matching frame of the duplicate signal before engaging in diversity combining and decoding of the received signals.
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Citations
25 Claims
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1. A method for mobile station processing of transmitted duplicate base station communications, each communication including a plurality of frames identified by frame sequence numbers, comprising the steps of:
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receiving the duplicate base station communications; comparing frame sequence numbers for substantially simultaneously received frames within the received duplicate base station communications; processing the substantially simultaneously received frames if the frame sequence numbers match; and generating a signal for transmission from the mobile station to an origination source of the duplicate base station communications if the frame sequence numbers do not match, the signal identifying non-synchronous reception of the frames within the duplicate base station communications and requesting a timing adjustment be made to the duplicate base station communication transmissions to provide for substantially synchronous reception of frame sequence number matching frames within the received duplicate base station communications at the mobile station. - View Dependent Claims (2, 3, 4, 5)
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6. A method for mobile station processing of transmitted duplicate base station communications, each communication including a plurality of frames identified by frame sequence numbers, comprising the steps of:
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receiving the duplicate base station communications; comparing frame sequence numbers for substantially simultaneously received frames within the received duplicate base station communications; buffering frames of an earlier arriving one of the duplicate base station communications if the frame sequence numbers do not match; and processing the substantially simultaneously received frames if the frame sequence numbers match, or processing the buffered frames of the earlier arriving one of the duplicate base station communication with the frame sequence number matching frames of a later arriving one of the duplicate base station communications if the frame sequence numbers did not match. - View Dependent Claims (7, 8, 9, 10)
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11. A method for performing soft handoff within a communications system, comprising the steps of:
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engaging in a base station communication with a mobile station via first communications path associated with a first cell; detecting a need for a handoff of the communication from the first cell to a second cell; engaging in a duplicate base station communication with the mobile station via the first communications path and also via a second communications path associated with the second cell; receiving a message from the mobile station indicative of non substantially synchronous reception of individual frames within the duplicate base station communication whose frame sequence numbers match; and adjusting the timing of base station communications over the first and second communications paths to provide for substantially synchronous matching frame reception by the mobile station of the duplicate base station communication. - View Dependent Claims (12, 13, 14, 15)
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16. A mobile communications device, comprising:
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a first receiver for receiving a first communication transmitted from a first base station over a first communications path; a second receiver for receiving a second communication transmitted from a second base station over a second communications path, wherein the first and second communications comprise duplicate communications; a first decoder connected to the first receiver for extracting a frame sequence number from each frame within the first communication; a second decoder connected to the second receiver for extracting a frame sequence number from each frame within the second communication; a processor connected to the first and second decoders for comparing the extracted frame sequence numbers for substantially simultaneously received frames of the received duplicate communications, the processor generating a first signal if the frame sequence numbers match and a second signal if the frame sequence numbers do not match; means for combining and decoding the substantially simultaneously received frames in response to the first signal; and means for transmitting from the mobile station to an origination source of the duplicate communications in response to the second signal a request that a timing adjustment be made to the first and second base station duplicate communication transmissions over the first and second communications paths to provide for substantially synchronous reception by the mobile station first and second receivers of frame sequence number matching frames. - View Dependent Claims (17, 18, 19, 20)
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21. A mobile communications device, comprising:
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a first receiver for receiving a first communication transmitted from a first base station over a first communications path; a second receiver for receiving a second communication transmitted from a second base station over a second communications path, wherein the first and second communications comprise duplicate communications; a first decoder connected to the first receiver for extracting a frame sequence number from each frame within the first communication; a second decoder connected to the second receiver for extracting a frame sequence number from each frame within the second communication; a processor connected to the first and second decoders for comparing the extracted frame sequence numbers for substantially simultaneously received frames of the received duplicate communications, the processor generating a first signal if the frame sequence numbers match and a second signal if the frame sequence numbers do not match; means for buffering frames of an earlier arriving one of the duplicate communications in response to the second signal; means for combining and decoding the substantially simultaneously received frames in response to the first signal; and means for combining and decoding the buffered frames with the frame sequence number matching frames of a later arriving one of the duplicate communications in response to the second signal. - View Dependent Claims (22, 23, 24, 25)
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Specification