Matched filter-based handoff method and apparatus
First Claim
1. In a spread-spectrum-communications system having a plurality of base stations and a remote unit, with the remote unit communicating with a first base station using spread-spectrum modulation, with the remote unit having a matched filter for despreading a first received-spread-spectrum signal transmitted from the first base station, and with the remote unit transmitting data to the first base station at a first data rate and a first power level, a method comprising the steps of:
- monitoring, at the output of said matched filter, a first signal quality of the first received-spread-spectrum signal;
scanning, at said remote unit, a plurality of received-spread-spectrum signals radiated from the plurality of base stations, respectively;
storing, at said remote unit, a plurality of signal qualities for the plurality of received-spread-spectrum signals, respectively;
selecting, from the plurality of received-spread-spectrum signals, at said remote unit, using the plurality of signal qualities from the plurality of received-spread-spectrum signals, a second received-spread-spectrum signal having a second signal quality transmitted from a second base station;
determining when the first signal quality falls below any of a predetermined handoff threshold and the second signal quality;
initiating, from said remote unit, upon the first signal quality falling below any of the predetermined handoff threshold and the second signal quality, handoff to the second base station;
queuing, upon requesting handoff to the second base station, data for transmission at said remote unit;
storing the queued data;
synchronizing, at said remote unit, to the second received-spread-spectrum signal and handing off from said first base station to said second base station; and
transmitting, from said remote unit to said second base station, the stored data at a second data rate and a second power level, with the second data rate greater than the first data rate, and with the second power level greater than the first power level, thereby transferring the stored data to said second base station.
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Accused Products
Abstract
In a cellular spread-spectrum communications network, a system and method for handing off a remote unit from a first base station to a second base station without loss of data. The remote unit receives a first spread-spectrum signal having a first signal quality from the first base station and transmits data to the first base station at a first data rate and a first power level. Responsive to monitoring the first signal quality and comparing the first signal quality to a plurality of signal qualities of a respective plurality of received-spread-spectrum signals, the remote unit initiates handoff when any of a number of predetermined criteria are met. Upon initiating handoff to the second base station, the remote unit stores the data that would otherwise have been transmitted. Once handoff is complete, the remote unit transmits the stored data to the second base station at a second data rate and a second power level, with the second data rate greater than the first data rate and the second power level greater than the first power level. Once the stored data has been transmitted, the remote unit transmits data to the second base station at a data rate and power level comparable to the first data rate and the first power level.
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Citations
15 Claims
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1. In a spread-spectrum-communications system having a plurality of base stations and a remote unit, with the remote unit communicating with a first base station using spread-spectrum modulation, with the remote unit having a matched filter for despreading a first received-spread-spectrum signal transmitted from the first base station, and with the remote unit transmitting data to the first base station at a first data rate and a first power level, a method comprising the steps of:
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monitoring, at the output of said matched filter, a first signal quality of the first received-spread-spectrum signal; scanning, at said remote unit, a plurality of received-spread-spectrum signals radiated from the plurality of base stations, respectively; storing, at said remote unit, a plurality of signal qualities for the plurality of received-spread-spectrum signals, respectively; selecting, from the plurality of received-spread-spectrum signals, at said remote unit, using the plurality of signal qualities from the plurality of received-spread-spectrum signals, a second received-spread-spectrum signal having a second signal quality transmitted from a second base station; determining when the first signal quality falls below any of a predetermined handoff threshold and the second signal quality; initiating, from said remote unit, upon the first signal quality falling below any of the predetermined handoff threshold and the second signal quality, handoff to the second base station; queuing, upon requesting handoff to the second base station, data for transmission at said remote unit; storing the queued data; synchronizing, at said remote unit, to the second received-spread-spectrum signal and handing off from said first base station to said second base station; and transmitting, from said remote unit to said second base station, the stored data at a second data rate and a second power level, with the second data rate greater than the first data rate, and with the second power level greater than the first power level, thereby transferring the stored data to said second base station. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a spread-spectrum-communications network having a central control unit, a plurality of base stations and a remote unit, with the remote unit transmitting data to a first base station of said plurality of base stations at a first data rate and a first power level, a system for handing off from the first base station to a second base station, through the central control unit, without data loss, the system comprising:
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transmitting means, located at the remote unit, for transmitting data from the remote unit to the first base station at a first data rate and a first power level; receiving means, located at the remote unit, for receiving a plurality of received-spread-spectrum signals radiated from the plurality of base stations, said receiving means including matched means for despreading a first received-spread-spectrum signal; monitoring means for monitoring, at the output of said matched means, a first signal quality of the first received-spread-spectrum signal; first memory means, coupled to said receiving means, for storing a plurality of signal qualities for the plurality of received-spread-spectrum signals, respectively; selecting means, coupled to said first memory means, for selecting, from the plurality of received-spread-spectrum signals using the plurality of signal qualities stored in said first memory means, a second received-spread-spectrum signal having a second signal quality transmitted from a second base station of said plurality of base stations; comparison means, coupled to said monitoring means and to said selecting means, for comparing the first signal quality to at least one of a predetermined threshold and the second signal quality; processor means, coupled to said comparison means, responsive to the first signal quality falling below any of the predetermined threshold and the second signal quality, for initiating handoff to the second base station and for queuing data for transmission; second memory means, coupled to said processor means, responsive to handoff initiation, for storing the data queued for transmission; said processor means for completing handoff to said second base station and for setting said matched means to despread the second received-spread-spectrum signal; and said transmitting means, responsive to handoff completion, for transmitting to said second base station the stored data at a second data rate and a second power level, with the second data rate greater than the first data rate, and with the second power level greater than the first power level, thereby transferring the stored data to the second base station. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. In a spread-spectrum-communications network having a central control unit, a plurality of base stations and a remote unit, with the remote unit transmitting data to a first base station of said plurality of base stations at a first data rate and a first power level, a system for handing off from the first base station to a second base station, through the central control unit, without data loss, the system comprising:
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a transmitter, located at the remote unit, for transmitting data from the remote unit to the first base station at a first data rate and a first power level; a receiver, located the remote unit, for receiving a plurality of received-spread-spectrum signals radiated from the plurality of base stations, said receiver including a matched filter for despreading a first received-spread-spectrum signal; a code generator, coupled to said receiver, for setting a chip-code of said matched filter; a monitoring device for monitoring, at the output of said receiver, a first signal quality of the first received-spread-spectrum signal; a first memory, coupled to said receiver, for storing a plurality of signal qualities for the plurality of received-spread-spectrum signals, respectively; a decision device, coupled to said first memory, for selecting, from the plurality of received-spread-spectrum signals using the plurality of signal qualities stored in said first memory, a second received-spread-spectrum signal having a second signal quality transmitted from a second base station of said plurality of base stations; a comparator, coupled to said monitoring device and to said decision device, for comparing the first signal quality to at least one of a predetermined threshold and the second signal quality; a processor, coupled to said comparator and to said code generator, responsive to the first signal quality falling below any of the predetermined threshold and the second signal quality, for initiating handoff to the second base station and for queuing data for transmission; a second memory, coupled to said processor, responsive to handoff initiation, for storing the data queued for transmission; said processor for completing handoff to said second base station; said code generator, responsive to said processor, for changing a chip code of said matched filter to despread the second received-spread-spectrum signal; and said transmitter, responsive to handoff completion, for transmitting to said second base station the stored data at a second data rate and a second power level, with the second data rate greater than the first data rate, and with the second power level greater than the first power level, thereby transferring the stored data to the second base station.
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15. A cellular spread-spectrum-communications system for handing off between a plurality of base stations without data loss comprising:
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a central control unit; a first base station having a first base-transmitter for transmitting a first spread-spectrum signal; a second base station having a second base-transmitter for transmitting a second spread-spectrum signal; and a remote unit including, a transmitter for transmitting data from the remote unit to the first base station at a first data rate and a first power level; a receiver for receiving a plurality of spread spectrum signals radiated from the plurality of base stations, the plurality of spread-spectrum signals received including the first spread-spectrum signal; a matched filter, coupled to said receiver, for despreading the first received-spread-spectrum signal; a monitoring device for monitoring, at the output of said matched filter, a first signal quality of the first received-spread-spectrum signal; a first memory, coupled to said receiver, for storing a plurality of signal qualities for the plurality of received-spread-spectrum signals, respectively; a decision device, coupled to said first memory, for selecting, from the plurality of received-spread-spectrum signals using the plurality of signal qualities stored in said first memory, the second received-spread-spectrum signal having a second signal quality transmitted from the second base station; a comparator, coupled to said monitoring device and to said decision device, for comparing the first signal quality to at least one of a predetermined threshold and the second signal quality; a processor, coupled to said comparator, responsive to the first signal quality falling below any of the predetermined threshold and the second signal quality, for initiating handoff to the second base station and for queuing data for transmission; a second memory, coupled to said processor, responsive to handoff initiation, for storing the data queued for transmission; said processor for completing handoff to said second base station and for changing a chip code of said matched filter to despread the second received-spread-spectrum signal; and said transmitter, responsive to handoff completion, for transmitting to said second base station the stored data at a second data rate and a second power level, with the second data rate greater than the first data rate, and with the second power level greater than the first power level, thereby transferring the stored data to the second base station.
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Specification