METHOD OF CREATING AND UTILIZING DIVERSITY IN A MULTIPLE CARRIER COMMUNCIATION SYSTEM
First Claim
1. A method of operating a wireless terminal in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two different carrier signal including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, the method comprising:
- operating said wireless terminal to communicate with said base station using said first carrier signal over a period of time;
during said period of time, checking a plurality of said transmitted carrier signals to determine channel interference associated with each of said carrier signals; and
initiating an intercarrier handoff between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference.
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Accused Products
Abstract
In many cellular systems, reusing spectrum bandwidth, creates problems in boundary regions between the cells and sectors where the signal strength received from adjacent base stations or adjacent sector transmissions of a single base station may be nearly equivalent. The invention creates a new type of diversity, referred to as multiple carrier diversity by utilizing multiple carriers, assigning different power levels to each carrier frequency at each base station, and/or offsetting sector antennas. The cell and/or sector coverage areas can be set so as to minimize or eliminate overlap between cell and/or sector boundary regions of different carrier frequencies. Mobile nodes traveling throughout the system can exploit multiple carrier diversity by detecting carriers and selecting to use a non-boundary carrier based on other system criteria in order to improve performance. Boundary carriers may, but need not be, identified and excluded from consideration for use by a wireless terminal.
148 Citations
18 Claims
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1. A method of operating a wireless terminal in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two different carrier signal including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, the method comprising:
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operating said wireless terminal to communicate with said base station using said first carrier signal over a period of time; during said period of time, checking a plurality of said transmitted carrier signals to determine channel interference associated with each of said carrier signals; and initiating an intercarrier handoff between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference. - View Dependent Claims (2, 3, 4)
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5. A wireless terminal, comprising:
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receiver means for receiving carrier signals corresponding to at least two different available carrier frequencies transmitted by the same base station; carrier selection means for selecting which one of said different available carrier frequencies to use at any point in time for the receipt of information, said carrier frequency selecting means including; means for repeatedly checking, during an interval of time during which said wireless terminal has a reliable communications connection with said base station using a first one of the available carrier frequencies, which of the available carrier frequencies has better interference properties; and means for signaling the base station to initiate an intracell intercarrier handoff to change the carrier frequency used to communicate with the wireless terminal when one of the available carrier frequencies is determined to be better for communication of signals to said wireless terminal than the carrier frequency being used. - View Dependent Claims (6, 7, 8, 9)
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10. A wireless terminal, comprising:
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a receiver for receiving carrier signals corresponding to at least two different available carrier frequencies transmitted by the same base station; a carrier selection module for selecting which one of said different available carrier frequencies to use at any point in time for the receipt of information; a carrier strength measurement module for repeatedly checking, during an interval of time during which said wireless terminal has a reliable communications connection with said base station using a first one of the available carrier frequencies, which of the available carrier frequencies has better interference properties; and a transmitter for signaling the base station to initiate an intracell intercarrier handoff to change the carrier frequency used to communicate with the wireless terminal when one of the available carrier frequencies is determined to be better for communication of signals to said wireless terminal than the carrier frequency being used. - View Dependent Claims (11, 12)
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13. A device for use in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two different carrier signals including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, said device comprising:
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a processor configured to; control the device to communicate with said base station using said first carrier signal over a period of time; during said period of time, check a plurality of said transmitted carrier signals to determine channel interference associated with each of said carrier signals; and initiate an intercarrier handoff between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference. - View Dependent Claims (14, 15)
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16. A computer program product, comprising:
computer readable medium embodying computer executable instructions for controlling a wireless terminal in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two different carrier signals including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, the computer readable medium comprising; instructions for causing said wireless terminal to communicate with said base station using said first carrier signal over a period of time; instructions for causing said wireless terminal to check a plurality of said transmitted carrier signals, during said period of time, to determine channel interference associated with each of said carrier signals; and instructions for causing said wireless terminal to initiate an intercarrier handoff between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference. - View Dependent Claims (17, 18)
Specification