Inter-frequency handoff evaluation method
First Claim
1. A method of evaluating need for handoff of a mobile station in a wireless communication system from a base station operating at a first frequency (hereafter “
- f1 base station”
) to a base station operating at a second frequency (hereafter “
f2 base station”
), said method comprising the steps of;
evaluating a geographic positioning of said mobile station in respect to a signal coverage area of said f1 base station and a signal coverage area of said f2 base station;
computing an aggregate value of a set of pilot energy signals received at said mobile station;
obtaining a value of a pilot energy signal transmitted by said f2 base station and comparing it with said aggregate value; and
determining that a hand off of said base station connection should be made if said aggregate value is less than said f2 base station transmitted pilot energy signal value plus a preselected threshold value;
wherein said aggregate value is computed according to the equation;
where k=number of active set pilots.
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Accused Products
Abstract
An improved inter-frequency handoff trigger in a wireless communication system is disclosed. In an embodiment of the invention, a particular mobile station transmits a pilot strength measurement message to the base station. The base station subsequently determines the strongest border pilot and the strongest interior pilot. The base station evaluates whether the border sector is stronger than the interior sector. If the border sector is stronger than the interior sector, this would indicate that the mobile station is out of the coverage area of the interior pilot. The base station subsequently determines the transmitted pilot energy to total transmit power of the pilot signal associated with the border pilot. The transmitted pilot energy to total transmit power of the border pilot is then compared to an aggregate value of a set of pilot energy signals received at the mobile station and if the difference exceeds a threshold value, the handoff of the mobile station to the border sector base station is initiated.
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Citations
20 Claims
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1. A method of evaluating need for handoff of a mobile station in a wireless communication system from a base station operating at a first frequency (hereafter “
- f1 base station”
) to a base station operating at a second frequency (hereafter “
f2 base station”
), said method comprising the steps of;evaluating a geographic positioning of said mobile station in respect to a signal coverage area of said f1 base station and a signal coverage area of said f2 base station;
computing an aggregate value of a set of pilot energy signals received at said mobile station;
obtaining a value of a pilot energy signal transmitted by said f2 base station and comparing it with said aggregate value; and
determining that a hand off of said base station connection should be made if said aggregate value is less than said f2 base station transmitted pilot energy signal value plus a preselected threshold value;
wherein said aggregate value is computed according to the equation;
where k=number of active set pilots. - View Dependent Claims (2, 3, 4, 5, 6)
- f1 base station”
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7. In a wireless communication system having a plurality of base stations in communication with a mobile station at a first traffic channel, said mobile station receiving a plurality of active pilot signals, said active pilot signals including at least one border pilot signal and at least one interior pilot signal, a method of evaluating conditions for handoff of a connected call to a new traffic channel, said method comprising the steps of:
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determining a signal strength for a strongest border pilot signal at said mobile station and a signal strength for a strongest interior pilot signal at said mobile station and evaluating a difference between said determined signal strengths of said strongest border pilot signal and said strongest interior pilot signal against a first threshold;
determining transmitted pilot energy to total transmit power of said strongest border pilot signal and an aggregate value of all of said active pilot signals at said mobile station and evaluating a difference between said determined transmitted pilot energy to total transmit power and said aggregate value against a second threshold; and
making a handoff decision for said mobile station if said determined signal strength of said strongest border pilot signal is greater than said determined signal strength of said strongest interior pilot signal plus said first threshold, and if said transmitted pilot energy to total transmit power of said strongest border pilot signal is greater than said aggregate value plus said second threshold. - View Dependent Claims (8, 9, 10, 11, 12)
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13. In a wireless communication system having a plurality of base stations in communication with a mobile station at a first traffic channel, said mobile station receiving a plurality of active pilot signals, said active pilot signals including at least one border pilot signal and at least one interior pilot signal, a method of evaluating conditions for handoff of a connected call to a new traffic channel, said method comprising the steps of:
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adding a new border pilot signal to said plurality of active pilot signals;
determining a ratio of transmitted pilot energy to total transmit power of a strongest border pilot signal and an aggregate value of ratios of pilot energy to total received power of all of said active pilot signals at said mobile station and evaluating a difference between said determined transmitted pilot energy to total transmit power and said aggregate value against a threshold; and
making a handoff decision for said mobile station if transmitted pilot energy to total transmit power of said strongest border pilot signal is greater than said aggregate value plus said threshold. - View Dependent Claims (14, 15, 16, 17)
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18. In a wireless communication system having at least one base station in communication with a mobile station at a first frequency, said mobile station receiving a plurality of active pilot signals, said active pilot signals including at least one border pilot signal, a method for triggering handoff of a connected call to a new frequency, said method comprising the steps of:
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determining a ratio of transmitted pilot energy to total transmit power of a strongest border pilot signal and an aggregate value of ratios of pilot energy to total received power of all of said active pilot signals at said mobile station and evaluating a difference between said determined transmitted pilot energy to total transmit power and said aggregate value against a threshold; and
tuning said mobile station to said new frequency if a ratio of transmitted pilot energy to total transmit power of said strongest border pilot signal is greater than said aggregate value plus said threshold. - View Dependent Claims (19)
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20. A method of evaluating need for handoff of a mobile station in a wireless communication system from a base station operating at a first frequency (hereafter “
- f1 base station”
) to a base station operating at a second frequency (hereafter “
f2 base station”
), said method comprising the steps of;evaluating a geographic positioning of said mobile station in respect to a signal coverage area of said f1 base station and a signal coverage area of said f2 base station;
computing an aggregate value of a set of pilot energy signals received at said mobile station;
obtaining a value of a pilot energy signal transmitted by said f2 base station and comparing it with said aggregate value; and
determining that a hand off of said base station connection should be made if said aggregate value is less than said f2 base station transmitted pilot energy signal value plus a preselected threshold value;
wherein said step of evaluating a geographic positioning includes the substeps of;
determining a value of a first pilot energy signal received at said mobile station from said f1 base station and a value of a second pilot energy signal received at said mobile station from said f2 base station;
computing a difference between said second pilot energy signal value and said first pilot energy signal value; and
evaluating said difference against a preselected threshold value.
- f1 base station”
Specification