Method and apparatus for performing soft hand-off in a wireless communication system
First Claim
1. A method for selecting base stations to communicate with a remote station comprising:
- computing a threshold value in accordance with a combination of measurements of signal energies from base stations capable of communicating with said remote station;
comparing a signal energy measurement of a first base station with said threshold value; and
selecting said first base station when said signal energy measurement of said first base station exceeds said threshold value;
wherein said combination of signal energy measurements from base stations capable of communicating with said remote station comprises the sum of pilot energy values of pilot with greater received energy than said first base station.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus for providing soft handoff in a mobile communication system. In current systems is that the members of active set are determined in accordance with comparisons of measured pilot energy with fixed thresholds. However, the value of providing a redundant communication link to a mobile station depends strongly on the energy of other signals being provided to the mobile station. In the present invention, the signal strengths of other base stations in communication with a mobile station are considered when determining whether adding a base to that set of base stations in communication with the remote station is of sufficient value to justify the impact on system capacity.
188 Citations
11 Claims
-
1. A method for selecting base stations to communicate with a remote station comprising:
-
computing a threshold value in accordance with a combination of measurements of signal energies from base stations capable of communicating with said remote station; comparing a signal energy measurement of a first base station with said threshold value; and selecting said first base station when said signal energy measurement of said first base station exceeds said threshold value; wherein said combination of signal energy measurements from base stations capable of communicating with said remote station comprises the sum of pilot energy values of pilot with greater received energy than said first base station. - View Dependent Claims (2)
-
-
3. In a wireless communications system wherein a first base station transmits a first pilot signal and a first traffic signal, and a second base station transmits a second pilot signal and a second traffic signal, and a remote station receives said first pilot signal and said first traffic signal, a method for determining whether to add a third base station to an Active Set of said remote station, comprising the steps of:
-
demodulating said first pilot signal; measuring the energy of said demodulated first pilot signal; generating a threshold in accordance with said demodulated first pilot signal energy; demodulating said second pilot signal; measuring the energy of said demodulated second pilot signal; comparing said demodulated second pilot signal energy with said threshold; adding said second base station to said Active Set when said demodulated second pilot signal energy exceeds said threshold; generating a revised threshold in accordance with a combination of said demodulated first pilot signal energy and said demodulated second pilot signal energy; demodulating a third pilot signal from said third base station; measuring the energy of said demodulated third pilot signal; comparing said demodulated third pilot signal energy with said revised threshold; and adding said third base station to said Active Set when said demodulated third pilot signal energy exceeds said revised threshold.
-
-
4. In a wireless communications system in which a plurality of base stations are in communication with a base station controller, a method for determining an Active Set of base stations to communicate with a remote station at said base station controller, comprising the steps of:
-
receiving a signal strength measurement message indicative of the signal strengths associated with each of said plurality of base stations as measured at said remote station; selecting a first base station as a member of said Active Set of base stations; calculating a threshold value in accordance with a signal strength of said selected first base station; selecting a second base station as a member of said Active Set of base stations in accordance with said threshold value; summing the signal strengths associated with each of said two selected base stations; determining a revised threshold value in accordance with said summed signal strengths; and determining remaining members of said Active Set in accordance with said revised threshold value. - View Dependent Claims (5)
-
-
6. A method for determining the base stations to transmit to a remote station at said remote station in which a plurality of base stations comprising an Active Set of base stations transmit to said remote station and wherein a second set of base stations which are not members of said Active Set comprise a Candidate Set of base stations, said method comprising the steps of:
-
aggregating signal energies of said Active Set of base stations; generating a threshold value in accordance with said aggregated signal energies of said base station members of said Active Set; comparing signal energy of a base station of said Candidate Set of base stations with said threshold; and adding said base station of said Candidate Set of base stations to said Active Set of base stations when said signal energy of a base station of said Candidate Set of base stations exceeds said threshold. - View Dependent Claims (7, 8, 9, 10, 11)
-
Specification