Patent ID: 6049716
Filing Date: 2000-04-11
Classification: H04W

Abstract:
In the region where the density of radio wave of CDMA system is high, in case that the pilot signal is detected from more than three BSs by superposition, a soft swap handoff method in CDMA cellular system to perform optimal handoff by adding the BS with the strongest pilot strength, comprising the steps of:sending the pilot strengths of the present-added BSs and the newly detected BSs whereof the pilot strength is above T.sub.-- ADD the threshold value of said pilot strength to BSC through PSMM;sending HDM to a mobile station to drop the BS with said weakest pilot strength by activating only the remaining BSs except the BS with said weakest pilot strength after comparing the pilot strength of the present-added BSs through said PSMM transferred from said mobile station to said BSC;dropping applicable BS by said BSC after said mobile station receives said HDM from said BSC and drops the BS with the weakest pilot strength among the present-added BSs and sends the result to said BSC through HCM;sending PMRO from BSC to said mobile station to inform pilot strength of adjacent BSs detected by said mobile station;sending said pilot strength of said adjacent BSs to BSC through PSMM in order to set the BSs whereof pilot strength is above T.sub.-- ADD at present and the BS which was added once but now is dropped, as candidate set of newly added BS;sending the HDM to said mobile station in order to perform handoff after comparing the pilot strengths by said BSC and adding the BS with the strongest pilot strength among the candidates to be added newly; andsending the results to said BSC through HCM after that said mobile station receives said HDM and adds the BS with the strongest pilot strength among the candidates to be added newly and handoff is performed.