Patent ID: 7079510

Claim:
A method for allocating a code in connection with soft handover in a CDMA system in downlink transmissions from a base transceiver station (BTS) to a mobile station (MS), the method comprising: allocating codes in the base transceiver station (BTS) according to a specific code tree, wherein a specific first spreading factor (SF=2) corresponds to each code (C 2, 1 ) and it is possible to derive from a code that has a specific spreading factor, two codes (C 4, 1 , C 4,2 ) that have a higher second spreading factor (SF=4), characterized in that the method comprises: allowing the base transceiver station to use said first spreading factor (SF=2) in code allocation in all downlink transmissions; allowing the base transceiver station to use both codes simultaneously (C 4, 1 , C 4,2 ) that have said second spreading factor (SF=4) in code allocation in downlink transmissions when the receiving mobile station is in connection with only one base transceiver station; and limiting the use of said second spreading factor (SF=4) in code allocation in downlink transmissions when the receiving mobile station is in connection with at least two base transceiver stations (BS A, BS B) simultaneously so as to allow the base transceiver station to use only one (C 4, 1 or C 4,2 ) of said two codes (C 4, 1 , C 4,2 ) that have said second spreading factor (SF=4).