Code Tree Extension and Performance Improvement in OVSF-CDMA Systems

UTRA-FDD systems use orthogonal variable spreading factor (OVSF) codes for channel separation in uplink and downlink. The OVSF codes are the limited resources in the downlink. The limited codes as well as code blocking property of OVSF codes gives lower system throughput. In this paper the OVSF code tree is extended such that the capacity of the tree becomes four times. Also the modified system uses single rake combiner providing no additional complexity increase in the user equipments (UEs). Simulation results are demonstrated to show the reduction in new call blocking probability using the OVSF code tree extension