On the use of QOF functions with RC3 in Walsh code limited base station deployments

The forward link capacity of a CDMA base station is limited by the available transmit power and orthogonal Walsh code space. The cdma2000 standard defines new radio configurations (RC3 and RC4) that improve forward link capacity. The orthogonal Walsh code space for RC3 and RC4 are 64 and 128, respectively. The link level performance of RC3 is generally better than that of RC4 due to a stronger channel code. In addition, quasi orthogonal function (QOF) sets are introduced in the forward link in order to extend the available Walsh code space. In certain deployments that offer voice services using RC3 it is possible to run out of orthogonal Walsh space before using up available transmit power. Two possible ways to avoid this issue are to use RC4 or RC3 with an additional QOF set. This study compares these two options by a series of lab experiments.