Enhancing data throughput using quasi-orthogonal functions aggregation for 3G CDMA systems

The forward link of an IS-2000 CDMA system may become Walsh code limited under certain scenarios. To enhance the capacity in such scenarios, alternative sets of orthogonal functions called the quasi-orthogonal functions (QOF), which possess optimal minimax cross correlation with Walsh code sets of variable length, have been incorporated in IS-2000. We discuss a method of significantly enhancing the maximum throughput in evolutions of IS-2000 systems. This method uses aggregation of multiple quasi-orthogonal functions with a relatively smaller constellation alphabet size for a single user with a joint multi-channel detector. This method is compared with the alternative method for enhancing the maximum throughput using aggregation of a relatively smaller number of Walsh functions, but with a higher constellation alphabet size (multi-level modulation). Discussions on the trade-offs and recommendations as to the better method for enhancing the throughput in evolutions of IS-2000/3G systems are then provided.