Multi-rate DS-CDMA radio interface for third-generation cellular systems

The authors outline the concept of an open and flexible CDMA radio interface for third-generation mobile and personal communication systems which has been developed in the RACE Project R2020 (CODIT). The advanced CDMA system concept elaborated in CODIT is based on asynchronous multi-rate direct-sequence CDMA characterised by long pseudo-noise spreading codes, variable spreading factors, multiple chip rates and multiple RF bandwidths. The multi-rate DS-CDMA technique offers great flexibility with respect to spectrum and radio resource management, system deployment, and service provision. Furthermore, a time division technique (compressed mode transmission) for CDMA systems is introduced which enables seamless inter-frequency handover between radio cells at different hierarchical layers (e.g. pico, micro, macro cells)