Development of the next generation CDMA technology and lessons we learnt from the past

In this paper, we start with the review of the history of CDMA technology development and technical limitations for the current CDMA technology, and then proceed to propose the next generation CDMA (NG-CDMA) technology for its use in future high-speed all IP wireless communications. We will also address the issues on the technical features offered by the NG-CDMA technology, including the innovation in the CDMA code design approach, i.e., the REAL approach, and then multi-dimensional spreading techniques, which become the cores for the NG-CDMA technologies. Our earlier works showed that an CDMA system can offer an interference-free operation if we use orthogonal complementary codes (OCC) generated by the REAL approach. The orthogonality of the OCC is guaranteed in both asynchro-nous and synchronous transmission channels even with multipath propagation, making it an ideal choice for many applications in futuristic wireless systems. The multi-dimensional spreading technique offers us more degree-of-freedoms to design a CDMA system which offers an inherent mitigating capability to frequency-selective and/or time-selective fading. Adding an additional space-domain to the existing frequency-time two dimensional spreading, we can have a CDMA system which offers frequency-time-space three dimensional spreading capability, integrating CDMA coding with space-time coding, to make a CDMA system that enjoys the benefits of both interference-free and full-diversity gain. This paper will also offer an overview on the cause of development of CDMA technology, the comparison between NG-CDMA and OFDMA technologies, as well as many lessons we learnt from the past, guarding us for the design of futuristic multiple access technologies.