Future wireless communication systems ought to offer a high spectral efficiency and an inherent flexibility to carry diverse services with variable rate requirements. The rate change should be made scalable, continuous and real-time based to match exactly to the required data rate for conservation of precious bandwidth. The rate change in multiples of two, as implemented in the existing 3G W-CDMA standard, is undesirable. It is also preferred that the multiple access technique itself should support asymmetrical traffic in up- and down-links to fit connection modes of the Internet services. This paper is a review of our recent research effort to propose an innovative CDMA architecture based on complete complementary codes, which can satisfy major requirements for the future mobile Internet applications. The architecture uses a new "offset stacked" spreading technique, based on which both high spectral efficiency and scalable rate-matching are guaranteed. To measure spectral efficiency of the systems, "spreading efficiency" (SE) is defined as the information bit(s) conveyed by each chip. All traditional CDMA-based standards offer an SE of 1/N, where N is the processing gain. On the contrary, the SE of the proposed architecture can be made as high as one. As the bandwidth of a CDMA system is determined by its chip width, a high SE means a high spectral efficiency. This paper illustrates that the proposed scheme is well-performing and has a great potential for applications in future wireless communications beyond 3G.
['Hsiao-Hwa Chen']
A new CDMA architecture based on complementary codes enabling isotropic MAI-free operation