The future wireless communication systems ought to offer high spectral efficiency and flexibility to carry multimedia services with variable rate requirements. The data rate change should be made scalable, continuous and real-time based to match exactly to what required in different content for conservation of precious bandwidth. The rate change in multiples of two, as implemented in the UMTS W-CDMA standard, is clearly undesirable. In particular, the multiple access technique itself should support asymmetrical traffic in up- and down-links to fit different connection modes of Internet-based applications. This paper is to propose an innovative CDMA architecture based on complete complementary (CC) codes, which can address all above concerns. The architecture makes use of 'offset-stacked' spreading modulation, based on which both high spectral efficiency and flexible rate matching are guaranteed. The proposed CC-CDMA system can support continuously alterable data rates, which can match exactly to the user demand without the need of complex 'rate-matching' algorithms.
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