N-shift cross-orthogonal sequences
IEEE Transactions on Information Theory
Comparison of the Two Signal Design Methods in the CDMA Systems Using Complete Complementary Codes
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Orthogonal complementary codes for interference-free CDMA technologies
IEEE Wireless Communications
A New Framework for Constructing Mutually Orthogonal Complementary Sets and ZCZ Sequences
IEEE Transactions on Information Theory
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A code-division multiple access (CDMA) communication system achieves the maximum spectral efficiency over multipath fading channels if employed spreading sequences have ideal correlations, i.e., the ideal auto-correlation that are zero except for zero shift and the ideal cross-correlations that are zero for all shifts. Unfortunately, such sequences are known nonexistent and, Suehiro and Hatori proposed a sequence family with ideal correlation sum called the complete complementary code (CCC). For (quasi-) synchronous CDMA systems, the ideal correlation sum of CCC provides an inter-channel interference (ICI)-free communication and CCC based CDMA (CCC-CDMA) improves spectral efficiency significantly. In previous work, we have proposed a general and systematic construction of the optimal CCC. However, in special cases, the proposed construction results in CCCs with extra interesting properties. In this paper, we propose a new type of CCC called the Z-connectable CCC (Z-CCC), which gives a sequence set with zero correlation zone (ZCZ) by connecting codes in its complementary codes. We also present two Z-CCCs which consist of rows of the discrete Fourier transform (DFT) and Hadamard matrices. Due to Z-CCC provides the guard-part reduced sub-packet structure, Z-CCC based CDMA (Z-CCC-CDMA) realizes higher spectral efficiency than the traditional CCC-CDMA and, intimate relationships of the present Z-CCCs and the DFT matrix or Hadamard matrix allows low implementation complexity.