The Optimal Assignment of Orthogonal Polyphase Sequences in CDMA Systems
Liupiao Zhang, Yujuan Sun · IEEE Communications Letters · 2017
In this letter, ternary semi-bent functions and a complex Hadamard matrix are used to construct spreading sequences for code-division multiple-access systems. An efficient assignment of these sequences to a lattice of regular hexagonal cells, which are mutually orthogonal within each cell and the adjacent cells, is achieved and most notably the number of sequences per cell is maximum possible. The large sequence reuse distances, being √27, and low cross-correlation between non-orthogonal sequences (in non-adjacent cells) make these sequences appealing for practical applications.