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This paper presents two new constructions of two-dimensional (2D) spreading codes, here designated as 2D orthogonal variable spreading factor (OVSF) codes, for multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) systems. Orthogonality of these spreading codes is employed to improve the bandwidth efficiency and interference rejection capability of the DS-CDMA systems. The 2D OVSF codes are constructed by generalizing one-dimensional (1D) OVSF codes and they possess ideal correlation properties. As illustrated in this paper, these 2D OVSF cods preserve the orthogonality of different spreading factors in an OVSF code tree, supporting multimedia services with a variety of data rates.
Communications, 2003. ICC '03. IEEE International Conference on (Volume:5 )
Date of Conference: 11-15 May 2003