Line rate(s) selection for cellular DS-CDMA systems with integrated traffic

Fong et al. (1994, 1995) introduced the idea of using the concatenated orthogonal/PN spreading scheme for integrated traffic. Fong et al. (1995) proposed using a single line rate (adjusted data rate before spreading) to accommodate traffic with a wide range of source rates. In this paper, we further investigate the choice of line rate(s) (either single or multiple) with emphasis on its effect on spreading sequence usage and user capacity. In conjunction with this, we propose a new scheme called orthogonal subsets of Walsh Hadamard codes in order to provide orthogonality between spreading sequences of different length. The advantages and disadvantages of the single line rate scheme versus the multiple line rate scheme are considered which leads to the selection criterion for the optimal line rate(s).