Concatenated orthogonal/PN spreading scheme for cellular DS-CDMA systems with integrated traffic
Mo-Han Fong, V.K. Bhargava, Q. Wang · 2002
The application of the concatenated orthogonal/PN spreading scheme for integrated traffic is introduced. Bhargava (1994) proposed using a single line rate (adjusted data rate before spreading) to accommodate traffic with a wide range of source rates. For traffic with source rates higher than the line rate, the authors propose using concatenated orthogonal/PN spreading sequences to subdivide a high rate stream into several parallel line rate streams. The performance of the concatenated orthogonal-PN spreading sequence for homogenous voice traffic in various cellular mobile environments with multipath fading, log-normal shadowing and path loss, is first analyzed and compared with that of the conventional non-concatenated long PN sequence. The authors then evaluate the performance of a system with integrated traffic of voice and video. In conjunction with this, they propose the use of cosets of Walsh-Hadamard (WH) codes to reduce the multi-user interference. Different methods of assigning the spreading sequences among the cosets which improve the capacity of both voice and video users, are investigated.