Spectrum Shaping Using Weighted Code-Hopping CDMA

Spectral shaping is one of the primary technical challenges in spectrally constrained multiple access applications. In this paper, we introduce an efficient spectrum shaping technique based on code-hopping CDMA. In this approach users are allowed to hop between available spreading codes with different probabilities. The proportion of time that each code is used for spreading is determined by an assigned code-weight. We show that the code-weights can be chosen such that the power spectral density of the resulting signal would approximate a desired shape without changing the pulse shape. We also analyze the impact of the hopping patterns on the system capacity in the multi-user orthogonal CDMA systems