Forward link performance of multicarrier CDMA with different allocations of quasi-orthogonal codes

This study introduces some code assignment policies suitable for the forward link of a multicarrier DS-CDMA system employing quasi-orthogonal sequences to increase its capacity. It points out how different allocation strategies alter the interference level suffered by active units, and how it is possible to deliberately shape the rate of interference growth as a function of the number of active users within the reference cell. The performance achieved by several schemes is assessed in a frequency selective fading environment, in terms of average bit error probability experienced by users who are assigned either Walsh or quasi-orthogonal code sequences. Alternative assignment criteria are critically compared and the most advantageous solutions highlighted.