Two different philosophies in CDMA-a comparison

There has been considerable interest recently in the subject of multiuser interference cancellation techniques for CDMA wireless systems. It is widely believed that a system design using interference cancellation techniques has considerably better capacity than the design methodology adopted in the IS-95 CDMA cellular standard, which does not use such techniques. We examine this issue, and in particular focus on linear interference cancellation techniques. Linear techniques are simpler and require fewer assumptions, such as accurate knowledge of amplitude and phase information of the users to be canceled, than nonlinear interference cancellers. However, linear interference cancellation techniques require a fundamentally different CDMA system design philosophy than IS-95. In IS-95, the coding gain from error control codes bears the burden of handling interference, while a linear canceller uses the dimensional separation of users. This paper compares and contrasts the two design philosophies. Our comparison is based on overall user capacity (defined as the number of users per Hz per unit area) as well as robustness and fairness. The focus of the paper is on the mobile-user to base station reverse link which is modeled by the classical many-to-one multiple-access problem