Steven P. Nicoloso

Linear versus non-linear interference cancellation

In this paper we compare linear and non-linear interference cancellation for systems employing code division multiple access (CDMA) techniques. Specifically, we examine linear and non-linear parallel interference cancellation (also called multistage cancellation) in relationship to other multiuser detection algorithms. We show the explicit relationship between parallel interference cancellation and the decorrelator (or direct matrix inversion). This comparison gives insight into the performance of parallel interference cancellation (PIC) and leads to better approaches. We also show that non-linear PIC approaches with explicit channel estimation can provide performance improvement over linear PIC, especially when using soft non-linear symbol estimates. The application of interference cancellation to non-linear modulation techniques is also presented along with a discussion on minimum mean-squared error (MMSE) symbol estimation techniques. These are shown to further improve the performance of parallel cancellation.

Frame Quality-based Versus Eb/No-based Forward Power Control Methods for the cdma2000 Third Generation Standard

Fast forward link power control is one of several improvements offered by third generation standard cdma2000 over the well-known second generation IS-95. This paper describes each of the five forward power control methods allowed in cdma2000, wherein the slow frame quality-based algorithms are similar to those of IS-95. We examine the performance of frame quality-based versus E b /N o -based (fast) power control for a typical voice traffic channel and a high data rate traffic under various geometries and a wide range of mobile station velocities. We also consider the impact of Space-Time Spreading (STS) transmit diversity along with power control. Forward link power control proves itself to be a worthwhile addition to CDMA, providing substantial gains in capacity where they are needed most, viz., at low speeds where FEC interleaving is weaker. The effect of time-correlated shadowing is also considered and experimental results suggest that actually may show additional gains hidden by conventional static (Rayleigh fading only) experiments.