Simplified statistical replacement models for channel estimation in WCDMA

Abstract

This paper provides a statistical analysis of channel estimation errors and gives simplified replacement models that can be used to speed-up link- as well as system-level simulations. Although the investigations are carried out for downlink dedicated physical channels (DL-DPCH) of third-generation wideband CDMA (3G WCDMA), specified by 3GPP for IMT-2000/UMTS (UTRA), the main results are also suitable for the uplink. It turns out that in almost all cases well-known distribution functions for the channel estimation error amplitudes and phases can be used to model real channel estimation behavior efficiently. For low to medium speed vehicular environments without interference, the error amplitudes can be assumed to be Rician and the error phases are uniformly distributed. For low speed indoor environments, the resulting error phases can be neglected and error amplitudes are best represented by the Nakagami-m distribution. In general, the higher the velocity of the mobile and the interference of other channels get, the more error amplitudes follow a Suzuki distribution. The given models show to be applicable to replace computational intensive real channel estimation. They could also be used in radio network and radio protocol simulations, e.g. to quantify time-variant demodulator losses.