Channel estimation with linear interpolation and decision feedback for UTRA FDD downlink

This paper introduces a channel estimation (CE) scheme called linear interpolation with decision feedback (LIDF) for downlink coherent Rake-combining in a DS-CDMA mobile environment. In this case an UTRA FDD scenario is taken for showing the feasibility of this approach. This scheme uses known periodically time-multiplexed pilot symbols for interpolating the channel coefficients in between. It decides all symbols within the focused slot and takes them to do a new channel estimation using a linear regression to refine its estimation. Besides using this LIDF on pilot sequences of every dedicated physical channel (DPCH) in UMTS, the refinement of the estimation by regression could also be used for the common pilot channel defined in the 3GPP UTRA FDD DL specification. This main approach has been done for 2G systems before and is now implemented for 3GPP UTRA FDD DL. The basic advantage of this approach is to have good noise reduction capability and good adaptation to the time variant channel coefficients. Some simulation results for the and multiple users for the LIDF-CE compared with other well known CE-filters are presented.