Estimation of Time-Varying Wireless Channels and Application to the UMTS W-CDMA FDD Downlink
نویسندگان
چکیده
In this paper we consider the estimation of mobile channels that are modeled as autoregressive processes with a bandwidth commensurate with the Doppler spread. Pilot based estimation leads to brute FIR channel estimates on a slot by slot basis. These estimates are then refined by Wiener filtering across slots that performs the optimal compromise between temporal decorrelation due to Doppler spread and slot-wise estimation error. We furthermore propose adaptive filtering techniques to implement the optimal filtering. For structured multipath channels, we introduce 2D filtering in which the refined FIR channel estimates are optimally approximated by a multipath model in every slot. The techniques are illustrated with applications from downlink channel estimation in the 3G UMTS W-CDMA FDD system.
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