Identification of Taps in Time-Variant Multipath Channels for 3GPP LTE-Downlink

Accurate knowledge of the time-variant mobile radio channel is essential to achieve high data rates in modern wireless communication systems e.g. 3GPP LTE-downlink. Known tap positions in the Channel Impulse Response (CIR), along with the received pilot symbols, provide improved estimation of CIR. The estimated CIRs are then used in tracking algorithms, e.g. the Basis Expansion Model (BEM), to track time variations caused by the Doppler effect. In recent years BEM-based methods have been improved substantially. Their performance largely depend on the estimated CIRs. Therefore the tracking accuracy of the time-variant channel mainly depends on the CIR estimation. Here we present a novel technique to detect tap positions in the CIR. Our proposed method is based on the fact that only actual taps in the CIR experience Doppler effect. The error probability of the algorithm is as low as 10(exp -2) when moving with a speed of up to 350 km/h. A 3GPP LTE-downlink MATLAB simulator is used for providing simulation results.