Pilot Power Allocation for OFDM in DAS

In distributed antenna system (DAS), since the distances from the remote antenna units (RAUs) to the mobile are different, the transmitted power of pilot symbol in orthogonal frequency division multiplexing (OFDM) needs to be optimized to provide a reliable channel estimation for the purpose of coherent detection. In this paper, we present a novel pilot power allocation strategy for OFDM in DAS which is developed based on the criterion of minimizing the mean square error (MSE) of channel estimates at pilot subcarrier across the RAUs. The proposed method only needs the information of large-scale fading at transmitter to allocate power, which makes it feasible in practical OFDM DAS systems.