||In order to improve the transmission efficiency, wireless communication adopts uplink and downlink technologies. Through uplink, the user equipment (UE) feedbacks channel state information (CSI) to the base station (BS), then BS can change the transmission mode according to current CSI and achieve better transmission efficiency. However, the traditional channel estimation method can only estimate the total channel impact on each signal. Therefore, UE needs to feedback huge amount of CSI. In order to reduce the feedback of CSI, this paper proposes a new channel estimation method. This method uses newtonized orthogonal matching pursuit (NOMP) to estimates the gains and delays of the downlink channel, so we only need to feedback small amount of detail information of the channel to BS, then we can reconstruct the downlink channel in BS. |
We also want to use this method for carrier aggregation technology. However, the channel gains of different frequency bands are not the same. Therefore, we first estimate the detail information from one of the frequency bands (which we define inband in this paper), then use least square (LS) to re-estimate the channel gain of other frequency bands (which we define out-of-band in this paper). By this method, we can not only reduce CSI, but also reduce pilot signals of out-of-band. At the end of this paper, we use over-the-air test to validate the performance of the algorithm.