Frequency prediction of the channel transfer function in multiple antenna systems

Having the channel state information of the channels over which the signals propagate from the transmitter to the receiver available at both sides of the transmission link is beneficial in many wireless applications. However, in frequency division duplex systems, a base station can only estimate the channel transfer function of the uplink channel based on the transmission of a-priori known training signals from the mobile station. A mobile station can only estimate the channel transfer function of the downlink channel based on the transmission of a-priori known training signals from the base station. Due to the frequency selective behavior of the mobile radio channel, the channel transfer functions of the uplink channel are different from the channel transfer functions of the downlink channel. In order to obtain the channel state information of the downlink channel in the base station or the channel state information of the uplink channel in the mobile station it is possible to feed back this information from the mobile station to the base station or from the base station to the mobile station. However, this feedback of the channel state information decreases the spectral efficiency. This paper introduces novel techniques to obtain the channel state information of the downlink channel in the base station based on the channel state information of the uplink channel in multiple antenna systems. Measurement results show the good performance of the investigated techniques. Thus, the signalling overhead can be reduced.