Low feedback downlink MIMO channel estimation for distributed FBMC systems using SNR measurements

In this paper, we present a new method to estimate the MIMO channel in a distributed MIMO system using FBMC modulation (Filter Bank based Multicarrier). As opposed to previously presented methods, it is not based on the existence of pilots and therefore avoids the necessity of auxiliary pilots or similar methods. Besides, it requires a very low amount of feedback. Only the SNR observed by the different users need to be fed back periodically. It is intended for the estimation of the downlink MIMO channel in a distributed beamforming system where the basestations can cooperate to some extent. It is based on the concept of adding small, controlled, perturbations to the transmitted signals and observing the related changes to the SNR at the receivers. It is shown in this paper that, based on a limited amount of SNR measurements from the receivers, it is possible to accurately estimate the MIMO channels, both in amplitude and phase. It is also shown that the proposed method exhibits the best performance in a tracking mode.