MMSE channel estimation and time synchronization tracking for cooperative MIMO-OFDM with propagation delay differences

We propose a method for concurrent OFDM fine time synchronization to different stations with propagation delay differences, and a receiver based delay difference compensation method for MMSE channel estimation, which are needed to enable cooperative MIMO-OFDM transmission. Cyclic prefix removal is done dynamically with respect to the closest station, which allows for intersymbol interference free reception from all cooperating stations (if cyclic prefix length is adequately chosen). Pilot phase rotations caused by delay differences are compensated to allow for practical MMSE channel estimation with precomputed interpolation matrices. Simulative evaluation is done using 3GPP LTE parameters. Channel estimation mean square error and bit error rate curves show the method able to support cooperative MIMO-OFDM.