Joint time and frequency offset estimation for DMIMO-OFDM in vehicular networks

Cooperation in a vehicular network allows to opportunistically form a virtual antenna array (VAA) to accelerate information exchange resulting in safer transportation. Moving to such cooperative communication requires synchronization in order to realize the concept of the distributed coherence. In this paper, we propose a joint parameter estimation of multiple timing offset (MTO) and multiple carrier frequency offset (MCFO) for estimate-and-forward (EF) cooperative communication employing orthogonal frequency division multiplexing (OFDM). The estimation errors at the relays which contribute inter carrier interferences (ICI) are considered for mathematical analysis. The system model considers multiple antennas at the relays. An iterative algorithm based on expectation conditional maximization (ECM) is proposed for joint estimation of synchronization parameters over a quasi-static channel. Performance of the estimator is evaluated by means of mean square error (MSE) and bit error rate (BER). ECM estimator´s performance is enhanced for multi-input multi-output (MIMO) configuration at the relays.