Superimposed Pilots Aided Joint CFO and Channel Estimation for ZP-OFDM Modulated Two-Way Relay Networks

Existing works on joint carrier frequency offset (CFO) and channel estimation in two-way relay networks (TWRN) only deal with the composite channel parameters and the mixed CFO values. In this paper, we design a superimposed pilot based training strategy such that the individual frequency and channel parameters can be obtained at the source terminals. We consider the amplify-and-forward (AF) relaying scheme and discuss the zero-padding (ZP) based orthogonal frequency division multiplexing (OFDM) modulation in order to cope with the frequency selective fading channels. We build up the system model and propose the joint estimation method. An iterative process is also proposed to further improve the estimation accuracy. To make the study complete, we also derive the Cram´er-Rao Bound (CRB) and compare with the mean square error of our algorithms. Finally, simulation results are provided to corroborate our studies.