Tensor-Based Channel Estimation for Cooperative Diversity Scheme in the Presence of Timing and Frequency Offsets

The distributed nature of cooperative networks may result in multiple carrier frequency offsets (MCFOs) and multiple timing offsets (MTOs), which overshadow the diversity gains promised by cooperative communications. So the estimation of MCFOs and MTOs is an important implementation issue in practice. In this paper we propose a new channel estimation both at the relays and the destination in distributed space-time block code (DSTBC) based amplify-and-forward (AF) cooperative networks in the presence of MCFOs and MTOs. We propose tensorbased channel estimation (TENCE) scheme, which does not assume any perfect frequency or timing synchronization. Moreover, the canonical polyadic (CP) decomposition for the tensor, associated with channel gains, frequency offsets and timing offsets, is proposed in the cooperative communication systems. We also demonstrate that TENCE can be improved by the iteration. Simulation results show that the proposed TENCE scheme can achieve a better performance in the presence of channel and synchronization impairments in multi-relay AF cooperative communications. Depending on the scenario, we also show that the significant improvements in estimation accuracy are achievable by TENCE iterations.