In multi-relay cooperative systems, the signal at the destination is affected by impairments such as multiple channel gains, multiple timing offsets (MTOs), and multiple carrier frequency offsets (MCFOs). In this paper we account for all these impairments and propose a new transceiver structure at the relays and a novel receiver design at the destination in distributed space-time block code (DSTBC) based amplifyand-forward (AF) cooperative networks. The Cramér-Rao lower bounds and a least

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... s (LS) estimator for the multi-parameter estimation problem are derived. In order to significantly reduce the receiver complexity at the destination, a differential evolution (DE) based estimation algorithm is applied and the initialization and constraints for the convergence of the proposed DE algorithm are investigated. In order to detect the signal from multiple relays in the presence of unknown channels, MTOs, and MCFOs, novel optimal and sub-optimal minimum mean-square error receiver designs at the destination node are proposed. Simulation results show that the proposed estimation and compensation methods achieve full diversity gain in the presence of channel and synchronization impairments in multi-relay AF cooperative networks. Index Terms-Cooperative communication, amplify-andforward (AF), Cramér-Rao lower bound (CRLB), differential evolution (DE), distributed space-time block code (DSTBC), receiver design. This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at IEEE Transactions on Signal Processing, published by IEEE. Copyright restrictions may apply.