An asynchronous cooperative transmission scheme

This paper proposes a novel asynchronous transmission scheme for cooperative wireless networks using Alamouti coded orthogonal frequency division multiplexing (OFDM) modulation. The proposed scheme obviates the need for the timing synchronization at the relay nodes through a renewal of the cyclic prefix (CP) of the OFDM symbol, and achieves a cooperative diversity gain through some simple complex-valued operations at the relay node. Numerical results demonstrate that the bit error rate (BER) performance of the proposed scheme, unlike that of the conventional scheme, does not degrade even when there exists a timing synchronization error at the relay nodes, and also, that the proposed scheme obtains two times higher cooperative diversity gain compared with that of the conventional scheme at the cost of the symbol transmission rate being reduced by half.