Differential Space-Time-Frequency Transmission for Amplify-and-Forward Asynchronous Cooperative Communications
Xu Jing · Xi'an Jiaotong Daxue xuebao · 2009
Focusing on asynchronous cooperative communication systems over frequency-selective fading channels,a distributed differential space-time-frequency(ADSTF) coding scheme is proposed by using the amplify-and-forward protocol.By applying full diversity rotation,Cayley transformation and OFDM modulation at the source node and then amplifying and forwarding the received signal at the relays,a ADSTF code is constructed.The proposed scheme can achieve both spatial and multi-path diversities without either perfect synchronization at the relays or any instantaneous channel state information at the destination node.Compared with the differential OSTBC OFDM transmission,the ADSTF transmission scheme can obtain higher transmit diversity.Simulation results show that the ADSTF scheme outperforms the differential OSTBC-OFDM scheme with BPSK modulation by 3 dB at bit-error-rate of 10-3 with only a rate loss of 0.25 b/(s·Hz).