In this paper, we consider an asynchronous bidirectional communication system over flat fading channels in which the two source nodes are not perfectly synchronized. A low complexity pilot aided timing estimation and resynchronization scheme is proposed to combat the fractional asynchronous delay between the two source nodes. In the proposed scheme, cyclic prefixed single carrier block transmission is implemented at the two sources and frequency domain orthogonal pilots are transmitted to the relay simultaneously. After timing and channel estimation at the relay, a fractionally spaced frequency domain equalizer is employed at the relay to resynchronize the received mixed signals. With the proposed resynchronization scheme, the data detection at the two sources is the same as in a perfect synchronized system, because the two asynchronous signals are already resynchronized at the relay node. Simulation results show that the performance gap between the proposed scheme and the perfect synchronized system is within 1dB when there are four antennas at the relay. Copyright © 2014 John Wiley & Sons, Ltd.
['Zhaoxi Fang', 'Feng Liang', 'Zunyi Wang', 'Danjiang Chen']
Low complexity timing estimation and resynchronization for asynchronous bidirectional communications with multiple antenna relay