The fourth generation mobile communication system is expected to be implemented on a frequency band higher than the bands already assigned for IMT-2000. Therefore, to compensate propagation loss, relay schemes have been investigated. Amplify-and-Forward (AF) relay has advantages on complexity and time slot usage. However, the coupling effect between transmit and receive antennas in the relay station is the cause of performance degradation. Thus, in this paper, the coupling effect is evaluated and a frequency offset amplify-and-forward relay scheme is proposed by the authors. It is shown that the proposed scheme can alleviate the coupling effect in the AF relay system.