In this paper, we will present diversity gain analysis of a novel channel assignment scheme at the relay for the case in which two non-cooperative independent users communicate with their destination through a single relay and by using only two frequency channels. The analysis of two main relay techniques, namely the amplify-and-forward (AF) and decode-and-forward (DF) will be provided. As the results show, the DF approach provide a higher diversity gain especially in scenarios in which the relay is closer to the receiver.