The capacity of three-node wireless relay channel was analyzed. While previous research work showed how parameters like relay numbers

antenna numbers and fading affected the capacity

focused on the impact of relay position. By analysis results

there were three modes that the capacity will follow: with relay moving from source toward destina- tion

the capacity can decrease （mode C1）

or increase （mode C3）

or decrease after increasing （mode C2）. A numerical example was given to verify the theory.