In this chapter, we look at the performance of transmission links with two-hop relaying. Each link has two end nodes, one source node and one destination node, and one or multiple relay nodes. The direct link between the end nodes may or may not exist. The relay nodes can use either amplify-and-forward (AF) or decode-and-forward (DF) when forwarding received signals. In one-way relaying, the relay node receives from one end node and then forwards to the other end node; and in two-way relaying, the relay node combines the received signals from both the end nodes and forwards simultaneously to the two end nodes. Relationship between link capacity and node transmission power for different combinations of the link and transmission conditions is studied.