A base station with multiple antennas including a relay scheduler to select a serving relay from a plurality of candidate relays. Each candidate relay may have a user group including at least one user. The selection may be based on an achievable transmission capacity of each candidate relay with respect to its user group and a state of channels formed between the plurality of candidate relays and the base station. The base station also includes a transmission signal generator to generate a transmission signal for the user group corresponding to the serving relay.