Patent ID: 7929995

Claim:
A system to transmit/receive a signal, the system comprising: a base station (BS); at least one mobile station (MS); and a relay station (RS) comprising: a first antenna set including at least one antenna, used for signal exchange with the BS; and a second antenna set including a plurality of currently allocable antennas, used for signal exchange with the MS, wherein the RS selects at least one antenna from the second antenna set for each of the at least one MS, and exchanges a signal with the MS using the selected at least one antenna, wherein the RS transmits a second downlink signal to the MS in a same time interval as a time interval for which it receives a first downlink signal transmitted to the RS by the BS, wherein when a number of antennas included in the second antenna set is greater than or equal to two (2), the RS selects at least one antenna to be used for signal exchange with the MS using a channel quality for each of the at least two antennas, wherein the channel quality comprises an average channel power gain (ACPG), and wherein the RS generates an allocable antenna set including antennas currently allocable to the MS in the second antenna set, selects an antenna having a highest ACPG among the antennas included in the generated allocable antenna set, excludes the selected antenna from the allocable antenna set, determines whether there is any antenna having ACPG exceeding a predetermined ACPG threshold in the allocable antenna set when a number of antennas selected is less than a number of antennas included in the second antenna set, and if there is an antenna having ACPG exceeding the ACPG threshold, selects an antenna having a highest ACPG among them.