Patent ID: 8804602

Claim:
A method of communicating by a base station in a wireless communication system including a relay station, the method comprising: configuring, by the base station, a downlink (DL) access zone for communicating with a mobile station and a DL relay zone for communicating with the relay station or the mobile station; transmitting, by the base station, a multiple-input multiple-output (MIMO) midamble for the mobile station in the DL access zone; and when an R-amble indicator is included in a specific field in a DL message, transmitting, by the base station, an R-amble for the relay station in the DL relay zone, the R-amble being an additional MIMO midamble for the relay station, the R-amble indicator indicating whether or not the R-amble should be transmitted in the DL relay zone; wherein, if the R-amble indicator is set with a specific value, the R-amble is to be transmitted; wherein the R-amble indicator is transmitted to the mobile station through a secondary-superframe header (S-SFH) SP 2 .