1. An apparatus for adaptively allocating transmission power for beamforming combined with orthogonal space-time block codes (OSTBC) in a distributed wireless communication system, the apparatus comprising: a plurality of geographically distributed sub-arrays for beamforming, each sub-array of said plurality comprising a plurality of distributed antennas placed in random groups; and a central processing unit for identification of a performance of each subset of the sub-arrays by applying a predetermined power allocation scheme thereto, each said subset being obtained by combining the sub-arrays using a Nakagami fading parameter and information about large-scale fading of each sub-array of the sub-arrays fed back from a receiving party, determination of a subset having a best identified performance as an optimal subset according to the identified performances thereof, and performance of power allocation based on the subset determined as the optimal subset, wherein the each subset is a random combination of the plurality of sub-arrays.