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This study deals with the study on the performance of the hybrid transmission scheme combining both beamforming and spatial multiplexing for multiple spatial streams. The capacity of the hybrid scheme is evaluated and compared with that of the beamforming scheme for a single spatial stream in both line-of-sight and multi-path channels. Two kinds of hybrid schemes are considered: the shared antenna architecture, where each antenna processes all spatial streams and the split antenna architecture, where each antenna processes only one spatial stream. The effects of the channel parameters, such as the antenna spacing, the existence of reflected paths etc. On the capacity and the optimal beams and powers are examined. The frequency-selective property of the capacity and optimal beams and powers are also investigated. In this study, a scenario is assumed, where the same analogue radio frequency (RF) beamforming vector (or matrix) is applied to all subcarriers whereas the digital baseband power allocation is executed individually at each subcarrier.