Methods and apparatuses are provided for uplink MIMO transmissions in a wireless communication system. In particular, a single inner loop power control may be utilized to control a power of both a primary stream and a secondary stream, in a system where the power of the secondary stream is linked to the power of the primary stream. That is, a single transmit power control command calculated according to the primary stream and directly controlling the power of the primary stream can effectively control the power of both uplink streams. Further, the disclosure provides outer loop power control, where a signal-to-interference ratio target used in the inner loop power control can be adjusted. Here, the SIR target may be adjusted in accordance with at least one of a block error rate performance or a HARQ failure performance of one of the primary stream or the secondary stream.