Space-time transmit diversity (STTD) is an open loop multiantenna transmission method adopted in 3G standard. This technique uses the space-time block code (STBC) at the base station to combat deep channel fading. In order to enhance the STTD system performance, adaptive algorithms were proposed in which the corresponding information can be fed back to adjust the transmit weights according to the channel conditions. In this paper, the performances of STTD with various transmit weights and receiver structures are investigated via theoretical analysis and numerical simulations. And their respective compatibility and implementation complexity are pointed out.