Joint beamforming and transmit diversity for wireless communications

Antenna arrays can be used in wireless communication systems to improve system performance. Both beamforming (BF) and transmit diversity (TD), which exploit antenna arrays, are promising techniques for increasing channel capacity. Two downlink transmission methods combining beamforming with transmit diversity in the closed-loop mode are proposed, and, according to the actual channel states, the transmitter can adaptively change the transmission mode between the two methods. Both the methods combine BF, space-time block coding (STBC) and selection transmit diversity (STD), but the first one uses diversity arrays while the second one uses beamforming arrays for downlink transmission. By simulation, the complexities of the two methods are compared with respect to antenna configuration and information feedback, and their improved performances over the original STBC scheme are investigated in detail.