Application Of Joint Beamforming And STC In Multi-Antenna Systems

Recently, with the rapid development of requirement for data rates and reliable transmission, how to improve the transmission rate and guarantee the quality of service (QoS) becomes a key research point of future wireless communication system. Multiple input multiple output (MIMO) technique becomes an indispensable role for its capability to increase the system capacity without increasing the system bandwidth. At the same time, beamforming technique which has been applied in TD-SCDMA system, has been proved to provide effective array gain and reduce non-target-user's interference, and it has very strong applicability. Hence, the research on multi-antenna technique of joint MIMO and beamforming becomes a hot research point.It is known that beamforming mainly uses the high correlation of the channels, whereas the traditional MIMO requires the independence between each path of the channels, so how to reflect the combination of the two techniques in MIMO channel is the main point of this topic. In this paper, a general introduction of the development of multi-antenna technique comes first, which includes MIMO diversity and its sub-topic of space-time coding and then beamforming is introduced briefly. Then, it mainly focuses on the correlation modeling of MIMO channel, which includes the spatial correlation matrix, the polarized correlation matrix and the joint spatial and polarized correlation matrix. Meanwhile, based on the correlated MIMO channel model, this paper provides the channel capacity formulation and the simulation results show the trends that the capacity reduces with the channel correlation. Furthermore, the signal to noise ratio (SNR) in the correlated channel is discussed. Then, this paper investigates beamforming technique in MIMO correlated channel, and gives the antenna direction pattern by simulation. The conclusion of improvement of bit error rate (BER) performance is drawn through simulation. Meanwhile, the combination schemes of beamforming and space-time block code in dual-polarized correlated channel environment is discussed, and it is shown that the performance is improved compared with the conventional space-time block code.