Joint Application Of Qo-STBC And Transmit Beamforming

With people's increasing demand on advanced wireless communication technology. More and more people start to focus their researching on the next generation mobile communication technology, B3G (beyond 3G) or 4G. From the technique point of view, higher data transmission rate, larger system capacity and better communication QoS are the key objects of new mobile communication technology to be break through.Beamforming comes from smart antenna,its typical technical superiority is strengthening desired signal and suppressing interference. It is also the base to realize SDMA (Space Division Multiple Access). STBC (Space Time Block Code) is the main method to realize MIMO (Multiple Input Multiple Output) diversity, and it is good at mitigating wireless multipath fading. In view of development, the combination of beamforming and STBC will adequately exert the advantage of multi-antenna system and result in enhancing the system performance significantly. According to some new thoughts, this paper proposed some new scheme to solve problems during research recently.First, the rationale for STBC and beamforming techniques is described, mainly focusing on the orthogonal STBC, quasi-orthogonal STBC and transmit beamforming, which are the foundation of the following combination scheme. We also make extension the conception of beamforming, including the traditional beamforming in smart antenna system and the generalized beamforming in MIMO wireless system.In the second part, the performance of the combined beamforming of space-time block coding according to the number of antenna array group was analyzed; compare the two scheme under different DOA and SNR, analyzed the performance of two scheme.We also study the key coefficient of the system, optimize the results of the emulation.At last, a new improved scheme for downlink transmit beamforming system based on Qo-STBC is proposed. The key feature of the scheme is separating the signals of system, eliminating the interference from the neighboring signals via composite weighting and the improvement of the way of receiving signals, so this scheme enhance the performance of the system. We also study the situation of un-perfect channel.