Research On Mimo Downlink Beamforming

Future mobile communication systems urgently need to adopt more advanced technology, for the purpose of better using of limited power and improving spectrum efficiency. In support of high-speed data transmission, spectrum efficiency and power efficiency, MIMO technology has advantages unmatched by other technologies, so it becomes the importance of technology into a high-speed mobile communication system in the future. Beamforming technology is the key downlink MIMO communications systems technology, and so beamforming technology, optimization and performance improvement become the main issues in the paper.Based on the present technical development, refer to the latest monographs and 3GPP-LTE standards; we research the beamforming in MIMO downlink. From the sides of system optimization and achieve, we make a depth analysis and research to the existing use of beamforming techniques.First researches the single-user Beamforming. In the scheme of Double directional beamforming MIMO, analyzed the application environment of the scheme,results from the Monte Calo simulations indicate that the beam domain MIMO scheme has a potential to bring significant improvement. Then studied the beamforming scheme based on eigenvalue distribution, scheme makes a full use of the channel correlation information, so the MIMO system can get channel diversity gain. The combination of MIMO with smart antenna scheme is the key point. Based on existing schemes, analysed the proposed scheme that combine Turbo-BLAST technology with smart beamforming technology in detail. When the data frame length is shorter, the new scheme can get the accurate channel estimation enough. Simulation results show that this scheme improves the system performance better than the existing schemes.In the researches on multi-user beamforming system, the key points of issues are proportional fair scheduling for random beamforming scheme and zero forcing beamforming scheme. Then propose a new algorithm that improves the performance of semi orthogonal user group zero forcing beamforming schemes.Multi-user random beamforming technology, Base station broadcasts the beam to user that code book is known, the user just responses the signal to noise ratio information, the feedback is much less than zero forcing beamforming. In this paper, single-beam random beamforming system that based on proportional fair scheduling algorithm is a research point. Ensuring the system throughput and user fairness, while significantly reduce feedback overhead.Assuming Perfect channel knowledge at the transmitter, zero forcing beamforming scheme can select orthogonal or semi orthogonal subset of users to be able to eliminate the inter user interference perfectly and implement space division multiple access. When beamforming weight vector is optimal and the number of users approaches the limit, the sum rate in the zero forcing beamforming schemes tends to dirty paper coding system performance. The new algorithm makes the selected users contribution sum rate of and control, based on the semi orthogonal user group algorithm. In the condition of low complexity realized the sum rate of performance improvements.