Study On Design And Simulation Of Multi-User MIMO Systems

With the development of mobile communication, the capacity of communication systems cannot meet the users' requirement, which is increasing day by day. How to utilize wireless spectrum efficiently becomes more and more important. Nowadays multi-antenna technology is regarded as one of the most effective methods to improve spectrum utilization. Adopting multi-antenna technology within mobile communication systems can increase channel capacity, enhance spectrum efficiency, and extend covered area, etc, which will improve the system performances significantly. As spread spectrum communications can extend the spectrum of signals, transmit signal can be modulated using spread spectrum sequence and related demodulation technology can be adopted to achieve good performances which are difficult to achieve within narrow-band communications. Therefore, the spectrum will be easy to reuse; better wireless spectrum efficiency, better performance of anti-jamming and lower bit error rate will be achieved; finally CDMA multi-user systems will be realized.The main content of the thesis around the subjects of multi-antenna and spread spectrum technology is as follows. Firstly, research on the existing Multi-Input Multi-Output (MIMO) technology, such as MIMO system performance, capacity, space-time coding. Secondly, research on multiple access technology, mainly focused on CDMA technology. Thirdly, study on combination of MIMO and multiple accesses, construct multi-user MIMO systems and analyze their performances. Different kinds of multi-user MIMO systems are simulated on computer.The thesis briefly discusses MIMO technology, mainly including different space-time coding technology. MIMO wireless communication technology is the outcome of the combination of antenna array diversity and space-time process technology; it has the advantage of both two technologies and belongs to the generalized concept of intelligent antenna. The combination of transmit diversity, receive diversity and channel coding technologies becomes the trend of development of wireless communications. In multi-path environment, the increase of the distance of elements and angular extension and the combination of space-time process is good for capture, separation and combination of multi-path. MIMO systems adopt multi-antenna elements at both transmitter and receiver. The system performance can be improved through array gain, diversity gain, spatial multiplexing and interference elimination.MIMO mobile communication based on antenna array has become one of the important breakthrough technologies. MIMO mobile communication can be viewed as the further development of mobile communication systems of array antenna or intelligent antenna. MIMO can efficiently utilize random fading and multi-path delay extension, thus improves both transmit rate and performances significantly for wireless communication systems. This will make MIMO technology become new research subject for mobile communications.The thesis studies on multi-user MIMO systems. Through the specific selection of simulation models of wireless channel transmission, matlab/simulink is adopted as the computational tool for modeling and simulation. The system performance within multi-user systems is investigated. Finally, the results of simulation experiments with different system parameters and coding modes are analyzed.