The Applied Research Of MIMO SDAM In OFDM Systems

The rapid development of mobile communications has brought tremendous impact to people's social life. To meet the various requirements of emerging multimedia services, higher data rate should be achieved in mobile communications systems. Therefore, the anti-interference capability and enhance of system capacity become a very serious challenge. Orthogonal Frequency Division Multiplexing (OFDM) technology can transform broadband channel into many parallel orthogonal sub-channels, and thus the frequency-selective channel becomes a series of flat fading channels, so the influence of multi-path interference would be decreased. Multiple input multiple output (MIMO) technology uses multiple antennas at the transmitter and receiver, which can take advantage of multi-path propagation, thereby system capacity is increased. MIMO-OFDM that combines the advantages of MIMO and OFDM can provide higher data transfer rate.This paper focuses on the research of MIMO space division multi-access (SDMA) technology in OFDM system. First, this paper introduces the history of mobile communications briefly. Also the basic principles and the key technologies of OFDM are discussed, and the basic principles of MIMO SDMA and MIMO-OFDM are introduced. Finally, MIMO SDMA applications are studied. The existing conditions of the independent Rayleigh fading channels in MIMO systems is analyzed in this paper, and SHPAA technology is introduced into MIMO. SHPAA is a technology based on the Shannon formula and phased array antenna theory. Three-dimensional channel capacity formula for SHPAA system is presented in the paper. Simulation results show the effect of enhancing the system capacity by SHPAA technology, so SHPAA technology has important value for research and application.