The Research Of Space-Time Block Codes In MIMO Systems

The multiple input multiple output (MIMO) technology is an important breakthrough in the area of wireless communication, which is the key technology of the beyond 3^rd generation or 4^th generation systems. Space-time coding technology is based on MIMO systems. MIMO technology can weaken the influence of multipath fading and increase the data transmission rate and increase efficiency of frequency spectrum by space diversity. Space-time block codes (STBC) become one of the most widest researched codes, because it has the advantages such as the simple construction and low decoding complexity. The organization of this paper is as follows.(1) orthogonal space-time block code and quasi-orthogonal space-time block codeIn the paper, the channel model of the MIMO system is introduced, then Alamouti space- time code is studied, and its performance in Rayleigh-fading environments is simulated in different number of the transmit antennas with different modulation. From the simulation results we can get:(I) The bit error probability will rise with the transmission rate increasing;(II) Receive diversity can reduce the bit error probability of the system;(III) Transmitted diversity can reduce the bit error probability of the system.Quasi-orthogonal space-time block code, which is designed by Jafarkhani, is discussed. The simulation results show that the performance of quasi-orthogonal space block code has better in low SNR, but opposite in high SNR, than that of orthogonal space-time block code.(2)space-time codes based on bit-interleaved super-orthogonal designs The space-time codes based on bit-interleaved super-orthogonal designs can exist for 2,3,4 transmit antennas of rate 1,and exist for 5,6,7,8 transmit antennas of rate 3/4. Simulation results show that the bit-interleaved super-orthogonal can reduce the bit error probability of the communication system. Then the differential design of the code is discussed , and the performance of the new code is simulated.(3)space-time codes based on bit-interleaved quasi-super-orthogonal designs The space-time codes based on bit-interleaved quasi-super-orthogonal designs can exist for 2,3,4 transmit antennas of rate 1,and exist for 5,6,7,8 transmit antennas of rate 3/4, and for any number transmit antennas of rate 1/2. Simulation results show that the bit-interleaved quasi-super-orthogonal can reduce the bit error probability of the communication system. The constellation rotation design of the code is discussed, then the performance of the new code is simulated.(4)quaternion orthogonal space-time block code with multiple antennasThe channal model is constructed with the two and three transmit antennas in the rate 1,and propose to construct the new code with the codes which is discussed above and the performance of some codes is simulated. Simulation results show that the quaternion orthogonal design can reduce the bit error probability of the communication system.