Research On Space-time Coding Technique In Wireless MIMO Systems

Space-time coding(STC)technique in a wireless MIMO system improves spectral efficiency with multi-elements antenna array,it introduces the correlations in both time and space domains when signals are transmitted by different antennas,which can greatly enhance the data transmission rate and improve the performance without bandwidth expansion or transmit power augment.Thus STC has been used in 3G technique and beyond 3G as one of the key techniques.This thesis investigates several issues related to this hot topic, the main research results are as follows:(1)The basic concept and charaeteristic of MIMO channels are analyzed, and the mathematical model of MIMO channel is established.Then the formula of the capacity in the communication channels is gived and the performance is simulated.(2)The thesis analyzes four types of space-time codes.It consists of STBC(Space-Time Block Codes),DSTBC(Differential Space-Time Block Coding),LSTC(Layer Space-Time Codes)and STTC(Space-Time Trellis Codes).Then,this thesis gives the principle of encoder and decoder of these space-time codes, and analyzes the simulation results. In addition, the performance of these space-time codes is compared.(3)The STBC can provide diversity gain but can not provide coding gain,while the LDPC codes have good performance close to capacity limits and provide good coding gain. In order to get coding gain, the STBC and LDPC are concatenated in this thesis. The simulations show that the concatenation scheme can get the coding gain very well. The impact of different block length, modulation and receiving antennas number to the performance of LDPC-STBC is discussed.The results show that the performance of the concatenation scheme is improved with the growth of the block length of LDPC code and the number of receiving antennas. (4)This thesis investigates some typical application model of the Space-Time code cooperation MIMO systems.Then the thesis proposes a new scheme of cooperative diversity based on two-hop of space-time block coding decode and forward, designs a network protocol for this scheme,discusses cooperative synchronization and partner selection, and simulates the performance of this cooperative method which validates the availability of the proposed scheme.