Space-Time Code Technique And Performance Study In OFDM System

Multiple Input Multiple Output (MIMO) technique and Orthogonal Frequency Division Multiplexing (OFDM) technique has been regarded as potential candidate for Fourth Generation (4G) mobile communication. As the one of the kernel parts of MIMO architecture, Space-Time Block Codes (STBC) technique is a new scheme with much potential power. STBC and STBC combined with OFDM is just the object discussed in this dissertation. The basic theory of STBC and application in OFDM mobile communication system are both studied. A general expression of instant output signal-to-noise ratio for orthogonal space-time block code over fading channel at the receiver is shown in the light of Almont's maximum likely-hood decode method . An estimate of the symbol error rate for orthogonal space-time block code is shown over Raleigh or Rice fading environment. Computer simulation results and experimental analysis prove the correctness of theoretical analysis. The principle and characteristic of STBC-OFDM system is analyzed. It is proved that various sub carrier wave is equal to some independent output branches obtained at the receiver in frequency selected fading channel using Almont's maximum likely-hood decode method . Theoretical analysis indicate that the characteristic of STBC-OFDM is influenced by the product of the number of transmitter antennas, the number of receiver antennas and the number of multi-path matrix's order. Two kinds of situation is considered on the basis the number of this product the expression of minimum distance sphere upper-bound symbol error rate of this system is also obtained. Results show that the highest possible diversity order by this system is the product of the number of transmitter antennas, the number of receiver antennas and the number of multi-path matrix's order when singnal-to-noise ratio is biggish.