| The limited spectrum resource constraints become a bottleneck in the development of mobile communications,Therefore,to ensure the premise of reliable transmission,how to improve spectrum efficiency in the field of wireless communications become the focus of the study subjects.MIMO technology can establish a number of non-interfering and parallel subchannel between send and receive antenna;with the use of advanced multi-user detection technology,it has greatly improved forward and reverse link capacity.OFDM with a high Spectrum utilization has a very strong capability of anti-multipath interference and narrow-band interference,and it easily to combine multiple access technology.Bring the space-time coding technology and MIMO-OFDM technology in combination and play to their respective performance characteristics,which can achieve the goal of high-speed data transmission under the premise of not increasing the transmitting power and the expansion of the band.(1)The article have an in-depth study of MIMO-OFDM system synchronization technology,based on the training sequence,time synchronization algorithms such as: Schmidl&Cox algorithm,Minn&Letaief algorithm,and 802.11aWLAN symbolsynchronization and P.H.Moose frequency offset algodthm,whose's performance have been analyzed,compared and simulated.802.11 aWLAN symbol synchronization algorithm has been improved so that it will not be subject to the impact of frequency offset.In the environment of frequency offset,the improved algorithm will still be able to carry out the relevant time synchronization to sign a starting point.(2)Carrying out and analying a simulation for the MIMO channel capacity model. Introduced the synchronization error model for MIMO-OFDM system and the design principles of pre-structure for synchronization.Then,Mody&Stuber,Schenk&Zelst algorithm,which could be appliled in MIMO-OFDM,have been studied. Mody&Stuber algorithm is susceptible to multipath ISI interference,which resulting in performance degradation of Synchronization in Rayleigh fading channels.In this paper,a new MIMO-OFDM synchronization algorithm based on CAZAC training sequence has been proposed,a optimal structure of training sequence for synchronization is designed in new algorithm,which make it applicable to low-SNR Rayleigh fading channel environment.(3)The LS algorithm,MMSE and SVD algorithm in the one-dimensional pilot channel estimation is analyzed and simulated.IFFT/FFT transform domain channel estimation algorithm is studied and improved:A special channel estimation pilot frame structure is designed;The NLMS is used to filter IFFT/FFT transform domain filtering algorithms.Improved algorithm can be adaptive filter to track changes in fading channel and have a better performance than the original algofithrn.(4)Finally,Orthogonal time-domain channel estimation algorithm,which based on training sequences is researched,in order to avoid interference between the antenna,have been reaserched.Applying the algorithm to 2x2MIMO-OFDM system, using space-time coding STBC.The simulation results show that time-domain training sequence orthogonal channel estimation algorithm can effectively overcome the interference between the antenna and has a good performance. |
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