Studies On Synchronization Technique Of MIMO-OFDM Systems And Its FPGA Design

With the continual development of wireless communication and broadband data service,the limited frequency spectrum resources are running short.So promoting the utilization ratio of frequency spectrum and increasing the channel capacity is becoming a work which offers many challenges.And so it will do in the future.An effective approach to increase the data rate and system capacity over wireless channels is to use multiple transmitting and receiving antennae.Systems using Multiple-Input Multiple-Output(MIMO) technique can take full advantage of space resources,convert adverse factors of multi-path into positive impacts.Space-Time Coding technique is a kind of coding technique which has already been applied in MIMO system.It obtains diversity gain and coding gain without frequency bandwidth loss.Systems which contain technique of Space-Time Coding are mainly designed for flat fading channels.However,most of channels in nature are frequency selective ones. So they must be transformed into flat channels.Orthogonal Frequency Diversity Multiplexing(OFDM) technique is just a kind of such technique..Systems which combine MIMO and OFDM technique are concerned by people because of their excellent performance.Therefore,the topic and content of this paper may offer value both in practice and theory.Firstly,the propagation characteristics and types of wireless fading channels are discussed in this paper.Then the technique of OFDM over frequency selective channels and the technique of MIMO over multi-path channels,especially,the capacity of MIMO systems are analyzed particularly. Furthermore,the principle and performance of systems which combining Space-Time coding with OFDM are presented.The synchronization of SISO-OFDM system is detailed in all aspects.Communication emulators are used to research,simulate,and contrast ML algorithm with several other algorithms over AWGN and Rayleigh channels.Two typical synchronization algorithms of MIMO-OFDM system are introduced in detail.They are Mody timing synchronization and Schenk&Zelst timing synchronization.In the end,a physics layer based on FPGA for OFDM baseband system is given.Each module of this system is also analyzed and discussed in this paper.In order to validate the correctness of the theoretical results,some simulations of MATLAB software are given in the paper.The curves of simulations are contrasted to theories.The hardware description language VHDL and IP core are applied in the models of interleaving,constellation mapping,IFFT/FFT,etc.The correctness of designing is validated by simulations of Quartusâ…¡8.1 software.