Research On Key Technologies Of Indoor High Speed And Large Capacity MIMO-OFDM Receiver

Every commercial communication system must attach great importance to indoor environment coverage.How to transmit data reliably within complex indoor channel environment has always been a significant issue in wireless communication systems.OFDM technology can resist multipath effect and the effect caused by the frequency-selective fading in high-speed wireless communication systems,at the same time,it can improve spectrum efficiency as well.The receiver of wireless communication system need to implement at least two kinds of synchronization processing,namely,time synchronization and frequency synchronization.MIMO technology realizes multiple transmitting and receiving through multiple antennas,it can not only take full advantage of space resources,but also improve the channel capacity of high-speed wireless communication systems multiply.Therefore,in order to achieve considerable system capacity in complex indoor channel environment and reduce BER,it is crucial to study the key technologies of MIMO-OFDM receiver for indoor high-speed and large-capacity systems both in theoretical and practical applications.First,this paper introduces the research background and significance as well as the status about the research at home and abroad,summaries the difficulties faced by large bandwidth and high-speed data transmission receivers under complex indoor channel conditions,and then briefly introduce the basic principles,advantages and disadvantages of MIMO-OFDM technology.Based on that,the frame structure,transmitter and receiver models,and the channel model used in system simulation is presented.Following,the receiver's timing and frequency synchronization technology is studied in this paper.The first step of the receiver is frame synchronization.Considering the coarse frequency synchronization that will be carried out after,the coarse frequency offset is estimated according to the delay-related phase information at the same time of frame synchronization.Then,the existing fine timing synchronization algorithm is simulated and analyzed.In the MIMO system,these algorithms do not consider the effect of the cyclic shift.So,when the fine timing synchronization is implemented,there will be multiple peaks in the decision variables,resulting in greater error in fine timing synchronization,to solve the problem,this paper proposed an improved timing synchronization algorithm,which avoids the influence of pseudo multipath by shifting subtraction and improves the accuracy of fine timing synchronization.For precise frequency synchronization,This paper proposes an improved algorithm,ensuring the accuracy while avoiding the influence of multipath channel.Finally,the signal detection algorithm in the MIMO-OFDM system is studied,and the classical signal detection algorithms The ML detection has the best performance but the complexity is too high.Therefore,this paper studies the K-Best detection whose performance is close to the ML detection and has lower complexity,gaining the conclusion that the traditional K-Best detection only preserves K branches at every search,it is likely that the ML solution may be lost,resulting in the performance decrease.In response to the above circumstances,this paper studies the K-Best algorithm based on column norm sorting,which detects the current received spatial multiplexing signals according to sorting order by sorting operation,so that the maximum likelihood solution can be included in the path range as far as possible.Through the above operation,the ML solution is included as possible in the path range.The improved algorithm not only reduces the complexity,but also achieves more accurate signal detection as ML algorithm.