Pilot Design And Channel Estimation In Multiple Antenna Systems

With the rapid development of wireless mobile communications,the MIMOOFDM technology integrated with multiple-input multiple-output(MIMO)technology and orthogonal frequency division multiplexing(OFDM)technology has become a new trend in the development of broadband wireless communication systems.The MIMO-OFDM system converts the wideband channel into multiple flat narrowband subchannels through OFDM technology,which reduces the impact of multipath fading.The MIMO technology can multiply communication system capacity and spectrum efficiency without increasing the bandwidth through multiplexing and diversity.These features,such as signal transmission stability,high transmission rate,etc.,can meet the development requirements of wireless communication.However,most of the current MIMO-OFDM systems use orthogonal pilot-aided channel estimation.With the increasing number of antennas,orthogonal pilot transmissions will cause severe spectral loss.To solve the above problems,this paper studies the non-orthogonal pilot configuration method and transceiver design problem of MIMO-OFDM systems.Specifically,this paper proposes a partial orthogonal pilot placement and sparse pilot placement scheme for a traditional MIMO-OFDM system,proposes multiple pilot transmission schemes for index modulation MIMO-OFDM systems,and further studies the design of receiver and compares them with traditional methods.The first chapter introduces the basic principles and research status of OFDM systems,frequency index modulation,airspace index modulation,MIMO-OFDM systems,and pilot-aided channel estimation techniques.The second chapter analyzes the performance of pilot-aided channel estimation in OFDM systems and compares the performance of different pilot insertion methods and common channel estimation algorithms.Then,the system model of the transmitter-receiver in the orthogonal pilot multiplexing and superposition of data and pilot in the MIMO-OFDM system is further introduced.The performance and problems of the orthogonal pilot transmission are analyzed through simulation.In the third chapter,the application of non-orthogonal pilot configuration in MIMO-OFDM systems is studied for the problem of reduced spectral efficiency due to orthogonal pilot transmission.A partial orthogonal pilot configuration scheme is proposed in this thesis.The spectrum loss caused by pilot transmission is reduced by the partial superposition between multiple sets of orthogonal pilots.Two channel estimation methods are given and compared with the traditional scheme according to the simulation results.Then,a non-orthogonal pilot configuration scheme based on sparse structure is proposed.Through the partial superposition of data and pilot sequences to improve the transmission efficiency of the system,three kinds of design of transmitter based on sparse structure and channel estimation methods are given and simulated.The fourth chapter focuses on the subcarrier and antenna sparse activation characteristics of index modulation MIMO-OFDM systems.It uses silent subcarriers and inactive antenna resources for pilot transmission,and achieves a better compromise between spectral resource loss and transmission performance.The paper firstly gives an index modulation MIMO-OFDM system model.Then,the paper presents a pilot transmission method and channel estimation method in a frequency index modulation MIMO-OFDM system.The transmitting antenna transmits each pilot sequence using quiet subcarriers,and the receiver superposes the subcarrier data in sub-blocks.Channel estimation is completed by iteratively eliminates data subcarrier interference,and compares it with existing methods.For airspace index modulation MIMO-OFDM systems,a pilot transmission scheme and channel estimation method are presented in this thesis.The transmit antenna uses the same subcarriers to transmit the pilot sequence with the silence subcarriers.The channel estimation algorithm uses different cyclic shifts through the base sequence to distinguish different antenna channels.Finally,the effectiveness and superiority of the proposed transmitter and receiver design are verified by simulation.The last chapter is a summary of the full text,describes the contribution of this article and possible future research directions.