| Single carrier-frequency domain equalization(SC-FDE) is an effective way to combat effects of multipath channel conditions and to overcome high Peak to Average Power Ratio(PAPR) of Orthogonal Frequency Division Multiplexing(OFDM) system. SC-FDE is suitable for transmission scheme with power constrained devices. When deploying multiple antennas, SC-FDE system can further enhance the reliability of the transmission link. Many studies have focused on the multi-antenna SC-FDE system space-time code design issues in slow fading channel.Aiming at the high speed mobile communication environment represented by air-ground communication link and aiming at the short burst discontinuous transmission requirements, we have studied the MIMO-SC-FDE system with space-time code designing issues, channel estimation problems and synchronization issues. We focus on the receiver signal detection based on frequency domain equalization, space-time code design framework making full use of low complexity in FDE, pilot designing and channel estimation method adapted to the high-speed mobile environment, steady time synchronization method. The main contents of this thesis are as follows:The first chapter outlines MIMO-SC-FDE technologies briefly. Then, research status of high-speed mobile communications and key technologies are described. At the end of the chapter, we give research contents and the structure of this thesis.In chapter two, the system model for SC-FDE is described firstly and summarizes basic principle of zero-forcing(ZF) and minimum mean-square error(MMSE) equalizer. This chapter is concerned about residual inter-symbol interference problems and analyzes limitations of MMSE-RISIC. A time-frequency mixing algorithm for residual symbol interference cancellation is proposed. Under the condition of two kinds of static channel, its performance has been proved by Matlab simulation. The results show that BER performance of the proposed is better than MMSE-RISIC. Faced with short bursts transmission demands and SC-FDE system with multi-antenna space-time coding joint design, the second part of the chapter comparative studies the performance of space-time coding, cyclic delay diversity and space-frequency coding applied to SC-FDE system. The rest of chapter, we analyze three kinds of diversity technology applied to the SC-FDE system and its optimal receiving detection method. By comparing the BER performance of several diversities under the specified channel, we point out the application scenarios of different diversity technologies.In chapter three, we mainly study different channel estimation methods and pilot designing of MIMO-SC-FDE systems. Prior to this, we research common frame structure based on SC-FDE, comparing and analyzing advantages and disadvantages of different design methods in bandwidth utilization and structure. Then, we study three kinds of channel estimation methods corresponding with different frame structures, including traditional frequency-domain channel estimation, m sequence of time-domain channel estimation and unique word channel estimation method. Finally, the simulation results in static and high-speed mobile channel have shown that: traditional frequency-domain channel estimation method is not very satisfactory both in bandwidth utilization and performance. M sequence of time-domain channel estimation method ignores the interference caused by information sequence and its performance depends on the length of the m sequence. Unique word(UW) channel estimation method is mainly applied to the frame structure whose front and rear information sequence added with UW. The performance of the third method is superior to the previous at the same channel environment. According to the aforementioned simulation results, this article make further improvements on the third method based on taking the average of pilot sequences and setting threshold to reduce the error performance of the system.The fourth chapter studies synchronization technology of SC-FDE system, including symbol timing synchronization and carrier frequency offset estimation. First, an overview of the non-data-aided timing synchronization algorithm depending on cyclic prefix is presented. Then, we pay attention to several classical synchronization algorithms on the basis of auxiliary data, including Schimidl & Cox algorithm, Minn algorithm and Park algorithm. The characteristics and performance of different synchronization algorithms are verified by simulation. Finally, a symbol timing synchronization algorithm according to the frame structure is presented.In chapter five, we make a summary and point out the future research direction of MIMO-SC-FDE system. |
PDF Full Text Request