Channel Estimation And Equalization Algorithm In OFDM Systems

Orthogonal frequency division multiplexing (OFDM) has been adopted in various wireless communication standards to exploit its high spectral efficiency and robustness against multipath fading channels. With the enhance of carrier frequency of wireless communication system and terminal mobility, time-varying characteristics of channel become more significant, therefore, to obtain accurate real-time channel information is the key to ensure OFDM system communicate reliably This paper focuses on SISO/MIMO OFDM system channel estimation algorithm, the optimal balancing algorithm and the optimum pilot pattern and sequence design, in order to improve the overall performance of the system.First, introduce the basic principles of OFDM system and the main channel estimation and equalization algorithms adopted in OFDM system currently. Then, theoretically deduce MSE minimum condition used in LS estimate of SISO/MIMO OFDM system, resulting in different channel optimal pilot distribution information. Among them, the optimal pilot tone sets of SISO-OFDM system are the sets of the equally-space tones, the number of which is equal to the symbol prefix length; And the optimal pilot distribution strategy of MIMO-OFDM system use time space orthogonal method and time space orthogonal method. Meanwhile, for MIMO-OFDM system used optimal pilot distribution, simplify its LS algorithm. Improved MMSE algorithm has lower system complexity. In addition, to enhance the system stability, selecting sequence all-one sequence as a pilot, the system has better performance under the residual frequency offset. In the system that the pilot distribution by time space orthogonal, the residual frequency offset estimation algorithm based on the pilot sequence compared to other sequences, may further optimize the system performance and reduce implementation complexity.In this paper, by setting up 2x2 MIMO-OFDM system-level simulation platform, analyzed and compared performance of different pilot distribution systems and performance of residual frequency offset estimation algorithm in the pilot all-one sequence and random sequence respectively, proved the solution proposed by this article has significant advantages.