Impulse Interference Mitigation Research Based On Ica For MIMO-OFDM System

L-band Digital Aeronautical Communication System 1(L-DACS1) is based on Orthogonal Frequency Division Multiplexing(OFDM), which mainly provides high-speed voice and data communication services between aircraft and ground base station. Due to the lack of spectrum resource in L-band, L-DACS1 is deployed as an inlay system in the gaps between adjacent channels of the distance measure equipment(DME). So, the DME pulse interference signal makes the deleterious influence on the OFDM receiver of L-DACS1 inevitably. In order to solve this problem, a new DME interference suppression method is proposed in this paper based on MIMO-OFDM system and Independent Component Analysis(ICA) algorithm. The main research contents of this paper are as follows:Firstly, the characteristic parameters of physical layer in L-DACS1 system, the frame structure and the model of forward link system are introduced in details.Secondly, according to L-DACS1 system protocol specifications and the operating principle of DME, the model of DME disturbing OFDM receiver is built with Matlab. The interference is analyzed by simulation results.Finally, the model of DME pulse interference suppression on MIMO-OFDM receiver is established, transforming the problem of interference suppression into blind source separation.And ICA-only algorithm is used to separate the OFDM signal and DME impulse interference, based on the linear mixing properties in frequency domain of received signal.For the ambiguity problem after the separation of ICA, two solutions are put forward by training sequence and coding, implementing the identification, extraction and recovery of OFDM signal successfully. The computer simulation indicates that the proposed method can reduce the impact of DME interference effectively, and improve the reliability of OFDM receiver of the L-DACS1 system significantly in the case of channel information is completely unknown.