Anti-jamming Solution of GPS Receiver Using Nonlinear Adaptive Predictor

W.-L. Mao, H.-W. Tsao and E-R. Chang

Abstract:	The global positioning system (GPS) can provide accurate positioning and timing information useful in many applications. Commercial aircrafts are susceptible to be jammed due to the presence of interference signal. The civil GPS receivers also have similar problems due to those intentional and non-intentional obstacles. However, it has been demonstrated that the performance of direct sequence spread spectrum system in the presence of jamming signal can be enhanced through the use of adaptive filters. In this paper, the received signal has been passed through a filter matched to the chip interval. The equivalent baseband waveforms have 3 components: GPS spread spectrum components, the additive white Gaussian noise (AWGN) and jamming signal. They are assumed to be mutually independent. Two kinds of jamming are investigated. One is single tone continuous wave interference (CWI). The other is a periodically swept CWI signal. A nonlinear adaptive predictor (NAP), which consists of two subsections: a pipelined recurrent neural network (PRNN) and a conventional tapped delay line (TDL) filter, is used to suppress the jamming signal. The PRNN is composed of M identical modules. Each module is organized by fully connected recurrent neural network with N neurons. A gradient descent learning algorithm, which minimizes the overall cost function, is adopted to update the synaptic weights. The output variables of PRNN are then fed into the tapped delay line filter in order to accomplish the one step prediction. The conventional normalized least mean square (LMS) algorithm of the linear subsection will update the adjustable weights. Simulation results show that our method can indeed achieve a superior signal-to-noise ratio (SNR) improvement relative to the conventional linear adaptive filter.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	969 - 974
Cite this article:	Mao, W.-L., Tsao, H.-W., Chang, E-R., "Anti-jamming Solution of GPS Receiver Using Nonlinear Adaptive Predictor," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 969-974.
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