Light-emitting diode (LED) is the major source of nonlinearity in LED communications, and the nonlinearity needs to be modelled effectively and thereby mitigated through predistortion or postdistortion to avoid degradation of communication performance. Memory polynomial is often used for LED nonlinearity modelling and mitigation in the literature. However, the estimation of memory polynomial coefficients suffers from numerical instability, resulting in inaccurate modelling and poor performance in nonlinearity mitigation. In this work, we propose an orthogonal polynomial based nonlinearity modelling and mitigation technique for LED communications with PAM signalling and show that the proposed technique significantly outperforms the conventional memory polynomial based techniques.

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In this thesis, the design, the performance and applications of jamming systems for frequency-hopped communication countermeasure based on Armored Vehicles are investigated with the background of link simulation system for communication countermeasure system in field operations and with the assistant software of MATLAB-Simulink toolbox. The design and simulation of jamming system includes waveform level and spectrum level simulation models of main entities such as a fast frequency-hopped binary frequency-shift keying (FFH/BFSK) spread-spectrum (SS) communication system and the jamming of fast frequency-hopped BFSK SS communication system, etc. The simulation can analyze the performance of the jamming methods; it can give us a new choice to make the jamming systems more useful for frequency-hopped communication which is suitable for the complex electromagnetic battlefield environment.