Research Of Narrowband Interference Detection And Attenuation Based On GMSK High Speed Data Transmission System On VHF

GMSK modulation is the transmission technology using in GSM system. In recent decades, with the worldwide commercial success of the GSM system, GMSK demodulation technology is becoming more and more mature. GMSK modulation has been proved to be suitable for the mobile burst communication system with limited power, non-linear channel, multi-path fading and Doppler shift. In GSM system, however, due to the distribution of the frequency band, bandwidth limit and some other factors, interference from other wireless communication system which will deteriorate system performance inevitably. Therefore, interference suppression technology is essential for GSM system, which plays a fundamental role to the stability of the system. Narrow-band interference is one of the most destructive interference. In order to further reduce the bit error rate, it is necessary to take certain measures of narrowband interference suppression. This paper studies about the narrowband interference suppression technology including time domain linear prediction technology and frequency domain interference suppression technology, between which the former has been used more commonly.Firstly, the design of GMSK transmission system is introduced, including channel characteristics and receiver design. The concept and models of narrowband interference are also introduced.Secondly, time domain linear prediction technology and frequency domain anti-jamming technology are discussed. Specifically, on one hand, adaptive notch filter and adaptive algorithm, which applied in time domain suppression technology, are thoroughly discussed and simulated. On the other hand, the architecture of frequency domain filter and the interference threshold selection algorithm are studied. Meanwhile, Kwan-Martin algorithm and IIR trapper are introduced.Finally, research on LDPC channel coding technology is conducted. The LDPC code allows the Shannon limit to be closely approached, and also proposed efficient iterative decoding mechanisms, which can markedly reduce the bit error rate of GMSK transmission system.