Research Of Chirp Underwater Spread Spectrum Communication Technology Based On FRFT

Shallow water acoustic channel is an extremely complex radio channel, with its channel parameters in the random changes. There is a strong multipath interference, narrow bandwidth, random noise, Doppler shift and other features. To achieve reliable and efficient communication faces enormous challenges in the bad channel environment. So research a way that reliable transmission technology is essential to resist the low SNR, multipath fading and Doppler frequency shift.This paper research underwater acoustic spread spectrum communication technology based on Chirp signal, which has good noise immunity and multipath charateristics. Firstly, propose a frame synchronization structure based on Chirp signal, verify the excellent performance of frame synchronization, ensure the correct demodulation of he receiving end of the communication system. Then research the Chirp single carrier and multi-carrier modulation system based on fractional Fourier transform. And analysis of the Sweep-pread Spectrum system. Based on the above theoretical simulation of the system, the modulation and demodulation of each communication system integrated into the design Matlab GUI interface. Finally the test the communication system with noise, experiments of pool multipath and shallow water experiment, verify anti-noise performance and anti-multipath characteristics of the proposed design of communication system. The reslts represent the paper proposed spread spectrum communication system based on Chirp signal has good anti-noise and anti-multipath.The main work of this dissertation is listed below:1. The systematic introduction to the development status and overview of domestic and foreign research Chirp spread spectrum technology.2. Proposed a suitable frame synchronization structure with underwater acoustic communication, test the synchronization performance under different channel conditions by simulation.3. The introduction to Chirp spread spectrum technology, research the Chirp signal for high-end single carrier modulation technique, demodulation with the FRFT. To resist the frequency selected fading of multipath channel, proposed the Chirp spread spectrum modulation technique based on multi-carrier, the comparison and analysis to the system performance of single-carrier and multi-carrier.4. In order to solve the influence of strong multipath, research an anti-multipath Chirp Sweep-spread Spectrum system. Analyze the impact of different channel parameters to the system. And presents MFSK-Chirp sweep-spread spectrum system combined with FRFT, improve the transmission rate of system.5. On the basis of theoretical analysis and simulation test, integrate the communication into Matlab GUI interface, make the test for anti-noise, multipath pool experiments and shallow water experiment. Verify the performance of system.