Research On Key Techniques Of Message-Driven Frequency Hopping Systems

Modern warfare is information warfare. To obtain absolute advantages in information, the army needs to ensure that their command system can seamlessly connect. A full range of all-weather reconnaissance is completed in ISR systems, where weapons can always be in contact with the operator.Hence, higher requirements in transmission rate, anti-jamming performance, spectrum efficiency and so on, are acquired for military communication system.The new message driven frequency hopping(MDFH) technique has many advantages, such as strong anti-interference ability, high spectrum efficiency, supporting multiple access and so on, which is one of the hotspots in the field of frequency hopping communication. The thesis focuses on the performance analyses and improved scheme of the enhanced MDFH. The main contents are as follows:Firstly, the basic principle of the MDFH is studied. The transmission information in the MDFH are divided into carrier bit and ordinary bit, where the carrier bit is used as subcarrier index of each hop and the ordinary bit is mapped to baseband symbol. The core concept of the MDFH system is to replace PN sequence in traditional frequency hopping system with the transmission information, which can improve spectrum efficiency and reduce synchronization burden of the system.Secondly, the operation principles of frequency hopping systems, including the traditional frequency hopping, MDFH and enhanced MDFH(EMDFH) systems are studied, and their BER performance and spectral efficiency are compared through theoretical analysis and Monte Carlo simulation. The results show that the spectrum efficiency of MDFH system is higher than that of the traditional frequency hopping system in the same channel and bit error performance, and bit error performance of the EMDFH systems is mainly decided by the carrier bit. Besides, it also shows that there are error clusters in the carrier bits and the ordinary bit which adopted high-order modulation for the EMDFH system.Thirdly, to solve the error clusters problem in EMDFH, a interleaving and code aided EMDFH improved scheme(IC-EMDFH) is proposed. At receiving end, the scheme disperses errors by using deinterleaving, and then corrects errors by convolutional decoder. Monte Carlo simulations were carried out to verify the results, it shown that the interleaving and convolutional coding can solve the clusters bit errors in EMDFH and improve the bit error rate performance of EMDFH.Finally, a synchronization scheme for the burst EMDFH system is proposed, where the preamble training pattern based on CAZAC sequence is designed, and the algorithms, including frame detection, symbol synchronization, carrier synchronization, are proposed. Through simulation the detection and estimation performance of the above algorithem evaluated, respectively, and the system error curveare also obtained under multipath environment and Gauss environments respectively. The results show that the proposed synchronization scheme can meet the system requirements of the burst EMDFH, which is suitable for the EMDFH-TDMA systems.