Differential Frequency Hopping System Research Articles

High-Security Sequence Design for Differential Frequency Hopping Systems

Differential frequency hopping (DFH) technique is widely used in wireless communications by exploiting its capabilities of mitigating tracking interference and confidentiality. However, electronic attacks in wireless systems become more and more rigorous, which imposes a lot of challenges on the DFH sequences designed based on the linear congruence theory, fuzzy and chaotic theory, etc. In this article, we investigate the sequence design in DFH systems by exploiting the equivalence principle between the G-function algorithm and the encryption algorithm, in order to achieve high security. In more details, first, the novel G-function is proposed with the aid of the Government Standard algorithm and the Rivest–Shamir–Adleman algorithm. Then, two sequence design algorithms are proposed, namely, the G-function-assisted sequence generation algorithm, which takes the full advantages of the symmetric and asymmetric encryption algorithms, and the high-order G-function-aided sequence generation algorithm, which is capable of enhancing the correlation of the elements in a DFH sequence. Moreover, the security and ergodicity performance of the proposed algorithms are analyzed. Our studies and results show that the DFH sequences generated by the proposed algorithms significantly outperform the sequences generated by the reversible hash algorithm and affine transformation in terms of the uniformity, randomness, complexity, and the security.

Research On LDPC-DFH Code Modulation And Demodulation System Based On Hard Decision Decoding

In order to reduce the bit error rate of differential hopping transmission, differential frequency hopping (DFH) is combined with low density parity check code (LDPC). On the basis of not adding more system complexity, the hard decision bit inversion algorithm (BF) and weighted error check based bit inversion algorithm (WVBF) are proposed to decode LDPC-DFH system. The check matrixes of different generation methods are used respectively. The BF decoding method and WVBF decoding method are used to simulate the Gaussian channel and Rician channel. The influence of different decoding methods on the bit error rate is discussed. The simulation results show that the BER of the DFH system with LDPC code is lower than that of DFH without LDPC, and the WVBF algorithm is better than the BF algorithm.

High Order Differential Frequency Hopping: Design and Analysis

This paper considers spectrally efficient differential frequency hopping (DFH) system design. Relying on time-frequency diversity over large spectrum and high speed frequency hopping, DFH systems are robust against hostile jamming interference. However, the spectral efficiency of conventional DFH systems is very low due to only using the frequency of each channel. To improve the system capacity, in this paper, we propose an innovative high order differential frequency hopping (HODFH) scheme. Unlike in traditional DFH where the message is carried by the frequency relationship between the adjacent hops using one order differential coding, in HODFH, the message is carried by the frequency and phase relationship using two-order or higher order differential coding. As a result, system efficiency is increased significantly since the additional information transmission is achieved by the higher order differential coding at no extra cost on either bandwidth or power. Quantitative performance analysis on the proposed scheme demonstrates that transmission through the frequency and phase relationship using two-order or higher order differential coding essentially introduces another dimension to the signal space, and the corresponding coding gain can increase the system efficiency.

Anti-jamming Frequency Hopping System Using Multiple Hopping Patterns

This paper deals with the follower jamming (FJ) and partial-band jamming (PBJ) resistance for the frequency hopping (FH) communication system with low hopping rate over AWGN channel. To gain a comprehensive FJ and PBJ rejection capability, we propose a multi-pattern frequency hopping (MPFH) scheme. In MPFH, the data channel and complementary channel are hopped on separate frequency slots determined by their respective frequency patterns, which will lure the follower jammer out of aiming at the complementary channel, thus mitigating the effect of FJ. Besides, narrow-band receiver is employed to ensure its PBJ rejection capability. We further enhance the proposed scheme by employing convolutional coding and maximum-likelihood decoding. Its upper bounds on bit error rate (BER) are derived under FJ and PBJ, respectively. Effects of three FJ parameters (tracking success probability, jamming duration ratio and jamming bandwidth ratio) and one PBJ parameter (jamming bandwidth ratio) on BER performance of MPFH are investigated versus the conventional FH/BFSK and recently developed differential frequency hopping (DFH) system. Numerical and simulation results show that when under the worst-case FJ, the proposed MPFH performs as well as DFH, but outperforms the conventional FH/BFSK by more than 5 dB; on the other hand, when under worst-case PBJ, the MPFH has the similar BER performance as conventional FH/BFSK, but outperforms DFH by more than 5 dB. The proposed MPFH shows superior jamming rejection performance under both PBJ and FJ.

Differential Frequency Hopping Systems Using Soft Decision Viterbi Decoding Algorithm

Differential frequency-hopping (DFH) technique has been widely studied and applied in the military communications due to its many desirable features, such as reliable high data rate transmission characteristics, anti-jamming abilities and information security. In order to improve the information security of the conventional DFH systems, a novel DFH system with the G-function controlled by the well-known maximal length sequences, is proposed in this paper. In addition, both BCH code and soft decision Viterbi algorithm are also used in the proposed scheme to further improve the system performance. Our results show that the proposed scheme not only provides the higher information security but also improves the system performance indeed, compared to the conventional schemes.

Anti-jamming performance of Fountain coded differential frequency hopping systems in AWGN

Based on the anti-jamming performance of differential frequency hopping (DFH) systems in Additive White Gaussian Noise (AWGN) channel, Fountain code is introduced to the DFH systems as the outer error correcting code in this paper to investigate the improvements against partial-band jamming over AWGN channel. The performance of Fountain coded DFH is theoretically analyzed and numerically simulated. The total frequency of hopping in the simulation is 16, and results show that, on one hand, when exact jamming state information (JSI) is available, and the number of jamming frequency is n=16, the bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> is achieved with the signal to interference ratio (SIR) approximately 7.5 dB over AWGN channel, and the performance improves about 1-1.5dB compared with the no-coded system. When the number of jamming frequency is n=2, the performance increases 15-17dB. On the other hand, when JSI is unavailable, a joint JSI estimation and decoding algorithm is proposed. The BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> is achieved with jamming-frequency n=16, SIR=8dB and signal noise ratio (SNR) 10dB over AWGN channel. It's proved that this algorithm provides robust anti-jamming performance even without JSI. The anti-jamming performance of Fountain coded DFH systems is obviously superior to no-coded DFH systems.

Improved frequency transition function construction method the differential frequency hopping system

Improved frequency transition function construction method the differential frequency hopping system

Modulated Differential Frequency Hopping System

Modulated Differential Frequency Hopping System