Q-Learning Based Adaptive Frequency Hopping Strategy Under Probabilistic Jamming

Frequency hopping systems have been widely used in military communications to prevent hostile jamming, interception and detection. In traditional frequency hopping (FH) systems, the transmitter hops in a pseudo-random manner among available frequencies according to a pre- specified algorithm, and the receiver operates accordingly in exact synchronization with the transmitter's hopping pattern. In multiple access systems, a collision may happen when more than one users transmit in the same frequency band simultaneously. Two major limitations with the conventional frequency hopping systems are: strict requirement on frequency acquisition/synchronization, and very low spectral efficiency due to inefficient utilization of the available bandwidth. In this paper, we introduce a new concept collision-free frequency hopping (CFFH). Based on the OFDM framework and the secure subcarrier assignment algorithm, the proposed CFFH system can achieve high information capacity through collision-free multiple access, and can successfully resolve the strict synchronization limitation. At the same time, as each user still transmits through a pseudo-random frequency hopping scheme, CFFH can maintain the inherent anti-jamming, anti-interception security features of the conventional FH system. The proposed CFFH scheme can be used for both civilian and military applications where secure high speed information transmission is needed.

The integrated design for both radar and anonymous communication has drawn more attention recently since wireless communication system appeals to enhance security and reliability. Given the frequency hopping (FH) communication system, an effective way to realize integrated design is to meet the spectrum compatibility between these two systems. The paper deals with a unimodular sequence design technique which considers optimizing both the spectrum compatibility and peak sidelobes levels (PSL) of auto-correlation function (ACF). The spectrum compatibility requirement realizes anonymous communication for the FH system and provides this system lower probability of intercept (LPI) since the spectrum of the FH system is hidden in that of the radar system. The proposed algorithm, named generalized fitting template (GFT) technique, converts the sequence optimization design problem to a iterative fitting process. In this process, the power spectrum density (PSD) and PSL behaviors of the generated sequences fit both PSD and PSL templates progressively. Two templates are established based on the spectrum compatibility requirement and the expected PSL. As noted, in order to ensure the communication security and reliability, spectrum compatibility requirement is given a higher priority to achieve in the GFT algorithm. This algorithm realizes this point by adjusting the weight adaptively between these two terms during the iteration process. The simulation results are analyzed in terms of bit error rate (BER), PSD, PSL, and signal-interference rate (SIR) for both the radar and FH systems. The performance of GFT is compared with SCAN, CAN, FRE, CYC, and MAT algorithms in the above aspects, which shows its good effectiveness.

Anti-follower jamming wide gap multi-pattern frequency hopping communication method

This paper proposes a Frequency Hopping (FH) communication system with a novel frequency synthesis method. Considering that the existing frequency synthesis methods are inevitably limited by the electronic device bandwidth, a combination of directly modulated laser (DML) and optical heterodyne technique is proposed as a hopping frequency source. The principle of the method is presented and a dual frequency hopping system in E band is carried out through simulation to verified the feasibility of the proposed method. This frequency synthesis method supports high radio frequency, ultra-wideband and high hopping speed.

Frequency hopping (FH) communication has good anti-fading, anti-jamming and anti-eavesdropping capabilities, so it is one of the main ways to combat electronic jamming. In order to further improve the anti-jamming capability of FH communication, the parameters such as fixed frequency interval, hopping rate and hopping frequency in conventional FH can be assigned with time-varying characteristics. In order to set appropriate hopping parameters to improve the performance of the system in the electromagnetic environment with various types of jamming, a heuristically accelerated Q-learning (HAQL) method is proposed in this paper. Firstly, a theoretical model for the parameter decision-making of FH system is made, and the key parameters affecting the energy efficiency of the system are analyzed. Secondly, a Q-learning model in complex electromagnetic environment is proposed, which includes setting states, actions and rewards, as well as a HAQL-based decision-making algorithm is put forward. Lastly, simulations are carried out under different jamming environments, and simulation results show that the average energy efficiency of HAQL algorithm is higher than that of the SARSA algorithm, the e-greedy QL algorithm and the HQL-OSGM algorithm, respectively.

Jamming attacks have become wireless security threats disrupting reliable RF communication. Frequency Hopping Spread Spectrum (FHSS) is a widely used technique for anti-jamming wireless communications. However, FHSS relies on the pre-shared secret key between the communication pair. However, secure key exchange is challenging. Recently, Uncoordinated Frequency Hopping (UFH) schemes have been studied to achieve resilient key establishment in presence of a jammer. However, existing UFH schemes either suffer from unguaranteed rendezvous. In this paper, we introduce an Jamming-Resilient Asynchronous-Symmetric UFH scheme, AJCH, for guaranteeing rendezvous.

As Unmanned Aerial Vehicle (UAV) play a progressively important role in both military and civilian affairs, the requirements on its dependability and validity are higher and higher. In order to meet the application requirements of the UAV downlink communication system, we did the theoretical research and analysis based on the basic principles of transmission and reception of differential frequency hopping (DFH) communication systems. In this paper, for a case where the sampling frequency, hopping speed, frequency hopping bandwidth, and frequency hopping points is constant, a theoretical study about the performance analysis of the differential hopping communication systems over Rician fading channels with different fan-out coefficients, full-band jamming, partial-band jamming, and comb spectrum jamming is confirmed. On the whole, the larger the fan-out coefficient, the stronger the anti-jamming comprehensiveness of the differential frequency hopping communication system.

Accurate jamming detection in the broadband frequency hopping (FH) systems plays a vital role in improving the anti-jamming performance of the communication systems. The traditional jamming detection algorithms are prone to misjudge FH communication signals as jamming signals, leading to inaccurate jamming detection. Therefore, this paper proposes a jamming detection algorithm for broadband FH systems based on multi-segment signals spectrum clustering (MSSC). According to the difference in the time-frequency characteristics between FH signals and jamming signals, the proposed algorithm accurately detects the jamming by clustering the spectral components of signals in multiple periods. In addition, a jamming detector suitable for broadband FH systems is designed and the theoretical solution to the threshold factor of signal detection based on the Welch spectrum is also given in this paper. The simulation results show that the MSSC-based jamming detection algorithm proposed in this paper can reduce the jamming false detection probability and significantly improve the estimation accuracy of jamming parameters, effectively overcoming the defects of the traditional FFT-based energy detection and the multi-hop accumulation algorithms whose detection accuracy is sensitive to FH signals.

The cooperative combat of manned/unmanned aerial vehicle combine the advantages of both sides to enhance the combat capability to the greatest extent. The research results show that the cooperative combat of manned/unmanned aerial vehicle needs to solve the availability of the data link between fighters. In the strong interference environment, frequency hopping communication technology is used to prevent enemy electromagnetic interference. However, the traditional frequency hopping technology requires the communication parties to pre-negotiate the frequency hopping spectrum, and the fighters use the pre-negotiated frequency hopping pattern for communication. However, the research shows that it is difficult to exchange frequency hopping parameters between the two sides of the communication, and the availability of the data link is difficult to guarantee in a strong electromagnetic interference environment. Since the communication sequence of the uncoordinated frequency hopping communication can be predicted, a variable speed uncoordinated frequency hopping technique is proposed in this paper to increase the difficulty of reconnaissance and tracking of frequency hopping parameters. Next, we propose an artificial noise co-interference technology that can interfere with the channel communication quality of the enemy, but our signal reception is not affected. Furthermore, we use the zero-sum game model to analyze the electromagnetic confrontation process between the enemy and us. The experimental results show that the variable speed uncoordinated frequency hopping technique and the artificial noise co-interference technology have good anti-interference effects.

The synchronization is one of the key techniques in frequency hopping communication system. In this paper, a new synchronization scheme for high-speed frequency hopping is analyzed after analyzing synchronization in conventional frequency hopping communication system. Based on the method combined synchronization-head with time of day (TOD), the synchronization information is carried by slow-hopped pattern, and the corresponding message is carried by fast-hopped pattern, which overcomes the difficulty of correlation code transmission in fast frequency hopping. This paper mainly studies the frame of synchronization head,the synchronization of FH pattern. The performance of synchronization is analyzed and the simulation is completed by using Matlab7.0. The performance of synchronization shows that the scheme has the advantages of short synchronization time, higher probability of capture and lower false probability.

Differential frequency hopping communication system as a new concept of communication systems has become an important development direction of the current shortwave confidential communications. In this paper, on the DFH communication mechanism based on the establishment of a function, the function design m sequences designed based on HHT transform DFH signal detection design, experimental results show that this scheme can effectively achieve DFH Signal generation and detection of a communication system. KEYWORD: DFH; G function; HHT transform; detection International Conference on Social Science, Education Management and Sports Education (SSEMSE 2015) © 2015. The authors Published by Atlantis Press 710 unknown Research hopping signal detection method differential signal parameters under the conditions. 2 BASIC PRINCIPLE OF DFH The concept stems from a DFH enhanced 1995 Sandes company developed Spread Spectrum (Correlated Hopping Enhanced Spread Spectrum, called CHESS) system, CHESS radio with DFH (Differential Frequency Hopping, referred DFH) as the core technology to achieve high-speed frequency hopping, hopping speed up to 5000 hops / sec transfer rate up to 19.2kbit / s, and anti-jamming, strong anti-fading capability. DFH has two key technologies, namely signal detection technology design technology and the receiving end of a differential frequency hopping pattern. DFH system uses a new technology system, its design is based on the hopping pattern called a mathematical relationship of G function, at the sending end, the frequency value of the current time n f is by the frequency value 1 n f  and the current time data symbols n X decision. An implicit difference equation is expressed as [8]: ) , ( 1 n n n X f G f   (1) G(∙)indicates a function transform relations, referred to function. Its frequency, data transformation relationship can be expressed in the form of a diagram of transformation function in Figure 1. Fig.1 The G function transform Differential frequency hopping communication system, the receiver uses a variety of new technology to receive broadband, digital signal processing. At the receiving end, by the broadband receiving digitized, characterized by the FFT analysis of all signals within the bandwidth of the frequency hopping, 1 n f  and n f is determined. Restore the data transmitting side by the inverse transform function, namely: ) , ( 1 1 n n n f f G X    (2) Wherein G -1 denotes inverse transform function of G, which requires the function G must have reversible. Its inverse transform relationship can be expressed in the form of a diagram 2. Fig.2 The inverse G function transform 3 G FUNCTION ALGORITHM PRINCIPLE In the differential frequency hopping, G function is a specific frequency transfer function, can be seen as a directed graph, directed graph node represents a frequency point of each frequency set, each node separates 2 f  branches, BPH representative of the number of bits per hop transmission, also called the fan-out coefficients. Are marked on each bifurcation current information symbols to the set of frequencies containing frequencies of 64, for example, when each hop transmission 1bit, each node has two bifurcated (0,1). BPH transmission bit stream bits per symbols constituting a transmission symbol stream according to a given differential frequency hopping sequence with a frequency corresponding to the generated map. 3.1 1 bit G function design G function design approach are many, including those based on the theory of congruence G function design, based on the state of the shift register design function G, G function m-sequence-based design and so on. In this selection of designs based on G function m sequences. Algorithm is described as follows: Step1 First reads the data n X to be transmitted, the data is encoded, the encoded data n d is calculated.

Information communication of frequency hopping is a kind of spread spectrum in communication, it has strong anti-jamming ability, good performance of confidentiality, resistance to intercept ability and multi-user random access etc. Frequency hopping signal's spectrum is a very broad bring to unequal interval random jump, frequency hopping communication is using discrete channel. Today, the spectrum resources is shortage, in order to improve the existing spectrum utilization, cognitive radio therefore put forward the solution. The combination of cognitive radio and frequency hopping, not only improve the utilization rate of spectrum, but also improve the communication quality. This article is based on the combination of cognitive and frequency hopping, and proposed a kind of channel Information cognitive radio network channel access with good SNR selected.

FH(frequency hopping) is widely concerned in the field of communication because of its outstanding ability of noise suppression. The suppression ability of FH communication can be improved by increasing the bandwidth and hopping rate. MSK is chosen as a modulation of high-speed broadband FH communication system to research the suppression ability of FH to different noise signals. The diagram between ratio peak and ISR (interference-signal power) can be given in different bandwidths and different hopping rates. It is verified that the broadband high-speed FH communication system with MSK as the modulation mode has not only a smaller BER (bit error rate) but also a higher noise suppression.

A channel simulator that models accurately the physical channel statistics determined by the frequency separation between two carriers in frequency hopping (FH) systems is called a FH channel simulator. In this paper, a novel stochastic FH simulation model based on Rice's sum of sinusoids is proposed for wideband mobile fading channels. It is shown that a frequency hop is the physical channel model that corresponds to phase hops in the simulation model, while maintaining all other parameters unchanged. Furthermore, this simulator is capable of simulating both the fast FH and slow FH fading channel by only adjusting the phase hop rate. Due to the fact that closed-form expressions are given for all model parameters, we can study the correlation properties of the proposed simulation model from both the analytical and simulation point of view. A pretty good agreement between the correlation properties of the simulation model and those of the underlying reference model has been observed in all cases.

Unmanned aerial vehicle (UAV) systems undergo a period of rapid development in both civil and military scenarios. A major challenge in the malicious jamming environment is to guarantee the reliability of UAV communications links. Frequency hopping (FH) is one of the most commonly used means of combatting the influence brought about by jamming. In this paper, we integrate low-rate codes into an anti-jamming FH communications system, and propose an efficient and low-complexity turbo-Hadamard code scheme. Tail-biting is applied to design the component convolutional-Hadamard codes, and a corresponding decode algorithm is used for implementation in the UAV hardware platform. Numerical simulation results demonstrate that the anti-jamming performance of this method is improved as compared with conventional concatenated codes. Finally, we compare the complexity and transmission efficiency of the proposed algorithm with the algorithms implemented on the field programmable gate array (FPGA) platform in detail.