Spectrally Efficient Frequency Hopping System Design forWireless Networks

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.

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 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.

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.

In this paper the bit error probability of the SFH/MFSK system in presence of wideband and tone interference in a fading environment is evaluated. Simultaneous license-free operation of tone-like applications, Frequency Hopping (FH), and Direct Sequence (DS) based LAN clusters is assumed to be the prime interference facing the subject FH wireless LAN (of the IEEE 802.11 standard). The wideband DS interference is considered to have a sinc2() shape Power Spectral Density (PSD) centered at the middle of FH signal band and tone interferers are assumed to be spread over the whole FH band of the intended signal. Assumptions of slow non-selective fading along with slow hopping justify a quasi-static treatment. Results shows that the FH system is more sensitive to tone interference and fading and less sensitive to wideband interference variations. The paper sheds light on the performance of wireless LAN operation in the unlicensed free band where many other LANs may exist.

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.

It is difficult to ensure stability and communication efficiency of traditional anti-jamming frequency hopping communication system in the frequency domain probabilistic jamming environment. Therefore, this paper proposes an adaptive frequency hopping communication scheme under probabilistic jamming. Based on the probabilistic jamming model, the practical frequency hopping (FH) strategy and average payoff is obtained using Q-Learning algorithm and is compared with the theoretical optimal average payoff obtained by the greedy algorithm. Simulation results show that our proposed algorithm is fast to converge, has fewer frequency hops compared with existing anti-jamming FH strategy, and the average payoff is close to the theoretical optimal frequency hopping strategy.

Unmanned aircraft vehicle frequency hopping (UAV-FH) systems face multiple types of jamming, and one anti-jamming method cannot cope with all types of jamming. Therefore, the jamming signals of the environment where the UAV-FH system is located must be identified and classified; moreover, anti-jamming measures must be selected in accordance with different jamming types. First, the algorithm extracts the Sevcik fractal dimension from the frequency domain (SFDF) and the degree of energy concentration from the fractional Fourier domain of various types of jamming. Then, these parameters are combined into a two-dimensional feature vector and used as a feature parameter for classification and recognition. Lastly, a binary tree-based support vector machine (BT-SVM) multi-classifier is used to classify the jamming signal. Simulation results show that the feature parameters extracted by the proposed method have good separation and strong stability. Compared with the existing box-dimensional recognition algorithm, the new algorithm not only can quickly and accurately identify the type of jamming signal but also has more advantages when the jamming-to-noise ratio (JNR) is low.

Robust frequency hop (FH) waveforms perform forward error correction coding across multiple time-frequency slots (referred to as hops). The typical assumption for FH receivers is that only one signal per hop can be recovered by the demodulator. In terms of multiple-access interference (MAI), this typically leads to one of two design choices for FH systems. One option is to mitigate MAI statistically; namely, through the use of nonorthogonal hopping. With nonorthogonal hopping, from time to time multiple users' signals occupy the same hop. Because coding is performed across many hops, this interference does not necessarily preclude correct decoding, and the corresponding performance degradation may be deemed acceptable. The advantage of this approach is that one user's hopping sequence does not depend on the hopping sequence of one or more of the other users, which reduces the required level of coordination among the users. The second option is to completely avoid MAI through the use of orthogonal hopping sequences. Such sequences ensure that at most one user signal is present in each hop, which complements the capabilities of a single-user detector, but additional coordination is required among the users.

Aiming at the problem of unsatisfactory performance of the low-density parity-check (LDPC) belief propagation decoding algorithm in the LDPC coded frequency hopping (FH) system when the interference state is unknown, an LDPC layered decoding scheme based on interference state estimation is proposed. The iterative feedback estimation mechanism is used to estimate the interference state of the hop according to the posterior message of the variable node in each hop obtained in each iteration, and then update the decoding prior probability message of the next iteration to realize the LDPC decoding under the interference state estimation Process. The simulation results show that the scheme has better decoding performance and decoding convergence. When the number of hop bits is greater than or equal to 10, the decoding performance is equivalent to the known interference state, and the complexity of the scheme is not enormous.

This paper presents the calculation of the required bandwidth of common frequency bandwidth applying queueing theory for maximizing the efficiency of frequency resource of WPAN(Wireless Personal Area Network) based Digital acoustic and communication devices. It assumed that LBT device(ZigBee) and FH devices (DCP, RFID and Bluetooth) coexist in the common frequency band for WPAN based Digital acoustic and communication devices. Frequency hopping (FH) and listen before talk (LBT) have been used for interference avoidance in the short range device (SRD). The LBT system transmits data after searching for usable frequency bandwidth in the radio wave environment. However, the FH system transmits data without searching for usable frequency bandwidth. The queuing theory is employed to model the FH and LBT system, respectively. As a result, the throughput for each channel was analyzed by processing the usage frequency and the interval of service time for each channel statistically. When common frequency bandwidth is shared with SRD using 250mW, it was known that about 35 channels were required at the condition of throughput 84%, which was determined with the input condition of Gaussian distribution implying safety communication. Therefore, the common frequency bandwidth is estimated with multiplying the number of channel by the bandwidth per channel. These methodology will be useful for the efficient usage of frequency bandwidth.

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.

In a non-cooperative frequency hopping communication system, the frequency hopping network station sorting of the received hybrid signals plays an important role and becomes an active research area in recent years. In order to solve the problem that the currently widely used clustering algorithm can not achieve satisfactory accuracy. In this paper, we propose a signal sorting method for hybrid frequency hopping network stations by applying the neural network to classify the frequency hopping description words of signals. Additionally, the conjugate gradient algorithm is utilized in the neural network training process to improve the convergence speed. Simulation results demonstrate that when compared with the clustering algorithm, the proposed algorithm converges with fewer iterations and delivers better sorting accuracy, especially in a low signal to noise ratio environment.

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

Inter-vehicle communication is an essential part of any intelligent transportation system (ITS). It allows vehicles to share surrounding road traffic information to support safe driving and road traffic management. Current systems use spread spectrum (SS) techniques: direct sequence (DS) or frequency hopping (FH). This paper proposes an implementation of a hybrid system in which DSSS and FHSS techniques are combined to provide performance and scalability improvements over a system that uses either of the SS techniques. Also this paper presents a theoretical analysis showing the improvement in the overall system capacity of the proposed system and the results of the computer simulations conducted. The results show that given an equal bandwidth, the hybrid system out performed the DS or FH systems. It showed superior bit error rate (BER) performance and scalability.