Generation And Network Characterization Of High-performance Intelligent Frequency Hopping Sequences

Cognitive frequency hopping(CFH) system has the advantage of dynamic configuration, high frequency ultilization, intelligent anti-jamming and high-capacity network, which results in a higher communication reliability than conventional frequency hopping system(FH) does. As one of the key technology of the FH communication, the performance of the FH sequence, which controls the FH pattern of the FH signal, is crucial for the anti-jamming capability of the FH system. Therefore, it is essetial to study the intelligent FH sequence for the CFH system.The intelligent FH sequence should at least satisfy the following requirements: It should exhibit excellent intergrated performance to gaurantee the basic requirement of the low probability detect(LPD) and the low probability intercept(LPI); The frequency slot number could be dynamically changed, to access the channel by employing the dynamic “spectrum hold”; The frequency gap could be controlled by the FH user, to make the FH system have high anti-jamming ability for the random or hostile jamming; The intelligent FH sequence should support the high-capacity synchronous FH multiple-access(FHMA) network and low packet error asynchronous FHMA network. However, the existing FH sequences can not be used as the intelligent FH sequence, for their poor integrated perfromance and fixed parameters.This paper investigates the generation and characterization of the intelligent FH sequence including the adaptive frequency slot number FH sequence, the wide-gap FH sequence and the orthogonal FH sequence as well as the theory of synchronous and asynchronous FHMA network based on the intelligent FH sequence. The main research results are as follows:1. This paper investigates the generation of adaptive frequency slot number FH sequence to satisfy the new requirement of high dynamic intelligent communication for CFH systems. Employing an available frequency slot number varying with the real-time electromagnetic environment, the adaptive frequency slot number FH sequence is generated by pseudo-random mapping. In addition, some important conclusions about relationship between the adaptive paramters and performance of uniformity and randomness are derived in a probabilistic point of view. Simulation results show that the performance of uniformity, randomness, hamming correlation, complexity, periodicity, run path and sensitivity of the proposed FH sequence outperforms that of the widely used chaotic sequences.2. An appropriate wide-gap FH sequence could minimize the impact of jamming on CFH system. However, conventional wide-gap FH sequence adopted in CFH system performs poorly in statistical properties and FH synchronization. Therefore, we propose an algorithm named classified pseudo-random perturbation(CPRP) that can generate a random and uniform wide-gap FH sequence. In addition, the generated FH system is uniquely determined by the system status. The simulation results indicate the wide-gap FH sequence generated by the CPRP outperforms the existing wide-gap FH sequences, such as the Reed-Solomon code with dual sub-bands and the chaotic sequences with shifting replacement.3. The existing orthogonal FH sequence cannot support the high throughput and high spectrum efficient CFH network due to its small family size, high computational complexity and short period. To overcome these disadvantages, this paper proposes cyclical shift replacement(CSR) scheme. A large family size of orthogonal FH sequences is generated by employing the block cipher iteration and the orthogonal treatment. Moreover, the theoretical relationships of the throughput and transmission delay with respective to the user number and the packet arrival rate is given, and the uniformity of the generated orthogonal FH sequence is derived in a probabilistic point of view. The simulation results validate our theoretical analysis, and show that our proposed sequence outperforms the widely used no hit zone FH sequences in terms of uniformity, randomness, Hamming correlation, complexity and sensitivity, etc.4. The performance of the asynchronous FHMA network in the CFH system is also analyzed. According to the model of the CFH asynchronous FHMA network given in this paper, the theoretical expressions of packet correct transmission probability, system throughput, the frequency efficiency, network capacity and transmission delay are proposed. Moreover, we draw the conclusion of the relationship between the uniformity of FH sequence and the packet correct transmission probability and the optimal frequency slot number employed to get the maximum frequency efficiency is obtained.