This paper addresses the problem of online hop timing detection and frequency estimation of multiple frequencyhopping (FH) signals with antenna arrays. The problem is deemed as a dynamic one, as no information about the hop timing, pattern, or rate is known in advance, and the hop rate may change during the observation time. The technique of particle filtering is introduced to solve this dynamic problem, and real-time frequency and direction of arrival estimates of the FH signals can be obtained directly, while the hop timing is detected online according to the temporal autoregressive moving average process. The problem of network sorting is also addressed in this paper. Numerical examples are carried out to show the performance of the proposed method.Keywords: Array signal processing, frequency hopping, FH, frequency estimation, hop timing detection, network sorting. Manuscript received Nov. 16, 2012; revised Jan. 11, 2013; accepted Feb. 2, 2013. This research was supported by the National Natural Science Foundation of China (No. 61072120), and the Program for New Century Excellent Talents in University of China (NCET).Zhi-Chao Sha (phone: +86 073184573489, shazhichao_163@163.com), Zheng-Meng Liu (zm_liur@sohu.com), Zhi-Tao Huang (taldcn@yahoo.com..cn), and Yi-Yu Zhou (zhouyiyu@shou.com) are with the College of Electronic Science and Engineering, National University of Defense Technology, Changsha, Hunan, P.R. China.http://dx.doi.org/10.4218/etrij.13.0112.0787
I. IntroductionFrequency hopping (FH) is one of the prevailing spread spectrum technologies in communications owing to its low probability of detection and interception, and vast efforts have been made to study the parameter estimation methods of such signals. Single-antenna-based methods and multiple-antennabased methods exist that can address this problem.The single-antenna-based methods exploit the temporal properties of the FH signals to estimate their parameters, such as hop rate and frequency. Chung and Polydoros proposed the methods known as multiple-hop observation autocorrelation and single-hop observation autocorrelation to estimate the hop rate and hop timing [1], [2]. The methods in [2] were further developed by Janani and others in [3] to jointly estimate the hop rate and signal power. Barbarossa and Scaglione then introduced the pseudo Wigner-Ville distribution in [4] to estimate the hop period, hop instant, and frequency. The technique of matching pursuit [5] was brought in for blind parameter estimation of FH signals by Fan and others in [6]. Ko and others focused on the estimation of the hop instant with the maximum likelihood method for network synchronization [7]. Angelosante and others focused on the estimation of the hop instant with the sparse linear regression method [8] and obtained a more satisfactory performance than when using the time-frequency distribution method.Although the above-mentioned methods are quite different in principle, they can only make use of the diversity of FH signal hop times to sort FH networks. So, these ...