Abstract
It is challenging to detect and track frequency hopping spread spectrum (FHSS) signals due to their wideband frequencies and the limitations of current hardware. In the implementation, there has been a trend of conducting compressive sensing for blind signal processing of FHSS signals. The modulated wideband converter (MWC) is a type of sub-Nyquist sampling system, which accomplishes the recovery of highly accurate broadband sparse signals by multichannel sub-Nyquist sampling sequences. However, it is difficult to adjust MWC to FHSS signals, because the support set and sparsity change with the hop. In this paper, we propose a channelized MWC scheme in order to solve these problems. First, the proposed method distributes the sub-bands to different channels. We can derive and refresh the frequency support set rapidly without recovery. Secondly, by reconstructing the low-pass filter and decimation, we reduced the computational cost to 1/m as the traditional m-channel MWC scheme, where m is the number of channels. Moreover, we propose a series of strategies to estimate carrier frequency. The numerical simulations show that our method can detect the channel, which contains FHSS signals in the case of a low signal-to-noise ratio. Furthermore, the estimation method leads to the successful estimation of the FHSS carrier frequency. This indicates that our method is also effective in the broadband non-cooperative spectrum sensing.
Highlights
Due to its advantages, such as its strong anti-interference ability, good security and convenience for networking, the frequency hopping (FH) system has been applied in military communication, and in civilian mobile communication [1]
The advantages of the FH system are based on its wide bandwidth, randomness and paroxysms, which result in challenges to the blind reconnaissance and blind interference
In [3], an adaptive time–frequency local threshold, power-detection and time-statistic are used to remove the influence caused by the interferences and realize the blind detection of FH signals in the intricate electromagnetic environment
Summary
Due to its advantages, such as its strong anti-interference ability, good security and convenience for networking, the frequency hopping (FH) system has been applied in military communication, and in civilian mobile communication [1]. Time-frequency analysis and wavelet analysis are applied in the time–frequency domain for detection of FHSS signals [2,3,4,5,6]. These methods take advantage of the sparsity of two-dimensional distribution. Time-varying and the sampling rates of ADC can be relatively high, which satisfies the Nyquist theorem This requires a considerable amount of computations for further digital processing, especially when the communication is the form of non-cooperation. We propose methods for the detection of FHSS signals using MWC, which is based on channelization and energy detection.
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