Abstract
The chaotic direct sequence spread spectrum (CD3S) is one of the distinguished techniques providing physical layer secrecy and low probability of intercept (LPI) in wireless communication. Due to the noise-like and aperiodic characteristics of chaotic signals, the synchronization of CD3S signals is a challenging issue. A synchronization approach for aperiodic CD3S signals based on bidirectional correlation search (BDCS) is proposed. Through a joint acquisition of forward frequency domain matched filtering (FDMF) and backward FDMF, the synchronization module aligns received CD3S signals with local chaotic sequences without aid of the pilot signal. The probability distribution of correlator output is derived with additive white Gaussian noise and narrowband jamming. The probability of detection, probability of false alarm, and bit error rate are analyzed mathematically. An approximate solution of the local optimal acquisition threshold coefficient is obtained. These theoretical analyses are verified by numerical simulations, the results of which demonstrate that the proposed synchronization approach enables the CD3S system to resist interception and adapt to the environment with low signal-to-noise and signal-to-jammer ratios.
Highlights
Chaotic signals have attracted much attention in the field of secure communication due to their several distinct characteristics such as sensitivity to initial conditions, aperiodicity, and random-like behavior [1]-[4]
In order to construct a CD3S system with low intercept probability and anti-jamming capacity, this paper proposes a synchronization approach based on bidirectional correlation search (BDCS)
In order to construct a CD3S system with low intercept probability and anti-jamming capacity, the paper proposed a synchronization approach based on BDCS
Summary
Chaotic signals have attracted much attention in the field of secure communication due to their several distinct characteristics such as sensitivity to initial conditions, aperiodicity, and random-like behavior [1]-[4]. In the semi-blind demodulation approach, the receiver can demodulate the message bits without locally generating the same chaotic sequence as the transmitter. In the semi-blind demodulation approach, the transmitted signals have a low probability of intercept because each message bit is spread by a unique chaotic sequence. In order to construct a CD3S system with low intercept probability and anti-jamming capacity, this paper proposes a synchronization approach based on bidirectional correlation search (BDCS). For the CD3S system with aperiodic chaotic code, this approach can only complete the acquisition when the received signal lags behind the local spreading sequence. The received signal may lead or lag behind the local chaotic sequence, the acquisition approach of DSSS system is not applicable to CD3S system.
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