论文标题
脉冲波形和间歇性非线性滤波在综合低SNR和秘密通信中
Pulsed Waveforms and Intermittently Nonlinear Filtering in Synthesis of Low-SNR and Covert Communications
论文作者
论文摘要
在传统的传播技术中，通过通过包含相对较低的消息的窄带信号调节宽带信号来获得宽带发射信号。在接收器中，相应的解调/剥夺将恢复信息携带的窄带信号。在本文中，我们介绍了一种替代方法，其中低速率信息直接编码为给定带宽的宽带波形，而没有载体频率的物理“扩散”。这种方法的主要优点在于用于编码信息的扩展选项，并保留对调节宽带波形的时间和振幅结构的可逆控制。显着的“多余的带宽”（需要携带信息）使我们能够使用Allpass过滤器来管理这些波形的统计属性和时间域的外观，而无需更改光谱的组成。 For example, a mixture of transmitted waveforms can be shaped as a low-crest-factor signal (e.g. to reduce the burden on the power amplifier), and/or made statistically indistinguishable from Gaussian noise (e.g. for covert transmissions and physical layer steganography), while the selected components of the received waveform can be transformed into high-crest-factor pulse trains suitable for multiplexing and/or低SNR通信。此外，控制带有低速信息的宽带波形的时间和振幅结构，可以有效利用非线性滤波技术。这些技术可用于鲁棒的实时异步提取信息，以及将光谱含量相同的宽带信号组件分离。这可以促进开发多种低SNR和秘密通信配置。
In traditional spread-spectrum techniques, a wideband transmit signal is obtained by modulating a wideband carrier by a narrowband signal containing a relatively low-rate message. In the receiver, the respective demodulation/despreading restores the information-carrying narrowband signal. In this paper, we introduce an alternative approach, where the low-rate information is encoded directly into a wideband waveform of a given bandwidth, without physical "spreading" of the carrier's frequency. The main advantages of this approach lie in extended options for encoding the information, and in retaining a reversible control over the temporal and amplitude structures of the modulating wideband waveforms. Significant "excess bandwidth" (over that needed to carry the information) enables us to use allpass filters to manage statistical properties and time-domain appearances of these waveforms without changing their spectral composition. For example, a mixture of transmitted waveforms can be shaped as a low-crest-factor signal (e.g. to reduce the burden on the power amplifier), and/or made statistically indistinguishable from Gaussian noise (e.g. for covert transmissions and physical layer steganography), while the selected components of the received waveform can be transformed into high-crest-factor pulse trains suitable for multiplexing and/or low-SNR communications. Further, control over the temporal and amplitude structures of wideband waveforms carrying low-rate information enables effective use of nonlinear filtering techniques. Such techniques can be employed for robust real-time asynchronous extraction of the information, as well as for separation of wideband signal components with identical spectral content from each other. This can facilitate development of a large variety of low-SNR and covert communication configurations.
