||Kirtland Air Force Base, NM 871175776
|Khanh Dai Pham
At the center of covertness and survivability issues of Low-Probability-Interception (LPI) communications is the development of communication signaling techniques and signal transmission schemes that are changing courses primarily due to uncertain channel quality measurements, multi-access interferences, frequency-selective fading, partial band noise jamming, feedback delays, etc. Quantitatively speaking, it is important to investigate error performance analyses and related interpretations for M-ary-frequency-shift-keying systems employing L-hops per bit frequency hopping spread spectrum waveforms, transmitted over thermal noise plus partial-band Gaussian noise jamming channels. Performance measures should be computing processor dependent and further subject to different types of receiver processing techniques (e.g., square-law combining receiver, adaptively gain controlled square-law combining receiver, partially-jammed-hop elimination receiver, and clipped square-law combining receiver). A further concern involves hopping keystreams, which come from an end cryptographic unit at a user terminal. These frequency hopping patterns are more likely independent of channel conditions. In light of current practices, it becomes clear that the central question is then to ask whether or not L-hops per bit frequency hopping M-ary frequency-shift-keying spread spectrum systems with adaptive frequency hopping patterns ensure LPI communications more effectively (i.e., yielding of lower bit error rates, frame error rates against partial-band noise jamming under all possible operating situations)? If yes, relevant technical challenges of developing adaptive frequency hopping patterns based on imperfect channel state information (CSI), jamming state information (JSI)--in both time and frequency domains--should be of interest. On another front, yet not too far removed from covert communications, lies the possibility of research and development on the scope of properly designing waveforms for LPI applications with two set of requirements: (1) an unauthorized interceptor must not be able to detect the presence of the waveforms with probability greater than some specified small number–detection aspect; and (2) an authorized receiver can extract the information content with an acceptably low error probability–communication aspect.
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Low probability of interception communications; Frequency hopping M-ary frequency-shift-keying spread spectrum systems; Keystream generators; Waveform adaptation and coding; Maximal number of success hops; Maximal accumulated signal-to-interference-plus-jamming power ratios; Digital video-broadcasting satellite second generation; Low-density parity-check codes; Finite-length channel interleaving; Partial-band interferences; Partial-band noise and/or tone jamming; Covertness; Doppler fading;