OFDM waveform feature suppression

Traditional multicarrier systems developed for commercial applications use features of the waveform to improve the performance of receiver processing. These features, added in transmit processing, include, for example, a cyclic extension to mitigate inter-block interference, pilot tones inserted to assess the channel state, and specific FFT bin patterns for synchronization. An adversary can exploit these features to glean information about the transmitted waveform. The paper discusses a low probability of intercept (LPI) analysis of traditional and militarized OFDM waveforms. Militarized efforts include the elimination of the cyclic extension, pilot tones, and fixed synchronization patterns. We present an overview of the algorithms used to provide additional LPI relative to the commercial systems. In addition, traditional LPI quantitative analyses of the OFDM waveform are presented. Without adding the militarized features, the analysis shows that the OFDM waveform is rather easily detected. These analyses show the detectable features in OFDM without cyclic extension decrease as the number of subcarriers increase.