Passive monitoring for automated MMPP communication systems
Abstract
A recently completed study of passive sensing techniques for hf communication systems has shown that these sensing techniques can yield data which may be of use in the control of adaptive hf communication systems. The aim of this paper is to review work carried out to date on these techniques and to examine the feasibility of applying similar techniques to radio systems utilizing higher carrier frequencies, up to around 200MHz, where many propagation modes other than ionospheric skywave may exist. Whilst inputs for the control of adaptive radio systems may be derived from a number of sources, many techniques, such as pilot-tone soundings and the transmission of training sequences, involve radiation of signals which may be undesirable in a tactical situation. System control information may also be derived by monitoring other signals which are already present in related parts of the radio spectrum, allowing more covert operation and avoiding unnecessary pollution of the radio spectrum. Derivation of such control information for use in hf systems has been studied in some detail, utilizing the following types of radio signals existing in the hf band: swept frequency sounder signals radiated by other uses of the hf spectrum, broadcast signals, standard time signals, meteorological data signals (RTTY), and overall statistical occupancy measurements of the spectrum. Some of these techniques would also be applicable to the multimechanism case, provided that the more complex propagation inversion, which is due to the greater range of propagation mechanisms available, can be taken into account. Additional, higher frequency, sources of RF energy which may provide data through passive monitoring, include aeronautical navigation beacons, amateur beacons and various types of radar signals. Use may also be made of low-orbiting satellite signals, although these present tracking problems in terms of doppler shift and give data mainly related to ionospheric scintillation and hence magnetic storm effects.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- July 1994
- Bibcode:
- 1994STIN...9520927R
- Keywords:
-
- Adaptation;
- Automatic Control;
- Broadcasting;
- Carrier Frequencies;
- Frequencies;
- Propagation Modes;
- Radio Signals;
- Radio Spectra;
- Telecommunication;
- Time Signals;
- Air Navigation;
- Doppler Effect;
- Magnetic Storms;
- Meteorological Parameters;
- Radio Frequencies;
- Tracking Problem;
- Communications and Radar