Siemens Aktiengesellschaft

Josef Brusch

Manfred Hanni

Kurt Hechfellner

A method for jam-resistant transmission speech signals by radio which have been processed via vocoders, utilizing spread spectrum multiple access modulation (SSMA) or rapid frequency hopping (FH) provides, with respect to the danger of an inherent jamming brought about when a great number of stations simultaneously use the same frequency band for the same radio channel frequency group, activation and deactivation of the transmitter and receiver at the rate of the internal system frame clock pulse during a frame clock pulse period only when useful information is present. In this manner, in the case of simplexcommunication connections, on the average approximately 40% and, in the case of duplex operation, more than 60%, of the transmitting time can be saved, and hence, the inherent jamming of the system can be reduced in a corresponding fashion.

Method for jam-resistant communication transmission

In order to achieve a good masking, together with minimum bandwidth requirement of sample values of spectral channels which are to be transmitted in the timing of consecutive analysis intervals in a time division multiplex sum signal, and of other predetermined speech parameters which likewise represent sample values, including at least one item of synchronizing information, at the transmitting end, the time-wise overlap of the sample values and of the synchronizing information are effected pseudo-randomly within consecutive frames of the sum signal and the analog sum signal obtained in this manner is transmitted across a shaping network to the receiving end, either directly in its base frequeny, or in a desired higher frequency position, or else indirectly by modulation onto a carrier.

Process for interception-protected frequency band compressed

In order to achieve a higher resistance to interference with respect to alien sources of deliberate interference in the use of communication connections via short waves, certain cooperative measures are proposed which include that the stations are equipped with highly-constant quartz crystal clocks and the bursts of information to be transmitted are accompanied by a time signal with the aid of which it is possible to correct any time tolerances between the stations. With an acknowledgment signal, use is made of a frequency variation of the radio frequency in the timing of consecutive burst transmissions including the acknowledgment response. The information contained in a burst in a fault safeguarded fashion is transmitted in coded form. The code sequence for encoding the information component and the fault safeguarding component of a burst and for the frequency address which determines the transmitting and receiving frequencies is recalculated for each burst on the basis of the clock time of the quartz crystal clock and on the basis of a subscriber number.

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Unterhaching, Germany

Josef Brusch