R&S M3SR 4100 Series, Operating Manual

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M3SR Series 4100 SECOM-H
4.158 Operating Manual 6175.4760.02 – 01
4.8.1.2 COMSEC and TRANSEC
Communication security (COMSEC) for user and technical data is provided by ciphering be-
fore transmission and deciphering after reception:
• Ciphered voice/data transmission
• Digital voice with
- AMBE (Advanced Multi-Band Excitation) vocoder, at 2400 bit/s
- MELP (Mixed Excitation Linear Prediction) vocoder at 2400 and 600 bits/s
- MMBE (Modified Multi-Band Excitation) vocoder at 2400 and 1200 bits/s
A COMSEC key used for ciphering/deciphering the transmitted data is valid for a certain pe-
riod of time, e.g. one day.
Transmission security (TRANSEC) is provided by frequency hopping. The frequency range
is from 1.5 MHz to 29.999990 MHz. The hopping frequencies are stored in so-called
hopsets. The frequency to be used for a hop is selected pseudo-randomly by a crypto algo-
rithm, controlled by the TRANSEC key, the time, the link type and the addresses of the par-
ticipating units.
4.8.1.3 Time Synchronization
To ensure secure communication, all participating radios need to be adjusted to the same
time. This can be achieved by using GPS as time source or by manual synchronization to a
(Primary) Time Reference Unit ((P)TRU). The procedure for time synchronization of a radio
to the TRU is called Time Acquisition (TAQ). The time difference between a requesting unit
and the TRU must not be greater than five days for successful Time Acquisition. There must
not be more than one TRU in a net at any time. If the pre-configured TRU fails, any other
radio of the net can take over the TRU role when it is configured as TRU manually. Every net
uses its own net time. Time synchronization must be performed separately in every net.
R&S M3TR: If all radios in a SECOM-H net use GPS as time source, no TRU is required.
R&S EK4100 Systems can not be synchronized with the net by means of a TAQ call,
because it can not transmit the request.