These days I am monitoring some signals on 5120 KHz (from Serbian-Mil) that will be the subject of a next post, and I noticed a strangeness in the use of STANAG-5066 in relation to the "way" the data are sent. The waveforms are shown in the waterfall of figure 1.
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| Fig. 1 - the waveforms into play |
As known from the "operation" of STANAG-5066, before the Data Transfer Sublayer (DTS) forwards the data, the Channel Access Sublayer (CAS) provides the functions necessary to access the physical channel (figure 2), ie the radio spectrum, assuming that the selection of the frequency (physical link setup) is handled by an external process such as ALE, in this case 188-141A. Then, a soft-link session (1) will be started immediately when there is data available for transmission to a remote STANAG-5066 node (2).
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| Fig. 2 - Physical Link Request PDUs related to the S5066 of figure 1 |
(2) A correct sequence of operations is shown in figures 3,4 (physical link request/accept, data forward, ACKs, physical link break): all managed by the STANAG-5066 sublayers that is carried by the same underlaying HF wavefrom. Notice the switch of the node address.
