This sample provides an example of the use of 3G-HF (STANAG-4538) Fast Traffic Manager (FTM) protocol, which is sometimes referred to as simply FLSU (Fast Link SetUp). More precisely, FLSU is used to set up links, and it includes the traffic type that will be used immediately after the link set up is complete; FTM is used after the FLSU for cases in which the traffic type needs to be changed, or to negotiate channel access among linked stations.
As stated in S-4538 Annex-C Edition1 Amendment2, if a link has been established for delivery of packet traffic using the HDL+ data link protocol (BW7), all FTM and FLSU Protocol Data Units (PDUs) transmitted for the remaining duration of the packet link shall be transmitted using the BW6 burst waveform: thus, since the use of BW6, the link was initialized for HDL+ protocol. But, as you can see in Figure 1, at some point an FTM negotiation causes the change of the traffic type: from HDL+ (BW7 waveform) to LDL (BW3 waveform).
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| Fig. 1 - traffic type change |
It's worth noting the use of BW4 waveform bursts after LDL data delivery, it's requested by the #4.6.5 Dual Demodulation condition: "Under no circumstances shall stations be required to simultaneously demodulate more than two waveforms. Any scenario requiring more than dual-demodulation is either an error in the specification or an error in interpretation" (1).
By the way, the BW3 burst transports a L3Harris "Citadel" encrypted message (Figure 2).
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| Fig. 3 |
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(1) HDL+ states is missing in the Table 4.6.5-1: however, since BW6 burst waveform is used for Ack/EOM/Term messages, Master and Slave stations expect to receive a BW6 or a BW7 waveform.
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