This sample is a real-world example of 3G-HF Link SetUp protocol used in conjunction with a 2G MS 188-110 Serial waveform, it was copied and recordered on 9003.0 KHz/USB by my friend Mike Chace-Ortiz (mco) who kindly sent me the file.
As visible in the "NATO HF House" in Fig. 1, STANAG-4538 is located at the two lowest layers of the OSI model. The Data Link protocols at Layer two are closely connected with the burst waveforms defined in the standard and located at Layer 1 and cannot be run with other waveforms. On the other hand, link-oriented protocols, which are also located at layer two, can be run "in conjunction" with other data link protocols, for example STANAG 5066, and with waveforms at Layer 1 of the HF House such as STANAG-4285, STANAG-4539 and MIL 188-110: in this case, STANAG 4538 establishes a sort of line-switched connection which STANAG-5066 or the waveforms make use of. For example, Former Selex Communications, now Leonardo, has implemented FLSU from STANAG-4538 together with STANAG-5066 for the Swedish Armed Forces.
As visible in the "NATO HF House" in Fig. 1, STANAG-4538 is located at the two lowest layers of the OSI model. The Data Link protocols at Layer two are closely connected with the burst waveforms defined in the standard and located at Layer 1 and cannot be run with other waveforms. On the other hand, link-oriented protocols, which are also located at layer two, can be run "in conjunction" with other data link protocols, for example STANAG 5066, and with waveforms at Layer 1 of the HF House such as STANAG-4285, STANAG-4539 and MIL 188-110: in this case, STANAG 4538 establishes a sort of line-switched connection which STANAG-5066 or the waveforms make use of. For example, Former Selex Communications, now Leonardo, has implemented FLSU from STANAG-4538 together with STANAG-5066 for the Swedish Armed Forces.
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| Fig.1 - NATO HF House |
The sampleconsists of n-transmissions, each composed of a MIL 188-110A transfer running at 300bps, preceeded and terminated by BW5 bursts which control the link (Figs. 2,3):
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| Fig.3 |
More precisely, 188-110A frames transport Harris proprietary Citadel encrypted data, Fig. 4, so it's difficult to say what sits behind: S-5066 or FED-1052 (most likely the former).
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| Fig.4 |
Since the 1.033 msec length and the 50-bit payload, type "A"bursts correspond to the burst waveform 5 (BW5), as defined in STANAG-4538 (MIL 188-141C does NOT provide such waveform):
BW5 is an extended version of the BW0, it uses the same TLC, FEC, Walsh coding, and PN spreading but a longer preamble and the 50-bit payload (with increased interleaver span) make BW5 more robust than BW0. Note that the BW5 bursts that terminate each transmission, the type "C" bursts in Fig. 2, are a bit longer than the expected 1.03 msec: this is not a problem since only the first part, i.e.just 1.03msec length, contains modulated data (Fig. 6).
BW5 bursts are used to carry the PDUs of FLSU (Fast Link SetUp) and its closely associated FTM (Fast Traffic Management) protocol. PDUs for the two protocols are distinguished by the protocol field in the first three bits: 001 for an FLSU PDU versus 100 for an FTM PDU.
Unfortunately, the decode attempt of the BW5 frames, either type "A" or type "C", does not show the expected values of the first 3 bits, unless in some cases (Fig. 7). Anyway, the presence of repeated patterns could indicate a certain consistency of the data. I do not know if it's due to decoder errors or perhaps a proprietary implementation of FLSU/FTM PDU to accomplish this 3G/2G switching: for sure, since the use of the proprietary Citadel encryption, they use Harris equipment and Harris had, and still has, a preminent role in the development of 3G-HF technology (Harris was the first who implemented STANAG-4538).
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| Fig.5 |
BW5 is an extended version of the BW0, it uses the same TLC, FEC, Walsh coding, and PN spreading but a longer preamble and the 50-bit payload (with increased interleaver span) make BW5 more robust than BW0. Note that the BW5 bursts that terminate each transmission, the type "C" bursts in Fig. 2, are a bit longer than the expected 1.03 msec: this is not a problem since only the first part, i.e.just 1.03msec length, contains modulated data (Fig. 6).
| Image may be NSFW. Clik here to view.  |
| Fig.6 |
Unfortunately, the decode attempt of the BW5 frames, either type "A" or type "C", does not show the expected values of the first 3 bits, unless in some cases (Fig. 7). Anyway, the presence of repeated patterns could indicate a certain consistency of the data. I do not know if it's due to decoder errors or perhaps a proprietary implementation of FLSU/FTM PDU to accomplish this 3G/2G switching: for sure, since the use of the proprietary Citadel encryption, they use Harris equipment and Harris had, and still has, a preminent role in the development of 3G-HF technology (Harris was the first who implemented STANAG-4538).
| Image may be NSFW. Clik here to view.  |
| Fig.7 |
