8 May 2017

interesting paper about IP Multicasting in HF Radio Networks

I recently found in the web the interesting paper titled IP Multicasting in HF Radio Networks (2008) that proposes a multicast data link protocol for third generation (3G) high frequency (HF) radio networks:
http://mac-ee211.nmsu.edu/hf/papers/3g_mdl.pdf
I have a doubt about the "MDL Operation" paragraph and the related Figure 3 of the paper:



According to §4.6.5 "Dual Demodulation" of Annex-C to STANAG-4538 Ed.1: under no circumstances shall PUs be required to simultaneously demodulate more than two waveforms.
Well, at time "tn" in Figure 3 the receiving PUs expect an LDL_DATA PDU (BW3) or an LDL_EOM/TERM PDU (BW4): sending a FLSU PDU (BW5) would impose a triple demodulation requirement. 

Thus, the calling PU shall send an LDL_EOM PDU (BW4) to indicate that the entire datagram has been transferred and the FEC Phase 0 session is terminated; then the following FSL PDU (BW5) will be sent to announce the repetition of the datagram in the alternate FEC code:

Anyway, since the multicast scenarios proposed in the paper have been evaluated using the DoD-validated HF Network Simulator (NetSim-SC), and then not implemented in real radios, the procedure depicted in Figure 3, although wrong, could be a simplification.