8 March 2017

3G-ALE, 2-Way Link Quality Analysis (“LQA Exchange”) example

this is surely a post of few or zero significance, just to add another over-the-air scenario of those depicted in the NATO STANAG-4538 document.
The diagram in Fig. 1 shows the procedure by which a PU can exchange SNR information for all scanned channels in both directions with a second specified PU. This is accomplished by means of a 3-way FLSU PDU exchange on each of the scan channels. The LQA Exchange, as well as other 3G-HF activity, has been copied on 10132.0 KHz/USB (sunday morning, 1019 UTC) in the reserved WARC band of 30mt.  

Fig. 1
When a PU is given a request for an LQA Exchange with another PU, it sends a FLSU_Req PDU on the next scan channel on which it is able to. The FLSU_Req PDU includes the caller PU address and called PU address, and is of type REQUEST_2Way.
The called PU estimates the SNR of the received FLSU_Req PDU and reports the channel quality back to the caller PU by responding with an FLSU_Conf PDU on the same channel. The caller PU, on its turn, estimates the SNR of the FLSU_Conf PDU and reports it back to the called PDU through an FLSU_Term PDU that terminates the 3-way exchange.

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