FlexACM » History » Version 6
Version 5 (GAY, Adrien, 12/15/2014 06:18 PM) → Version 6/10 (Cuadro, Juan Pablo, 12/15/2014 07:02 PM)
h1. FlexACM
FlexACM In-band signalling on the forward link:
!{width: 45%}InbandSigFW.png(FlexACM In-band signalling on the forward link.)!
FlexACM In-band signalling on the return link:
!{width: 45%}InbandSigRT.png(FlexACM In-band signalling on the return link.)!
As seen previously, the demodulator reports on the channel conditions (Es/N0 estimates) and the HUB subsequently selects the optimal MODCOD based on it. the estimation of the signal Es/N0. However, the choice of the MODCOD is not only based upon on the comparison of the Es/N0 values with the theoretical thresholds,. It also takes in thresholds as distortion of the signal has to be taken into account distortion that may be caused by non linearities (distortions from the channel or caused causes by a saturated transponder for example). examples). Moreover, we add some margin in the link budget for by safety.
Then, the MODCOD is chosen by comparing comparison of the estimated Es/N0 with the theoretical threshold of the MODCOD + the distortion + the margin, as shown in on the figure below:
p=. !{width: 60%}margins.png(FlexACM margins)!
(figure p 124 newtec user manual).
We can notice on this figure that the margin for selecting a higher MODCOD is higher than the one used to select that margin for selecting a lower MODCOD. This is advised by the constructor to create hysteresis and avoid toggling togglings of MODCODs MODCODS for specific values of Es/N0.
Distortion The distortion is estimated thanks to the proprietary a NoDE (Noise and Distorsion estimator) feature implemented in the modem, margins can be set up by the user and the table below shows the different thresholds for different the MODCODs:
p=. !{width: 30%}table.png(MODCOD thresholds)!
Note that these are the minimum Es/N0 values in order to have a quasi-error-free (QEF) transmission which ranslates into a packet error rate PER = 10 ^-5^
Table thresholds MODCOD
Once the optimal MODCOD has been estimated at the demodulator, this information is sent back to the emitter side. Two options are possible: in-band or out-band signaling. This last one does not send the signaling messages back via the satellite but use another possible links (via a terrestrial network for example); it is not the one chosen for this project. We used in-band signaling, consisting in sending the MODCOD signaling messages directly via the return channel of the satellite link as non routable encapsulated IP packets.
p=. !{width: 45%}InbandSigFW.png(FlexACM In-band signalling on the forward link.)!
FlexACM In-band signalling on the forward link
p=. !{width: 45%}InbandSigRT.png(FlexACM In-band signalling on the return link.)!
FlexACM In-band signalling on the return link
FlexACM In-band signalling on the forward link:
!{width: 45%}InbandSigFW.png(FlexACM In-band signalling on the forward link.)!
FlexACM In-band signalling on the return link:
!{width: 45%}InbandSigRT.png(FlexACM In-band signalling on the return link.)!
As seen previously, the demodulator reports on the channel conditions (Es/N0 estimates) and the HUB subsequently selects the optimal MODCOD based on it. the estimation of the signal Es/N0. However, the choice of the MODCOD is not only based upon on the comparison of the Es/N0 values with the theoretical thresholds,. It also takes in thresholds as distortion of the signal has to be taken into account distortion that may be caused by non linearities (distortions from the channel or caused causes by a saturated transponder for example). examples). Moreover, we add some margin in the link budget for by safety.
Then, the MODCOD is chosen by comparing comparison of the estimated Es/N0 with the theoretical threshold of the MODCOD + the distortion + the margin, as shown in on the figure below:
p=. !{width: 60%}margins.png(FlexACM margins)!
(figure p 124 newtec user manual).
We can notice on this figure that the margin for selecting a higher MODCOD is higher than the one used to select that margin for selecting a lower MODCOD. This is advised by the constructor to create hysteresis and avoid toggling togglings of MODCODs MODCODS for specific values of Es/N0.
Distortion The distortion is estimated thanks to the proprietary a NoDE (Noise and Distorsion estimator) feature implemented in the modem, margins can be set up by the user and the table below shows the different thresholds for different the MODCODs:
p=. !{width: 30%}table.png(MODCOD thresholds)!
Note that these are the minimum Es/N0 values in order to have a quasi-error-free (QEF) transmission which ranslates into a packet error rate PER = 10 ^-5^
Table thresholds MODCOD
Once the optimal MODCOD has been estimated at the demodulator, this information is sent back to the emitter side. Two options are possible: in-band or out-band signaling. This last one does not send the signaling messages back via the satellite but use another possible links (via a terrestrial network for example); it is not the one chosen for this project. We used in-band signaling, consisting in sending the MODCOD signaling messages directly via the return channel of the satellite link as non routable encapsulated IP packets.
p=. !{width: 45%}InbandSigFW.png(FlexACM In-band signalling on the forward link.)!
FlexACM In-band signalling on the forward link
p=. !{width: 45%}InbandSigRT.png(FlexACM In-band signalling on the return link.)!
FlexACM In-band signalling on the return link