Viasat Satellite → Re: Upload :: 12 Kbps 2 kB/s

Considering it takes some 20 minutes or so for my SB2 to "connect" after a power cycle, and assuming, as joebob42 suggested, that apparently SMTS determines an user's coding/modulation used for their SB2's uplink, then when an user's connect time takes longer on a clear day, it may be that user's SB2 unit is pre-programmed to use highest bit rate first, and then it works itself downward in coding/modulation formats until SMTS takes control of it.

If true, I'm wondering how service techs or even NRTC can evaluate which coding/modulation format is being used for coming to a judgment that a TRIA is defective. For instance, NRTC claimed in May of 2012:

...NRTC members have returned only 82 SB2 units after 90 days into shipping and so far 20 of those have been found to have problems.

Did they contact ViaSat to see SMTS data, if available, or did they just install these TRIAs for testing, and said, "see these 62 TRIAs are fit for duty?"

If these "good" 62 TRIAs were using a lower bit rate, then they were defective, and NRTC screwed the pooch. And of course, consumers who received these defective TRIAs experienced slower uplink speeds, page waits, and stall-outs.

If all true above, then SB2's diagnostics ought to show coding/modulation info, and service techs need to be educated on this topic.

Earlier in this thread you reported:

"...NRTC members have returned only 82 SB2 units after 90 days into shipping and so far 20 of those have been found to have problems."

and now you're talking about the other "62 Tria's"..

Have you confused SB2 modems that were bad with Tria's?

Good point....here's the terms they used in that article:

SurfBeam 2 (SB 2) equipment

SB 2 units

Keep in mind the author's abstraction level might suggest a clueless management person. Apparently, members of NRTC send equipment back to them, and its rather doubtful a single TRIA has not failed, statistically speaking.

In any event, my point is still valid if those conditions exist. If service tech is clueless about which coding/modulation is being used, and if TRIA can still operate at lower output power, then how can a service tech assess the situation?

Question remains...is my TRIA shooting craps, or has Exede reduced my uplink speed to a crawl during primetime.

Spice's argument vs increases in legacy speeds.

Over the last 7 years my WB modem has taken between 1 minute and more than an hour to connect after power on. There has never been a correlation between the time to connect and the speeds once connected. You argued somewhere else that the encoding and bit rate are adaptive without power cycling the modem to compensate for varying weather. It is either fixed during registration or adaptive. It can not be both.

SB2 may or may not function as WB-modem, when Gateway equipment is responsive (on-line; ready to serve you ). I recall SB2 use to connect fairly quickly, in early times.

quote:

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encoding and bit rate are adaptive without power cycling the modem to compensate for varying weather.

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A given - When SB2 is powered up, it must "listen" for its turn to transmit to SMTS "I'm here." SB2 will not transmit until it locks upon satellite signal. Consequently, there is a built in program which initiates incremental power/coding-modulation; hence, SB2 is seaching for correct transmit format to engage SMTS unit.

Via WB legacy installer manual (in which installer had to input a value) - "The maximum offset frequency in Hz, from nominal frequency, that the SM will use in its search for upstream lock.

Wildblue Legacy - I don't know if "headquarters" changed coding/modulation or not. I'd have to search literature, but in back of my mind, I seem to recall headquarters changed it...could be wrong here.

Via SB2 brochure - RETURN CHANNEL "Automatic power control and rate adaptation"

From a previous discussion - "The system has adaptive coding and modulation so the link rate will be adjusted as needed..."

I forgot to mention the "...infamous loose screw on the tria? If it is loose, it can allow moisture inside and that could certainly cause problems." 2006-01-04

To my recollections, these TRIAs were replaced in the truck load volumes, including mine, and they also had a few power-brick replacements, not mine, but I don't recall an issue with MODEMS.

Hence, I suspect the author of that news article was talking abstractly, cause TRIA replacement was the biggest issue (aka headache) back then.

Thus SB1 modem replacements has no relationship to reality back then, so I must conclude this author was expressing an abstract idea since it was TRIAs that were failing, not modems then. Using abstraction is not uncommon among management folks. Plain folks speak with concrete terms...TRIAs.

Okay, SB2 uses an adaptive bit rate controlled by the gateway. If your equipment is working properly, then the gateway is instructing your SB2 modem to upload slowly because something is broken at the gateway.

Yes, my SB1 modem used to connect faster than Windows XP booted from power on. It seldom connects that fast anymore.

Adaptive coding and modulation (ACM) was was still in research stages around 2003.

Abstract

The exploitation of adaptive coding and modulation (ACM) techniques for the forward link (satellite-to-user) of broadband communication satellites operating at Ka-band and above has been shown to theoretically provide large system capacity gains.

An over view can be found here: September 2010

Adaptive coding and modulation can be done now on a per user basis on return link to satellite and on forward link to each user.

Wilblue legacy was designed back in early 2000 time-frame; here are the specs:

Adaptive Coding and Modulation (ACM)...forward link

• Rate-adaptable return link

But, I think all users' uplink for a single beam were all the same rate, until they changed it. In other words, the forward link to users could be adjusted individually, but the return linked was fixed for all users until they change it. So, if the rain didn't blast enough users, it was "lights out" for you.

Time slots -Each user is allocated their "share" of time to uplink. As the number of active users decrease, this time slot can widen. Those user modems that are "asleep," will be polled less frequently; Wildblue Legacy modems operate this way I believe. Hence, as the time interval lengthens for active users, these users experience higher upload speeds, and generally higher download speeds.

Coding/Modulation - 8PSK 7/12 can deliver more bits per second than BPSK Rate 1/2.

8PSK and QPSK Modulation - With the addition of 8PSK modulation the DVB-S2 standard increases the bits per hz over satellite by up to 50%.