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DSWM13 Switch


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#26 OFFLINE   slice1900

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Posted 02 November 2013 - 06:57 PM

My few cents:

 

The current SWiM doesn't share when two receivers are tuned to the same transponder.

The external SWiMs also have six inputs, so there is "some room" for more SATs.

 

 

I've been told current SWM shares channels by others on dbstalk, but I've never tested that, so I have no reason to doubt your statement. At any rate, there's nothing stopping the DSWM from assigning multiple receivers the same SWM channel, so long as the DSWM made the Directv channel each wants available on that SWM channel. If the SWM channel assignment to the receiver is fixed, then the DSWM would have to create its own SWM channels to do so. And it will (but not the DSWM13, see below)

 

I recently noticed Sonora had a new model of amplifier, which has 6 inputs/6 outputs like the model it is replacing, which I confess at the time made me wonder if Directv might have plans to use more inputs for RDBS, given that Sonora would undoubtedly be aware of Directv's future plans. Of course, Sonora might have left it there "just in case".

 

 

As for the DSWM, if the current thoughts hold true, it's an evolution of the current SWiM, "but" will have more of a receiver so it can decode "a channel" from the transponder. This will then be encoded [modulated] onto an RF signal and become "a SWiM channel".

Software in the receiver should be able to "fine tune" to these new frequencies, but "I doubt" we'll see 40 channels, if they're starting at 13, since this requires 13 tuners and encoders/modulators.

 

 

Well, unfortunately I have to eat my words about what I said before. I finally had time to sit down and read both patents in detail, instead of giving them a more cursory examination (i.e. skipping ahead to the end figuring that's where the good parts are) There are no tuners or modulators (even digital equivalents) in the DSWM13. The patents actually describe three (or four, depending on how you count them) embodients of a Digital SWM, which is why I should have read them in their entirety before commenting :)

 

The first is very likely what the DSWM13 is. While it is "digital" in terms of using ADCs to digitize the entire RF bandwidth being transmitted by Directv, it isn't performing any higher order digital operations. It fits 13(14) channels where 8(9) used to go, using an entire transponder at a time. Basically it uses smaller guard bands as has been previously suggested. This device is figure 4 & 5 from the patents. What I've seen elsewhere suggests it is also cheaper than current SWM due to the elimination of SAW filters.

 

Figures 4 & 6 is the second embodiment, which utilizes some higher order digital functions but still operates at the transponder level. Of note, it describes the choice of a 32 point FFT, despite a maximum [for SWM] of 26 channels, because powers of two simplify the FFT implementation. So we might reasonably expect a DSWM26 in the future utilizing the technology in Figure 6.

 

Figures 4 & 7 is the third embodiment, which is what I've been describing, but we may not see for a while. It operates not on transponders but on individual channels, computing I/Q data for each channel of interest. These can either be pasted together on the fly and converted back into analog SWM channels (with at least 100 HD channels possible from the 26 SWM channels) or can be sent via IP.

 

The patent actually lists several possibilities for this third embodiment, adding further processing of the I/Q data, to the point where it is fully demodulated. So we may have to wait until the 4th generation DSWM to get one that can work directly with RVU devices as I was suggesting. Though depending on how long it takes to get there, there may well be a competing protocol which Directv would use in preference to RVU.


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#27 OFFLINE   inkahauts

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Posted 02 November 2013 - 08:59 PM

Who knows....

Remember there was a SWM5 before a SWM8.


Ha! I still have my swim5!!!

#28 OFFLINE   inkahauts

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Posted 02 November 2013 - 09:06 PM

I've been told current SWM shares channels by others on dbstalk, but I've never tested that, so I have no reason to doubt your statement. At any rate, there's nothing stopping the DSWM from assigning multiple receivers the same SWM channel, so long as the DSWM made the Directv channel each wants available on that SWM channel. If the SWM channel assignment to the receiver is fixed, then the DSWM would have to create its own SWM channels to do so. And it will (but not the DSWM13, see below)

I recently noticed Sonora had a new model of amplifier, which has 6 inputs/6 outputs like the model it is replacing, which I confess at the time made me wonder if Directv might have plans to use more inputs for RDBS, given that Sonora would undoubtedly be aware of Directv's future plans. Of course, Sonora might have left it there "just in case".




Well, unfortunately I have to eat my words about what I said before. I finally had time to sit down and read both patents in detail, instead of giving them a more cursory examination (i.e. skipping ahead to the end figuring that's where the good parts are) There are no tuners or modulators (even digital equivalents) in the DSWM13. The patents actually describe three (or four, depending on how you count them) embodients of a Digital SWM, which is why I should have read them in their entirety before commenting :)

The first is very likely what the DSWM13 is. While it is "digital" in terms of using ADCs to digitize the entire RF bandwidth being transmitted by Directv, it isn't performing any higher order digital operations. It fits 13(14) channels where 8(9) used to go, using an entire transponder at a time. Basically it uses smaller guard bands as has been previously suggested. This device is figure 4 & 5 from the patents. What I've seen elsewhere suggests it is also cheaper than current SWM due to the elimination of SAW filters.

Figures 4 & 6 is the second embodiment, which utilizes some higher order digital functions but still operates at the transponder level. Of note, it describes the choice of a 32 point FFT, despite a maximum [for SWM] of 26 channels, because powers of two simplify the FFT implementation. So we might reasonably expect a DSWM26 in the future utilizing the technology in Figure 6.

Figures 4 & 7 is the third embodiment, which is what I've been describing, but we may not see for a while. It operates not on transponders but on individual channels, computing I/Q data for each channel of interest. These can either be pasted together on the fly and converted back into analog SWM channels (with at least 100 HD channels possible from the 26 SWM channels) or can be sent via IP.

The patent actually lists several possibilities for this third embodiment, adding further processing of the I/Q data, to the point where it is fully demodulated. So we may have to wait until the 4th generation DSWM to get one that can work directly with RVU devices as I was suggesting. Though depending on how long it takes to get there, there may well be a competing protocol which Directv would use in preference to RVU.

Ah well this makes a lot more sense IMHO in terms if a road map for the future.

I can see an entirely new system when they go to a per channel swim system. As you say out all the tuners in the swim have a box anywhere that's your DVR an not even connect it to your tv and then small clients at all tvs.

And 100? Now we are talking easy time for commercial situations.

I wouldn't be surprised if they waited for implement of this type of tech before they began shutting down mpeg2 sd.

I do enjoy fun speculation without knowing what they are really planning and for when. :)

#29 OFFLINE   P Smith

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Posted 02 November 2013 - 11:16 PM

by cursory reading, there will not be demodulation/modulation of channels; IMHO it will come to shifting and making bandwidth close to transponder's bandwidtn;

demod process is still be done by receiver's chip



#30 OFFLINE   slice1900

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Posted 03 November 2013 - 01:34 AM

Ah well this makes a lot more sense IMHO in terms if a road map for the future. I can see an entirely new system when they go to a per channel swim system. As you say out all the tuners in the swim have a box anywhere that's your DVR an not even connect it to your tv and then small clients at all tvs. And 100? Now we are talking easy time for commercial situations. I wouldn't be surprised if they waited for implement of this type of tech before they began shutting down mpeg2 sd. I do enjoy fun speculation without knowing what they are really planning and for when. :)

 

Why do you think they'd wait to do this for when they began shutting down MPEG2/SD? How would that make this any easier to implement? I would think they'd want to implement it as soon as it was ready and the cost/power was where they feel it needs to be.

 

Given that they apparently still install SD dishes for new SD only customers even now, it will be many years before they can even think about shutting down MPEG2/SD. Since the DSWM is cheaper to build than ASWM (or will be once they make it in volume) maybe it'll change the cost enough that they start installing a DSWM LNB even for new SD only installs. That's really the first step for MPEG2 retirement.

 

The per channel third embodiment sending I/Q data would let them remove tuners from all the receivers, but as you say you'd still need some sort of device somewhere to store recordings, but more importantly to provide the UI to the clients/RVU TVs.

 

Whether they would ever implement the final step in the third embodiment and do the demodulation of I/Q data in the DSWM is an interesting question. So long as they need some sort of "server" it doesn't really matter if the demodulation happens in the DSWM or in this device. Theoretically the TV could also do it, it has the hardware to demodulate ATSC and QAM, it is just a matter of programming it to handle Directv's modulation scheme. The thing is, without a server the TV would have to also have the Directv UI programmed into it for this to be useful, and unless the capability to do stuff like that was added in a future version of RVU or a similar protocol, I don't see that happening (outside of maybe a few special models created for the hotel industry)


Edited by slice1900, 03 November 2013 - 01:36 AM.

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#31 OFFLINE   slice1900

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Posted 03 November 2013 - 01:39 AM

BTW, not really related to the DSWM, but interesting nonetheless. When looking for other DSWM related patents I found various other patents Directv has filed. Most were not interesting to me, but may be to others - various features for DVRs and what not. One caught my eye. Check out patent 20130174192, "Method and system for detecting unauthorized use of a set top box using weather profiles". Yes, it is exactly what it sounds like.

 

http://www.google.co...s/US20130174192

 

Quite clever, I must say, they'd catch everyone using receivers in a second home without paying if they ever implemented this! Not to mention everyone using Directv in Canada or Mexico using a US service address.

 


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#32 ONLINE   veryoldschool

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Posted 03 November 2013 - 03:15 AM

I recently noticed Sonora had a new model of amplifier, which has 6 inputs/6 outputs...

 

Well, unfortunately I have to eat my words about what I said before....

.... While it is "digital" in terms of using ADCs to digitize the entire RF bandwidth being transmitted by Directv, it isn't performing any higher order digital operations.

The two flex ports have been around since the WB68. They were/are for the 95 & 72.5 SATs, but 72.5 isn't used anymore.

 

When speculating there will be paths that don't turn out [dead ends].

I think you're over reaching with "digitizing the entire RF bandwidth being transmitted by DirecTV".

We're dealing with a single wire [coax] and must stay in the frequency domain for more than one "signal".

 

I'm going to agree with P Smith that there is better filtering allowing the spacing of the SWiM channels to be closer.

He's posted screen shots of the current SWiM output and the spacing "can be improved" for more channels. 


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#33 OFFLINE   P Smith

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Posted 03 November 2013 - 03:30 AM

while it could be hard to send just I/Q signals of particular _transponder_  not a _channel_ (!)  (last time it's  a trend to shorten the physical path by combining a tuner with demod in one chip - see Broadcom latest chips), I would point out to an encryption of frames [see DTV patents about ACM] for AC3 aka MPEG-4 DTV transponders what would required to control demods for each tpn ... I would say not that easy as you could discuss here


Edited by P Smith, 03 November 2013 - 03:31 AM.


#34 ONLINE   veryoldschool

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Posted 03 November 2013 - 04:08 AM

I'm going to do a little "2+2" here.

I may get 3 or 5 :lol:

 

The current Entropic chip handles 3 channels.

Three chips and we have the 8 SWiM + guide.

 

A SWiM13 doesn't "add up" since with the guide it's 14.

 

"So":

Entropic's new chip handles 2 channels with digital filters.


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#35 OFFLINE   HoTat2

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Posted 03 November 2013 - 08:54 AM

OK;

 

So to summarize, look for the DSWM13 to likely use digital filtering and conversion to produce tighter spacing of the SWiM carrier channels to create more room for an additional 5 more?

 

Possibly to around 60-70 MHz spacing instead of 102 MHz?

 

That is, somewhere in the area of 9/14 x 102 MHz. 

 

But asides this, it will maintain the same traditional scheme of converting an entire transponder multiplex to a SWiM channel?  


Edited by HoTat2, 03 November 2013 - 09:08 AM.

DIRECTV sub. since Sep. of '95


#36 OFFLINE   P Smith

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Posted 03 November 2013 - 09:06 AM

when we'll have I'll post spectrograms and will do the measures (if it will fall in my hands)



#37 ONLINE   veryoldschool

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Posted 03 November 2013 - 11:06 AM

OK;

 

So to summarize, look for the DSWM13 to likely use digital filtering and conversion to produce tighter spacing of the SWiM carrier channels to create more room for an additional 5 more?

 

But asides this, it will maintain the same traditional scheme of converting an entire transponder multiplex to a SWiM channel?  

That seems about right.

The hardest thing for a tech will be the change of tuner limits. :lol:

 

Right now DirecTV requires all eight channels for a Genie install with an MDU.

It "looks like" they'll allow two on this SWiM.


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#38 OFFLINE   texasbrit

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Posted 03 November 2013 - 11:30 AM

My few cents:

 

The current SWiM doesn't share when two receivers are tuned to the same transponder.

The external SWiMs also have six inputs, so there is "some room" for more SATs.

 

 

Unless it has changed along the way, the SWM does share when two receivers are on the same transponder. I checked this some time back, after the SWM8 was released.. If you set the receivers to the same transponder, you could add more than eight tuners to an SWM8 multiswitch. I think I tried 11 on one occasion. Then as you changed the receivers to different channels, you had no problem until you had eight different transponders selected. You could also see this in the way the SWM channels were used.

Maybe the SWM LNB is different, I don't know.



#39 ONLINE   veryoldschool

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Posted 03 November 2013 - 12:07 PM

Unless it has changed along the way, the SWM does share when two receivers are on the same transponder. I checked this some time back, after the SWM8 was released.. If you set the receivers to the same transponder, you could add more than eight tuners to an SWM8 multiswitch. I think I tried 11 on one occasion. Then as you changed the receivers to different channels, you had no problem until you had eight different transponders selected. You could also see this in the way the SWM channels were used.

Maybe the SWM LNB is different, I don't know.

This doesn't match the old SWM screen.

Each tuner would get assigned a channel and it never "released" it.

You may have gotten more than eight tuners to "work" by having more than one on the same TV channel, but the SWiM itself doesn't share, or show any sign of giving up a channel when two tuners are on the same TV channel.

 

Error code 49 | Primary Tuner Connection Problem – No SWM channels are available. The receiver is unable to register tuners for Live TV or Recordings because there are too many receivers connected to the coax network


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#40 OFFLINE   gov

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Posted 03 November 2013 - 12:08 PM

Mentioned the SWM13 to a local D* installer, and he said his first thought was 8+5 is 13, so maybe the 8 part is just a SWM8 pure and simple, and the extra 5 have to go to a Genie, which has a different, compatible way of handling it's 5 extra.  He was speculating a SWM13 would not support 6 HR2Xs (12 tuners), but it might support 2 Genies (10 tuners) and an HR2X and an H2X (13 all together).

 

But he added, he had heard nothing from management, and was just guessing.

 

He also said management never tells them nuthin', but I suppose we already knew that.

 

:sure:

 

 

Sparky school for me was early 80s, so I be clueless how it works, and thankfully so.  

 

:righton:



#41 ONLINE   veryoldschool

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Posted 03 November 2013 - 12:18 PM

Mentioned the SWM13 to a local D* installer, and he said...

 

But he added, he had heard nothing from management, and was just guessing.

I think this might be an "uneducated" guess. :lol:


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#42 OFFLINE   JosephB

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Posted 03 November 2013 - 12:53 PM

Yeah, it seems if this is meant for hotels and whatnot, the 5 "bonus" tuners for the Genie wouldn't really make sense. In the end, how much more sense does this make than just using SWM-8 and SWM-16 modules? If you include the cost to develop this technology, along with the fact that there are DSPs and other more advanced technologies in this than a normal SWM, what do you get? I suppose you could modestly reduce the number of modules if you were loading racks with SWM-8s in a hotel or dorm or hospital type situation.

 

But, in an MDU it seems like this would be a bad choice. Generally one would think in a condo or apartment you're generally going to see fewer tuners per unit than single family homes, and with it being 13 tuners you now have an uneven balance if you were to split the single DSWM between two units. Plus, you have the need to isolate the MoCA networks between two units. 

 

I'm just confused why it was worth their time and money to build this when SWM8 and SWM16s are only in the range of $100, and that is the consumer cost at Solid Signal--DirecTV's cost has to be less than that. 



#43 OFFLINE   slice1900

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Posted 03 November 2013 - 01:46 PM

When speculating there will be paths that don't turn out [dead ends].

I think you're over reaching with "digitizing the entire RF bandwidth being transmitted by DirecTV".

We're dealing with a single wire [coax] and must stay in the frequency domain for more than one "signal".

 

I'm quite certain it does exactly that. I'm not sure I understand your comment about how we're dealing with single wire coax. The output of the DSWM is single wire, but the input is the same legacy input that current SWM has. It is the input it is digitizing, outputting 13 SWM channels spaced more closely than current SWM to use the same or very similar frequency range. The drawings on the patents and the description itself is very clear that it does the following:

 

We can assume the legacy portion of an LNB is unchanged, or at least any changes are not referenced in these patents. The only change mentioned in the patents is the possible addition of feedback from the DSWM to tweak the DRO (dielectric resonant oscillator, or what we call a LO) frequency to correct for LO frequency drift.

 

The input to the DSWM is 8 "LNBs". Figure 3b in the patent shows what these contain: 99 odd, 99 even, 101 odd, 101 even, 103 odd, 103 even, 119 odd, 110/119 even. That doesn't mean it would actually expect 8 cables, figure 3b represents a DSWM LNB, getting 8 traces from the legacy side to the DSWM side. When an external DSWM is connected to a legacy LNB it would still take four cables but do this splitting out internally. These 8 pathways are frequency shifted using DROs so the bottom is at near baseband (starting between 10 and 100 MHz) This is shown in the center of figure 3b in the patent - the circles with X's marked 328 are the DROs.

 

From there, the Ka pathways are split so hi and lo can be handled separately, increasing the count to 12 pathways, as shown on the left side of figure 4. All 12 pathways are passed through anti aliasing filters, high pass AA filters for Ka hi, low pass for the rest. Next ADCs perform 9 bit sampling frequencies up to 1.35 GHz, converting the full 500 MHz spectrum of all 12 pathways to digital data. It isn't specified in the drawings/patent, but it is assumed someone skilled in the art will know all 12 ADCs are part of a single DSP.

 

These outputs are inputs to the channelizers shown in figure 5, which as the first and most simple embodiment of the patent most likely represents the DSWM13. This stage creates the SWM channels by picking and choosing transponders from the 12 digitized 500 MHz bands. Thus the value of 'L' on the right side of figure 5 would be equal to 14 for the DSWM13 (13 SWM channels plus the guide channel)

 

For space reasons, on the left hand side of figure 5 only 2 of the 12 outputs from figure 4 are shown as inputs, but all 12 are actually used. There are 'k' pathways to the "select and reorder" stage for each of the 12 inputs, each pathway representing one transponder. Thus the number for 'k' will be different for the different paths, since not every 500 MHz band has the full complement of transponders active. The patent states that normally, k=16 for Ku and k=12 for Ka lo, which makes sense as the number of possible/typical odd or even transponders on Ku and Ka lo, respectively. It states that normally k=3 for Ka hi, which makes no sense, but I ascribe that to there being few Ka hi transponders being active when the patent was written. Clearly k=12 for Ka hi now for 103, and eventually for 99 when it D14 is in service.

 

The rest of the channelizer design is not documented, but given that it takes digital input from every 500 MHz band, and thus can select one or more individual transponders from any 500 MHz, then outputs stacked SWM channels on the other end I guess it is supposed to be pretty self explanatory for anyone who has understood everything up until this point ;) The "select and reorder" stage picks the required transponders containing the desired Directv channel(s), then frequency shifts them to be stacked in the SWM output. It isn't shown exactly where the conversion back to analog occurs, but probably after the circled plus so only one DAC is required to convert the whole SWM output.

 

I realize that to people not used to a DSP the idea of taking 12 500 MHz bands, each containing up to 12 or 16 transponders, and performing operations on 100+ transponders simultaneously is hard to wrap your head around, but that's exactly what this is doing. Just wait until the third embodiment, when it is doing these operations on all 1000+ Directv channels simultaneously!


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#44 ONLINE   veryoldschool

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Posted 03 November 2013 - 01:50 PM

I'm just confused why it was worth their time and money to build this when SWM8 and SWM16s are only in the range of $100, and that is the consumer cost at Solid Signal--DirecTV's cost has to be less than that. 

The SWM8 was first used for MDUs.

The design moved to LNBs as cost savings over an LNB + WB68

 

While I have no inside info.... this new DSWM might follow the same path by becoming an LNB and be cheaper than a LNB + SWM-16


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#45 OFFLINE   slice1900

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Posted 03 November 2013 - 02:03 PM

Yeah, it seems if this is meant for hotels and whatnot, the 5 "bonus" tuners for the Genie wouldn't really make sense. In the end, how much more sense does this make than just using SWM-8 and SWM-16 modules? If you include the cost to develop this technology, along with the fact that there are DSPs and other more advanced technologies in this than a normal SWM, what do you get? I suppose you could modestly reduce the number of modules if you were loading racks with SWM-8s in a hotel or dorm or hospital type situation.

 

But, in an MDU it seems like this would be a bad choice. Generally one would think in a condo or apartment you're generally going to see fewer tuners per unit than single family homes, and with it being 13 tuners you now have an uneven balance if you were to split the single DSWM between two units. Plus, you have the need to isolate the MoCA networks between two units. 

 

I'm just confused why it was worth their time and money to build this when SWM8 and SWM16s are only in the range of $100, and that is the consumer cost at Solid Signal--DirecTV's cost has to be less than that. 

 

 

There was a paper on the ASIC used in the DSWM presented at ISSCC (a conference for people presenting about state of the art circuit design...Intel will present about their new CPUs there, for instance)

 

The paper stated there were two problems with the current SWM. One, that it didn't provide enough flexibility to increase the number of inputs (reference to the RDBS bands of D14 and D15, perhaps, or maybe some plans beyond that Directv hasn't shared yet)  Two, that the SAW filters required in the design "significantly increase cost". In the patents figure 2 represents the current SWM, and 9 SAW filters are shown, one per channel. They are piezoelectric devices, not something you can shrink onto a circuit board, and I guess they must be pretty costly by comparison to integrated circuits.

 

I agree that 13 channels isn't really a big deal over 8 for MDUs, but it is still an improvement. The second generation should have 26, and the third even more, along with improvements that would provide IP output and drop the requirement for coax from DSWM to TV entirely if desired. The DSWM will be an evolution over time with regular improvements coming if they follow the path the patent lays out. So even if the DSWM13 isn't a huge improvement over the SWM8, it is just a step towards further improvements. The current SWM would always need one SAW filter per channel, limiting the cost improvement per channel that would be possible.

 

Certainly there would be no reason why anyone would want to rip out working SWM8s to replace with DSWM13s, but maybe when capacity is added DSWM13s would be added instead.

 

The cost/benefit of the DSWM13 might be hard to see at first - I'd guess they'll cost a lot more than a SWM8. That's probably why Directv is limiting it to certain markets for now, but perhaps they'll expand the market for it once they have the production cost driven down, or maybe they'll wait for the version with more channels (up to 26 would be possible in the second generation) before it sees wide deployment.


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#46 OFFLINE   slice1900

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Posted 03 November 2013 - 02:04 PM

The SWM8 was first used for MDUs.

The design moved to LNBs as cost savings over an LNB + WB68

 

While I have no inside info.... this new DSWM might follow the same path by becoming an LNB and be cheaper than a LNB + SWM-16

 

 

If the SAW filters are as expensive as the paper seems to imply, it might eventually become the standard LNB deployed in new installs, similar to the SWM LNB today.

 

I don't suppose anyone would know what SAW filters cost when purchased in quantities of a million? :)


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#47 OFFLINE   JosephB

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Posted 03 November 2013 - 02:08 PM

Down the line when it gets to the point that it's purely IP based, even from the LNB (or switch in the case of an MDU), what kind of bandwidth requirements and wiring requirements do you foresee? I'm guessing to guarantee QoS, the number of tuners supported would be determined by (speed of link)/(maximum theoretical channel bitrate)? Is there any idea at this point what that would be? IE: how many tuners would they be willing to install on a dedicated (no other traffic) 100Mb wired network?



#48 ONLINE   veryoldschool

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Posted 03 November 2013 - 02:23 PM

I'm quite certain it does exactly that.

 

I realize that to people not used to a DSP the idea of taking 12 500 MHz bands, each containing up to 12 or 16 transponders, and performing operations on 100+ transponders simultaneously is hard to wrap your head around, but that's exactly what this is doing. Just wait until the third embodiment, when it is doing these operations on all 1000+ Directv channels simultaneously!

I've read, thought, reread thought "a bunch more", over and over what you posted.

 

I think you've just described the digital filtering.

 

"In simple terms":

Analog in, frequency shift, ADC, digital filtering, DAC, frequency shift, analog out.


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#49 OFFLINE   HoTat2

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Posted 03 November 2013 - 02:24 PM

I'm quite certain it does exactly that. I'm not sure I understand your comment about how we're dealing with single wire coax. The output of the DSWM is single wire, but the input is the same legacy input that current SWM has. It is the input it is digitizing, outputting 13 SWM channels spaced more closely than current SWM to use the same or very similar frequency range. The drawings on the patents and the description itself is very clear that it does the following:

 

We can assume the legacy portion of an LNB is unchanged, or at least any changes are not referenced in these patents. The only change mentioned in the patents is the possible addition of feedback from the DSWM to tweak the DRO (dielectric resonant oscillator, or what we call a LO) frequency to correct for LO frequency drift.

 

The input to the DSWM is 8 "LNBs". Figure 3b in the patent shows what these contain: 99 odd, 99 even, 101 odd, 101 even, 103 odd, 103 even, 119 odd, 110/119 even. That doesn't mean it would actually expect 8 cables, figure 3b represents a DSWM LNB, getting 8 traces from the legacy side to the DSWM side. When an external DSWM is connected to a legacy LNB it would still take four cables but do this splitting out internally. These 8 pathways are frequency shifted using DROs so the bottom is at near baseband (starting between 10 and 100 MHz) This is shown in the center of figure 3b in the patent - the circles with X's marked 328 are the DROs.

 

From there, the Ka pathways are split so hi and lo can be handled separately, increasing the count to 12 pathways, as shown on the left side of figure 4. All 12 pathways are passed through anti aliasing filters, high pass AA filters for Ka hi, low pass for the rest. Next ADCs perform 9 bit sampling frequencies up to 1.35 GHz, converting the full 500 MHz spectrum of all 12 pathways to digital data. It isn't specified in the drawings/patent, but it is assumed someone skilled in the art will know all 12 ADCs are part of a single DSP.

 

These outputs are inputs to the channelizers shown in figure 5, which as the first and most simple embodiment of the patent most likely represents the DSWM13. This stage creates the SWM channels by picking and choosing transponders from the 12 digitized 500 MHz bands. Thus the value of 'L' on the right side of figure 5 would be equal to 14 for the DSWM13 (13 SWM channels plus the guide channel)

 

For space reasons, on the left hand side of figure 5 only 2 of the 12 outputs from figure 4 are shown as inputs, but all 12 are actually used. There are 'k' pathways to the "select and reorder" stage for each of the 12 inputs, each pathway representing one transponder. Thus the number for 'k' will be different for the different paths, since not every 500 MHz band has the full complement of transponders active. The patent states that normally, k=16 for Ku and k=12 for Ka lo, which makes sense as the number of possible/typical odd or even transponders on Ku and Ka lo, respectively. It states that normally k=3 for Ka hi, which makes no sense, but I ascribe that to there being few Ka hi transponders being active when the patent was written. Clearly k=12 for Ka hi now for 103, and eventually for 99 when it D14 is in service.

 

The rest of the channelizer design is not documented, but given that it takes digital input from every 500 MHz band, and thus can select one or more individual transponders from any 500 MHz, then outputs stacked SWM channels on the other end I guess it is supposed to be pretty self explanatory for anyone who has understood everything up until this point ;) The "select and reorder" stage picks the required transponders containing the desired Directv channel(s), then frequency shifts them to be stacked in the SWM output. It isn't shown exactly where the conversion back to analog occurs, but probably after the circled plus so only one DAC is required to convert the whole SWM output.

 

I realize that to people not used to a DSP the idea of taking 12 500 MHz bands, each containing up to 12 or 16 transponders, and performing operations on 100+ transponders simultaneously is hard to wrap your head around, but that's exactly what this is doing. Just wait until the third embodiment, when it is doing these operations on all 1000+ Directv channels simultaneously!

Wow ...

 

Thanks a much for this well written explanation. You've really helped my aging brain to understand this a lot better. Wish the patent description had been clearer on this for the main DSWiM parts as it was in quickly explaining the current ASWiM design which I grasped easily.

 

And yes I think the "k = 3" figure for the Ka-hi band is listed because D12 and of course D14 didn't exist when the patent was written and only SW1 & 2 operated in the Ka-hi band then with never greater of six (spotbeam) transponders in use.

 

3 LHCP and 3 RHCP , thus a "k" figure of only 3.


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#50 ONLINE   veryoldschool

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Posted 03 November 2013 - 02:35 PM

I agree that 13 channels isn't really a big deal over 8 for MDUs, but it is still an improvement. The second generation should have 26, and the third even more, along with improvements that would provide IP output and drop the requirement for coax from DSWM to TV entirely if desired.

The second generation would take a new receiver design, than what we have now.


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