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Digital SWM theory and speculation


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236 replies to this topic

#1 OFFLINE   Stuart Sweet

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Posted 23 December 2013 - 04:21 PM

This thread is devoted to the theory of Digital SWM technology. All participants need to be aware that any technologies represented here may or may not ever appear in any DIRECTV product and are, at the moment, pure speculation. As always, it's fun to imagine, but for real-world applications of Digital SWM technology, visit this thread: http://www.dbstalk.c...and-discussion/

Further, because this thread contains total and complete speculation, it's not off-limits to imagine anything happening with Digital SWM technology, so long as no person represents him or herself as being able to know the future.
Opinions expressed by me are my own and do not necessarily reflect
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#2 OFFLINE   slice1900

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Posted 23 December 2013 - 04:23 PM

DSWM (Digital Single Wire Multiswitch) is Directv's implementation of what is generally referred to in the satellite industry as dCSS (digital Channel Stacking Switch) At least three dCSS implementations exist as products, which are all capable of DSWM functionality. The industry appears to have settled on 24 output channels as a standard. Subtracting the one Directv dedicates to the guide, this would permit as many as 23 channels per output, unless Directv chooses to limit the number of channels below that.

 

Directv listed some goals for DSWM in both their patent and the paper describing the implementation of that patent. Cost reduction through elimination of expensive analog components, particularly SAWs. Increased flexibility to handle "many more satellites", which likely refers to a single product for US and non-US markets. More output channels. Cost savings by eliminating parts from IRDs (i.e. some parts of up to the entire tuner) Enabling "future products", for "Home Gateway or MDU architectures".

 

Directv's current DSWM products, the DSWM13 switch and SWM 13 LNB utilize the same starting frequency of 974 MHz, with channel spacing exactly half that of the analog SWM, 51.03 MHz versus 102.06 MHz. This was a deliberate choice, and presumably must have been done to permit some forwards and/or backwards compatibility between ASWM and DSWM, but the full extent of such compatibility is not yet known.

 

 

Current DSWM products:

 

DSWM13 (Directv multiswitch) http://www.dbstalk.c...and-discussion/

This is a specialized product targeted at a specific market for hotels, and cannot be used outside of that market. It is limited to 13 channels on a single high powered output for reasons specific to its application. The DSWM13 uses Entropic's EN5400 chip. The DSWM13 is manufactured by WNC.

 

SWM LNB 13 (Directv LNB) http://www.dbstalk.c...ook-swm-13-lnb/

This is a general purpose product targeted at residential and commercial installs with a requirement for up to 13 tuners. It isn't known for sure why it was limited to 13 tuners, but may have to do with difficulties maintaining signal strength when split a number of ways (particularly when DECA is involved) as well as the likelihood that a comparatively tiny number of Directv residential customers have more than 13 tuners. It isn't yet known what chip this uses, but it is likely the EN5500. If that is the case, then this LNB very likely supports RDBS reception.

 

 

Current implementations of dCSS:

 

EN5400 (Entropic Communications) http://www.entropic....oor-unit/en5400

14 500MHz input bands, 20 channels. The existence of at least one competitor was mentioned but not named during Entropic's Q4 2013 earnings call. The EN5400's technology was originally developed by Teranetics under contract by Directv, it was acquired and completed by PLX Technology, then acquired by Entropic, along with the engineers who designed it, in 2012. This is the only dCSS known to be used in current Directv products.

 

EN55x0 (Entropic Communications) http://www.entropic....oor-unit/en5500

The EN5500/EN5510/EN5520 have six/seven/four 250-2350 MHz inputs, with one, three and two 24 channel outputs, respectively. Announced and sampling in April 2014. The EN5500 family is designed for worldwide use, which would account for the slightly higher top end frequency. Entropic claims it is the lowest power dCSS chip available, which allows it to be powered by receivers instead of external power inserter, but such a capability may not be utilized by Directv. The EN5500 was designed by Mobius Semiconductor, and it and the engineers who designed it were acquired by Entropic in 2013.

 

BCM4551 (Broadcom) https://www.broadcom....php?id=s817469

8 250-2350 MHz inputs, 24 channels, built in 28nm CMOS. Designed for worldwide use, allowing both DiSEqC and FSK control.

 

MxL86x (MaxLinear) http://www.maxlinear...m-capture-socs/

MxL865 has 5 250-2350 MHz inputs, 24 channels. MxL868 has 8 950-2150(?) MHz inputs, 3 outputs capable of 24 channels each. Designed for worldwide use, allowing both DiSEqC and FSK control. Maxlinear has announced design wins with Zinwell and Eagle Aspen to use the MxL865, with plans to deliver the chips in Q4 2014, but there is no way to know whether either has anything to do with Directv.

 

unknown name (NXP Semiconductor) http://dx.doi.org/10...CC.2013.6487719

14 500 MHz input bands, 24 channels. NXP was contracted by Directv to design this ASIC, presumably as proof of concept or for internal testing, as there is nothing to suggest it will ever be used in a product. Figures of merit for the ADCs such as ENOB and SQR exactly match those of the second embodiment in Directv's DSWM patent, demonstrating the patent was written based on the design/implementation of this ASIC. It was probably a proof of concept, and may actually be the same chip Directv designed with Teranetics that became the EN5400.

 

 

Links of interest:

 

Analog SWM (US 20060277578 A1)  http://www.google.co...s/US20060277578

RF Magic's patent application that describes Directv's current SWM. RF Magic was later acquired by Entropic Communications, who produces the RF5201 ASWM chip used in all current SWM products.

 

Digital SWM (US8238813)    http://www.google.co...tents/US8238813

Directv patent which describes digital SWM technology from their DSWM ASIC. Figure 6 shows the second embodiment, which exactly matches the implementation described in the paper. Rather than splitting up the signal to individual choose and frequency shift transponders of known size/spacing one at a time as the ASWM does, higher order digital functions allow operating on groups of transponders. The transponders need not have uniform width or spacing, so it can handle Directv's US and non-US satellites equally well.

 

Digital SWM LNB frequency drift estimation/correction (US8509722)    http://www.google.co...tents/US8509722

Directv patent that describes using the DSWM ASIC's DSP to estimate and correct for LO frequency drift (due to temperature or age) in a DSWM LNB, sensing deviations and correcting for it by adjusting the frequency of the DRO (i.e. LO) Additional diagnostic outputs can be generated which aid installation, troubleshooting, etc.

 

Digital Single Wire Multiswitch ASIC (paper from Feb 2013 ISSCC)    http://dx.doi.org/10...CC.2013.6487719

Describes a 45nm 7 metal layer + RDL CMOS implementation of the DSWM ASIC. The die area is not stated in the paper, but based on a die micrograph would estimate it at around 30 sq mm. The paper and associated materials detail 14 input bands in the 250-760 MHz range, 24 output channels, 9.4 watts maximum dissipation.

 

Maxlinear's dCSS (US20130205349 A1)  http://www.google.co...s/US20130205349

Maxlinear's patent application. Probably describes or is similar to the MxL86x family.

 

Mobius Semiconductor's dCSS (US20120189084 A1)  http://www.google.co...s/US20120189084

Mobius Semiconductor's patent application. Mobius Semiconductor was acquired by Entropic Communications in 2013, this likely describes or is similar to the EN5500. See the writeup for Figure 10 for the description of the embodiment related to Directv.


Edited by slice1900, 14 September 2014 - 05:46 PM.

SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#3 OFFLINE   P Smith

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Posted 23 December 2013 - 04:25 PM

I would ask Mods to move many posts from original DSWiM13 thread to here; all of them contain speculations, theories, etc what would be make the thread is full of relevant posts



#4 OFFLINE   veryoldschool

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Posted 23 December 2013 - 04:27 PM

This thread is devoted to the theory of Digital SWM technology.

In which the basics are a change from analog filtering to digital filtering. This allows for closer spacing of the output channels.


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#5 OFFLINE   Stuart Sweet

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Posted 23 December 2013 - 04:29 PM

My apologies, no posts will be moved to this thread as we don't have the ability to change their post dates and there are known issues with moving posts older than the starting time of the thread. Feel free to copy and paste.
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#6 OFFLINE   slice1900

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Posted 23 December 2013 - 04:30 PM

Replying to inkahauts' post from the DSWM13 thread.

 

But see that's the spot i tend to disagree looking forward three years from now. By then I expect HR24 to become no recover like the HR20 etc. when that happens we will be left with just genies. I have to believe by then they will allow Multiple genies if not sooner anyway. They really could use a lower cost solution for more than 10 channels than a swim16 once that happens IMHO. That gives them three years before it could become a Mainstream issue by my guestimate. While the number of people wanting two genies now likely is small the number if people wanting two DVRs in general is probably higher IMHO significantly. Not a exorbananr amount either way but enough that could Make them want to move to a larger swim. Also porting this to mdu makes sense as well at some point if the cost savings is there. And then my question becomes relevant again. You don't need that kind of power for mdu either correct? Again my question was simply does Dswim actually require higher output as the nature of the beast or is it pumped up do to its actual needs for its specific use in this specific product. Granted I doubt we know for sure. Hopefully we will know latter next month.

 

Everything will become non-recoverable, eventually. But what makes you think they won't keep making DVRs with two tuners? Or that they won't make a new Genie with even more than 5 tuners? They haven't released a new dual tuner DVR since the HR24, but that doesn't mean they never will.

 

Directv would clearly benefit from having a single wire LNB that supports more than 8 tuners, since they hit that limit more often, and that trend seems likely to continue. I doubt anyone would dispute that. However, a DSWM LNB doesn't make sense until it costs them less to install than a legacy LNB, four coax, and SWM16. We can make some pretty good estimate of what the SWM16 solution costs, but can only guess at the cost of a DSWM LNB, or if there are some issues that need to be worked out before that's something they can offer at all, or ever.

 

There's nothing inherent in the DSWM technology itself that requires a higher output. It is doing A to D and then D to A conversion, and the D to A output doesn't require high levels, and even if it did there's no reason they couldn't be attenuated as necessary. Likewise, there's nothing inherent in the analog SWM technology that requires the specific output level it uses. That's determined by the AGC amp at its output. If they had wanted the SWM8 to output at -20 dbm or -40 dbm, they would have chosen the AGC amp and its settings to produce that output.

 

It isn't a matter of "porting" DSWM13 to MDU or the home market. They won't so much use a DSWM13 as a starting point as they'll use the DSWM ASIC as a starting point. Undoubtedly it would share a good portion of its design with that of the DSWM13, but certain things would be different, such as the output level and the number of channels. Once the exact frequencies being used in the DSWM13 are made public, we should have a better idea of what the maximum number of channels the DSWM ASIC inside of it is capable of. From the information I have so far it looks like that ASIC is capable of a maximum of either 15 or 22 channels. A different implementation of the DSWM (i.e. a new ASIC built in a different process) could have different channel spacing from the ASIC used in the DSWM13, of course.


SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#7 OFFLINE   slice1900

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Posted 24 December 2013 - 12:51 AM

I updated my post #2 with links to the patents & paper, along with a synopsis of what the patent describes as I understand it. Corrections for typos, additions, or something you think I'm misreading/misunderstanding appreciated!


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#8 OFFLINE   P Smith

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Posted 24 December 2013 - 01:39 AM

..

Thus there are 10 such bands for a SL3 LNB and 12 for a SL5 LNB. .

Please explain details of the numbers by sat/pol/etc


Edited by P Smith, 24 December 2013 - 01:39 AM.


#9 OFFLINE   HoTat2

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Posted 24 December 2013 - 03:17 AM

Please explain details of the numbers by sat/pol/etc

AIUI P. Smith, the DSWM as described by the patent breaks down the conventional 250-750 MHz, 950-1450 MHz, 1650-2150 MHz triple 500 MHz band LNBF converted transponder band stack into 12 separate 500 MHz bands, each with a beginning frequency selected somewhere in the 10-100 MHz range, thus;

 

For the SL-5;

 

99W

 

1) LNBF 1 - Ka-lo LHCP

2) LNBF 1 - Ka-hi LHCP

3) LNBF 2 - Ka-lo RHCP

4) LNBF 2 - Ka-hi RHCP

 

101W

 

5) LNBF 3 - Ku LHCP

6) LNBF 4 - Ku RHCP

 

103W

 

7) LNBF 5 - Ka-lo LHCP

8) LNBF 5 - Ka-hi LHCP

9) LNBF 6 - Ka-lo RHCP

10) LNBF 6 - Ka-hi RHCP

 

110/119W

 

11) LNBF 7 - Ku 110 + 119 LHCP

 

119W

 

12) LNBF 8 - Ku 119 RHCP

 

Note: The SL-3 is the same excluding LNBFs 7 and 8 of course.

 

These then create the 12 "paths" (or 10 for the SL-3) each fed to a separate 9 bit ADC with a sampling rate of around 1.35 GigaSamples/s


Edited by HoTat2, 24 December 2013 - 03:34 AM.

DIRECTV sub. since Sep. of '95


#10 OFFLINE   veryoldschool

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Posted 24 December 2013 - 08:44 AM

Please explain details of the numbers by sat/pol/etc

There seems to be a bit of smoke and mirrors here.

There are six inputs in both the current analog SWM & DSWM.

With the three bands 250-750, 950-1450, 1650-2150 there are 18 possible 500 MHz blocks that can be used.


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#11 OFFLINE   P Smith

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Posted 24 December 2013 - 10:54 AM

There seems to be a bit of smoke and mirrors here.

There are six inputs in both the current analog SWM & DSWM.

With the three bands 250-750, 950-1450, 1650-2150 there are 18 possible 500 MHz blocks that can be used.

That's what was my initial impulse ...did decide to ask the 'math' though



#12 OFFLINE   slice1900

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Posted 24 December 2013 - 01:23 PM

There seems to be a bit of smoke and mirrors here.

There are six inputs in both the current analog SWM & DSWM.

With the three bands 250-750, 950-1450, 1650-2150 there are 18 possible 500 MHz blocks that can be used.

 

The patent doesn't mention flex ports at all, similar to how it (and the base analog SWM patents) leaves them out when describing the analog SWM.

 

However, it does say "while eight inputs 312-326 are shown, a larger or smaller number of inputs are possible without departing from the scope of the present invention". If we do get a 6 output LNB to add RDBS/BSS, the inputs on a future DSWM module might be labeled something other than "flex 1" and "flex 2" anyway...


Edited by slice1900, 24 December 2013 - 01:26 PM.

SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#13 OFFLINE   veryoldschool

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Posted 24 December 2013 - 01:28 PM

The patent doesn't mention flex ports at all, similar to how it (and the base analog SWM patents) leaves them out when describing the analog SWM.

Yet this doesn't change "the fact" that they are there and can be used.

You need to relate your patent readings to what is currently in use along with provisions not yet used.


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#14 OFFLINE   slice1900

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Posted 24 December 2013 - 01:33 PM

Yet this doesn't change "the fact" that they are there and can be used.

You need to relate your patent readings to what is currently in use along with provisions not yet used.

 

I was only attempting to relate what the patent states in a clearer manner than the patentese it is written in that most people can't understand well.

 

Since I'd written only about the SL3 and SL5 outputs, that's why I mentioned 10 and 12. I added a note about six additional inputs via the flex ports, or future LNBs with that may have six outputs.


Edited by slice1900, 24 December 2013 - 01:40 PM.

SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#15 OFFLINE   veryoldschool

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Posted 24 December 2013 - 01:58 PM

I was only attempting to relate what the patent states in a clearer manner than the patentese

Good luck with that :lol:

I seemed to remember "explaining" the digital filtering for you.


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#16 OFFLINE   slice1900

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Posted 24 December 2013 - 02:58 PM

Good luck with that :lol:

I seemed to remember "explaining" the digital filtering for you.

 

While I understand the computational side of the process quite well, I've never claimed to be an expert on the RF side. You are. That's why I asked for additions & corrections so others can make up for the gaps in my understanding and the patent description in the second post can be expanded and improved by applying expertise from both ends.


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#17 OFFLINE   veryoldschool

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Posted 24 December 2013 - 03:03 PM

While I understand the computational side of the process quite well, I've never claimed to be an expert on the RF side.

Digital filtering is "anything but" RF. :hair:


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#18 OFFLINE   slice1900

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Posted 24 December 2013 - 03:44 PM

Digital filtering is "anything but" RF. :hair:

 

The digital filtering in the DSWM is subject to the limitations of RF when has to go back out as RF and be received by analog tuners, i.e. requirement for skirts / guard bands. That is after all exactly what you "explained" to me about digital filtering...


SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#19 OFFLINE   inkahauts

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Posted 24 December 2013 - 07:20 PM

Replying to inkahauts' post from the DSWM13 thread.


Everything will become non-recoverable, eventually. But what makes you think they won't keep making DVRs with two tuners? Or that they won't make a new Genie with even more than 5 tuners? They haven't released a new dual tuner DVR since the HR24, but that doesn't mean they never will.

Directv would clearly benefit from having a single wire LNB that supports more than 8 tuners, since they hit that limit more often, and that trend seems likely to continue. I doubt anyone would dispute that. However, a DSWM LNB doesn't make sense until it costs them less to install than a legacy LNB, four coax, and SWM16. We can make some pretty good estimate of what the SWM16 solution costs, but can only guess at the cost of a DSWM LNB, or if there are some issues that need to be worked out before that's something they can offer at all, or ever.

There's nothing inherent in the DSWM technology itself that requires a higher output. It is doing A to D and then D to A conversion, and the D to A output doesn't require high levels, and even if it did there's no reason they couldn't be attenuated as necessary. Likewise, there's nothing inherent in the analog SWM technology that requires the specific output level it uses. That's determined by the AGC amp at its output. If they had wanted the SWM8 to output at -20 dbm or -40 dbm, they would have chosen the AGC amp and its settings to produce that output.

It isn't a matter of "porting" DSWM13 to MDU or the home market. They won't so much use a DSWM13 as a starting point as they'll use the DSWM ASIC as a starting point. Undoubtedly it would share a good portion of its design with that of the DSWM13, but certain things would be different, such as the output level and the number of channels. Once the exact frequencies being used in the DSWM13 are made public, we should have a better idea of what the maximum number of channels the DSWM ASIC inside of it is capable of. From the information I have so far it looks like that ASIC is capable of a maximum of either 15 or 22 channels. A different implementation of the DSWM (i.e. a new ASIC built in a different process) could have different channel spacing from the ASIC used in the DSWM13, of course.


I don't see another two tuner DVR for two reason. Money and direction.

Maybe a three tuner unit utilizing one four tuner chip. And sure we could se a seven tuner unit with two four tuner chips which is rumored To be what the hr44 was built with.

But at this point I'm Not sure you can make a two tuner unit for cheaper than at least a three tuner hunt anymore and still be able to perform at the same ability level as a genie. And I have a feeling internal box performance isn't why the hr44 is five instead of seven tuners. I think it's the other stuff that's limiting it.

#20 OFFLINE   slice1900

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Posted 24 December 2013 - 08:23 PM

I don't know what sort of tuner chips are out there now, or their cost. It obviously costs more to use more than one like the Genie does, but you may be right that there's not much cost savings to be had if there are newer chips that support more tuners so newer DVRs may have more than two.

 

Regardless of what future DVRs look like, Directv has some good reasons to desire a single wire LNB that supports more than 8 tuners if it can be produced as cost effectively as a legacy LNB + running 4 coax + SWM16 solution.

 

Directv will need to introduce a new LNB relatively soon if they intend to use RDBS/BSS for customer broadcast. Depending on how wide an interest that content has, and what form the legacy version of this new LNB might take (in particular, if it has six outputs) will determine, along with cost, the likelihood of seeing a DSWM LNB at that time.


SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#21 OFFLINE   Stuart Sweet

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Posted 24 December 2013 - 09:33 PM

Seems to me that I read where around 98% of customers are satisfied with 8 tuners or fewer. Granted that does leave roughly 400,000 households that want more than 8, but it certainly makes one wonder how it would be possible to achieve economies of scale for a new SWM with more than 16 tuner capacity unless it was required for future technologies.

It's clear that it's just been in the last 18 months or so that SWM16s have become inexpensive when purchased through legitimate sources, implying that it took 3ish years to make up the R&D investment. Putting aside the specific design of the DSWM13 which exists for a specific market, it's hard to see the economics of a future DSWM product being cost competitive with the existing ASWM devices. Unless, as I said, the existing SWM is somehow incompatible with future broadcasting.
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#22 OFFLINE   slice1900

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Posted 25 December 2013 - 01:33 AM

Based on that 98% figure, it would have to come down to DSWM being cheaper than analog SWM and entirely replacing it, because the volumes for SWM16 replacement would be too small. That's clearly a higher bar, but I don't believe it is as hopeless you feel it is. It will all come down to the cost per unit to make the DSWM ASIC, the NRE costs will become insignificant if it replaces the ASWM entirely. The ASWM contains a number of discrete components, including 9 SAWs and 3 RF5200 (or similar) chips, along with a 6x9 multiswitch at the input, all of which would be replaced by the DSWM ASIC.

 

The big unknown is the size of that ASIC. I understand the scale of it, but i don't really know what the computational requirements for each transponder are to implement the filtering, and the wiring for a mux able to handle up to 264 inputs (one per transponder) won't be pretty and could require a couple additional metal layers on its own.

 

For a foundry pricing comparison, its estimated Apple pays about $20 for the 100 sq mm A7 SoC in the latest iPhone & iPad. That's the price to have them made from Apple's "blueprints", including foundry profit, exclusive of Apple's NRE costs. Directv wouldn't buy DSWM ASICs at volumes remotely close to Apple, but the good news for them is that the economies of scale for a foundry peter out at around 1000 wafers (let's call that a half million A7 sized chips) so they don't need to buy in the tens of millions quantities Apple does to get similar pricing. I wonder how many SWM8, SWM16, and SWM LNBs are made in a year? A couple million, maybe? They should easily reach the thousand wafer bar - if they don't it means the DSWM ASIC is tiny, and they've already won.

 

A production volume of several million over a two year period drops the cost of the $3 million mask set to around $1/unit. The design costs of the ASIC itself are largely a sunk cost by virtue of the existence of the DSWM13, but they'd still need to design a DSWM LNB and an external DSWM module, provide installer training, etc. so maybe a $5 more per unit to account for all that, but largely amortized after the first year or so.

 

If the DSWM ASIC is around the size of Apple's A7, the $25/chip cost would compare unfavorably with ASWM, based on the Ebay pricing for SWM8s and SWM LNBs. If its half that size, at $15/chip, it may be close, especially in the second year when it is around $11/ea. A quarter the size and I think we have a winner! If the DSWM ASIC in the DSWM13, implemented in 45nm CMOS, is 100 sq mm, then implemented in 20nm CMOS it would be a quarter that size, and TSMC could start to deliver 20nm chips by next summer. If its larger, they need to wait a couple years for a smaller process, or value other advantages of DSWM - i.e. the frequency drift control and installation/diagnostic support mentioned in the other patent reducing their support costs.

 

Wish there was a way to find out the size of the ASIC in the DSWM13 - but even if someone had one to experiment on the chip would have to be desoldered and delidded to see the actual size, since the package you can see when you look at a board is governed by pin spacing and the size of the pad, not the often much smaller silicon chip inside.


SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#23 OFFLINE   slice1900

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Posted 25 December 2013 - 01:58 AM

Thinking more about the second patent, how much value would there be for Directv from a "smarter" LNB? Controlling frequency drift is nice, assuming temperature or aged related drift is a common reason LNBs have to be replaced for intermittent type issues, so replacements can be reduced.

 

Having the LNB able to tell a receiver when the drift risks getting too large to compensate for makes it even better. The receiver could either report it to Directv via the internet or tell the customer to call them. That's a lot nicer than people having intermittent problems they don't understand, and eventually calling Directv and trying to explain them, or coming to dbstalk for help. Or getting frustrated thinking those types of occasional problems are normal and going back to cable after the two years are up.

 

I also wonder, could the LNB tell the installer what to do to adjust the aim (once there's at least a little signal coming in) and tell the installer when they've got it aimed just right? The installer wouldn't look at a signal beyond getting something coming in, then he'd start receiving instructions to adjust this, then adjust that, monitoring the results of each step he performs and telling him the next step until he's done and the process could be made pretty foolproof. Much nicer for customers trying to aim dishes at a tailgate if the receiver could provide those instructions!

 

If these things could be done, how much is that worth to Directv in reduced support/installation/retention costs?


SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21


#24 OFFLINE   P Smith

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Posted 25 December 2013 - 10:54 AM

could require a couple additional metal layers on its own.

 

[voice from crowd]

metal [practically a copper] layers are for PCB, not in chips; there is more Si then Me

[/voice from crowd]



#25 OFFLINE   slice1900

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Posted 25 December 2013 - 02:23 PM

[voice from crowd]

metal [practically a copper] layers are for PCB, not in chips; there is more Si then Me

[/voice from crowd]

 

Not so, all silicon chips have multiple metal layers, which are deposited using CVD or similar one on top of the other, with an insulating layer deposited between them, then holes "cut" and filled in the dialectric for vias where the metal layers require connection. Transistors are formed on the very bottom, directly on the silicon wafer surface. Signal routing wires go in the layers above the transistors, short wires on the bottom and long (thicker) wires above, then one or more power planes form the top of the stack with the thickest metal. How do you think power and communication happen between all those isolated transistors deposited in the initial steps, if there are no wires? :)

 

These days very complex chips can have quite a few metal layers, for instance Intel currently uses nine in making their CPUs. The number of metal layers used in complex chips keeps going up and up as the transistors get smaller, because wires can't get smaller at the same rate so you either waste area not spacing your transistors as closely as you could, or you make the metal stack taller. Back in the days of the Apple II they could get away with only one or two metal layers in the tiny CPUs of the day, because the transistors were so big.

 

Simple stuff like DRAM and FPGAs has only three layers these days, and the DSWM ASIC, since it is mostly a DSP, is of comparable complexity, but that big multiplexer would need one layer to avoid wasting area. I was thinking perhaps two in my previous post, as typically you want to avoid the long wires that would result from the inefficient routing trying to cram that in a single layer. However the reasons you don't want long wires (propagation delay that scales roughly in proportion to the wire length squared, and resistive power losses) don't really matter in this case.

 

Additional metal layers increase wafer processing time and therefore cost, so I guess that's an advantage for the DSWM ASIC compared to the A7 I didn't think about previously. I have no idea how many metal layers the A7 uses, Apple is even more secretive about its tech than Directv, but it is safe to assume the number is closer to Intel's nine than a DSP's three. I don't know exactly much you save using half the metal layers of a chip of equivalent size, but it should knock down the DSWM ASIC cost a bit in my previous post.

 

Here's an image from a scanning electron microscope of what the metal stack actually looks like, with the metal layers labeled M1 through M6:

 

fig1.large.gif


SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21





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