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How do MDUs handle SWM overload?


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17 replies to this topic

#1 OFFLINE   wesmills

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Posted 29 August 2008 - 09:46 PM

I am not a MDU sysop, nor do I ever plan to be one, but I was pondering this question. ("How do MDUs handle SWM overload?")

The basis for wondering how MDU operators handle an overloaded SWM comes from my (ill-informed?) assumption that the "consumer" SWM8 is as big as it gets for MDUs. Is this true?

If so, then knowing there's nothing (short of "education" about how a subscriber Shouldn't Do That) to prevent a subscriber from getting clever and splitting the signal much like people are used to doing with cable, and since SWM-capable receivers are available for purchase pretty much everywhere electronics are sold, what do y'all do? Keep extremely detailed records of who has what receivers--according to your installers--and then compare that list to some master list DirecTV might send you of what your "downline" subs have on their accounts? I can think of some possibilities, but they seem incredibly expensive (dedicated SWM8 for every unit comes to mind) or time-consuming (have somebody go on-site, rebalancing connections as needed). Then again, this all goes back to my assumption that MDUs can only go as high as SWM8.

Do any MDUs deliberately or unintentionally leave apartment units hooked up to the distribution system (that is, a unit is not disconnected when a tenant moves out) so that truck rolls are avoided? (Just ship 'em the box and tell them to plug it in) That seems like that would create more problems (somebody shows up with five HR21s from their old house and instantly overloads even a dedicated SWM8), but is that a scenario for which a sysop plans?

If this is all top secret industry hush-hush stuff, let me know and I'll just sit on my curiosity. :)

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#2 OFFLINE   AntAltMike

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Posted 30 August 2008 - 09:24 AM

Only the apartments that are enrolled in the MDU system will be physically connected to an SWM coax, so the only way an SWM could get overloaded would be for an established SWM subscriber to independently add his own receiver.

I'm not sure about this, but I think that once a residential subscriber's account is registered as part of a MDU system, only the MDU operator can add receivers to that account, so if a resident simply legally procured a receiver elsewhere, he would have to pay "full fare" for that receiver's subscription to activate it, so it would not be worth his while to do so.

I would say the only way that someone might surreptitiously overload an SWM is by taking a receiver that was registered to another person's valid account that additional premium programming included in its subscription.

Even though I do commercial service only and service lots of MDUs, I have so far avoided getting directly involved in any SWM projects because I don't have the time that would be necessary to deal with the "bleeding edge" characteristic of managing this technology when something could just "go wrong" that I cannot efficiently diagnose. Right now, if I were called to troubleshoot an SWM application that involved multiple apartments, and if I couldn't definitively find a fault in the parts of the distribution system I have ready access to, I would hate to have to contact the other subscribers who had not yet complained about their DirecTV service, asking them how many tuners they have (they might lie), or then asking them if they could power down their unit, or let me into their unit to test a device that was not malfunctioning, or suppose the problem is intermittent? Do I tell them their receiver has to be swapped out to remedy an intermittent problem that doesn't affect them and that I can't definitively diagnose?

I once was called out to diagnose a building-wide single satellite stacked LNB system where I determined the cause to be the backfeed from one of the residents. This was not a registered MDU system. It was just a community antenna system paid for by a condo association and installed by a residential installer, and so each subscribing resident sets up his own account and as far as DirecTV's records are concerned, they are a bunch of single family residences.

The most likely cause of the backfeed was that there was an old, low frequency splitter in the apartment that was throwing back the interference. There are other possibilities, but I don't have a relationship with that resident and she wasn't home, so I disconnected her coax, which cut her DirecTV off but restored service to the other unit. Actually, since I had also enhanced the signal strength and quality of the distribution, it would now have worked even with the interference her line was throwing back, but I wanted to eliminate this interference once and for all, so I left her a note telling her what I had found and offering to come into her apartment and remedy the problem, with the HOA paying for the cost of the service and the only cost she MIGHT have to incur would be that of a receiver replacement of that turned out to be the offending component.

She called me that evening and said that she would not "accept" my diagnosis. I politely and as inoffensively as possible told her that she didn't really have a vote in the matter. I was hired by the HOA to remedy a building-wide problem, I remedied it for everyone else but her unit by disconnecting her unit and now she doesn't have any DirecTV (which she did not realize, because she hadn't turned her TVs on yet).

She said she didn't want me in her apartment. I told her that since her DirecTV home run connection was in a secure area controlled by the HOA, she would have no TV service until someone authorized by the HOA reconnected it, and that I was going to advise them against either reconnecting it themselves and to not have it reconnected until someone remedied the interference problem emanating from her apartment, but regardless of how it was resolved, this is the kind of headache that I am not staffed to handle, and the kind that I think SWM operators are going to run into when they receive reports of problems that MIGHT be caused by over-subscription or might be caused by an intermittent hardware problem that is not present when they are on site.

Neither she nor the HOA ever called me to reconnect that unit, so I don't know if someone just physically reconnected her, which as I said, would now work since I did improve the system signal quality enough to make strong enough to withstand the interference, or if she just switched to cable TV

Can anyone with a spectrum analyzer look at the output of an SWM to see if all nine SWM transponders are developed even when the receivers are not calling for all eight available frequencies. If not, then that would give us at least some means to determine how many transponders each apartment is calling for at any given time, but even then, if I come out for a service call based on a complaint by one resident that there was no transponder availability last night, but if two of the receivers in an offending apartment are now tuned to the same program when I arrive, then the tuner over-subscription would not be apparent even if I could detect the number of transponders being called for, which I don't think I can detect anyway.

I'm probably going to be setting up an SWM system in a large building in which I will simply quoting installation terms that carry the cost of furnishing one SWM (or more) per apartment. Since some of the residents in that building are, or have previously been in, the Forbes 500, I don't expect any price resistance, but even at today's SWM prices, it is still a big pill for a small apartment with just one or two tuners to swallow.

#3 OFFLINE   wesmills

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Posted 30 August 2008 - 02:42 PM

Yay! That's exactly the sort of reply I was seeking.

Your comment about the cost is spot-on. I'm curious if MDU developers front-load costs like that, or pay over time for the labor to keep everything in check. Of course, this all goes out the window when you're "huge," and especially somebody like DirecPath which is practically DirecTV doing its own MDU; I bet they have the coin to front every unit a SWM but don't because of the corporate bean counters.

In thinking about this myself, I suspect it's a combination of the two. Perhaps for an apartment with four outlets such as a 3BR, it makes sense to dedicate a SWM. For smaller units, such as two 1BR units with an outlet in the bedroom and another in the living room, split a SWM between the two.

Of course, this is all academic since my only involvement with a MDU system is as a subscriber to a MFH1 system. I'm just curious about everything. :)

#4 OFFLINE   AntAltMike

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Posted 30 August 2008 - 04:24 PM

As best as I can determine, neearly all SWMs are installed on an as-needed basis, beyond a small number included in the initial installation. Apartments without SWM subscribers will not ordinarily have a live path to an SWM.

#5 OFFLINE   Incog-Neato

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Posted 30 August 2008 - 04:44 PM

They add SWM's just as you would do in res home except there is not one swm per unit (as it would get quite expensive in a large property). And a big YES, customers can and often do add their own receivers which can wreck HAVOC with existing customers. It happens all the time. Then a tech goes out and needs to add another SWM to the SWM rack (they stack 'em). Unfortunately, unlike with the older systems where sysops can have some control because additional equipment may be needed to connect new receivers so customers can't do it on their own. With SWM it is causing a MAJOR problem in mdu properties (especially the ones high HD penetration). Sysops do not usually allocate 1 SWM per unit due to cost but they are installed in a common closet and are supposed to be tagged with the unit number and # of tuners connected to each SWM. This gets messed up quite often as well which leads to "overpopulated" SWMs which leads to other customers getting knocked off the system until the tech returns and adds another SWM to the rack. It's created a very large problem.

#6 OFFLINE   Incog-Neato

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Posted 30 August 2008 - 04:47 PM

DirecTV won't touch MDU's. It's only done by PCO's who handle all support and installation. Sometimes (and this is being fixed) DirecTV accidently sends their techs out to a property and more times then not they never walk in the door.

Yay! That's exactly the sort of reply I was seeking.

Your comment about the cost is spot-on. I'm curious if MDU developers front-load costs like that, or pay over time for the labor to keep everything in check. Of course, this all goes out the window when you're "huge," and especially somebody like DirecPath which is practically DirecTV doing its own MDU; I bet they have the coin to front every unit a SWM but don't because of the corporate bean counters.

In thinking about this myself, I suspect it's a combination of the two. Perhaps for an apartment with four outlets such as a 3BR, it makes sense to dedicate a SWM. For smaller units, such as two 1BR units with an outlet in the bedroom and another in the living room, split a SWM between the two.

Of course, this is all academic since my only involvement with a MDU system is as a subscriber to a MFH1 system. I'm just curious about everything. :)



#7 OFFLINE   texasbrit

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Posted 30 August 2008 - 06:50 PM

Can anyone with a spectrum analyzer look at the output of an SWM to see if all nine SWM transponders are developed even when the receivers are not calling for all eight available frequencies. If not, then that would give us at least some means to determine how many transponders each apartment is calling for at any given time, but even then, if I come out for a service call based on a complaint by one resident that there was no transponder availability last night, but if two of the receivers in an offending apartment are now tuned to the same program when I arrive, then the tuner over-subscription would not be apparent even if I could detect the number of transponders being called for, which I don't think I can detect anyway..


I don't think there is any way of telling how many tuners are attached to an SWM, because as you say two tuners will use the same SWM channel if the transponder they want is on that channel. So you could look at the SWM output and it could have seven SWM channels busy even though nine tuners were attached. The only place where potentially the nine tuners could be visible is on the 2.3Ghz control channel and unless the SWM channel allocations are on the control channel all the time (I don't know if they are, or if it is strictly a request-response scenario), and you can decode the protocol, I think it's a lost cause.
You can certainly detect the problem if you are looking at a DVR while it is happening; if the DVR SWM screen shows nine (eight plus guide) SWM screens all in use, and then you tune both DVR tuners to the same channel, and there are still nine busy SWM channels, this will indicate too many tuners connected to the SWM. Same if you have multiple receivers, and you tune them to the same channel, it should affect the number of active SWM channels.
But as you say, if when you arrive the problem has gone away because some of the tuners are now "SWM channel sharing", it's impossible to tell.

#8 OFFLINE   wesmills

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Posted 02 September 2008 - 03:40 PM

DirecTV won't touch MDU's. It's only done by PCO's who handle all support and installation. Sometimes (and this is being fixed) DirecTV accidently sends their techs out to a property and more times then not they never walk in the door.


Sorry, I was unclear. I didn't mean DirecTV "retail" was doing MDUs; I meant DirecPath, which is (according to their press releases) a "joint venture" between Hicks and DirecTV, had access to the same deep pockets as DirecTV and they might dedicate that sort of hardware, but it's unlikely.

So far, I'm confused as to the hoopla over SWM, except in residential installations where the customer owns the dish, cabling and switching equipment. It seems like MFH1 had a lot less hassle for the system operator, if only for the lack of ability to overload the switching gear. In a perfect world, sysops could perfectly control the number of tuners on each switch, but that's unlikely. Never mind that the SWM8 upper cap seems like a "8 tuners should be enough for anybody" mentality. That might be true in standalone install--even though 20% or more of DBSTalk members probably exceed that limit--but in an apartment it just seems brain-dead.

It seems like MFH2 was a stop-gap solution to get HD access to MDU subscribers, but it can go wrong in what appears (to me) to be an obvious way. Perhaps MFH3 is the "true" fix?

#9 OFFLINE   Slowhand

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Posted 02 September 2008 - 05:18 PM

I am a sys op in the Washington DC area. I have several buildings that I have upgraded to MFH2 and so far everything is going ok.

The SWMs seem reliable. I have not had to replace any. Resetting the receivers have not been an issue and necessary.

As far as overpopulating the swms I don't think that will be too much of an issue. Most swms only are only connected to two units each. I don't think that we have any swms that have more than three units connected to them.

To help prevent overpopulating the swm we try to have only seven tuners registered on each swm.

I don't think tracking down the source of the overload of tuners on a swm will be too hard because if Unit 1 is complaining about problems we can check out the number of tuners they have. Then contact DirecTV dealer services and get information on the other two units and the number of tuners on the accounts.

The main problem we have is trying to explain to customers why they have to pay for an swm charge when they see and hear the ads from DirecTv for free installs and free receivers.

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#10 OFFLINE   AntAltMike

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Posted 02 September 2008 - 05:41 PM

So far, I'm confused as to the hoopla over SWM, except in residential installations where the customer owns the dish, cabling and switching equipment. It seems like MFH1 had a lot less hassle for the system operator, if only for the lack of ability to overload the switching gear.

It seems like MFH2 was a stop-gap solution to get HD access to MDU subscribers, but it can go wrong in what appears (to me) to be an obvious way. Perhaps MFH3 is the "true" fix?


MFH1 takes the Ku signals from Sats A B and C and stacks them up to 3.4 MHz. I have never installed or serviced that system and ever will. Coax signal losses are too high at 3.4 MHz for cable lengths I commonly encounter, there are almost no splitters and no diplexers rated to that frequency, and it simply does not have the bandwidth for the additional 4 GHz of Ka bandswith that DirecTV is using.

SWM allows one coax to fully support eight tuners, it can be diplexed with cable TV, off-air and internet, it seems to be reliable and its price is coming down. As long as sharing is limited to two apartments per SWM, and as long as a system operator controls the connections to the extent that he can, I am inclined to think of it as the final solution, but there are some operators serving smaller complexes that have lots of studio and one bedroom apartments that try to support three or more apartments with one SWM and I think eventually, they will conclude that straddling an SWM among more than two dozen units is penny wise and dollar foolish.

#11 OFFLINE   odorcide

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Posted 23 September 2008 - 07:59 PM

As others have said we just do two unit per SWM, seems to work out well until the chassis is full and you have to get the customer installed.

#12 OFFLINE   djjolietjake

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Posted 03 October 2008 - 05:29 AM

As others have said we just do two unit per SWM, seems to work out well until the chassis is full and you have to get the customer installed.


Remember folks, the FCM-6's can be cascaded up to 4 before re-amping... If everything is properly balanced and your using good quality coax and watch your distances, it works fantastic!
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#13 OFFLINE   David MacLeod

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Posted 08 October 2008 - 06:01 AM

very interesting, thanks for posting this.
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#14 OFFLINE   odorcide

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Posted 08 October 2008 - 09:29 AM

Remember folks, the FCM-6's can be cascaded up to 4 before re-amping... If everything is properly balanced and your using good quality coax and watch your distances, it works fantastic!


I know about that but we don't carry spare chassis as truck stock.

#15 OFFLINE   AntAltMike

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Posted 08 October 2008 - 09:49 AM

I just installed a tapped trunkline system with each tapped location having a two way splitter on each tap port, with one port of each splitter connected to the flatter, four-SWM chassis and the other port vacant and terminated.

When the first chassis is fully stuffed, then someone is going to have to spring for the second four-port chassis, but the balancing of the system will stay the same until such time as a 9th SWM needs to be installed, which will probably be never. The four-SWM chassis cost less than a third as much as the FMC-6s. In an emergency, the fifth SWM can be directly connected to the vacant two-way splitter ports.

I may even hide a spare four-SWM chassis in one of the eight cable closets so that if a residential installer shows up without one, he can call me (or the property manager) and I can tell him where it is and how much it costs.

#16 OFFLINE   David MacLeod

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Posted 08 October 2008 - 10:19 AM

I'll never do an mdu, but I find it interesting. can someone post some links on terms and setup scenarios just for grins?
thanks.
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#17 OFFLINE   Bkegg

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Posted 07 November 2008 - 02:22 AM

The best way to prevent overloading the SWM MDU is proper labeling when installing. I just started working with the SWM based MDU and so far so good. If the SWM8s in the racks are properly labeled with APT# and # of tuners its simple subtraction to figure out who is knocking out what.

Also just a query. The SWM reciever are designed to reach out find a frequency band and lock on. With only 8 bands I would think out of say 9 D-12s the last reciever to power up would be SOL.

As for the Chasis capacity still same thing correct precise labeling is the only way to be able to anticipate quota. When it's getting full do some math and determine if another one is needed.

#18 OFFLINE   texasbrit

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Posted 07 November 2008 - 08:20 AM

The best way to prevent overloading the SWM MDU is proper labeling when installing. I just started working with the SWM based MDU and so far so good. If the SWM8s in the racks are properly labeled with APT# and # of tuners its simple subtraction to figure out who is knocking out what.

Also just a query. The SWM reciever are designed to reach out find a frequency band and lock on. With only 8 bands I would think out of say 9 D-12s the last reciever to power up would be SOL.

As for the Chasis capacity still same thing correct precise labeling is the only way to be able to anticipate quota. When it's getting full do some math and determine if another one is needed.

Unfortunately it does not work that way. When a receiver powers up it sends a message to the SWM asking for a particular transponder. If another receiver has already asked for that transponder the SWM tells the new receiver to look at the SWM channel that already has the correct transponder, it does not allocate a new one. So it is possible to have, say, ten receivers connected to an SWM, all working OK, as long as the total number of different transponders being used by the receivers is eight or less. As soon as one of the receivers asks for a ninth transponder, there will be a failure. I believe the 771s will appear on the receiver requesting the ninth transponder but have not done enough testing to prove that is what always happens.

And the problem with SWM overload is not usually that someone has miscalculated the number of tuners on an SWM. It is that someone in the apartment complex adds a receiver/DVR on his own without telling the MDU tech (e.g. to avoid paying the install fee). The person who has installed the "rogue" receiver may think everything is working, because at the time of the install there were eight or less transponders being requested, but sooner or later the number of requested transponders will go above eight and then whichever tuner asked for the ninth transponder will lose signal (probably in someone else's apartment).




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