 KfedkaPremium
join:2005-05-06
Spokane, WA | Not enough bandwidth? Why not enough bandwidth, enless there are 10 tv's in the house watching hd channels. |
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GHz
join:2002-01-02
Needham, MA | I'm no cable expert, but it doesn't matter how many TVs are watching, it's a media transport limitation. A cable system works like a giant hub, and all cable channels are broadcast to all end-users, regardless of whether they are watching them or not. So you're already at-capacity, the only way to add more channels is to free up bandwidth by dropping unused channels. What they are proposing here is a switched media system, where not all channels are broadcast at the same time... channels are essentially on-demand, which means you can add as many channels as you like.
Someone correct me if I'm way off-base :P |
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 AlpinePremium
join:2000-01-11
Atlanta, GA | I think you hit it on the head...
Adam |
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 thender2Glamour ProfessionPremium
join:2004-05-16
Staten Island, NY | reply to Kfedka
A 1080i channel with equal quality to OTA tv is 17 mbps.
This is real quality - not directv, overcompressed-because-satelite-bandwidth-sucks bandwidth.
Three TVs is 51 mbps.. that's a lot. Cable can't handle this at peak hours. Looking at all the prior posts in the front page news, most major cable ISPs can't even handle internet, much less more HDTV.
I forsee a day where your TV shows "you have exceeded your monthly limit as specified by the fair use portion of the TOS" instead of 24 at 9 PM on Monday night.
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The Problem With Music.
Our Rationale
Time to rewrite the DMCA. |
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| Cable is multicast not point to point like IPTV. It's not three people watching the same channel that causes the bandwidth usage, it's three people watching different channels that causes it. With SDV the slots are allocated as people ask for the channel.
I actually see SDV as a pretty good solution. It eliminates 50% of the bandwidth waste. Combine that with DOCSIS 3.0 providing more bandwith and ultimatly putting less people on a node and I think cable has bandwidth for years to come. The question is: are those things cost competive compared to just going pure fiber. |
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| reply to thender2
said by thender2:A 1080i channel with equal quality to OTA tv is 17 mbps. This is real quality - not directv, over compressed-because-satelite-bandwidth-sucks bandwidth. Three TVs is 51 mbps.. that's a lot. Cable can't handle this at peak hours. Looking at all the prior posts in the front page news, most major cable ISPs can't even handle internet, much less more HDTV. I forsee a day where your TV shows "you have exceeded your monthly limit as specified by the fair use portion of the TOS" instead of 24 at 9 PM on Monday night. 1080i signal = 19.1 mbits, 720p signal = 15.3 mbits. Each Analog channel takes 6 MHz of freq, most cable networks in the US are 550 MHz, 750 MHz or 960 MHz. You can fit 6-8 digital channel or 2 HD channel in the same spot as 1 analog channel… I believe with QAM256 you are able to get 38.1 mbits per 6 mhz…
SDV will work the same way that current cable system works on the stand point on the node it doesn’t matter if 1 person or a 100 are watching. What SDV does is allocate frequencies to certain channels dynamically, much like DHCP work for a cable modem or your home network. So for instance let’s say I'm the first person to watch DiscoveryHD in my neighborhood, you tune to the channel on your cable box, the box sends out a signal to the node saying I want to watch discoveryhd. It checks to make sure I pay for the channel, and then allocates a frequency to that channel. Now let’s say Fred, 8 house down, also wants to watch discoveryhd at the same time as I am watching it. He tune to the channel on the cable box, the box sends out a signal to the node saying I want to watch discoveryhd. It checks to make sure I pay for the channel, and then sees that someone else is watching it on the node and what frequency is allocated to that channel on the node, it then uses the same frequency and tunes in without using anymore bandwidth. So doesn’t matter if 1 or 100 are watching it, or if you have the same channel on 10 TVs in your house. |
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thender2Glamour ProfessionPremium
join:2004-05-16
Staten Island, NY | Thanks, that was pretty interesting. I like learning new stuff on here. |
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mobbo
join:2005-04-13
Denton, TX | reply to valuepac0
Very nice explanation! So if this is true, it would actually be good if on one node 1,000 people were watching "24" or the Super Bowl because, essentially, it would only be like allocating a frequency for 1 person? |
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| reply to valuepac0
So the problem really is the current situation where you have digital and analog being delivered over the same cable? From what you posted it seems to me this problem self corrects if the digital switchover takes place in February 2009 as currently scheduled. |
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 cdruGo ColtsPremium,MVM
join:2003-05-14
Fort Wayne, IN
kudos:5
 ·Frontier FiOS
| reply to GHz
Essentially it's VoD at the node level. If anyone on a particular node wants say ESPN, then it gets broadcasted. If no one wants to watch QVC, then that bandwidth is not allocated for that channel.
Say you have 100 different channels and a node has 100 different receivers. At worst, you really are no worse off (network overhead aside) as all 100 stations would still be broadcasted. But if 1 or more of those receivers watched the same channel as another, you'd start saving bandwidth for other uses.
To make full use of this though nodes need be smaller. The larger the node you are on, the more likely the number of distinct channels increase. It's more likely a node of 500 customers would be watching more channels then a node of 100 customers.
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Go Colts |
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