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W1RFI
join:2003-05-12
Burlington, CT | reply to drjim
Re: FCC Official Anouncement said by drjim:They think "Internet over powerlines", and figure it's a great way to have access anywhere you have power, especially out in the sticks. The problem is, is that it doesn't travel all that far, and to *really* get it everywhere the power goes, you'd need to build _another_ infrastructure on top of the existing power system. IBEC is actually going after the rural market, primarily through RUS federal loans to municipalities to help them deploy broadband.
You are correct about the infrastructure, but any broadband system will require infrastructure. With BPL, I have often seen the figure of 2000 feet distance between repeaters, indicating that the maximum distance along overhead power lines is up to 2000 feet. In practice, in the field, I have seen as little as 300 feet as as much as about 1400 feet between repeaters.
If they are willing to put up a digital BPL repeater every 1000 feet along overhead power lines, it can be delivered for a few miles along a particular power line. Much beyond that, the latency (time delay) issues really start to mung things up.
Ed | |
| reply to BPL 200 Mbps
Re: FCC Official Anouncement !!! said by BPL 200 Mbps:FCC`s official Audio/Video last November 3, 2006- approval of Broadband Powerline or BPL as "Information Service" just like Cable or DSL. forward to 30:25 minute area: » xrl.us/s2kbListen to it and decide yourself folks... !!! I'm sure BBR would let you buy some banner advertising. 
The FCC's "approval" of BPL as an Information Service was as predictable as the sun coming up in the morning. I mean, really, think about it. Whose eyes are you trying to pull the wool over? | |
| reply to BPL 200 Mbps
Re: DS2 200 Mbps BPL tech is working with ARRL Laboratory !!! said by BPL 200 Mbps:it should be up to 600Mbps BPL ... !!! up to 600 Mbps !!! Will this answer your BANDWIDTH slowdown fear ? No. I haven't seen a BPL subscriber getting anything near 200 Mbs. (If there was a subscriber getting 200Mbs, you would certainly see press releases and articles here.) And if you knew anything about networks, 200 Mbs would be the backbone speed, not the end user speed. Has any vendor gotten 200 Mbs BPL to work on an overhead line and actually deliver a full 200 Mbs? | | |
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W1RFI
join:2003-05-12
Burlington, CT | Shannon's information theorum says that with absolutely perfect modulation, to attain 200 Mb/s using a 20 MHz channel, the signal-to-noise ratio at the end of the circuit would have to be 30 dB. With an estimated 15 dB loss between an injector and the repeater located 1000 feet away, the system would have to start out at 45 dB signal-to-noise. Unfortunately, at typical noise levels, that would put the system well above the FCC emissions limits.
At a more reasonable 10 dB signal-to-noise ratio, 70 Mb/s is the upper theoretical limit.
This assumes perfect modulation and demodulation. In practice, getting within 10 dB of the Shannon limit is considered to be pretty good. That would give a typical 20 Mb/s to the end user, not counting any bits used for system overhead.
The only G2 system whose data rate I tested had other indications that something was actually wrong with the system, so its results are really not useful at this time. I do expect to get back there, though, and as these other commerical systems come on line, sooner rather than later, we will see independent speed tests done for G2 as they have beend done for G1.
Ed | |
| reply to W1RFI
Re: FCC Official Anouncement said by W1RFI:You are correct about the infrastructure, but any broadband system will require infrastructure. Hi Ed,
That's true, but when you look at cable, the cable system itself is the backhaul network, and the repeaters (line amplifiers) are already in place and have been for years. While DSL has an 18,000 foot limit, telcos often have SLIC huts in neighborhoods with T1s going to them already to handle POTS service. I'm 65,000 feet from the CO in a rural area and nearly two years ago DSL came into my area. Presumably they're sticking DSLAMs in these huts to reach people like me. The point being, with cable and DSL, the infrastructure is already there. BPL is starting from scratch and really can't piggyback an existing network, and certainly not one that is already paid for like a cable network. The exception to this would be if the power company had fiber ran along the route of BPL feedpoints. In my neck of the woods this is done, but the fiber routes are few and far between and the ones on MV lines are targeting very urban areas. The ones in rural areas are on HV lines (up on 100' pylons) and are going between urban areas for transport. Granted these could be used to light up substations, but in my case, the substation servicing my location is about 10 miles away.
Ironically, the industry has been running on the claim that the infrastructure, power lines, is already there, despite it being the worse possible broadband medium around. The general public translates this to mean that BPL can be easily turned up with the flip of a switch. | |
| reply to W1RFI
Re: DS2 200 Mbps BPL tech is working with ARRL Laboratory !!! said by W1RFI:Shannon's information theorum says that with absolutely perfect modulation, to attain 200 Mb/s using a 20 MHz channel, the signal-to-noise ratio at the end of the circuit would have to be 30 dB. With an estimated 15 dB loss between an injector and the repeater located 1000 feet away, the system would have to start out at 45 dB signal-to-noise. Unfortunately, at typical noise levels, that would put the system well above the FCC emissions limits. At first I was thinking your 20 Mhz channel was a bit too small, considering there's about 80 Mhz of spectrum BPL is using (1 to 80 Mhz). But the lower 21 Mhz is not contiguous space as there's the mandatory NTIA notches and the amateur band notches. Then there's frequency reuse that needs to be considered. Each BPL repeater segment needs a different frequency band as the repeater can't prevent RF from one segment bleeding onto another; you're depending strictly on line attenuation for isolation between segments. I'm guessing n=3 or n=4 frequency reuse? Last you need separate frequencies for transmit and receive, so you need double the frequency bands/"channels". So, it's conceivable that one would need six to eight "channels" to work with. So your 20 Mhz channel figure is reasonable as the required number of channels would fit into what's usable in the 80 Mhz of spectrum.
Your 15 dB of loss between the coupler and repeater seems low to me, especially if you consider VHF frequencies. Have you seen this in practice or in your modeling?
At a more reasonable 10 dB signal-to-noise ratio, 70 Mb/s is the upper theoretical limit.
This assumes perfect modulation and demodulation. In practice, getting within 10 dB of the Shannon limit is considered to be pretty good. That would give a typical 20 Mb/s to the end user, not counting any bits used for system overhead. And no ISP in their right mind would give an end user the same speed that they have on their backbone. It would be too easy for one user to saturate the network and wreck the service for others. 10 to 25% would be reasonable. | |
| reply to rf_engineer
Re: FCC Official Anouncement !!! said by rf_engineer:said by BPL 200 Mbps:FCC`s official Audio/Video last November 3, 2006- approval of Broadband Powerline or BPL as "Information Service" just like Cable or DSL. forward to 30:25 minute area: » xrl.us/s2kbListen to it and decide yourself folks... !!! I'm sure BBR would let you buy some banner advertising. The FCC's "approval" of BPL as an Information Service was as predictable as the sun coming up in the morning. I mean, really, think about it. Whose eyes are you trying to pull the wool over? rf, this is the anonymous troll that used to post his rantings and fake press releases.  | |
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