Jim, Good points! Thank you.
John - K8OCL >From: "jgorman01" <[EMAIL PROTECTED]> >Reply-To: [email protected] >To: [email protected] >Subject: [digitalradio] Re: BPL-Busting Modes/Techniques >Date: Wed, 25 Oct 2006 21:34:20 -0000 > >Actually, the statement that a solution is possible is unproven. A >more accurate one might be that a solution may be possible. However, >802.11 is NOT a good example to use in citing how it might be done! > >The statement about 802.11 doesn't tell the whole story, not by a long >shot. These types of wireless protocols have collision avoidance and >interference mitigation built into the protocols. In other words, the >transmitters and receivers work together. 802.11 collision avoidance >is implemented by carrier sensing and random timing before starting to >send and/or requires a sender to forward a 'request to send' packet to >the receiver and should transmit only after receiving a 'clear to >send' packet back. Even then, there are problems with these >techniques where hidden terminals can wreak havoc, so they are not >perfect either. Although the spectrum looks full, it is also very >well controlled. > >BPL has none of this, so it is not even comparable. You can't ask BPL >for a request to send or even to stop sending for a period of time. An >even bigger problem is coordinating sending and receiving when you >have two terminals that are 1000's if not 10,000's of miles apart >which can happen on HF. What BPL is doing at any instant of time at >your location is absolutely no guarantee that the same thing is >happening at the receiving end. You may transmit in a perceived >"hole" (be it in frequency, time or phase) at your end, but at the >receiver, chances are that there is no corresponding "hole" when the >signal arrives. > >This isn't to say that some method can't be developed in time after >careful long term assessment of BPL characteristics. However, your >derision of Ed Hare being stuck in an analog world is not justifiable. >Your statements and examples like: > > > Yet, in digital networking we are able to work within and around > > this sea very effectively to do what we must do to communicate. If > > Hams can stop thinking of BPL as simply NOISE and investigate its > > specific nature, their great history of Ham Radio innovation will > > eventually prevail. > >don't come close to refuting what Ed said about BPL and its noise >characteristics. You can "...do what we must do to communicate..." >only because others have done the groundwork on the protocols to >insure collision avoidance is part of the basic operation. I am >surprised that chose to ignore this in your comparison. Although your >spectrum analyzer may show lots of RF, it is all very much in a >controlled environment and not at all like BPL. > >You live in a digital world so I tell you what, here's a little >problem for you to solve. Start up a laptop in your wireless network >that acts just like BPL. Make sure it has all collision avoidance >defeated, not just RTS/CTS but all CA, so it begins transmitting as >soon as data is ready, even if another node is transmitting. While >you're at it turn off all power control too, just run at maximum >output. Then, like BPL, make it constantly send data. Let us know >how quickly the whole network deteriorates. As an exercise, see how >quickly you can arrive at a solution that can be applied to the other >nodes to solve the problem of the uncontrolled transmitter and let us >know what that solution is. This problem is much more closely aligned >to the BPL issue than simply describing normal wireless operation as >being similar. > >Jim >WA0LYK > >--- In [email protected], "John Champa" <[EMAIL PROTECTED]> wrote: > > > > Ed, > > > > Nobody said it is available now, only that a solution is possible. >Bob even > > pointed out that any solution may be too expensive anyway. > > > > If we can pause for a minute and stop thinking in strictly analog >terms, > > then it is clear a solution is possible. For example, I work in a >virtual > > sea of BPL. It's thick and heavy. Any spectrum analysis indicates >such. > > > > Of course we don't call it "BPL", because it is the same stuff but >it is > > aimed deliberately at us. It's called 802.11g, 802.11a, and other >assorted > > OFDM products. > > > > Yet, in digital networking we are able to work within and around >this sea > > very effectively to do what we must do to communicate. If Hams can >stop > > thinking of BPL as simply NOISE and investigate its specific nature, >their > > great history of Ham Radio innovation will eventually prevail. > > > > Remember, somebody once said with equal certainty that 200 Meters >and down > > was absolutely worthless! (HI) > > > > 73, > > John - K8OCL > > > > > > > > >From: "Hare, Ed W1RFI" <[EMAIL PROTECTED]> > > >To: <[EMAIL PROTECTED]>,<[email protected]> > > >Subject: RE: [digitalradio] Re: BPL-Busting Modes/Techniques > > >Date: Wed, 25 Oct 2006 11:03:15 -0400 > > > > > >I strongly disagree. If a digital solution exists to dig signals 60 dB > > >out of poorly correlated noise, where can I download a copy or > > >information so I can copy signals 60 dB below the present ambient noise > > >levels? > > > > > >Ed Hare, W1RFI > > >ARRL Laboratory Manager > > >225 Main St > > >Newington, CT 06111 > > >Tel: 860-594-0318 > > >Internet: [EMAIL PROTECTED] > > >Web: http://www.arrl.org/ > > >Member: ASC C63 EMC Committee > > > Chairman: Subcommittee 5, Immunity > > > Chairman: Ad hoc BPL Working Group > > >Member: IEEE P1775 BPL EMC Committee > > >Member: IEEE, Standards Association, Electromagnetic Compatibility > > >Society > > >Member: ICES SCC-28 RF Safety > > >Member/Secretary: IEEE EMC Society Standards Development Committee > > > Chairman, BPL Study Project > > >Member: Society of Automotive Engineers EMC/EMR Committee > > >Board of Directors: QRP Amateur Radio Club International > > > > > > > Need a Digital mode QSO? 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