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Re: [BCD396XT] FDMA

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  • MCH
    Wow. Without the quotes, it s not easy to follow the text, but... My definition has not changed from the beginning of the thread. I never said they were on the
    Message 1 of 46 , Mar 15, 2011
      Wow. Without the quotes, it's not easy to follow the text, but...

      My definition has not changed from the beginning of the thread. I never
      said they were on the exact same frequency (which would not be
      possible), but they do use the same transmitter. Again, satellites are
      an excellent example of true FDMA - they have one transmitter which has
      several user slots. The frequency bandwidth of the transmitter is shared
      among many users. That's your non-trunking counter-example.

      As for FDM, there is no practical difference between multiplexing and
      multiple access. They mean the same thing, as multiplexing is the
      combining of more than one signal on the same 'line' or transmitter.
      Well, unless the meaning of multiplexing changed.

      Yes, the examples at the bottom of my last post were meant mostly as
      sarcasm, but if you accept that FDMA can mean multiple users on multiple
      transmitters, every transmitter is FDMA. This is based on your bandplan
      based frequency division. Your local FD who uses 33.92 MHz is using a
      channel among other users who are sharing the same band and can use it
      at the same time. Therefore, a simplex, analog, Low Band transmitter is
      FDMA. No, no sarcasm this time. If you accept FDMA can be comprised of
      multiple transmitters, you cannot deny that everything is FDMA.

      You could also argue that everything is TDMA since different users can
      use a frequency at different times.

      I can accept the fact that FDMA and TDMA have been twisted to the point
      that they are meaningless anymore - just like 'channel'. But, that still
      doesn't mean that I have to accept that the meanings were always the
      same, or were not vastly different in the past when they meant what the
      words say. I think they were changed just so people could make systems
      sound more complex so they could get more money from sales. But, that's
      just a theory. No, I don't care to explore that one.

      So, the XT series I guess do already support FDMA and TDMA.
      A lot of people will be happy to hear that.

      Joe M.

      Yuni T. Runker wrote:
      > Hello Joe;
      >
      > --- On Mon, 3/14/11, MCH <mch@...> wrote:
      > By definition, they are sharing the same frequency bandwidth - it's just slit between (or among) them. Granted, not the exact same frequency, but the same transmitter.
      >
      >
      > Invoking your own definition to argue for it is just circular logic.
      >
      >
      >
      > If they are on distinct, separate frequencies, that is trunking. Or at
      > least that's what it's been called for the last 25 years.
      >
      >
      >
      > I'm sure you can think of non-trunking counter examples.
      >
      >
      >
      > If you read the MIT URL which you posted, it's saying the same thing.
      > The channel (transmitter) is divided into slots in the frequency domain.
      >
      >
      >
      > The MIT page does refer to dividing a channel into sub-channels. We've already agreed that the word channel is an overloaded, unreliable term. The MIT link does not say "transmitter" or place any such constraint on the equipment. Most of it's examples are cellular networks.
      >
      >
      >
      > It's ironic to have a "FDMA" transmitter that is neither dividing the frequency nor allowing multiple access, but is being granted that status in name.
      >
      >
      >
      > It allows multiple access to the same band by limiting its emission to a specific frequency or set of frequencies. Other transmitters can do the same provided they use different disjoint frequencies. Again, see how the term is applied to cable modems and other non-RF applications.
      >
      >
      >
      > What does FDM stand for?
      >
      >
      >
      > http://en.wikipedia.org/wiki/Frequency-division_multiplexing
      >
      >
      >
      > Quote from the article:
      >
      > "FDMA is the traditional way of separating radio signals from different transmitters."
      >
      >
      >
      > That's your one-transmitter handling multiple carriers. If FDMA meant what you claim, the industry would not have needed to invent another acronym.
      >
      >
      >
      > Just to clarify what you are saying:
      > Traditional trunking is now called FDMA
      > Traditional FDMA is now called FDM
      >
      >
      >
      > I've already said this discussion isn't about trunking. I know you're being sarcastic.
      >
      >
      >
      > Once you accept changes in the meanings of words, the words become meaningless.
      >
      >
      > Have faith Joe.
      >
      >
      >
      > [Non-text portions of this message have been removed]
      >
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
    • Yuni T. Runker
      Yeah. Don t know what happened to the formatting. ... [Non-text portions of this message have been removed]
      Message 46 of 46 , Mar 15, 2011
        Yeah. Don't know what happened to the formatting.

        On Mar 15, 2011, at 8:47 AM, MCH <mch@...> wrote:

        > Wow. Without the quotes, it's not easy to follow the text, but...


        [Non-text portions of this message have been removed]
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