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Thread: A cheap short wave radio Internet?

  1. #1 A cheap short wave radio Internet? 
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    It is known that short wave radio allow you to communicate through thousands of miles.
    Why not to make a cheap Internet which would be based on short waves?You would need only
    one or a few strong transmitter hubs for a large city.I guess frequency in MHz range gives you
    sufficient bandwidth.Also each transmitter could be equipped with thousands of micro-transmitters
    wich are able to transmitt simultaneously to encrease bandwidth even more.I know that short waves
    are susceptible to athmosferic interruptions.But most of cities rarely experience storms.And in case of
    storms you would be able to swith to more reliable Internet connection such as cable.(And have agreement to pay less money as you use it occasionally).What do you think?


    Last edited by Stanley514; February 9th, 2012 at 07:27 PM.
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    Isn't Wimax use the same concept? You could subscribe to Wimax if you wanted too. It is available commercially, and each transmitter cover 10Km area.


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    Or there is Packet radio.
    dan hunter likes this.
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    Quote Originally Posted by Stanley514 View Post
    It is known that short wave radio allow you to communicate through thousands of miles.
    Why not to make a cheap Internet which would be based on short waves?You would need only
    one or a few strong transmitter hubs for a large city.I guess frequency in MHz range gives you
    sufficient bandwidth.
    It depends on the definition of "sufficient." How many users are going to be within the service radius of a city? What peak and average data rates are these users supposed to have? It's not hard to come up with aggregate bitrates that would not feasibly fit within the bandwidths of ham radio bands. That's why cellular telephony evolved as it did -- by keeping service radii small, you can "reuse" spectrum and serve many more users. The tradeoff is that someone has to spend lots of money to build out the infrastructure.

    If "sufficient" means "Morse code data rates," then maybe...
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  6. #5  
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    20 years ago I purchased a very good shortwave receiver. I was entertained by North Korea, Havana, some crackpot Libertarian out of Alaska, even tiny "Free Kurdistan" broadcasters. Now the interference is too thick to really get much. I think it is the proliferation of wireless devices...

    which is strange because airwaves were supposed to be regulated against this problem. Shortly after telegraph technology we had the radio AKA "the wireless".
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    Isn't Wimax use the same concept? You could subscribe to Wimax if you wanted too. It is available commercially, and each transmitter cover 10Km area.
    What frequency do they use? This one article mentions Wimax frequency is 2GHz - 66GHz. Also it seem requires a big tower. http://computer.howstuffworks.com/wimax1.htm
    I do not see why majority of Internet users who need cheap Internet need that much high frequency. High quality TV is broadcasted in 14 MHz range. (And common TV's do not seem to use data compression.) I guess this range wud allow much larger distance to cover with much cheaper equipment?
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    Quote Originally Posted by Stanley514 View Post
    Isn't Wimax use the same concept? You could subscribe to Wimax if you wanted too. It is available commercially, and each transmitter cover 10Km area.
    What frequency do they use? This one article mentions Wimax frequency is 2GHz - 66GHz. Also it seem requires a big tower. HowStuffWorks "WiMAX Wireless Network"
    I do not see why majority of Internet users who need cheap Internet need that much high frequency. High quality TV is broadcasted in 14 MHz range. (And common TV's do not seem to use data compression.) I guess this range wud allow much larger distance to cover with much cheaper equipment?
    You're missing a key point. Broadcast TV is indeed high quality, but one TV station consumes the entire spectrum of its assigned channel, and over a large geographical area. If you want to allow more conversants (as opposed to passive listeners), you must either make more spectrum available, or you have to reduce the transmission range (to allow the available spectrum to be reused by other customers within a geographic area). Look up the term "cellular wireless" if my earlier explanation was unclear. The cellular idea is very important if you want to allow millions -- billions -- of users to share the finite spectrum available.
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    We have been using radio to make dedicated data lines between places for years. It is nothing new.
    It is by will alone I set my mind in motion.
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    You're missing a key point. Broadcast TV is indeed high quality, but one TV station consumes the entire spectrum of its assigned channel, and over a large geographical area. If you want to allow more conversants (as opposed to passive listeners), you must either make more spectrum available, or you have to reduce the transmission range (to allow the available spectrum to be reused by other customers within a geographic area). Look up the term "cellular wireless" if my earlier explanation was unclear. The cellular idea is very important if you want to allow millions -- billions -- of users to share the finite spectrum available.
    If users use phone line for uploading data and short waves for receiving, does it reduce the problem? And what frequency step size should be between different users in order to minimize interference?
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    Quote Originally Posted by pyoko View Post
    We have been using radio to make dedicated data lines between places for years. It is nothing new.
    There's almost never anything truly new. In this case, the OP used the term "radio internet," which perhaps connotes something a bit different from a pure dedicated data link.
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    Quote Originally Posted by Stanley514 View Post
    If users use phone line for uploading data and short waves for receiving, does it reduce the problem?
    Sure. In a symmetrical scenario, you'd relax the problem by a factor two, for example. Helpful, but you don't win prizes for that, especially if you are starting with one user per square km. Going to 2 users per sq. km isn't much to boast about.

    And what frequency step size should be between different users in order to minimize interference?
    It's not an absolute frequency value; it scales with the carrier frequency, among other things. In very, very, extremely crude terms, you can space users apart by a value roughly on the order of one part in a thousand of the carrier frequency. So, if you are using 2GHz carriers, you might be able to space channels apart by about 20MHz. A much tighter spacing than that requires more expensive components, and a much looser spacing than that wastes precious spectrum.
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    Well, I worked at a government fire service IT department and we were installing radio lines actoss the state. I know it's not "Internet", but it sure is part of it. Why it is useful is because it increases the speed and cost of loaning a dedicated line. Why it is bad for general public use is, ironically, because it is too expensive.
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    Quote Originally Posted by pyoko View Post
    Well, I worked at a government fire service IT department and we were installing radio lines actoss the state. I know it's not "Internet", but it sure is part of it. Why it is useful is because it increases the speed and cost of loaning a dedicated line. Why it is bad for general public use is, ironically, because it is too expensive.
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    What is multiplexing?
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    Quote Originally Posted by Stanley514 View Post
    What is multiplexing?
    In the context of wireless, it's the act of allowing multiple users to access the same resource (spectrum) "simultaneously." It's more commonly called "multiple access" these days.

    Three methods are used, individually or in combination: Frequency-division, time-division, and code-division multiple access. In FDMA, each user is assigned a different frequency. In TDMA, users can employ the same frequency, but access is granted for only small windows of time for each user. In CDMA, each signal is convolved with a unique code. Simultaneous conversations can take place; the desired one is picked out from all the others by using the known unique code to decode the transmission. The other users' signals then look like noise. The number of users that can use the frequency is determined by when the aggregate noise of the undesired signals finally overwhelms the power of the desired signal.
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    What exactly limits speed of data transmission by copper and phone lines (of a single wire) to 1-4 Mbts/sec? Could we increase frequency into GHz range?
    Why digital signals cannot spread in phone lines and we need a modems? What allows you faster bitrates, digital or analog signals?
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  18. #17  
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    Quote Originally Posted by Stanley514 View Post
    What exactly limits speed of data transmission by copper and phone lines (of a single wire) to 1-4 Mbts/sec? Could we increase frequency into GHz range?
    Why digital signals cannot spread in phone lines and we need a modems? What allows you faster bitrates, digital or analog signals?
    The capacity (in bits per second) of a transmission medium or channel is directly proportional to bandwidth, and to a logarithmic measure of signal-to-noise ratio.

    As you increase frequency, various types of losses kick in, causing signal-to-noise ratio to diminish. That causes the capacity to diminish. Some of these losses include "skin effect" losses (effective increase in resistance with increasing frequency) and radiation (wires can act like antennas, causing energy to be "lost".
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    Some of these losses include "skin effect" losses (effective increase in resistance with increasing frequency) and radiation (wires can act like antennas, causing energy to be "lost".
    Do the same type of looses relate to digital (pulsed DC current) data transmission?
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    Quote Originally Posted by Stanley514 View Post
    Some of these losses include "skin effect" losses (effective increase in resistance with increasing frequency) and radiation (wires can act like antennas, causing energy to be "lost".
    Do the same type of looses relate to digital (pulsed DC current) data transmission?
    The wires don't know whether the signals are digital or analog. They're just signals.
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    The wires don't know whether the signals are digital or analog. They're just signals.
    From what I know such issues as skin effect and radiation are associated with AC current, not with (pulsed) DC.
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  22. #21  
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    Quote Originally Posted by Stanley514 View Post
    The wires don't know whether the signals are digital or analog. They're just signals.
    From what I know such issues as skin effect and radiation are associated with AC current, not with (pulsed) DC.
    Pulsed DC is AC. Just because it's not sinusoidal does not make it non-AC. Indeed, one could argue -- successfully -- that true DC does not exist, because nothing has been on forever.
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    The affordable alternative to fibre, DSL Rings delivers 400 Mb/s broadband to rural and urban communities
    Genesis Technical Systems Launches Superfast DSL Rings(R) to North American and Rural Markets - Yahoo Finance

    It is still not clear what is the range/distance of this system. From what I know, similar systems do not work for distance more then few hundreds of meters without repeater. But why? Could it be regarded as useful link between fiber optic and usual phone line network? I wonder where exactly now is weak link of Internet which doesn't allow it to become much cheaper and in the same time unlimited? I think that limitation of typical user to 50-80 GB/month download/upload capacity is ridiculous.
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  24. #23  
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    Quote Originally Posted by Stanley514 View Post
    The affordable alternative to fibre, DSL Rings delivers 400 Mb/s broadband to rural and urban communities
    Genesis Technical Systems Launches Superfast DSL Rings(R) to North American and Rural Markets - Yahoo Finance

    It is still not clear what is the range/distance of this system. From what I know, similar systems do not work for distance more then few hundreds of meters without repeater. But why? Could it be regarded as useful link between fiber optic and usual phone line network? I wonder where exactly now is weak link of Internet which doesn't allow it to become much cheaper and in the same time unlimited? I think that limitation of typical user to 50-80 GB/month download/upload capacity is ridiculous.
    Look up the attenuation characteristics of cables to understand the answer to your question.
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    Mathematical research conducted by the U.S. National Institute of Standards and Technology could lead to the development of military radios capable of hopping frequencies up to 1,000 times faster than conventional systems. The research also could result in more energy-efficient, interference-resistant cellular telephones than are available today, as well as improvements in many other modern communications devices.
    New Wave Communications Emerge | SIGNAL Magazine
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    Quote Originally Posted by Stanley514 View Post
    Mathematical research conducted by the U.S. National Institute of Standards and Technology could lead to the development of military radios capable of hopping frequencies up to 1,000 times faster than conventional systems. The research also could result in more energy-efficient, interference-resistant cellular telephones than are available today, as well as improvements in many other modern communications devices.
    New Wave Communications Emerge | SIGNAL Magazine
    I wouldn't hold my breath. Soliton-based technology might be scientifically interesting, but CDMA should be able to do just as well, with far less effort. But it's good that nonzero amounts of funding are being used to study the prospect, in any case.
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    I wouldn't hold my breath. Soliton-based technology might be scientifically interesting, but CDMA should be able to do just as well,
    Could they combine these technologies? And how many users in the same frequency CDMA does allow to have?
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    A serial entrepreneur released a white paper describing a wireless technology that can deliver more than ten-fold increases in spectrum utilization compared to today's cellular systems.
    DIDO promises wireless breakthroughs | EE Times

    I still can't understand what does mean for example: "Each client receives a unique waveform with just that user's data. DIDO does this by synthesizing a private channel for each user, which is why each user gets 100 percent of the data rate of the spectrum, regardless of how many users share the spectrum, Perlman said."

    What does it mean unique waveform and how interference is avoided?
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  29. #28  
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    Quote Originally Posted by Stanley514 View Post
    What does it mean unique waveform and how interference is avoided?
    Interference cannot be avoided. In code division multiple access, for example, everyone gets their own "waveform" (i.e. code) and transmits on the same frequency. This increases background noise which eventually makes it harder to receive new signals. In "normal" (i.e. AM) communications this problem is referred to as signal to noise ratio; in spread spectrum systems it is referred to as Eb/No (energy per bit or symbol vs noise power spectral ratio.)

    It can be mitigated many ways. In the case of this paper, it is mitigated by putting the antennas a lot closer to the user. If your system has 1000 active users, but the antenna can only "see" ten people at a time, then you have decreased interference by a factor of 100.
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  30. #29  
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    Quote Originally Posted by Stanley514 View Post
    A serial entrepreneur released a white paper describing a wireless technology that can deliver more than ten-fold increases in spectrum utilization compared to today's cellular systems.
    DIDO promises wireless breakthroughs | EE Times

    I still can't understand what does mean for example: "Each client receives a unique waveform with just that user's data. DIDO does this by synthesizing a private channel for each user, which is why each user gets 100 percent of the data rate of the spectrum, regardless of how many users share the spectrum, Perlman said."

    What does it mean unique waveform and how interference is avoided?
    There really are very few ways of increasing network capacity, and all have been tried. Giving each user a unique code is already done; that's what Qualcomm's CDMA does. But that doesn't magically allow an arbitrary number of users to share spectrum, as each user's signal appears as noise to all the others. Eventually, you run out of signal-to-noise ratio.

    To increase capacity further, you can reduce the size of a cell, allowing you to re-use that spectrum in a more distant cell. You can also use "smart antenna" techniques to direct the RF energy in pencil-like beams to only the intended user. As far as I can tell, Perlman is merely using these time-worn techniques. All the rest is PR fluff. Picocells and femtocells have been discussed, analysed, proposed, and constructed. It's just a matter of cost (much of which has to do with property ownership/rights of way sorts of issues).
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