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Thread: Cell Tower Radius

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    Cell Tower Radius

    Does anyone know the radis of a cell tower? A shot in the dark, I would guess it has a radius of 1.5 miles. Anyone like to correct that?

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    Re: Cell Tower Radius

    Originally posted by DigitalSounds
    Does anyone know the radis of a cell tower?
    It's going to depend on how it is configured. Carriers can choose to have a larger coverage radius at the expense of lower overall capacity or more capacity at the expense of the coverage radius.

    So, it's a big balancing act as carriers try to get it to meld well with their other cells in the area while still offering the needed capacity and still keeping their costs down by not installing more cells than are really needed.

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    Out in the boonies, it's a lot further than it is in cities -- as the other poster mentioned, this is for call capacity reasons.

    There is a limitation that GSM has in terms of distance, I think it's 25 miles or something like that. It's something like the number of bits in some register, yada yada...

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    I believe it's around 20 miles depending on the environment. If it's in a place like NYC where there's a lot of tall buildings, obviouslly the signal wouldn't reach as far as if it was in an open field.

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    When Murphy's Law is in effect: 20 feet short of your current location!

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    If a cell site is located on a perfectly flat area (say in the mid west somewhere), the site will broadcast from horizon to horizon, or line of site. It can go farther or less, depending on a lot of factors (height above ground, output power, Antenna gain, access threshold, so on....).

    In a TDM(A) (GSM is a form of TDM(A)), ther is a timing advance that must happen as you move farther away from a site. After a certain distance the timing advance counter maxes out and the phone loses synch.... and you drop. Now I have seen a TDMA call held at 30 miles from the serving cell, however the call was dropped due to reuse/interferrence, but it lasted about a minute, and the voice quality was sketchy, at best.

    In deisgn and operation, a cell site only covers a small area, 1/2 mile to 5 miles (can vary), and can only handle so many calls.

    The rule of thumb is that your connection is line of sight, if you can see the cell site, then you can make a call. Unless the site is under maintenance, or blocking.
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    Talking

    Thats crazy... I live in a normal residental neighborhood, yet, driving around say in a 4-5 mile circle I could count atleast 5 cell towers with many clusters and rows of cells on them. Granted this neighborhood is off a major interstate and a pretty popular shopping mall. I quess that has something to do with it.

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    just maybe


    GSM: now more than 1 Billion orGaSMs worldwide

    UPenn 2007

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    Also, no one mentioned here that 1900 MHz sites have a much much smaller radius than 850 sites.

    So, it mostly depends on the area. You've got your micro cells in malls, etc that run 5 watts, You have "boomer" cells running 300+ watts and several hundred feet above the local terrain, and everything inbetween.

    Take a look at some of the maps on my web page to give you an idea of the site spacing for both 1900 MHz and 850 networks.
    "Give me dBm, or give me death!"

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    You cannot make a tower transmit further by sacraficing capacity. That is completely untrue.

    Now, carriers often do put more towers in an area than they need (in places like cities) to increase capacity, but there is no balance between transmission radius and capacity.

    There is a theoretical limit to how far a tower can transmit because it won't be ablt to sync everything up properly. You're not going to hit this, because the signal won't get that far in the real world and this is not an advantage to any technology.

    Tower transmission distance varies greatly by terrain. Buildings, trees, hills, mountains, etc. all diminish a tower's transmission distance. Cell phones use regular line of sight radio signals. The more stuff that is in that line of sight between you and the tower, the less signal that gets through.

    You can't have cell sites running at 300+ watts and get better coverage. This is fine for a one-way device like a beeper because your beeper doesn't have to transmit back. Your cell phone has to transmit back and so the distance is limited to the distance that your cell phone can transmit. Now companies do transmit with greater power from the towers than your cell phone does because the towers have more sensitive antennas and many of them plus better digital signal processing units than your phone so towers are able to work with a more diminished signal than your phone is, but this only goes so far. Think of how some phones have better RF than others. It only goes so far. The tower transmits at a higher wattage to compensate for the fact that it performs better than your phone.

    Just because you count 4-5 cell sites doesn't mean that many are necessary. First, not all carriers might be on each site. If one site is a Verizon site, that doesn't help Cingular, Sprint, etc.

    800 does transmit further than 1900 in practical terms. How much further is debatable. The higher the frequency you get, the closer its properties are to visible light. That means that higher frequencies are more likely to be blocked by solid objects while lower frequencies are more likely to go through them. Think of when a car with a loud sterio pulls up next to you. You hear the bass. People exagerate the difference between the two. Yeah, 800 is better, but the number of cell sites matters more. 800 carriers are mandated by the FCC to cover 80% of the geographic area while 1900 carriers only have to cover 80% of the population. This makes a big difference.

    In a vacuum, 1900 and 800 transmissions would travel equally far (for an infinite distance) since there would be nothing to block or scatter the transmission.

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    Another good way to explain this is: Imagine two people, one with big ears and a big mouth (tower), and another with a tiny ears and mouth (phone). The tower with its perfect wavelength antennas and preamplifiers, give it a finely tuned ability to hear your phone. Combine that with the ability to transmit higher power and you have an excellent combination.

    Towers running 300 or more watts ERP can and do exist. Just north of I-80 in PA comes to mind.

    Here's a link to a site in Clinton County, PA I know of. It's running 352 watts, and covers quite a chunk of land.
    http://wireless2.fcc.gov/UlsApp/UlsS...5&licKey=11689

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    Mobilegirl knows her stuff

    1. There is no federally mandated max distance a tower can transmit (at least in the USA/Canada.) Instead, the FCC has limited the wattage of the transmitters. (I don't remember the max number) It is like a WiFi base station...some transmit further than others based on location, obstacles, antenna gain, etc.

    2. A few more notes on 800 vs. 1900. First 800 has been around for about 15 years longer than 1900. So the providers have had many more years to make the coverage good! I am willing to bet that 850GSM won't be as good as 850TDMA to start, because TDMA signals behave differently than GSM signals. They can't just put up a GSM tower where a TDMA tower was and expect the same level of service...

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    Originally posted by smitty825
    Mobilegirl knows her stuff 2. A few more notes on 800 vs. 1900. First 800 has been around for about 15 years longer than 1900. So the providers have had many more years to make the coverage good! I am willing to bet that 850GSM won't be as good as 850TDMA to start, because TDMA signals behave differently than GSM signals. They can't just put up a GSM tower where a TDMA tower was and expect the same level of service...
    GSM is a form of TDMA! So is iDen.
    Moderator yahoogroups forum T-Mobile-US http://groups.yahoo.com/group/T-Mobile-US

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    very true, GSM is just a better version of IS136, there are only 2 technogolies, CDMA and TDMA

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    Very true. A tower transmitting at a certain frequency and wattage will be received equally at a distant spot no matter if it is transmitting trational TDMA, GSM or analog.

    Secondly, 1900 MHz networks will NEVER have the coverage of 850 networks. Primarily because the law doesn't require it, but because a provider would bankrupt itself putting up the amount of towers required to match 850 service. (in populated areas, this doesn't matter. They'd need that many towers anyway)
    PCS providers at the very MOST will be nothing more than "road-atlas" style coverage with blotches in individual towns, especially out west.

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