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CDMA Pilot Pollution

Discussion in 'GENERAL Wireless Discussion' started by GLZ, Jun 3, 2007.

  1. bobolito

    bobolito Diamond Senior Member
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    You're right about that. I mixed up the numbers and forgot that each timing adv. is 550m not 500m and so I just calculated it would be 69TA to reach approx. 35 km. Sorry for the misinformation.
     
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  2. bobolito

    bobolito Diamond Senior Member
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    For the most part CDMA users are all in one channel, but in order to avoid channel overloads as a user moves from one area to another (prevents concentration of users in one channel), you are virtually "assigned" one channel based on some factors. So, two different CDMA phones can be standing next to each other using the same tower, but they may be on two different channels. And if they move together in one direction, they'll soft-handoff to the next site to continue on their corresponding channels rather than changing channels. Unlike GSM, the same CDMA channels can physically overlap over the same spot, otherwise soft-handoffs would not be possible. On GSM, they have to use different channels to overlap the same spot to allow handoffs (hard handoffs in this case). If two sites on the same channel overlap on the same spot on GSM, then you get interference and calls garble and drop if a handoff to a better, cleaner channel is not performed.

    Depending on allocated capacity, CDMA sites can carry several channels and will transparently move users from one channel to another depending on load. So contrary to popular belief, hard handoffs can happen on CDMA as well. ;)
     
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  3. rytard

    rytard Junior Member
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    This is very entertaining how i love to expand my knowledge lol
     
  4. Andy

    Andy Diamond Senior Member
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    This thread has been VERY informative and should be stickied somewhere, I think. :)
    You are absolutely correct about the CDMA channel allocation. Each CDMA phone will be "assigned" a default channel, based on some calculation they get from your phone number (I think). My phone will stay on the same channel, unless capacity reasons force my phone to a different channel- this can either happen when I initiate a call or during a call (as a hard handoff).
    CDMA cell sites are able to transmit several channels, and depending on the cards used, can either carry 32 or 64 calls per channel per sector from what I have learned.

    Andy
     
  5. Shwemp

    Shwemp New Member

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    Here is a site that has some dated but good info including a CDMA mobile channel selection tool. Look in the section called Non-Map Topics. The tool is called CDMA channel selection mobile station hash function.

    Welcome to the Wireless Wavelength

    Shwemp
     
  6. Yankees368

    Yankees368 Compulsive Signal Checker
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    Interestingly enough, I was on a 5th floor rooftoop in Manhattan today along Central Park, with a RSSI os -68 and a EC/IO of only 6 on my M1 today. Not bad considering how many sites I could see.
     
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  7. Bill Clinton

    Bill Clinton 10 years scandal free....
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    That was corrected to 64x550=35,200 meters

    bobolito Just out of curiosity... If you had a GSM phone and the nearest tower was visible but 40 kilometers away I am assuming you would not be able to use it. If you buy an antenna, amplifier, or repeater for a GSM signal for your home or car and the nearest tower is over 35,200 meters away that is also useless correct? I am just wondering if this is the case. I don't own a GSM phone but I may get one and keep my Sprint lines. There are Unicel towers near the location that I am thinking about, there is just poor service due to the mountains. I would be fine with an antenna but I am just wondering about driving and other times when you are over 35 kilometers away from the nearest tower. It sounds like you are really out of luck at that point. If you could let me know if I have this right I would appreciate it very much. Thanks
     
  8. KyleAndMelissa22

    KyleAndMelissa22 Woot Woot, Splat !!!
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    bobolito was right, anything over about 22 miles will not work.

    If there is absolutely no signal, a repeater can't magically make signal appear.
    Repeaters/amplifiers will boost signal that is already there. so if you get a bad signal in your house,
    just put the repeater near a window, and you should see some improvement within 10-30 feet.
    Same goes for the car.

    The closer to the tower, the better the call will be.
    Even close to the 22 mile limit, the call may drop long before that if the tower wasn't built to go that far.
    Line of sight is the key to a good cell connection (except high elevations).

    If you don't like being limited with GSM range, try using CDMA.
    I've used towers over 75 miles away (at Mount Mitchell, NC using a tower near Wilkesboro, NC on Carolina West).
    However, CDMA will work alot better in flat/lower terrain.
    If your up in the mountains, try using analog.
    PCS is the hardest to use at high elevations.
     
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  9. bobolito

    bobolito Diamond Senior Member
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    The problem with Timing Advance is not the signal strength, its the time it takes for the signal to travel from either the tower to the phone or from the phone to the tower. An amplifier is not going to make the signal go any faster so the delay for the signal to reach its destination over the air will be the same.

    As for amplifying signals that are not there, that's a partial truth. In theory there is always a signal present. The question is how strong/weak and clean the signal is so that the amplifier can turn it into something the phone can detect after being amplified. If you can't detect a signal on your phone, it doesn't mean that the signal is not there. It just means the signal is too weak for the phone to detect it and an amplifier may nor may not help. But again, that depends on just how weak the original signal is. With the right antenna and amplifier, you can get a signal to your phone that would otherwise be invisible to the phone.

    However, there are limits to what amplifiers can do. Sometimes the signal can be so weak, that not even the best amplifier and long range Yagi antenna can make it useful. And finally, sometimes it is not how weak the signal is, sometimes the signal comes with interference and the amplifier is going to amplify that noise as well and even if you can get the phone to detect the signal it may not be usable because of the noise/interference coming through.
     
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  10. rytard

    rytard Junior Member
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    i think if CDMA could elminate the problems of pilot pollution, NID borders, and reduced battery life that it would be far superrior to other technologies, does anyone agree?
     
  11. KyleAndMelissa22

    KyleAndMelissa22 Woot Woot, Splat !!!
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    I agree, just like on Sprint phones, choosing to roam only, or not.
    I'd like to see one big CDMA network that anyone can use, at any time, no restrictions, no roaming.
    Just one "BIG" network accessible to any CDMA phone.

    But to be realistic about it, this doesn't happen for free, and theres competition. It could never be one "big" network.

    The closest they've come is Alltel's Total Freedom, and perhaps others.
    But even total freedom isn't "total freedom."
    There are still minutes to worry about (nevermind MyCircle).
    Still, National freedom comes close as well. and i think it's worth every bit i pay for. :cool:
     
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  12. bobolito

    bobolito Diamond Senior Member
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    Well, if it didn't have pilot pollution, NID borders and reduced battery life, then it wouldn't be CDMA. It would be GSM. ;)

    Actually, any kind of spread spectrum type of technology (like WiFi or UMTS/HSDPA) will suffer from the same weaknesses. Bottomline, there is no perfect technology yet and I doubt there will be. If you want more throughput you need a wider channel, and the wider the channel the more battery it will consume. In addition, with more throughput you need a faster processor to handle the load, more memory buffers, etc. and that uses more power as well. So as you add more benefits, everything else tags along.
     
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  13. RadioRaiders

    RadioRaiders RF Black-Belt
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    If you are in an open area and have LOS to a GSM site over 35km away, and you have a signal, there's a pretty good chance that the GSM operator is trying to purposely cover that area and most likley has Extended Range features implimented so that you can connect to the site from up to 120km away. I really wouldn't worry so much about the 35km range. That's true in theory, but in reality most GSM operators have Extended Range, because it saves them $$ by not having to build more sites to cover rural areas.

    Too see if your local GSM operator has it, you can probably just ask them directly, as it's not "confidential" information. The problem may be finding someone who knows about it. Don't ask at you local retail phone shop, as those $5/hr monkeys usually know nothing about the network and are only trained to smile and say "have a great day!". Maybe if the operator has some kind of customer contact/complaint center you can e-mail to, they might be able to find out for you. Or you can get a GSM phone and go make some feild-tests yourself.
     
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  14. rytard

    rytard Junior Member
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    yes mabye it would act like GSM but the technology would still be CDMA
     
  15. rytard

    rytard Junior Member
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    I wish Verizon wouldnt have shut down their analog network (they did didnt they?) and still offered analog roaming because i dont have a signal at my dads house but on his analog phone that he used years ago on verizon he got a signal
     
  16. cheddar

    cheddar Senior Member
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    Verizon has not shutdown their analog network yet. I believe that analog cannot be shutdown until February 18, 2008. Someone please correct me if I'm wrong.

    If you have a recent phone than chances are the reason you cannot roam is because its a digital only phone. I'm not sure of the percentages but more and more phones do not offer analog roaming. I'm guessing your phone is an example.
     
  17. rytard

    rytard Junior Member
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    thats when it is required but it can do it in advance, it is all digital i believe all new verizon phones are
     
  18. Fire14

    Fire14 Easy,Cheap & Sleazy
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    They can't shut down Analog before the 2/08 date unless they have no customers left on it (or very, very few)

    As for the phones, Verizon still sells phones with Analog, your phone just happens to be one without it.
    So that is why you can't get a signal at his house.

    As for bobolito's comment, you do understand the "joke" he was trying to get at right?
    I guess not from your response.
     
  19. Bill Clinton

    Bill Clinton 10 years scandal free....
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    I use CDMA and I have for several years. Since I rarely use GSM I don't know much about it so I was just wondering about a few of these things and you were able to explain my questions quite well. I was thinking of possibly picking up GSM phone of my own. When I travel overseas I am given a GSM phone and I was considering just buying a quadband GSM phone and keeping my CDMA phones as well. Thank you very much for the help though. You gave me some very useful information.

    esto - Thank you for the very helpful comments also. I only use GSM when I am out of the country and when I am somewhere else the network is usually built out very well and I never have to worry about any of these things. Your post was very informative as well so I greatly appreciate your taking the time to help me out with this.
     
  20. AlanJP

    AlanJP New Member

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    Good info here... My experience has been that the 800 MHz carriers tend to have better coverage and less dropped calls in the rural areas than the 1900 MHz carriers. However, there are always exceptions.. like was said about cell site placement, altitude etc. I used to live outside Winchester in N. VA and had Verizon and because of the hills had a heck of a time keeping my signal. I got a Wilson dual-band mobile wireless amp (which also works with GSM) and used a 12" magnet mount antenna on the top of my truck. Wilson claims 10 times more powerful than your cell phone because the receiver sensitivity in the amp really picks up a weak signal and it increases the cell signal 10 to 50 times, which can sometimes mean about a 50 mile increase in signal range. I haven't ever had a problem dropping calls unless I'm just so far out in the boonies there is no signal at all. I like Wilson because the engineering is sound, they've been around over 40 years in the RF business, and their microprocessor technology automatically adjusts power needs based on signal strength so there is no cell site interference or messing with other cell users. May want to try that. Also, Wilson makes a dual band SOHO amplifier that works in-buildings or RVs or even cabin cruisers (marine). Good product. Check out PowerfulSignal dot com for a mobile kit and Lee can give you good tech support. I use the product; so that's my opinion.
     

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