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  1. Minsc's Avatar
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    #61  
    Quote Originally Posted by helpermonkey
    1) How is a softhandoff an advantage? I understand it to be part of how CDMA works... like me saying GSM has an advantage because it has freq. hopping and CDMA doesn't. You may be correct, but you didn't explain it, just puut the term out there.

    2) Noise canceling, how do you mean exactly?

    3) UMTS is not fundamentaly incompatible with the existing GSM equipment. I can't say this is true for all makers of GSM equipment as I am only used to Ericsson equipment, but on Ericsson it is not like going from TDMA to GSM. They are two completely different networks. On GSM all of the equipment does not need to be replaced. So there is compatability there.
    1. Soft-handoffs are advantageous because handing off is one of the prime causes of dropped calls. CDMA is unique in that the phone can be communicating with more than 1 tower simultaneously. (I think it can do up to 4 or 5 sites) So as you're driving down the highway, a CDMA phone is hooking up and spreading your conversation among multiple towers. As you get further away from a tower, the phone just drops that "thread", while continuing to communicate with the closer tower(s). With GSM, you can usually hear a very slight break in the communication - which is the "hard" hand-off.
    I'm certainly not suggesting that CDMA phones don't drop calls because like all wireless phones they do, however when it does happen it's most likely not because of a bad hand-off.

    Also, frequency-hopping isn't an advantage of GSM. It's meant to minimize co-channel interference, which is an inherent problem with GSM. Additionally, I don't think all GSM providers have implemented it.

    2. CDMA cancels out most background noise by default. This is why if you're talking to your friend who has a GSM phone and he's in a car driving at 70 down the highway, it sounds like quite a ruckus in the background. With CDMA, it's often impossible to tell that he's even in a car. Not a huge deal, but just another little nicety.
  2. #62  
    On point 2. not sure I follow you. CDMA is a multiplexing technology, but isn't the background noise (sound) detection a microphone / signal processing issue that could be done with either surely?

    It is of course a different phenomena to the ability of CDMA to treat intra-system interference as noise like as the signals from other handsets (that should have orthogonal codes) will mostly cancel out at the receiver.
  3. #63  
    WOW ... I'm no CDMA techie, but from my "raw empirical data" (my wife driving a Ford Explorer @ 70mph down the NJ turnpike with the back seat window down) I'd have to disagree with THAT statement! It sounded like she she was holding the phone out the back window while driving. (This was on Verizon).
    Quote Originally Posted by Minsc
    2. CDMA cancels out most background noise by default. This is why if you're talking to your friend who has a GSM phone and he's in a car driving at 70 down the highway, it sounds like quite a ruckus in the background. With CDMA, it's often impossible to tell that he's even in a car. Not a huge deal, but just another little nicety.
  4. Minsc's Avatar
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    #64  
    Hmmm, that is odd. I know that noise cancelling is part of the CDMA spec, and from my own personal experience it's an astounding difference. Most of my friends have T-Mobile and it's very obvious when they're in the car. My wife and brother both have Sprint, and usually I can't tell at all that they're calling me while in the car.
  5. #65  
    Maybe they keep the windows closed!
    Quote Originally Posted by Minsc
    Hmmm, that is odd. I know that noise cancelling is part of the CDMA spec, and from my own personal experience it's an astounding difference. Most of my friends have T-Mobile and it's very obvious when they're in the car. My wife and brother both have Sprint, and usually I can't tell at all that they're calling me while in the car.
  6. #66  
    Quote Originally Posted by Minsc
    1. Soft-handoffs are advantageous because handing off is one of the prime causes of dropped calls. CDMA is unique in that the phone can be communicating with more than 1 tower simultaneously. (I think it can do up to 4 or 5 sites) So as you're driving down the highway, a CDMA phone is hooking up and spreading your conversation among multiple towers. As you get further away from a tower, the phone just drops that "thread", while continuing to communicate with the closer tower(s). With GSM, you can usually hear a very slight break in the communication - which is the "hard" hand-off.
    I'm certainly not suggesting that CDMA phones don't drop calls because like all wireless phones they do, however when it does happen it's most likely not because of a bad hand-off.

    Also, frequency-hopping isn't an advantage of GSM. It's meant to minimize co-channel interference, which is an inherent problem with GSM. Additionally, I don't think all GSM providers have implemented it.

    2. CDMA cancels out most background noise by default. This is why if you're talking to your friend who has a GSM phone and he's in a car driving at 70 down the highway, it sounds like quite a ruckus in the background. With CDMA, it's often impossible to tell that he's even in a car. Not a huge deal, but just another little nicety.
    Minsc, how do you know that most drops on GSM are caused by failed handovers? I would argue that that is not true.

    On GSM handovers CAN be audible, but they should not be, and are not usually. So I am not buying that a hard handover is a disadvantage. In a normal handover the phone recieves a message from the tower it is "talking to" telling it to tune to such and such frequency. If the phone tunes to it and can not find the call, it returns to the old site, which does not stop transmitting that call until it recieves a message that the call was handed over succcessfully. Even a failed handover is not always audible, they can be in some circumstances though.

    I know what fequency hopping is for. My point is simply that it is a function of the GSM standard, just as a soft handoff in CDMA is. Sure you don't have to use it in GSM, but you would be foolish not too. The only reason I cna think of for not using it is because your network carries next to know traffic on some small network.

    You still did not explain number 2. You just say it does it. As mentioned by someone else, what does it? The network? I suppose it could, but it sounds much more like a function that should be left to the mobile to me. I admit I could be wrong on this. I don't claim to be even knowledgable on CDMA.
  7. Minsc's Avatar
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    #67  
    Quote Originally Posted by helpermonkey
    In a normal handover the phone recieves a message from the tower it is "talking to" telling it to tune to such and such frequency. If the phone tunes to it and can not find the call, it returns to the old site, which does not stop transmitting that call until it recieves a message that the call was handed over succcessfully.
    This is exactly the reason why. If the phone can't tune to the new tower for whatever reason and you're moving away from the current tower, the call will drop - because the current tower is now out of range. TDMA systems like GSM use a "break before make" procedure for handoffs, which is why it's called a hard handoff. (and is why you can often hear a slight pause in the conversation) The connection is physically broken before the new one is established. This is why the potential for dropped calls exists, sometimes the handoff gets botched for whatever reason. Just the opposite, CDMA is a "make before break" handoff.
    In practice, of course, the vast majority of handoffs are successful. But occasionally they do drop. If handoffs weren't a common source of dropped calls, then the CDMA engineers wouldn't have gone to the trouble of designing a better way to do it.

    You still did not explain number 2. You just say it does it. As mentioned by someone else, what does it? The network?
    I believe the noise cancelling is done at the handset level, by the codec. Not the network.
    Last edited by Minsc; 01/08/2005 at 02:38 PM.
  8. #68  
    I did a google of noise cancelling and GSM and there seems be lots of companies offering that option. So its not a CMDA specific technology.
  9. Minsc's Avatar
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    #69  
    I'm sure you can buy noise cancling headsets for any phone. How well they work is another matter. You're correct, noise canceling in the general sense of the word isn't a CDMA specific technology, although the type of noise canceling used by CDMA is proprietary and part of the spec - and it works quite well.
  10. #70  
    Quote Originally Posted by Minsc
    This is exactly the reason why. If the phone can't tune to the new tower for whatever reason and you're moving away from the current tower, the call will drop - because the current tower is now out of range.
    Minsc, once agian I am going to say that isn't correct. Some of the time, sure it could be, but usually not. Did you read my original post? In it I said "If the phone tunes to it and can not find the call, it returns to the old site, which does not stop transmitting that call until it recieves a message that the call was handed over succcessfully." Although the handover may be "hard" as opposed to "soft" that doesn't mean the call can not be recovered on the original tower. These things happen much faster than you could hear under "normal" circumstances. Under non-ideal circumstances, you could have your handover be audible, like if you are trying to handover due to interference and the interference is preventing the successful handover tot he new cell and you are forced to revert to the original "dirty" channel, sure that is going to sound bad. The idea that you are going to have difficulty going back to the original tower because you have left it's coverage area is wrong. You may have left the site's service area, but the coverage area of a site in an area with no coverage holes is much larger than it's service area. You handover to to another site when it is stronger than the serving cell by a specified amount of strength in dB and for a specified amount of time. So a handover can be triggered at say -50dB (super good coverage) or at -95 (usable but considered week). In the core of a network, most handovers on the street will be happening at good signal strength and a failed attempt at ahnding over should not result in a drop. I have not even mentioned subcell handovers that occure between different layers in a sector when subcells are enabled. The happen inside the coverage area of a cellsite with itself.
  11. Minsc's Avatar
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    #71  
    Quote Originally Posted by helpermonkey
    Minsc, once agian I am going to say that isn't correct.
    What isn't correct? My hypothetical situation?

    Some of the time, sure it could be, but usually not.
    Oh... So I guess it is correct?

    Did you read my original post? In it I said "If the phone tunes to it and can not find the call, it returns to the old site, which does not stop transmitting that call until it recieves a message that the call was handed over succcessfully."
    Yes I did read your post. Even an analog network does that. The point is that a GSM phone CANNOT communicate with more than 1 site at a time. When it attempts to connect to the new site, it has physically and absolutely dropped it's connection with the original site. There is a physical break in the connection, which doesn't occur in a CDMA system. RF is fragile, and if the break in communication lasts just a few milliseconds too long, the call drops. In a well deployed and well tuned network, this should happen very infrequently. But it does happen, and frankly any technology advancement that seeks to eliminate unnecessary breaks in the communication link is a good thing.

    Look, the point I'm trying to make here (and didnt' realize it would take this many posts to do it) is that the soft-handoff system that CDMA utilizes is superior to GSM's. I'm NOT saying that GSM is crap, or that anything about how the GSM network operates is crap. But newer technologies bring with them some advancements. This is one of those.

    Someone earlier had asked for pros and cons of CDMA and GSM. I thought I'd just bring to light an advantage for CDMA that hadn't yet been mentioned, and that's the soft-handoff technology.
  12. #72  
    Minsc,

    Please excuse me for being overly zelous. No offence was ment.
  13. Minsc's Avatar
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    #73  
    None taken. We both love our Treo's and that's all that matters, right?
  14. #74  
    Yah, I like to discus, but fear it often appears that I just like to argue. Thanks for understanding
  15.    #75  
    I was reading in another thread about Sprint's Vision data plan being $15.00/mo, but I swear....in the SF area it seems slow to me. I have never owned a Treo 600 on Sprint, but no less than 12 of my friends who have them -- all have Sprint. Without fail, everytime I have attempted to browse on one of them -- it's slow, slow, nauseating slow. Now I am certain someone will come behind me and say. That's not true. I live in Concord, I live in Berkeley, I live in SF, I live Oakland, I live in blah, blah and it's BLAZING fast. I can only speak subjectively about my experiences in 3 Sprint stores in the Eastbay and using my friends Treos and it is slow. It is certain that EDGE will not be that much faster, but that is why I started this thread to help others clarify what's best for them region by region. As for me:

    Not in a box.
    Not with a fox.
    Not in a house.
    Not with a mouse.
    I would not use Sprint here or there.
    I would not use Sprint anywhere.
    I would not get Sprint's Vision Plan.
    I do not like them, Sam-I-am.
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