Is the rezound a CDMA phone?

Discussion in 'HTC Rezound' started by turkjey5, Nov 23, 2013.

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  1. turkjey5
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    turkjey5 New Member

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    I understand that CDMA phones don't have sim cards, yet the rezound has a sim and the LTE/CDMA network option.
    thanks
  2. mountainbikermark
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    mountainbikermark DF Super Moderator Staff Member Premium Member

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    CDMA is the phone call and text radio. It needs no SIM.
    Any phone that uses LTE for data on Verizon uses a SIM card.
    The Rezound uses both CDMA and LTE so it uses a SIM card.

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  3. acejavelin
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    @mountainbikermike is partially correct... the Rezound is a CDMA phone, but it is also a 4G/LTE and GSM phone, and more correctly it is called a Global Mode phone.

    Technically speaking, the Rezound can be activated and use CDMA networks without a SIM, but Verizon will not do it as they use the 4G/LTE SIM as a psuedo-MEID for the phone instead of the hardware MEID of the physical unit (this is why you can swap 4G/LTE SIMs on Verizon from phone to phone and it moves your number with it like GSM networks). Other carriers, such as Page Plus, do not have this restriction, but have agreements in place with Verizon not to activate certain devices anyways (they may, or may not, be a technical reason for this... I don't know). The MEID used to register on a CDMA network can be changed in the Rezound, it is done occasionally and activated on other networks with mixed results, by cloning a carriers native phone MEID into the Rezound. This is a... ummm... "questionable" practice, if you know what I mean.

    The Rezound is also a 4G/LTE phone with a multi-band LTE radio... it is tuned for Verizon's Band 13 4G/LTE network, but some users have been able to tweak the 4G radio and use it on other 4G networks such as AT&T's Band 17 LTE, although it is not a practice to be taken lightly as it does possess the possibility of bricking your device and making it non-recoverable unless you are S-OFF prior to the incident.

    And lastly, if your Rezound has recent firmware (4.3.605.2 or higher) it is also a fully functioning GSM phone, pop in a GSM SIM card, set the APN settings, and change it to Global Mode and away you go.
    Last edited: Nov 23, 2013
  4. turkjey5
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    turkjey5 New Member

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    Ace, as always thanks for a very informative reply!
  5. MotoXGirl
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    MotoXGirl Active Member

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    You seem to know CDMA well, I have a question, if you know, and would be willing to explain? Sorry... How does CDMA hashing work, and channels? What determines what a channel is?
  6. acejavelin
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    acejavelin Member

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    Wow... you really want to get into the nitty-gritty of CDMA don't you? :)

    I will be honest and say I only have slightly more than a general overall knowledge of what it is and how it functions, and since you are asking the questions you probably have the same knowledge already... it is a way of the handset to perform a mathematical calculation based on the networks available resources and it's unique identifier (typically the ESN or MEID number) and request a channel allocation from the carrier for the necessary packet transaction(s) to occur. A way of requesting available resources so to speak.

    The technical specification knowledge of it is mostly irrelevant though, even for the hard-core hacker, there isn't any real life use to the knowledge that you can manipulate to your advantage and CDMA is going away, slowly, but within 5-8 years, I think there will be very little of it as VoLTE is slowly being deployed and will eventually replace it.
  7. MotoXGirl
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    MotoXGirl Active Member

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    Yea, I more or less wanted to know just to know.. lol What is a channel? Is it a frequency? Is it standardized? Or are channels like the channels in Wifi in the regard that they are standard within the frequency?

    Thanks!
  8. acejavelin
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    acejavelin Member

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    Ok... I get what your looking for I think. CDMA is kind of hard to compare to WiFi, TDM, or FSK, it doesnt allocate a specific frequency or channel to a device, essentially it is one big channel on a single spread spectrum of frequency range, and each device's information is encoded (hashed) with its unique code using an SHA1 encryption and sent out in conjunction with all devices data, kind of mushed together, and each device is responsible for grabbing its own specific data. This has an advantage essentially unlimited capacity on a cell site , where every device shares the same bandwidth but the disadvantages as the number of handsets increase the available resources for that specific device become less common thus slower. It works on the principle that no devices going to have a continuous stream of data all the time but only needed in bits and pieces.

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  9. acejavelin
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    Imagine a stream, where everything flows out of a giant faucet, the water is the frequency channel, and each device is a kid along the shore with a specific color assigned to them, as each kid requests something and tells the source of the water what it's color is, pieces of it are then released into the stream in the form of colored ping pong balls, to get the information the kid has to grab their specific color of ping pong ball and get the pieces out of them and put them back to together... the wrong color ball doesn't do them any good so it is ignored. As more kids request stuff, more different colored balls are added to the stream. The balls don't come out in a specific order based on the time slot (red-blue-green-red-blue-green) or a specific section of the stream (red down the middle, blue on the far side, green on the near side), they are all just dumped out and the kids have to pull out what they need.
    Last edited: Nov 29, 2013
  10. FoxKat
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    FoxKat Resident Novelist...LOL! Staff Member Premium Member

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    Excellent analogy. The acronym CDMA stands for Code Division Multiple Assess. By dividing the entire spectrum of bandwidth using specific hash codes for each packet of information (colored balls for instance), it allows everyone to share the bandwidth peacefully. The analogy of the colored balls represents the hash code or personal identifier for each packet of information. Other systems use other methods of delegating portions of the entire bandwidth to each individual cell phone. TDMA uses Time as the division method where each cell phone is given a specific time slot in minute fractions of a second to access their own specific packets of information.

    So a channel can be a specific frequency such as that of the radio you listen to, or a time or code divided portion of a wide spectrum of frequencies as here on cellular, within the spectrum of frequencies allocated to the cellular carrier by the FCC (Federal Communications Commission).

    Another analogy would be baggage claim at the airport where all the bags are placed on the belt with no regards for order and go around and around until someone picks up the one with their name tag on it. If you don't pick it up the first time, it can be resent and picked up the next time around.

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    Last edited: Nov 29, 2013
  11. FoxKat
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    I've found another analogy that works even better than either of the two above.


    Imagine a room (channel) in which people wish to talk to each other simultaneously. If that room only had two people there would be no need to divide the conversations into packets to share the room fairly...they are the only ones in the room, so there is no competition. However fill that room with a lot of people and the "noise" level gets louder. If everyone were talking at the same time, and all spoke the same language, it could be very difficult to hear everything the person you are speaking to specifically is saying due to the noise level, resulting in missed words (lost data packets), and it's also quite possible that you might hear part of someone else's speech nearby and confuse it for that of your party's conversation (cross-talk).

    To avoid confusion, people in the room could take turns speaking (Time Division - TDMA), but that would still limit the number of ongoing conversations to only one at a time...not very efficient and there would be a lot of others waiting for their turn. They could speak at different pitches - some with deep voices, some with middle voices, and still others at high-pitched voices (Frequency Division - FDMA). This would allow several conversations to take place at once, but again there is the possibility of it getting too noisy to the point where again you would have lost packets and cross-talk. But what if you all spoke unique and completely different languages instead (Code Division - CDMA)?

    I'm sure most of you have been in a situation where there was a conversation nearby in a different language...you take notice at first, but soon the other conversation becomes background noise that isn't confusing you while having your own conversation since you can't understand it anyway. Your brain simply ignores it. CDMA is analogous to the last example where people speaking the same language can understand each other, but other languages are perceived as noise and rejected.

    Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can communicate. So each cell phone is given it's own code and all communications to and from that cell phone are broken into small packets of data, each with a header that contains that code. Analog waveform of sound from the microphone is encoded (AtoD), into a continuous string of digital data as a series of 0s and 1s. Then that streaming data is broken or portioned into smaller packets of data, perhaps 32K bits per packet, for instance, and sent off to allow them to travel quickly as multiple packets traveling individually and independent of one another at the same time.

    Those packets all have starting and ending marks, and each ending mark to one packet lines up sort of like puzzle pieces, with only one other packet's beginning...the one that's next in line. By each packet having the unique perfect lock-key connection to only the next one in line, it allows the packets to travel at different rates of speed and along completely different paths, totally irrespective of one another. They are then collected together at the receiving end, and by using the data contained in the headers they can be sorted into the right order, placed back end to end, decoded (DtoA), back into the analog audio waveform and sent to the speaker as essentially continuous sound.

    As those packets are sent out, all other devices listening for data that belongs to them will be looking at only the headers (a very small piece of data), and if the headers aren't properly addressed or coded with the specific code that belongs their own specific cell phone, it's perceived as noise and simply ignored since it needs to know the code in order to decode it into something it can understand. This both allows transmission of massive amounts of data from many multiple sources and to many multiple destinations, and allows massive amounts of irrelevant data to be quickly identified and ignored on the fly by those for whom the data wasn't intended.
  12. mountainbikermark
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    mountainbikermark DF Super Moderator Staff Member Premium Member

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    This is also why it has never been broken since its creation in WWII. It can be hacked at the cell but not after.
    That's just cool imo.
    Cyberdine will break into the LTE system after CDMA is no more if we haven't already voluntarily let it totally in .

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  13. FoxKat
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    Exactly. Each packet is encrypted with a unique hash code that's specific to the electronic serial number of the cell phone for which is intended and since every cell phone has a unique serial number, without having that serial number you can't decode the packets.

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