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휴대전화 세가지 신호 전송방법
Three signal carriers
아무전화나 사면 안됩니다. 다시 사야 합니다.

Phone  GSM Vs CDMA : What Is Difference and Which Is Better?

Three signal carriers 세가지 신호 전송방법
1. GSM [Global System for Mobile Communications]. As its name implies, this standard was developed for, and has been adopted by, almost the entire globe as the way to communicate via cellular calls.

An alternative cellular standard known as
2. CDMA [Code Division Multiple Access] is used by many carriers around the world. It is most popular in the United States and Russia, but it’s also used in some Asian and African countries, often alongside competing GSM carriers.

3. LTE [ Long Term Evolution ] LTE is a new standard that’s come into vogue over the last few years. LTE 는 아래를 읽어보세요
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Here’s what cell phone users stuck on choosing between them should know before purchasing a phone.

# GSM vs. CDMA : What’s Better?

GSM and CDMA are different ways to accomplish the same goal, and the fact that extremely popular networks are built on each simply proves that it’s the quality of the network, not the standard, which is important. For instance, in the United States,

Two of the four major carriers
GSM for (AT&T and T-Mobile)
GSM phones are able to be UNlocked and moved between carriers, but

CDMA for (Verizon and Sprint)
CDMA phones are often LOCKed to a single carrier and unable to be transferred.

* 헌데 이 두가지 신호 전송방법을 가지고 있는 전화도 있다는데??

Additionally, most phones only come in GSM or CDMA models, so your choice of phone could determine which standard you end up using, and it all depends on which carriers are available to you in your area.
Some areas may be better covered by GSM-providers, while
CDMA-providers will have better coverage in other areas.

# What Phones Support Which?

Many phones are compatible with either GSM or CDMA, but not both.
For CDMA phones, you will need to buy a phone made for your specific carrier, and the easiest way to do this is buy directly from your carrier. For example,
if you want an iPhone on Verizon, you need to buy a Verizon-branded iPhone — not a Sprint- or AT&T-branded iPhone — because it has the specific bands and compatibility with Verizon. However, if you ever want to leave Verizon, you won’t be able to take your phone with you; it is locked to that carrier.

If you don’t want to be trapped with one carrier, however, you can also look for unlocked GSM phones from third-party retailers — these phones will work with any GSM carrier simply by popping in your SIM card.  For example,
Amazon sells tons of unlocked GSM phones, and Google sells their Nexus 5 and a couple Google Play Edition phones unlocked. Any retail or online store dealing in cellular phones should provide information regarding the networks a phone works with.
You must be careful when examining a phone’s network compatibility, though. Phones sold in markets that service both standards often come in a GSM version or a CDMA version, but only a few phones are compatible with both.
If you buy a CDMA phone from a third-party retailer, you’ll need to call your carrier to have it activated.
If you buy a GSM phone, you’ll need to purchase a SIM card to put into your phone that will activate your phone’s network capabilities.

Owners of CDMA phones don’t need to worry about SIM cards, but this is more a curse than a blessing. CDMA phones bake in compatibility restrictions that are difficult to get around, while GSM owners can simply take out their SIM and replace it with one from another carrier. Most CDMA networks do not allow the use of a phone originally purchased from another carrier even if the phone is otherwise technically compatible.
This is an important restriction to remember when going with a CDMA network. If you decide to switch networks later you’ll likely need to buy a new phone even if the network you’re switching to also uses CDMA.
While GSM is more open, the frequency bands supported by a phone can still restrict access. There’s a number of bands from 380 MHz to 1900 MHz and the bands used can vary from market to market. You should double-check your local carrier’s band usage and make sure the phone you’re buying supports the same. With that said,

GSM is concentrated around a core of four bands, those being 850, 900, 1800 and 1900.
A phone that supports all four can be used in most countries, which is why GSM phones compatible with all four bands are often called a “world phone.”
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LTE [ Long Term Evolution ] Cometh, And Carries Confusion
If you now understand the importance of GSM and CDMA, awesome! Now let’s entirely destroy your assumptions by talking about the newcomer, Long Term Evolution (LTE).
LTE is a new standard that’s come into vogue over the last few years. Though based on the principles of GSM, LTE is its own separate standard that operates apart from existing GSM and CDMA networks — it’s the real fourth generation of cellular data.

The highest adoption of LTE can be found in South Korea, where it commands the majority of the market, but it is also popular in Japan, Australia, Sweden, and the United States. So far it’s used primarily for data, but standards have been drawn up for using LTE as a replacement to traditional cellular networks. Verizon Wireless in the US, for example, has announced its plan to roll out LTE-only phones in late 2014.
This standard uses a SIM card, so users can switch networks by replacing the SIM if the phone is compatible with the new network. With that said, at this time phones that use LTE generally use it only for data, but not for voice. This means CDMA/LTE phone owners are still locked into a network. That will change as carriers like Verizon move to LTE-only networks, but this process could take many years.
While it has the potential to be a global standard, there are some obstacles in the way. Outside of South Korea there’s no market where LTE’s reach is more than a quarter of the services available. South Korea in general, and Verizon Wireless in the US, are exceptions to the rule; in most markets, even carriers that offer LTE only offer it in a slim selection of the total area they cover.

And then there’s the problem of spectrum. Remember how GSM/CDMA operates on many different bands? The same is true of LTE. You need to check that the compatibility of your phone matches the frequency band supported by your carrier, and you won’t be able to use an LTE phone on other networks with the same standard, but a different frequency band.
It’s unclear at this point if this standard will ever become “global” in the same way as GSM, which settled on a core of four frequencies across the world that are supported by most GSM phones.
# Wrapping It Up
Take a deep breath; it’s time to review this buffet of confusing information.

First, neither GSM or CDMA is technically better; they ultimately provide the same service and the quality of a network depends on the carrier, not the cellular standard used.

Second,
GSM phones can be unlocked and switch carriers, whereas
CDMA phones are locked to a carrier. It’s usually cheaper to buy unlocked GSM phones than on-contract CDMA phones.

Third, you need to check what bands your chosen phone supports carefully. Most either work on GSM or CDMA, and both standards offer multiple frequencies that differ across the globe.

Finally, LTE is being rolled out as a potential global standard, but it falls victim to even more frequency division than GSM and CDMA. The technology also suffers from limited adoption because it’s relatively new.
Hopefully this has cleared up any questions you had, but cellular service is undergoing constant evolution and the standards commonly supported by phones can change from year to year. Feel free to leave your questions and comments below.
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Comment ;
I live in Arizona. couple of questions. I have a Samsung Galaxy S4. It’s both CDMA and GSM. I’m switching it over to straight talk. What does Verizon towers use, CDMA or GSM ?
Also, I’ll be in Alaska for a couple of months and I saw they don’t support CDMA. If I go with CDMA will I still be able to use the phone while I’m in Alaska?