苹果推出了三种型号的iPhone 5 —— 选购指南
Apple has finally made its latest iPhone compatible with LTE networks. But it’s not all good news for the company’s customers. Due to 4G LTE fragmentation, Apple has had to make three different models of the iPhone 5. Where the iPhone 4S was a dual GSM/CDMA device, meaning one model for all carriers, the LTE-enabled iPhone 5 comes in two separate GSM models and one CDMA model. This means that consumers will have fewer choices when switching carriers, and that LTE access will be limited when traveling abroad.
Since carriers utilize different radio frequencies (also known as frequency bands) for LTE service, Apple has had to diversify its iPhone 5 portfolio. This largely has to do with the fact that 4G LTE is still in the early stages of development, compared to more mature networks like 2G and 3G. It’s a messy situation that Android handset makers like Samsung and HTC have been dealing with when it comes to their 4G LTE devices. For example, the Samsung Galaxy SIII comes in nine model variants, five of which are specific to North American carriers.
The three iPhone 5 models include: GSM model A1428 that supports LTE Bands 4 and 17; GSM model A1429 that supports LTE Bands 1, 3, and 5; and CDMA model A1429 that supports LTE Bands 1, 3, 5, 13, and 25.
In layman’s terms, this means an iPhone 5 user who wanted to jump from, say, AT&T to Verizon or vice versa, would have to buy a new handset, since AT&T runs a GSM network and Verizon is CDMA. And where owners of GSM handsets previously enjoyed wide compatibility with foreign networks, LTE fragmentation means that AT&T customers using an iPhone 5 in Europe, for example, won’t be able to take advantage of LTE speeds while abroad and will instead get kicked down to the 3G network.
“With 2G, pretty much everything has matured to use four main frequency bands,” IHS analyst Francis Sideco told Wired. “And the components have matured enough so there are a lot of multiband components out there. 3G is in a similar state, where the bands are known and components are becoming more integrated with multiband capability…. When we get to LTE, neither one of those things is true. The bands that are being selected by operators globally have not coalesced, nor are the components mature enough where they are integrating to the same degree as far as multiband capability.”
The GSM A1428 model appears to be made specifically for AT&T, which is the only carrier that uses both LTE Bands 4 and 17. It will also support T-Mobile’s U.S. LTE network as well as several Canadian networks. But don’t expect any LTE service outside of North America — currently no carriers in other countries use Bands 4 or 17. Even though GSM networks are more common worldwide, this particular iPhone 5 model is not a global phone when it comes to LTE support. Instead, Apple has opted to make a second GSM model for other countries. Model A1429 supports the three more common LTE Bands in places like Asia and Europe, but none for North America use.
The CDMA phone, however, is more of a global device. It supports the same three LTE bands as the non-U.S. GSM phone, as well as the two main bands used by U.S. carriers Verizon and Sprint. Another benefit to the CDMA phone is that it supports GSM/EDGE radio frequencies, while the GSM phones do not support CDMA frequencies. Unfortunately, that GSM support is limited to international use for stateside customers. What is oddly missing from all three phones is LTE support for a large portion of Western Europe, which uses LTE Band 7.
苹果一共推出了三种型号的iPhone 5来适配全球不同国家的4G-LTE网络。但并不是对于所有运营商的顾客来说都是好消息。iPhone 4S是CDMA/GSM双模手机。这意味着在3G/2G网络上适配所有合作运营商。支持LTE网络的iPhone 5却不得不分成两种GSM型号和一种CDMA型号。这将限制用户在转换运营商时的选择。而且当你出国使用你的手机功能（主要指4G）将受到限制。
当运营商利用不同频段来提供4G-LTE服务时，苹果只能将iPhone 5分成不同的版本。这只能说是因为LTE刚刚起步，还不像3G和2G一样成熟。其它Android手机制造商像HTC和三星则用看起来比较麻烦的方法来适配不同的LTE网络。比如三星的Galaxy SIII就分成了9个不同的版本，其中5种就是为了北美洲。
这3种型号分别是GSM A1428支持LTE频段4和17；GSM A1429 支持LTE频段1、3和5；和CDMA A1429支持LTE频段1、3、5、13和25。
说白了，iPhone5的用户在从at&t转网到Verizon时必须要购买一个新手机（不然放弃使用4G），反之亦然。那些拥有GSM手机的人以前享受着全球范围的兼容性。LTE的分裂造成了一个at&t的用户想要将他的手机带到欧洲使用，但是却不能使用快速的4G网络而不得不使用3G。
在2G时代，一切都很成熟，我们只使用4个频段，而且有很多支持多频段的芯片。3G也是类似的状态，有很多这样的芯片。到了4G-LTE，这些都没有，全球不同运营商的频率还没有被整合到一起，没有芯片支持所有的频段。
GSM A1428型号看起来像是为北美洲的运营商所制造（主要是at&t），目前在美国只有at&t使用这个频段，将来可能有T-Mobile USA。另外还有加拿大的几个运营商支持这几个频率。在北美之外，没有任何运营商使用这个频段。iPhone 5不再是个全球手机，作为替代，只能另外推出一个GSM A1429型号来支持亚洲和欧洲地区的运营商网络的iPhone 5(不支持北美任何一家运营商）。
CDMA A1429支持的频段更多一点，包括了非北美GSM运营商使用的频段和美国两家CDMA（Verizon Wireless和Sprint）运营商的频段。CDMA型号同样支持GSM网络，但是仅在美国外可以使用。奇怪的是为什么三款型号都不支持西欧的7频段。
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