中國(guó)有3家，美國(guó)其實(shí)也只有4家，另外還有一些Local，只能在當(dāng)?shù)赜?，可以忽略，還有一些實(shí)際上是虛擬運(yùn)營(yíng)商，沒(méi)有自己的網(wǎng)絡(luò)，租用的都是4大的。
1.Verizon
CDMA：850MHz，1900MHz
CDMA EVDO/CDMA2000(3G):850MHz，1900MHz
LTE(FDD):700MHz(Band 13)，1700Mhz(Band 4)
2.Sprint
CDMA:800MHz(Band 10),1900MHz(Band 2)
CDMA EVDO/CDMA2000(3G):1900MHz(Band 2)
LTE(FDD):800MHz(Band 26)，1900MHz(優(yōu)先,Band 25)
WiMAX(已終止):2500MHz
LTE(TDD):2500MHz(Band 41)
3.T-Mobile
GSM:1900MHz，850MHz
WCDMA(3G，HSPA+):1700/2100MHz(成對(duì))，1900Mhz
CDMA EVDO/CDMA2000(3G)：1700/2100MHz(成對(duì)，優(yōu)先)，1900MHz
LTE(FDD):1700/2100MHz(成對(duì)，優(yōu)先，band 4)

4.AT&T
GSM:850MHz，1900MHz(個(gè)別地區(qū))
WCDMA(3G，HSPA+):1900MHz(優(yōu)先),850MHz
LTE(FDD):1700MHz/2100MHz(成對(duì)，優(yōu)先,band 4)，1900MHz(Band 2)，700MHz(Band 17,29)

在國(guó)內(nèi)買(mǎi)的手機(jī)要在美國(guó)使用，需要仔細(xì)看說(shuō)明，以T-Mobile為例：

2G(圖標(biāo)顯示E)：T-Mobile's GSM network operates in 850 MHz and 1900 MHz frequencies.A device is only able to use 850 MHz or 1900 MHz, it can still use T-Mobile's domestic network.

3G(圖標(biāo)顯示3G)：T-Mobile's UMTS network operates in Band IV, which uses 1700 MHz and 2100 MHz frequencies. Specifically, T-Mobile uses the 1700 MHz frequency to send information to cell sites and then uses the 2100 MHz frequency to receive information. A device must be able to use both frequencies to use T-Mobile's domestic UMTS network.

4G(圖標(biāo)顯示H+)：T-Mobile's HSPA+ network operates on the same band as our 3G network, Band IV, which uses 1700 MHz and 2100 MHz frequencies to transmit voice and data services. The 1700 MHz frequency sends information to cell sites and the 2100 MHz frequency receives information.
T-Mobile is switching some 1900 MHz frequency from EDGE to HSPA+. This will allow devices that work on 1900 MHz, such as AT&T devices, to use our 4G network.

4G LTE(真正的4G):T-Mobile’s 4G LTE network will operate on the same band as our 4G HSPA+ network, Band IV, which uses 1700 MHz and 2100 MHz frequencies to transmit data services.
4G LTE does not carry voice services, so calls will fall back to our HSPA+ network until voice over LTE (VoLTE) software is ready.
T-Mobile’s 4G LTE equipment will be the newest and most up-to-date of any carrier.

Ultra.me公司：For voice and text, you need a tri-band or quad-band phone that supports either the 850mhz or 1900mhz frequency.
Phones that support 1900mhz will get data from us at 3/4G speeds in most of our coverage areas.

由于CDMA模式的手機(jī)很多不是機(jī)卡分離的，因此，國(guó)內(nèi)人到美國(guó)大部分使用AT&T和T-Mobile的網(wǎng)絡(luò)（有一個(gè)例外，中國(guó)電信漫游到美國(guó)，4個(gè)公司的信號(hào)都可以使用，前兩個(gè)信號(hào)好一些，后兩個(gè)差一些，漫游費(fèi)用也不一致），到美國(guó)后需要的手機(jī)（GSM/WCDMA）是這樣的：

基本通話(huà)：3頻及以上（900M,1800M,1900M,850M）
上網(wǎng)：除了以上

WCDMA(UMTS,HSPA+)：除了國(guó)內(nèi)所用的2100M（聯(lián)通，Band1），要求至少一個(gè)1900M(Band2)，最好還要有1700M(Band4)

FDD LTE：Band4(首選，甚至是必須的)，Band2(1900M)，Band5(850M)