AT&T Carrier From
United States

The AT&T Carrier From United States is denoted by codes: 310 016, 310 030, 310 070, 310 080, 310 090, 310 150, 310 170, 310 280, 310 380, 310 410, 310 560, 310 670, 310 680, 310 950, 311 070, 311 090, 311 180, 311 190, 312 090, 312 680, 313 210. The followings IDs are called HNI (Home network identity). This code is created by the combination of two other Mobile Country Code (MCC) and Mobile Network Code (MNC). The first three numbers stand for the MCC and they are used in order to identify the region which the carried comes from (in the following example it’s United States). The last numbers of the HNI code are equal with the MNC and this ID is given for the specific mobile network operator.

Besides AT&T United States has assigned country code + 1. This number + 1 is equal with international calling code and it’s simply the telephone dialing prefixes used for calling AT&T numbers.
AT&T uses 2 GSM bands, 2 UMTS bands, 4 and 0 CDMA bands.. You can read the specific frequency bands in the table below. All bands of the AT&T are display in MHz units.
Another important information in AT&T United States architectures is the standard of used protocols. It also uses 7 protocols such as GSM, UMTS, LTE, CDMA. The ISO standard code of AT&T is US. You can see more info about this mobile network operator at https://www.att.com/. How to check AT&T coverage? How to check if your phone will work in United States?