What is a Mobile Country Code (MCC)?

Mobile Country Code (MCC) Explained

A Mobile Country Code (MCC) is a three-digit number that uniquely identifies a country or geographic area for mobile telecommunications. MCCs are a critical component of the international mobile subscriber identity (IMSI) and are standardized by the International Telecommunication Union (ITU).

Purpose and Function

The primary purpose of MCCs is to identify the country in which a mobile subscriber is registered. This identification is essential for:

• International Roaming: When a mobile device connects to a network outside its home country, the MCC helps route calls and data correctly.
• Network Identification: Combined with the Mobile Network Code (MNC), the MCC forms the first part of the network identifier.
• Billing and Accounting: MCCs facilitate accurate billing between operators for international services.

MCC Allocation

MCCs are allocated by the ITU and published in the ITU-T Recommendation E.212. Each country or geographic area is typically assigned one MCC, though larger countries with extensive mobile networks may have multiple MCCs. For example:

• United States: 310, 311, 312, 313, 314, 315, 316
• Russia: 250
• China: 460, 461
• India: 404, 405, 406
• United Kingdom: 234, 235

MCC in the IMSI Structure

Within the IMSI (International Mobile Subscriber Identity), the MCC occupies the first three digits. The complete structure is:

IMSI = MCC (3 digits) + MNC (2-3 digits) + MSIN (9-10 digits)

For example, in the IMSI 310150123456789:

• 310 is the MCC (United States)
• 150 is the MNC (AT&T)
• 123456789 is the MSIN (Mobile Subscription Identification Number)

Regulatory Aspects

MCCs are regulated internationally to ensure global interoperability of mobile networks. The ITU manages the allocation process to prevent conflicts and ensure efficient use of these resources. Changes to MCC assignments are relatively rare and typically occur only with significant geopolitical changes, such as the formation of new countries.

Technical Implementation

In mobile devices, the MCC is stored on the SIM card and is used by the device to identify its home network. When roaming, the device compares the MCC of the current network with its home MCC to determine if it's in a foreign country, which triggers specific roaming behaviors and protocols.