The Telecom Regulatory Authority of India has carved up the market into 23 different service areas referred to as "circles," which are further divided into categories: "metro" circles covering four major cities, "A" circles for regions with other large cities, "B" circles covering regions with smaller towns, and "C" circles for rural areas. Operators must have a separate license for each circle, and license fees vary depending on the category.

The circles are largely in line with India's 28 states, but several states, for example in the Northeast, have been combined, so that the list looks like this:

The government is phasing out the Chennai metro and has merged it with the Tamil Nadu circle for the purpose of service provider licenses, so from March 31 operators will pay a combined license fee for the two areas. But most operators still consider it a separate circle for the purpose of service provisioning, subscriber counts, and financials.

While metro circles account for just 5 percent of India's estimated 1.1 billion population, they make up close to 18 percent of its mobile subscribers. Metro and A circles have so far provided the majority of subscriber growth but B and C circles are fast catching up, and operators are turning their attention to rural India to tap into the vast potential these more populous regions provide.