AT&T, on the heels of its $2.5 billion purchase of Iusacell, now has reached agreement with NII Holdings to buy Nextel Mexico for about $1.88 billion.

The acquisition will give AT&T a network that covers about 76 million people in the Mexican wireless market, and answers in part the methods AT&T will use to assemble its network, acquire spectrum and amass customer scale.

As always, there are several proven ways for a mobile service provider to acquire spectrum assets.

A service provider can buy new spectrum, can acquire a firm that already has such assets, create more density in its transmitting network (using smaller cells), offload to Wi-Fi or other unlicensed spectrum, can use new air interfaces (fourth generation Long Term Evolution is at least 25 percent more spectrally efficient than third generation air interfaces), employ new radio technologies and, in the future, use shared spectrum.

By buying Nextel Mexico, AT&T will acquire about 20 MHz of spectrum in most of its local markets, in the 800-MHz range. That is important because such spectrum has optimal distance performance as well as in-building reach.

Iusacell owns about 20 MHz and 25 MHz of spectrum, also in the 800 MHz band, in most of its local markets, giving AT&T about 40 MHz to 45 MHz of combined spectrum.