The Samsung Galaxy Note7 is the first commercially [almost] available smartphone to support 4x4 MIMO. The feature is supported by the Qualcomm Snapdragon 820 but only if the handset is equipped with four network antennas for simultaneous connections. Well, the Galaxy Note7's hardware does support this in conjunction with Qualcomm's X12 LTE model. And although there are no US carrier that supports 4x4 MIMO right now, at least we know that the Snapdragon variant of the Note7 does. This feature is not supported on the Exynos variant of the Galaxy Note7 since it does not have the same X12...
Source: http://www.gsmarena.com/galaxy_note7_can_connect_to_4_simultaneous_lte_bands_with_4x4_mimo-news-19886.php
