Infrastructure REITs have found a profitable calling in life — assisting the nation’s biggest telecommunication carriers in moving from 3G to 4G wireless networks. The largest infrastructure REITs are benefiting from strong demand generated by the four major wireless carriers, which are upgrading their networks and wireless services.

This transition — combined with growing usage of smartphones, games, music and video services — is driving demand for tower space. In pursuing a strong growth strategy, infrastructure REITs have become highly leveraged. Consolidation among wireless carriers has also made the REITs more dependent on a limited number of tenants. Through June 12, infrastructure REIT returns totaled 8.2 percent. Although returns have increased from 4.8 percent in 2013, they remain below the 14.1 percent FTSE NAREIT All Equity REIT average.

The infrastructure sector’s two largest REITs are in the cell tower industry and comprise more tha