The number of LTE subscribers is set to more than double in 2013, according to a forecast released Tuesday from IHS iSuppli. According to the report, worldwide LTE subscribers will surpass 198.1 million in 2013, a 115 percent increase from the 92.3 million last year, according to an IHS. 

Numbers from carriers back up those numbers. For instance, MetroPCS recently reported that subscribers operating on the company's LTE network increased by 117 percent from the third quarter to the fourth. Meanwhile, Verizon Wireless said it added 2.3 million LTE-capable devices (1.6 million smartphones), up from 1.4 million LTE-capable devices in the third quarter. 

IHS points out that LTE has surged by a factor of 22 to 13.2 million subscribers in 2011, and then jumping another 599 percent in 2012 to nearly 100 million subscribers. 

By 2016, IHS forecasts that LTE will claim more than 1 billion users, equivalent to a five-year compound annual growth rate of 139 percent.

Wayne Lam, senior analyst for wireless communications at IHS, said there are still significant challenges ahead. 

“Rapid adoption will drive design innovations, particularly in smartphones, but issues like spectrum fragmentation will also remain an overhang for the LTE industry that requires attention," Lam said in a statement. "Overall, however, the LTE space will be less worried about rifts or divisions in technology, and more concerned with laying the foundation for sustained growth across the entire LTE landscape.”

IHS also points out that interoperability across multiple carriers and spectrum holdings is far from consistent, currently registering more than 40 different frequency spectrums.