New reports suggest that T-Mobile is working on a LTE variant of the popular Nokia Lumia 810, which is exclusive to the carrier. An FCC filing has popped up online, which points to a mysterious "RM-878X" model, believed to be the LTE variant of the Lumia 810.

T-Mobile has been prepping for the launch of its first LTE network in Las Vegas, with Kansas City soon to follow. The carrier also plans to extend LTE coverage to 100 million Americans by mid-2013. CTO Neville Ray announced at the recently concluded CES that the faster access would go live in Las Vegas within "weeks."

Now, per reports, the FCC filing fuels speculations that the carrier's Lumia 810 could be up for an upgrade to support the faster LTE speeds and may make its way to T-Mobile in June.

"We all know Lumia 810′s Firmware variant is RM-878. But on FCC there is one recent entry with name RM-878X and it has passed test for LTE 1700 Frequency (T-Mobile's LTE frequency)," reported Nokiapoweruser.

The report points out that the RM-878X has "a final action date of December." Moreover, the original non-LTE Limua 810 or RM-878 is also listed and has October 2012 as its action date.

According to the report, the RM-878X has confidentiality till June 24 and, therefore, no images of the device are currently available. The report also suggests that T-Mobile is set to get the LTE variant of the Lumia 810 from June.

"So, may be be T-Mobile is going to get LTE variant of Lumia 810 from June or it may be a new device, possibility of which is less. Or, as some recent rumors have it, may be a software update will enable the LTE on Lumia 810 in June," notes the report.

With T-Mobile gearing up to prepare its smartphone line-up to support LTE, it remains to be seen when the Nokia Lumia 810 with LTE will hit the shelves.