Microsoft has already confirmed its participation at the Mobile World Congress (MWC) 2015 and now tech enthusiasts are eagerly waiting for the Redmond-based tech giant to unveil its latest Lumia smartphones at the upcoming trade show early next month.

According to Christian Today, there are rumors that Microsoft intends to unveil two Lumia smartphones at the MWC 2015 - the Microsoft Lumia 640 and Microsoft Lumia 1330. Tech website GSM Arena recently posted a leaked AdDuplex slide document that suggests AT&T will be offering the new mid-range smartphones in the United States.

Various reports suggest that the Microsoft Lumia 1330 device will sport a 5.7-inch touchscreen display with 720 x 1280 pixel resolution. It will be powered by a Qualcomm MSM8930AB Snapdragon 400 chipset coupled with dual-core 1.7 GHz Krait 300 processor. The other expected features of the device include Adreno 305 graphics card, 1 GB RAM, in addition to 32 GB internal memory. It is expected that the Microsoft Lumia 1330 will also features a 14-megapixel primary rear camera along with LED flash and auto-focus, plus a 5-megapixel secondary shooter. According to reports, the smartphone will run with Microsoft Windows Phone 8.1 OS.

The Lumia 640 will succeed the Lumia 630 that has already been launched in the Brazilian market. According to reports, the Lumia 640 for the U.S. market will feature a 5.0-inch screen with 720p. In addition, the smartphone will be powered by the basic Snapdragon 400 chipset coupled with 1 GB RAM.

Microsoft Lumia 640 is an entry-level smartphone that will come with an 8.7-megapixel primary rear camera and a 0.9-megapixel front-facing secondary camera. As of now, no details regarding the device's mobile operating system are available. As a result, there are speculations that the device could either run with the Windows Phone 8.1 OS or the most recent Windows 10 operating system.

If latest rumors are to be believed, the Microsoft Lumia 640 may be priced at $275 in the U.S. and will be sold through AT&T.