Nokia has launched its third smartphone under the Lumia series - Lumia 900 - at the 2012 International Consumer Electronics Show (CES).

The smartphone, which will come exclusively to AT&T in the coming months, will be the first of Nokia's Windows Phone-based range to feature high-speed LTE connectivity.

"The introduction of the Nokia Lumia 900 with AT&T is another significant milestone in the ongoing rollout of Nokia's global smartphone strategy," said Chris Weber, President of Nokia Americas. "The Nokia Lumia 900 is designed specifically with the US in mind and the announcement of this collaboration with AT&T, in addition to other recent announcements, signifies a new dawn for Nokia in the US," he added.

However, the Lumia 900 will face cut-throat competition from the Samsung Galaxy S2, which is one of the best-selling smartphones in the Android camp. The Galaxy S2, which runs on the Android 2.3 Gingerbread OS and sports Samsung's TouchWiz UI, comes in three variants - on AT&T, T-Mobile and Sprint, whose version is called Samsung Galaxy S2 Epic 4G Touch.

Let's see how the Lumia 900 fares against the Samsung Galaxy S2:

Display: The Lumia 900 sports a 4.3-inch WVGA AMOLED ClearBlack Display offering resolution of 800 x 480 pixels.

Both the T-Mobile and Sprint versions of the Galaxy S2 have 4.52-inch display screen, whereas the AT&T version retains the 4.3-inch screen of the Galaxy S2 version sold worldwide. The Galaxy S2 Epic Touch 4G comes with 4.52-inch (about 206 ppi pixel density) 800 x 480 pixels Super AMOLED Plus capacitive touch screen display. All the variants of the Galaxy S2 have Corning Gorilla Glass display protection.

Size:  The Lumia 900, which weighs 160 grams, has a dimension of 127.8 x 68.5 x 11.5 mm.

On the other hand, Sprint's Samsung Epic 4G Touch comes with a 129.5 x 68.6 x 9.6 mm dimension and weighs 129 grams, while the T-Mobile version has 131 x 70 x 9 mm dimension. As the AT&T version retains the 4.3-inch display, it has dimension of 125.3 x 66.1 x 8.5 mm and weighs 116 grams

Operating System:  The Lumia 900 runs on the latest version of Microsoft's Windows Phone 7 operating system called Mango (Windows Phone 7.5), while the Galaxy S2 runs on Android 2.3 Gingerbread OS and will get an Ice Cream Sandwich upgrade soon.

Processor:  The Lumia 900 is powered by a 1.4 GHz Qualcomm APQ8055 Snapdragon processor and Adreno 205 GPU. On the other hand, the Sprint and AT&T variants of the Galaxy S2 are powered by a dual-core 1.2 GHz ARM Cortex-A9 Mali-400MP GPU Orion chipset, while the T-Mobile variant is powered by a 1.5 GHz dual-core Qualcomm APQ8060 processor.

Camera: Both smartphones sport rear-facing 8 megapixel cameras. On the front, the Lumia 900 has a 1.3-megapixel camera, compared to the Galaxy S2's 2 megapixel shooter. The Galaxy S2 scores over the Lumia in terms of video capture, as the former can capture HD videos in 1080p compared to the latter's 720p.

Connectivity: The Lumia 900 supports HSDPA, 21 Mbps; HSUPA, 5.76 Mbps, LTE, Cat3, 50 Mbps DL, 25 Mbps UL. On the other hand, the T-Mobile Galaxy S2 version has HSDPA 42 Mbps support while the AT&T version has HSDPA 21 Mbps support. Both variants have HSUPA 5.76 Mbps. The Epic 4G Touch has Rev. A up to 3.1 Mbps.

WLAN, Bluetooth, and USB: The Lumia 900 supports Wi-Fi 802.11 b/g/n, NFC, Bluetooth version 2.1 with A2DP, EDR and microUSB v2.0, HS.

All variants of the Galaxy S2 have Wi-Fi 802.11 a/b/g/n, DLNA, Wi-Fi Direct, Wi-Fi hotspot, NFC, Bluetooth 3.0 version with A2DP and HS, microUSB 2.0 version (MHL) and USB-On-the-go.

Memory: The umia 900 has 16GB internal storage and 512 MB RAM. There is no microSD card slot. However, Nokia offers cloud storage on SkyDrive. On the other hand, the T-Mobile and AT&T variants of the Galaxy S2 boast of 16/32 GB internal storage and via a microSD card slot this can be expanded up to 32 GB. Sprint's Galaxy S2 Epic 4G Touch comes only with 16GB internal storage with expandable microSD card storage.

Battery:  The Lumia 900 has an 1830mAh battery that is expected to give talk time of up to 7 hours and standby time of 300 hours. Meanwhile, the Samsung Epic Touch 4G has Li-Ion 1800 mAh battery support, which will offer more than 10 hours of talk time; the AT&T versions retain the Li-Ion 1650 mAh battery found in the original Galaxy S2. The T-Mobile variant has Li-Ion 1850 mAh battery support.

Pricing: The Galaxy S2 is priced at $199.99 with a two-year contract both on Sprint and AT&T, while the T-Mobile variant is priced at $229.99. The pricing details of the Lumia 900 are unknown.