Where can I find some info about GSM SMS system?

Sony Ericsson P990 is a smartphone and the successor of Sony Ericsson P910. The phone uses the UIQ 3 software platform, which is based upon Symbian OS 9.1. It was released in August 2006. The P990 has a numeric keypad that flips open to reveal a full qwerty keyboard below the display, on the phone itself. This is a change from P910 where the keyboard is on the flip. The keyboard itself can be attached or detached using the screw and screwdriver found in the box. The phone is a UMTS (3G) and tri-band GSM phone supporting video calls through its front VGA camera. The touchscreen displays 262,521 colours (18-bit colour depth) with a resolution of 240x320 pixels. It also comes with a 2.0 Megapixel camera featuring autofocus and an FM/RDS radio. The P990 runs a version of an ARM9 208 MHz processor from Philips.The screen despite a smaller length (2.8 inch) than its predecessors is actually larger in area because of the increased width. The phone also improves over the P910 by including support for Wi-Fi, allowing users to connect to 802.11b wireless networks, which will be popular with the professional user.