1xRTT 
single-carrier radio transmission technology 
1xRTT, sometimes referred to as CDMA2000 1x, is the first phase in CDMA's evolution to third-generation (3G) technology. For voice transmission, 1xRTT networks allow for greater network capacity (more users; fewer dropped calls) and, in theory, better battery life for phones. On the data side, carriers plan to initially offer always-on connections at speeds of up to 144Kbps and ratchet up to broadband speeds in phase two of 3G deployment, referred to as 3xRTT, by 2003.