1xRTT, often abbreviated as 1x, is a designation referring to an operating mode of CDMA2000, a wireless technology used in CDMA cellular networks. The 1x stands for one times the number of 1.25MHz channels, while RTT stands for radio transmission technology. It is also called 3G1X, IMT-CDMA Multi-Carrier, or IS-2000.
CDMA stands for code division multiple access, and it is a mobile digital radio technology that transmits streams of bits. Unlike older cellular technology, all radios on the network can be active at the same time. CDMA was developed by a commercial company, Qualcomm.
CDMA2000 is a family of wireless standards that use CDMA technology to transmit voice, data, and signal information between cellular phones and cell sites. 1xRTT is the version of CDMA2000 that uses a pair of 1.25MHz radio channels. It supports peak data speeds of up to 144 kilobits per second (Kbps) and, since it offers high speed data services in addition to voice capability, this standard is technically part of the third generation (3G) of cellular systems. It is slower than other 3G systems, however, so it is sometimes classified as “2.5” generation, an unofficial term for technologies that are seen as falling somewhere between the second and third generation of wireless cellular systems.
This technology is seen as an improvement over previous CDMA technologies for a number of reasons. It provides up to double the voice capacity of 2G cellular systems. What makes it so much more efficient is that it uses a pilot signal — a frequency transmitted for control, equalization, and reference purposes — as well as more channels between fixed cell stations and mobile users. It also has media and link access protocols, allowing for greater use of data services than 2G systems.
There are other operating standards for CDMA2000, including 1x Evolution-Data Optimized, which is also known as 1xEV-DO or EVDO. EVDO is an improvement over 1xRTT because it has a higher data rate capability. Wireless carriers use it for streaming data and video services, which would not be possible on the other standard. Evolution-Data/Voice (EVDV) transfers data at similar speeds, but development has stalled since most wireless carriers began adopting EVDO.