annel as it is sent. Use of this technology gives CDMA more capacity than GSM. The United States-based technology company, Qualcomm, pio- neered CDMA in the commercial sector. CDMA supports more phone calls and data sessions per cell than any other 2G air interface. The decision to use this superior multiplexing method cost many carriers in the United States a high price in lost compatibility to GSM. However, CDMA enabled them to offer voice and data services at a lower cost and to more easily upgrade their networks to 3G networks. In the United States, Verizon Wireless and Sprint Nextel use CDMA technology. Carriers in other countries including China, Japan, and South Korea adopted it as their 2G service. Once Europe settled on a uniform air interface, most of the rest of the world followed suit and adopted GSM for compatibility while roaming. Compatibility throughout Europe; a Mix of Standards in the United States When analog cellular was developed in the United States, one organization, AT&T, set de facto standards for all telecommunications services. However, in 1984, AT&T was required to divest itself of the local telephone companies. When these local carriers in the United States upgraded to digital services during the 1990s, they were no longer part of AT&T and were free to select different standards. Also, new cellular companies that purchased spectrum at a government auction chose various air interfaces. Initially, all but the former AT&T local carriers chose CDMA because of its superior capacity. Qualcomm, the developer of CDMA, was late in delivering CDMA software due to its complexity. Because of this, Southwestern Bell Mobility (now AT&T) initially commercialized Time-Division Multiple Access (TDMA). As the former Southwest- ern Bell Mobility purchased other telephone companies, it converted them to TDMA, as well. Starting in 2003, AT&T Mobility converted its entire TDMA network to GSM to align with carriers worldwide. AT&T Mobility upgraded its 2G network to Wideband Code-Division Multiple Access (W