hat most GSM cellular providers use. WCDMA is also known as the Universal Mobile Tele- communications System (UMTS). Time Division-Synchronous CDMA (TD-SCDMA) This is a standard supported by the Chinese government, which underwrote research and development by Chinese manufacturers. Thus, manufacturers do not have to pay royalties to license these 3G technologies. The government has left it up to operators to choose their own 3G technology. It has made spectrum available for the three main 3G standards. China Mobile has implemented TD-SCDMA, but China Unicom settled on WCDMA and China Telecom on CDMA2000. CDMA2000 This is the standard used by most CDMA providers and some providers in newly developing countries. Verizon Wireless and Sprint Nextel use CDMA2000. CDMA2000 was the first IMT-2000 standard deployed commercially. SK Telecom implemented it in South Korea in October 2000. The Transition to WCDMA Most GSM operators implemented General Packet Radio Service (GPRS) before WCDMA. WCDMA supports higher data rates and has more capacity for voice. Installing both GPRS and Enhanced Data Rates for Global Evolution (EDGE) delayed the large expenses of upgrading to WCDMA. Unlike 3G, GPRS and EDGE operate on the same frequencies as GSM, and thus upgrades are less costly. GPRS has a 64Kbps peak data rate with an achievable rate of about 30Kbps. This is about equivalent to dial-up data modems on landline networks. A disadvantage of GPRS is that packet data takes capacity from voice in GSM networks and dedicates it to data. Mobile and Wi-Fi Networks The Benefits of EDGE over GPRS EDGE, as implemented, is a 2.5G interim technology in the evolution to 3G networks. Although there is a 3G standard for it, it has never been implemented. EDGE supports more capacity for data than GPRS. The average data throughput is between 60Kbps and 120Kbps, depending on network conditions. It also uses network capacity more efficiently than GPRS because it dynamically assigns voice and data to channels as they become available instead of dedic