ht member companies: China Mobile, China Telecom, China Unicom, Datang, Hua- wei, Motorola, Nortel, and Siemens. TD-SCDMA is primarily aimed at the main- land Chinese market, in support of voice services. TD-SCDMA uses TDD, which significantly improves network performance by processing traffic in both the uplink and downlink directions. It transmits uplink traffic and downlink traffic in the same frame in different time slots. Uplink and downlink resources are assigned according to individual user needs. The S (for Synchronous) in its name signifies that TD-SCDMA can master both synchronous circuit-switched services (such as speech or video services) and asynchronous packet-switched services (such as Internet access). Data rates can range from 1.2Kbps to 2Mbps. In addition, TD-SCDMA improves performance by using the CDMA encoding transmission mode, supporting improved and highly efficient capacity and spectrum usage. TD-SCDMA covers all application scenarios, being designed to address all cell sizes: metropolitan city centers, indoor and campus environments, hotspots, and rural areas. Because TD-SCDMA is based on TDD and uses unpaired frequency bands, it offers optimum efficiency for both symmetric and asymmetric data ser- vices. Due to its small bandwidth of 1.6MHz, this technology allows flexible spec- trum allocation, depending on the type of information being transmitted. When asymmetrical data such as e-mail and Internet information are transmitted from the base station, more time slots are used for the downlink than for the uplink. A symmetrical split in the uplink and downlink takes place with symmetrical ser- vices such as telephony. Finally, seamless handoff between TD-SCDMA and GSM guarantees that no call is lost while the user is moving. The main characteristics of TD-SCDMA are that it operates in the frequency band 2,010MHz to 2,025MHz in China (with wireless local loop applications in the 1,900MHz to 1,920MHz band) using the TDD mode. TD-SCDMA can operate in a minimum frequency band of 1.6MHz at 2Mbp