What is Automatic Modulation and Coding (AMC)

As the basic 3G choice in China, TD-SCDMA has been widely accepted and adopted. The performance of China Communication Standard Association (CCSA) N-frequency TD-SCDMA DCH (Dedicated Channel) -based services has been well testified in both the trial and real networks. It is no question that DCH-based TD-SCDMA is able to provide both voice service and some packet services. Nowadays, for the ever-increasing demand on the multimedia services, the evolution of TD-SCDMA networks has become a hot issue. Single carrier TDSCDMA HSDPA (TD-HSDPA for short) was introduced in 3GPP in the R5 version as the downlink evolution of TD-SCDMA networks. Multi-carrier TD-HSDPA, introduced by CCSA, is the enhancement version of the 3GPP single carrier TD-HSDPA, which adopts the multi-carrier to improve the system performance. It offers backward-compatible upgrades to both former N-frequency TD-SCDMA networks and single carrier TD-HSDPA systems. In 2006, 3GPP made its effort to standardize the uplink evolution of TD-SCDMA networks. Released by 3GPP R6 version, TD-SCDMA HSUPA (TD-HSUPA for short) is believed to be able to enhance the system uplink capacity significantly. In order to offer the backward-compatible upgrade to both the N-frequency TD-SCDMA and multi-carrier TD-HSDPA, CCSA started the standardization work of multi-carrier TD-HSUPA in August, 2007. Armed with both the downlink and the uplink evolution, TD-SCDMA is believed to be able to provide various multimedia services. This article aims at introducing key concepts of the evolution of TDSCDMA networks, including system architecture, key techniques, protocols, and channels. The article begins with the introduction of the basic characters of TD-SCDMA. Then, the downlink evolution of TDSCDMA networks is presented. After that, we present the uplink evolution of TD-SCDMA networks. Key principles of TD-SCDMA Long-Term Evolution (LTE TDD) are discussed at the end of the article.