TD-SCDMA evolution

This article focuses on the evolutional strategies (which can be divided into four phases) from the current commercial time division-synchronous code division multiple access (TD-SCDMA) to the future International Mobile Telecommunications (IMT)-Advanced systems. The first evolutional phase is to develop an N-frequency technology to improve capacity and ease network planning of the current TD-SCDMA system. Single- and multicarrier high-speed packet access (HSPA) is specified in the second phase for providing high-rate packet services. Long-term evolution (LTE) technology is introduced in the third phase to provide a similar performance of mobile worldwide interoperability for microwave access (WiMAX). Finally, the fourth phase is to implement time division duplex (TDD)-based IMT-Advanced system, which is one of the alternative standards beyond third-generation (3G) systems. The advanced technologies to enhance spectral efficiency are the critical issues emphasized in all the four phases. The challenges and open issues in the different evolutional phases are identified in this article as well.