TDD-CDMA Technology for Cellular and Ad Hoc Systems
Outline of tutorial:
This tutorial will provide an in-depth analysis of the Time Division Duplex (TDD) mode of CDMA (Code Division Multiple Access) communications as it applies to the 3rd and 4th generation of mobile communications systems. It deals with both TD-CDMA, or UTRA-TDD (UMTS Terrestrial Radio Access), and TD-SCDMA standards and discusses the associated public and ad-hoc network topologies for next generation systems. The tutorial provides a detailed state of the art analysis, including the implementation and rollout issues, and how the TD-CDMA business and technology is developing.
Although considered a complimentary technology to the Frequency Division Duplex (FDD) mode in the 3G standards, TDD systems are emerging as equal, if not the dominant, mode of the future mobile communication services (including 3G services). They are the front-runner to become the major duplex technology in 4G systems as flexible operation, asymmetric capacity requirements of 4G services, as well as unpaired frequency allocation and the lack of a guard radio frequency band gives them a significant advantage over the FDD mode – especially for asymmetric high data rate transmission. In addition to these advantages, the channel reciprocity characteristic of TDD transmission facilitates specific techniques, which enable TDD systems to transmit at higher rates and support higher system capacity. In addition, new communication modes such as ad hoc, relaying or multi-hop will play a significant role in future wireless communications due to the significantly reduced coverage for high data-rate transmissions. It will be demonstrated the TDD technology is the most appropriate duplexing method to enable the new communications modes.
The disadvantages of the TDD mode such as the need for synchronisation will also be discussed and solutions will be provided.