Technology requirements of the 3GPP-TDD terminal

This paper examines the technology requirements for the implementation of the 3GPP-TDD mode and discusses how the terminal complexity of the TDD mode compares to that of the FDD mode. An overview of the TDD mode covers the frequency bands, the synchronous nature, and the physical channel structure. The differences in the inner receiver implementation between the TDD mode and the FDD mode are highlighted. The paper identifies the key complexity issues that determine the TDD terminal architecture. It explains the requirement for terminal synchronisation to the network in the synchronous TDD mode and asynchronous FDD mode. The description of the baseband implementation covers the inner receiver functions of the TDD mode: channel estimation, active code detection and multi-user detection. The latter is basically examined from the joint detection point of view, nevertheless other techniques are presented with particular interest in the single detection algorithms. This leads to a comparison of the terminal architectures for the FDD and TDD modes, in particular the suitability of the air interface to flexible implementation on a DSP.