LTE TDD Mode
With full coverage in the 3GPP Release 8 specifications of both TDD and FDD modes of operation, LTE can effectively be deployed in both the paired and the unpaired spectrums. LTE TDD and FDD modes have been greatly harmonized in the sense that both modes share the same underlying framework, including radio access schemes, OFDMA in downlink and SC-FDMA in uplink, basic sub-frame formats, and configuration protocols. As a clear indication of harmonization, the TDD mode is included together with the FDD mode in the same set of specifications, including the physical layer [1–4] where there are just a few differences due to the uplink/downlink switching operation. In terms of architecture there are no differences between FDD and TDD and the very few differences in the MAC and higher layer protocols relate to TDD-specific physical layer parameters. Procedures remain the same. Thus there will be high implementation synergies between the two modes allowing for efficient support of both TDD and FDD in the same network or user device. Coexistence would, of course, still require careful analysis.
Another key feature of the LTE TDD mode (also known as TD-LTE) is the commonality with TD-SCDMA . This is an advantage, for example, in China, where the Release 4 based TD-SCDMA (including enhancements from later Releases) has opened for a large-scale TDD system deployment, making ...