Seven TDD UL/DL configurations have been supported in LTE TDD since Rel-8 to address different DL and UL traffic ratios. The most DL heavy TDD UL/DL configuration in current LTE TDD is configuration 5, where 8 DL subframes and one DwPTS in a special subframe within a radio frame (i.e. 10 subframes) can be used for DL transmission. There has been a proposal to introduce additional configuration into LTE TDD, aiming to provide even more resources for DL transmission. There has not been any consensus on whether additional TDD configuration shall be introduced for LTE TDD. To gain a better understanding on the issues related to the potential introduction of additional configuration for LTE TDD, this study item is proposed. This study item shall not provide any recommendation on any follow-up normative work. Upon completion of this study item, the follow-up actions shall be discussed on the PCG level. TDD operation in unlicensed spectrum is out of the scope of this study.

The objective of the study is to evaluate issues related to the potential introduction of the following additional configuration(s) for LTE TDD; 10:0:0 and 9:1:0 (DL:Sp:UL). This includes:

• Identify the scenario(s), frequency band(s), and use cases(s) of the possible additional TDD configuration(s)
• Coexistence with adjacent standalone LTE TDD operations in the same band
  • To be compared with the coexistence between intra-band adjacent LTE TDD operations using different UL/DL configurations
• Evaluation of the potential benefits and drawbacks of the additional TDD configuration(s) and possible solutions to mitigate the potential drawbacks
• Any other relevant ecosystem aspect(s)
• Compare the option of using 10:0:0 and/or 9:1:0 TDD configuration for a TDD spectrum against the alternative of converting the TDD spectrum to FDD supplemental DL spectrum