Full Duplex TDD Operation with Adaptive HARQ Feedback Timing
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Solution Overview
Problem
Conventional communication systems face challenges in achieving full-duplex operation in time division duplex (TDD) systems due to the need for simultaneous transmission and reception of radio frequency signals, which is not supported by existing frequency or time separation methods.
Innovation Solution
A wireless transmit/receive unit (WTRU) is configured to receive indications of different TDD uplink/downlink configurations and applies hybrid automatic repeat request (HARQ) process timing for DL HARQ feedback, monitoring subframes for grants and transmitting feedback via a Physical UL Control Channel (PUCCH), while configuring FD radio subframes from corresponding subframes of multiple TDD configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency separation is used to separate Tx and Rx signals, then signal separation is achieved, but spectrum efficiency is reduced due to required spacing between UL and DL channels
Solution Approach 1:
The patent transitions from frequency-domain separation (FDD) to time-domain separation (TDD), utilizing temporal dimension to separate transmit and receive signals. This allows channels to be adjacent in frequency while maintaining separation through time switching, thereby improving spectrum efficiency while preserving signal separation reliability.
Solution Approach 2:
The patent implements dynamic TDD configuration where the uplink-downlink configuration can be changed dynamically. The eNodeB can switch between different TDD configurations (e.g., configuration 1 with more downlink subframes, configuration 5 with more uplink subframes) to adapt to varying traffic conditions, optimizing spectrum utilization while maintaining reliable signal separation through controlled switching periods.
2Productivity
If time separation is used to separate Tx and Rx signals, then full duplex operation is enabled, but HARQ feedback timing becomes complex when multiple TDD configurations are involved
Solution Approach 1:
The patent segments HARQ feedback timing into different sets based on the TDD configuration. Each TDD configuration (e.g., configuration 1 and configuration 5) has its own associated HARQ feedback timing set. The WTRU maintains multiple HARQ process sets, each linked to a specific TDD configuration, thereby managing complexity through systematic segmentation rather than unified handling.
Solution Approach 2:
The patent implements feedback mechanisms where the WTRU reports its configured TDD configuration to the eNodeB, and the eNodeB adjusts scheduling decisions accordingly. The WTRU also provides feedback on HARQ status for different configuration sets, enabling the system to adapt feedback timing dynamically while maintaining manageable complexity through structured feedback protocols.
3Adaptability or versatility
If multiple TDD UL/DL configurations are supported, then flexibility and adaptability are improved, but compatibility with legacy WTRUs is challenging
Solution Approach 1:
The patent implements universality by allowing the eNodeB to support multiple TDD configurations simultaneously while maintaining backward compatibility. Legacy WTRUs continue to operate with their original configured TDD settings, while newer WTRUs can utilize enhanced configurations. The system provides multi-functional capability to handle both legacy and advanced configurations through a unified control framework, ensuring compatibility without sacrificing flexibility.
Solution Approach 2:
The patent employs dynamic configuration where the eNodeB can adaptively select between different TDD configurations based on the capabilities of connected WTRUs. The system dynamically adjusts the active configuration set, allowing flexible deployment of multiple configurations while maintaining compatibility. Legacy WTRUs are served through established configurations, while new configurations are activated only when capable devices are present, ensuring smooth transition and broad compatibility.
Data Source
AI summary
A method and apparatus for providing for full-duplex (FD) operation in time division duplex (TDD) communications are disclosed herein. A wireless transmit/receive unit (WTRU) may receive an indication of a first, UL heavy, TDD uplink (UL)/downlink (DL) configuration and an indication of a second, DL heavy, TDD UL/DL configuration. The WTRU may also receive a grant in a common DL subframe. The WTRU may apply the hybrid automatic repeat request (HARQ) process timing associated with one of the TDD UL/DL configurations for DL HARQ feedback. Also, the WTRU may monitor a set of subframes for a UL or a DL grant. Further, the WTRU may receive a grant in a subframe which may include an indication of a reference TDD UL/DL configuration. The WTRU may then apply the HARQ process timing associated with the reference TDD UL/DL configuration for DL HARQ feedback.