Subband Full Duplex Timing Alignment for Inter-UE Cross-Link Interference
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Solution Overview
Problem
In Subband Full Duplex (SBFD) cellular systems, inter-UE cross-link interference (CLI) and self-interference (SI) occur due to the proximity of uplink and downlink transmission sub-bands, causing significant interference issues that existing mitigation techniques are unable to fully address.
Innovation Solution
A method and apparatus for enabling a Subband Full Duplex (SBFD) timing alignment (TA) mechanism, where UEs receive a timing adjustment command including propagation delay from the base station, and apply a timing alignment delay of 2×(c−δi) for UL transmissions in SBFD slots, or a timing advancement for uplink-only slots, to synchronize UL transmissions with respect to DL receptions, thereby reducing inter-UE CLI and SI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uplink and downlink transmission sub-bands are placed in proximity for SBFD operation, then spectrum efficiency is improved, but inter-UE cross-link interference and self-interference increase
Solution Approach 1:
The base station performs preliminary timing alignment by calculating the propagation delay δi for each UE and determining the timing alignment delay 2×(c−δi) before UL transmission occurs. This preliminary timing adjustment ensures that UL transmissions from different UEs arrive at the base station synchronized with DL receptions, preventing inter-UE CLI before it can occur.
2Object-affected harmful factors
If timing alignment delay 2×(c−δi) is applied to UL transmissions in SBFD slots, then UL transmissions are synchronized with DL receptions reducing inter-UE CLI, but transmission timing complexity increases
Solution Approach 1:
Each UE independently calculates its own timing alignment delay using the formula 2×(c−δi), where c is a constant and δi is the propagation delay specific to that UE. The base station provides only the propagation delay parameter δi to each UE, and the UE autonomously applies the appropriate timing adjustment to its UL transmissions, eliminating the need for complex centralized timing control.
3Measurement precision
If propagation delay compensation is implemented for each UE, then timing synchronization accuracy is improved, but signaling overhead increases
Solution Approach 1:
The base station changes the parameter δi (propagation delay) specifically for each UE based on its distance from the base station. By adjusting this single parameter δi and providing it to each UE, the system achieves precise timing synchronization for all UEs without requiring complex multi-parameter signaling, as each UE uses δi to calculate its unique timing alignment delay.
Data Source
AI summary
In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The method may be performed by a UE. In certain configurations, the UE receives, from a base station, a configuration instruction for enabling a subband full duplex (SBFD) timing alignment (TA) mechanism and a constant c. The UE enables the SBFD TA mechanism according to the configuration instruction. The UE receives, from the base station, a timing adjustment command, which includes a propagation delay δi for the UE. The UE determines whether an uplink (UL) transmission is to be performed in a SBFD slot. In response to determining the UL transmission to be performed in the SBFD slot, the UE applies a timing alignment delay to the UL transmission with respect to the SBFD slot start boundary. The timing alignment delay is determined by both the constant c and the propagation delay δi.