Scheduling Weights for Cross-Link Interference Mitigation in TDD Networks

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Solution Overview

Problem

Existing solutions for mitigating Cross-Link Interference (CLI) in Time Division Duplexing (TDD) cellular networks incur significant signaling overhead and are not efficient, as they often require resource wastage and complex signaling between base stations to avoid inter-cell interference.

Innovation Solution

A method is introduced where Radio Access Network (RAN) nodes perform a baseline scheduling procedure, modifying scheduling weights for wireless communication devices based on CLI impact, specifically avoiding scheduling of devices affected by CLI in downlink slots preceding uplink slots, thereby reducing overhead and targeting precise interference mitigation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If gap symbols are increased to protect against uplink-to-downlink CLI, then interference mitigation is improved, but system resources are wasted and productivity deteriorates

Engineering Contradiction:

ImproveCLI interferenceVSAvoidsystem resource utilization

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The base station performs preliminary identification of cell edge UEs that are likely to cause CLI before scheduling decisions are made. By pre-characterizing these UEs based on their location and transmission patterns, the system can proactively adjust scheduling weights to prevent CLI rather than reacting to it after occurrence, thereby avoiding the need for excessive gap symbols.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention applies differentiated scheduling weights specifically to cell edge UEs that are prone to causing CLI, rather than uniformly reducing resources across the entire cell. This localized approach targets only the specific UEs and time slots where CLI is likely to occur, preserving system resources for other UEs and time slots where interference is not an issue.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If neighbor base stations share scheduling information to avoid CLI, then interference mitigation is improved, but signaling overhead increases

Engineering Contradiction:

Improveinter-cell interferenceVSAvoidsignaling overhead

Core Design Contradiction:

Object-affected harmful factorsVSLoss of information

Solution Approach 1:

Each base station independently identifies its own cell edge UEs that may cause CLI and autonomously adjusts scheduling weights for these UEs. The base station uses local knowledge of UE locations, path losses, and timing advance values to make scheduling decisions without requiring extensive information exchange with neighboring base stations, thereby eliminating the need for complex inter-base-station signaling.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention segments the scheduling decision-making process into independent base station operations, where each base station handles its own CLI mitigation locally. This segmentation eliminates the need for centralized coordination or extensive information sharing between base stations, reducing signaling overhead while maintaining effective CLI mitigation.

Inventive Principle:

Principle #1Segmentation

3Productivity

If high-powered UEs are scheduled in downlink slots preceding uplink slots, then system throughput is improved, but severe CLI is caused to neighboring cells

Engineering Contradiction:

Improvesystem throughputVSAvoiduplink interference to downlink

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The scheduling weight for each UE is dynamically adjusted based on real-time conditions including whether the current slot is a downlink slot preceding an uplink slot, the UE's cell edge location, and its transmission power level. This dynamic adjustment allows the system to flexibly manage throughput and interference trade-offs on a per-slot, per-UE basis rather than using static resource allocation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the scheduling weight parameter for cell edge UEs in specific time slots (downlink slots preceding uplink slots) to prevent CLI. By modifying this key scheduling parameter based on slot type and UE characteristics, the system can control uplink transmission power levels indirectly, reducing interference to neighboring cells while maintaining overall system throughput through alternative scheduling decisions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240237047A1Scheduling cell edge users to avoid cross link interference

Publication Date: 2024.07.11 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Systems and methods for avoiding or mitigating cross-link interference in a Time Division Duplexing (TDD) network are disclosed. In one embodiment, a method performed by a Radio Access Network (RAN) node comprises performing a baseline scheduling procedure for wireless communication devices for a slot, wherein the wireless communication devices are assigned first scheduling weights that correspond to priorities of the wireless communication devices for scheduling during the slot. The method further comprises determining that the slot is a downlink slot that is preceding an uplink slot and, responsive thereto, modifying the first scheduling weights based on whether the wireless communication devices are affected by cross-link interference to thereby provide second scheduling weights for the wireless communication devices for the slot. The method further comprises scheduling the wireless communication devices for the slot in accordance with the second scheduling weights.