Cross Link Interference Measurement in TDD Networks
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Solution Overview
Problem
Dynamic Time Division Duplexing (TDD) networks face challenges in meeting stringent latency and reliability performance due to exclusive availability of either downlink or uplink transmission at a time, leading to cross-link interference (CLI) issues.
Innovation Solution
A method is presented where a second node in a second radio access network (RAN) requests cross-link interference measurement parameter information from a first node in a first RAN, allowing for the measurement and reporting of CLI, thereby facilitating dynamic adaptation of network resources to mitigate CLI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If full duplexing is implemented to eliminate buffering delays and improve latency performance, then latency is reduced, but cross-link interference (CLI) occurs due to neighboring RAN nodes transmitting in opposite directions simultaneously
Solution Approach 1:
The patent implements a feedback mechanism where the victim RAN node measures CLI from the aggressor RAN node and reports the measurement results back through the backhaul interface. This feedback loop enables the network to identify and mitigate CLI issues, allowing full duplex operation to proceed with controlled interference levels.
Solution Approach 2:
The patent introduces an intermediary measurement and reporting mechanism between the aggressor and victim RAN nodes. The victim node acts as an intermediary that quantifies the interference and communicates it back to the aggressor, enabling coordinated resource allocation and CLI mitigation strategies.
2Productivity
If dynamic TDD is used to adapt network resources to asymmetric downlink and uplink traffic, then resource utilization and capacity are improved, but latency and reliability performance deteriorate due to exclusive availability of single transmission direction
Solution Approach 1:
The patent enables dynamic TDD operation by allowing RAN nodes to independently select their transmission direction (uplink or downlink) based on traffic demands. This dynamic adaptability is combined with CLI measurement and reporting mechanisms that allow the system to adjust to changing interference conditions while maintaining high resource utilization.
Solution Approach 2:
The patent changes the operational parameters of TDD by introducing full duplex capability where nodes can simultaneously transmit and receive on different sub-bands. This parameter change allows the system to meet asymmetric traffic demands while maintaining low latency through simultaneous bidirectional communication.
3Reliability
If downlink transmission power is increased to improve downlink coverage and performance, then downlink reliability is improved, but uplink transmission to adjacent RAN nodes is severely impacted due to higher interference power
Solution Approach 1:
The patent applies local quality by allowing different RAN nodes to operate with different transmission powers and directions based on local conditions. The aggressor node can maintain high downlink power for its own coverage area while the victim node experiences controlled interference, and the system compensates through CLI measurement and coordinated resource allocation.
Solution Approach 2:
The patent segments the frequency spectrum into different sub-bands for downlink and uplink transmissions. This segmentation allows the aggressor node to transmit downlink on one sub-band while the victim node receives uplink on another sub-band, reducing interference through frequency separation while maintaining high transmission powers.
Data Source
AI summary
A victim RAN node subject to cross-link interference (“CLI”) from a neighboring aggressor RAN node requests a CLI measurement procedure with the aggressor. The CLI measurement request may include indication of time-unit and frequency resources, and uplink and downlink beam combinations, corresponding to the victim and aggressor, respectively, to be used during the measuring procedure. Upon acknowledgement by the aggressor to participate in measuring CLI according to resource information indicated in the request, the victim may mute ongoing receiving or transmitting of signals using the time, frequency, and beam-combination resources indicated in the request and measure CLI received from the aggressor during the time, at the frequencies, and via the beam-combinations indicated in the request. The victim RAN may compile a CLI measurement report and transmit the report to the aggressor. The request, acknowledgement, and report may be transmitted via backhaul links.