Mitigating Cross-Link Interference in Millimeter Wave Dynamic TDD
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Solution Overview
Problem
In 5G NR wireless communication systems, dynamic time division duplexing (TDD) leads to cross-link interference (CLI) between user equipment (UEs) operating across millimeter wave bands, where UEs transmitting on an uplink channel may interfere with neighboring UEs receiving on a downlink channel, compromising communication flexibility.
Innovation Solution
UEs and base stations coordinate communication parameters such as beam directions and slot formats to minimize CLI by selecting non-overlapping beam directions or coordinated slot formats, ensuring that one UE does not transmit while the other receives during overlapping periods, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic time division duplexing is used to allow flexible transmission modes, then communication flexibility is improved, but cross-link interference between user equipment increases
Solution Approach 1:
The base station determines candidate values for communication parameters before actual transmission occurs, and provides these candidate values to the user equipment in advance. This preliminary coordination allows UEs to select parameters that avoid interference without real-time negotiation, resolving the contradiction between flexibility and interference by pre-planning parameter selections.
Solution Approach 2:
The base station acts as an intermediary that collects communication parameter information from one UE, determines compatible candidate values, and provides them to another UE. This intermediary coordination mechanism enables flexible parameter selection while preventing cross-link interference through centralized management of parameter compatibility.
2Productivity
If UEs transmit on uplink channels simultaneously, then uplink communication capacity is improved, but interference with neighboring UEs receiving on downlink channels increases
Solution Approach 1:
The system applies different communication parameters (beam directions, slot formats) to different UEs locally. By determining candidate values based on specific UE configurations and providing UE-specific parameter recommendations, the system enables each UE to transmit or receive with optimized local parameters that avoid causing or suffering from interference, thus maintaining high uplink capacity while protecting downlink reception quality.
Solution Approach 2:
The base station determines candidate values for communication parameters such as beam directions and slot formats based on the first UE's parameters, then provides these to the second UE. This parameter coordination ensures that when one UE transmits on uplink, the other UE uses coordinated parameters (different beam directions or slot formats) to avoid interference during downlink reception, resolving the capacity-interference tradeoff.
Data Source
AI summary
Dynamic time division duplex (TDD) is a flexible transmission technique allowing different user equipments (UEs) to operate in a downlink mode or an uplink mode depending on the instantaneous traffic load. As a result, a UE transmitting on an uplink channel may interfere with a neighboring UE receiving on a downlink channel. UEs may coordinate communication parameters to reduce cross-link interference. A UE may determine a preferred value(s) for a first communication parameter comprising a beam direction or a slot format index (SFI). The UE receives a candidate value(s) for the first communication parameter, the candidate value(s) being based on communications between a second UE and a first base station. The UE selects a first value among the preferred values based on the received candidate value(s); and initiates communications with a second base station using the first value for the first communication parameter.