TDD Slot Format Configuration for CLI Mitigation
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Solution Overview
Problem
Current Time-Domain Duplex (TDD) systems face challenges in configuring uplink and downlink periods flexibly, leading to Cross Link Interference (CLI) between overlapping radio resources, which existing techniques fail to address effectively due to inconsistent definitions and reliance on outdated data.
Innovation Solution
Implementing a configurable TDD system with defined rules for allocating uplink and downlink resources, including a Slot Format Indication (SFI) for gNBs to agree on safe regions, allowing flexible configuration while minimizing CLI, by specifying the order and length of DL, UL, and guard periods, and enabling semi-static agreements between neighboring gNBs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible configuration of uplink and downlink periods is provided on a per-TRP basis, then adaptability to changing network demands is improved, but Cross Link Interference between overlapping radio resources occurs
Solution Approach 1:
The patent applies preliminary action by establishing semi-static agreements between neighboring gNBs in advance, defining safe regions for uplink and downlink transmissions before interference occurs. These agreements are configured ahead of time and remain valid across multiple slot formats, preventing CLI proactively rather than reacting to it after it occurs. The gNBs exchange information about their intended UL/DL configurations and pre-identify safe regions where transmissions will not cause interference to neighbors.
Solution Approach 2:
The patent uses the Xn interface as an intermediary mechanism between neighboring gNBs to exchange slot configuration information and safe region definitions. This intermediary communication channel allows gNBs to coordinate their TDD configurations without direct interference, sharing knowledge about upcoming UL/DL periods and identifying mutually safe transmission regions. The intermediary enables cooperative interference avoidance while maintaining independent operation of each gNB.
2Object-affected harmful factors
If measurements and status reports are used to identify safe regions, then CLI mitigation is achieved, but data aging and poor accuracy occur due to reliance on backwards-looking data
Solution Approach 1:
The patent replaces backwards-looking measurements with forward-looking preliminary configurations. Instead of measuring past interference patterns and inferring safe regions, the gNBs proactively declare intended safe regions based on their configured TDD patterns and exchange this information through the Xn interface. This preliminary action ensures safe region identification is based on known, intended configurations rather than outdated measurements, eliminating data aging issues.
3Object-affected harmful factors
If gNBs exchange slot configuration information via Xn interface, then CLI avoidance is improved, but communication overheads and latency are incurred
Solution Approach 1:
The patent reduces latency and overhead by performing the information exchange preliminarily, before the actual slot configurations are needed for transmission. The gNBs exchange their intended slot format configurations and safe region definitions in advance through the Xn interface, allowing each gNB to locally determine safe regions without real-time communication during active transmission. This preliminary exchange eliminates the need for continuous real-time coordination, significantly reducing ongoing overhead and latency.
Solution Approach 2:
The patent introduces dynamics by allowing the safe region configurations to be updated periodically or event-driven rather than being static. The semi-static agreements can be reconfigured when network conditions change, allowing the system to adapt dynamically while maintaining stability during normal operation. This dynamic approach balances the need for frequent updates with the overhead of communication, updating only when necessary.
Data Source
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AI summary
Methods and techniques for slot format configuration in a Time Domain Duplex system to allow flexible assignment of resources between uplink and downlink, while avoiding Cross Link Interference. As standard slot ordering is provided together with rules to limit modification of slot format between slots such than an estimate of safe regions can be made.