Non-Proportional TBS Scaling for URLLC Reliability
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Solution Overview
Problem
Current wireless communication systems face challenges in meeting ultra-reliable low-latency communication (URLLC) requirements, particularly in reducing coding rates to achieve high reliability without increasing processing latency, as the minimum achievable coding rate is constant across transmission time intervals (TTIs) due to proportional transport block size (TBS) scaling factors.
Innovation Solution
Dynamic indication of non-proportional TBS scaling factors, such as 1/12 for shortened TTIs, allows for lower coding rates by explicitly or implicitly transmitting TBS scaling factors through radio resource control signaling or repetition modes, enabling improved reliability without affecting processing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If proportional TBS scaling factors are used across different TTI lengths, then the system maintains consistent coding rate relationships, but the minimum achievable coding rate remains constant and cannot be reduced to meet URLLC reliability requirements
Solution Approach 1:
The patent introduces non-proportional TBS scaling factors that break the traditional proportional relationship between TTI length and TBS scaling. By allowing different scaling factors (e.g., 1/4, 1/6, 1/12) that are not strictly proportional to TTI length reductions, the system can achieve lower coding rates for shortened TTIs, thereby meeting URLLC reliability requirements while maintaining adaptability across different TTI configurations
Solution Approach 2:
The patent enables dynamic selection of TBS scaling factors based on the specific TTI length and URLLC requirements. The base station can dynamically indicate appropriate scaling factors to UEs, allowing the coding rate to be adaptively reduced for shorter TTIs without being constrained by fixed proportional relationships, thus achieving both reliability improvement and system adaptability
2Reliability
If the coding rate is reduced to meet reliability requirements, then the transmission reliability improves, but the processing latency increases
Solution Approach 1:
By introducing non-proportional TBS scaling factors, the patent enables more aggressive TBS reduction for shortened TTIs compared to traditional proportional scaling. This allows achieving lower coding rates (e.g., 1/12 scaling for subslot TTIs) without proportionally increasing processing time, as the scaling is decoupled from strict TTI length proportionality, thus improving reliability while controlling latency
Solution Approach 2:
The base station pre-configures and indicates appropriate TBS scaling factors to UEs before transmission occurs. This preliminary indication allows UEs to prepare the correct TBS and coding rate in advance, avoiding latency penalties during actual transmission. The scaling factors are determined beforehand based on TTI length and URLLC requirements, enabling fast execution without real-time calculation delays
3Reliability
If non-proportional TBS scaling factors are used, then lower coding rates and improved reliability are achieved, but the system complexity increases due to multiple scaling factor configurations
Solution Approach 1:
The patent uses dynamic indication mechanisms where the base station signals the appropriate TBS scaling factor to UEs based on current transmission conditions and TTI length. This dynamic approach allows the system to use simple proportional scaling for non-URLLC traffic while switching to complex non-proportional scaling only when URLLC requirements are present, thereby achieving high reliability when needed while minimizing average system complexity
Solution Approach 2:
The patent applies different TBS scaling factor rules to different traffic types and TTI lengths. Non-proportional scaling factors are applied locally only to URLLC transmissions with shortened TTIs, while traditional proportional scaling continues to apply to other traffic. This localized application of complexity ensures that the increased device complexity is confined only to where it provides value for URLLC reliability, rather than affecting the entire system uniformly
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. Some wireless communications systems may implement reliability thresholds for transmissions. Base stations and user equipment (UEs) may implement techniques to reduce coding rates in order to improve reliability. For example, a base station may dynamically indicate a UE-specific transport block size (TBS) scaling factor for communication. The base station may include an explicit TBS scaling factor indicator in a downlink transmission, an implicit indication of the TBS scaling factor based on an indicated mode of operation (for example, a repetition mode) for the UE, or a combination thereof. By dynamically selecting between different supported scaling factors, the wireless devices may implement TBS scaling factors that are non-proportional to resource scaling factors, resulting in lower coding rates. For example, the wireless devices may utilize lower scaling factors for repetition-based transmissions than single transmissions to improve the reliability of the repeated transmissions.