Grant-Free Uplink Configuration for URLLC Latency
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Solution Overview
Problem
Current wireless communication systems, particularly in 4G and 5G networks, face challenges in efficiently managing multi-carrier communication and resource allocation for ultra-reliable low-latency communications (URLLC), leading to suboptimal performance in terms of latency and reliability.
Innovation Solution
The implementation of grant-free uplink transmission mechanisms, where radio resources are configured without dynamic grants, allowing multiple UEs to share the same radio resources, and the use of UE-specific demodulation reference signals to avoid collisions, along with a preamble-based transmission procedure for reliable UE identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic grants are used for uplink transmission, then resource allocation reliability is improved, but signaling overhead increases and latency increases
Solution Approach 1:
The base station pre-configures uplink radio resources for multiple UEs before actual data transmission is needed. This preliminary configuration includes allocating specific time-frequency resources and associated demodulation reference signals to each UE, so that when URLLC data arrives, the UE can immediately transmit without waiting for dynamic grant signaling.
Solution Approach 2:
The patent extracts the resource allocation decision from the dynamic grant signaling process and embeds it directly into the downlink data transmission. By including resource allocation information in the downlink assignment, the system eliminates the need for separate uplink grant signaling, thereby reducing signaling overhead and latency while maintaining reliable resource allocation.
2Productivity
If multiple UEs share the same radio resources, then resource utilization efficiency is improved, but collision probability increases
Solution Approach 1:
Each UE is assigned unique UE-specific demodulation reference signals with distinct parameters (such as different cyclic shifts or orthogonal cover codes) even when sharing the same physical radio resources. This local differentiation in signal characteristics allows the base station to distinguish between multiple UEs' transmissions and perform separate channel estimates, thereby avoiding collisions and maintaining transmission reliability while enabling efficient resource sharing.
3Loss of time
If grant-free transmission is implemented, then signaling overhead is reduced, but resource allocation flexibility decreases
Solution Approach 1:
The base station performs preliminary resource configuration for multiple UEs based on historical traffic patterns and QoS requirements. This pre-allocation enables grant-free transmission by having UEs directly use pre-assigned resources without dynamic grants, reducing signaling overhead. The preliminary configuration includes setting up UE-specific reference signals and resource mappings that can be activated or deactivated as needed.
Solution Approach 2:
The system maintains flexibility by allowing the base station to dynamically adjust and reconfigure grant-free resources based on changing traffic conditions. The pre-configured resources can be modified, reallocated, or deactivated through subsequent signaling, enabling the system to adapt to varying load conditions and service requirements while still benefiting from reduced signaling overhead in normal operation.
Data Source
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AI summary
A wireless device may receive a radio resource control message comprising first configuration parameter(s) of a configured periodic grant of a first type. The first configuration parameter(s) may indicate: a timing offset and a symbol number that identify a resource of an uplink grant of the configured periodic grant; a first periodicity of the configured periodic grant, the first periodicity indicating a time interval between two subsequent resources of the configured periodic grant; and one or more demodulation reference signal parameters of the configured periodic grant. The configured periodic grant may be activated in response to the radio resource control message. Symbol(s) of the resource of the uplink grant of the configured periodic grant may be determined based on the timing offset, the symbol number, and the first periodicity. Transport block(s) may be transmitted, via the resource, employing the demodulation reference signal parameter(s).